Water-based ink composition for ballpoint pen

Abstract

Provided is an ink composition for a water-based ballpoint pen, which is excellent in pen wielding feeling without causing deterioration in pen wielding feeling or wear of a socket of a pen tip even when colored resin particles that encapsulate a pigment are used. A water-based ink composition for a ballpoint pen according to this embodiment, for example, contains at least colored resin particles (A) that encapsulate a pigment (a), and non-colored resin particles (B) that do not contain a pigment.

Description

[0001] This application is a divisional application of a Chinese patent application filed on October 21, 2020, with application number 202080074457.0 and invention name “Water-based ballpoint pen ink composition”. Technical Field

[0002] The present specification relates to an aqueous ballpoint pen ink composition using colored resin particles encapsulating a pigment. Background Art

[0003] It has long been known that there are: a water-based ink characterized by comprising (A) a hydrophilic polymer, (B) a hydrophobic polymer, and (C) an aqueous dispersion of pigment-encapsulated polymer particles containing a pigment and having a predetermined average particle size (see, for example, Patent Document 1); and an ink composition for writing instruments that uses a microcapsule pigment in which a dye or pigment is encapsulated in a microcapsule wall membrane (see, for example, Patent Document 2).

[0004] The microcapsule pigments encapsulating pigments described in Patent Documents 1 and 2 are obtained by encapsulating general dyes and general pigments whose particle size and particle distribution can be easily adjusted in a microcapsule wall membrane. However, when used in water-based ballpoint pens, the pen feel may be reduced and the socket of the pen tip may be worn.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-277507 (claims, examples, etc.)

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-150331 (claims, paragraph

[0006] , examples, etc.) Summary of the invention

[0009] Problem that the invention aims to solve

[0010] The present disclosure is made in view of the above-mentioned problems of the prior art and aims to overcome them, and its purpose is to provide a water-based ballpoint pen ink composition that has excellent writing feel without causing a decrease in writing feel or wear of the socket of the pen tip even when using colored resin particles encapsulating pigments.

[0011] Solutions for solving problems

[0012] The present inventors have conducted intensive studies in view of the above conventional problems and have found that the above-mentioned target water-based ballpoint pen ink composition can be obtained by containing at least colored resin particles encapsulating a pigment and colored resin particles having specific properties, thereby completing the present disclosure.

[0013] That is, the water-based ballpoint pen ink composition disclosed in the present invention is characterized by containing at least colored resin particles (A) encapsulating a pigment (a) and non-colored resin particles (B) containing no pigment.

[0014] Each resin component of the colored resin particles (A) and (non-colored resin particles (B)) is preferably a urethane-based resin.

[0015] The content ratio of the non-coloring resin particles (B) to the colored resin particles (A) [(B) / (A)] is preferably 0.05 to 1.0 on a mass basis.

[0016] The average particle diameter ratio of the non-coloring resin particles (B) to the colored resin particles (A) [(B) / (A)] is preferably 0.5 to 4.0.

[0017] Effects of the Invention

[0018] According to the present disclosure, it is possible to provide an aqueous ballpoint pen ink composition that provides excellent writing feel without causing a decrease in writing feel or wear of the socket of the pen tip even when using colored resin particles encapsulating a pigment.

[0019] In this specification, both the foregoing general description and the following detailed description are exemplary and explanatory and do not limit the present disclosure described in the claims. DETAILED DESCRIPTION

[0020] At least several embodiments of the present disclosure are described in detail below. However, the protection scope of the present disclosure is not limited to the embodiments described in detail below, but extends to the inventions described in the claims and their equivalents.

[0021] The water-based ballpoint pen ink composition disclosed herein is characterized by containing at least colored resin particles (A) encapsulating a pigment (a) and non-colored resin particles (B) containing no pigment.

[0022] <Pigment (a)>

[0023] In the present disclosure, the type of the pigment (a) encapsulated in the colored resin particles (A) is not particularly limited, and any of inorganic and organic pigments commonly used in aqueous ballpoint pen ink compositions and the like can be used.

[0024] Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, iron oxide, chromium oxide, and ultramarine blue.

[0025] In addition, examples of organic pigments include azo lakes, insoluble azo pigments, chelated azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, and nitroso pigments. These may be used alone or in combination of two or more.

