Water-based ink composition for writing instruments and writing instruments

Abstract

To provide an aqueous ink composition for writing instruments that forms a uniform coating with low glossiness, and even when writing is performed on non-absorbing surface, is excellent in scratch resistance and waterproof sticking properties, and a writing instrument.SOLUTION: An aqueous ink composition for writing instruments of the present invention comprises at least a coloring material, a neutralized isobutylene / maleic anhydride copolymer, a polyol having two or more OH groups, an aqueous resin and / or a resin emulsion, and water.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition for writing instruments and a writing instrument that form a low-gloss and uniform coating film and are excellent in abrasion resistance and water-fast fixing property even when written on a non-absorbent surface.

Background Art

[0002] Conventionally, as an aqueous ink composition for writing instruments or the like that has good abrasion resistance, water-fast fixing property, etc., for example, 〔1〕 An aqueous ink containing an aqueous solution of a colorant in which a hydrophobic resin containing an acidic group in which a hydrophobic colorant selected from a hydrophobic dye or a solvent-soluble pigment is dissolved is dissolved or dispersed in water as a water-soluble salt with an alkaline substance, wherein the hydrophobic colorant is contained in the range of 0.5 to 10 wt% with respect to the whole 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 an alkali is 0.1 or more (for example, see Patent Document 1), 〔2〕 An aqueous ink composition for glass and pottery surfaces containing an acrylic silicone-based resin emulsion, a pigment, a dispersant, and an aqueous solvent in order to provide an ink having properties such that its handwriting is sufficiently excellent in water resistance, hot water resistance, and abrasion resistance even when written on the surface of glass or pottery (for example, see Patent Document 2), 〔3〕 An aqueous ink composition for writing instruments containing water, a fluorescent pigment particle, a wetting dispersant having an acid value and an amine value, and an elastic polymer in order to provide an aqueous ink composition for writing instruments excellent in fixing property, follow-up fixing property with respect to a non-permeable writing object, and anti-hard caking property and redispersibility of fluorescent pigment particles (for example, see Patent Document 3) etc. are known.

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

[0004] [Patent Document 1] Japanese Patent Publication No. 9-143410 (Claims, Examples, etc.) [Patent Document 2] Japanese Patent Publication No. 2014-105282 (Claims, Examples, etc.) [Patent Document 3] Japanese Patent Publication No. 2019-119855 (Claims, Examples, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0005] In view of the problems and current status of the above-mentioned prior art, the present invention aims to solve these problems and provides an aqueous ink composition and writing instrument for writing instruments that forms a low-gloss, uniform coating film and exhibits excellent abrasion resistance, water adhesion resistance, etc., even when writing on non-absorbent surfaces. [Means for solving the problem]

[0006] In view of the above-mentioned conventional problems, the inventors conducted diligent research and found that an aqueous ink composition for writing instruments and a writing instrument for the above-mentioned purpose can be obtained by including at least a colorant, a neutralized copolymer of specific physical properties, a polyol having two or more OH groups, a water-soluble resin and / or a resin emulsion, and water, thus completing the present invention.

[0007] In other words, the aqueous ink composition for writing instruments of the present invention is characterized by comprising at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and / or a resin emulsion, and water. It is preferable that the mass-average molecular weight of the neutralized product of the isobutylene-maleic anhydride copolymer is 3,000 to 400,000. Preferably, the colorant is a pigment. The writing instrument of the present invention is characterized by incorporating the aqueous ink composition for writing instruments having the above-described configuration. [Effects of the Invention]

[0008] According to the present invention, an aqueous ink composition for writing instruments and a writing instrument are provided that have low gloss, form a uniform coating film, and exhibit excellent abrasion resistance, water adhesion resistance, and other properties even when writing on a non-absorbent surface. The object and effect of the present invention are recognized and obtained, in particular, by using the components and combinations indicated in the claims. Both the general description above and the detailed description below are illustrative and descriptive, and do not limit the present invention as described in the claims. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below. However, it should be noted that the technical scope of the present invention is not limited to the embodiments detailed below, but extends to the invention described in the claims and its equivalents. Furthermore, the present invention can be implemented based on the contents disclosed herein and common technical knowledge in the art (including design matters and obvious matters).

