Water-based ink composition for writing implements and writing implements

Abstract

To provide: an aqueous ink composition for a writing instrument which forms a uniform coating with low gloss and has superior abrasion resistance and water-resistant adhesion even when used to write on a non-absorbent surface; and a writing instrument.SOLUTION: An aqueous ink composition for a writing instrument comprises at least: a color material; a neutralized isobutylene / maleic anhydride copolymer; a water-soluble resin and / or resin emulsion; and water. The acid value of resin in the water-soluble resin and / or resin emulsion is 240 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous ink composition for a writing instrument, which forms a low-gloss, uniform coating film, and has excellent abrasion resistance and water-resistant adhesion even when written on a non-absorbent surface, and to a writing instrument. [Background technology]

[0002] Conventional aqueous ink compositions for writing instruments and the like that have good abrasion resistance, water-resistant adhesion, etc. include, for example: [1] A water-based ink containing a colorant aqueous solution prepared by dissolving a hydrophobic colorant selected from hydrophobic dyes or easily solvent-soluble pigments in a hydrophobic resin containing an acidic group, and dissolving or dispersing the hydrophobic resin in water as a water-soluble salt with an alkaline substance, wherein the hydrophobic colorant is contained in an amount of 0.5 to 10 wt % of the total ink composition, the weight ratio of the hydrophobic colorant to the hydrophobic resin is in the range of 1:5 to 5:1, and the degree of neutralization of the hydrophobic resin containing an acidic group with alkali is 0.1 or more (see, for example, Patent Document 1). [2] A water-based ink composition for glass and ceramic surfaces, which contains an acrylic silicone resin emulsion, a pigment, a dispersant, and an aqueous solvent, in order to provide an ink that has excellent properties such that the handwriting has sufficient water resistance, warm water resistance, and abrasion resistance even when written on the surface of glass or ceramic (see, for example, Patent Document 2); [3] A water-based ink composition for a writing instrument, which is excellent in fixation and follow-up fixation on a non-permeable medium, as well as in the prevention of hard caking of glitter pigment particles and in redispersibility, is characterized by comprising water, glitter pigment particles, a wetting dispersant having an acid value and an amine value, and an elastic polymer (see, for example, Patent Document 3). etc. are known.

[0003] However, the aqueous ink compositions for writing instruments and the like described in Patent Documents 1 to 3 above still have insufficient abrasion resistance, water-resistant adhesion, and the like when written on a non-absorbent surface, and there is currently a strong demand for aqueous ink compositions for writing instruments and writing instruments that form a low-gloss, uniform coating film and are excellent in abrasion resistance, water-resistant adhesion, and the like even when written on a non-absorbent surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP-A-9-143410 (claims, examples, etc.) [Patent Document 2] JP 2014-105282 A (claims, examples, etc.) [Patent Document 3] JP 2019-119855 A (claims, examples, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned problems and current state of the prior art, and aims to solve these problems, and to provide an aqueous ink composition for a writing instrument, which forms a low-gloss, uniform coating film, and has excellent abrasion resistance, water-resistant adhesion, etc., even when written on a non-absorbent surface, and a writing instrument. [Means for solving the problem]

[0006] In view of the above-mentioned problems in the prior art, the present inventors have conducted extensive research and have found that the above-mentioned objective aqueous ink composition for a writing instrument and writing instrument can be obtained by containing at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or a resin emulsion, and water, and by adjusting the acid value of the resin in the water-soluble resin and resin emulsion to a predetermined value or less, thereby completing the present invention.

[0007] That is, the aqueous ink composition for a writing instrument of the present invention contains at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or a resin emulsion, and water, and is characterized in that the acid value of the resin in the water-soluble resin and resin emulsion is 240 or less. The neutralized product of the isobutylene-maleic anhydride copolymer preferably has a mass average molecular weight of 3,000 to 400,000. The coloring material is preferably a pigment. The writing instrument of the present invention is characterized by being equipped with the aqueous ink composition for a writing instrument having the above-described configuration. [Effects of the Invention]

[0008] According to the present invention, there are provided an aqueous ink composition for a writing instrument, which forms a low-gloss, uniform coating film, and which has excellent abrasion resistance, water-resistant adhesion, etc., even when written on a non-absorbent surface, and a writing instrument. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes in detail the embodiments of the present invention. However, please note that the technical scope of the present invention is not limited to the embodiments described in detail below, but extends to the inventions set forth in the claims and their equivalents. Furthermore, the present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field (including design matters and obvious matters).

