JP7270973B2 - Aqueous ink composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-based ink composition, particularly to a water-based ink composition that can be suitably used as a water-based ink composition for a water-based ballpoint pen.

In recent years, not only white paper, but also water-based ballpoint pens that draw opaque handwriting on colored paper, black paper, photographs, fabrics, leather, etc. Are known. As such water-based ball-point pens, those using a water-based ink composition that contains a white pigment such as titanium oxide and has concealing properties are often used.

In Patent Document 1, by using a water-based ink composition containing a specific amount of titanium oxide, specific hollow resin particles, an aqueous-soluble organic solvent, a shear-thinning agent, and a phosphoric acid ester-based activator, It describes a water-based ballpoint pen that does not cause visible blurring or line skipping.
Patent Document 2 discloses a ballpoint pen capable of recording clear handwriting on dark colored paper, using ink containing a specific amount of titanium oxide and specific resin particles and having a solid content adjusted to a specific range with respect to the total amount of ink. It is
Patent Document 3 describes a water-based ink composition for a water-based ball-point pen, which contains titanium oxide, a color pigment, and alumina, and which does not stain the inner wall of the ink containing tube and allows the remaining amount of ink to be clearly visually recognized. there is
Patent Document 4 discloses a water-based white ink for ballpoint pens, which contains a white pigment, a plate-like talc, and a water-soluble resin, has good ink ejection, prevents the penetration of the white pigment into paper, and has a high concentration of handwriting. Pigmented inks are described.

When writing on black paper or the like, it is conceivable to increase the content of titanium oxide or aluminum oxide in the ink composition in order to increase the concealability.
However, the specific gravity of titanium oxide and aluminum oxide is high, and if the content is increased, they settle in the ink. In addition, due to the influence of titanium oxide and aluminum oxide, it may be difficult to obtain a desired color.
On the other hand, when the content of titanium oxide and aluminum oxide in the ink is lowered, the drying property and hiding property are deteriorated. If the drying property is improved by increasing the drying speed of the water-based ballpoint pen ink, it becomes impossible to ensure good writing property when the ink is left uncapped (cap off property).

JP 2009-185166 A Japanese Patent Application Laid-Open No. 2001-180177 JP 2016-124894 A Japanese Patent No. 3122781

The present invention has good drying property, good color development and hiding property of the coloring agent, can form a handwriting having an opaque beauty, has good writing property without blurring, etc., and is contradictory to drying property. An object of the present invention is to obtain a water-based ink composition which has good cap-off property, which is a characteristic of the ink, has good sedimentation stability of components in the ink, and has excellent storage stability.

The inventors of the present invention have made intensive studies to solve the above problems, and as a result, found that the above problems can be solved by an aqueous ink composition containing titanium oxide, aluminum oxide, and talc. Arrived. Specifically, it is as follows.
[1] An aqueous ink composition containing titanium oxide, aluminum oxide and talc.
[2] The water-based ink composition according to [1], which is for writing instruments.
[3] The water-based ink composition according to [1] or [2], wherein the total content of titanium oxide, aluminum oxide and talc is 10 to 40% by mass based on the total amount of the water-based ink composition.
[4] The water-based ink according to any one of [1] to [3], wherein the ratio (mass ratio) of the content of titanium oxide to the total content of aluminum oxide and talc satisfies the following formula (1): Composition.
Formula (1):
1/99≦titanium oxide content/(aluminum oxide content+talc content)≦5/1
[5] The water-based ink composition according to any one of [1] to [4], wherein the content of talc is 2 to 15% by mass based on the total amount of the water-based ink composition.

According to the present invention, it is possible to form a handwriting that has good drying property, good color development and hiding property of the coloring agent, and has an opaque beauty, has good writing property without blurring, etc., and is contrary to drying property. Provided is a water-based ink composition which has good cap-off property, which is a characteristic of the ink, has good sedimentation stability of components in the ink, and has excellent storage stability.

The water-based ink composition of the present invention contains titanium oxide, aluminum oxide, talc, and a water-based solvent. It may contain one or more selected from the group consisting of agents and dispersants. Furthermore, other components (one or more selected from the group consisting of pH adjusters, preservatives, antifungal agents, resins, etc.) other than these may be included. Each component contained in the water-based ink composition of the present invention is described below.

