Water-based ink composition for ballpoint pens

Abstract

To provide a water-based ink composition for a ballpoint pen which hardly causes corrosion of a pen tip even after a long-term storage and causes no blur upon starting to write.SOLUTION: There is provided a water-based ink composition for a ballpoint pen which comprises water, a coloring material and a cyclic peptide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous ink composition for a ballpoint pen. [Background technology]

[0002] Water-based ballpoint pens containing water-based ink are widely used, and it is required that such water-based ballpoint pens do not cause smearing of handwriting. To achieve this, polypeptides have been incorporated into water-based inks.

[0003] Patent Document 1 discloses a water-based ink for a ballpoint pen that contains at least water, a colorant, a polypeptide, and a resin emulsion.

[0004] Patent Document 2 discloses a water-based ink composition for a ballpoint pen that contains at least a colorant, water, a polymer having a structural unit represented by a specific general formula, and a polypeptide.

[0005] Patent Document 3 discloses an aqueous ink composition for ballpoint pens, which contains at least a silk polypeptide having an average molecular weight of 200 to 15,000, a colorant, a water-soluble organic solvent, and water.

[0006] Patent Document 4 discloses an aqueous ink composition for a ballpoint pen, which contains at least a polypeptide having an average molecular weight of 500 to 15,000 and containing 15 mol % or more of glutamic acid in its amino acid composition, a colorant, a water-soluble organic solvent, and water.

[0007] Incidentally, Patent Document 5 discloses various surfactin salts, which are a type of cyclic peptide. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-202706 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-235378 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-328248 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-316093 [Patent Document 5] International Publication No. 2014 / 142177 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a water-based ink composition for ballpoint pens which is resistant to corrosion of the pen tip even after long-term storage and does not cause smearing when starting to write. [Means for solving the problem]

[0010] The present inventors have conducted extensive research and found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows: <Aspect 1> An aqueous ink composition for a ballpoint pen, comprising water, a colorant, and a cyclic peptide. <Aspect 2> The aqueous ink composition for a ballpoint pen according to Aspect 1, wherein the cyclic peptide is a cyclic surfactin salt represented by the following formula (I): [ka] (wherein X represents an amino acid residue selected from leucine, isoleucine, and valine, R represents a C9-18 alkyl group, and M+ represents an alkali metal ion or a quaternary ammonium ion). Aspect 3: The aqueous ink composition for ballpoint pens according to Aspect 2, wherein the content of the cyclic peptide is 0.01 to 10% by mass based on the total mass of the aqueous ink composition for ballpoint pens. Aspect 4: The aqueous ink composition for a ballpoint pen according to any one of Aspects 1 to 3, further comprising 1 to 20% by mass of a water-soluble organic solvent. Aspect 5: The aqueous ink composition for a ballpoint pen according to Aspect 4, wherein the water-soluble organic solvent is at least one selected from the group consisting of aromatic compounds, alcohols, polyhydric alcohols, glycol ethers, hydrocarbons, and esters. <Aspect 6> The pen comprises at least an ink storage section, a writing section having a ball, and a holding section, The aqueous ink composition for a writing instrument according to any one of Aspects 1 to 5 is stored in the ink storage section. Ballpoint pen. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an aqueous ink composition for ballpoint pens that is resistant to corrosion of the pen tip even after long-term storage and does not cause smearing when starting to write. DETAILED DESCRIPTION OF THE INVENTION

[0012] <<Water-based ink composition for ballpoint pens>> The aqueous ink composition for a ballpoint pen of the present invention contains water, a colorant, and a cyclic peptide.

[0013] The present inventors have found that the above-mentioned configuration makes it possible to provide an aqueous ink composition for ballpoint pens that is resistant to corrosion of the pen tip even after long-term storage and that does not cause smearing when the ink starts to write. Without wishing to be bound by theory, this is thought to be because the amphiphilic nature of the peptide bond results in good affinity between the pigment and the solvent.

