Resin particle dispersion and aqueous ink composition for writing utensils containing same

Abstract

Provided is a resin particle dispersion which is excellent in terms of dispersion stability and efficiently exhibits a specific surfactant function even after storage in a low-temperature environment. Also provided is an aqueous ink composition for writing utensils, which contains the resin particle dispersion and has a sufficient wettability improving effect even in a low-temperature environment without destroying the dispersion stability of an aqueous ink. This aqueous ink composition for writing utensils achieves both a stable writing flow rate and quality of written lines (writing performance) at high levels.　A resin particle dispersion according to the present disclosure is characterized in that at least resin particles which each internally contain at least one surfactant component that is selected from the group A described below are dispersed in water. (Group A) an acetylene-based surfactant, a polyethylene glycol-based surfactant, and a silicone-based activator

Description

Resin particle dispersion and aqueous ink composition for writing implements containing the same

[0001] The present specification relates to a resin particle dispersion containing a surfactant, and an aqueous ink composition for a writing instrument containing the same.

[0002] Conventionally, aqueous ink compositions for writing instruments and the like have been improved in wettability by incorporating specific surfactants. For example, the following are known: 1) an aqueous ballpoint pen ink composition containing at least water, carbon black, and a surfactant, wherein the carbon black has an oil absorption of 101 g or more ( / 100 g), and the surfactant is one or more selected from the group consisting of a silicone surfactant, an acetylene glycol surfactant, a fluorine-containing surfactant, and a dialkyl sulfosuccinate, and an aqueous ballpoint pen using the same (see, for example, Patent Document 1); 2) an aqueous brush pen ink composition containing a colorant, a surfactant having an acetylene bond, a defoaming agent, and water (see, for example, Patent Document 2); and 3) a heat-erasable ink composition comprising a colorant formed by reacting a leuco dye with a color developer and a desensitizer dispersed in water, the colorant using a polyethylene glycol-type nonionic surfactant as the desensitizer (see, for example, Patent Document 3).

[0003] However, when these aqueous ink compositions directly contain an acetylene-based surfactant having an acetylene bond, a polyethylene glycol-based surfactant, a silicone-based surfactant, or the like, direct addition can frequently cause the dispersion system to become unstable or precipitates to form. Furthermore, depending on the liquid temperature of the ink, particularly in a low-temperature environment, the solubility decreases, making it difficult to obtain a sufficient surfactant effect after low-temperature storage, making it difficult to obtain a wettability improvement effect or a stable writing flow rate, and causing unevenness in the writing flow rate, which can also reduce the quality of the written lines (writing ability).

[0004] JP 2013-28789 A (claims, examples, etc.) JP 2021-123696 A (claims, examples, etc.) JP 9-165537 A (claims, examples, etc.)

[0005] The present disclosure has been made in view of the above-mentioned problems of the conventional art and seeks to solve them, and aims to provide a resin particle dispersion that has excellent dispersion stability even after storage in a low-temperature environment and that efficiently exhibits a predetermined surfactant action, and an aqueous ink composition for a writing instrument containing the resin particle dispersion that has improved wettability and achieves a high degree of balance between a stable writing flow rate and the quality of the written lines (writing performance).

[0006] In view of the above-mentioned conventional problems, the present inventors have conducted extensive research and have found that the above-mentioned desired resin particle dispersion can be obtained by dispersing at least resin particles encapsulating a specific surfactant component in water, thereby completing the present disclosure.

[0007] That is, the resin particle dispersion of the present disclosure is characterized in that resin particles encapsulating at least one surfactant component selected from Group A below are dispersed in water. <Group A> Acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants. The resin particles encapsulating the surfactant component are preferably composed of a homopolymer or copolymer obtained from at least one monomer selected from Group B below. <Group B> Acrylic monomers, styrene monomers, nitrile monomers, vinyl acetate monomers. The acetylene-based surfactants and polyethylene glycol-based surfactants preferably have a water solubility of less than 10%. The acetylene-based surfactants preferably have an HLB value of 13.5 or less, the polyethylene glycol-based surfactants preferably have an HLB value of 10.0 or less, and the silicone-based surfactants preferably have an HLB value of 10.0 or less. The aqueous ink composition for a writing instrument of the present disclosure is characterized in that it contains the resin particle dispersion having the above-described configuration.

[0008] According to the present disclosure, a resin particle dispersion is provided that can efficiently exhibit a predetermined surfactant function, such as a sufficient wettability-improving effect, even in a low-temperature environment without destroying dispersion stability, and an aqueous ink composition for a writing instrument containing the resin particle dispersion has a sufficient wettability-improving effect even in a low-temperature environment without destroying the dispersion stability of the aqueous ink, thereby providing an aqueous ink composition for a writing instrument that achieves a high level of both stable writing flow rate and quality of written lines (writing performance). The objects and advantages of the present disclosure will be realized and attained by using the elements and combinations particularly pointed out in the claims. Both the general description above and the detailed description below are exemplary and explanatory and do not limit the present disclosure, which is set forth in the claims.

[0009] The embodiments of the present disclosure are described in detail below. However, it should be noted that the technical scope of the present disclosure is not limited to the respective embodiments detailed below, but extends to the inventions set forth in the claims and their equivalents. The resin particle dispersion of the present disclosure is characterized in that resin particles encapsulating at least one surfactant component selected from the following Group A are dispersed in water. <Group A> Acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants

[0010] In the present disclosure, the resin particles encapsulating at least one surfactant component selected from Group A above are not particularly limited in terms of their function or resin type, and examples thereof include homopolymers obtained from various resin monomers such as acrylic monomers, allyl monomers, isocyanate monomers, isothiocyanate monomers, epoxy monomers, diamine monomers, silyl monomers, dicarboxylic acid chloride monomers, dicarboxylic acid monomers, disulfonyl chloride monomers, dithiol monomers, divinyl monomers, diallyl monomers, styrene monomers, tetracarboxylic acid anhydride monomers, nitrile monomers, bismaleimide monomers, lactone monomers, actide monomers, fluorine-containing monomers, and cyclic olefin monomers, or copolymers combining these monomers. Preferably, the resin particle dispersion of the present disclosure is composed of a homopolymer or copolymer obtained from at least one monomer selected from Group B below, from the viewpoints of ease of encapsulation in resin particles and stability in low-temperature environments. <Group B> Acrylic monomers, styrene monomers, nitrile monomers, vinyl acetate monomers

[0011] To produce resin particles encapsulating at least one surfactant component selected from Group A above, for example, at least one surfactant component selected from Group A above and at least one of the above-mentioned monomer components are polymerized (homopolymerized or copolymerized) using a suitable polymerization initiator depending on the type of monomer, thereby obtaining each resin particle dispersion. In addition, each resin particle dispersion can be obtained by appropriately adjusting production conditions such as temperature during polymerization, stirring speed, and reaction time. Examples of resin particles of the copolymer of the above-mentioned group B include particles of copolymer of acrylic monomer and styrene monomer, particles of copolymer of acrylic monomer and nitrile monomer, particles of copolymer of acrylic monomer and vinyl acetate monomer, particles of copolymer of styrene monomer and nitrile monomer, particles of copolymer of styrene monomer and vinyl acetate monomer, particles of copolymer of nitrile monomer and vinyl acetate monomer, particles of copolymer of acrylic monomer, styrene monomer and nitrile monomer, particles of copolymer of acrylic monomer, styrene monomer and vinyl acetate monomer, particles of copolymer of acrylic monomer, nitrile monomer and vinyl acetate monomer, particles of copolymer of acrylic monomer, styrene monomer, nitrile monomer and vinyl acetate monomer.The particles composed of the homopolymer or copolymer obtained from at least one monomer selected from these group B are preferably used in view of the strength of the surfactant component that can be encapsulated as described later, the ability to produce long-lasting and stable particles, the fact that it does not have a negative effect on other compounding components, the long-lasting effect of the surfactant component.