[Titanium oxide]
Titanium oxide exhibits a function as a white coloring agent and a function as a masking material. Its crystal structure is not particularly limited, and titanium oxide of various crystal structures such as rutile type and anatase type is used.
The average particle size of titanium oxide ( _D50 value measured by a laser diffraction particle size distribution meter) is not particularly limited, but it is from 0.1 to 0.1 in consideration of concealability, prevention of pen tip clogging and sedimentation, and cost. 5 μm is used. It is preferably 0.1 to 1 μm, more preferably 0.3 to 0.5 μm.
Titanium oxide may be used either untreated or surface-treated with a treating agent. Preferably, one surface-treated with a treating agent is used. Examples of the treating agent include aluminum hydroxide (hydrous aluminum oxide), aluminum oxide, zirconium oxide, silicon oxide, zinc oxide, phosphoric acid (salt), fatty acid (salt), polyol compound, amine compound, silicone compound, and the like. One or more compounds selected from the group may be mentioned.

Titanium oxide may be commercially available in the form of fine particles. A commercially available aqueous dispersion can also be used in order to increase dispersion efficiency.
Examples of titanium oxide include KRONOS KA-10, KA-15, KA-20, KA-30, KA-35, KA-80, KR-310, KR-380, KR-380-N, KR-460, KR-480, KR-270 (Titanium Kogyo brand name), TITONE SR-1, R-3L, R-5N, R-7E, R-21, R-24, R-25, R-32 , R-38l, R-42, R-45M, R-61N, R-62N, R-310, R-650, D-918, R-970, FTR-700, TCR-52, GTR-100, A -110, A-150, A-190, A-197 (trade names of Sakai Chemical Industry Co., Ltd.), TIPAQUE R-550, R-580, R-630, R-670, R-680, R-780 , R-780-2, R-820, R-830, R-930, R-980, PR-690, PF-691, PF-711, PF-736, PF-737, PF-742, PF-739 , PF-740, PC-3, S-305, CR-50, CR-50-2, CR-57, CR-58, CR-58-2, CR-Super70, CR-80, CR-85, CR -90, CR-90-2, CR-93, CR-97, A-100, A-220 (all product names manufactured by Ishihara Sangyo Co., Ltd.), TITANIX JR-300, JR-301, JR-403, JR- 405, JR-600A, JR-600E, JR-603, JR-605, JR-701, JR-800, JR-801, JR-805, JR-806, JR-906, JR, JRNC, JA-1, JA-C, JA-3, JA-4, JA-5 (the above are product names of Tayca), TA-100, TA-200, TA-300, TA-400, TR-600, TR-700, TR -840, TR-900 (manufactured by Fuji Titanium Industry Co., Ltd.), Ti-Pure R-700, R-706, R-900, R-901, R-902, R-931 (DuPont Japan)・At least one selected from the group consisting of (trade name, manufactured by Limited) and the like can be used.

[Aluminum oxide]
Aluminum oxide exhibits a function as a white colorant and a function as a masking material. The crystal form is not particularly limited, and may contain water of crystallization or the like. Usually, α-, β-, γ-types and the like are used. The shape of the aluminum oxide particles is not particularly limited. It does not have to have a uniform shape.
The average particle size of aluminum oxide ( _D50 value measured by a laser diffraction particle size distribution meter) is not particularly limited, but it is from 0.1 to 0.1 in consideration of concealability, prevention of pen tip clogging and sedimentation, and cost. 5 μm is used. It is preferably 0.1 to 3 μm. When scale-like aluminum oxide is used, its aspect ratio (average particle size/average thickness) should be more than 1, preferably 5 or more, more preferably 10 or more. Although the upper limit of the aspect ratio is not particularly limited, it is usually 80 or less, preferably 60 or less.
Aluminum oxide may be used either untreated or surface-treated with a treating agent. An untreated one is preferably used.

Commercially available products can be used as aluminum oxide. In addition, a commercially available aluminum oxide aqueous dispersion can be used in order to increase the dispersion efficiency.
As aluminum oxide, for example, Seraph YFA02025, YFA10030, YFA05025 (the above are trade names manufactured by Kinseimatec), Terraces BMM, BMF, BMN, BMP, BMI, BMM-B, BMF-B, BMN-B, BMP-B , BMI-B (both manufactured by Kawai Lime Industry Co., Ltd.) and the like.

