Aqueous ink composition for writing utensil, and writing utensil containing the same

Abstract

To provide an aqueous ink composition for a writing utensil, improved in the aseptic / fungus resistance performance by solubilizing 2-n-octyl-4-isothiazolin-3-one in the aqueous ink composition by adding polyether phosphoric ester, and not generating bleed through of handwriting formed on a writing surface such as a paper surface in writing, and to provide a writing utensil containing the same.SOLUTION: An aqueous ink composition for a writing utensil contains at least water, a coloring agent, 2-n-octyl-isothiazolin-3-one and polyether phosphoric ester and / or its salt. The HLB of the polyether phosphoric ester and / or its salt may be 5 or more and 20 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based ink composition for a writing instrument and a writing instrument containing the same, and more particularly to a water-based ink composition for a writing instrument having excellent antiseptic and antifungal properties and a writing instrument containing the same. [Background technology]

[0002] Conventionally, aqueous ink compositions, which contain water as their main component, are prone to the proliferation of microorganisms (e.g., fungi such as mold or yeast, bacteria, etc.). The proliferation of microorganisms in aqueous ink can cause the aqueous ink to spoil, resulting in the formation of precipitates or aggregates in the ink composition, discoloration of the ink composition, the emission of a putrid odor from the ink composition, and changes in the physical properties of the aqueous ink composition, such as a decrease or increase in viscosity, thereby impairing the functionality of the aqueous ink composition. To address this issue, a technology has been disclosed in which 2-n-octyl-4-isothiazolin-3-one is used as an antiseptic and antifungal agent in an aqueous ink composition containing a colorant, and a polyoxyalkylene alkyl ether with an HLB of 12 to 20 is further added as a solubilizer to solubilize the 2-n-octyl-4-isothiazolin-3-one (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-178924 Summary of the Invention [Problem to be solved by the invention]

[0004] The aqueous ink composition in the cited document uses polyoxyalkylene alkyl ether to solubilize 2-n-octyl-4-isothiazolin-3-one, thereby exhibiting excellent antiseptic and antifungal properties. However, the addition of polyoxyalkylene alkyl ether causes a problem in that the handwriting formed on the paper surface during writing tends to show through to the other side.

[0005] The present invention overcomes the above-mentioned drawbacks by solubilizing 2-n-octyl-4-isothiazolin-3-one in an aqueous ink composition, thereby improving the antiseptic and antifungal properties of the aqueous ink composition and providing an aqueous ink composition for a writing instrument that does not cause bleed-through of handwriting formed on a writing surface such as paper during writing, and a writing instrument containing the same.

[0006] In addition, in recent years, the Sustainable Development Goals (SDGs), consisting of 17 goals, 169 targets, and 232 indicators, have been proposed, calling for various initiatives across society both domestically and internationally. Of the 17 goals, Goal 12, "Responsible Consumption and Production," lists waste reduction and recycling as one of the challenges. The water-based ink composition for writing instruments of the present invention can inhibit ink spoilage and microbial growth, thereby enabling the reduction and recycling of waste such as ink and ink containers, and is believed to greatly contribute to the achievement of the goals set out in the SDGs, including Goal 12. [Means for solving the problem]

[0007] A first aspect of the present invention is an aqueous ink composition for a writing instrument, characterized by containing at least water, a colorant, 2-n-octyl-isothiazolin-3-one, and a polyether phosphate ester and / or a salt thereof.

[0008] Aspect 2 is the aqueous ink composition for a writing instrument of Aspect 1, characterized in that the polyether phosphate ester and / or salt thereof has an HLB of 5 or more and 20 or less.

[0009] Aspect 3 is a water-based ink composition for a writing instrument, characterized in that the water-based ink composition according to Aspect 1 or Aspect 2 further contains 4-chloro-3-methylphenol.

[0010] A fourth aspect is a writing instrument containing the aqueous ink composition for a writing instrument according to any one of the first to third aspects. [Effects of the Invention]

[0011] According to the present invention, by adding a polyether phosphate ester and / or a salt thereof to an aqueous ink composition, it is possible to solubilize 2-n-octyl-isothiazolin-3-one, thereby improving the antiseptic and antifungal properties of the aqueous ink composition, and to provide an aqueous ink composition for a writing instrument that does not cause bleed-through of handwriting formed on a writing surface such as paper during writing, and a writing instrument containing the same. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail. In this specification, "parts," "%," "ppm," and the like indicating the composition are based on mass unless otherwise specified.

[0013] The aqueous ink composition for a writing instrument of the present invention (hereinafter sometimes referred to as "aqueous ink composition" or "aqueous ink") contains at least water, a colorant, 2-n-octyl-isothiazolin-3-one (hereinafter sometimes referred to as "OIT"), and a polyether phosphate ester and / or a salt thereof.