[0012] Furthermore, the acrylic monomer that can be used is preferably a (meth)acrylic acid ester monomer represented by the following general formula (X). In the above formula (X), A is a hydrogen atom (H) or a methyl group (CH ３) wherein R represents a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a substituent having a polyalkylene glycol chain in which the alkylene chain has 2 to 18 carbon atoms, and the alkyl group or the substituent having a polyalkylene glycol chain may have, as a substituent, a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group. Examples of the alkyl group or the substituent having a polyalkylene glycol chain include a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, and an alkyl group having 1 to 18 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, a dialkylamino group, or an alkoxy group having 1 to 4 carbon atoms. In particular, an alkyl group having 1 to 6 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, or an alkoxy group having 1 to 2 carbon atoms, and an alkyl group having 1 to 6 carbon atoms which may have, as a substituent, Preferably, R in the above general formula (X) is a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a hydroxyl group, a trifluoroethyl group, a dimethylaminoethyl group, a methoxyethyl group, a hydroxyethyl group, a hydroxypropyl group, an allyl group, a tetrahydrofurfuryl group, a phenyl group, a benzyl group, a butoxydiethylene glycol group, a methoxypolyethylene glycol group, a dimethylaminoethyl group, a diethylaminoethyl group, a dimethylaminoethyl group, a glycidyl group, ethyl phosphate, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, etc. In this specification, the expression "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0013] Specific examples of the (meth)acrylic acid ester represented by the general formula (X) used include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, Isobornyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate methyl chloride salt, diethylaminoethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-Hexanediol, trimethylolpropane tri(meth)acrylate, 2-(meth)acroyloxyethyl phthalate, 2-(meth)acroyloxyethyl hexahydrophthalate, trifluoroethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, diethylene glycol (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(dimethylamino)propyl, 2-(dimethylamino)butyl (meth)acrylate, 2-isocyanoethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, perfluoroethyl methacrylate having a perfluoroalkyl group having 1 to 18 carbon atoms, 2-(phosphate)ethyl (meth)acrylate [2-(methacryloyloxy)ethyl phosphate], trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, and the like (each may be used alone or in combination of two or more, the same applies hereinafter).

[0014] Among these, from the viewpoints of industrial availability, ease and safety in handling during production, and further improving the effects of the present disclosure, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate are preferred.

[0015] In the present disclosure, in addition to the (meth)acrylic acid ester monomers, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers can be preferably used in order to obtain a sustained wetting effect, dispersion stability, a stable writing flow rate, and quality of the drawn lines (writing properties). Examples of the hydrophobic vinyl monomer include at least one monomer other than the (meth)acrylic acid ester monomers, such as styrene and methylstyrene. Examples of the hydrophobic vinyl monomers that can be used include at least one of styrene, methylstyrene, chloromethylstyrene, alkylstyrenes having an alkyl group with 1 to 12 carbon atoms, methoxystyrene, chlorostyrene, bromostyrene, divinylbenzene, phenylstyrene, and vinylnaphthalene. Examples of aqueous monomers that can be used include at least one of glycerin monomethacrylate, 2-sulfoethyl sodium methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-propylene glycol monomethacrylate, polyethylene glycol-tetramethylene glycol-monomethacrylate, and propylene glycol-polybutylene glycol-monomethacrylate.

[0016] The surfactant component used in the present disclosure may be at least one selected from acetylene-based surfactants, polyethylene glycol-based surfactants, and silicone-based surfactants. In the case of acetylene-based surfactants and polyethylene glycol-based surfactants, those with a water solubility of less than 10%, and even less than 5%, are preferred in order to produce more stable surfactant-encapsulated resin particles. The term "water solubility" as defined in the present disclosure refers to the solubility in water at 25°C (water solubility). Furthermore, the acetylene-based surfactants that can be used preferably have an HLB value of 13.5 or less, more preferably 10.0 or less, and particularly preferably 8.0 or less, in terms of dispersion stability, increasing the amount of encapsulation within the particles, and achieving a sustained wettability effect. Furthermore, in the case of polyethylene glycol-based surfactants and silicone-based surfactants, an HLB value of 10.0 or less is preferred in terms of dispersion stability, increasing the amount of encapsulation within the particles, and achieving a sustained wettability effect.

[0017] The surfactant component used in the resin particle dispersion of the present disclosure preferably has the above-described characteristics and is composed of at least one surfactant component selected from an acetylene-based surfactant, a polyethylene glycol-based surfactant, and a silicone-based surfactant. The HLB value is a measure of the surfactant properties and quantifies the balance between hydrophilic and lipophilic groups in the molecule. While several calculation methods have been proposed for the HLB value, the value used herein is calculated using the Griffin method, as shown in formula (1): HLB value = 20 × (formula weight of hydrophilic moiety) / (molecular weight of surfactant) (1). Usable acetylene-based surfactants include at least one selected from acetylene glycols, their alkylene oxide adducts, and acetylene alcohols. Specifically, at least one selected from formulas (I) to (VI) below can be used. [In the above formulas (I) to (III), R1 and R2 are each a linear or branched alkyl group having 1 to 8 carbon atoms, and m, n, x, and y are numbers from 1 to 100.]

[0018] [In the above formulas (IV) to (VI), R3, R4, and R5 represent a hydrogen atom or a linear or branched carbon chain having 0 to 10 carbon atoms, which may contain an unsaturated bond, R6 represents an alkylene group having 2 to 5 carbon atoms, and R7 represents an alkylene group having 1 to 5 carbon atoms.]

[0019] Examples of acetylene glycols and alkylene oxide adducts thereof that can be used include acetylene glycol represented by the above formula (I), a derivative (adduct) of acetylene glycol represented by the above formula (II) in which ethylene oxide (EO) is added, and a derivative (adduct) of acetylene glycol represented by the above formula (III) in which ethylene oxide (EO) or propylene oxide (PO) is added. Examples of the linear or branched alkyl group having 1 to 8 carbon atoms represented by R1 and R2 in the above formulas (I) to (III) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.

[0020] Examples of the acetylene glycol of formula (I) include 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, 5,8-dimethyl-6-dodecyne-5,8-diol, 2,4,7,9-tetramethyl-5-dodecyne-4,7-diol, 8-hexadecyne-7,10-diol, 7-tetradecyne-6,9-diol, 2,3,6,7-tetramethyl-4-octyne-3,6-diol, 3,6-diethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol. Examples of the alkylene oxide (EO, PO) adducts of acetylene glycol of formula (II) and formula (III) include alkylene oxide derivatives of the acetylene glycol.

[0021] The compounds of the general formulae (I) to (III) can be synthesized by various known methods, and commercially available compounds may also be used. Examples of acetylene glycols and alkylene oxide adducts thereof include commercially available Surfynol 104 [2,4,7,9-tetramethyl-5-dodecyne-4,7-diol, manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 4], which has a water solubility of less than 10%, Surfynol 104E (HLB value: 4), 104H, 104A (each HLB value: 4) obtained by diluting Surfynol 104 with various solvents, the Surfynol 104 series such as 104S containing silica particles, and EO adducts of Surfynol 104 such as 420 (HLB value: 4), 440 (HLB value: 8), DF110D (HLB value: 3), DF37, DF58, DF75, and DF220.

[0022] The acetylene alcohols represented by formulas (IV) to (VI) above have an acetylene group (—C≡C—) and a hydroxyl group (—OH) in their molecular structure. R3, R4, and R5 in the general formulas (IV) to (VI) above each represent a hydrogen atom, a linear or branched alkyl group, an alkenyl group, an aryl group, or an aralkyl group. The alkyl and alkenyl groups may be linear, branched, or cyclic, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, and a cyclohexenyl group. The aryl group may have a substituent such as a lower alkyl group on the aromatic ring, such as a phenyl group, tolyl group, xylyl group, or naphthyl group. The aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, such as a benzyl group, phenethyl group, or naphthylmethyl group. R6 in the general formula (V) represents an alkylene group having 2 to 5 carbon atoms. The alkylene group may be linear, branched, or cyclic, with linear alkylene groups being particularly preferred. Examples of linear alkylene groups include ethylene, trimethylene, tetramethylene, and pentamethylene. R7 in the general formula (VI) represents an alkylene group having 1 to 5 carbon atoms. The alkylene group is a methylene group (having 1 carbon atom). For alkylene groups having 2 or more carbon atoms, the alkylene group is the same as R6 in the general formula (V).

[0023] Specific examples of the acetylene alcohols of the general formula (IV) or derivatives thereof include 2-butyn-1-ol, 3-butyn-2-ol, 2-decyn-1-ol, 3,6-dimethyl-1-heptyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3,4-dimethyl-1-pentyn-3-ol, 1,1-diphenyl-2-propyn-1-ol, 3-ethyl-1-heptyn-3-ol, 4-ethyl-1-octyn-3-ol, 3-ethyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, 9-ethynyl-9-fluorenol, 1-heptyn- 3-ol, 2-heptyn-1-ol, 1-hexyn-3-ol, 2-hexyn-1-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-penten-4-yn-3-ol, 3-methyl-1-pentyn-3-ol, 2-methyl-4-phenyl-3-butyn-2-ol, 1-octyn-3-ol, 1-pentyn-3-ol, 2-pentyn-1-ol, 1-phenyl-2-propyn-1-ol, 3-phenyl-2-propyn-1-ol, 2-propyn-1-ol, 1,1,3-triphenyl-2-propyn-1-ol, and the like.