[0014] Furthermore, cyclic peptides have fewer functional groups available for reaction than non-cyclic peptides, making them more stable. As a result, cyclic peptides are less likely to react with the ball than non-cyclic peptides, which may further inhibit corrosion of the ball surface.

[0015] The aqueous ink composition for a writing instrument of the present invention does not contain an inorganic pigment, particularly a glittering inorganic pigment.

[0016] Each component of the present invention will be described below.

[0017] <water> As the water, ion-exchanged water, distilled water, etc. can be used.

[0018] The water content may be 50% by mass or more, 55% by mass or more, 60% by mass or more, 63% by mass or more, or 65% by mass or more, based on the total mass of the aqueous ink composition for ballpoint pens, and may be 90% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less.

[0019] <Coloring material> As the colorant, various colorants that can be used in conventional inks can be used, such as dyes, pigments, or mixtures of dyes and pigments, etc. These colorants can be used alone or in combination.

[0020] As the dye, any dye that dissolves or disperses in water can be used, including, for example, acid dyes such as eosin, fuoxin, water yellow #6-C, acid red, water blue #105, brilliant blue FCF, and nigrosine NB; direct dyes such as direct black 154, direct sky blue 5B, and violet BB; and basic dyes such as rhodamine and methyl violet.

[0021] Examples of pigments that can be used without limitation include conventionally known inorganic and organic pigments such as titanium oxide, resin particle pigments containing pigments or dyes, pseudopigments in which resin emulsions are colored with dyes or pigments, white plastic pigments, luster pigments, pigments in which silica or mica is used as a base material and the surface is multi-coated with iron oxide, titanium oxide, or the like, thermochromic pigments, photochromic particles, and the like.

[0022] Examples of inorganic pigments that can be used include carbon black, titanium black, zinc white, red iron oxide, aluminum, chromium oxide, iron black, cobalt blue, iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, yellow lead, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, baryte powder, calcium carbonate, white lead, dark blue, iron blue, manganese violet, aluminum powder, and brass powder.

[0023] Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, nitroso pigments, etc. Examples of such organic pigments include CI Pigment Blue 17, CI Pigment Blue 15, CI Pigment Blue 17, CI Pigment Blue 27, CI Pigment Red 5, CI Pigment Red 22, CI Pigment Red 38, CI Pigment Red 48, CI Pigment Red 49, CI Pigment Red 53, CI Pigment Red 57, CI Pigment Red 81, CI Pigment Red 104, CI Pigment Red 146, CI Pigment Red 245, CI Pigment Yellow 1, CI Pigment Yellow 3, CI Pigment Yellow 12 ... Examples of pigments that may be used include CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 17, CI Pigment Yellow 34, CI Pigment Yellow 55, CI Pigment Yellow 74, CI Pigment Yellow 95, CI Pigment Yellow 166, CI Pigment Yellow 167, CI Pigment Orange 5, CI Pigment Orange 13, CI Pigment Orange 16, CI Pigment Violet 1, CI Pigment Violet 3, CI Pigment Violet 19, CI Pigment Violet 23, CI Pigment Violet 50, and CI Pigment Green 7.

[0024] Examples of thermochromic pigments include those produced by microencapsulating a thermochromic composition containing at least a leuco dye that functions as a color former, a color developer that is a component capable of causing the leuco dye to develop color, and a color change temperature regulator that controls the color change temperature during color development of the leuco dye and the color developer, so as to have a predetermined average particle size (e.g., 0.1 to 6 μm). This average particle size may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 0.9 μm or more, or 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0025] Examples of photochromic particles that can be used include photochromic particles composed of at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, and a resin such as a terpene phenol resin. Examples of photochromic particles include photochromic particles produced by microencapsulating a photochromic composition containing at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, so as to have a predetermined average particle diameter (e.g., 0.1 to 6 μm).

