Aqueous ink composition for writing instrument

Abstract

To provide an aqueous ink composition for writing instruments that can prevent generation of precipitates even in the case of storage in a glass ink reservoir containing aluminum.SOLUTION: An aqueous ink composition for writing instruments comprising water, an acid dye having a fluorescein skeleton, and an organophosphorus chelating agent having two phosphonic acid groups.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an aqueous ink composition for a writing instrument. [Background technology]

[0002] Water-based ink compositions for writing instruments are generally stored in glass ink reservoirs (e.g., glass ink containers) from the viewpoint of ease of storage, etc. However, it is known that when water-based ink compositions for writing instruments are stored in glass ink reservoirs, alkaline components are eluted from the glass ink reservoir, causing precipitates.

[0003] Patent Document 1 discloses that an aqueous ink composition for a writing instrument, which contains an acid dye (e.g., an acid dye having a fluorescein skeleton) and a chelating agent such as ethylenediaminetetraacetate, can suppress the occurrence of precipitates even when the composition is contained in a glass ink reservoir. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-053183 Summary of the Invention

[0005] The present inventors considered it advantageous to use an aluminum-containing glass ink reservoir as a glass ink reservoir capable of storing an aqueous ink composition for a writing instrument, from the viewpoint of the hardness and stability of the reservoir. Therefore, the present inventors attempted to store an aqueous ink composition for a writing instrument containing an acid dye having a fluorescein skeleton and an optional chelating agent in an aluminum-containing glass ink reservoir. Their investigations revealed that, despite the inclusion of a chelating agent, the aqueous ink composition for a writing instrument may develop precipitates after storage for a certain period of time. Furthermore, their investigations also revealed that such precipitates do not develop when the ink composition is stored in an aluminum-free glass ink reservoir.

[0006] Therefore, one object of the present disclosure is to provide a water-based ink composition for a writing instrument that can suppress the occurrence of precipitates even when stored in an aluminum-containing glass ink reservoir.

[0007] The present inventors have found that the use of a specific organophosphorus chelating agent makes it possible to obtain an aqueous ink composition for a writing instrument that can suppress the formation of precipitates even when stored in an aluminum-containing glass ink reservoir. The present disclosure is based on this finding.

[0008] According to one embodiment of the present disclosure, there is provided an aqueous ink composition for a writing instrument, comprising water, an acid dye having a fluorescein skeleton, and an organophosphorus chelating agent having two phosphonic acid groups.

[0009] According to the present disclosure, it is possible to suppress the occurrence of precipitates in a water-based ink composition for a writing instrument even when the composition is stored in an ink reservoir made of aluminum-containing glass. [Brief explanation of the drawings]

[0010] [Figure 1] In Test Example 3, the precipitates observed in Reference Example 2 were evaluated by energy dispersive X-ray analysis, and the results are shown. [Figure 2]In Test Example 3, the precipitates observed in Reference Example 2 were collected on carbon tape and subjected to elemental map analysis, and the results are shown below. Specific Description of the Invention

[0011] According to one embodiment of the present disclosure, an aqueous ink composition for a writing instrument comprises water, an acid dye having a fluorescein skeleton, and an organophosphorus chelating agent having two phosphonic acid groups. Each component of the aqueous ink composition for a writing instrument of the present disclosure will be described in detail below.

[0012] (Acid dyes with a fluorescein skeleton) In the present disclosure, an "acid dye having a fluorescein skeleton" refers to an acid dye having a basic skeleton represented by the following formula (I):

[0013] [ka] The acid dye having a fluorescein skeleton is not particularly limited as long as it has the above structure and can be used as an acid dye. Since acid dyes having a fluorescein skeleton can be used as acid dyes, they typically have one or more acidic groups (e.g., hydroxyl, carboxyl, or sulfonic acid groups) in the basic skeleton. The acidic group may be directly bonded to the basic skeleton (i.e., a hydrogen atom in the basic skeleton may be substituted with the acidic group) or may be contained in an optional substituent described below (i.e., a hydrogen atom in an optional substituent may be substituted with the acidic group). The basic skeleton may also be substituted with one or more identical or different optional substituents (including, but not limited to, an optionally substituted alkyl group; an optionally substituted aryl group; a halogen atom such as fluorine, chlorine, bromine, or iodine; an optionally substituted amino group; ═O, etc.). The acid dye having a fluorescein skeleton may also be a salt of a compound having the above skeleton (e.g., a metal salt such as sodium or potassium).

[0014] According to one embodiment of the present disclosure, the basic skeleton represented by formula (I) is a skeleton represented by the following formula (I-1): [ka] It has.

[0015] According to one embodiment of the present disclosure, the basic skeleton represented by formula (I) is a skeleton represented by the following formula (I-2): [ka] It has.

[0016] According to one embodiment of the present disclosure, the basic skeleton represented by formula (I) is a skeleton represented by the following formula (I-3): [ka] It has.