[0024] Specific examples of the acetylene alcohols of general formula (V) or derivatives thereof include at least one of 3-butyn-1-ol, 3-decyn-1-ol, 9-decyn-1-ol, 3-heptyn-1-ol, 3-hexyn-1-ol, 5-hexyn-1-ol, 3-nonyn-1-ol, 3-octyn-1-ol, 3-pentyn-1-ol, 4-pentyn-1-ol, 5-phenyl-4-pentyn-1-ol, 10-undecyn-1-ol, etc. Specific examples of the acetylene alcohols of general formula (VI) or derivatives thereof include at least one of 4-heptyn-2-ol, 5-heptyn-3-ol, 5-hexyn-3-ol, 4-pentyn-2-ol, etc. Among the compounds specifically listed in the general formulas (IV) to (VI) above, it is preferable to use 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol in terms of usability, cost, safety, and further exerting the effects of the present disclosure.

[0025] The synthesis methods for each of the compounds represented by the general formulas (IV) to (VI) are known, and the compounds can be obtained by various production methods. Alternatively, commercially available products may be used. For example, acetylene alcohols include commercially available products having a water solubility of less than 10%, such as Surfynol 61 (3,5-dimethyl-1-hexyn-3-ol), Olfine A (2,5-dimethylhexane-2,5-diol), Olfine B (3-methyl-1-butyn-3-ol), Olfine P (3-methyl-1-pentyn-3-ol), Olfine PD-002W, EXP. 4200, WE-003, SPC, and other olphin-based products manufactured by Nissin Chemical Industry Co., Ltd.

[0026] Usable polyethylene glycol surfactants include polyethylene glycol ethers and polyethylene glycol esters, and it is preferable to use the following general formula (VII). In the above formula (VII), R8 and R9 are hydrogen atoms or C ｎ H ２ｎ＋１, n is a number from 1 to 20, and m is a number from 5 to 40. Among the polyethylene glycol surfactants represented by the above formula (VII), the alkyl groups such as R8 and R9 preferably have 4 to 20 carbon atoms, more preferably 5 to 18 carbon atoms, and particularly preferably 8 to 15 carbon atoms. Furthermore, the ethylene oxide group -(CH ２ -CH ２ In —O)m—, the number of moles of ethylene oxide added, m, is preferably 10 to 40, more preferably 20 to 40, and particularly preferably 30 to 40.

[0027] As with the acetylene surfactants described above, in order to obtain more stable surfactant-encapsulated resin particles, this polyethylene glycol surfactant preferably has a water solubility of less than 10%, and more preferably has an HLB value of 10.0 or less, more preferably 8.0 or less, and particularly preferably 5.0 or less. Specific examples of polyethylene glycol surfactants that can be used include at least one of commercially available surfactants with a water solubility of less than 10%, such as EGMS-70V (manufactured by Nikko Chemicals Co., Ltd., HLB value: 3.5), MYO-6V (manufactured by Nikko Chemicals Co., Ltd., HLB value: 8.5), and ADEKA Estol OEG-102 (manufactured by ADEKA Corporation, HLB value: 7.9).

[0028] In terms of obtaining more stable surfactant-encapsulated resin particles, silicone surfactants with an HLB value of 10.0 or less, more preferably 9.0 or less, and particularly preferably 8.0 or less are desirable. Examples of silicone surfactants include dimethyl silicone, cyclic silicone, trimethylsiloxysilicate, and methylphenyl silicone. Further preferred examples of silicone surfactants include polyether-modified silicone, methylstyryl-modified silicone, alkyl-modified silicone, higher fatty acid ester-modified silicone, higher alkoxy-modified silicone, fluorine-modified silicone, fluorine-based alkyl ester, polyether-modified silicone, polyglycerin-modified silicone, polyether-alkyl co-modified silicone, polyglycerin-alkyl co-modified silicone, and polyether-silicone-alkyl co-modified silicone. Any of linear, branched, and crosslinked types can be used, and emulsion types are also acceptable. These silicone surfactants can be used alone or in combination of two or more.

[0029] Specific examples of silicone surfactants that can be used include at least one of commercially available surfactants with an HLB value of 8.0 or less, such as KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 4.5), KF-6004 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 9.0), KF-6038 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 3.0), and KF-6012 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 7.0).

[0030] The resin particle dispersions of the present disclosure are characterized in that resin particles encapsulating at least one surfactant component selected from Group A above are dispersed in water. As a production method thereof, for example, each resin particle dispersion can be obtained by polymerizing (homopolymerizing or copolymerizing) at least one surfactant component selected from Group A above and at least one of the above-mentioned monomer components using a suitable polymerization initiator or the like. Furthermore, each resin particle dispersion can be obtained by appropriately adjusting production conditions such as temperature during polymerization, stirring speed, and reaction time.

[0031] In the resin particle dispersion composed of a homopolymer or copolymer obtained from at least one monomer selected from the acrylic monomers of Group B, styrene monomers, nitrile monomers, and vinyl acetate monomers, for example, at least one surfactant component selected from the acetylene-based surfactants and polyethylene glycol-based surfactants is dissolved in a styrene monomer, a nitrile monomer, a vinyl acetate monomer, a (meth)acrylic acid ester monomer, or the like (each alone or in combination of two or more, the same applies hereinafter), or in a mixed monomer containing a monomer such as the (meth)acrylic acid ester monomer and another hydrophobic vinyl monomer and / or an aqueous monomer, and ammonium persulfate, potassium persulfate, hydrogen peroxide, or the like is used as a polymerization initiator, and a reducing agent is further used in combination with the polymerization initiator, and triallyl isocyanurate, triallyl isocyanurate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol acrylate, ditrimethylolpropane acrylate, dipentaerythritol acrylate, methoxylated bisphenol A methacrylate, , pentaerythritol methacrylate, ditrimethylolpropane methacrylate, dipentaerythritol methacrylate, ethoxylated polyglycerin methacrylate, or other crosslinking agents; and, if necessary, polyoxyethylene-1-(allyloxymethyl)-alkyl ether ammonium sulfate, ether sulfate, polyoxyethylene nonylpropenylphenyl ether ammonium sulfate, polyoxyethylene nonylpropenylphenyl ether, ammonium polyacrylate, styrene-maleic acid copolymer ammonium, polyoxyethylene alkyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene decyl ether, polyoxyethylene tridecyl ether, alkylbenzene sulfonate, dioctyl sulfosuccinate, sodium lauryl sulfate, polyoxyethylene alkyl ether phosphate ester, polyoxyethylene styrenated phenyl ether phosphate ester, polyoxyethylene styrenated phenyl ether sulfate, polyoxyethylene alkyl ether sulfate,It can be produced by emulsion polymerization using a polymerizable surfactant (emulsifier) ​​such as polyoxyethylene sorbitan monolaurate (polysorbate 20), polyoxyethylene sorbitan palmitate (polysorbate 40), polyoxyethylene sorbitan monostearate (polysorbate 60), or polyoxyethylene sorbitan oleate (polysorbate 80), and after being produced as a dispersion of resin particles, it can be dried or the like to form a resin particle dispersion. The use of a crosslinking agent such as triallyl isocyanurate is preferred because it can improve the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the resin particle dispersion.

[0032] During the emulsion polymerization, the styrene monomer, nitrile monomer, vinyl acetate monomer, (meth)acrylic acid ester monomer, etc. may be further mixed with an appropriate amount of dicyclopenta(tenyl)(meth)acrylate monomer, etc., to carry out emulsion polymerization. When this dicyclopenta(tenyl)(meth)acrylate monomer is further mixed and then emulsion polymerized, stability is less likely to be lost even if water in the dispersion evaporates, and an even more stable surfactant-encapsulated resin particle dispersion can be obtained. Usable dicyclopenta(tenyl)(meth)acrylate monomers include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate.

[0033] In the present disclosure, during the emulsion polymerization, in addition to the dicyclopenta(thenyl)(meth)acrylate monomer, an appropriate amount of a monomer having a reactive crosslinking group such as an epoxy group, a hydroxymethylamide group, or an isocyanate group, or a polyfunctional monomer having two or more vinyl groups may be blended and crosslinked, such as the styrene monomer, nitrile monomer, vinyl acetate monomer, acrylic acid monomer, or other hydrophobic vinyl monomer.