[0010] <Water-based ink composition for writing instruments> The aqueous ink composition for writing instruments of the present invention is characterized by comprising at least a colorant, a neutralized product of an isobutylene-maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and / or a resin emulsion, and water.

[0011] <Colorants> The colorants used in this invention can be any of the following without limitation: all dyes that dissolve or disperse in water, conventionally known inorganic and organic pigments such as titanium dioxide, resin particle pigments containing pigments, pseudo-pigments obtained by coloring resin emulsions with dyes, white plastic pigments, hollow resin pigments (particles), pigments with silica or mica as a base material and a multi-layer coating of iron oxide or titanium dioxide on the surface, luminous pigments such as aluminum pigments, thermochromic pigments (particles), photochromic pigments (particles), and composite pigments (particles) thereof. Examples of commercially available aluminum pigments that can be used include the WXM series, in which the aluminum surface is rust-preventively treated with a phosphorus-based compound; the WL series, in which the aluminum surface is rust-preventively treated with a molybdenum compound; the EMR series, in which the surface of aluminum flakes is coated with high-density silica (all manufactured by Toyo Aluminum Co., Ltd.); SW-120PM (all manufactured by Asahi Kasei Chemicals Co., Ltd.); and others. These can be used individually or in mixtures of two or more. Furthermore, when titanium dioxide is added, it is preferable to use, for example, alumina or silica, or zirconia or zinc-treated titanium dioxide, and it is preferable to use rutile-type or anatase-type titanium dioxide. Examples of dyes include acid dyes such as eosin, foxine, 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 yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, lead yellow, molybdide orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, barite powder, calcium carbonate, lead white, navy blue, navy blue, manganese violet, aluminum powder, brass powder, etc., CI Pigment Blue 17, CI Pigment Blue 15, CI Pigment Blue 17, CI Pigment Blue 27, CI Pigment Red 5, CI Pigment Red 22, CI Pigment Red 38, CI Pigment Red 48, CI Pigment Red 49, CI Pigment Red 53, CI Pigment Red 57, C Examples include I 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, CI Pigment Green 7, etc.

[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 developer, a color developer that has the ability to cause the leuco dye to develop color, and a color change temperature adjuster that can control the color change temperature in the color development of the leuco dye and the color developer, so that the composition has a predetermined average particle size (for example, 0.1 to 10 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, or 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 antioxidants, light stabilizers, and sensitizers, to a predetermined average particle size (e.g., 0.1 to 10 μm). In this invention (including the examples), the "average particle diameter" is a value measured by laser diffraction or dynamic light scattering. In the case of laser diffraction, it is the D50 value calculated on a volume basis. This measurement can be performed using, for example, the particle diameter distribution analyzer HRA9320-X100 from Nikkiso Co., Ltd. The average particle diameter using dynamic light scattering is, for example, the average particle diameter value of the cumulant method analysis in the scattering intensity distribution calculated using the concentrated particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.).

[0014] These colorants can be used individually or in combination of two or more (hereinafter simply referred to as "at least one"). In these colorants, from the viewpoints of further reducing the gloss of the coating film and the uniformity of the coating film, the use of pigments, that is, the above-mentioned inorganic pigments, organic pigments, resin particle pigments containing pigments or pseudo-pigments obtained by coloring resin emulsions with dyes, etc., coloring resin pigments, white plastic pigments, hollow resin pigments (particles), pigments having a base material of silica or mica and a multi-layer coating of iron oxide, titanium oxide, etc. on the surface layer, bright pigments such as aluminum pigments, thermochromic pigments (particles), photochromic pigments (particles), etc., and the use of composite pigments (particles) thereof are desirable.