[0017] According to one embodiment of the present disclosure, the skeleton represented by formula (I), (I-1), (I-2) or (I-3) is substituted with one or more (preferably 2 to 4, more preferably 4) halogen atoms. According to one embodiment of the present disclosure, the skeleton represented by formula (I), (I-1), (I-2) or (I-3) is substituted with one or more (preferably 2 to 4, more preferably 4) bromine atoms.

[0018] Acid dyes having a fluorescein skeleton include, but are not limited to, eosin (CI Acid Red 87, Eosin Y), phloxine (CI Acid Red 92), erythrosin (CI Acid Red 51), rose bengal (CI Acid Red 94), CI Acid Red 289, CI Acid Red 52, CI Acid Red 388, rhodamine 110, rhodamine 123, rhodamine 6G (CI Basic Red 1), rhodamine 116, rhodamine B (CI Basic Violet 10), rhodamine 3B, rhodamine 19, rhodamine 3GO, sulforhodamine G, and derivatives thereof (including salts), which may be used alone or in any combination of two or more. Eosin derivatives include, for example, eosin B. Erythrosin derivatives include, for example, erythrosin, erythrosin B, and erythrosin isothiocyanate.

[0019] According to a preferred embodiment of the present disclosure, the acid dye having a fluorescein skeleton is preferably eosin or a derivative thereof, more preferably eosin (eosin Y) or eosin B, and even more preferably eosin (eosin Y).

[0020] The amount of the acid dye having a fluorescein skeleton contained in the aqueous ink composition for a writing instrument of the present disclosure is not particularly limited as long as the object of the present disclosure can be achieved. The amount of the acid dye may be, for example, 0.01 to 10% by mass, preferably 0.1 to 8% by mass, and more preferably 0.3 to 5% by mass, based on the total mass of the aqueous ink composition for a writing instrument.

[0021] (Organophosphorus chelating agent with two phosphonic groups) In the present disclosure, an "organophosphorus chelating agent having two phosphonic groups" refers to an organophosphorus-containing chelating agent having two phosphonic groups in the molecule. In addition, the "phosphonic group" in the present disclosure refers to a group having the structure "-P(=O)(OH)2" or a group in which the group forms a salt with a metal ion. Examples of the organophosphorus chelating agent include, but are not limited to, 1-hydroxyethane-1,1-diphosphonic acid (HEDP), ethane-1,1-diphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, and salts thereof, which may be used alone or in any combination of two or more. Examples of salts of the organophosphorus chelating agents include, but are not limited to, alkali metal salts, alkaline earth metal salts, ammonium salts, and ethanolamine salts, with alkali metal salts being preferred and sodium salts being more preferred.

[0022] According to one embodiment of the present disclosure, the organophosphorus chelating agent comprises 1-hydroxyethane-1,1-diphosphonic acid or a salt thereof, preferably 1-hydroxyethane-1,1-diphosphonic acid or a sodium salt thereof, and more preferably 1-hydroxyethane-1,1-diphosphonic acid or tetrasodium 1-hydroxyethane-1,1-diphosphonate.

[0023] The amount of the organophosphorus chelating agent contained in the aqueous ink composition for a writing instrument of the present disclosure is not particularly limited as long as the object of the present disclosure can be achieved. The amount of the organophosphorus chelating agent may be, for example, 0.01 to 10 mass %, preferably 0.02 to 5 mass %, more preferably 0.03 to 3 mass %, and even more preferably 0.05 to 1 mass %, based on the total mass of the aqueous ink composition for a writing instrument.

[0024] The ratio of the acid dye to the organophosphorus chelating agent contained in the aqueous ink composition for a writing instrument of the present disclosure (the acid dye / the organophosphorus chelating agent) may be, for example, 0.001 to 1000, preferably 0.02 to 400, more preferably 0.3 to 100, and even more preferably 1 to 30, based on the mass of these agents contained in the aqueous ink composition for a writing instrument.

[0025] (water) The aqueous ink composition for a writing instrument of the present disclosure comprises water. The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltered water, and distilled water. The amount of water contained in the aqueous ink composition for a writing instrument of the present disclosure is not particularly limited, and can be appropriately adjusted by a person skilled in the art, taking into consideration the amounts of the acid dye, the organophosphorus chelating agent, and other optional components described below. The amount of water may be, for example, 50 to 99.5% by mass, preferably 70 to 99.5% by mass, and more preferably 80 to 99.5% by mass, based on the total mass of the aqueous ink composition for a writing instrument.

[0026] (Other optional ingredients) The aqueous ink composition for a writing instrument of the present disclosure may contain, as necessary, any optional components such as other dyes, solvents, pH adjusters, preservatives, surfactants, and rust inhibitors, as long as the purpose of the present disclosure is not impaired. These may be used alone or in any combination of two or more.