[talc]
Talc exhibits a function as a white colorant and a function as a masking material. Talc is hydrous magnesium silicate, and is obtained by grinding talc or the like.
The average particle size of talc ( _D50 value measured by a laser diffraction particle size distribution meter) is not particularly limited, but it is 0.1 to 5 μm in consideration of concealability, prevention of pen tip clogging and sedimentation, and cost. are used. It is preferably 0.5 to 4 μm, more preferably 1 to 3 μm.
Talc is generally plate-shaped particles, and its aspect ratio (average particle size/average thickness) is 1 or more, preferably 5 or more, and more preferably 10 or more. Although the upper limit of the aspect ratio is not particularly limited, it is usually 10,000 or less, preferably 8,000 or less.
Talc may be used either untreated or surface-treated with a treating agent. An untreated one is preferably used.

A commercial item can be used as talc. For example, MAICRO ACE SG-95, SG-2000, P-2, P-3, P-4, P-6, P-8, NANO ACE D-1000, D-800, D-600 (Nippon Talc company's product names), P talc, PH talc, PS talc, TTK talc, TT talc, T talc, ST talc, Hilac, Microlite, Himicron HE5 (all product names of Takehara Chemical Industry Co., Ltd.), LMS- 100, LMS-200, LMS-300, LMS-3500, LMS-400, LMP-100, PKP-53, PKP-80, PKP-81 (manufactured by Fuji Talc Kogyo Co., Ltd.), JM-209, JM One or more selected from the group consisting of -309 (these are trade names manufactured by Asada Flour Milling Co., Ltd.) and the like can be used.

[Contents of titanium oxide, aluminum oxide and talc]
The contents of titanium oxide, aluminum oxide, and talc can be appropriately set according to the type, shape, size, etc. of each, and according to the desired properties.
The content of titanium oxide is not particularly limited, but can be, for example, in the range of 0.1 to 30% by mass, preferably 1 to 20% by mass, based on the total amount of the water-based ink composition. If the content is less than 0.1% by mass, problems may arise in terms of background concealability and color developability when writing on dark colored paper such as black paper. If the content exceeds 30% by mass, problems such as sedimentation of titanium oxide and fading of handwriting over time may occur.
The content of aluminum oxide is not particularly limited, but can be, for example, in the range of 0.1 to 30% by mass, preferably 1 to 20% by mass, based on the total amount of the water-based ink composition. If the content is less than 0.1% by mass, problems may arise in terms of base-concealability, color developability, ink fluidity, and ink handleability when writing on dark colored paper. If the content exceeds 30% by mass, problems may occur such as sedimentation of aluminum oxide over time, blurred handwriting, difference in whiteness before and after drying, ink fluidity and ink handleability. The present inventors have found that the above effects are obtained when aluminum oxide particles are contained in the water-based ink composition, and that the above effects cannot be obtained with aluminum oxide coating the surface of titanium oxide or the like. rice field.
The content of talc is not particularly limited, but can be, for example, in the range of 1 to 30% by mass, preferably 1 to 20% by mass, more preferably 3 to 15% by mass, based on the total amount of the water-based ink composition. If the content is less than 1% by mass, there may be problems in terms of drying speed, base concealability when writing on dark paper, color development, visibility of handwriting, ink fluidity, ink handling, cap-off properties, etc. There is If the content exceeds 30% by mass, problems may occur in terms of sedimentation of talc over time, blurred handwriting, ink fluidity and ink handleability.
The total content of titanium oxide, aluminum oxide and talc is not particularly limited, but is, for example, 5 to 50% by mass, preferably 10 to 40% by mass, more preferably 10 to 40% by mass, based on the total amount of the water-based ink composition. can range from 15 to 35 mass %. If the amount is outside the range of 5 to 50% by mass, problems may occur in terms of drying speed, color development, sedimentation stability, faint handwriting, ink fluidity/outflow, and the like.

The content ratio (mass ratio) of titanium oxide and aluminum oxide is not particularly limited. /70 to 90/10.
The ratio (mass ratio) of the content of titanium oxide to the total content of aluminum oxide and talc is not particularly limited, but the titanium oxide content/(aluminum oxide content + talc content) is For example, it can be in the range of 1/99 to 5/1, preferably 1/9 to 2/1, more preferably 1/5 to 1/1.
The present inventors presume that the whiteness, particle shape and specific gravity of talc give the water-based ink composition a good balance between drying properties, sedimentation stability and color development properties.