[0034] In the present disclosure, among the polymer components constituting the resin particle dispersion, the content of the monomers of Group B is preferably 30% by mass or more, more preferably 30 to 95% by mass, and particularly preferably 30 to 70% by mass, relative to the total polymer components constituting the resin particle dispersion. In the present disclosure, the term "total polymer components" refers to the polymerizable components constituting the resin particle dispersion, specifically the total amount including all types of monomers and crosslinkers that are raw materials for the final polymer. For Group B, the term refers to the total amount of the monomers of Group B used, other monomer components used, and the crosslinker described below. In the case of a dispersion using a monomer of Group B, the effects of the present disclosure can be further enhanced by setting the content of the monomers of Group B to 30% by mass or more relative to the total polymer components. On the other hand, if the content is less than 30% by mass, the stability over time tends to be poor.

[0035] In the present disclosure, when the (meth)acrylic acid ester monomer or the like of Group B is used among the polymer components constituting the resin particle dispersion, the content of other monomer components other than Group B is the remainder of the total amount of the (meth)acrylic acid ester monomer or the like used and the crosslinking agent described below. Preferably, the content of other monomer components is 0.5 to 70 mass% with respect to the total polymer components, from the viewpoints of further exerting the effects of the present disclosure, dispersibility, and reactivity.

[0036] In the present disclosure, the total (solid content) content of the surfactants is desirably 1% by mass or more, preferably 5% by mass or more, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass, based on the total polymer components, from the viewpoints of obtaining sufficient surfactant performance, obtaining a sustained surfactant effect, etc., stability, etc. By setting the content of the surfactant components to 1% by mass or more, sufficient surfactant performance and a sustained surfactant effect can be exerted, while if the content of the surfactant components is less than 1% by mass, the surfactant performance will be insufficient and the effects of the present disclosure will not be exerted.

[0037] The polymerizable surfactant that can be used as needed is not particularly limited as long as it is a polymerizable surfactant that is commonly used in the emulsion polymerization. For example, the polymerizable surfactant may be an anionic or nonionic polymerizable surfactant, such as ADEKA REASOAP NE-10, NE-20, NE-30, NE-40, SE-10N, SR-10, SR-20, ER-10, ER-20, ER-30, ER-40, or PP manufactured by ADEKA Corporation. -70, Kao Corporation's Latemul S-180, S-180A, S-120A, PD-420, PD-430, PD-450, Sanyo Chemical Industries, Ltd.'s Eleminol JS-20, CLS-20, RS-3000, Dai-ichi Kogyo Seiyaku Co., Ltd.'s Aqualon AN-10, AN-20, AN-30, AN-5065, KH-05, KH-10, KH-1025, HS-10, AR-10, AR-1025, AR-20, and Tosoh Finechem's Spinomer NaSS. The amount of these polymerizable surfactants used is 0 to 50% by mass, preferably 0.1 to 50% by mass, based on the total amount of the monomers. The content of the crosslinking agent such as triallyl isocyanurate is preferably 0 to 50% by mass, and more preferably 0.1 to 25% by mass, based on the total amount of the monomers.

[0038] In the present disclosure, the preferred embodiment, specifically, the polymerization provides a resin particle dispersion (liquid dispersion) in which resin particles composed of a homopolymer obtained from each resin monomer or a copolymer combining these monomers, each having a surfactant component encapsulated therein, are dispersed in water. Alternatively, a resin particle dispersion (liquid dispersion) can be obtained by dissolving at least one surfactant component selected from the above-mentioned acetylene surfactants and polyethylene glycol surfactants in a monomer selected from Group B acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monomers, followed by emulsion polymerization, or by polymerizing a monomer mixture containing at least one monomer selected from the above-mentioned acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monomers and other monomer components, followed by dissolving the surfactant component and emulsion polymerization. The amount of resin particles in the resin particle dispersion obtained under these production conditions varies depending on the amount of the resin monomers (such as Group B monomers) and surfactant components used, the polymerization conditions, etc. From the standpoints of manufacturability, workability, efficiency, etc., it is preferable to produce the resin particle dispersion so that the solid content is 1 to 50% by mass. More preferably, the solid content is produced to be 10 to 40% by mass.

[0039] These resin particle dispersions (dispersions) are more stable than those using the surfactant component alone by using the resin particle dispersions of the present disclosure, as they have strong and durable surfactant performance without adversely affecting other formulation components. In particular, resin particle dispersions are obtained that can maintain or improve the surfactant effect of the surfactant component even after long-term storage. Furthermore, the present disclosure preferably uses a surfactant component with a specific solubility or HLB as the surfactant component. Therefore, in particular, to address the issues of dispersion stability and ink penetration without bleeding, encapsulating the surfactant component in particles made of the resin monomers of the present disclosure, preferably monomers of Group B, improves the quality of written lines while suppressing bleeding, and is expected to provide a sustained wetting effect.

[0040] In the present disclosure, the average particle size of the resin particles in the resulting resin particle dispersion varies depending on the monomer used, the type and content of other monomers used, the polymerization conditions during polymerization, and the like, but is preferably 10 to 800 nm, more preferably 20 to 300 nm, and even more preferably 30 to 200 nm. By setting the average particle size within the above preferred range, the resin particles can be further improved in storage stability and can be used in an average particle size range suitable for each application described below. When used in aqueous inks for writing instruments, the resin particles do not clog the cores of writing instruments such as felt-tip pens, marking pens, and ballpoint pens, and further improve storage stability. The "average particle size" defined in the present disclosure is the histogram average particle size obtained by scattering light intensity distribution, and in the present disclosure (including the examples described below), it is the D50 value measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)].

[0041] In the resin particle dispersion of the present disclosure, the content of the resin particles contained in the dispersion is preferably 0.1 to 50 mass % in terms of solid content, and more preferably 1 to 30 mass % depending on the intended use, etc., as described below. If the content of the resin particles is less than 0.1 mass % in terms of solid content, the effects of the present disclosure cannot be exhibited, whereas if it exceeds 50 mass %, long-term storage stability is likely to decrease.

[0042] The resin particle aqueous dispersion of the present disclosure thus constructed can efficiently exhibit predetermined surfactant properties, such as a sufficient wettability-improving effect, even at low temperatures without destroying dispersion stability. Therefore, the resin particle aqueous dispersion can be used to impart surfactant properties, such as wettability, to a variety of products, including cosmetics and ink compositions for writing instruments and inkjet printers. The resin particle aqueous dispersion can be used to impart surfactant properties, such as wettability, to a variety of products, including cosmetics, ink compositions for writing instruments and inkjet printers, and to impart surfactant properties, such as wettability, to a variety of products, including detergents, such as laundry detergents, fabric softeners, household detergents, dishwashing detergents, and hard surface cleaners, which have previously contained acetylene-based surfactants, polyethylene glycol-based surfactants, and the like; personal care products, such as shampoos, conditioners, lotions, emulsions, creams, sunscreens, foundations, eye makeup products, antiperspirants, and toothpaste; paints, adhesives, building materials, wood preservatives, cement admixtures, and ink compositions for writing instruments and inkjet printers. The resin particle dispersion of the present disclosure is highly stable and exhibits excellent surface activity effects, such as the wettability of surfactant components, even at low temperatures and after long-term storage, while not affecting other blended components. Therefore, as described above, the resin particle dispersion can be used to improve the wettability of various products, and can be particularly suitably used in aqueous inks, inks for inkjet printers, detergent applications, personal care applications, paints for building materials, eyeliner inks, hair care applications, and inks for adhesives and pressure-sensitive adhesives. For example, the use of the resin particle dispersion in an aqueous ink composition for writing instruments will be described below.

[0043]

[0033] (Aqueous ink composition for writing instruments) The aqueous ink composition for writing instruments of the present disclosure is characterized by containing at least the resin particle dispersion described above, and may contain a colorant and a water-soluble organic solvent in addition to the resin particle dispersion. From the viewpoints of exhibiting the effects of the present disclosure without impairing writing performance and of storage stability, the content of the resin particle dispersion in the ink composition is preferably 0.1 to 30.0 mass %, more preferably 1.0 to 15.0 mass %, in terms of solid content, relative to the total amount of the ink composition.

[0044] Usable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, and plastic pigments; hollow resin particles with internal voids can be used as white pigments; colored resin particles (pseudo-pigments) dyed with dyes that have excellent color development and dispersibility; thermochromic pigments; photochromic pigments; and luster pigments such as aluminum pigments. As water-soluble dyes, direct dyes, acid dyes, food dyes, and basic dyes can all be used in appropriate amounts as long as the effects of the present disclosure are not impaired. The content of these colorants varies depending on the type of writing instrument, but is generally 1 to 30% by mass of the total ink composition.