[0027] In the present disclosure, "other dyes" refers to dyes other than the acid dyes having the fluorescein skeleton. Examples of other dyes include, but are not limited to, CI Acid Red 18, CI Acid Orange 10, CI Acid Yellow 3, CI Acid Yellow 7, CI Acid Yellow 23, CI Acid Yellow 42, CI Acid Green 3, CI Acid Green 16, CI Acid Blue 1, CI Acid Blue 9, CI Acid Blue 22, CI Acid Blue 90, CI Acid Violet 15, CI Acid Violet 49, CI Acid Black 1, and CI Acid Black 2, Acid dyes such as; CI Basic Orange 2, CI Basic Orange 14, CI Basic Green 4, CI Basic Blue 9, CI Basic Blue 26, CI Basic Violet 1, CI Basic Violet 3, CI Basic Violet 10, Chrysoidine (CI11270), Crystal Violet (CI42555), Malachite Green (CI42000), Acridine red (CI45000), Pyronin G (CI45005), and Rhodamine S (CI45050), Basic dyes such as; CI Direct Red 28, CI Direct Yellow 44, CI Direct Blue 86, CI Direct Blue 87, CI Direct Violet 51, CI Direct Black 19, Direct Sky Blue 5B (CI24400), Direct Violet BB (CI27905), Direct Black 38 (CI30235), and Phthalocyanine Blue (CI74180), etc. direct dyes; CI Food Yellow 3, and CI Hood Black 2, food dyes such as; These derivatives; These may be used alone or in any combination of two or more. When other dyes are contained in the aqueous ink composition for a writing instrument of the present disclosure, the amount thereof can be appropriately adjusted by a person skilled in the art.

[0028] Examples of the solvent include, but are not limited to, (a) glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and glycerin; (b) Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols; (c) glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; These may be used alone or in any combination of two or more. When a solvent is contained in the aqueous ink composition for a writing instrument of the present disclosure, the amount thereof may be, for example, 0.01 to 10 mass%, preferably 0.1 to 8 mass%, and more preferably 0.5 to 5 mass%, based on the total mass of the aqueous ink composition for a writing instrument. From the viewpoint of being able to suppress evaporation of water from the pen tip and / or being able to write with a certain degree of fluidity even after evaporation, the solvent preferably contains a glycol, and more preferably contains ethylene glycol and / or diethylene glycol.

[0029] Examples of pH adjusters include, but are not limited to, basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, and sodium hydroxide; basic organic compounds such as sodium acetate, triethanolamine, and diethanolamine; acidic inorganic compounds such as hydrochloric acid and nitric acid; and acidic organic compounds such as acetic acid, lactic acid, and citric acid. These may be used alone or in any combination of two or more. When a pH adjuster is included in the aqueous ink composition for a writing instrument of the present disclosure, the amount thereof may be, for example, 0.01 to 10% by mass, preferably 0.1 to 8% by mass, and more preferably 0.5 to 5% by mass, based on the total mass of the aqueous ink composition for a writing instrument. From the viewpoints of being able to suppress evaporation of water from the pen tip, and / or being able to maintain a certain level of fluidity even after evaporation, and / or being able to stably dissolve acid dyes, the pH adjuster preferably includes a basic organic compound, more preferably triethanolamine and / or diethanolamine, and even more preferably triethanolamine.

[0030] Preservatives include, but are not limited to, 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, 2-pyridinethiol-1-oxide sodium, 3-iodo-2-propynyl butylcarbamate sodium benzoate, and phenol These may be used alone or in any combination of two or more. When a preservative is contained in the aqueous ink composition for a writing instrument of the present disclosure, the amount thereof may be, for example, 0.0001 to 10% by mass, preferably 0.0001 to 1% by mass, more preferably 0.001 to 0.1% by mass, and even more preferably 0.01 to 0.1% by mass, based on the total mass of the aqueous ink composition for a writing instrument.

[0031] Examples of surfactants include, but are not limited to, nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, surfactants having an acetylene bond in their structure, silicone surfactants, phosphate ester surfactants, and fluorine-based surfactants. These surfactants adjust the surface tension of the ink composition within an appropriate range and can maintain good wettability with respect to the pen tip. This can improve ink blobbing resistance, provide good ink ejection properties, and / or produce good handwriting with reduced smearing.

[0032] As the surfactant, it is preferable to use a nonionic surfactant, from the viewpoint of being able to fully obtain the effects of the surfactant without inhibiting the effects of the organic phosphorus chelating agent having two phosphonic acid groups. Among nonionic surfactants, those having a polyoxyalkylene structure, such as polyetheramine and polyoxyalkylene glycol, are preferred, from the viewpoint of being particularly easy to obtain the effects. Furthermore, among those having a polyoxyalkylene structure, surfactants having a polyoxyethylene structure are preferred, from the viewpoint of being excellent in dissolution stability with the organic phosphorus chelating agent and the acid dye, and being more easy to obtain the effects.

[0033] Examples of the rust inhibitor include, but are not limited to, benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, and dialkylthiourea, which may be used alone or in any combination of two or more. When a rust inhibitor is contained in the aqueous ink composition for a writing instrument of the present disclosure, the amount thereof may be, for example, 0.01 to 10% by mass, preferably 0.1 to 8% by mass, and more preferably 0.5 to 5% by mass, based on the total mass of the aqueous ink composition for a writing instrument.