[0026] The content of the pigment (a) encapsulated in the colored resin particles (A) is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and particularly preferably 15 to 25% by mass.

[0027] If the content of the pigment (a) is less than 5% by mass, the coloring power is insufficient and the visibility of the written and drawn lines may be reduced. On the other hand, if it exceeds 40% by mass, the amount of pigment becomes too large and the color reproducibility may be deteriorated.

[0028] <Colored resin particles (A)>

[0029] The colored resin particles (A) disclosed herein can be composed of a microencapsulated pigment encapsulating at least the above-mentioned pigment (a). For example, at least the above-mentioned pigment (a) is microencapsulated in a manner to have a predetermined particle size, specifically, encapsulated in a shell layer (shell) composed of a wall membrane forming substance (wall material), and can be produced.

[0030] Furthermore, the colored resin particles (A) of the present disclosure may be composed of a microcapsule pigment in which a synergist (pigment derivative) is encapsulated together with the above-mentioned pigment (a).

[0031] The synergist (pigment derivative) used is preferably used in order to facilitate the incorporation of the pigment (a) into the resin particles when forming the colored resin particles and to prevent the pigment (a) from falling off in the colored resin particles. It is a derivative having the same structure as the pigment (a) and is a compound that strongly interacts with the pigment (a). In addition, it also has a strong interaction with the dispersant described later that is preferably used when producing the colored resin particles.

[0032] The colored resin particles contain at least a synergist in addition to the pigment (a). Since the synergist has the same structure (common skeleton) as the pigment (a), it is adsorbed on the surface of the pigment. The synergist is adsorbed on the resin of the colored resin particles, thereby making it easy for the pigment (a) to enter the resin particles and not easy to fall off.

[0033] The interaction of the synergist is considered to be a van der Waals force, but it is presumed that since it acts on the entire flat and wide surface of the pigment skeleton, a strong and practical adsorption can be achieved. It should be noted that the synergist is usually used as a dispersion aid for the pigment in the liquid medium, but in the present disclosure, the synergist is contained in the formed colored resin particles together with the pigment (a), so that the effect of the present disclosure can be further exerted.

[0034] As the synergist that can be used, an optimal synergist can be used depending on the pigment (a) used. A commercially available synergist that is suitable for the color of the pigment (a), specifically, carbon black, yellow pigment, azo pigment, or phthalocyanine pigment can be used. Examples of the commercially available synergist that has an acidic functional group include Solsperse 5000 (phthalocyanine pigment derivative), Solsperse 12000 (phthalocyanine pigment derivative), and Solsperse 22000 (azo pigment derivative) manufactured by The Lubrizol Corporation, BYK-SYNERGIST 2100 (phthalocyanine pigment derivative), and BYK-SYNERGIST 2105 (yellow pigment derivative) manufactured by BYK-Chemie Japan KK, EFKA 6745 (phthalocyanine pigment derivative), and EFKA 6750 (azo pigment derivative) manufactured by BASF Japan Ltd., and Synergist 5000 (phthalocyanine pigment derivative), manufactured by Disper Material R&D Corp., and having an acidic functional group include Synergist 5000 (phthalocyanine pigment derivative), Solsperse 12000 (phthalocyanine pigment derivative), and Solsperse 22000 (azo pigment derivative) manufactured by The Lubrizol Corporation, and Synergist 5000 (phthalocyanine pigment derivative), manufactured by Disper Material R&D Corp., and having an acidic functional group include Synergist 5000 (phthalocyanine pigment derivative), manufactured by Disper Material R&D Corp., and ... Yellow-8020, 8404, 9043, 4827 (yellow pigment derivatives); Synergist Red-3953, 4327, 4474, 4858, 4966, 5507, 5525, 5909, 6006, 6547 (azo pigment derivatives); Synergist Blue-6831, 7215, 7438, 7854, 0785, 0785A (phthalocyanine pigment derivatives); Synergist Violet-6965, 7349, 7572, 7988 (phthalocyanine pigment derivatives), etc., and these may be used alone or in combination of two or more.

