JP2023078817A - Aqueous ink composition for writing instrument and writing instrument - Google Patents

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 The present invention relates to an aqueous ink composition for a writing instrument that forms a uniform coating film with low gloss and is excellent in scratch resistance and water adhesion resistance even when writing on a non-absorbent surface, and to a writing instrument.

Examples of conventional water-based ink compositions for writing instruments having good scratch resistance, water-resistant adhesion, etc. include:
[1] An aqueous solution containing a coloring agent aqueous solution in which a hydrophobic resin containing an acidic group in which a hydrophobic coloring agent selected from hydrophobic dyes or solvent-soluble pigments is dissolved is dissolved or dispersed in water as a water-soluble salt with an alkaline substance An ink containing a hydrophobic colorant in the range of 0.5 to 10 wt% with respect to the entire ink composition, and a weight ratio of the hydrophobic colorant to the hydrophobic resin of 1:5 to 5:1. A water-based ink characterized in that a hydrophobic resin containing an acidic group has a degree of neutralization with an alkali of 0.1 or more (see, for example, Patent Document 1);
[2] In order to provide an ink which, even when written on the surface of glass or pottery, the handwriting is sufficiently resistant to water, hot water, and abrasion, an acrylic silicone resin is used. a water-based ink composition for glass and ceramic surfaces containing an emulsion, a pigment, a dispersant and a water-based solvent (see, for example, Patent Document 2);
[3] In order to provide a water-based ink composition for writing instruments which is excellent in fixability and follow-up fixability on non-permeable writing materials, and in prevention of hard cake formation and redispersibility of bright pigment particles, water and An aqueous ink composition for writing instruments, comprising glitter pigment particles, a wetting and dispersing agent having an acid value and an amine value, and an elastic polymer (see, for example, Patent Document 3).
etc. are known.

However, in the water-based ink compositions for writing instruments and the like described in Patent Documents 1 to 3, when writing is still performed on a non-absorbing surface, etc., the abrasion resistance, water resistance, etc. are insufficient, and the gloss is low. At present, there is a strong demand for an aqueous ink composition for writing instruments and a writing instrument which form a uniform coating film and are excellent in abrasion resistance, water adhesion resistance, etc. even when writing on a non-absorbing surface.

Japanese Patent Application Laid-Open No. 9-143410 (Claims, Examples, etc.) Japanese Patent Application Laid-Open No. 2014-105282 (Claims, Examples, etc.) Japanese Patent Application Laid-Open No. 2019-119855 (Claims, Examples, etc.)

The present invention is intended to solve the above-mentioned problems and current situation of the prior art, and is intended to form a uniform coating film with low gloss, and even when writing on a non-absorbent surface, the scratch resistance, An object of the present invention is to provide a water-based ink composition for a writing instrument and a writing instrument which are excellent in water-resistant adhesion and the like.

In view of the above-described conventional problems, the present inventors have conducted intensive research and found that at least a coloring material, a neutralized copolymer of specific physical properties, a polyol having two or more OH groups, and a water-soluble The inventors have found that the water-based ink composition for writing instruments and the writing instrument having the above-described objective can be obtained by containing a resin and/or resin emulsion and water, and have completed the present invention.

That is, the water-based 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, and a water-soluble resin and/or resin It is characterized by containing an emulsion and water.
The weight average molecular weight of the isobutylene/maleic anhydride copolymer neutralized product is preferably 3,000 to 400,000.
It is preferable that the coloring material is a pigment.
The writing instrument of the present invention is characterized in that the water-based ink composition for writing instruments having the above structure is mounted.

ADVANTAGE OF THE INVENTION According to the present invention, a low-gloss, uniform coating film is formed, and even when writing on a non-absorbent surface, an aqueous ink composition for a writing instrument and a writing instrument which are excellent in abrasion resistance, water adhesion resistance, etc. are provided. .
The objects and advantages of the invention may be realized and obtained 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 limiting of the invention as claimed.

Embodiments of the present invention are 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 equivalents thereof. In addition, the present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge (including design matters and self-evident matters) in the relevant field.

<Aqueous ink composition for writing instruments>
The water-based 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, and a water-soluble resin and/or a resin emulsion. , and water.