[0045] Examples of usable water-soluble organic solvents include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol, 2-methylpentane-2,4-diol, 3-methylpentane-1,3,5triol, and 1,2,3-hexanediol. Examples thereof include at least one of alkylene glycols such as triols, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, glycerols such as glycerol, diglycerol and triglycerol, lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethylene glycol mono-n-butyl ether, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidalidinone.

[0046] Other water-soluble solvents that can be mixed include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol, amides such as dimethylformamide and diethylacetamide, and ketones such as acetone. The content of these water-soluble organic solvents varies depending on the type of writing implement, such as a felt-tip pen, marking pen, or ballpoint pen, and is particularly effective in an ink composition with a content of 1 to 40% by mass, and 10% by mass or less, based on the total amount of the ink composition, from the viewpoint of further improving the drying properties of drawn lines, and more preferably 3 to 8% by mass.

[0047] The aqueous ink composition for a writing instrument of the present disclosure may contain, in addition to the particles, colorant, and water-soluble solvent having the above-described properties, water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as the solvent as the remainder, as well as dispersants, lubricants, pH adjusters, rust inhibitors, thickeners, evaporation inhibitors, surfactants, and the like, as appropriate, within limits that do not impair the effects of the present disclosure.

[0048] Usable dispersants include nonionic and anionic surfactants other than the above-mentioned acetylene surfactants and polyethylene glycol surfactants, and water-soluble resins. Preferably, water-soluble polymers are used. Examples of lubricants include nonionic lubricants such as polyhydric alcohol fatty acid esters, sugar higher fatty acid esters, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic lubricants such as alkyl sulfonates and alkyl aryl sulfonates of higher fatty acid amides; polyalkylene glycol derivatives, fluorine-based surfactants, and polyether-modified silicones.

[0049] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonate or phosphate such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of thickeners include carboxymethyl cellulose (CMC) or its salts, cellulose derivatives such as fermented cellulose and crystalline cellulose, and polysaccharides. Examples of polysaccharides that can be used include xanthan gum, guar gum, hydroxypropylated guar gum, casein, gum arabic, gelatin, amylose, agarose, agaropectin, arabinan, curdlan, callose, carboxymethyl starch, chitin, chitosan, quince seed, glucomannan, gellan gum, tamarind seed gum, dextran, nigeran, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkaloid gum, succinoglycan, locust bean gum, and tara gum. These may be used alone or in combination. Furthermore, commercially available products of these may be used. Examples of evaporation inhibitors include pentaerythritol, p-xylene glycol, trimethylolpropane, triethylolpropane, and dextrin. Examples of surfactants include fluorine-based, silicone-based, acetylene glycol-based, etc. Furthermore, in the present disclosure, from the viewpoint of improving the quality of written lines, it is preferable to use olefin-based resin particles, and the content of these olefin-based resin particles is desirably 0.01 to 20% by mass, and preferably 1 to 5% by mass, relative to the total amount of the ink composition.The olefin resin particles that can be used are not particularly limited in shape or structure, so long as they have a penetration hardness of 1 or more and an average particle diameter measured by the Coulter counter method of 15 μm or less, and examples of commercially available products include Chemipearl W100, W200, W400, and W500 manufactured by Mitsui Chemicals, Inc., and examples of similar olefin resin particles (Chemipearl products) include Chemipearl W300, W308, W310, W700, and W900. If the penetration hardness is 1 or more, improved ink outflow can be expected, and a stable writing flow rate can be obtained.

[0050] The aqueous ink composition for a writing instrument of the present disclosure can be prepared by appropriately combining the resin particle dispersion having the above-described properties, the water-soluble solvent, and other components depending on the intended use of the ink for the writing instrument (for a ballpoint pen, a marking pen, etc.), stirring and mixing them using a stirrer such as a homomixer, a homogenizer, or a disper, and then, if necessary, removing coarse particles from the ink composition by filtration or centrifugation.

[0051] Furthermore, the pH (25°C) of the aqueous ink composition for a writing instrument of the present disclosure is preferably adjusted to 5 to 10 using a pH adjuster or the like, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, and more preferably 6 to 9.5.

[0052] The aqueous ink composition for writing instruments of the present disclosure is incorporated into ballpoint pens, marking pens, and the like, equipped with a pen tip such as a ballpoint pen tip, fiber tip, felt tip, or plastic tip. Examples of ballpoint pens include those in which the aqueous ink composition for writing instruments having the above-described composition is contained in a ballpoint pen ink reservoir (refill) equipped with a ball having a diameter of 0.18 to 2.0 mm, and in which a substance that is incompatible with the aqueous ink composition contained in the ink reservoir and has a low specific gravity relative to the aqueous ink composition, such as polybutene, silicone oil, or mineral oil, is contained as an ink follower. In addition, the amount of movement (distance) of the writing ball in the axial direction (vertical direction) in the ballpoint pen is preferably 15 to 80 μm, from the viewpoints of appropriately ejecting resin particles and stabilizing the writing flow rate. The structure of the ballpoint pen or marking pen is not particularly limited, and may be, for example, a direct ink ballpoint pen or marking pen having a collector structure (ink retention mechanism) in which the barrel itself serves as an ink container and is filled with the aqueous ink composition for a writing instrument having the above-described structure.

[0053] In the aqueous ink composition for writing instruments of the present disclosure, which is configured in this manner, the resin particle dispersion having the above-described properties is blended into the aqueous ink composition for writing instruments. This prevents the instability of the dispersion system and the formation of precipitates that frequently occur when an acetylene-based surfactant or the like is directly added in the past, and provides a sufficient wettability-improving effect, making it possible to stably blend the composition into a variety of aqueous inks. In particular, depending on the liquid temperature of the ink, particularly in a low-temperature environment, direct addition can reduce solubility, making it difficult to obtain a sufficient activator effect after low-temperature storage, making it difficult to obtain a stable writing flow rate, and causing unevenness in the writing flow rate, which in turn reduces the quality of the written lines. However, according to the present disclosure, by preparing the present resin particle dispersion that encapsulates an acetylene-based surfactant and / or a polyethylene glycol-based surfactant component, it is possible to obtain an aqueous ink composition for a writing instrument that has a sufficient wettability-improving effect even in a low-temperature environment, without destroying the dispersion stability of the original aqueous ink, and that achieves a high level of both a stable writing flow rate and quality (writing ability) of the written lines.

[0054] (Aqueous inkjet ink composition) The aqueous inkjet ink composition of the present disclosure is characterized by containing at least the resin particle dispersion having the above-described configuration, and may contain, in addition to this resin particle dispersion, a colorant and a solvent such as a water-soluble organic solvent.

[0055] Usable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, and plastic pigments. Hollow resin particles with internal voids can be used as white pigments, or colored resin particles (pseudo pigments) dyed with dyes exhibiting excellent color development and dispersibility, and luster pigments such as aluminum pigments. As water-soluble dyes, direct dyes, acid dyes, food dyes, and basic dyes can all be used in appropriate amounts within a range that does not impair the effects of the present disclosure. The content of these colorants varies depending on the inkjet device and method, but is generally 1 to 30% by mass based on the total amount of the ink composition. When used in an aqueous inkjet ink composition, the resin particle dispersion may further enhance stability over time, antiseptic properties, color development, fragrance, and light resistance by incorporating a preservative, reducing agent, fragrance, oil, ultraviolet absorber, light stabilizer, and the like, in addition to the surfactant component of Group A.

[0056] This aqueous inkjet ink composition can be prepared by adding a colorant and a solvent to the inkjet colored resin particle dispersion having the above-described configuration and stirring the mixture. If necessary, a resin, a dispersant, etc. may also be added. The solvent used in the inkjet ink is not particularly limited, but specifically, water (purified water, ion-exchanged water, distilled water, pure water, etc., hereinafter simply referred to as "water") and water-soluble organic solvents can be used as mixed solvents. The water content, which is the remainder of the contents of each component, is approximately 1.0 to 70.0% by mass.

[0057] Examples of water-soluble organic solvents that can be used include alkyl alcohols having 1 to 4 carbon atoms, such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols, such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols, such as polyethylene glycol and polypropylene glycol; alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; glycerin; lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred. The content of the water-soluble organic solvent is preferably in the range of 3 to 50% by mass, more preferably 3 to 30% by mass, based on the total amount of the ink composition.