[0014] <Water> The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, purified water, distilled water, ultrafiltered water, pure water, deep sea water, and groundwater.

[0015] <Coloring agent> The colorant may be selected appropriately from dyes, pigments, etc. without any particular limitations.

[0016] Specific examples of dyes include acid dyes, basic dyes, direct dyes, reactive dyes, vat dyes, sulfur dyes, metal-containing dyes, cationic dyes, food dyes, and disperse dyes. Examples of acid dyes include New Coccine (CI 16255), Tartrazine (CI 19140), Acid Blue Black 10B (CI 20470), Guinea Green (CI 42085), Brilliant Blue FCF (CI 42090), Acid Violet 6B (CI 42640), Soluble Blue (CI 42755), Naphthalene Green (CI 44025), Eosin (CI 45380), Phloxine (CI 45410), Erythrosine (CI 45430), Nigrosine (CI 50420), and Acid Flavin (CI 56205). Examples of basic dyes include chrysoidine (CI 11270), methyl violet FN (CI 42535), crystal violet (CI 42555), malachite green (CI 42000), Victoria blue FB (CI 44045), rhodamine B (CI 45170), acridine orange NS (CI 46005), methylene blue B (CI 52015), etc. Examples of direct dyes include Congo red (CI 22120), direct sky blue 5B (CI 24400), violet BB (CI 27905), direct deep black EX (CI 30235), Kayalas black G concentrate (CI 35225), direct fast black G (CI 35255), phthalocyanine blue (CI 74180), etc.

[0017] Examples of pigments include inorganic pigments, organic pigments, extender pigments, processed pigments, fluorescent pigments, luster pigments, phosphorescent pigments, and complementary color pigments. Specific examples of inorganic pigments include carbon black, graphite, titanium oxide, zinc oxide, iron black, yellow iron oxide, red iron oxide, composite oxide pigments, metal powders such as aluminum powder and bronze powder, iron blue, ultramarine, talc, mica, and kaolin. Specific examples of organic pigments include azo pigments, indigo pigments, phthalocyanine pigments, quinacridone pigments, thioindigo pigments, threne pigments, perinone pigments, perylene pigments, phthalone pigments, dioxane pigments, isoindolinone pigments, metal complex pigments, methine azomethine pigments, and diketopyrrolopyrrole pigments. Specific examples of fluorescent pigments include inorganic fluorescent pigments and organic fluorescent pigments. Specific examples of luster pigments include glass flake pigments, pearl pigments, and glitter pigments. Furthermore, as the pigment, thermochromic compositions, photochromic compositions, capsule pigments in which fragrances or the like are directly or microencapsulated, colored resin particles in which pigments are covered with transparent or translucent resin or the like, colorless resin particles colored with pigments or dyes, water-dispersed pigments dispersed using surfactants or the like, self-dispersed pigments, pigment dispersions in which pigments are dispersed in solvents, lake pigments insolubilized by adding metal salts to dyes, and the like can also be used. Examples of pigment dispersions in which a pigment is dispersed in a solvent include pigment dispersions in which a fluorescent pigment is dispersed in a solvent, and specific examples include the Shin-Roihi Color SW series, Shin-Roihi Color SF series (both manufactured by Shin-Roihi Co., Ltd.), and the Lumicol series (manufactured by Nippon Fluorescent Chemical Co., Ltd.).

[0018] These dyes and pigments may be used singly or in combination of two or more.

[0019] <Polyether phosphate esters and their salts> By adding polyether phosphate ester and its salt to water-based ink containing OIT, micelles with a structure that incorporates OIT at the center are formed, solubilizing OIT. By solubilizing OIT, the antiseptic and antifungal properties of OIT in water-based ink can be maximized. Furthermore, the action of the polyether phosphate ester and its salt moderately suppresses a decrease in the surface tension of the aqueous ink, thereby preventing strike-through when writing on a writing surface such as paper without excessively increasing the penetrability of the ink into the writing surface. "Strike-through" refers to the phenomenon in which ink penetrates to the reverse side of a writing surface such as paper, causing the reverse side to be colored.

[0020] Micelles are molecular aggregates or associations formed in aqueous or organic solvents. Micelles formed in aqueous solvents are composed of molecules or compounds with hydrophilic and hydrophobic regions, with the hydrophobic regions on the inside and the hydrophilic regions on the outside, forming a shell that incorporates hydrophobic substances. Micelles formed are known to have various structures, including spherical, rod-like, lamellar, string-like, and vesicle-like.

[0021] Solubilization refers to the state in which a hydrophobic substance that is insoluble or poorly soluble in an aqueous solvent is incorporated into the micelles of the solubilizer in a thermodynamically stable manner using a solubilizer, and dissolved in the aqueous solvent. In a solubilized solution, the micelles formed in the aqueous solvent have a particle size smaller than the wavelength of visible light, so the appearance is transparent. The polyether phosphate and / or its salt in the present invention acts as a solubilizing agent, and can solubilize OIT by forming micelles smaller than the wavelength of visible light.