[0010] <Water-based ink composition for writing instruments> The aqueous ink composition for a writing instrument of the present invention contains at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or a resin emulsion, and water, and is characterized in that the acid value of the resin in the water-soluble resin and resin emulsion is 230 or less.

[0011] <Colorant> The coloring materials that can be used in the present invention include, without limitation, all dyes that dissolve or disperse in water, conventionally known inorganic and organic pigments such as titanium oxide, resin particle pigments containing pigments, pseudo-pigments in which resin emulsions are colored with dyes, white plastic pigments, hollow resin pigments (particles), pigments with a base of silica or mica and a multilayer coating of iron oxide, titanium oxide, etc. on the surface, photoluminescent pigments such as aluminum, thermochromic pigments (particles), photochromic pigments (particles), and composite pigments (particles) of these. Commercially available aluminum pigments that can be used include, for example, the WXM series, in which the aluminum surface has been treated with a phosphorus-based compound for rust prevention; the WL series, in which the aluminum surface has been treated with a molybdenum compound for rust prevention; the EMR series, in which the surface of aluminum flakes has been coated with high-density silica (all manufactured by Toyo Aluminum); and SW-120PM (all manufactured by Asahi Kasei Chemicals Corporation). These can be used alone or in combination of two or more types. When titanium oxide is added, it is desirable to use, for example, alumina or silica, or zirconia or zinc-treated titanium oxide, and it is preferable to use rutile or anatase titanium oxide. Examples of dyes include 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.

[0012] Examples of inorganic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, and nitroso pigments. More specifically, inorganic pigments such as carbon black, titanium black, zinc oxide, 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, barite powder, calcium carbonate, white lead, dark blue, iron blue, manganese violet, aluminum powder, and brass powder; CI Pigment Blue 17, CI Pigment Blue 15, 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 Blue 18, CI Pigment Blue 19, CI Pigment Blue 20, CI Pigment Blue 21, CI Pigment Blue 22, CI Pigment Red 38, CI Pigment Red 48, CI Pigment Red 49, CI Pigment Red 53, CI Pigment Red 57, CI Pigment Blue 19, CI Pigment Blue 23, CI Pigment Blue 24, CI Pigment Blue 25, CI Pigment Blue 26, CI Pigment Blue 27, CI Pigment Red 5, CI Pigment Red 28, CI Pigment Red 39, CI Pigment Red 49, CI Pigment Red 54, CI Pigment Red 55, CI Pigment Red 56, CI Pigment Red 57, CI Pigment Blue 19, CI Pigment Blue 28, CI Pigment Blue 29, CI Examples of pigments that can be used include 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, 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.

[0013] Examples of thermochromic pigments (particles) include thermochromic pigments 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 can control the color change temperature when the leuco dye and color developer develop color, so that the resulting particles have a predetermined average particle size (e.g., 0.1 to 7 μm). Examples of photochromic pigments (particles) include photochromic particles composed of at least one selected from photochromic dyes (compounds), fluorescent dyes, etc., and a resin such as a terpene phenol resin, and photochromic pigments (particles) produced by microencapsulating a photochromic composition containing at least one selected from photochromic dyes (compounds), fluorescent dyes, etc., an organic solvent, and additives such as an antioxidant, a light stabilizer, and a sensitizer, so as to have a predetermined average particle diameter (for example, 0.1 to 7 μm). In the present invention (including the examples), the "average particle size" refers to the D50 value calculated on a volume basis using a particle size distribution analyzer HR9320-X100 (manufactured by Nikkiso Co., Ltd.), or the average particle size value calculated by the cumulant method analysis in the scattering intensity distribution using a concentrated particle size analyzer FPAR-1000 (Otsuka Electronics Co., Ltd.) using dynamic light scattering.