[0015] The (total) content of these colorants is preferably 0.5 to 50% by mass, more preferably 2 to 40% by mass, and particularly preferably 5 to 30% by mass with respect to 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 colorant to 0.5% by mass or more, the low glossiness and uniformity of the coating film can be exhibited, and the formation of a more beautiful coating film can be realized. On the other hand, by setting it to 50% by mass or less, an increase in viscosity can be suppressed, and the fluidity of the ink becomes good, which is preferable.

[0016] The neutralized product of the isobutylene / maleic anhydride copolymer used in the present invention is a neutralized product of a copolymer of isobutylene and maleic anhydride, and in the present invention, when used in combination with a water-soluble resin (including resin emulsion) described later, it becomes a component that exhibits functions of making the coating film have low glossiness, forming the coating film uniformly, and having good abrasion resistance and water-fast fixing properties. In the neutralized product of the isobutylene / maleic anhydride copolymer to be used, the basic structure of the isobutylene / maleic anhydride copolymer is represented by the following formula (I), and the following formula (II) is an ammonia neutralized product (modified product) of the isobutylene / maleic anhydride copolymer that can be preferably used in the present invention.

[0017]

Chemical formula

[0018] [ka] Formula (II)

[0019] In this invention, in addition to the ammonia neutralized product of formula (II) above, sodium hydroxide neutralized product and amine neutralized product may also be used. Furthermore, the values ​​of n in formula (I), l and m in formula (II), and j and k in formula (III) below vary depending on the weight-average molecular weight described later, and a suitable range is determined. Furthermore, in the present invention, the isobutylene-maleic anhydride copolymer may also be neutralized by neutralizing the imidized isobutylene-maleic anhydride copolymer represented by the following formula (III) with ammonia, sodium hydroxide, amine, etc. [ka] Formula (III)

[0020] The weight-average molecular weight of each neutralized product obtained by neutralizing the isobutylene-maleic anhydride copolymers of the above formulas (II) and (III) is preferably 3,000 to 400,000, more preferably 5,000 to 200,000, 30,000 to 100,000, and most preferably 50,000 to 70,000. This weight-average molecular weight is the polystyrene equivalent value obtained by aqueous gel permeation chromatography (GPC) analysis. The isobutylene-maleic anhydride copolymers and their neutralized products can be commercially available products. For example, "Isoban" manufactured by Kuraray Co., Ltd. can be used. Examples include the neutralized products of Isoban-04, 06, 10, and 18, and Isoban-104 and 110, which are commercially available ammonia neutralized (modified) products of the isobutylene-maleic anhydride copolymer in formula (II) above. Furthermore, neutralized products of Isoban-304, 306, and 310 can also be used. When preparing the neutralized products of the isobutylene-maleic anhydride copolymers used (from formula (I) above, etc.), for example, if all carboxyl groups of the isobutylene-maleic anhydride copolymer are neutralized, the degree of neutralization is considered to be 1, and the necessary amounts of ammonia, sodium hydroxide, amine, etc. used for neutralization are calculated and prepared to obtain each neutralized product.

[0021] The content of these neutralized isobutylene-maleic anhydride copolymers is preferably 0.01 to 4% by mass, more preferably 0.05 to 3% by mass, and particularly preferably 0.1 to 2% by 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, resulting in a glossy finish and preventing the achievement of a low-gloss finish. On the other hand, if it exceeds 4% by mass, the viscosity increases, reducing ink ejection and negatively impacting writing performance, as well as leading to increased costs.

[0022] Examples of polyols having two or more OH groups used in the present invention include 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, cyclohexanedimethanol, glycerin, and sugar alcohols. Examples of sugar alcohols include disaccharide alcohols such as isomaltitol, maltitol, and lactitol; trisaccharide alcohols such as maltotriitol, isomalttriitol, and panitol; tetrasaccharide or higher sugar alcohols such as oligosaccharide alcohols; and at least one of reduced starch saccharified products and reduced starch hydrolysates made from disaccharide or higher sugar alcohols.