[0034] The pH of the aqueous ink composition for a writing instrument of the present disclosure is not particularly limited as long as the object of the present disclosure can be achieved, and may be, for example, 3 to 12, preferably 6 to 11, more preferably 8 to 10, and even more preferably 8.5 to 9.5.

[0035] The viscosity of the aqueous ink composition for a writing instrument of the present disclosure may be any viscosity, and can be adjusted appropriately by a person skilled in the art depending on the application, etc. The viscosity is, for example, 0.1 to 100 mPa·s, more preferably 0.5 to 10 mPa·s, and even more preferably 1 to 2 mPa·s. The viscosity of the ink composition is measured using a B-type rotational viscometer under conditions of 20°C and a rotation speed of 60 rpm, and the measuring instrument can be, for example, a BII-type viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd.).

[0036] The surface tension of the aqueous ink composition for a writing instrument of the present disclosure may be any surface tension, and can be adjusted appropriately by a person skilled in the art depending on the application, etc. The surface tension is, for example, 40 to 60 mN / m, preferably 50 to 60 mN / m, and more preferably 51 to 60 mN / m. A surface tension of the aqueous ink composition for a writing instrument of the present disclosure within the above range (particularly 51 to 60 mN / m) is particularly advantageous in that it reduces the risk of bleeding, strike-through, and / or dripping.

[0037] [Method for producing an aqueous ink composition for a writing instrument] The aqueous ink composition for a writing instrument of the present disclosure can be produced by any method, for example, by blending the required amounts of the above-mentioned components and mixing them using a mixer such as a propeller mixer, a homodisper, a homomixer, or a planetary mixer, or a disperser such as a bead mill.

[0038] [Uses of water-based ink compositions for writing instruments]

[0039] According to one embodiment of the present disclosure, the aqueous ink composition for a writing instrument of the present disclosure is suitable for being contained in an aluminum-containing glass ink reservoir.

[0040] (Aluminum-containing glass ink reservoir) In the present disclosure, an "aluminum-containing glass ink reservoir" refers to a reservoir made of aluminum-containing glass that is capable of containing the aqueous ink composition for a writing instrument. At least the interior of the ink reservoir (i.e., the surface that comes into contact with the aqueous ink composition for a writing instrument) is made of aluminum-containing glass. The portion of the ink reservoir that does not come into contact with the aqueous ink composition for a writing instrument (e.g., the outer surface) may be made of resin, wood, or coated with lacquer, etc.

[0041] The ink reservoir may be made of aluminum-containing glass (i.e., containing at least aluminum, silicon, and oxygen) and may have any composition. Elements other than aluminum, silicon, and oxygen that may be contained in the ink reservoir include, but are not limited to, sodium, magnesium, gold, silver, copper, manganese, neodymium, uranium, nickel, selenium, calcium, palladium, cadmium, barium, cesium, chromium, titanium, iodine, sulfur, cobalt, iron, zirconium, niobium, tantalum, strontium, rubidium, lead, zinc, and potassium. These elements may be present alone or in any combination of two or more. In this disclosure, when the elemental and compound compositions of the ink reservoir are referred to, the elemental and compound compositions refer to the elemental and compound compositions of the surface that comes into contact with the aqueous ink composition for a writing instrument under normal storage conditions. Therefore, if the ink reservoir is, for example, a container with a lid, the elemental and compound compositions refer to the elemental and compound compositions excluding the lid. Furthermore, if the ink reservoir is coated with resin, wood, lacquer, etc. in a portion that does not come into contact with the aqueous ink composition for a writing instrument, the elemental composition and compound composition refer to the elemental composition and compound composition excluding the resin, wood, lacquer, etc.

[0042] The amount of aluminum contained in the ink reservoir is, for example, 1 to 5 mass %, preferably 1.5 to 4.5 mass %, more preferably 2 to 4 mass %, and even more preferably 2.5 to 3.5 mass %, based on the total amount of elements (preferably the total amount of elements with atomic numbers 11 to 92) detected when the ink reservoir is measured with an elemental analyzer (preferably an X-ray fluorescence elemental analyzer).

[0043] The amount of silicon contained in the ink reservoir is, for example, 40 to 50 mass %, preferably 41 to 49 mass %, and more preferably 42 to 48 mass %, based on the total amount of elements (preferably the total amount of elements with atomic numbers 11 to 92) detected when the ink reservoir is measured with an elemental analyzer (preferably an X-ray fluorescence elemental analyzer).

[0044] The amount of calcium contained in the ink reservoir is, for example, 38 to 48 mass %, preferably 39 to 47 mass %, and more preferably 40 to 46 mass %, based on the total amount of elements (preferably the total amount of elements with atomic numbers 11 to 92) detected when the ink reservoir is measured with an elemental analyzer (preferably an X-ray fluorescence elemental analyzer).