[0022] The polyether phosphate ester and its salt of the present invention have a structure in which a phosphate group and a polyether group serve as a hydrophilic moiety, and a hydrophobic substituent is bonded to the terminal of the phosphate group or the polyether group as a hydrophobic moiety. From the viewpoint of excellent water solubility, resistance to dry-up, and dispersibility, the polyether group is preferably a polyoxyalkylene group.

[0023] The polyether phosphate ester having a polyoxyalkylene group is a compound represented by the following general formula (1).

[0024] [ka]

[0025] In general formula (1), R represents a hydrophobic portion, and A represents an alkylene group. n represents an integer of 1 or greater, and p and q represent that p+q=3, where p is an integer of 1 or greater and 3 or less, and q is an integer of 0 or greater and 2 or less. When there are multiple R and multiple A, they may be the same or different.

[0026] In general formula (1), the hydrophobic moiety represented by R represents any one of an alkyl group, an alkenyl group, and an aryl group. The number of carbon atoms in the alkyl group and the alkenyl group is preferably 3 to 24, more preferably 6 to 20, and even more preferably 10 to 18. When the number is equal to or greater than the lower limit, the performance of preventing strike-through onto a writing surface such as paper is superior. When the number is equal to or less than the upper limit, the dispersion stability is superior. Furthermore, the number of carbon atoms in the aryl group is preferably 6 to 24, more preferably 7 to 20. When the number is equal to or greater than the lower limit, the performance of preventing strike-through onto a writing surface such as paper is superior. When the number is equal to or less than the upper limit, the dispersion stability is superior.

[0027] In general formula (1), the alkyl group and alkenyl group represented by R may be linear, branched, or cyclic, and the number of double bonds in the alkenyl group is not particularly limited.

[0028] In the general formula (1), examples of the alkylene group represented by A include an ethylene group and a propylene group, with an ethylene group being more preferred in terms of superior hydrophilicity.

[0029] In general formula (1), n is preferably 1 or more and 30 or less, more preferably 1 or more and 20 or less, and even more preferably 2 or more and 20 or less, from the viewpoint of dispersion stability.

[0030] Salts of the polyether phosphate ester represented by general formula (1) can also be suitably used. Specific examples of polyether phosphate ester salts include metal salts such as sodium, calcium, and potassium salts, ammonium salts, and organic amine salts such as monoethanolamine salts.

[0031] Specific examples of the polyether phosphate ester represented by general formula (1) include monopolyoxyalkylene alkyl ether phosphate ester, dipolyoxyalkylene alkyl ether phosphate ester, tripolyoxyalkylene alkyl ether phosphate ester, monopolyoxyalkylene alkenyl ether phosphate ester, dipolyoxyalkylene alkenyl ether phosphate ester, tripolyoxyalkylene alkenyl ether phosphate ester, monopolyoxyalkylene aryl ether phosphate ester, dipolyoxyalkylene aryl ether phosphate ester, tripolyoxyalkylene aryl ether phosphate ester, monopolyoxyalkylene alkyl ether phosphate ester salt, dipolyoxyalkylene alkyl ether phosphate ester salt, monopolyoxyalkylene alkenyl ether phosphate ester salt, dipolyoxyalkylene alkenyl ether phosphate ester salt, monopolyoxyalkylene aryl ether phosphate ester salt, dipolyoxyalkylene aryl ether phosphate ester salt, and dipolyoxyalkylene aryl ether phosphate ester salt. Polyoxyethylene alkyl ether phosphate ester, tripolyoxyethylene alkyl ether phosphate ester, monopolyoxyethylene alkenyl ether phosphate ester, dipolyoxyethylene alkenyl ether phosphate ester, tripolyoxyethylene alkenyl ether phosphate ester, monopolyoxyethylene aryl ether phosphate ester, dipolyoxyethylene aryl ether phosphate ester, tripolyoxyethylene aryl ether phosphate ester, polyoxyethylene polyoxypropylene ether phosphate ester, monopolyoxyethylene alkyl ether phosphate ester salt, dipolyoxyethylene alkyl ether phosphate ester salt, monopolyoxyethylene alkenyl ether phosphate ester salt, dipolyoxyethylene alkenyl ether phosphate ester salt, monopolyoxyethylene aryl ether phosphate ester salt, dipolyoxyethylene aryl ether phosphate ester salt, polyoxyethylene polyoxypropylene ether phosphate ester salt are more preferred, and polyoxyethylene lauryl ether phosphate ester, polyoxyethylene alkyl(C12,More preferred are polyoxyethylene (C13) ether phosphate ester, polyoxyethylene alkyl (C12-C15) ether phosphate ester, polyoxyethylene alkyl (branched C13) ether phosphate ester, polyoxyethylene tridecyl ether phosphate ester, dipolyoxyethylene lauryl ether phosphate ester, dipolyoxyethylene alkyl (C12-C15) ether phosphate ester, polyoxyethylene oleyl ether phosphate ester, polyoxyethylene styrenated phenyl ether phosphate ester, polyoxyethylene alkenyl (C18) ether phosphate ester, polyoxystyryl phenyl ether phosphate ester, dipolyoxyethylene lauryl ether sodium phosphate, and polyoxyethylene aryl ether phosphate esters whose hydrophobic moiety has a phenol derivative. These polyether phosphates and / or salts thereof may be used alone or in combination of two or more. The content of the polyether phosphate ester and / or salt thereof is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass, relative to the total mass of the aqueous ink composition, in order to obtain better discharge stability when used in a marking pen.

