JP7328015B2 - Water-based ink composition for writing instruments - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aqueous ink composition for writing instruments containing colored resin particles encapsulating a pigment.

Conventionally, many attempts have been made to use pigment-encapsulated resin particles as coloring agents for inks for writing instruments.
Conventionally, pigment-encapsulated colored resin particles include those in which the coloring agent of an ink composition for writing instruments is composite particles of spherical resin particles and a pigment (see, for example, Patent Document 1), and resin particles. An ink composition for writing instruments containing coated pigments (see, for example, Patent Document 2) is known.

Further, as a method for producing colored resin particles containing a pigment, for example, a crude pigment or a pulverized crude pigment obtained by dry pulverizing a crude pigment, an alkali salt of a carboxyl group-containing acrylic resin, and water and/or an aqueous solvent are mixed. a first step, a second step of mechanically dispersing the mixture obtained in the first step, a third step of adding an acid to the dispersion obtained in the second step to precipitate a resin on the pigment, and the A method for producing a pigment composition (colored resin particles) comprising a fourth step of re-neutralizing the precipitate obtained in the third step by adding an alkali (see, for example, Patent Document 3) is known.

However, the coloring agent composed of colored resin particles encapsulating such a pigment often causes the pigment to come off in the writing instrument ink composition or during the use or storage of the writing instrument in which it is mounted. Ta. The dropped pigment causes problems such as clogging of the ink flow path and gradual deterioration of the writing feel.

Japanese Patent Application Laid-Open No. 63-218778 (Claims, Examples, etc.) Japanese Patent Application Laid-Open No. 2003-268287 (Claims, Examples, etc.) Japanese Patent Application Laid-Open No. 9-217019 (Claims, Examples, etc.)

In view of the above-mentioned problems of the prior art, the present invention is intended to solve the problems. By containing colored resin particles encapsulating a pigment that is less likely to fall off, the clogging of the ink flow path can be prevented. To provide a water-based ink composition for writing utensils which is free from odors and has good writing feel.

In view of the above-described conventional problems, the present inventors have conducted intensive research and found that the aqueous ink composition for writing instruments having the above-described objective can be obtained by containing a synergist (pigment derivative) in colored resin particles encapsulating a pigment. etc. can be obtained, and have completed the present invention.

That is, the water-based ink composition for writing instruments of the present invention is characterized by containing colored resin particles containing at least a pigment and a synergist.
The synergist/pigment mass ratio is preferably 0.01 to 0.2.
It is preferable that the resin component of the colored resin particles is urethane-based.

ADVANTAGE OF THE INVENTION According to this invention, the water-based ink composition for writing instruments which does not clog an ink flow path and has a favorable writing feeling is provided.

Embodiments of the present invention are described in detail below.
The water-based ink composition for writing instruments of the present invention is characterized by containing colored resin particles containing at least a pigment and a synergist.

<Pigment>
The type of pigment that can be used is not particularly limited, and any of inorganic and organic pigments commonly used in water-based ink compositions for writing instruments can be used.
Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, iron oxide, chromium oxide, and ultramarine blue.
Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, and nitroso pigments. A single species may be used, or two or more species may be used in combination.

The content of these pigments in the colored resin particles is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, particularly preferably 15 to 25% by mass.
If the content of the pigment is less than 5% by mass, the coloring power may be insufficient and the visibility of the drawn line may be reduced. Reproducibility may deteriorate.

<Synergist>
The synergist (pigment derivative) used in the present invention is used to make it easier for the pigment to enter the resin particles during the formation of the colored resin particles and to make it difficult for the pigments to fall out of the colored resin particles. It is a derivative with a structure similar to that of pigments, and is a compound that has a strong interaction with pigments. It also has a strong interaction with a dispersant, which is preferably used in the production of colored resin particles, and which will be described later.
By including at least a pigment and a synergist in the colored resin particles, the synergist has a structure similar to that of the pigment (common skeleton) and therefore adsorbs to the surface of the pigment, and the synergist is adsorbed to the resin of the colored resin particles. , the pigment can easily enter into the resin particles, and has the effect of making it difficult for the pigment to come off.
Such synergistic interaction is considered to be van der Waals force, and it is presumed that strong and practical adsorption can be achieved because it acts on the entire flat and wide surface of the dye skeleton. The synergist is usually used as a dispersing aid for pigments in a liquid medium, but in the present invention, the effect of the present invention can be exhibited for the first time by containing it together with the pigment in the colored resin particles to be formed. .