[0014] These coloring materials can be used either alone or in combination of two or more (hereinafter simply referred to as "at least one"). Furthermore, with these colorants, in terms of further reducing the gloss of the coating film and making the coating film uniform, it is desirable to use pigments, that is, colored resin pigments such as the above-mentioned inorganic pigments, organic pigments, resin particle pigments containing pigments, or pseudo-pigments made by coloring resin emulsions with dyes, white plastic pigments, hollow resin pigments (particles), pigments with a base of silica or mica and a surface layer multi-coated with iron oxide, titanium oxide, or the like, photoluminescent pigments such as aluminum, thermochromic pigments (particles), photochromic pigments (particles), and composite pigments (particles) of these.

[0015] The (total) content of these coloring materials is preferably 0.5 to 50% by mass, more preferably 2 to 40% by mass, and particularly preferably 5 to 30% by mass, based on the total amount of the aqueous ink composition for writing instruments (hereinafter simply referred to as "total amount of ink composition"). By setting the content of this coloring material to 0.5% by mass or more, it is possible to achieve low gloss and uniformity in the coating film, thereby realizing the formation of a more beautiful coating film, while by setting it to 50% by mass or less, it is possible to suppress an increase in viscosity and improve the fluidity of the ink, which is preferable.

[0016] The neutralized isobutylene-maleic anhydride copolymer used in this invention is a neutralized copolymer of isobutylene and maleic anhydride, and in this invention, when used in combination with a water-soluble resin (including a resin emulsion) described below, it forms a low-gloss, uniform coating film and is a component that exhibits the functions of improving abrasion resistance and water-resistant adhesion. The basic structure of the neutralized isobutylene-maleic anhydride copolymer used is represented by the following formula (I), and the following formula (II) represents an ammonia-neutralized (modified) isobutylene-maleic anhydride copolymer that can be preferably used in the present invention.

[0017] [ka]

[0018] [ka]

[0019] In the present invention, in addition to the ammonia-neutralized product of formula (II), sodium hydroxide-neutralized products and amine-neutralized products may also be used. The values ​​of n in formula (I), l and m in formula (II), and j and k in formula (III) vary depending on the weight-average molecular weight, which will be described later, and the preferred ranges are determined. In addition, in the present invention, the copolymer may be a neutralized product obtained by imidizing (imide-modifying) an isobutylene-maleic anhydride copolymer, which is represented by the following formula (III), and neutralizing the imidized isobutylene-maleic anhydride copolymer with ammonia, sodium hydroxide, an amine, or the like. [ka]

[0020] The weight average molecular weight of each neutralized product of the isobutylene-maleic anhydride copolymer of the above formulas (II), (III), etc. is preferably 3,000 to 400,000, more preferably 5,000 to 200,000, most preferably 30,000 to 100,000, and most preferably 50,000 to 70,000. In the present invention, the "weight average molecular weight" is a value calculated in terms of polystyrene by aqueous gel permeation chromatography (GPC) analysis. The isobutylene-maleic anhydride copolymer and its neutralized products can be commercially available products, such as "ISOBAM" manufactured by Kuraray Co., Ltd. ISOBAM-104 and ISOBAM-110 are commercially available ammonia-neutralized (modified) products of the isobutylene-maleic anhydride copolymer of formula (II) above. When preparing a neutralized product of the isobutylene-maleic anhydride copolymer (from formula (I) above, etc.), for example, if all the carboxyl groups of the isobutylene-maleic anhydride copolymer are neutralized, the degree of neutralization is set to 1, and each neutralized product can be obtained by calculating and preparing the necessary amounts of ammonia, sodium hydroxide, amine, etc. for neutralization.

[0021] The content of the neutralized isobutylene-maleic anhydride copolymer is preferably 0.01 to 4 mass %, more preferably 0.05 to 3 mass %, and particularly preferably 0.1 to 2 mass %, based on the total amount of the ink composition. If the content of the neutralized isobutylene-maleic anhydride copolymer is less than 0.01% by mass, the gloss of the coating film cannot be suppressed sufficiently, resulting in a glossy appearance and making it impossible to achieve low gloss. On the other hand, if the content exceeds 4% by mass, the viscosity increases, reducing ink ejection properties and adversely affecting writing performance, and further increasing costs.