[0032] The polyether phosphate ester and / or its salt may be appropriately synthesized, or a commercially available product such as the Plysurf series (manufactured by Daiichi Kogyo Co., Ltd.), the Phosphanol series (manufactured by Toho Chemical Industry Co., Ltd.), the NIKKOL series (manufactured by Nikko Chemicals Co., Ltd.), the Disparlon series (manufactured by Kusumoto Chemicals Co., Ltd.), and the Dispersogen series (manufactured by Clariant) may be used. Specifically, the Plysurf series includes Plysurf A212C, A215C, A208F, M208F, A208N, A208B, A219B, DB-01, A210D, A210B, and AL, while the Phosphanol series includes Phosphanol BH-650, ED-200, RA-600, ML-220, ML-240, RD-510Y, RS-410, RS-610, RS-710, RL-210, RL-310, RB-410, RD-710, LF-200, RM-410, RM-510, SP-212, and CP. -120, CP-720, SC-6103, RD-720, LP-700, LP-500, LB-400, PE-510, ED-200, etc., as the NIKKOL series, DOP-8NV, DLP-10, DDP-2, DDP-4, DDP-6, DDP-8, DDP-10, TLP-4, TCP-5, TOP-0V, TDP-2, TDP-6, TDP-8, TDP-10, etc., as the Disparlon series, Disparlon AQ-320, AQ-330, etc., as the Dispersogen series, Dispersogen LFH, etc. can be applied.

[0033] Polyether phosphate esters and their salts preferably have an HLB value of 5 or more and 20 or less, more preferably 6 or more and 18 or less, in order to be more effective in preventing bleed-through of handwriting written on a writing surface such as paper. HLB is an index showing the hydrophilic-lipophilic balance. A higher HLB value indicates greater hydrophilicity, and a lower HLB value indicates greater lipophilicity. The HLB value is a value calculated by the Griffin method, the Kawakami method, or the like.

[0034] 2-n-octyl-4-isothiazolin-3-one The water-based ink composition of the present invention is characterized by containing 2-n-octyl-4-isothiazolin-3-one (OIT), which is an isothiazolin compound having a highly hydrophobic octyl group.

[0035] Isothiazolin compounds are widely used industrially due to their excellent antiseptic and antifungal properties. In addition to OIT, which is used in the aqueous ink composition of the present invention, other known isothiazolin compounds include 1,2-methyl-isothiazolin-3-one (hereinafter sometimes referred to as "MIT"), 1,2-benzisothiazolin-3-one (hereinafter sometimes referred to as "BIT"), and 5-chloro-3-methyl-isothiazolin-3-one (hereinafter sometimes referred to as "CMIT"). Due to its excellent solubility in water, BIT is widely used not only in the field of writing instruments but also in aqueous systems. However, while BIT has a low minimum inhibitory concentration against bacteria, meaning that a small amount of additive can provide antiseptic and antifungal properties against bacteria, it has a high minimum inhibitory concentration against fungi (mold and yeast), meaning that a large amount is required to achieve antiseptic and antifungal properties against fungi.In addition, the high proportion of preservatives and antifungal agents in water-based inks can have an effect on the physical properties of the ink, such as increasing or decreasing the viscosity of the ink. The minimum inhibitory concentration of OIT against fungi is much lower than that of BIT, so preservative and antifungal properties can be obtained with a small amount added.In addition, by reducing the proportion of preservatives and antifungal agents in water-based inks, the impact on the physical properties of the ink can be reduced. The minimum inhibitory concentration is the minimum concentration required to inhibit the growth of fungi, bacteria, etc. If the minimum inhibitory concentration is low, antiseptic and antifungal properties can be obtained with a small amount added, but if it is high, a large amount must be added to achieve the desired effect. The minimum inhibitory concentration can be measured using a measurement method based on the standard method of the Japanese Society of Chemotherapy (broth microdilution method).