[0045] According to a preferred embodiment of the present disclosure, the ink reservoir has the following elemental composition based on the total amount of elements (preferably the total amount of elements with atomic numbers 11 to 92) detected when the ink reservoir is measured with an elemental analyzer (preferably an X-ray fluorescence elemental analyzer): Aluminum 1-5% by mass Calcium 38-48% by mass Silicon 40-50% by mass It has.

[0046] The elemental composition of the ink reservoir in the present disclosure refers to the numerical value obtained by elemental analysis (preferably, X-ray elemental analysis, more preferably, X-ray fluorescence elemental analysis). Therefore, the ink reservoir may contain elements other than those mentioned above, and elements with atomic numbers 1 to 10 and atomic numbers 93 or higher (e.g., carbon, oxygen, hydrogen, nitrogen, etc.) that are not generally detected by elemental analysis (preferably, X-ray elemental analysis, more preferably, X-ray fluorescence elemental analysis) are not included in the "total amount of elements with atomic numbers 11 to 92 detected when measured with an elemental analyzer (preferably, X-ray fluorescence elemental analysis)."

[0047] According to a preferred embodiment of the present disclosure, the elemental composition of the ink reservoir means a value obtained by fluorescent X-ray analysis under the following conditions. Measurement equipment: EA1400 X-ray fluorescence analyzer (Hitachi High-Tech Science Corporation) Tube target element: Rh Quantitative analysis method: bulk fundamental parameter method

[0048] According to one embodiment of the present disclosure, the ink reservoir contains at least aluminum oxide (Al2O3), calcium oxide (CaO), and silicon dioxide (SiO2).

[0049] According to one embodiment of the present disclosure, the amount of aluminum oxide contained in the ink reservoir is 0.1 to 5 mass %, preferably 0.3 to 3 mass %, and more preferably 0.5 to 2.5 mass %, based on the total mass of the ink reservoir.

[0050] According to one embodiment of the present disclosure, the amount of calcium oxide contained in the ink reservoir is 5 to 15 mass %, preferably 6 to 13 mass %, and more preferably 7 to 11 mass %, based on the total mass of the ink reservoir.

[0051] According to one embodiment of the present disclosure, the amount of silicon dioxide contained in the ink reservoir is 70 to 80 mass %, preferably 71 to 79 mass %, and more preferably 72 to 78 mass %, based on the total mass of the ink reservoir.

[0052] According to one embodiment of the present disclosure, the ink reservoir has the following composition based on the total mass of the ink reservoir: Al2O30.1~5% by mass CaO: 5~15% by mass SiO2: 70~80% by mass It has.

[0053] The aqueous ink composition for a writing instrument of the present disclosure may be used as an ink for a writing instrument (e.g., a fountain pen) equipped with an ink supply mechanism utilizing a grooved comb, a ballpoint pen, a brush pen, a calligraphy pen, or a writing instrument (e.g., a marker) equipped with an ink supply mechanism utilizing a fiber bundle. From the viewpoint of suppressing precipitation and / or stabilizing physical properties (e.g., viscosity, surface tension), the aqueous ink composition for a writing instrument of the present disclosure can be suitably used as an ink for a writing instrument (e.g., a fountain pen) equipped with an ink supply mechanism utilizing a grooved comb, such as a fountain pen.

[0054] [Methods for suppressing precipitates] According to another embodiment of the present disclosure, there is provided a method for inhibiting precipitation in an aqueous ink composition for a writing instrument to be contained in an aluminum-containing glass ink reservoir, the ink composition comprising water and an acid dye having a fluorescein skeleton, the method comprising: The coexistence of an acid dye having a fluorescein skeleton and an organophosphorus chelating agent having two phosphonic acid groups A method is provided, comprising:

[0055] The definitions of each term and preferred embodiments in the above method are the same as those described above in this specification.

[0056] [Use to suppress precipitation] According to another embodiment of the present disclosure, there is provided use of a composition comprising an organophosphorus chelating agent having two phosphonic acid groups for inhibiting precipitation in an aqueous ink composition for a writing instrument to be contained in an aluminum-containing glass ink reservoir, the aqueous ink composition comprising water and an acid dye having a fluorescein skeleton.

[0057] The definitions of each term and preferred embodiments in the above method are the same as those described above in this specification.

[0058] [Water-based ink products, writing implements] According to another embodiment of the present disclosure, there is provided an aqueous ink product comprising the aqueous ink composition for a writing instrument of the present disclosure contained in the glass ink reservoir.

[0059] According to another embodiment of the present disclosure, there is provided a writing instrument comprising an ink reservoir (preferably a resin or glass ink reservoir, more preferably the glass ink reservoir) containing the aqueous ink composition for a writing instrument of the present disclosure.