As a synergist that can be used, an optimum synergist can be used depending on the pigment to be used, and a commercially available synergist for pigment colors, specifically carbon black, yellow pigments, azo pigments, and phthalocyanine pigments is used. Commercially available products having an acidic functional group include Solsperse 5000 (phthalocyanine pigment derivative), Solsperse 12000 (phthalocyanine pigment derivative), Solsperse 22000 (azo pigment derivative) manufactured by Lubrizol Co., Ltd., and BYK Chemie Co., Ltd. BYK-SYNERGIST2100 (phthalocyanine pigment derivative) manufactured by Japan, BYK-SYNERGIST2105 (yellow pigment derivative), EFKA6745 (phthalocyanine pigment derivative) manufactured by BASF Japan, EFKA6750 (azo pigment derivative) manufactured by Dispersion Materials Laboratory Co., Ltd. Synergist Yello-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 with two The above may be used in combination.

The content of these synergists in the colored resin particles varies depending on the type of pigment used and the amount thereof used, and the pigments and synergists used are constant from the viewpoint of suitably exhibiting the effect of synergist inclusion and the effect of the present invention. and the mass ratio of synergist/pigment is preferably 0.01 to 0.2, more preferably 0.05 to 0.15. If the mass ratio of the synergist/pigment is less than 0.01, the effect of making it difficult for the pigment to fall off in the colored resin particles may be weakened. Agglomeration of the pigment in the particles may occur, resulting in poor writing quality.

<Colored resin particles>
The colored resin particles of the present invention can be composed of at least microcapsule pigments encapsulating the pigment and synergist described above. It can be produced by microencapsulation, specifically by encapsulation in a shell layer (shell body) composed of a wall film-forming substance (wall material).
Microencapsulation methods include, for example, an interfacial polymerization method, an interfacial polycondensation method, an in situ polymerization method, an in-liquid curing coating method, a phase separation method from an aqueous solution, a phase separation method from an organic solvent, a melting dispersion cooling method, an air A suspension coating method, a spray lining method, and the like can be mentioned.

Preferably, the resin component (shell component) constituting the microcapsules is preferably a thermosetting resin such as epoxy resin, urethane, urea, or urea urethane, particularly preferably, from the viewpoint of ease of production and quality. Urethane-based resins such as urethane, urea, and ureaurethane are preferable because they can increase the amount of components to be encapsulated, have few restrictions on the types of components to be encapsulated, and are excellent in redispersibility.
Urethane (polyurethane resin), urea (polyurea resin), and ureaurethane (polyurea resin/polyurethane resin) used to form the shell layer are formed by reacting an isocyanate component with an amine component or an alcohol component. . Further, the epoxy resin used for forming the shell layer is formed by reacting with a curing agent such as an amine component.

Isocyanate components that can be used include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and 3,3′. -dimethyldiphenyl-4,4'-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, transcyclohexane 1,4-diisocyanate, diphenyl ether diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, 2 ,6-diisocyanatocaproic acid, tetramethyl-m-xylylenediisocyanate, tetramethyl-p-xylylenediisocyanate, trimethylhexamethylene diisocyanate, triphenylmethanetriisocyanate, tris(isocyanatophenyl)thiophosphate, isocyanatoalkyl 2,6- diisocyanatocapronate, 1,6,11-undecanetriisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-hexamethylenetriisocyanate, bicycloheptanetriisocyanate and the like.
Further, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene 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, cyclohexylene-1,4-diisocyanate and other diisocyanates, 4,4′,4″-triphenylmethane triisocyanate, triisocyanate such as toluene-2,4,6-triisocyanate, tetraisocyanate such as 4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate, hexamethylene diisocyanate and trimethylolpropane adducts of 2,4-tolylene diisocyanate and trimethylolpropane, adducts of xylylene diisocyanate and trimethylolpropane, and isocyanate prepolymers such as adducts of tolylene diisocyanate and hexanetriol. These isocyanate components may be used alone or in combination.