[0035] The content of these synergists in the colored resin particles is preferably changed according to the type of pigment used and its amount. From the perspective of the effect of the synergist and the effect of the present disclosure, the pigment and the synergist used are preferably mixed at a predetermined ratio, and the mass ratio of the synergist / pigment is preferably set to 0.01 to 0.2, and more preferably 0.05 to 0.15. By setting the mass ratio of the synergist / pigment to 0.01 or more, the pigment in the colored resin particles is not easily shed. On the other hand, by setting the mass ratio to 0.2 or less, the aggregation of the pigment in the colored resin particles is suppressed, and the reduction in the pen-handling feeling is suppressed.

[0036] The colored resin particles (A) of the present disclosure can be produced by microencapsulating a particle containing at least the above-mentioned pigment (a), or containing the above-mentioned pigment (a) and a synergist, so as to have a predetermined particle size.

[0037] Examples of the microencapsulation method include interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid solidification coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt dispersion cooling, air suspension coating, and spray drying.

[0038] Preferably, from the perspective of ease of production and quality, the resin component (shell component) constituting the microcapsule is preferably a thermosetting resin such as epoxy resin, carbamate, urea, or ureacarbamate. Carbamate resins such as carbamate, urea, or ureacarbamate are particularly preferred because they can increase the amount of encapsulated components, have fewer restrictions on the types of encapsulated components, and have excellent redispersibility.

[0039] The carbamate (polyurethane resin), urea (polyurea resin), and ureacarbamate (polyurea resin / polyurethane resin) used in the formation of the shell layer are formed by reacting an isocyanate component with an amine component or an alcohol component, etc. In addition, the epoxy resin used in the formation of the shell layer is formed by reacting with a curing agent such as an amine component.

[0040] Examples of the isocyanate component that can be used include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, polymerized diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethyldiphenyl-4,4′-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, trans-cyclohexane 1,4-diisocyanate, diphenyl ether diisocyanate, and xylylene diisocyanate. isocyanate, hydrogenated xylylene diisocyanate, 2,6-diisocyanate hexanoic acid, tetramethyl-m-xylylene diisocyanate, tetramethyl-p-xylylene diisocyanate, trimethylhexamethylene diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, isocyanate alkyl 2,6-diisocyanate hexanoate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanate methyl octane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, etc.

[0041] In addition, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-4,4-biphenyl-diisocyanate, 3,3'-dimethylphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, Ester, diisocyanate such as cyclohexylene-1,4-diisocyanate, triisocyanate such as 4,4',4"-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, tetraisocyanate such as 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, adduct of hexamethylene diisocyanate and trimethylolpropane, adduct of 2,4-toluene diisocyanate and trimethylolpropane, adduct of xylylenediisocyanate and trimethylolpropane, adduct of toluene diisocyanate and hexanetriol, and isocyanate prepolymers. These isocyanate components may be used alone or in combination.

[0042] Specific examples of the amine component that can be used include ethylenediamine, hexamethylenediamine, diaminocyclohexane, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, diaminoethyl ether, 1,4-diaminobutane, pentamethylenediamine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylaminopropylamine, diaminopropylamine, diaminopropane, 2-methylpentamethylenediamine, aliphatic amines such as xylene diamine, metaphenylenediamine, triaminobenzene, 3,5-toluenediamine, diaminodiphenylamine, diaminonaphthalene, tert-butyltoluenediamine, diethyltoluenediamine, diaminophenol, etc. Among them, aromatic amines such as phenylenediamine, diaminophenol, and triaminobenzene are preferred.

[0043] As the alcohol component that can be used, specifically, polyols having two or more hydroxyl groups such as ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerol, catechol, resorcinol, and hydroquinone can be cited. These alcohol components can be used alone or in combination. Furthermore, the alcohol component can be mixed with an amine component for use.

[0044] The shell layer of the carbamate system based on these carbamates, ureas, or urea carbamates is formed, for example, by 1) dispersing at least one monomer component of carbamate, urea, and carbamate urea with a pigment component to form a shell layer by interfacial polymerization; or, 2) forming the shell layer by a manufacturing method including the following steps: an emulsification step, which disperses an oily component (oily phase) containing an isocyanate component in an aqueous solvent (aqueous phase) to adjust an emulsion; and an interfacial polymerization step, which adds at least one of an amine component and an alcohol component to the emulsion to perform interfacial polymerization.

[0045] In the production method of 2) above, a solvent may be used when adjusting the emulsion. For example, benzyl glycol, benzyl alcohol, ethylene glycol monobenzyl ether, ethyl acetate, alkyl sulfonate phenyl ester, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, liquid xylene resin, etc. may be used. These may be used alone or in combination.