[Aqueous solvent]
As the aqueous solvent used in the aqueous ink composition of the present invention, water or a mixed solvent of water and a water-soluble organic solvent is used. When a resin emulsion or an aqueous dispersion is blended into the water-based ink composition, the water-based solvent derived from these is also blended into the water-based ink composition as a water-based solvent.
Water is not particularly limited as long as it can be used as an aqueous solvent for aqueous ink compositions. For example, water that does not contain a large amount of impurities, such as ion-exchanged water, distilled water, pure water, and tap water, is used.
The water-soluble organic solvent is not particularly limited as long as it can be used as a water-soluble organic solvent for water-based ink compositions. For example, lower alcohols such as ethanol, isopropanol and butanol; polyhydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, glycerin and trimethylolpropane; monoalkyl ethers of these polyhydric alcohols; At least one selected from the group consisting of monoalkyl ether acetates of these polyhydric alcohols is used. Preferably, ethylene glycol, propylene glycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether One or more selected from the group consisting of is used.

The content of the aqueous solvent may be set as appropriate, and may be, for example, in the range of 10 to 90% by mass, preferably 20 to 80% by mass, more preferably 30 to 70% by mass, relative to the total amount of the aqueous ink composition. can. If the content is less than 10% by mass, sedimentation of the components and blurring of handwriting may occur over time, and fluidity may be poor, resulting in poor handleability and poor ink flowability. If the content exceeds 90% by mass, the viscosity of the water-based ink composition becomes too low, making it difficult to control the flow of the water-based ink composition when it is used as a writing instrument, and the handwriting becomes too thin, resulting in good substrate hiding properties. There is a possibility that the aesthetic feeling may be deteriorated because the color developability cannot be obtained.

[Coloring agent]
The coloring agent is used to make the handwriting with the water-based ink composition of the present invention aesthetically pleasing and to have a desired color tone. The colorant has properties such as good writability without blurring, good drying property and cap-off property, good sedimentation stability of components in the ink, and excellent storage stability. can be incorporated into the aqueous ink composition.
The coloring agent is not particularly limited as long as it is used in water-based ink compositions, particularly water-based ink compositions for water-based ballpoint pens. One or more selected from the group consisting of inorganic pigments, organic pigments, dyes, colored resin spheres, etc., which exhibit any color tone can be used.
Examples of inorganic pigments include carbon black, red iron oxide, yellow iron oxide, ultramarine blue, Prussian blue, metal powders such as aluminum powder and bronze powder, fluorescent pigments, pearl pigments, and luster pigments. The above can be used.
Organic pigments and dyes include, for example, phthalocyanine-based, azo-based, quinacdrine-based, anthraquinone-based, dioxane-based, indigo-based, thioindigo-based, perinone-based, perylene-based, indolenone-based, and azomethine-based known coloring pigments. At least one selected from the group consisting of colored dyes/fluorescent dyes such as fluorescent pigments, anthraquinone-based dyes, methine-based dyes, carbonium-based dyes, and metal complex salt-based dyes can be used.
The colored resin spheres are spherical, amorphous, hollow, or flat resin spheres colored with one or more inorganic pigments, organic pigments, or dyes exhibiting any desired color tone. Examples of the resin material forming the colored resin spheres include polyethylene, polypropylene, vinyl chloride, polymethacrylate, benzoguanamine, melamine resin, and nylon.

The content of the coloring agent may be appropriately set so that the water-based ink composition has a desired color tone. can range from 0 to 15% by weight. If the content exceeds 40% by mass, the viscosity becomes too high, causing problems such as the outflow of the ink from the tip of the writing instrument (the ink does not flow out), the handleability of the ink, the sedimentation stability, the blurred handwriting, and the manufacturing cost. It could be a problem.

[Viscosity modifier (thickener)]
A viscosity modifier (thickener) may be included for viscosity adjustment and the like. The viscosity modifier (thickener) is not particularly limited as long as it is used in aqueous ink compositions, particularly aqueous ink compositions for aqueous ball-point pens. For example, polysaccharides such as xanthan gum, welan gum, succinoglycan (leozan), diutan gum, guar gum, locust bean gum and derivatives thereof and derivatives thereof, cellulose polymers, cross-linkable acrylic acid polymers, alkali-thickening acrylic At least one kind selected from the group consisting of based resins, urethane associative thickeners, N-vinylacetamide based resins, inorganic fine particles and the like can be used.
The content of the viscosity modifier (thickener) is appropriately set so that the aqueous ink composition has an appropriate viscosity according to the application. For example, it can be in the range of 0 to 20% by mass, preferably 0.1 to 10% by mass, based on the total amount of the water-based ink composition.