[0036] OIT, which contains a highly hydrophobic octyl group, was developed to improve solubility in non-aqueous materials such as plastics and building materials, thereby providing these materials with antiseptic and antifungal properties; however, it is a compound that is poorly soluble in aqueous solvents. In conventional aqueous ink compositions, the dissolution of OIT in aqueous solvents is insufficient, making it difficult to obtain sufficient antiseptic and antifungal properties. However, in the aqueous ink composition of the present invention, the addition of the polyether phosphate ester solubilizes OIT, thereby enabling the maximum antiseptic and antifungal properties to be exhibited in the aqueous ink.

[0037] The OIT content is preferably 1 ppm or more and 50,000 ppm or less, more preferably 1 ppm or more and 30,000 ppm or less, even more preferably 1.5 ppm or more and 10,000 ppm or less, and particularly preferably 1.5 ppm or more and 5,000 ppm or less, relative to the total mass of the aqueous ink composition. If the OIT content is above the lower limit, it is easier to obtain antiseptic and antifungal properties in the aqueous ink, and if it is below the upper limit, it is less likely to affect the physical properties of the aqueous ink.

[0038] <4-chloro-3-methylphenol> The aqueous ink composition of the present invention preferably further contains 4-chloro-3-methylphenol (hereinafter sometimes referred to as "PCMC"). In the present invention, the inclusion of PCMC as an antiseptic and antifungal agent significantly inhibits the growth of a wide variety of microorganisms. Furthermore, the addition of PCMC further improves the antiseptic and antifungal properties of tanks used in the production of aqueous ink, writing implement containers that store aqueous ink, and ink storage containers (ink cartridges) and other containers.

[0039] PCMC may be synthesized as appropriate or commercially available products may be used. The shape of the PCMC is not particularly limited, and may be crystalline, granular, flake, or the like. Furthermore, a solution of PCMC dissolved in an aqueous solvent, a dispersion of PCMC dispersed or emulsified in an aqueous solvent, or a solution of PCMC dissolved in an organic solvent such as ethanol or acetone may also be used.

[0040] The content rate of PCMC is preferably 1 ppm or more and 50,000 ppm or less, more preferably 1 ppm or more and 30,000 ppm or less, still more preferably 1 ppm or more and 10,000 ppm or less, and particularly preferably 1 ppm or more and 5,000 ppm or less, based on the total mass of the aqueous ink composition. When it is at least the lower limit value, it is easy to obtain the anti-corrosion and anti-mold performance in the aqueous ink and the container, and when it is at most the upper limit value, it is difficult to affect the physical properties of the aqueous ink.

[0041] <Other additives> In the ink composition according to the present invention, arbitrary additives can be used as needed for the purpose of improving the physical properties and functions of the aqueous ink. Examples of the additives include preservatives and fungicides other than OIT and PCMC, water-soluble organic solvents, resins, resin particles, rust inhibitors, wetting agents, defoaming agents, antioxidants, viscosity adjusters, specific gravity adjusters, shear-thinning property imparting agents, pH adjusters, pigment dispersants, chelating agents, bubble inhibitors, bubble absorbers, and the like.

[0042] <Preservatives and fungicides other than OIT and PCMC> The aqueous ink composition in the present invention may contain preservatives and fungicides other than OIT and PCMC for the purpose of further suppressing the growth of various microorganisms in the aqueous ink and in the container that houses it. Examples of the preservatives and fungicides other than OIT and PCMC include MIT, CMIT, BIT, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, sodium 2-pyridinethiol-1-oxide, and the like.

[0043] <Water-soluble organic solvent> Examples of the water-soluble organic solvent include methanol, ethanol, propanol, butanol, glycerin, diglycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone, and conventional, commonly used water-soluble organic solvents that are compatible with water can be used.

[0044] <Resin and resin particles> Examples of resins include acrylic resins, urethane resins, styrene-butadiene resins, alkyd resins, sulfamide resins, maleic acid resins, polyvinyl acetate resins, ethylene vinyl acetate resins, vinyl chloride-vinyl acetate resins, copolymers of styrene and maleic ester, styrene-acrylonitrile resins, cyanate-modified polyalkylene glycols, ester gums, xylene resins, urea resins, urea aldehyde resins, phenolic resins, alkylphenolic resins, terpene phenolic resins, rosin resins and their hydrogenated compounds, rosin phenolic resins, polyvinyl alkyl ethers, polyamide resins, polyolefin resins, nylon resins, polyester resins, and cyclohexanone resins. Examples of the resin particles include resin particles made of polyolefin resin, acrylic resin, nylon resin, silicone resin, urethane resin, fluororesin, and the like.

[0045] <Rust inhibitor> Examples of the rust inhibitor include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, and dialkylthiourea.