Specific examples of usable amine components include ethylenediamine, hexamethylenediamine, diaminocyclohexane, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, diaminoethyl ether, and 1,4-diamino. Aliphatic compounds such as butane, pentamethylenediamine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylaminopropylamine, diaminopropylamine, diaminopropane, 2-methylpentamethylenediamine, and xylenediamine amine, m-phenylenediamine, triaminobenzene, 3,5-tolylenediamine, diaminodiphenylamine, diaminonaphthalene, t-butyltoluenediamine, diethyltoluenediamine, diaminophenol and the like. Among them, aromatic amines such as phenylenediamine, diaminophenol and triaminobenzene are preferred.

Specific examples of alcohol components that can be used include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, catechol, and resorcinol. and polyols having two or more hydroxyl groups such as hydroquinone. These alcohol components may be used alone or in combination. Moreover, you may mix and use an alcohol component and an amine component.

Examples of the formation of a urethane-based shell layer using these urethane, urea, or urea-urethane include: 1) At least one monomer component selected from urethane, urea, and urethane-urea, and a pigment component are dispersed, and the shell layer is formed by interfacial polymerization. or 2) an emulsification step of dispersing an oily component (oil phase) containing an isocyanate component in an aqueous solvent (aqueous phase) to prepare an emulsion, and an amine component and an alcohol component in the emulsion It can be formed by a production method including an interfacial polymerization step of adding at least one of the above and performing interfacial polymerization.

In the production method of 2) above, a solvent can be used in preparing the emulsion. For example, phenyl glycol, benzyl alcohol, ethylene glycol monobenzyl ether, ethyl acetate, alkylsulfonic acid phenyl ester, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, liquid xylene resin. etc. can be used. These may be used alone or in combination.
On the other hand, the aqueous phase used for emulsifying the oily phase may contain a protective colloid in advance. As the protective colloid, a water-soluble polymer can be used, and it can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers. Inclusion is particularly preferred.
The aqueous phase may also contain a surfactant. As the surfactant, an anionic or nonionic surfactant that does not react with the protective colloid to cause precipitation or aggregation can be appropriately selected and used. Preferred surfactants include sodium alkylbenzenesulfonate (eg, sodium lauryl sulfate), dioctyl sulfosuccinate sodium salt, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.
After the oily phase prepared as described above is added to the aqueous phase and emulsified using mechanical force, the temperature of the system is raised as necessary to cause interfacial polymerization at the interfaces of the oily droplets and form particles. be able to. At the same time or after the completion of the interfacial polymerization reaction, the solvent can be removed. Capsule particles are obtained by separating the particles from the aqueous phase, washing the particles after interfacial polymerization reaction and removing the solvent, and then drying the particles.

In addition, the epoxy resin used for forming the shell layer is formed by reacting with a curing agent such as an amine component, and is formed by interfacial polymerization using each of the microencapsulation methods described above. be able to.
Epoxy resins that can be used include epoxy resins having two or more epoxy groups in one molecule, and those that are commonly used without being limited by molecular weight, molecular structure, etc. can be used. For example, bisphenol A type epoxy resin such as bisphenol A diglycidyl ether type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, cresol novolak type epoxy resin, biphenyl type epoxy resin, aromatic epoxy resin, naphthalene type Polyfunctional epoxy resins, polycarboxylic acid glycidyl ether type epoxy resins, polycarboxylic acid glycidyl ester type epoxy resins, and cyclohexane derivatives such as cyclohexane polyether type epoxy resins and hydrogenated bisphenol A type epoxy resins are obtained by epoxidation. and alicyclic epoxy resins such as dicyclopentadiene type epoxy resins, which can be used alone or in combination of two or more.