[0060] The present disclosure encompasses the following. [1] An aqueous ink composition for a writing instrument, comprising water, an acid dye having a fluorescein skeleton, and an organophosphorus chelating agent having two phosphonic acid groups. [2] The aqueous ink composition for a writing instrument according to [1], wherein the acid dye is eosin or a derivative thereof. [3] The aqueous ink composition for a writing instrument according to [1] or [2], wherein the organophosphorus chelating agent is 1-hydroxyethane-1,1-diphosphonic acid or a salt thereof. [4] The water-based ink composition for a writing instrument according to any one of [1] to [3], which is to be contained in an ink reservoir made of aluminum-containing glass. [5] The aqueous ink composition for a writing instrument according to [4], wherein the aluminum content of the ink reservoir is 1 to 5 mass% based on the total amount of elements with atomic numbers 11 to 92 detected when the ink reservoir is measured using an elemental analyzer. [6] The ink reservoir has the following elemental composition based on the total amount of elements with atomic numbers 11 to 92 detected when the ink reservoir is measured with an elemental analyzer: Aluminum 1-5% by mass Calcium 38-48% by mass Silicon 40-50% by mass The aqueous ink composition for a writing instrument according to [4] or [5], [7] An aqueous ink product comprising a glass ink reservoir containing the aqueous ink composition for a writing instrument according to any one of [1] to [6]. [8] A method for suppressing precipitation in an aqueous ink composition for a writing instrument, which contains water and an acid dye having a fluorescein skeleton and is to be contained in an aluminum-containing glass ink reservoir, comprising: The coexistence of an acid dye having a fluorescein skeleton and an organophosphorus chelating agent having two phosphonic acid groups A method comprising: [9] Use of a composition containing an organophosphorus chelating agent having two phosphonic acid groups for inhibiting precipitation in an aqueous ink composition for a writing instrument to be contained in an aluminum-containing glass ink reservoir, the aqueous ink composition containing water and an acid dye having a fluorescein skeleton. [Example]

[0061] The ink compositions and methods according to the present disclosure are described in more detail below using examples. However, the following examples are not intended to limit the present disclosure in any way. Unless otherwise specified, percentages and ratios described herein are by mass. Furthermore, unless otherwise specified, units and measurement methods described herein are in accordance with the Japanese Industrial Standards (JIS).

[0062] [Example 1: Preparation of aqueous ink composition for writing implements 1] 0.08 parts by mass of a 60% solution of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) (Chilest Co., Ltd., Chelest PH-210) (0.048 parts by mass as HEDP), 1 part by mass of Acid Red 87 (Orient Chemical Industries Co., Ltd., Water Red 2), 1 part by mass of Acid Yellow 42 derivative (Orient Chemical Industries Co., Ltd., Water Yellow 6C), 1 part by mass of Red No. 106 (Daiwa Chemical Co., Ltd.), 1 part by mass of ethylene glycol, 2 parts by mass of triethanolamine, 0.05 parts by mass of a polyalkylene glycol derivative (NOF Corporation, Unilube 75DE-3800), and a 10% solution of preservative (Arcsada Japan Co., Ltd., Proxel XL-2(S)). 0.5 parts by mass (0.05 parts by mass as a preservative) and water (the remainder so that the total amount of the composition was 100 parts by mass) were mixed by propeller stirring to obtain the aqueous ink composition for writing instruments of Example 1.

[0063] [Examples 2 to 4: Preparation of aqueous ink compositions for writing instruments 2] The same method as in Example 1 was carried out, except that 0.32 parts by mass, 0.8 parts by mass, or 1.28 parts by mass of a 60% solution of 1-hydroxyethane-1,1-diphosphonic acid (0.192 parts by mass, 0.48 parts by mass, or 0.768 parts by mass as HEDP, respectively) were used instead of 0.08 parts by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid, to obtain aqueous ink compositions for writing instruments of Examples 2 to 4.

[0064] [Examples 5 and 6: Preparation of aqueous ink composition for writing implements 3] The same method as in Example 1 was carried out, except that 0.2 parts by mass or 2 parts by mass of a 26% solution of tetrasodium 1-hydroxyethane-1,1-diphosphonate (HEDP·4Na) (Chelest PH-214, manufactured by Chelest Co., Ltd.) (0.052 parts by mass or 0.52 parts by mass as HEDP·2Na, respectively) was used instead of 0.08 parts by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid, to obtain aqueous ink compositions for writing instruments of Example 5 and Example 6.

[0065] Reference Example 1: Preparation of aqueous ink composition for writing implements 4 A water-based ink composition for a writing instrument of Reference Example 1 was obtained in the same manner as in Example 1, except that 0.1 part by mass (0.051 part by mass as NTMP) of a 51% solution of nitrilotris(methylenephosphonic acid) (NTMP) (Chilest PH-320, manufactured by Chelest Co., Ltd.) was used instead of 0.08 part by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid.

[0066] Reference Example 2: Preparation of aqueous ink composition for writing implements 5 A water-based ink composition for a writing instrument of Reference Example 2 was obtained in the same manner as in Example 1, except that 0.13 parts by mass (0.0507 parts by mass as NTMP 5Na) of a 39% solution of pentasodium nitrilotris(methylenephosphonate) (NTMP 5Na) (manufactured by Chelest Co., Ltd., Chelest PH-325) was used instead of 0.08 parts by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid.