[0026] By suitably using the above-mentioned photochromic substance, the photochromic particles can be made to have the property of being colorless in an indoor lighting environment (indoor lighting equipment selected from incandescent lamps, fluorescent lamps, lamps, white LEDs, etc.) and becoming colored in an ultraviolet irradiation environment (irradiation with wavelengths of 200 to 400 nm, or irradiation with sunlight containing ultraviolet rays).

[0027] In the present invention (including the examples), the "average particle size" is appropriately selected depending on the size of the particles to be measured. For particles less than approximately 1 μm, it is the histogram mean particle size (D50) calculated on a volume basis in the scattering intensity distribution measured by dynamic light scattering, and for particles 1 μm or larger, it is the median diameter (D50) calculated on a volume basis by laser diffraction. The average particle size can be measured using a particle size analyzer (Microtrac HRA9320-X100 (Nikkiso Co., Ltd.)).

[0028] Examples of methods for microencapsulating the thermochromic pigment and the photochromic particles include interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid hardening coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and can be appropriately selected depending on the application.

[0029] For example, in the phase separation method from an aqueous solution, a thermochromic microcapsule pigment can be produced by a method comprising the following steps, particularly a method comprising the following steps in this order: (1) Heating and melting the leuco dye, the color developer, and the color change temperature adjuster; (2) Adding the heated and melted leuco dye, developer, and discoloration temperature regulator to an emulsifier solution, and dispersing the mixture in the form of oil droplets by heating and stirring to prepare a dispersion; (3) A resin raw material capable of forming a wall film, such as a urethane resin, an epoxy resin, or an amino resin, is gradually added to the dispersion as a capsule film agent, specifically, an amino resin solution such as a methylolmelamine aqueous solution, a urea solution, or a benzoguanamine solution, and the resin raw material is reacted to form a capsule film, thereby obtaining a thermochromic microcapsule pigment; and (4) filtering the dispersion containing the thermochromic microencapsulated pigment;

[0030] In this thermochromic pigment, the color-developing temperature and decolorizing temperature of each color can be set to an appropriate temperature by appropriately combining the types and amounts of the leuco dye, color developer, and color-change temperature regulator.

[0031] These colorants can be used alone or in combination. The average particle diameter of water-dispersible pigments, resin particle pigments, pseudopigments, white plastic pigments, multi-coated pigments, thermochromic pigments, and photochromic particles varies depending on the ball diameter, ink composition, and viscosity, but is preferably 0.02 to 6 μm. This average particle diameter may be, for example, 0.02 μm or more, 0.05 μm or more, 0.07 μm or more, 0.10 μm or more, 0.20 μm or more, 0.30 μm or more, 0.50 μm or more, 0.70 μm or more, or 0.90 μm or more, or 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0032] The content of these coloring materials can be increased or decreased as appropriate depending on the line density of the ink, but may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, or 1.0% by mass or more, relative to the total amount of the ink composition, and is preferably 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0033] <Cyclic peptides> A cyclic peptide generally refers to a peptide having a cyclic structure.

[0034] As the cyclic peptide, for example, a cyclic surfactin salt represented by the following formula (I) can be used.

[0035] [ka]

[0036] In the formula, X represents an amino acid residue selected from leucine, isoleucine, and valine, R represents a C9-18 alkyl group, and M + represents an alkali metal ion or a quaternary ammonium ion.

[0037] For details of such a cyclic surfactin salt, reference can be made to Patent Document 5. Furthermore, as such a cyclic surfactin salt, a commercially available surfactin salt, for example, a surfactin salt commercially available from Kaneka Corporation, can be used.

[0038] The cyclic peptide content, based on the total mass of the aqueous ink composition for ballpoint pens, may be 0.01% by mass or more, 0.05% by mass or more, 0.10% by mass or more, 0.20% by mass or more, 0.30% by mass or more, 0.50% by mass or more, 0.70% by mass or more, 0.90% by mass or more, 1.00% by mass or more, 1.20% by mass or more, 1.50% by mass or more, 1.70% by mass or more, 2.0% by mass or more, 2.5% by mass or more, 3.0% by mass or more, or 3.5% by mass or more, and may be 10% by mass or less, 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, or 5% by mass or less.