[0022] The water-soluble resin and resin emulsion used in the present invention have an acid value of 240 or less, and by using a resin with this characteristic, it functions as a fixing agent, dispersant, and stabilizer. The water-soluble resins and resin emulsions that can be used are not particularly limited as long as the acid value of the resin is 240 or less, and examples thereof include at least one selected from water-soluble resins having a hydrophobic moiety in the molecule, such as polyacrylic acid, acrylic resins, water-soluble styrene-acrylic resins, water-soluble styrene-maleic acid resins, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resins, water-soluble styrene resins, water-soluble ester-acrylic resins, ethylene-maleic acid copolymers, polyethylene oxide, and water-soluble urethane resins, which have an acid value of 240 or less; and resin emulsions such as acrylic emulsions, vinyl acetate emulsions, urethane emulsions, styrene-butadiene emulsions, styrene-acrylonitrile emulsions, silicone resin emulsions, and silicone-acrylic copolymer emulsions.

[0023] Preferably, from the viewpoints of dispersibility of the colorant, viscosity adjustment, and fixing power improvement, it is desirable to use a water-soluble resin such as an acrylic resin, a water-soluble styrene-acrylic resin, a styrene-maleic acid resin, or a urethane resin, or an acrylic resin emulsion, a styrene-acrylic resin, a styrene-maleic acid resin, or a urethane resin emulsion, all of which have an acid value of 240 or less. Note that, from the viewpoint of storage stability of the ink, the lower limit of the acid value is desirably 10 or more. By adjusting the acid value of the resin to 240 or less, it is possible to form a coating film with even lower gloss and uniformity.

[0024] The mass average molecular weight of the resin having an acid value of 240 or less is preferably 2,000 or more, more preferably 3,000 to 300,000, and particularly preferably 5,000 to 200,000. By using a resin having a mass average molecular weight of 2,000 or more, it is possible to further improve abrasion resistance and water-resistant adhesion. In the present invention, the "acid value of a resin" represents the number of mg of KOH required to neutralize 1 g of resin, and is a value measured in accordance with, for example, JIS-K3054.

[0025] The water-soluble resins and resin emulsions having an acid value of 240 or less can be commercially available products. For example, water-soluble resins such as BASF PDX6157 (acid value: 205), JDX6500 (acid value: 85), and PDX-6137A (acid value: 240), and Seiko PMC M-30 (acid value: 155) can be used. Resin emulsions such as BASF PDX-7741 (acid value: 52), PDX-7787 (acid value: 100), and PDX-7158 (acid value: 54), Taisei Fine Chemical WBR-016 (acid value: 7), and Mitsui Chemicals MC Takelac W-5661 (acid value: 48) can be used.

[0026] The content (total: solid content) of the water-soluble resin and resin emulsion having these properties is preferably 0.1 to 20% by mass, and more preferably 0.5 to 15% by mass, based on the total amount of the ink composition. If the content of water-soluble resin or resin emulsion with these characteristics is less than 0.1% by mass, the quality of the drawn lines will deteriorate, including a decrease in abrasion resistance. On the other hand, if it exceeds 20% by mass, the viscosity will increase, resulting in a deterioration in ink ejection properties.

[0027] The aqueous ink composition for a writing instrument of the present invention contains at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or a resin emulsion, and water, in which the acid value of the water-soluble resin and the resin emulsion is 240 or less, and the remainder is water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as a solvent.In addition, the composition may contain appropriate additives such as polyhydric alcohols, dispersants, lubricants, pH adjusters, thickeners, synthetic polymers, rust inhibitors, preservatives or antibacterial agents, thickeners, etc., within limits that do not impair the effects of the present invention.

[0028] Examples of polyhydric alcohols that can be used include at least one of ethylene glycol, diethylene glycol, 1,2-propylene glycol, dipropylene glycol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 1,6-hexanediol, and cyclohexanedimethanol.