[Wetting agent]
A wetting agent may be included for adjusting dryness and the like. The wetting agent is not particularly limited as long as it is used in water-based ink compositions, particularly water-based ink compositions for water-based ballpoint pens. For example, glycerin, diglycerin, triglycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, glycols such as polypropylene glycol, sugars, ureas, derivatives thereof, etc. One or more selected from the group consisting of can be used.
The content of the humectant in the water-based ink composition is appropriately set so that the ink has desired properties such as drying properties. For example, it can be in the range of 0.1 to 30% by mass, preferably 1 to 20% by mass, based on the total amount of the water-based ink composition.

[lubricant]
A lubricant may be included to improve the slip of the water-based ballpoint pen. The lubricant is not particularly limited as long as it is used for water-based ink compositions, particularly water-based ink compositions for water-based ballpoint pens, and commercially available lubricants can be used. For example, Phosphanol series such as Phosphanol PE-510, ML-220, ML-200, RL-310 (the above are the product names of Toho Chemical Industry Co., Ltd.), Nikkor series such as Nikkor DDP-2 (Nikko Chemicals Co., Ltd.) product name), Plysurf series such as POE alkyl ether phosphate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), fatty acids such as sodium oleate, and the like.
The content of the lubricant in the aqueous ink composition is not particularly limited, but can be, for example, in the range of 0.1 to 10% by mass, preferably 0.1 to 5% by mass, relative to the total amount of the aqueous ink composition. .

[Dispersant]
A dispersant may be included for the purpose of stabilizing the dispersion of the contained titanium oxide, aluminum oxide, talc, and pigment contained as a coloring agent. The dispersant stabilizes the dispersed pigment to prevent sedimentation of the pigment, and at the same time functions as a vehicle/binder for forming a coating film of the water-based ink composition. The dispersant is not limited as long as it is used for water-based ink compositions, particularly water-based ink compositions for water-based ballpoint pens, and commercially available ones can be used. For example, styrene-(meth)acrylic resin (emulsion), styrene-maleic acid resin (emulsion), styrene-maleic acid ester resin (emulsion), (meth)acrylic resin (emulsion), (meth)acrylic acid One or more selected from the group consisting of ester-based resins (emulsions), cellulose-based compounds such as sodium carboxymethylcellulose, and the like can be used.
The content of the dispersant in the water-based ink composition is not particularly limited, but can be, for example, in the range of 0.1 to 30% by mass, preferably 1 to 10% by mass, based on the total amount of the water-based ink composition. If the content exceeds 30% by mass, the dispersant may act as a flocculant and cause pigment aggregation. If the content is less than 0.1% by mass, the pigment may not be sufficiently dispersed, resulting in pigment aggregation. If pigment aggregation is caused, the pigment may settle in the ink, and there is a possibility that the ink will flow out from the writing instrument.

[Other additives]
If necessary, other additives may be added to the aqueous ink composition of the present invention. Other additives are not limited as long as they are used in water-based ink compositions, particularly water-based ink compositions for water-based ballpoint pens.
For example, pH adjusters (alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide (aqueous solutions), triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine, triethylamine, and other amine compounds , ammonia (water), etc.), antiseptic/antifungal agents (benzisothiazoline antiseptic/antifungal agents, pentachlorophenol antiseptic/antifungal agents, cresol antiseptic/antifungal agents, propylene glycol antiseptic/antifungal agents, iodine antiseptic/antifungal agents Antiseptic and antifungal agents such as agents), antirust agents (benzotriazole, tolyltriazole, dicyclohexylammonium nitrate, etc.), surfactants, antifoaming agents, leveling agents, anticoagulants, ultraviolet absorbers, infrared absorbers, Antioxidants, non-thermochromic pigments, non-thermochromic dyes, fluorescent brighteners and the like can be used in appropriate amounts.