[0039] <Water-soluble organic solvent> Examples of the water-soluble organic solvent that can be used include aromatics, alcohols, polyhydric alcohols, glycol ethers, hydrocarbons, esters, etc. These solvents may be used alone or in combination.

[0040] Examples of aromatic compounds that can be used include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkylsulfonic acid phenyl ester, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, and dipropylene glycol dibenzoate.

[0041] Examples of alcohols that can be used include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methylamyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, and 2-methylcyclohexanol.

[0042] Examples of polyhydric alcohols that can be used include ethylene glycol, diethylene glycol, 3-methyl-1,3 butanediol, triethylene glycol, dipropylene glycol, 1,3 propanediol, 1,3 butanediol, 1,5 pentanediol, hexylene glycol, and octylene glycol.

[0043] Examples of glycol ethers that can be used include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

[0044] As the hydrocarbons, for example, straight-chain hydrocarbons such as hexane, isohexane, heptane, octane, nonane, and decane, and cyclic hydrocarbons such as cyclohexane, methylcyclohexane, and ethylcyclohexane can be used.

[0045] Examples of esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, Examples of usable surfactants include methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic acid triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0046] The content of the water-soluble organic solvent may be 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, or 12% by mass or more, based on the total mass of the aqueous ink composition for ballpoint pens, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 17% by mass or less.

[0047] <Other ingredients> The aqueous ink composition for a writing instrument of the present invention may contain other optional components, such as dispersants, anti-rust agents, thickeners, preservatives or antibacterial agents, lubricants, pH adjusters, and adhesive resins.

[0048] The dispersant may be a nonionic surfactant, an anionic surfactant, or a water-soluble resin, and is preferably a water-soluble polymer.

[0049] As the lubricant, lubricants used in surface treatment agents for pigments can be used, and examples thereof include nonionic surfactants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters; anionic surfactants such as phosphate esters, alkyl sulfonates of higher fatty acid amides, and alkyl aryl sulfonates; derivatives of polyalkylene glycols; and polyether-modified silicones.

[0050] As the thickener, a known thickener can be used, specifically at least one selected from polysaccharides such as cellulose derivatives, crystalline cellulose, rheozan gum, gellan gum, xanthan gum, and succinoglycan; organic thickeners such as alkali-swelling association emulsions, alkali-swelling emulsions, polyvinylpyrrolidone, and cross-linked acrylic acid polymers; and inorganic thickeners such as montmorillonite clay minerals.

[0051] Examples of pH adjusters include ammonia, urea, amines such as monoethanolamine, diethanolamine, and triethanolamine, alkali metal salts of carbonate or phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and hydrates of alkali metal salts such as sodium hydroxide.

[0052] As the rust inhibitor, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponins, etc. can be used. As the antiseptic or antibacterial agent, phenol, sodium omadine, sodium benzoate, thiazoline compounds, benzimidazole compounds, etc. can be used.

[0053] The above-mentioned dispersants, lubricants, thickeners, pH adjusters, rust inhibitors, preservatives, antibacterial agents, and other components may be used alone or in combination of two or more. Furthermore, if commercially available, these products may also be used.

[0054] The fixing resin is a resin used as needed to adjust viscosity and improve fixing strength. For example, a water-soluble resin and a resin emulsion can be used as the fixing resin.

[0055] Examples of water-soluble resins that can be used include water-soluble resins having a hydrophobic portion in the molecule, such as polyacrylic acid, water-soluble styrene-acrylic resin, water-soluble styrene-maleic acid resin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resin, water-soluble styrene resin, water-soluble ester-acrylic resin, ethylene-maleic acid copolymer, polyethylene oxide, and water-soluble urethane resin.

[0056] As the resin emulsion, for example, at least one selected from polyolefin emulsion, acrylic emulsion, vinyl acetate emulsion, urethane emulsion, styrene-butadiene emulsion, styrene-acrylonitrile emulsion, and the like can be used.