In the present invention, it is preferable to use a dispersant together with the pigment and synergist when forming the colored resin particles.
Dispersants that can be used include, for example, Ajisper PB821, Ajisper PB822, Ajisper PB711 (all manufactured by Ajinomoto Fine-Techno Co., Inc.), Disparlon DA-705, Disparlon DA-325, Disparlon DA-725, and Disparlon DA-703. -50, DISPERBYK-111, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2020, DISPERBYK-2050, DISPERBYK-2150 (manufactured by BYK-Chemie Japan), EFKA4010, EFKA4009, EFKA 4015 , EFKA4047, EFKA4050, EFKA4055, EFKA4060, EFKA4080, EFKA4520 (manufactured by BASF Japan), TEGO Dispers 655, TEGO Dispers 685, TEGO Dispers 690 (manufactured by Evonik Japan), etc., and other dispersants commonly known as Commercially available products can also be used, and are not limited to the above examples.
The content of these dispersants in the colored resin particles varies depending on the type of pigment and synergist used. % by mass, more preferably 3 to 15% by mass.

In the present invention, by forming the shell layer by each of the forming means described above, colored resin particles comprising at least a pigment and a microcapsule pigment encapsulating a synergist can be obtained.
In the present invention, the content of at least the pigment and the synergist varies depending on the dispersibility, specific gravity, arbitrarily controlling the particle size, color development, etc., but the water phase component (water , PVA), oil phase component (solvent), etc., do not substantially remain when colored resin particles are produced. components, etc.) are adjusted and polymerized by adjusting the above-mentioned pigment, synergist, dispersant, and resin component (remainder) within a suitable range, thereby obtaining colored resin particles in which each component falls within the above predetermined preferable range. becomes.
In the present invention, the colored resin particles composed of microcapsule pigments encapsulating at least the above pigments and synergists have a predetermined average particle diameter, for example, an average particle diameter of 0.00, depending on the application of the writing instrument (ballpoint pen, marking pen). It can be adjusted to be 1 to 30 μm, preferably the range of 0.5 to 20 μm satisfies the practicality of each of the above applications.
In the present invention (including the examples described later), the "average particle size" is the value of the particle size (D50) at 50% cumulative volume of the particle size distribution calculated based on the volume measured by the laser diffraction method. be. Here, the average particle size can be measured by the laser diffraction method, for example, using a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd.

<Aqueous ink composition for writing instruments>
The water-based ink composition for writing instruments of the present invention is characterized by containing at least the colored resin particles having the above configuration, that is, the colored resin particles containing at least a pigment and a synergist. It is used as an ink composition for writing instruments such as marking pens.
In the present invention, the content of the colored resin particles having the above characteristics is preferably 3 to 24% by mass, more preferably 10 to 20% by mass, based on the total amount of the water-based ink composition for writing instruments. is desirable.
If the content of the colored resin particles is less than 3% by mass, the coloring power will be insufficient and the visibility of the drawn lines will be reduced. It is not preferable because it may lower the performance.

The water-based ink composition for writing instruments of the present invention contains, in addition to the colored resin particles having the above characteristics, at least a general-purpose coloring agent other than the colored resin particles having the above characteristics, and a water-soluble solvent.
Colorants that can be used include 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 voids inside the particles as white pigments, or , resin particles dyed with a basic dye (pseudo-pigment), etc., which are excellent in color development and dispersibility, can also be used in an appropriate amount.
Any of direct dyes, acid dyes, food dyes, and basic dyes can be used as water-soluble dyes in an appropriate amount within a range that does not impair the effects of the present invention.

Examples of water-soluble solvents that can be used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, and glycerin, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, which may be used alone or in combination. be able to. The content of the water-soluble solvent is desirably 5 to 40% by mass based on the total amount of the water-based ink composition for writing instruments.