[Viscosity of aqueous ink composition]
The viscosity of the water-based ink composition may be set appropriately, for example, 1 to 100,000 mPa·s, preferably 100 to 20,000 mPa·s, more preferably 1,000 to 10,000 mPa·s (E-type rotational viscosity (for example, Toki Sangyo Co., Ltd., TVE viscometer, 3° R14 cone, 0.5 rpm)). If the viscosity of the water-based ink composition is less than 100 mPa·s, the outflow of the ink from the tip of the writing instrument (the water-based ink composition flows out excessively during writing, making it impossible to accurately form a handwriting), sedimentation stability, and the like. It could be a problem. If the viscosity of the water-based ink composition exceeds 50,000 mPa·s, the viscosity becomes too high, and the outflow of the ink from the tip of the writing instrument (the ink does not flow out), the handleability of the ink, the sedimentation stability, the blurred handwriting, This may pose a problem in terms of manufacturing cost and the like.

[Use]
The water-based ink composition of the present invention can be used for both writing instruments and printing. As a writing instrument, the pen tip is a ball or a fiber bundle, and the ink storage part is a storage tube or a core type writing instrument such as a marker, felt-tip pen, ballpoint pen, etc., regardless of whether it is a valve type or a non-valve type. can also be used. In particular, it is most suitable for water-based ballpoint pens.

When the water-based ink composition of the present invention is used to construct a water-based ball-point pen, a known ball-point pen member may be employed. For example, for the ink storage tube, a known material and size can be applied as they are. As the material of the ink storage tube, for example, a pipe made of synthetic resin such as polyethylene or polypropylene, or a pipe made of metal can be used. Also, for the ball-point pen tip, materials and structures similar to those used in known water-based ball-point pens can be employed.

[Method for preparing water-based ink composition]
The method for producing the water-based ink of the present invention is not particularly limited, and any known method for preparing a water-based ink composition can be used.
For example, all the components are put into a container, and the ink is dispersed by mixing and stirring with devices such as ball mills, bead mills, roll mills, Henschel mixers, homomixers, propeller stirrers, homogenizers, high-pressure homogenizers, kneaders, and dissolvers. can be prepared.
For example, an aqueous solvent, a dispersant, titanium oxide, aluminum oxide, talc, and a coloring agent are put into a container, mixed and stirred by the above-mentioned device to produce a dispersion, and then the rest of the components are added. Ink can be prepared by mixing and stirring.
For example, after preparing a dispersion containing titanium oxide, a dispersion containing aluminum oxide, a dispersion containing talc, and a dispersion containing a colorant, these dispersions are mixed, and the remaining components are added. Ink can be prepared by mixing and stirring.
In the preparation of the water-based ink composition, coarse particles, gas, and air bubbles may be removed by performing operations such as filtration, centrifugation, defoaming, and the like. Means such as heating, cooling, pressurization, depressurization, inert gas replacement, etc. may be employed during the preparation of the water-based ink composition. Furthermore, you may perform an aging process after ink preparation.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples. Unless otherwise specified, "%" means "% by mass" and "parts" means parts by mass.

[Water-based ink composition component]
The following components were prepared as components constituting the water-based ink composition.
(titanium oxide)
"KRONOS KR-380N (manufactured by Titan Kogyo Co., Ltd., aluminum oxide, silicon oxide, zinc oxide treatment, average particle size 0.3 μm)
(Aluminum oxide)
“Seraph YFA02050” (manufactured by Kinseimatec, plate-like, average particle size 2.0 μm, aspect ratio 45 to 55)
(talc)
“Talc SG-95” (Nippon Talc Co., Ltd., average particle size 2.5 μm)

(light calcium carbonate)
"Characteristic Light Calcium Carbonate" (manufactured by Maruo Calcium Co., Ltd.)
(silica)
“ACEMATT (registered trademark) HK400” (manufactured by EVONIK, average particle size 6.3 μm)
(coloring agent)
A dark brown coloring agent was prepared by mixing the following coloring agents.
"A3 Yellow" (manufactured by Dainichiseika Kogyo Co., Ltd.)
"HOSTAPERM (registered trademark) ORANGE GR" (manufactured by Clariant)
"CINQUASIA (registered trademark) PINK D 4450" (manufactured by BASF)
"Printex (registered trademark) G" (manufactured by Orion Engineered Carbons)
(Viscosity modifier)
"Primal (registered trademark) ASE-60" (manufactured by Rohm and Haas Japan)
(wetting agent)
"Purified glycerin" (manufactured by Shin Nippon Rika Co., Ltd.)
(dispersant)
"Joncryl (registered trademark) 683" (manufactured by BASF, styrene-acrylic resin emulsion)
"Hi-Loss-X1" (manufactured by Seiko PMC)