[0058] The resin used in inkjet inks is not particularly limited as long as it dissolves or disperses in the solvents blended into the ink. Specific examples include acrylic resins, polyester resins, phenolic resins, polyamides, polyvinyl butyral, cellulose acetate butyrate, nitrocellulose resins, urethane resins, and vinyl chloride-vinyl acetate copolymers. These can be used alone or in combination. The type of resin can be selected depending on the type of medium. Preferred resins include urethane resin emulsions, acrylic resin emulsions, styrene resin emulsions, styrene-acrylic resin emulsions, and olefin resin emulsions, which have excellent functionality as fixing resins. The content of these resins is preferably in the range of 0.1 to 50.0% by mass, and more preferably 3.0 to 30.0% by mass, of the total amount of the ink composition.

[0059] In the aqueous inkjet ink composition of the present disclosure, the above-described resin particle dispersion can be used as is, or the above-described colorant, solvent, and, if necessary, resin and dispersant can be blended. Furthermore, various additives commonly used in the relevant field can be added within a range that does not impair the object of the present disclosure. For example, a nozzle clogging inhibitor, an antioxidant, a conductivity adjuster, a viscosity adjuster, a surfactant, an oxygen absorber, etc. can be added as appropriate. The types of these additives are not particularly limited, and those commonly used in the relevant field can be used. The resin particle dispersion can also be diluted with a non-aqueous solvent.

[0060] The content of the colored resin particles varies depending on the printing method, etc., but is preferably 1 to 30 mass % in terms of solid content relative to the total amount of the aqueous inkjet ink composition. The viscosity of the aqueous inkjet ink composition varies in an appropriate range depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but is usually preferably 1 to 20 mPa s at 25°C.

[0061] The inkjet recording method using the aqueous inkjet ink composition of the present disclosure is not particularly limited, and examples thereof include known methods, such as a charge control method that uses electrostatic attraction to eject the ink composition, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink composition with the radiation pressure to eject the ink composition, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink composition to form bubbles and uses the resulting pressure. The recording medium is not particularly limited, and examples thereof include plain paper, glossy paper, copy paper, special paper, cloth, film, and overhead projector sheets.

[0062] The aqueous inkjet ink composition of the present disclosure configured as described above is highly stable and contains a resin particle dispersion that exhibits excellent surface activity effects, such as the wettability of the surfactant component, even at low temperatures and after long-term storage, and does not affect other formulation components, making it suitable for aqueous inkjet ink compositions with improved wettability. Furthermore, these particles do not impair storage stability or inkjet performance, can be made small in particle size, and are free from issues such as clogging of nozzles, etc., and are therefore remarkably excellent in functionality for inkjet applications that exhibit excellent performance. Therefore, an aqueous inkjet ink composition can be obtained that is suitable for any printing method, such as piezo, electrostatic, or thermal, and for printing on plain paper, glossy paper, special paper, fabric (clothing such as T-shirts), film, OHP sheets, etc.

[0063] Next, the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples, etc.

[0064] [Production Examples 1 to 22: Production of Resin Particle Dispersions (Particles 1 to 22)] Each resin particle dispersion was produced according to the following Production Examples 1 to 22. Note that the "parts" below represent parts by mass. The surfactant component is the solid content.

[0065] Production Example 1 A 2-liter flask was equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000 ml separatory funnel for monomer introduction, and set in a warm water bath. 354.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blemmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 20 parts of a polymerizable surfactant (ADEKA Corporation, Adeka Reasoap SR-10, ether sulfite), and 0.5 parts of ammonium persulfate were then charged, and the internal temperature was raised to 50° C. while introducing nitrogen gas.

[0066] Separately, a solution was prepared by mixing a monomer mixture consisting of 55 parts of cyclohexyl methacrylate monomer and 20 parts of n-butyl methacrylate with 20 parts of an acetylene surfactant 1 [Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3] as a surfactant component, and 10 parts of a crosslinker [triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., TAIC]. This prepared solution was added from the separatory funnel to the flask maintained at a temperature of approximately 90°C over a period of 3 hours with stirring, and emulsion polymerization was carried out. The mixture was further aged for 5 hours to terminate the polymerization, yielding a resin particle dispersion (dispersion) (particles 1). The content of the methacrylic acid ester monomer was 58.6% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 20.7% by mass, based on the total polymer components. The average particle size of the resin particles was 62 nm.

[0067] (Production Example 2) A resin particle dispersion (dispersion liquid) (particles 2) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and 30 parts of an acetylene-based surfactant 2 [Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4] was used as the surfactant component. The content of the methacrylic acid ester monomer was 60.0% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 20.0% by mass, based on the total polymer components. The average particle diameter of the resin particles was 68 nm.

[0068] (Production Example 3) A resin particle dispersion (dispersion liquid) (particles 3) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 45 parts, the amount of n-butyl methacrylate was 35 parts, and 30 parts of an acetylene-based surfactant 3 [Surfynol 440; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 8] was used as the surfactant component. The content of the methacrylic acid ester monomer was 60.0% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 20.0% by mass, based on the total polymer components. The average particle diameter of the resin particles was 112 nm.

[0069] (Production Example 4) A resin particle dispersion (dispersion liquid) (particles 4) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 337.5 parts, the amount of cyclohexyl methacrylate monomer was 28 parts, the amount of n-butyl methacrylate was 44 parts, and 30 parts of an acetylene-based surfactant 4 [Olfine EXP. 4200; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.1-1.0%, HLB value: 10-13] was used as the surfactant component. The content of the methacrylic acid ester monomer was 50.6% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 18.5% by mass, based on the total polymer components. The average particle diameter of the resin particles was 71 nm.

[0070] (Production Example 5) A resin particle dispersion (dispersion) (particles 5) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 15 parts of an acetylene-based surfactant 5 (Olfine PD-002W; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.3-0.5%, HLB value: 9-10) was used as the surfactant component. The content of the methacrylic acid ester monomer was 56.7% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 10.0% by mass, based on the total polymer components. The average particle diameter of the resin particles was 51 nm.

[0071] (Production Example 6) A resin particle dispersion (dispersion liquid) (particles 6) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 334.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 30 parts of an acetylene-based surfactant 6 (Dynol 604; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 8) was used as the surfactant component. The content of the methacrylic acid ester monomer was 51.5% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 18.2% by mass, based on the total polymer components. The average particle diameter of the resin particles was 60 nm.

[0072] (Production Example 7) A resin particle dispersion (dispersion) (particles 7) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 339.0 parts, the amount of cyclohexyl methacrylate monomer was 30.5 parts, the amount of n-butyl methacrylate was 45 parts, and 25 parts of an acetylene-based surfactant 7 (Surfynol SE-F; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 6) was used as the surfactant component. The content of the methacrylic acid ester monomer was 53.3% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 15.6% by mass, based on the total polymer components. The average particle diameter of the resin particles was 43 nm.

[0073] (Production Example 8) A resin particle dispersion (dispersion) (particles 8) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 339.5 parts, the amount of cyclohexyl methacrylate monomer was 30.0 parts, the amount of n-butyl methacrylate was 45.0 parts, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the methacrylic acid ester monomer was 53.1% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 15.6% by mass, based on the total polymer components. The average particle diameter of the resin particles was 82 nm.

[0074] (Production Example 9) A resin particle dispersion (dispersion) (particles 8) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 334.5 parts, the amount of cyclohexyl methacrylate monomer was 45.0 parts, the amount of n-butyl methacrylate was 30.0 parts, and 9.0 parts of a silicone surfactant [KF-6004; PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the methacrylic acid ester monomer was 51.5% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 18.2% by mass, based on the total polymer components. The average particle diameter of the resin particles was 104 nm.

[0075] (Production Example 10) A liquid was prepared by mixing 369.5 parts of distilled water, 50 parts of methacrylonitrile monomer, 40 parts of an acetylene-based surfactant 1 (Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component, 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC), and 30 parts of an acetylene-based surfactant 2 (Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as a surfactant component. This prepared liquid was added from the separatory funnel to the flask maintained at a temperature of about 90°C over 3 hours with stirring, and emulsion polymerization was carried out. The resulting mixture was further aged for 5 hours to complete the polymerization, and the resin particle dispersion (liquid dispersion) was recovered to obtain a resin particle dispersion (liquid dispersion) (particles 10). The content of the nitrile monomer was 38.5% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 23.1% by mass, based on the total polymer components. The average particle diameter of the resin particles was 87 nm.

[0076] (Production Example 11) A resin particle dispersion (dispersion) (particles 11) was obtained in the same manner as in Production Example 10, except that the amount of distilled water was 370.5 parts, the amount of methacrylonitrile monomer was 54 parts, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the nitrile monomer was 41.9% by mass, based on all polymer components constituting the resin particles, and the content of the surfactant component was 19.4% by mass, based on all polymer components. The average particle diameter of the resin particles was 91 nm.