[0023] The content of polyols having two or more OH groups is preferably 0.05 to 40% by mass, more preferably 0.1 to 30% by mass, and particularly preferably 0.5 to 20% by mass, based on the total amount of the ink composition. If the content of polyols having two or more OH groups is less than 0.05% by mass, the drying of the coating surface proceeds rapidly, making it easy for uneven lines to occur and preventing the formation of a uniform coating. On the other hand, if it exceeds 40% by mass, the drying properties deteriorate, making it difficult to obtain low-gloss lines.

[0024] The water-soluble resins and resin emulsions used in the present invention function as fixatives, dispersants, and stabilizers, and include, for example, at least one selected from water-soluble resins having hydrophobic parts in their molecules, 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, as well as resin emulsions such as acrylic emulsions, vinyl acetate emulsions, polyolefin emulsions, urethane emulsions, styrene-butadiene emulsions, styrene-acrylonitrile emulsions, silicone resin emulsions, and silicone-acrylic copolymer emulsions. Preferably, from the viewpoint of dispersibility of the colorant, viscosity adjustment, and improved fixing strength, it is preferable to use the above-mentioned water-soluble resins and resin emulsions having a glass transition temperature (Tg) of 120°C or lower. More preferably, it is desirable to use resin emulsions such as acrylic resins, water-soluble styrene-acrylic resins, styrene-maleic acid, water-soluble urethane resins, or acrylic resin emulsions, all having a glass transition temperature (Tg) of 120°C or lower. The lower limit of the glass transition temperature (Tg) is preferably -50°C or higher from the viewpoint of line quality such as low gloss and abrasion resistance. By setting the glass transition temperature (Tg) of the above resin to 120°C or lower, cracking on the coating surface can be further suppressed, and abrasion resistance and water adhesion resistance can be further improved. In this invention, the "glass transition temperature" is the Tg measured in accordance with JIS K7121, for example, using a Rigaku thermo plus evo DSC8230 (manufactured by Rigaku Corporation).

[0025] The above-mentioned water-soluble resins and resin emulsions can be commercially available products. For example, for water-soluble resins, BASF's Joncryl JDX6500 (Tg: 65℃), JDX6180 (Tg: 134℃), 52J (Tg: 56℃), 70J (Tg: 102℃), and PDX-6137A (Tg: 102℃) can be used. For resin emulsions, BASF's Joncryl PDX352D (Tg: 52℃), PDX7199 (Tg: 88℃), PDX7537 (Tg: -4℃), or Seikoh PMC's KE-1062 (96℃) and PE-1304 (Tg: 9℃) can be used.

[0026] The total solid content of these water-soluble resins and resin emulsions is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and particularly preferably 1 to 10% by mass, relative to the total amount of the ink composition. If the content of this water-soluble resin or resin emulsion is less than 0.1% by mass, it will result in a deterioration of line quality, such as reduced abrasion resistance. On the other hand, if it exceeds 20% by mass, the viscosity will increase, resulting in a deterioration of ink ejection performance.

[0027] The aqueous ink composition for writing instruments of the present invention contains at least the above-mentioned colorant, a neutralized isobutylene-maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and / or resin emulsion, and as a remainder, water as a solvent (tap water, purified water, distilled water, deionized water, pure water, etc.), as well as dispersants, lubricants, pH adjusters, rust inhibitors, preservatives or antibacterial agents, thickeners, etc., to the extent that they do not impair the effects of the present invention.

[0028] Suitable dispersants include nonionic and anionic surfactants and water-soluble resins. Water-soluble polymers are preferred. Examples of lubricants include nonionic compounds such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, higher polyoxyalkylene fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic compounds such as alkyl sulfonates and alkyl allyl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorinated surfactants; and polyether-modified silicones.