[Examples 1 to 7, Comparative Examples 1 to 6]
Using the above ingredients, aqueous ink compositions having the compositions shown in Table 1 were prepared by the following method.
Using the obtained water-based ink composition, a water-based ball-point pen was produced by the following method.
(Method for preparing water-based ink composition)
Ion-exchanged water and a coloring agent were added to a titanium oxide dispersant obtained by mixing water, titanium oxide and a dispersant, and the mixture was stirred with a dissolver stirrer for 5 minutes.
Then, a lubricant, aluminum oxide and talc were added and stirred for 15 minutes.
After adding a pH adjuster and a dispersant and stirring for 30 minutes, an associative thickener was added and stirring was continued for 60 minutes.
Finally, other ingredients such as a wetting agent are added, and ion-exchanged water is added so that the amount of the water-based ink composition is equivalent to 100 parts by mass, and the mixture is stirred for 10 minutes to prepare a water-based ink composition. bottom.
(Method for producing a water-based ballpoint pen)
The obtained water-based ink composition was filled in a polypropylene ink storage tube having a stainless steel ballpoint pen tip (ball: cemented carbide, 1 mm in diameter) attached to one end, and an ink backflow preventer (gelled polybutene) was filled. to prepare a ballpoint pen refill. Next, a ball-point pen refill was attached to the main body, a cap was attached, the air in the tube was removed by a centrifuge, and a tail plug was attached to obtain a water-based ball-point pen using each water-based ink composition.
Using these water-based ball-point pens, water-based ink compositions were evaluated as follows.
Using the water-based ink composition or water-based ball-point pen thus obtained, the following evaluations were carried out. The results are also shown in Table 1.

<Drying speed>
Each water-based ballpoint pen was used to write 36 letters (180 seconds) of 15 mm sides on a white paper in an atmosphere of 20±2° C. temperature and 65±5% humidity (constant temperature chamber). Five seconds after the final V was written, the art surface of the art paper was applied to the handwriting, and a weight of 50φ500g was placed on the written part and rubbed five times. After that, the art paper was removed, and the drying speed was evaluated by taking the drying time as the time when the V-shaped transfer disappeared.

<Cap off property>
Place each water-based ballpoint pen horizontally with the cap removed, and leave it for 6 hours in an atmosphere with a temperature of 20 ± 2 ° C and a humidity of 65 ± 5% (in a constant temperature bath). (Evaluation method for determining the number of circles written until the handwriting disappears and the handwriting returns to normal while the circle is drawn 10 times) was performed and evaluated according to the following evaluation criteria.
◎: All 10 circles can be written normally ○: Normal writing is possible after 2 circles △: Normal writing is possible after 5 circles ×: All 10 circles are blurry

<Sedimentation stability>
Each water-based ballpoint pen was attached to a centrifuge so that the pen tip faced the outside of the rotation circumference, and after rotating and performing a sedimentation acceleration test, the time when writing was not possible was determined as the number of accelerated days, and the sedimentation stability was evaluated. .
The number of promotion days is calculated by multiplying the following
"If the emulsion suspension product is allowed to stand still for one year, the gravity of the earth (1 x g) will be applied to the product for one year. Summing up the gravity for this one year yields the following formula.
1 (year) x 365 (days) x 24 (hours) x 1 (xg) = 8,760 (xg) x 1 (hours)
That is, a gravitational effect equivalent to one year can be obtained by centrifuging at a centrifugal force of 8,760×g for one hour (or at a centrifugal force of 52,560×g for 10 minutes). ”
was calculated with reference to
When "H-38F" (manufactured by Kokusan; centrifugal radius 20 mm) is used as a centrifuge, centrifugation at 2,000 rpm for 1 minute corresponds to standing upside down for about 0.62 days.
After centrifugation at 2,000 rpm for an arbitrary time using a centrifuge "H-38F", a written test is performed, and further centrifugation at 2,000 rpm for an arbitrary time, written test, centrifugation at 2,000 rpm for an arbitrary time, written test. , and centrifugation and testing were repeated.
In the written test, 10 circles of 15 mm in diameter were written by hand. Ten circles were evaluated. ) was carried out, and the number of days converted to normal writing after 6 circles was derived.