The water-based ink composition for writing instruments of the present invention contains colored resin particles having the above characteristics, a colorant other than the colored resin particles, a water-soluble solvent, and the balance of water as a solvent (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), dispersants, lubricants, pH adjusters, rust inhibitors, antiseptics or antibacterial agents, thickeners, etc. be able to.

As dispersants that can be used, nonionic, anionic surfactants and water-soluble resins are used. A water-soluble polymer is preferably used.
The polymer dispersant is not particularly limited, and known ones can be used, and those obtained by known materials and methods can be used.
Examples of lubricants include nonionics such as polyhydric alcohol fatty acid esters, sugar higher fatty acid esters, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, and alkylsulfonic acid higher fatty acid amides, which are also used as surface treatment agents for pigments. Salts, anionic surfactants such as alkylallylsulfonates, derivatives of polyalkylene glycol, fluorine-based surfactants, and polyether-modified silicones can be used.

Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonic acid and phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. etc. Examples of rust preventives include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of antiseptics or antibacterial agents include phenol, sodium omadine, sodium benzoate, thiazoline compounds, and benzimidazole. system compounds and the like.
Examples of thickening agents include carboxymethyl cellulose (CMC) or salts thereof, fermented cellulose, crystalline cellulose, polysaccharides, and the like. Polysaccharides that can be used include, for example, 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, nigelan, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkasi gum, succinoglycan, locust bean gum, tara gum, etc. These may be used singly or in combination of two or more. In addition, if these commercial products are available, they can be used.

The water-based ink composition for writing instruments of the present invention is prepared by appropriately combining the colored resin particles having the above characteristics, the water-soluble solvent, and other components according to the application of the ink for writing instruments (for ballpoint pens, marking pens, etc.), The water-based ink composition for writing instruments can be prepared by stirring and mixing with a stirrer such as a homogenizer or a disper, and optionally removing coarse particles in the ink composition by filtration or centrifugation. .

The water-based ink composition for writing instruments of the present invention is mounted in ball-point pens, marking pens, and the like having pen tips such as ball-point pen tips, fiber tips, felt tips, and plastic tips.
The ball-point pen of the present invention contains the water-based ink composition for writing instruments having the composition described above in a ball-point pen ink container (refill), and has no compatibility with the water-based ink composition contained in the ink container, and , substances having a low specific gravity relative to the water-based ink composition, such as polybutene, silicone oil, mineral oil, etc., are accommodated as ink followers. It can be made by filling an aqueous ballpoint pen body with a ballpoint tip having a ball of 0.18 to 2.0 mm.
The structure of the ballpoint pen and the marking pen is not particularly limited. It may be a direct liquid type ballpoint pen or marking pen.

The pH (25° C.) of the water-based ink composition for writing instruments of the present invention is adjusted to 5 to 10 with a pH adjuster or the like from the viewpoints of usability, safety, stability of the ink itself, and compatibility with the ink container. It is preferably adjusted, more preferably 6 to 9.5.

In the water-based ink composition for writing instruments of the present invention having such a structure, the synergist is contained in the colored resin particles used, thereby increasing the affinity of the pigment for the resin and causing the pigment to fall off. Therefore, it is possible to obtain an aqueous ink composition for a writing instrument which makes it difficult to cause clogging in the ink flow path, and provides a good writing feel, and a writing instrument equipped with the same. As a result, the colored resin particles of the present invention can be suitably used as a coloring agent for use in water-based ink compositions for writing instruments. , the desired water-based ink composition for writing instruments can be obtained.

EXAMPLES Next, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples and the like. In addition, "parts" in the following production examples means "mass parts".
Next, the present invention will be described in more detail with Production Examples 1 to 8 of the colored resin particles used, Examples 1 to 4 of the water-based ink composition for writing instruments, and Comparative Examples 1 to 4. is not limited to
The average particle size (D50: μm) of the colored resin particles obtained in Production Examples 1 to 8 was measured using a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd. In addition, "parts" in Production Examples 1 to 4 below mean "parts by mass".