<Color material>
Coloring materials used in the present invention include all dyes that dissolve or disperse in water, conventionally known inorganic and organic pigments such as titanium oxide, pigment-containing resin particle pigments, and pseudo-pigments obtained by coloring resin emulsions with dyes. , White plastic pigments, Hollow resin pigments (particles), Silica or mica-based pigments coated with multiple layers of iron oxide or titanium oxide on the surface, Luster pigments such as aluminum pigments, Thermochromic pigments (particles), Photochromic pigments (particles), etc., and composite pigments (particles) thereof can be used without limitation. As the aluminum pigment that can be used, commercially available products include, for example, the WXM series in which the aluminum surface is rust-proofed with a phosphorus compound, the WL series in which the aluminum surface is rust-proofed with a molybdenum compound, and the aluminum flake surface with a high density. Silica-coated EMR series [manufactured by Toyo Aluminum Co., Ltd.], SW-120PM [manufactured by Asahi Kasei Chemicals Co., Ltd.] and the like can be mentioned, and these can be used alone or in combination of two or more.
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.
Dyes include, for example, acid dyes such as Eosin, Foxin, Water Yellow #6-C, Acid Red, Water Blue #105, Brilliant Blue FCF, Nigrosine NB; Dyes; basic dyes such as rhodamine and methyl violet.

Examples of inorganic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, and nitroso pigments. More specifically, carbon black, titanium black, zinc white, red iron oxide, aluminum, chromium oxide, iron black, cobalt blue, iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermillion, cadmium red, yellow lead, Inorganic pigments such as molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine blue, precipitated barium sulfate, barite powder, calcium carbonate, lead white, dark blue, dark blue, manganese violet, aluminum powder, brass powder, etc. , C.I. I. Pigment Blue 17, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 17, C.I. I. Pigment Blue 27, C.I. I. Pigment Red 5, C.I. I. Pigment Red 22, C.I. I. Pigment Red 38, C.I. I. Pigment Red 48, C.I. I. Pigment Red 49, C.I. I. Pigment Red 53, C.I. I. Pigment Red 57, C.I. I. Pigment Red 81, C.I. I. Pigment Red 104, C.I. I. Pigment Red 146, C.I. I. Pigment Red 245, C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 34, C.I. I. Pigment Yellow 55, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 166, C.I. I. Pigment Yellow 167, C.I. I. Pigment Orange 5, C.I. I. Pigment Orange 13, C.I. I. Pigment Orange 16, C.I. I. Pigment Violet 1, C.I. I. Pigment Violet 3, C.I. I. Pigment Violet 19, C.I. I. Pigment Violet 23, C.I. I. Pigment Violet 50, C.I. I. Pigment Green 7 and the like.

Thermochromic pigments (particles) include a leuco dye that functions as a color former, a developer that is a component capable of developing the color of the leuco dye, and a color change temperature that controls the color change temperature of the leuco dye and the developer. A thermochromic pigment produced by microencapsulating a thermochromic composition containing at least a discoloration temperature adjusting agent that can be used to have a predetermined average particle size (e.g., 0.1 to 10 μm) etc. can be mentioned.
As the photochromic pigment (particles), for example, at least one selected from photochromic dyes (compounds), fluorescent dyes, etc., and photochromic particles composed of a resin such as a terpene phenol resin, or at least photochromic A photochromic composition containing one or more selected from dyes (compounds), fluorescent dyes, etc., an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, a predetermined average particle Examples include photochromic pigments (particles) produced by microencapsulation so as to have a diameter (for example, 0.1 to 10 μm).
In the present invention (including Examples, etc.), "average particle size" is a value measured by laser diffraction or dynamic light scattering method, and in laser diffraction method, D50 value calculated based on volume For this measurement, for example, a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd. can be used. (manufactured by Otsuka Electronics Co., Ltd.) is the value of the average particle size of the cumulant method analysis in the scattering intensity distribution.

These coloring materials can be used alone or in combination of two or more (hereinafter simply referred to as "at least one").
In addition, in these colorants, from the point of further reducing the gloss of the coating film and the uniformity of the coating film, the use of pigments, that is, the above inorganic pigments, organic pigments, resin particles containing pigments, pigments or resins Colored resin pigments such as quasi-pigments made by coloring emulsions with dyes, white plastic pigments, hollow resin pigments (particles), silica or mica-based pigments coated with multiple layers of iron oxide or titanium oxide on the surface, aluminum pigments, etc. Effect pigments, thermochromic pigments (particles), photochromic pigments (particles), etc., and composite pigments (particles) thereof are preferably used.

The (total) content of these colorants is preferably 0.5 to 50% by mass, more preferably 2 It is desirable to make it to 40% by mass, particularly preferably 5 to 30% by mass.
By setting the content of this coloring material to 0.5% by mass or more, it is possible to realize the formation of a more beautiful coating film by expressing low glossiness and uniformity of the coating film, while on the other hand, it is 50% by mass or less. By doing so, the increase in viscosity is suppressed and the fluidity of the ink is improved, which is preferable.

The neutralized isobutylene/maleic anhydride copolymer used in the present invention is a neutralized copolymer of isobutylene and maleic anhydride. When used together, it becomes a component that exhibits the function of forming a uniform coating film with low glossiness and improving scratch resistance and water adhesion resistance.
In the neutralized 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 preferred in the present invention. It is an ammonia-neutralized product (modified product) of isobutylene/maleic anhydride copolymer that can be used.