[0046] <Wetting agent> As wetting agents, in addition to water-soluble organic solvents, there are disaccharides such as urea, sorbitol, mannitol, dextrin, trehalose, oligosaccharides, sucrose, cyclodextrin, glucose, N,N,N-trialkyl amino acids such as glycine betaine, hyaluronic acids, reduced or non-reduced starch hydrolyzates, sodium pyrophosphate, and the like.

[0047] <pH adjuster> As pH adjusters, there are basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide, basic organic compounds such as sodium acetate, triethanolamine, diethanolamine, lactic acid, acetic acid, citric acid, and the like.

[0048] <Pigment dispersant> As pigment dispersants, there are water-soluble resins such as water-soluble maleic acid resin, water-soluble styrene resin, water-soluble styrene maleic acid resin, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl butyral, water-soluble urethane resin, and the like.

[0049] <Chelating agent> As chelating agents, there are ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol ether diamine tetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and their alkali metal salts, ammonium salts or amine salts, and the like.

[0050] The aqueous ink composition according to the present invention can be produced by any conventionally known method. Specifically, the respective components are blended in necessary amounts and mixed with various stirrers such as propeller stirring, homodisper, or homomixer, and various dispersers such as bead mills, etc., for production.

[0051] <Writing instrument> The aqueous ink composition of the present invention is filled into writing instruments such as marking pens and ballpoint pens equipped with a fiber tip, a felt tip, a plastic tip, a fountain pen-type metal tip, or a ballpoint pen tip at the writing tip, as well as fountain pens. The writing instruments may be of the cap type equipped with a cap that covers the nib, or may be of the retractable type having a retractable mechanism such as a knock type, a rotation type, or a slide type, and capable of storing the nib in the barrel.

[0052] <Marking pen> Examples of materials for the nibs of writing instruments include metals such as cemented carbide, stainless steel, and gold, and ceramics such as silicon carbide for ballpoint pens and fountain pens, and synthetic resins such as polyester, nylon, polyurethane, polyethylene, polypropylene, and acrylic for marking pens (sign-tip pens).

[0053] The pen tip can be a fiber tip, a felt tip, a porous tip, or a plastic tip. Fiber tips made by bonding fiber bundles with resin or porous tips made by fusing resin particles such as polypropylene are particularly suitable. In particular, when nylon is used as the fiber bundle, the writing feel becomes softer, and when tracing, writing can be done without rubbing the printed text on the paper surface too hard, making it more effective when using fluorescent ink. The pen tip shape can be any of a bullet type, a chisel type, a brush pen type, etc.

[0054] The pen tip contains voids made of pores, and the pore diameter can be set arbitrarily as long as it is large enough to allow the colorant to pass through. The porosity is preferably 50 to 75% for fiber tips and 30 to 50% for porous tips. Taking ink composition ejection performance into consideration, the porosity of the pen tip is more preferably 55 to 70% for fiber tips and 40 to 50% for porous tips. If the porosity is within the above range, clogging of the pigment or copolymer does not occur, and an appropriate ink ejection rate can be maintained.

[0055] The ink filling mechanism of the marking pen may be configured to directly fill the ink composition, or may include an ink reservoir or ink occlusion body that can be filled with the ink composition. It is preferable that the marking pen be configured to directly fill the ink composition and include a stirring body, such as a stirring ball, built into the ink reservoir to stir the ink in order to redisperse the pigment. Examples of the shape of the stirring body include a spherical body, a rod-like body, and the like. The material of the stirring body is not particularly limited, but specific examples include metal, ceramic, resin, and glass. Furthermore, when the marking pen includes an ink occlusion body that can be filled with the ink composition, the ink occlusion body is preferably a fiber bundle made of twisted fibers.

[0056] The fiber bundle contains voids made of pores, similar to the pen tip, and the pore diameter can be set arbitrarily as long as it is large enough to allow the pigment or copolymer to pass through. On the other hand, in consideration of ink supply to the pen tip, the porosity of the fiber bundle is preferably 80 to 95%, more preferably 85 to 92%.

[0057] The ink supply mechanism is also not particularly limited, and examples include: (1) a mechanism that uses an ink guide core made of a fiber bundle or the like as an ink flow rate adjusting member to supply ink to the pen tip; (2) a mechanism that uses a comb-shaped ink flow rate adjusting member to supply ink to the pen tip; (3) a mechanism that uses a valve mechanism to supply ink to the pen tip; and (4) a mechanism that supplies ink directly to the pen tip from an ink reservoir or barrel equipped with a pen tip. Furthermore, the marking pen may also be equipped with a pen tip extension / retraction mechanism. The pen tip extension / retraction mechanism is not particularly limited, and examples include a knock-type, a rotary-type, and a slide-type. In addition to a pen equipped with a single pen tip, the marking pen may also be a double-ended type in which pen tips of different thicknesses and shapes are equipped on both ends of the barrel. In the double-ended type, one end may be a ballpoint pen.