[0077] (Production Example 12) A resin particle dispersion (dispersion) (particles 12) was obtained in the same manner as in Production Example 10, except that the amount of distilled water was 374.5 parts, the amount of methacrylonitrile monomer was 45 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the nitrile monomer was 36.0% by mass, based on all polymer components constituting the resin particles, and the content of the surfactant component was 24.0% by mass, based on all polymer components. The average particle diameter of the resin particles was 101 nm.

[0078] Production Example 13 A liquid was prepared by mixing 364.5 parts of distilled water, 75 parts of styrene monomer, 40 parts of an acetylene-based surfactant 1 (Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component, 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Industry Co., Ltd., TAIC), and 30 parts of an acetylene-based surfactant 2 (Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as a surfactant component. This prepared liquid was added from the separatory funnel to the flask maintained at a temperature of about 90°C with stirring over 3 hours, and emulsion polymerization was carried out. The resulting mixture was further aged for 5 hours to complete the polymerization, and the resulting resin particle dispersion (liquid dispersion) was recovered to obtain a resin particle dispersion (liquid dispersion) (particles 13). The content of the styrene monomer was 48.4% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 19.4% by mass, based on the total polymer components. The average particle diameter of the resin particles was 58 nm.

[0079] (Production Example 14) A resin particle dispersion (dispersion) (particles 14) was obtained in the same manner as in Production Example 13, except that the amount of distilled water was 354.5 parts, the amount of styrene monomer was 70 parts, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the styrene monomer was 48.3% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 17.2% by mass, based on the total polymer components. The average particle diameter of the resin particles was 77 nm.

[0080] (Production Example 15) A resin particle dispersion (dispersion) (particles 15) was obtained in the same manner as in Production Example 13, except that the amount of distilled water was 339.5 parts, the amount of styrene monomer was 80 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the styrene monomer was 50.0% by mass, based on all polymer components constituting the resin particles, and the content of the surfactant component was 18.8% by mass, based on all polymer components. The average particle diameter of the resin particles was 91 nm.

[0081] Production Example 16 A liquid was prepared by mixing 354.5 parts of distilled water, 65 parts of vinyl acetate monomer, 40 parts of an acetylene-based surfactant 1 (Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component, 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Industry Co., Ltd., TAIC), and 30 parts of an acetylene-based surfactant 2 (Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as a surfactant component. This prepared liquid was added from the separatory funnel to the flask maintained at a temperature of about 90°C with stirring over 3 hours, and emulsion polymerization was carried out. The mixture was further aged for 5 hours to complete the polymerization, and the resin particle dispersion (liquid dispersion) was recovered to obtain a resin particle dispersion (liquid dispersion) (particles 16). The content of the vinyl acetate monomer was 44.8% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 20.7% by mass, based on the total polymer components. The average particle diameter of the resin particles was 115 nm.

[0082] (Production Example 17) A resin particle dispersion (dispersion) (particles 17) was obtained in the same manner as in Production Example 16, except that the amount of distilled water was 364.5 parts, the amount of vinyl acetate monomer was 60 parts, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the vinyl acetate monomer was 44.4% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 18.5% by mass, based on the total polymer components. The average particle diameter of the resin particles was 121 nm.

[0083] (Production Example 18) A resin particle dispersion (dispersion) (particles 18) was obtained in the same manner as in Production Example 16, except that the amount of distilled water was 349.5 parts, the amount of vinyl acetate monomer was 70 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the vinyl acetate monomer was 46.7% by mass, based on all polymer components constituting the resin particles, and the content of the surfactant component was 20.0% by mass, based on all polymer components. The average particle diameter of the resin particles was 119 nm.

[0084] Production Example 19 A resin particle dispersion (dispersion) (particles 19) was obtained using 349.5 parts of distilled water, 35 parts of cyclohexyl methacrylate monomer, and 35 parts of methacrylonitrile monomer, as surfactant components, 10 parts of an acetylene-based surfactant 1 [Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3], 10 parts of a polyethylene glycol-based surfactant [ADEKA Esthole OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. The content of the monomer was 50.3% by mass, and the content of the surfactant component was 18.9% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 102 nm.

[0085] (Production Example 20) A resin particle dispersion (dispersion liquid) (particles 20) was obtained using 349.5 parts of distilled water, 35 parts of cyclohexyl methacrylate monomer, and 35 parts of styrene monomer, as surfactant components: 15 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9), 5.0 parts of a silicone surfactant (KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0), and 10 parts of a crosslinker (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., TAIC). The content of the monomer was 48.2% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 33.1% by mass, based on the total polymer components. The resin particles had an average particle size of 75 nm.

[0086] (Production Example 21) A resin particle dispersion (dispersion liquid) (particles 21) was obtained using 349.5 parts of distilled water, 30 parts of cyclohexyl methacrylate monomer, and 20 parts of vinyl acetate monomer, as surfactant components: 10 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0], 10 parts of an acetylene surfactant 5 [Olfine PD-002W, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.3 to 0.5%, HLB value: 9 to 10], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., TAIC]. The content of the monomers was 45.2% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant components was 30.1% by mass, based on the total polymer components. The average particle size of the resin particles was 89 nm.

[0087] (Production Example 22) A resin particle dispersion (dispersion liquid) (particles 22) was obtained using 349.5 parts of distilled water, 20 parts of methacrylonitrile monomer, 20 parts of styrene monomer, and 20 parts of vinyl acetate monomer, as surfactant components: 20 parts of an acetylene surfactant 1 [Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., TAIC]. The content of the monomer was 50.5% by mass, based on the total polymer components constituting the resin particles, and the content of the surfactant component was 21.6% by mass, based on the total polymer components. The average particle diameter of the resin particles was 109 nm.

[0088] The resin particle dispersions obtained in Production Examples 1 to 22 were evaluated for wettability and dispersion stability after low-temperature storage using the following evaluation methods. The solid content of the resin particles in each of the resin particle dispersions (dispersions) obtained in Production Examples 1 to 22 was 35 to 40 mass %. The results are shown in Table 1 below.

[0089] [Method for evaluating wettability after low-temperature storage] Each of the resin particle dispersions (dispersions) obtained in Production Examples 1 to 22 above was filled into a glass vial, the lid was closed, and the vial was stored in an environment of -10°C for one month, and the wettability after low-temperature storage was evaluated according to the following evaluation criteria. To evaluate the wettability, 0.5 ml of each resin particle dispersion (dispersion) was dropped onto a glass plate with a dropper, and the state of the coating film spread with a cotton swab was visually inspected and evaluated according to the following evaluation criteria. <Evaluation criteria> A: No repellency or pinholes were observed in the coating film, and the coating film was in good condition. B: Repelling or pinholes were observed in part of the coating film. C: Repelling or pinholes were observed throughout the coating film.

[0090] <Method for Evaluating Dispersion Stability After Low-Temperature Storage> Each of the resin particle dispersions (dispersions) obtained in Production Examples 1 to 22 above was filled into a glass vial, the lid was closed, and the dispersion was stored in an environment at -10°C for 3 months. After leaving it in an environment at 25°C for 3 hours to return to room temperature, the top and bottom of the dispersion (ink) in the vial were checked for the presence of sediment or floating matter. The top and bottom of the dispersion were sampled with a dropper and spread on a glass slide, and the presence or absence of sediment or floating matter was confirmed visually using an optical microscope. Evaluation was performed according to the following evaluation criteria. Evaluation criteria: A: No sediment or floating matter was observed. B: A small amount of sediment or floating matter was observed. C: Multiple sediments or floating matter was observed.

[0091]

[0092]

[0046] Considering Table 1 above, it was found that Production Examples 1 to 22, which fall within the scope of the present disclosure, achieve a high degree of wettability and dispersion stability after low-temperature storage, and that acetylene-based surfactants and polyethylene glycol-based surfactants containing surfactant components with a water solubility of less than 10% in particular exhibit excellent wettability and dispersion stability after low-temperature storage. Furthermore, for reference, dispersions were prepared by mixing various surfactants to achieve solid contents similar to those of Production Examples 1 to 22 above, but it was confirmed that the wettability and dispersion stability after low-temperature storage were inferior to those of the resin particle dispersions of Production Examples 1 to 22 of the present disclosure.