[0057] The fixing resins may be used alone or in combination. In particular, from the viewpoint of fixing property, it is preferable to use one or more types of the above-mentioned water-soluble resins and resin emulsions, i.e., a total of two or more types of fixing resins.

[0058] Ballpoint pen The ballpoint pen of the present invention comprises at least an ink reservoir, a writing part having a ball, and a holding part, the ink storage section stores the aqueous ink composition for a writing instrument; It's a ballpoint pen.

[0059] By using the above-described aqueous ink composition for a writing instrument, it is possible to provide a ballpoint pen that is resistant to corrosion of the pen tip even when stored for a long period of time and that does not cause smearing when starting to write.

[0060] <Ink storage section> The ink reservoir stores the above-described aqueous ink composition for a writing instrument.

[0061] The ink storage section can be any type that can store ink and supply ink to the writing section, and it can be a direct ink type with a collector structure (ink retention mechanism) or a cotton-filled ballpoint pen.

[0062] <Writing Department> The writing part can be a writing part having a ballpoint pen tip at its tip.

[0063] A ballpoint pen tip may be composed of a ball and a holder that rotatably holds the ball. The ball may be composed of any material used for ballpoint pen balls, such as stainless steel, cemented carbide, ceramics, etc. The shape of the ballpoint pen tip is not particularly limited, and may be, for example, bullet-shaped or needle-shaped.

[0064] Furthermore, from the viewpoint of writing feel, it is desirable that the surface roughness Ra of the ball is less than 10 nm, and it is particularly preferable that the writing ball has a surface roughness Ra of 4 nm or less.

[0065] The "surface roughness Ra" in the present invention (including the examples described later) was measured using a non-contact surface profiler (NewView7200, Zygo) under the following conditions: lens magnification: 50x, evaluation length: 100 μm, Gaussian filter: 25 μm; and all other conditions were measured in accordance with JIS B0601 (geometric characteristics specifications of products - surface properties).

[0066] The water-based ballpoint pen of the present invention is less likely to corrode the pen tip when stored for a long period of time, and as a result, it is possible to suppress smearing when starting to write. Therefore, the water-based ballpoint pen of the present invention is particularly useful when using a ball with a small surface roughness. [Example]

[0067] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0068] <<Production of Water-Based Ink Composition for Ballpoint Pens>> Example 8 parts by mass of pigment (FUJI RED 2510), 6 parts by mass of pigment dispersant (Joncryl 61J, BASF JAPAN), 0.32 parts by mass of xanthan gum (KELSANS, Sansho Co., Ltd.) as a thickener, 4 parts by mass of cyclic polypeptide (Surfactin, Kaneka Corporation), preservative (Biodene 421, Nippon Soda Co., Ltd.), 1.4 parts by mass of triethanolamine as a pH adjuster, 15 parts by mass of propylene glycol as a water-soluble organic solvent, and the remainder, ion-exchanged water, were mixed to prepare 100 parts by mass of an aqueous ink composition for a ballpoint pen of this example.

[0069] Comparative Example 1 100 parts by mass of an aqueous ink composition for ballpoint pens of Comparative Example 1 was prepared in the same manner as in the Examples, except that the same mass of a non-cyclic polypeptide (Peptide PRA, Nippi Co., Ltd.) was used instead of the cyclic polypeptide.

[0070] Comparative Example 2 100 parts by mass of a water-based ink composition for a ballpoint pen of Comparative Example 2 was prepared in the same manner as in Example, except that the same mass of ion-exchanged water was used instead of the cyclic polypeptide.

[0071] "Making a ballpoint pen" Using the barrel of a ballpoint pen (Signo UM-151, Mitsubishi Pencil Co., Ltd.), each of the above inks was filled into a refill consisting of a polypropylene ink reservoir tube with an inner diameter of 3.8 mm and a length of 113 mm, a ballpoint pen tip (holder: stainless steel, ball: carbide ball, ball diameter: 0.7 mm), and a joint connecting the reservoir tube and the tip. An ink follower made of polybutene was filled into the rear end of the ink, and the ink was degassed by centrifugation (500 G, 5 minutes) to prepare water-based ballpoint pens (5 pens of each type).