[Production Example 1: Colored resin particles 1]
As an oil phase solution, while heating 11.6 parts of ethylene glycol monobenzyl ether and 1.8 parts of a dispersant (DISPERBYK-111, manufactured by BYK-Chemie Japan) to 60°C, a pigment (carbon black, Cabot Mogul L , manufactured by Cabot) and 0.2 parts of synergist (phthalocyanine pigment derivative, Solsperse 5000, manufactured by Lubrizol) were added and sufficiently dispersed. Next, 9.0 parts by mass of a trimethylolpropane adduct of xylylene diisocyanate (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) was added as a prepolymer to prepare an oil phase solution.
As the aqueous phase solution, while heating 600 parts by mass of distilled water to 60° C., 15 parts by mass of polyvinyl alcohol (PVA-205, manufactured by Kuraray Co., Ltd.) as a dispersant is dissolved therein to prepare an aqueous phase solution. did.
The oil phase solution was added to the aqueous phase solution at 60° C., and the mixture was emulsified and mixed by stirring with a homogenizer for 6 hours to complete the polymerization.
The resulting dispersion was centrifuged to obtain colored resin particles. The average particle size (D50) of the colored resin particles was 2.1 μm. Incidentally, substantially no water, solvent, and PVA remain as particle components (the same applies to the following production examples).

[Production Example 2: Colored resin particles 2]
The pigment of Production Example 1 above was added to 2.0 parts of PV Fast Blue L6472 (manufactured by Clariant Japan), a dispersant to TEGO Dispers 685 (manufactured by Evonik Japan) to 1.0 parts, and a synergist to a phthalocyanine pigment derivative (Solsperse 12000, Colored Resin Particles 2 were obtained in the same manner as in Production Example 1 above, except that 0.2 parts of Lubrizol Co., Ltd.) was used.
The average particle size (D50) of the colored resin particles was 2.7 µm.

[Production Example 3: Colored resin particles 3]
Yellow 4G-PT VP2669 (manufactured by Clariant Japan Co., Ltd.) 2.5 parts of the pigment of Production Example 1, Ajisper 821 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 0.5 parts of the dispersant, a synergist azo pigment derivative (EFKA6750, Colored Resin Particles 3 were obtained in the same manner as in Production Example 1 above, except that 0.15 parts of BASF Japan Co., Ltd.) was used.
The average particle size (D50) of the colored resin particles was 3.2 μm.

[Production Example 4: Colored resin particles 4]
Novoperm Orange HL70 (manufactured by Clariant Japan) 2.0 parts of the pigment of Production Example 1, EFKA PX4340 (manufactured by BASF Japan) 0.4 parts of the dispersant, yellow pigment derivative (BYK-SYNERGIST 2105, synergist) BYK-Chemie Japan Co., Ltd.) was replaced with 0.14 parts, and colored resin particles 4 were obtained in the same manner as in Production Example 1 above.
The average particle size (D50) of the colored resin particles was 1.3 μm.

[Production Examples 5-8: Colored Resin Particles 5-8]
Colored resin particles 5 to 8 were obtained in the same manner as in Production Examples 1 to 4, except for the synergist in Production Examples 1 to 4 above. The average particle diameters (D50) of the colored resin particles 5 to 8 were 1.9 μm, 2.4 μm, 3.4 μm and 1.5 μm, respectively.

[Examples 1 to 4 and Comparative Examples 1 to 4]
Using each of the colored resin particles 1 to 8 of Production Examples 1 to 8, each water-based ink composition for writing instruments was prepared according to the composition shown in Table 1 below and the like by a conventional method.
For each aqueous ink composition for writing instruments obtained in Examples 1 to 4 and Comparative Examples 1 to 4, writing instruments (aqueous ballpoint pens and aqueous marking pens) were prepared by the following method, and the ink consumption was evaluated by the following method. Stability and writing feel were evaluated.
These results are shown in Table 1 below.