[0046] On the other hand, the aqueous phase used to emulsify the oily phase may contain a protective colloid in advance. As the protective colloid, a water-soluble polymer may be used, and it may be suitably selected from known anionic polymers, nonionic polymers, and amphoteric polymers, but it is particularly preferred to contain polyvinyl alcohol, gelatin, and a cellulose-based polymer compound.

[0047] In addition, the aqueous phase may contain a surfactant. As the surfactant, it is possible to appropriately select from anionic or nonionic surfactants that react with the protective colloid and do not cause precipitation or aggregation. Preferred surfactants include sodium alkylbenzene sulfonate (e.g., sodium lauryl sulfate), dioctyl sodium sulfosuccinate, polyalkylene glycol (e.g., polyoxyethylene nonylphenyl ether), and the like.

[0048] The oil phase prepared as above is added to the aqueous phase, and after emulsification by mechanical force, the temperature of the system is raised as needed to cause interfacial polymerization at the interface of the oil droplets, and granulation can be performed. In addition, at the same time or after the completion of the interfacial polymerization reaction, the solvent can be removed. Capsule particles can be obtained by separating the particles from the aqueous phase after the interfacial polymerization reaction and the solvent removal, washing, and then drying.

[0049] The epoxy resin used for forming the shell layer is formed by reacting with a curing agent such as an amine component, and can be formed by, for example, interfacial polymerization using the above-mentioned microencapsulation methods.

[0050] As the epoxy resin that can be used, there can be used: epoxy resins having two or more epoxy groups in one molecule, and generally used ones without limitation on molecular weight, molecular structure, etc., for example, bisphenol A type epoxy resins such as bisphenol A diglycidyl ether type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin and other aromatic epoxy resins, naphthalene type multifunctional epoxy resins, glycidyl ether type epoxy resins of polycarboxylic acids, homoglycidyl ester type epoxy resins, and cyclohexane polyether type epoxy resins, alicyclic epoxy resins obtained by epoxidation of cyclohexane derivatives such as hydrogenated bisphenol A type epoxy resin, and alicyclic epoxy resins such as dicyclopentadiene type epoxy resins. These can be used alone or in combination of two or more.

[0051] In the present disclosure, when the colored resin particles are formed, it is preferred to use a dispersant together with the pigment, or together with the pigment and a synergist.

[0052] Examples of dispersants that can be used include AJISPER PB821, AJISPER PB822, and AJISPER PB711 (all manufactured by Ajinomoto Fine-Techno Co., Inc.), DISPARLON DA-705, DISPARLON DA-325, DISPARLON DA-725, DISPARLON DA-703-50, and DISPARLON DA-234 (manufactured by Kusumoto Chemicals, Ltd.), DISPERBYK-111, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2020, DISPERBYK-2050, and DISPERBYK-2150 (manufactured by BYK-Chemie Japan KK), EFKA4010, EFKA4009, EFKA4015, EFKA4047, EFKA4050, EFKA4055, EFKA4060, EFKA4080, EFKA4520 (manufactured by BASF Japan Ltd.), TEGO Dispers 655, TEGO Dispers 685, TEGO Dispers 690 (manufactured by Evonik Japan Co., Ltd.), etc. In addition, as the dispersant, conventionally known and generally commercially available products can be used, without being limited to the above examples.

[0053] The content of these dispersants in the colored resin particles varies depending on the types of the pigment and synergist used, but is preferably 2 to 20% by mass, more preferably 3 to 15% by mass, from the viewpoint of synergistic action between the pigment and the synergist and appropriately exerting the effects of the present disclosure.

[0054] In the present disclosure, by forming the shell layer by the above-mentioned formation means, colored resin particles (A) containing microencapsulated pigments encapsulating at least the pigment (a) or colored resin particles (A) containing microencapsulated pigments encapsulating at least the pigment (a) and a synergist can be obtained.