<Beauty of handwriting>
For each water-based ballpoint pen, using a writing tester, a 20-m writing test was performed by continuously drawing circles on high-quality paper under the following conditions: writing angle: 65°, load: 100 gf, writing speed: 7 cm/sec, rotation: yes. , the number of bloats (ink lumps on the ball of the pen tip that were not transferred to the paper and accumulated on the pen tip attached to the paper) were visually counted and evaluated according to the following criteria.
Evaluation 5: 5 or less bots Evaluation 4: 6-10 bots Evaluation 3: 11-15 bots Evaluation 2: 16-20 bots Evaluation 1: 21 or more bots

<Double line of handwriting>
For each water-based ballpoint pen, using a writing tester, a 20-m writing test was performed by continuously drawing circles on high-quality paper under the following conditions: writing angle: 65°, load: 100 gf, writing speed: 7 cm/sec, rotation: yes. , fading and double lines were evaluated according to the following evaluation criteria.
Evaluation 5: No double lines Evaluation 4: Fewer double lines at the beginning and end of writing, double lines occurring on one side of the overlapping portion of the circles Evaluation 3: Less double lines at the beginning and end of the writing, both sides of the overlapping portion of the circles Double lines occur Evaluation 2: Writing double lines Evaluation 1: Double lines all the way

<Colorimetry>
Using a bar coater, RDS No. 9 (20.6 μm) and speed 3 (2.5±0.2 sec/30 cm).
Using a colorimeter (fluorescence spectral densitometer FD-5 (manufactured by Konica Minolta Japan), L*, a*, b* and chroma C of the handwriting were measured. A color difference ΔE from the handwriting of Comparative Example 7 was obtained.

<Concealability>
Each water-based ball-point pen was used to write on black drawing paper and a V-letter of 15 mm on each side was drawn on the black drawing paper.
○ = Color is not affected by black drawing paper △ = Color is slightly affected by black drawing paper × = Color is affected by black drawing paper

As is clear from the results of each example, the water-based ink composition of the present invention, which contains titanium oxide, aluminum oxide, and talc, has excellent drying speed, cap-off property, sedimentation stability, beautiful handwriting, and writability. Both (blurry, double lines) and hiding properties are exhibited in a well-balanced manner.
In contrast, the results of each comparative example reveal the following.
Comparative Example 1, which does not use talc, is particularly problematic in terms of drying speed.
Comparative Example 2, in which light calcium carbonate was used instead of talc, has particular problems in terms of drying speed, sedimentation stability and writability (blurry/double lines).
Comparative Example 3, in which silica was used instead of talc, had particular problems in terms of cap-off properties, sedimentation stability, aesthetics of handwriting, and writing properties (blurring and double lines).
Comparative Example 4, in which the amount of aluminum oxide was increased instead of talc, has particular problems in terms of sedimentation stability and writability (blurry/double lines).
Comparative Example 5, which does not use aluminum oxide, is particularly problematic in terms of drying rate.
Comparative Example 6, which does not use titanium oxide, has a particular problem in terms of concealability.
Comparative Example 7, which does not use talc, is particularly problematic in terms of drying speed and hiding power.

Claims (4)

containing titanium oxide, aluminum oxide and talc,
The content of titanium oxide is 1 to 20% by mass with respect to the total amount of the water-based ink composition,
The content of aluminum oxide is 1 to 20% by mass with respect to the total amount of the water-based ink composition,
The content of talc is 2 to 15% by mass with respect to the total amount of the water-based ink composition,
The mass ratio of titanium oxide to aluminum oxide is from 10/90 to 90/10 as titanium oxide/aluminum oxide.
Water-based ink composition. The water-based ink composition according to claim 1, which is used for writing instruments. 3. The water-based ink composition according to claim 1, wherein the total content of titanium oxide, aluminum oxide and talc is 10 to 40% by mass based on the total amount of the water-based ink composition. The water-based ink composition according to any one of claims 1 to 3, wherein the ratio (mass ratio) of the content of titanium oxide to the total content of aluminum oxide and talc satisfies the following formula (1).
Formula (1):
1/99≦titanium oxide content/(aluminum oxide content+talc content)≦5/1