(Preparing water-based ballpoint pens; Examples 1 to 3, Comparative Examples 1 to 3)
Using the ink compositions of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, water-based ballpoint pens were produced. Specifically, using the shaft of a ballpoint pen [manufactured by Mitsubishi Pencil Co., Ltd., product name: Signo UM-151], a polypropylene ink storage tube with an inner diameter of 3.8 mm and a length of 113 mm and a ballpoint pen tip (holder: stainless steel, Ball: Cemented carbide ball, ball diameter 0.38 mm) and a refill consisting of a joint connecting the storage tube and the tip with each of the above inks, and the trailing end of the ink is filled with an ink follower made of polybutene, and centrifuged. Deaeration was performed by treatment (500 G, 5 minutes) to prepare water-based ball-point pens (5 each).

(Preparing a water-based marking pen; Example 4, Comparative Example 4)
Water-based marking pens were produced using the ink compositions of Example 4 and Comparative Example 4 obtained above. Specifically, a marking pen [manufactured by Mitsubishi Pencil Co., Ltd., trade name: PEM-SY] having a plastic tip as a writing part is used, and the built-in ink occlusion body is filled with each of the above inks, and a water-based marking pen ( 5 each) were produced.

<Method for evaluating stability of ink consumption; ballpoint pen>
In a mechanical writing test under the following writing conditions, spiral writing was performed until the end of the stroke, and evaluation was made according to the following evaluation criteria. Writing conditions: 100 gf, writing angle of 75 degrees, writing speed of 4.5 m/min
Evaluation criteria:
A: Writing was possible until all the ink was consumed, and the ink consumption was stable.
B: Variation in ink consumption was observed.
C: Remarkable reduction in ink consumption was observed.

<Method for evaluating stability of ink consumption; felt-tip pen>
In a mechanical writing test under the following writing conditions, spiral writing was performed until the end of the stroke, and evaluation was made according to the following evaluation criteria. Writing conditions: 50 gf, writing angle of 65 degrees, writing speed of 4.2 m/min
Evaluation criteria:
A: Writing was possible until all the ink was consumed, and the ink consumption was stable.
B: Variation in ink consumption was observed.
C: Remarkable reduction in ink consumption was observed.

<Evaluation method of writing feeling; ballpoint pen>
In a mechanical writing test under the following writing conditions, 400-meter spiral writing was performed, and changes in writing feel before and after writing were evaluated according to the following evaluation criteria. Writing conditions: 100 gf, writing angle of 75 degrees, writing speed of 4.5 m/min
Evaluation criteria:
A: There is no change in writing feeling.
B: The writing feeling was slightly deteriorated.
C: Remarkably reduced writing feel.

<Evaluation method of writing feeling; Marking pen>
In a mechanical writing test under the following writing conditions, 400-meter spiral writing was performed, and changes in writing feel before and after writing were evaluated according to the following evaluation criteria. Writing conditions: 50 gf, writing angle of 65 degrees, writing speed of 4.2 m/min
Evaluation criteria:
A: There is no change in writing feel.
B: The writing feeling was slightly deteriorated.
C: Remarkably reduced writing feel.

As is clear from the results in Table 1 above, the water-based ink compositions for writing instruments of Examples 1 to 4, which fall within the scope of the present invention, have higher ink consumption stability than Comparative Examples 1 to 4, which fall outside the scope of the present invention. , it was confirmed that a water-based ink composition for writing instruments with excellent writing feel and writing instruments (water-based ballpoint pens, marking pens) equipped with the same can be obtained.

A water-based ink composition for writing instruments suitable for water-based ballpoint pens, marking pens and the like can be obtained.

Claims (2)

A water-based ink composition for a writing instrument, comprising colored resin particles containing at least a pigment and a synergist , wherein the resin component of the colored resin particles is a urethane-based resin . 2. The water-based ink composition for writing instruments according to claim 1, wherein the mass ratio of synergist/pigment is 0.01 to 0.2.