[0029] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonic acid and phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitride, and saponins, while examples of preservatives or antibacterial agents include phenol, sodium omazine, sodium benzoate, and benzimidazole compounds. As a thickening agent, for example, cellulose derivatives can be used, such as hydroxyalkylcellulose, carboxymethylcellulose (CMC) or its salts, fermented cellulose, crystalline cellulose, and polysaccharides. 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, nigellan, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkaci 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 can be used individually or in combination of two or more. Alternatively, commercially available versions of these products can be used.

[0030] The aqueous ink composition for writing instruments of the present invention is obtained by appropriately combining at least the above-mentioned colorant, a neutralized isobutylene-maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and / or resin emulsion, water, and other components according to the application of the ink for writing instruments (for ballpoint pens, marking pens, etc.), and stirring and mixing them with a stirrer such as a homomixer, homogenizer, or disper, and further removing coarse particles from the ink composition by filtration or centrifugation as necessary, thereby obtaining an aqueous ink composition for writing instruments with excellent color development. Furthermore, the pH (at 25°C) of the aqueous ink composition for writing instruments of the present invention is preferably adjusted to 5 to 10 using a pH adjuster or the like, and more preferably to 6 to 9.5, from the viewpoint of usability, safety, stability of the ink itself, and compatibility with the ink container.

[0031] The aqueous ink composition for writing instruments of the present invention, configured in this manner, comprises at least the above-mentioned colorant, This composition contains a neutralized isobutylene-maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and / or resin emulsion, and water. During the drying process, aggregation of the colorant and resin occurs, forming irregularities on the surface of the coating film. However, by adding the polyol, aggregation due to the evaporation of water is mitigated, promoting uniform, loose aggregation. As a result, a low-gloss, uniform coating film is formed, and an aqueous ink composition for writing instruments with excellent abrasion resistance and water adhesion resistance is obtained, even when writing on non-absorbent surfaces.

[0032] <Writing instruments> The writing instrument of the present invention incorporates an aqueous ink composition for writing instruments having the above-described characteristics, resulting in a low-gloss, uniform coating film that provides excellent scratch resistance, water-resistant properties, and adhesion even when writing on non-absorbent surfaces. As writing instruments, they are incorporated into ballpoint pens, marking pens, and other writing instruments equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, plastic tips, fiber cores, and porous cores.

[0033] In this invention, "marking pen" means a pen having a mechanism that supplies ink stored in an ink reservoir to a resin writing section by capillary action, and also includes pens referred to as "sign pens." Furthermore, "ballpoint pen" means a pen having a mechanism that causes ink stored in an ink reservoir to seep out by the rotation of a ball provided in the writing section. As a ballpoint pen, the aqueous ink composition for writing instruments having the above composition is contained in an ink reservoir (refill) for ballpoint pens equipped with a ball with a diameter of 0.18 to 2.0 mm, and an ink-following body is added. The ink-following body is a liquid that is incompatible with the aqueous ink composition for writing instruments having the above characteristics contained in the ink reservoir, and has a lower specific gravity than the aqueous ink composition, such as polybutene, silicone oil, or mineral oil. The structure of ballpoint pens, marking pens, etc., is not particularly limited. For example, a direct-ink type ballpoint pen or marking pen may have a collector structure (ink holding mechanism) in which the barrel itself serves as the ink reservoir and the barrel is filled with the aqueous ink composition for writing instruments having the above configuration. [Examples]

[0034] 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.

[0035] [Examples 1-5 and Comparative Examples 1-3] Each aqueous ink composition for writing instruments was prepared by conventional methods according to the formulation shown in Table 1 below. The pH of each aqueous ink composition for writing instruments was measured at room temperature (25°C) 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 prepare a writing instrument by the following method ( Water-based A felt-tip pen was prepared, and the glossiness and uniformity of the coating film, abrasion resistance, and water adhesion resistance were evaluated using the following evaluation methods. These results are shown in Table 1 below.