[0093] [Examples 1 to 23 and Comparative Examples 1 to 9: Preparation of aqueous ink compositions for writing instruments] (Examples 1 to 22) Using each of the resin particle dispersions (particles 1 to 22) produced in Production Examples 1 to 22 above, aqueous ink compositions for writing instruments were prepared by a conventional method according to the formulation shown below (total amount 100% by mass). Ink composition: (total amount 100% by mass) 15.0% by mass of each resin particle dispersion (particles 1 to 22: solid content 50% by mass for each), colorant (carbon black MA100, manufactured by Mitsubishi Chemical Corporation), 5.4% by mass, pH adjuster (triethanolamine), 1.4% by mass, water-soluble organic solvent (propylene glycol), 15.0% by mass, ion-exchanged water, balance

[0094] (Example 23) Using the resin particle dispersion (particles 1) produced in Production Example 1 above and colored resin particles having the following composition as a colorant, aqueous ink compositions for writing instruments were prepared by a conventional method according to the formulation shown below (total amount 100% by mass): Ink composition: (total amount 100% by mass) Resin particle dispersion (particles 1: solid content 50% by mass) 15.0% by mass Colorant (colored resin particles having the following composition) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water Balance

[0095] (Production Example of Colored Resin Particles) A ​​2-liter flask was equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000 ml separatory funnel for introducing monomers, and set in a warm water bath. 329.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blemmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 20 parts of a polymerizable surfactant (ADEKA Corporation, ADEKA REASOAP SE-10N, ether sulfate), and 0.5 parts of ammonium persulfate were then charged, and the internal temperature was raised to 50°C while introducing nitrogen gas. Separately, a solution was prepared by mixing 55 parts of cyclohexyl methacrylate monomer and 35 parts of n-butyl methacrylate as another monomer with 40 parts of an oil-soluble dye (Savinyl Blue GLS, manufactured by Clariant) and 10 parts of a crosslinker (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., "TAIC"). This prepared solution was added from the separatory funnel to the flask maintained at a temperature of approximately 50°C over a period of 3 hours with stirring, and emulsion polymerization was carried out. The mixture was then aged for another 5 hours to terminate the polymerization, yielding a dispersion of colored resin microparticles for aqueous inks (Particle 1). The content of the cyclohexyl methacrylate monomer was 50.0% by mass, based on the total polymer components constituting the colored resin microparticles, and the content of the oil-soluble dye was 36.4% by mass, based on the total polymer components. The average particle diameter of the colored resin microparticles was 40 nm.

[0096] As Comparative Examples 1 to 9, ink compositions for writing instruments were prepared by mixing the acetylene-based surfactants 1 to 7, polyethylene glycol-based surfactants, and silicone-based surfactants described in the above Production Examples to achieve solid contents similar to those of Examples 1 to 23.

[0097] The resulting aqueous ink compositions for writing instruments (total amount 100% by mass) were evaluated for wettability and writability (rubbing) after low-temperature storage, and for dispersion stability after low-temperature storage, using the writing instruments having the following configurations and the following evaluation methods. The evaluation results for Examples 1 to 23 are shown in Table 2 below, and the evaluation results for Comparative Examples 1 to 9 are shown in Table 3 below.

[0098] (Writing implement: preparation of marking pen) Each of the above aqueous ink compositions was loaded into a marking pen (manufactured by Mitsubishi Pencil Co., Ltd., trade name: Propass Window PUS-102T, nib, thick: PE resin sintered core, thin: PET fiber core) to prepare a marking pen.

[0099] [Method for evaluating wettability (glass surface) after low-temperature storage] Each aqueous ink composition for a writing instrument was filled into a writing instrument having the above-described configuration, and writing was performed in a spiral on a glass plate. The degree of repelling of the written line was visually confirmed, and the wettability (glass surface) after low-temperature storage was evaluated according to the following evaluation criteria. Evaluation criteria: A: The ink was not repelled at all, resulting in a clear written line. B: Some repelling was observed. C: The ink was repelled significantly, resulting in chipping of the written line.

[0100] [Method for evaluating writing properties (smearing and bleeding) after low-temperature storage] Writing was performed in a spiral on PPC paper using the writing implement configured as described above, and the initial writing properties were evaluated according to the following evaluation criteria. Evaluation criteria: A: Writing was possible without any problems from the start of writing. B: Smearing or bleeding of more than 0 mm but less than 10 mm was observed from the start of writing. C: Smearing or bleeding of 10 mm or more was observed from the start of writing.

[0101] [Method for evaluating dispersion stability after low-temperature storage] Each aqueous ink composition for writing instruments was filled into a glass vial, the lid was closed, and the composition was stored in an environment at -10°C for 3 months. After leaving it in an environment at 25°C for 3 hours to return to room temperature, it was checked whether any sediment or floating matter was observed at the top and bottom of the dispersion in the vial. The top and bottom of the dispersion were sampled with a dropper and spread on a glass slide, and the presence or absence of sediment or floating matter was visually confirmed using an optical microscope, and evaluated according to the following evaluation criteria. Evaluation criteria: A: No sediment or floating matter was observed. B: Slight sediment or floating matter was observed. C: Multiple sediments or floating matter was observed.

[0102]

[0103]

[0104] Considering the results in Tables 2 and 3 above, it was confirmed that Examples 1 to 23, which fall within the scope of the present disclosure, do not adversely affect other ink formulation components and do not adversely affect excellent wettability and writability after low-temperature storage, compared to Comparative Examples 1 to 9, which fall outside the scope of the present disclosure. Furthermore, it was confirmed that, with regard to dispersion stability after low-temperature storage, no sediment or floating matter was observed, compared to the Comparative Examples. It was also confirmed that the writing instruments prepared above did not smear or bleed, had sufficient line density, and produced clear lines.

[0105] Example 24: Preparation of aqueous inkjet ink composition Using the resin particle dispersion (particles 1) produced in Production Example 1 above, aqueous inkjet ink compositions were prepared by a conventional method with the formulation shown below (total amount 100% by mass). Each of the obtained aqueous inkjet ink compositions was evaluated for dispersion stability after low-temperature storage in accordance with the evaluation method described above. In addition, each composition was filled into a cartridge of an inkjet device [inkjet printer (PM-3000C, manufactured by Epson)], and printed on a support (printing paper) made of copy paper, and the color development and storage stability were evaluated using the evaluation methods described below. The results are shown below.

[0106] Ink composition: (total amount 100% by mass) Resin particle dispersion (particle 1, solid content 50% by mass) 50.0% by mass Colorant (colored resin particles of Example 23) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water Balance

[0107] (Method for evaluating color development) The printed portion printed by the inkjet device was visually evaluated according to the following evaluation criteria. Evaluation criteria: A: The printed portion is vivid and has excellent color development. B: The printed portion is slightly dull and has slightly poor color development. C: The printed portion is significantly dull and has poor overall color development.

[0108] (Method for evaluating storage stability) The above aqueous inkjet ink composition was filled into a glass vial, the lid was closed, and the vial was stored in an environment of -10°C for 3 months. After leaving it in an environment of 25°C for 3 hours to return to room temperature, inkjet printing was performed using the ink after storage in the above-mentioned method to obtain printed paper. The color developability of the obtained printed paper was confirmed. The storage stability of the ink was evaluated according to the following evaluation criteria. The storage stability was judged visually by comparing the color developability with that of printed paper printed with the aqueous inkjet ink composition before storage (initial period). Evaluation criteria: A: The printed area is vivid and has excellent color developability. B: The printed area is slightly dull, and color developability is slightly poor. C: The printed area is significantly dull, and color developability is poor overall.

[0109] It was confirmed that the aqueous inkjet ink composition of Example 24 obtained above did not adversely affect other ink components, had excellent storage stability after low-temperature storage, and was excellent in color development.

[0110] The resin particle dispersion of the present disclosure can be suitably used in writing instrument inks (low-viscosity ballpoint pens, batting-type writing instruments and direct-ink writing instruments, gel ballpoint pens, batting-type felt-tip pens, valve-type felt-tip pens, and direct-ink felt-tip pens), as well as inkjet inks, cosmetics such as eyeliners and hair dyes.

Claims

1. A resin particle dispersion characterized in that resin particles encapsulating at least one surfactant component selected from the following Group A are dispersed in water: <Group A> acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants 2. The resin particle dispersion according to claim 1, wherein the resin particles encapsulating the surfactant component are composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group B: <Group B> acrylic monomer, styrene monomer, nitrile monomer, vinyl acetate monomer 3. The resin particle dispersion according to claim 1 or 2, wherein the acetylene surfactant and the polyethylene glycol surfactant have a water solubility of less than 10%.

4. A resin particle dispersion according to claim 1 or 2, characterized in that the acetylene-based surfactant has an HLB value of 13.5 or less, the polyethylene glycol-based surfactant has an HLB value of 10.0 or less, and the silicone-based surfactant has an HLB value of 10.0 or less.

5. A water-based ink composition for a writing instrument, comprising the resin particle dispersion according to claim 1 or 2.

Images