[0055] In the present disclosure, at least the content of the pigment and the content of the synergist when used vary according to dispersibility, arbitrary control of specific gravity, aspects of particle size, color development, etc., and the above-mentioned aqueous phase components (water, PVA), oil phase components (solvents), etc. used in the production do not substantially remain when the colored resin particles are formed. Therefore, for each raw material (pigment, synergist, dispersant, resin component, etc.) used in the production of colored resin particles, by adjusting the above-mentioned pigment, synergist, dispersant, resin component (remainder) in an appropriate range and performing polymerization, etc., it is possible to obtain colored resin particles in which each component is within the above-specified preferred range.

[0056] In the present disclosure, the colored resin particles (A) composed of microcapsule pigments encapsulating at least the above-mentioned pigments can be adjusted to a predetermined average particle size, for example, an average particle size of 0.1 to 30 μm, according to the structure of a ballpoint pen, etc., and preferably in the range of 0.5 to 20 μm to meet the practicality of the above-mentioned structure.

[0057] In the present disclosure (including the embodiments described below), "average particle size" refers to the value of the particle size (D50) at the time of volume accumulation of 50% of the particle size distribution calculated on a volume basis by laser diffraction method. Here, the average particle size measurement based on the laser diffraction method can be performed using, for example, a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0058] <Non-coloring resin particles (B)>

[0059] The non-colored resin particles (B) disclosed herein are non-colored resin particles that do not contain a pigment. For example, when producing the above-mentioned colored resin particles (A), at least the components of the pigment, dispersant, and synergist are removed, and similarly, microencapsulation is performed in a manner to obtain a predetermined particle size, thereby producing the non-colored resin particles (B) that do not contain a pigment.

[0060] The uncolored resin particles (B) can be produced, for example, by removing the components of the pigment, dispersant, and synergist when producing the colored resin particles (A). The uncolored resin particles (B) can be produced by microencapsulating the particles to a predetermined particle size in the same manner as the colored resin particles (A) except that these components are not used.

[0061] As the resin component and the like used, the materials used in the above-mentioned colored resin particles (A) can be used, and therefore, descriptions of the materials and the production method are omitted.

[0062] <Water-based ballpoint pen ink composition>

[0063] The water-based ballpoint pen ink composition disclosed herein is characterized by containing at least the colored resin particles (A) encapsulating the pigment (a) and the non-colored resin particles (B) containing no pigment, and can be used as a water-based ballpoint pen ink composition, for example.

[0064] In the present disclosure, the content of the colored resin particles (A) having the above characteristics is preferably 5 to 25% by mass, more preferably 10 to 20% by mass, based on the total amount of the aqueous ballpoint pen ink composition.

[0065] If the content of the colored resin particles is less than 5% by mass, the coloring power is insufficient and the visual recognition of the written and drawn lines is reduced. On the other hand, if it exceeds 25% by mass, the viscosity becomes high and the fluidity of the ink may be reduced, which is not preferred.

[0066] In the present disclosure, from the viewpoint of further exerting the effects of the present disclosure, the content ratio [(B) / (A)] of the non-coloring resin particles (B) to the colored resin particles (A) is preferably 0.05 to 1.0, more preferably 0.05 to 0.5, based on mass.

[0067] From the perspective of further exerting the effects of the present disclosure and preventing the destabilization of the ink due to the separation of the colored resin particles (A) and the uncolored resin particles (B) over time, the ratio of the average particle diameters of the uncolored resin particles (B) and the colored resin particles (A) [(B) / (A)] is preferably 0.5 to 4.0, and more preferably 0.5 to 1.5.

[0068] The water-based ballpoint pen ink composition disclosed herein contains a water-soluble solvent in addition to the colored resin particles (A) and the non-colored resin particles (B). In addition, a general-purpose colorant other than the colored resin particles (A) may be contained as needed within a range that does not impair the effects of the present disclosure.

[0069] As the water-soluble solvent that can be used, for example, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerol, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether can be used alone or in combination. The content of the water-soluble solvent in the total amount of the aqueous ink composition for writing instruments is preferably 5 to 40% by mass.

[0070] As colorants that can be used, appropriate amounts of water-soluble dyes, pigments within a range that does not impair the effects of the present invention, such as inorganic pigments, organic pigments, plastic pigments, hollow resin particles having pores inside the particles as white pigments, or resin particles dyed with basic dyes having excellent color development and dispersibility (simulated pigments), etc. can also be used.

[0071] As the water-soluble dye, a direct dye, an acid dye, a food dye, and a basic dye may be used in an appropriate amount within a range not impairing the effects of the present disclosure.