[0058] The marking pen containing the ink composition of the present invention can be constructed by appropriately selecting each component from the pen tip, ink filling mechanism, and ink supply mechanism described above, but considering the ability to maintain a stable ink discharge volume, it is preferable that the marking pen is a fill-type marking pen that has a pen tip using the fiber tip or porous tip and an ink filling mechanism that uses the fiber bundle as an ink absorbing body, and that the pen tip and ink absorbing body are connected so that the ink absorbed in the ink absorbing body can be supplied to the pen tip.

[0059] <Ballpoint pen> Examples of ballpoint pen tips that can be used include those made by cutting metal to form a ball seat and ink outlet inside, and those made by forming multiple inward protrusions on the inner surface near the tip of a metal pipe by pressing from the outside, with ink outlet gaps extending radially outward from the center between the inward protrusions. Tips made by pressing and deforming in particular have a relatively small contact area with the rear end of the ball, allowing for a smooth writing feel even with low writing pressure. The ball held in the ballpoint pen tip is effectively made of cemented carbide, stainless steel, ruby, ceramic, or the like, with an outer diameter of 0.1 to 2.0 mm, preferably 0.2 to 1.5 mm, and more preferably 0.3 to 1.2 mm. Larger ball diameters (e.g., 0.7 to 1.2 mm) tend to result in a larger ink ejection volume during writing, making the ink of the present invention particularly effective. The ballpoint pen tip may be configured so that a resilient member is disposed within the tip to resiliently repel the rear end of the ball forward, so that when not writing, the ball is pressed against the inner edge of the tip tip to create a tight contact state, and when writing, the ball is retracted by writing pressure to allow ink to flow out, thereby preventing ink leakage when not in use. Examples of the resilient member include a thin metal wire spring, a spring with a straight portion (rod portion) at one end, and a linear plastic processed body, and are configured to be resilient with a resilience of 5 to 40 g.

[0060] For the barrel containing the aqueous ink composition, a molded article made of a thermoplastic resin such as polyethylene, polypropylene, or polyethylene terephthalate is preferably used in terms of low ink evaporation and productivity. The tip may be directly connected to the barrel, or the barrel and tip may be connected via a connecting member. Furthermore, a replaceable cartridge configuration is also possible. For ink compositions containing low viscosity inks, methods include attaching an ink retaining member to the front of the barrel and directly storing the ink composition in the barrel, or impregnating a porous body or a fiber-processed body with the ink composition. Furthermore, by using a transparent, colored transparent, or translucent molded body as the barrel, the ink color, remaining ink amount, etc. can be confirmed. The barrel may be in the form of a ballpoint pen refill, with the refill stored in the outer barrel, or the barrel itself, with a tip attached to the tip, may serve as the ink container, and ink may be directly filled into the barrel.

[0061] Ballpoint pens using barrels can be either cap-type or retractable. Retractable ballpoint pens can be any type that has a writing tip provided on a ballpoint pen refill housed within an outer barrel exposed to the outside air and that protrudes from the outer barrel opening when the retraction mechanism is activated. Examples of operating methods for the retraction mechanism include knock-type, rotation-type, and slide-type. Examples of knock-type pens include a configuration in which a knock portion is provided on the rear end or side surface of the outer barrel, and the writing tip of the ballpoint pen refill protrudes and retracts from the front end opening of the outer barrel when the knock portion is pressed, or a configuration in which the writing tip of the ballpoint pen refill protrudes and retracts from the front end opening of the outer barrel when a clip portion provided on the outer barrel is pressed. Examples of rotation-type pens include a configuration in which the outer barrel has a rotating portion (such as a rear barrel) and the writing tip of the ballpoint pen refill protrudes and retracts from the front end opening of the outer barrel when the rotating portion is turned. Examples of the sliding type include a configuration in which a sliding portion is provided on the side of the barrel, and the writing tip of the ballpoint pen refill is protruded and retracted from the front end opening of the outer barrel by operating the sliding portion, or a configuration in which the writing tip of the ballpoint pen refill is protruded and retracted from the front end opening of the outer barrel by sliding a clip portion provided on the outer barrel. The retractable ballpoint pen may be a composite type in which a single ballpoint pen refill is housed in the outer barrel, or a composite type in which multiple ballpoint pen refills are housed in the outer barrel. The ink reservoir tube that constitutes the ballpoint pen refill may be made of resin or metal.