[0029] Usable dispersants include nonionic and anionic surfactants and water-soluble resins, with water-soluble polymers being preferred. Examples of lubricants include nonionic lubricants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic lubricants such as alkyl sulfonates and alkyl aryl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorine-based surfactants; and polyether-modified silicones.

[0030] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonate or phosphate such as sodium tripolyphosphate and sodium carbonate, and hydrates of alkali metals such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of preservatives or antibacterial agents include phenol, sodium omadine, sodium benzoate, and benzimidazole compounds. Examples of thickeners that can be used include cellulose derivatives, such as hydroxyalkyl cellulose, carboxymethyl cellulose (CMC) or salts thereof, fermented cellulose, crystalline cellulose, polysaccharides, etc. Examples of polysaccharides that can be used include xanthan gum, guar gum, hydroxypropylated guar gum, casein, gum arabic, gelatin, amylose, agarose, agaropectin, arabinan, curdlan, callose, carboxymethyl starch, chitin, chitosan, quince seed, glucomannan, gellan gum, tamarind seed gum, dextran, nigeran, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkaloid gum, succinoglycan, locust bean gum, and tara gum. Examples of synthetic polymers include polyacrylic acids, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, bisacrylamide methyl ether, polyacrylamide, polyethyleneimine, polyethylene glycol, polydioxolane, polystyrene sulfonic acid, and polypropylene oxide. These may be used alone or in combination of two or more. If commercially available products of these are available, they may be used.

[0031] The aqueous ink composition for a writing instrument of the present invention is prepared by appropriately combining at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or resin emulsion having an acid value of 240 or less, water, and other components depending on the intended use of the ink for the writing instrument (for a ballpoint pen, a marking pen, etc.), stirring and mixing the combined components with an agitator such as a homomixer, homogenizer, or disper, and, if necessary, further removing coarse particles from the ink composition by filtration or centrifugation, thereby obtaining an aqueous ink composition for a writing instrument with excellent color development. Furthermore, the pH (25°C) of the aqueous ink composition for a writing instrument of the present invention is preferably adjusted to 5 to 10 using a pH adjuster or the like, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, and more preferably 6 to 9.5.

[0032] The aqueous ink composition for writing instruments of the present invention, which is configured in this manner, contains at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a water-soluble resin and / or a resin emulsion, and water, wherein the water-soluble resin and the resin emulsion contain resins with an acid value of less than 240. The combination of this low acid value property improves adhesion to the substrate, resulting in an aqueous ink composition for writing instruments which forms a low-gloss, uniform coating film and has excellent abrasion resistance and water-resistant adhesion properties, even when written on a non-absorbent surface.

[0033] <Writing instruments> The writing instrument of the present invention is equipped with an aqueous ink composition for a writing instrument having the above-described characteristics, and forms a low-gloss, uniform coating film, resulting in a writing instrument that has excellent abrasion resistance, water-resistant adhesion, etc., even when written on a non-absorbent surface. As a writing instrument, for example, it is mounted on a ballpoint pen, marking pen, or the like having a pen tip portion such as a ballpoint tip, fiber tip, felt tip, plastic tip, fiber core, or porous core.

[0034] In this invention, a "marking pen" refers to a pen that has a mechanism for supplying ink stored in an ink reservoir to a resin writing part by capillary action, and includes pens referred to as "sign pens." Also, a "ballpoint pen" refers to a pen that has a mechanism for causing ink stored in an ink reservoir to seep out by the rotation of a ball provided in the writing part. For a ballpoint pen, the aqueous ink composition for a writing instrument having the above-described composition is contained in a ballpoint pen ink container (refill) equipped with a ball having a diameter of 0.18 to 2.0 mm, and an ink follower is added. The ink follower is a liquid that is incompatible with the aqueous ink composition for a writing instrument having the above-described characteristics contained in the ink container and has a lower specific gravity than the aqueous ink composition, such as polybutene, silicone oil, or mineral oil. The structure of the ballpoint pen, marking pen, etc. is not particularly limited, and may be, for example, a direct ink ballpoint pen or marking pen having a collector structure (ink retention mechanism) in which the barrel itself serves as an ink container and is filled with the aqueous ink composition for a writing instrument having the above-described configuration. [Example]