[0072] The water-based ballpoint pen ink composition disclosed herein is characterized in that it contains at least: colored resin particles (A) encapsulating a pigment (a), and non-colored resin particles (B) not containing a pigment, and in addition to the colorant other than the above-mentioned colored resin particles and the water-soluble solvent, in addition to the remaining solvent, i.e., water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), a dispersant, a lubricant, a thickener, a pH adjuster, a rust inhibitor, a preservative or an antibacterial agent, etc., can be appropriately contained within a range that does not impair the effects of the present disclosure.

[0073] As the dispersant that can be used, nonionic or anionic surfactants and water-soluble resins are used, and preferably water-soluble polymers are used.

[0074] As lubricants that can be used, there are fatty acid esters of polyols, which can also be used as surface treatment agents for pigments, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, nonionic systems such as alkyl phosphates, anionic systems such as phosphates, alkyl sulfonates of higher fatty acid amides, alkyl allyl sulfonates, derivatives of polyalkylene glycol, polyether-modified silicones, and the like.

[0075] As the thickener that can be used, for example, it is desirable to be at least one selected from the group consisting of synthetic polymers, cellulose and polysaccharides. Specifically, gum arabic, tragacanth, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, welan gum, succinoglycan, diutan gum, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch glycolic acid and its salts, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylic acid and its salts, polyethylene oxide, copolymers of vinyl acetate and polyvinylpyrrolidone, styrene-acrylic acid copolymers and its salts, etc. can be cited.

[0076] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, sodium tripolyphosphate, alkali metal salts of carbonic acid and phosphoric acid such as sodium carbonate, hydrates of alkali metals such as sodium hydroxide, etc. In addition, examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylamine nitrite, saponins, etc., and examples of preservatives or antibacterial agents include phenol, sodium pyrithione, sodium benzoate, thiazoline compounds, benzimidazole compounds, etc.

[0077] Each component such as the above-mentioned dispersant, lubricant, thickener, pH adjuster, rust inhibitor, preservative or antibacterial agent may be used alone or in combination of two or more. In addition, any commercially available product thereof may be used.

[0078] The water-based ballpoint pen ink composition disclosed in the present invention can be prepared as follows: at least colored resin particles (A) encapsulating a pigment (a), non-colored resin particles (B) not containing a pigment, a water-soluble solvent, and other components are appropriately combined according to the purpose of the ballpoint pen ink, stirred and mixed using a stirrer such as a homomixer, a homogenizer, or a disperser, and then further filtered or centrifuged to remove coarse particles in the ink composition as needed, thereby preparing a water-based ballpoint pen ink composition.

[0079] The aqueous ballpoint pen ink composition disclosed herein can be produced without any particular change compared to the production method of other aqueous ink compositions.

[0080] That is, the water-based ballpoint pen ink composition of the present disclosure can be produced by mixing and stirring at least the colored resin particles (A) encapsulating the pigment (a), the non-colored resin particles (B) not containing the pigment, and the water-soluble solvent, and other components using a mixer, and further using, for example, a bead mill, a homomixer, a homogenizer, etc. that can exert strong shear, under appropriate stirring conditions, thereby producing the water-based ballpoint pen ink composition.

[0081] In addition, from the perspectives of usability, safety, stability of the ink itself, and compatibility with the ink container, the pH (25° C.) of the aqueous ballpoint pen ink composition of the present disclosure is preferably adjusted to 5 to 10 using a pH adjuster, and is more preferably set to 6 to 9.5.

[0082] The water-based ballpoint pen ink composition disclosed herein is mounted on a ballpoint pen having a pen tip such as a ballpoint pen nib.

[0083] As the water-based ballpoint pen in the present disclosure, there can be cited: for example, a water-based ballpoint pen ink composition of the above composition is contained in a ballpoint pen ink storage body (pen core) having a ball with a diameter of 0.18 to 2.0 mm, and a substance that is incompatible with the water-based ink composition contained in the ink storage body and has a smaller specific gravity than the water-based ink composition, such as polybutene, silicone oil, mineral oil, etc., is contained as an ink follower. As long as the ball has a diameter within the above range, the structure of the water-based ballpoint pen used is not particularly limited, and it is particularly desirable to process the water-based ballpoint pen with an ink storage tube filled with the above-mentioned water-based ink composition in a polypropylene tube and a pen core having a stainless steel pen tip (the ball is a super steel alloy) at the front end.