[0062] The rear end of the ink contained in the ballpoint pen refill can also be filled with an ink backflow preventer. Either a liquid or solid ink backflow preventer can be used. Examples of liquid ink backflow preventers include non-volatile media such as polybutene and silicone oil, and silica, aluminum silicate, etc. can also be added to the media if desired. Examples of solid ink backflow preventers include resin molded products. Note that the liquid and solid ink backflow preventers can also be used in combination. [Example]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The compositions of the water-based ink compositions of the examples and comparative examples are shown in Tables 1 to 3. The numerical values of the compositions in the tables indicate parts by mass.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] The contents of the ingredients in the table are explained according to the note numbers. (1) Pink fluorescent colored resin particle water dispersion [pigment content: 37% by mass, manufactured by Nippon Fluorescent Chemical Co., Ltd., product name: Lumicol NKW-3207E] (2) Red organic pigment aqueous dispersion [pigment content: 30% by mass, manufactured by Sanyo Pigment Co., Ltd., product name: SANDYE SUPER COLOUR RED 1326] (3) Blue acid dye [manufactured by Hodogaya Chemical Co., Ltd., product name: Brilliant Blue FCF] (4) Polyoxyethylene alkyl (C12, C13) ether phosphate ester [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf A208N] (5) Polyoxyethylene tridecyl ether phosphate ester [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf A212C] (6) Polyoxyethylene alkyl (C12) ether phosphate ester [manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RD-510Y] (7) Polyoxyethylene tridecyl ether phosphate ester [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf A215C] (8) Dipolyoxyethylene alkyl (C12-C15) ether phosphate ester [manufactured by Nikko Chemicals Co., Ltd., trade name: NIKKOL DDP-8] (9) Polyoxyethylene alkyl (C13 branched) ether phosphate ester [manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RS-710] (10) Polyoxyethylene alkenyl (C18) ether phosphate ester [manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RD-720] (11) Polyoxyethylene aryl (phenol derivative) ether phosphate ester [manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol CP-120] (12) Polyoxyethylene lauryl ether phosphate ester [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf A219B] (13) Sodium dipolyoxyethylene lauryl ether phosphate [manufactured by Nikko Chemicals Co., Ltd., trade name: NIKKOL DLP-10] (14) Polyoxyethylene lauryl ether [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: DKS NL-90] (15) Polyoxyethylene alkyl (C12-C14) ether [manufactured by Sanyo Chemical Industries, Ltd., trade name: Sannonic SS-120] (16) Polyoxyethylene isodecyl ether [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Noigen SD-80] (17) Lauryl phosphate ester [manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol ML-200]

[0068] <Ink preparation> The raw materials, excluding the polyether phosphate and polyoxyalkylene alkyl ether, were mixed in the amounts shown in the Examples and Comparative Examples, and the mixture was stirred using a disper at 30°C and 800 rpm for 1 hour. The polyether phosphate ester and its salt, and the polyoxyalkylene alkyl ether were then mixed and stirred for another 1 hour to prepare aqueous ink compositions.

[0069] <Making a marking pen> A water-based marking pen was prepared by filling a commercially available marking pen (manufactured by Pilot Corporation; SGR-8SL) with 2.4 g of each of the ink compositions of the Examples and Comparative Examples.

[0070] <Testing and Evaluation> Tests and evaluations were carried out in the following manner. The results obtained are shown in Tables 1 to 3.

[0071] <Solubilization test> In the examples and comparative examples, the components excluding glycerin, colorant, polyether phosphate ester and its salt, and polyoxyalkylene alkyl ether were mixed and stirred in a disperser at 30°C and 800 rpm for 1 hour to prepare a dispersion. When the appearance of the prepared dispersion was visually inspected, it was confirmed that all dispersions were cloudy and white. The prepared dispersion was mixed with polyether phosphate ester and its salt, and polyoxyalkylene alkyl ether, respectively, and stirred for another 1 hour. The appearance of the dispersion was then visually inspected to evaluate the solubilization of OIT. ○: The appearance is transparent. ×: Appearance is cloudy.

[0072] <Evaluation of bleed-through of handwriting> Each writing instrument that was confirmed to be usable was placed on a piece of report paper (JIS P3201 writing paper A) at room temperature (25°C) with the tip of the pen touching the paper. Immediately after it came to rest, a straight line of 5 cm was written in 3 seconds, and the handwriting formed was visually inspected from the back of the paper. ◯: No coloring due to bleed-through was observed. ×: Coloring due to strike-through was observed.

Claims

1. The aqueous ink composition for a writing instrument contains at least water, a colorant, 2-n-octyl-isothiazolin-3-one, and a polyether phosphate ester and / or a salt thereof.

2. 2. The aqueous ink composition for a writing instrument according to claim 1, wherein the HLB of the polyether phosphate ester is 5 or more and 20 or less.

3. 3. The aqueous ink composition for a writing instrument according to claim 1, further comprising 4-chloro-3-methylphenol.

4. A writing instrument containing the aqueous ink composition for a writing instrument according to any one of claims 1 to 3.

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