[0035] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0036] [Examples 1 to 6 and Comparative Examples 1 to 3] Each aqueous ink composition for a writing instrument was prepared by a conventional method using the formulation shown in Table 1. The pH of each aqueous ink composition for a writing instrument at room temperature (25°C) was measured using a pH meter (manufactured by HORIBA Corporation) and was found to be within the range of 7.9 to 8.2. Each of the aqueous ink compositions for writing instruments obtained above was used to write on a writing instrument ( Water-based A felt-tip pen was prepared and the low gloss and uniformity of the coating film, abrasion resistance, and water adhesion resistance were evaluated using the following evaluation methods. The results are shown in Table 1 below.

[0037] (Making a felt-tip pen) Each ink composition obtained above was used to prepare a felt-tip pen. Specifically, the barrel of a felt-tip pen (manufactured by Mitsubishi Pencil Co., Ltd., product name: PM-120T) was used, and each ink composition was loaded into the felt-tip pen, which was made of recycled PP resin as the barrel material and a (fine) PET fiber and (ultrafine) POM resin as the core. Each evaluation was carried out using the resulting felt-tip pens of Examples 1 to 5 and Comparative Examples 1 to 4.

[0038] (Method for evaluating low gloss and uniformity of coating film) A coating film was hand-painted onto a 2 cm x 2 cm area of ​​PET film and subjected to visual sensory evaluation according to the following evaluation criteria. <Evaluation criteria> A: The coating has no gloss and has a sufficiently low gloss. B: The coating has a slight glossiness, and the low gloss is somewhat weak. C: The coating has a glossy finish

[0039] (Method for evaluating scratch resistance) Five circles, each 15 mm in diameter, were handwritten in succession on a PET film. After five minutes, a Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) was placed on the drawn lines, and then a 500 g weight was placed on top and rubbed five times. The results were evaluated according to the following criteria. <Evaluation criteria> A: No change from before rubbing. B: There are some areas where the lines have become thinner compared to before rubbing. C: Compared to before rubbing, the drawn line is thinner across the entire line.

[0040] (Method for evaluating water-resistant adhesion) In an environment with a temperature of 25°C and humidity of 65%, a five-layer spiral, 15 mm wide, was drawn eight times on a PET film, and tap water was sprayed from the nozzle of a commercially available shower at a flow rate of 12 liters per minute. The state of the drawn lines was then observed and evaluated according to the following criteria (n=10). <Evaluation criteria> A: No change in the lines is observed. B: The hue of the lines has become slightly lighter, or some of the lines are missing. C: The hue of the lines has become significantly lighter, or half or most of the lines have been erased. D: Some of the color and shape of the lines remain, but it is difficult to imagine the original shape. E: All the lines have run away and disappeared.

[0041] [Table 1]

[0042] As is clear from the results in Table 1 above, the aqueous ink compositions for writing instruments of Examples 1 to 6 according to the present invention formed a coating film with low gloss and uniformity, and were superior in abrasion resistance and water-resistant adhesion, even when written on a non-absorbent surface, compared to the aqueous ink compositions for writing instruments of Comparative Examples 1 to 3, which are outside the scope of the present invention. [Industrial Applicability]

[0043] The ink composition can be suitably used in aqueous ink compositions for writing instruments such as ballpoint pens and marking pens.

Claims

1. The aqueous ink composition for a writing instrument comprises at least 0.5 to 30% by mass of a colorant, 0.01 to 4% by mass of a neutralized product of an isobutylene-maleic anhydride copolymer having a mass-average molecular weight of 3,000 to 200,000, 0.1 to 20% by mass of a water-soluble resin and / or resin emulsion in terms of solid content, and water, wherein the acid value of the resin in the water-soluble resin and resin emulsion is 240 or less and the mass-average molecular weight is 2,000 to 200,000.

2. 2. The aqueous ink composition for a writing instrument according to claim 1, wherein the neutralized product of the isobutylene-maleic anhydride copolymer has a mass average molecular weight of 5,000 to 200,000.

3. 3. The aqueous ink composition for a writing instrument according to claim 1, wherein the coloring material is a pigment.

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

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