[0084] In addition, it can also be a straight liquid ballpoint pen with a collector structure (ink holding mechanism), wherein the collector structure uses the barrel itself as an ink storage body and fills the barrel with the water-based ballpoint pen ink composition of the above structure.

[0085] The water-based ballpoint pen ink composition of the present disclosure thus constituted is characterized in that it contains at least the aforementioned colored resin particles (A) and non-colored resin particles (B). When the colored resin particles encapsulating the pigment are used, there is a problem that the pigment falls off when the ink passes between the ball and the ball socket, causing a decrease in the writing feel and wear of the socket of the pen tip. However, by using the non-colored resin particles in combination, it is possible to play a role as a bearing agent (lubricating effect) between the ball and the ball socket, thereby providing a water-based ballpoint pen ink composition with excellent writing feel without causing a decrease in the writing feel or wear of the socket of the pen tip.

[0086] In addition, by including a synergist in the colored resin particles used, the affinity of the pigment to the resin is increased, the pigment is less likely to fall off, the ink flow path is not clogged, and the writing feel is good. An aqueous ink composition for writing instruments can be obtained.

[0087] Example

[0088] Next, the present disclosure will be described in further detail based on Production Examples 1 and 3 of the colored resin particles (A) used, Production Example 2 of the non-colored resin particles (B) used, Examples 1 to 5 of the water-based ballpoint pen ink composition, and Comparative Examples 1 to 2, but the present disclosure is not limited to the following Examples, etc. In addition, the average particle size (D50: μm) of the colored resin particles etc. obtained in Production Examples 1 to 3 was measured using a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0089] [Production Example 1: Production of Colored Resin Particles (A)-1]

[0090] While heating 11.6 parts of ethylene glycol monobenzyl ether and 1.8 parts of a dispersant (DISPERBYK-111, manufactured by BYK-Chemie Japan KK) as an oil phase solution to 60°C, 2.0 parts of a pigment (carbon black, Cabot Mogul L, manufactured by Cabot Corporation) and 0.2 parts of a synergist (phthalocyanine pigment derivative, Solsperse 5000, manufactured by The Lubrizol Corporation) were added and dispersed sufficiently. Then, 9.0 parts by mass of a trimethylolpropane adduct of xylylene diisocyanate (TAKENATE D110N, manufactured by Mitsui Chemicals, Inc.) as a prepolymer was added thereto to prepare an oil phase solution. While heating 600 parts by mass of distilled water as an aqueous phase solution to 60°C, 15 parts by mass of a polyvinyl alcohol (PVA-205, manufactured by Kuraray Co., Ltd.) as a dispersant was dissolved therein to prepare an aqueous phase solution.

[0091] The oil phase solution was added to the aqueous phase solution at 60°C and stirred for 6 hours with a homogenizer to perform emulsification and mixing, thereby completing polymerization. The obtained dispersion was centrifuged to obtain colored resin particles (A)-1. The average particle size (D50) of the colored resin particles (A)-1 was 2.1 μm.

[0092] [Production Example 2: Production of non-colored resin particles (B)]

[0093] While heating 11.6 parts of ethylene glycol monobenzyl ether as an oil phase solution to 60° C., 9.0 parts by mass of trimethylolpropane adduct of xylene diisocyanate (TAKENATE D110N, manufactured by Mitsui Chemicals, Inc.) as a prepolymer was added to prepare an oil phase solution. While heating 600 parts by mass of distilled water as an aqueous phase solution to 60° C., 15 parts by mass of polyvinyl alcohol (PVA-205, manufactured by Kuraray Co., Ltd.) as a dispersant was dissolved therein to prepare an aqueous phase solution.

[0094] The oil phase solution was added to the aqueous phase solution at 60°C and stirred for 6 hours with a homogenizer to perform emulsification and mixing to complete polymerization. The obtained dispersion was centrifuged to obtain colorless resin particles (B). The average particle size (D50) of the colorless resin particles (B) was 1.5 μm.