[0067] Reference Example 3: Preparation of aqueous ink composition for writing implements 6 A water-based ink composition for a writing instrument of Reference Example 3 was obtained in the same manner as in Example 1, except that 0.13 parts by mass (0.052 parts by mass as GLDA 4Na) of a 40% solution of tetrasodium L-glutamate diacetate (GLDA 4Na) (Chelest CMG-40, manufactured by Chelest Co., Ltd.) was used instead of 0.08 parts by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid.

[0068] Reference Example 4: Preparation of aqueous ink composition for writing implements 7 A water-based ink composition for a writing instrument of Reference Example 4 was obtained in the same manner as in Example 1, except that 0.08 parts by mass of the 60% solution of 1-hydroxyethane-1,1-diphosphonic acid was replaced with 0.05 parts by mass (0.05 parts by mass as EDDS 4H 3H O) of ethylenediaminedisuccinic acid (EDDS 4H 3H O) (manufactured by Chelest Co., Ltd., Chelest EDDS-4H).

[0069] [Table 1-1] [Table 1-2]

[0070] [Test Example 1: Elemental analysis of glass ink container] The elemental composition of the glass ink reservoir (glass ink reservoir for fountain pen ink Iroshizuku (product number INK-50) manufactured by Pilot Corporation) used in Test Examples 2 and 4 described below was analyzed by fluorescent X-ray analysis under the following conditions. The results are shown in Table 3. Measurement equipment: EA1400 X-ray fluorescence analyzer (Hitachi High-Tech Science Corporation) Tube target element: Rh Quantitative analysis method: bulk fundamental parameter method

[0071] [Table 2]

[0072] [Table 3]

[0073] [Test Example 2: Evaluation of Precipitates] The aqueous ink compositions for writing instruments obtained in Examples 1 to 6 and Reference Examples 1 to 4 were evaluated for the presence or absence of precipitates after storage for a certain period of time. 50 mL of each aqueous ink composition for writing instruments was placed in an aluminum-containing glass ink reservoir (Pilot Corporation, fountain pen ink Iroshizuku (product number: INK-50), capacity 50 mL). After storing at 50°C for 4 weeks, an appropriate amount of each aqueous ink composition for writing instruments was taken out from the bottom of the container, dropped onto a glass slide, and a cover glass was placed over it. The presence or absence of precipitates was observed visually and under a microscope, and evaluated according to the following criteria. The results are shown in Tables 1-1 and 1-2. A: No precipitates were observed visually or under a microscope. B: No precipitates were observed visually, but slight precipitates were observed under a microscope. C: No precipitates were observed visually, but a medium amount of precipitates was observed under a microscope. D: Precipitates were observed visually, and a large amount of precipitates was observed under a microscope.

[0074] [Test Example 3: Elemental analysis of precipitates] The elemental composition of the precipitates observed in Reference Example 2 of Test Example 2 was evaluated by energy dispersive X-ray analysis under the following conditions. The results are shown in Table 5 and Figures 1 and 2. Figure 2 is a diagram obtained by elemental map analysis of the precipitates collected on carbon tape. Measurement equipment: Elemental analyzer mounted on a tabletop scanning electron microscope JCM-7000 (manufactured by JEOL Ltd.) Quantitative correction method: ZAF method

[0075] [Table 4]

[0076] [Table 5]

[0077] [Test Example 4: Evaluation of physical properties] The water-based ink compositions for writing instruments obtained in Examples 1 and 5 and Reference Examples 1 to 4 were evaluated for physical properties. 50 mL of each aqueous ink composition for writing instruments was placed in an aluminum-containing glass ink reservoir (Pilot Corporation, fountain pen ink Iroshizuku (product number: INK-50), capacity 50 mL). After 12 weeks of storage at 50°C, 20 mL of each aqueous ink composition for writing instruments was taken out and the surface tension, viscosity, and pH of each aqueous ink composition for writing instruments were measured. The viscosity was measured using a B-type rotational viscometer (model: BLII, rotor: BL adapter, Toki Sangyo Co., Ltd.) at 20°C and 60 rpm. The results are shown in Table 6.

[0078] [Table 6]

[0079] From the results of Test Example 2, no precipitates were observed in the aqueous ink compositions for writing instruments of Examples 1 to 6 (Table 1-1). On the other hand, precipitates were observed in the aqueous ink compositions for writing instruments of Reference Examples 1 to 4 (Table 1-2). In particular, it is a completely unexpected fact that precipitates were observed in the aqueous ink compositions for writing instruments of Reference Examples 1 and 2, which contain an organic phosphorus chelating agent having three phosphonic acid groups, while no precipitates were observed in the aqueous ink compositions for writing instruments of Examples 1 to 6, which contain an organic phosphorus chelating agent having two phosphonic acid groups.