[0072] "evaluation" <Corrosion test> After confirming that the prepared ballpoint pen was writable, it was left in a thermostatic chamber at 50°C and 80% humidity with the pen tip facing downward. After 3 months, the ballpoint pen was removed from the thermostatic chamber and left at room temperature for 1 day. Next, the appearance of the ball surface of the ballpoint pen left at room temperature for 1 day was visually observed using an optical microscope and evaluated according to the following evaluation criteria.

[0073] The evaluation criteria are as follows: A: It had a good metallic luster and no corrosion was observed. B: The metallic luster was weak and slight corrosion was observed. C: The metallic luster was weaker and some corrosion was observed. D: There was no metallic luster and corrosion was observed over the entire metal surface.

[0074] <Abrasion test> A mechanical writing test was conducted in which the pen was spirally written for 1000m (final stroke) under the conditions of a load of 100gf, a writing angle of 75 degrees, and a writing speed of 4.5mm / min.

[0075] The evaluation criteria are as follows: A: All five pens wrote smoothly to the end without any smudges. B: Although some of the pens had smudges, I was able to write with all five pens until the end. C: Significant wear, and all five pens became unusable.

[0076] Table 1 shows the configurations and evaluation results of the examples and comparative examples.

[0077] [Table 1]

[0078] It can be seen from Table 1 that the aqueous ink compositions for ballpoint pens of the examples containing cyclic peptides were good in all evaluation results.

Claims

1. An aqueous ink composition for a ballpoint pen, comprising water, a pigment, a thickener, and a cyclic peptide.

2. 2. The aqueous ink composition for a ballpoint pen according to claim 1, wherein the cyclic peptide is a cyclic surfactin salt represented by the following formula (I): 【Chemistry 1】 (wherein X represents an amino acid residue selected from leucine, isoleucine, and valine, R represents a C9-18 alkyl group, and M+ represents an alkali metal ion or a quaternary ammonium ion).

3. 3. The aqueous ink composition for ballpoint pens according to claim 2, wherein the content of the cyclic peptide is 0.01 to 10% by mass based on the total mass of the aqueous ink composition for ballpoint pens.

4. The aqueous ink composition for ballpoint pens according to any one of claims 1 to 3, further comprising 1 to 20% by mass of a water-soluble organic solvent.

5. 5. The aqueous ink composition for a ballpoint pen according to claim 4, wherein the water-soluble organic solvent is at least one selected from the group consisting of aromatic compounds, alcohols, polyhydric alcohols, glycol ethers, hydrocarbons, and esters.

6. 6. The aqueous ink composition for ballpoint pens according to claim 1, wherein the pigment has a D50 calculated on a volume basis of 0.02 to 6 μm.

7. The aqueous ink composition for ballpoint pens according to any one of claims 1 to 6, wherein the thickener is at least one selected from the group consisting of cellulose derivatives, crystalline cellulose, rheozan gum, gellan gum, xanthan gum, succinoglycan, alkali-swellable association emulsions, alkali-swellable emulsions, polyvinylpyrrolidone, cross-linked acrylic acid polymers, and montmorillonite-based clay minerals.

8. 8. The aqueous ink composition for ballpoint pens according to claim 1, wherein the content of the cyclic peptide is 2.5% by mass or more and 10% by mass or less, based on the total mass of the aqueous ink composition for ballpoint pens.

9. The pen comprises at least an ink reservoir, a writing part having a ball, and a holding part; The ink storage section stores the aqueous ink composition for a writing instrument according to any one of claims 1 to 8. Ballpoint pen.

10. 10. The ballpoint pen according to claim 9, wherein the ball has a surface roughness Ra of less than 10 nm.

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