[0095] [Production Example 3: Production of other colored resin particles (A)-2]

[0096] Colored resin particles (A)-2 were obtained in the same manner as in the above-mentioned Production Example 1, except that the dispersant (DISPERBYK-111, manufactured by BYK-Chemie Japan KK) in the above-mentioned Production Example 1 was changed to 3.2 parts and the synergist (phthalocyanine pigment derivative, Solsperse 5000, manufactured by The Lubrizol Corporation) was not added. The average particle size (D50) of the colored resin particles (A)-2 was 2.7 μm.

[0097] [Examples 1 to 5 and Comparative Examples 1 to 2]

[0098] Using the colored resin particles (A) and the non-colored resin particles (B) of Production Examples 1 to 3, and in accordance with the blending compositions shown in Table 1 below, each water-based ballpoint pen ink composition was prepared by a conventional method.

[0099] The water-based ballpoint pen ink compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated for socket wear and pen handling feel by the following methods using ballpoint pens produced by the following method.

[0100] These results are shown in Table 1 below.

[0101] 〔Manufacturing of water-based ballpoint pens〕

[0102] The obtained ink compositions were used to prepare water-based ballpoint pens. Specifically, the shaft of a ballpoint pen (manufactured by Mitsubishi Pencil Co., Ltd., trade name: SIGNO UM-100) was used, and the above-mentioned water-based inks were filled into a pen core formed by a polypropylene ink storage tube with an inner diameter of 4.0 mm and a length of 113 mm, a stainless steel pen tip (superhard alloy ball, ball diameter 0.7 mm), and a joint connecting the storage tube and the pen tip, and an ink follower with mineral oil as the main component was loaded into the rear end of the ink to prepare the water-based ballpoint pen.

[0103] [Evaluation method of wear test (retainer wear)]

[0104] Using each of the water-based ballpoint pens obtained above, a mechanical writing test was performed to write in a spiral for 1000 m (pen movement was completed), and evaluation was performed according to the following evaluation criteria.

[0105] Writing conditions: 150gf, writing angle 80 degrees, writing speed 4.5mm / min

[0106] Evaluation criteria:

[0107] A: There is no problem at all in writing.

[0108] B: Although the writing is a little blurry, the writing can be continued until the end.

[0109] C: Visibly worn, and writing is completely impossible midway.

[0110] (Evaluation method of pen-handling feeling)

[0111] Each of the water-based ballpoint pens obtained above was used to write in a spiral for 300 m in the mechanical writing test used in the above evaluation, and the pen-handling feeling before and after writing was evaluated according to the following evaluation criteria.

[0112] Writing conditions: 150gf, writing angle 80 degrees, writing speed 4.5mm / min

[0113] Evaluation Benchmarks

[0114] A: The same pen-handling feeling.

[0115] B: The pen-handling feeling is slightly reduced.

[0116] C: The pen-handling feeling is significantly reduced.

[0117] [Table 1]

[0118]

[0119] As is clear from the results in Table 1 above, the aqueous ballpoint pen ink compositions of Examples 1 to 5 within the scope of the present disclosure were confirmed to be aqueous ballpoint pen ink compositions having excellent writing feel without causing a decrease in writing feel or wear of the socket of the pen tip even when using pigment-encapsulating colored resin particles, compared with Comparative Examples 1 to 2 outside the scope of the present disclosure.

[0120] Industrial Applicability

[0121] An aqueous ink composition suitable for aqueous ballpoint pens can be obtained.

Claims

1. A water-based ink composition for writing tools, characterized in that: The invention comprises at least: colored resin particles (A) encapsulating a pigment (a), and non-colored resin particles (B) containing no pigment, Each resin component of the colored resin particles (A) and the non-colored resin particles (B) not containing a pigment is a urethane resin.

2. The aqueous ink composition for writing instruments according to claim 1, characterized in that: The urethane resin is obtained from an isocyanate prepolymer.

3. The aqueous ink composition for writing instruments according to claim 2, characterized in that: The isocyanate prepolymer is at least one selected from the group consisting of an adduct of hexamethylene diisocyanate and trimethylolpropane, an adduct of 2,4-toluene diisocyanate and trimethylolpropane, an adduct of xylylene diisocyanate and trimethylolpropane, and an adduct of toluene diisocyanate and hexanetriol.

4. The aqueous ink composition for writing instruments according to claim 2, characterized in that: The isocyanate prepolymer is an addition product of xylylene diisocyanate and trimethylolpropane.

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