[0080] The results of Test Example 3 indicate that the precipitates observed in Reference Example 2 contained aluminum (preferably aluminum and calcium) (Table 5, Figures 1 and 2). Taking into account the results of Test Example 2, it is believed that the presence of two phosphonic acid groups in the molecule of an organophosphorus chelating agent is important in suppressing the formation of precipitates (preferably aluminum-containing precipitates, more preferably aluminum- and calcium-containing precipitates) that may occur when an aqueous ink composition for a writing instrument containing an acid dye having a fluorescein skeleton is stored in an aluminum-containing glass container. Further investigation by the present inventors has revealed that the precipitates that have been a problem in the prior art (for example, Patent Document 1) are mainly precipitates containing sulfur. Therefore, it is believed that the precipitates that are a problem in the present disclosure (preferably aluminum-containing precipitates, more preferably aluminum and calcium-containing precipitates) have completely different precipitate compositions and precipitate formation mechanisms from the precipitates that have been a problem in the prior art. Without being bound by theory, considering that the precipitate observed in Reference Example 2 contained aluminum and calcium, it is believed that the precipitate originating from the acid dye having a fluorescein skeleton is generated by a reaction between aluminum ions (preferably aluminum ions and calcium ions) that can be eluted from the aluminum-containing glass ink reservoir and acidic groups (preferably carboxyl groups and / or hydroxyl groups) in the acid dye having a fluorescein skeleton. It is believed that the organic phosphorus chelating agent having two phosphonic acid groups traps aluminum ions (preferably aluminum ions and calcium ions) that may be eluted from the aluminum-containing glass ink reservoir, thereby inhibiting the reaction between the acid dye having a fluorescein skeleton and the aluminum ions and suppressing the formation of precipitates. Note that, because the precipitates observed in Reference Example 2 also contained calcium, it is believed that the organic phosphorus chelating agent having two phosphonic acid groups also inhibits the reaction between the acid dye having a fluorescein skeleton and the calcium ions, thereby suppressing the formation of precipitates. The above theory is inferred from the following facts: (1) aluminum and calcium elements were detected in Test Example 1; (2) the aqueous ink composition for writing instruments contained little or no aluminum or calcium elements; (3) carbon, aluminum, and calcium elements were detected in Test Example 3; and (4) Fourier transform infrared spectroscopy analysis of the precipitate yielded an infrared absorption spectrum similar to that of eosin.

[0081] The results of Test Example 4 show that the aqueous ink compositions for writing instruments of Examples 1 and 5 showed almost no change in their physical properties even after 12 weeks of storage at 50°C (Table 6). On the other hand, for example, in Reference Example 3, a decrease in surface tension was observed after 12 weeks of storage at 50°C (Table 6). A decrease in surface tension is undesirable because it increases the risk of bleeding, strike-through, and / or dribbling of the aqueous ink composition for writing instruments in writing instruments (particularly in writing instruments equipped with an ink supply mechanism utilizing comb grooves, such as fountain pens). Therefore, the aqueous ink composition for writing instruments of the present disclosure is considered to be particularly advantageous in that it has a low risk of bleeding, strike-through, and / or dribbling of the aqueous ink composition for writing instruments.

Claims

1. An aqueous ink composition for a writing instrument, comprising water, an acid dye having a fluorescein skeleton, and an organophosphorus chelating agent having two phosphonic acid groups.

2. 2. The aqueous ink composition for a writing instrument according to claim 1, wherein the acid dye is eosin or a derivative thereof.

3. 2. The aqueous ink composition for a writing instrument according to claim 1, wherein the organophosphorus chelating agent is 1-hydroxyethane-1,1-diphosphonic acid or a salt thereof.

4. 2. The water-based ink composition for a writing instrument according to claim 1, which is to be contained in an ink reservoir made of aluminum-containing glass.

5. 5. The water-based ink composition for a writing instrument according to claim 4, wherein the aluminum content of the ink reservoir is 1 to 5 mass% based on the total amount of elements having atomic numbers 11 to 92 detected when the ink reservoir is measured with an elemental analyzer.

6. The ink reservoir has the following elemental composition based on the total amount of elements having atomic numbers 11 to 92 detected when the ink reservoir is measured with an elemental analyzer: Aluminum 1 to 5 mass% Calcium 38-48% by mass Silicon 40 to 50 mass% The aqueous ink composition for a writing instrument according to claim 4, wherein the composition comprises:

7. 7. A water-based ink product comprising the water-based ink composition for a writing instrument according to claim 1 contained in a glass ink reservoir.

8. A method for inhibiting precipitation in an aqueous ink composition for a writing instrument, which contains water and an acid dye having a fluorescein skeleton and is to be contained in an aluminum-containing glass ink reservoir, comprising: The coexistence of an acid dye having a fluorescein skeleton and an organophosphorus chelating agent having two phosphonic acid groups A method comprising:

9. Use of a composition containing an organophosphorus chelating agent having two phosphonic acid groups for inhibiting precipitation in an aqueous ink composition for a writing instrument to be contained in an aluminum-containing glass ink reservoir, the aqueous ink composition containing water and an acid dye having a fluorescein skeleton.

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