[0036] (Making felt-tip pens) A felt-tip pen was prepared using each of the ink compositions obtained above. Specifically, a felt-tip pen (manufactured by Mitsubishi Pencil Co., Ltd., product name: PM-120T) was used, with the barrel material being recycled PP resin and the pen tip consisting of (fine) PET fiber and (extra-fine) POM resin. Each ink composition was loaded into the felt-tip pen to prepare the pen. The felt-tip pens obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated.

[0037] (Method for evaluating the low gloss and uniformity of the coating film) A 2cm x 2cm area of ​​paint was hand-painted onto a PET film, and the resulting coating was visually evaluated using the following criteria. <Evaluation Criteria> A: The coating has no gloss and possesses sufficient low gloss. B: The paint film has a slight sheen, and the low gloss is somewhat weak. C: The paint film has a glossy finish.

[0038] (Method for evaluating abrasion resistance) Five circles with a diameter of 15 mm were drawn in succession on a PET film by hand. After 5 minutes, a Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) was placed over the lines, and a 500 g weight was placed on top. The film was then rubbed five times and evaluated according to the following evaluation criteria. <Evaluation Criteria> A: There is no change compared to before the abrasion. B: Compared to before rubbing, there are slight areas where the lines have become lighter. C: Compared to before rubbing, the lines have become lighter across the entire surface.

[0039] (Method for evaluating water-resistant adhesion) Under conditions of 25°C and 65% humidity, a 15mm wide spiral was drawn eight times on a PET film using five layers of water. Tap water was then sprayed onto the film from a commercially available shower nozzle at a flow rate of 12 liters per minute, and the resulting lines were observed and evaluated according to the following criteria (n=10). <Evaluation Criteria> A: There is absolutely no change in the lines drawn. B: The hue of the lines became lighter, or parts of the lines were missing. C: All the lines have been washed away.

[0040] [Table 1]

[0041] As is clear from the results in Table 1 above, the aqueous ink compositions for writing instruments in Examples 1 to 5, which represent the present invention, were found to have a low gloss, form a uniform coating film, and exhibit superior abrasion resistance and water adhesion resistance even when writing on non-absorbent surfaces, compared to the aqueous ink compositions for writing instruments in Comparative Examples 1 and 2, which are outside the scope of the present invention. [Industrial applicability]

[0042] It can be suitably used in aqueous ink compositions for writing instruments such as ballpoint pens and marking pens.

Claims

1. An aqueous ink composition for writing instruments, characterized in that it contains at least 0.5 to 30% by mass of a pigment selected from group A below, 0.01 to 4% by mass of a neutralized isobutylene-maleic anhydride copolymer having a mass-average molecular weight of 3,000 to 200,000, 0.05 to 20% by mass of a polyol having two or more OH groups selected from group B below, 0.1 to 20% by mass of a water-soluble resin and / or resin emulsion in terms of solid content, and water, and the glass transition temperature of the water-soluble resin and / or resin emulsion is -50°C or higher and 120°C or lower. Group A: Inorganic pigments, organic pigments, resin particle pigments containing these pigments, colored resin pigments obtained by coloring resin emulsions with dyes, white plastic pigments, hollow resin pigments (particles), pigments with silica or mica as a base material and a multi-layer coating of iron oxide or titanium dioxide on the surface, and luminous pigments. Group B: 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, cyclohexanedimethanol, glycerin, sugar alcohols

2. The aqueous ink composition for writing instruments according to claim 1, characterized in that the mass-average molecular weight of the neutralized product of the isobutylene-maleic anhydride copolymer is 5,000 to 200,000.

3. A writing instrument characterized by incorporating the aqueous ink composition for writing instruments described in claim 1 or 2.

Images