式（Ｉ）

Formula (I)

式（ＩＩ）

Formula (II)

式（ＩＩＩ） In the present invention, in addition to the ammonia-neutralized product of the above formula (II), a sodium hydroxide-neutralized product and an amine-neutralized product may be used. Numerical values such as n in the above formula (I), l and m in (II), and j and k in the following formula (III) vary depending on the weight average molecular weight and the like described later, and a suitable range is determined. It is.
In the present invention, an imidized isobutylene/maleic anhydride copolymer represented by the following formula (III) obtained by imidizing (imido-modified) an isobutylene/maleic anhydride copolymer is treated with ammonia, sodium hydroxide, an amine, or the like. It may be each neutralized product.

Formula (III)

The weight average molecular weight of each neutralized product obtained by neutralizing the isobutylene/maleic anhydride copolymer of the above formulas (II) and (III) is preferably 3,000 to 400,000, more preferably 5,000 to 200,000. is more preferred, 30,000 to 100,000 is particularly preferred, and 50,000 to 70,000 is most preferred. This weight average molecular weight is a polystyrene-equivalent value obtained by aqueous gel permeation chromatography (GPC) analysis.
Commercially available products can be used as the isobutylene/maleic anhydride copolymer and its neutralized product. , 18, and Isovan-104, 110 include commercially available ammonia-neutralized (modified) products of the isobutylene/maleic anhydride copolymer represented by the above formula (II). 306, 310 neutralized products, and the like. When preparing a neutralized product of the isobutylene/maleic anhydride copolymer [from formula (I) above] to be used, for example, all the carboxyl groups of the isobutylene/maleic anhydride copolymer are neutralized. In this case, each neutralized product can be obtained by setting the degree of neutralization to 1 and calculating and preparing the necessary amounts of ammonia, sodium hydroxide, amine, etc. used for neutralization.

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, it is 0.1 to 2% by mass.
If the content of the neutralized product of the isobutylene/maleic anhydride copolymer is less than 0.01% by mass, the glossiness of the coating film cannot be completely suppressed, resulting in a glossy feeling and a low glossiness cannot be obtained. If the amount exceeds 4% by mass, the viscosity increases, the ink ejection property decreases, the writing property is adversely affected, and the cost increases.

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, and 2-butyl-2-ethyl-1,3-propane. Diol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 1,6-hexanediol, cyclohexanedimethanol, glycerin, sugar alcohol Examples of sugar alcohols include disaccharide alcohols such as isomaltitol, maltitol and lactitol; trisaccharide alcohols such as maltotriitol, isomaltotriitol and panitol; At least one of alcohols, reduced starch saccharification products composed of sugar alcohols of disaccharides or higher, and reduced starch hydrolysates can be used.

The content of these 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% by mass, based on the total amount of the ink composition. .5 to 20% by mass.
If the content of the polyol having two or more OH groups is less than 0.05% by mass, the surface of the coating film dries rapidly, and uneven drawing tends to occur, making it difficult to form a uniform coating film. On the other hand, if it exceeds 40% by mass, the drying properties deteriorate, making it difficult to obtain low-gloss drawn lines.

The water-soluble resin and resin emulsion used in the present invention function as a fixing agent, dispersant, and stabilizer. Acid resin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resin, water-soluble styrene resin, water-soluble ester-acrylic resin, ethylene-maleic acid copolymer, polyethylene oxide, water-soluble urethane resin, etc. 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. At least one selected is included.
From the viewpoint of dispersibility of the coloring material, adjustment of viscosity, and improvement of fixing power, it is preferable to use each of the above water-soluble resins and resin emulsions having a glass transition temperature (Tg) of 120° C. or less, more preferably. , acrylic resins having a glass transition temperature (Tg) of 120° C. or less, water-soluble styrene-acrylic resins, styrene maleic acid, water-soluble resins such as urethane resins, or resin emulsions such as acrylic resin emulsions. The lower limit of the glass transition temperature (Tg) is desirably −50° C. or higher from the viewpoint of drawing quality such as low glossiness and abrasion resistance.
By setting the glass transition temperature (Tg) of the resin to 120° C. or less, cracks on the surface of the coating film can be further suppressed, and scratch resistance and water-resistant adhesion can be further improved.
In the present invention, the "glass transition temperature" is Tg measured according to JIS K7121, and can be measured using, for example, Rigaku thermo plus evo DSC8230 (manufactured by Rigaku).

Commercially available products can be used for the above water-soluble resins and resin emulsions. 56° C.), 70 J (Tg; 102° C.) and PDX-6137A (Tg; 102° C.), and the resin emulsions used are Joncryl PDX352D (Tg; 52° C.) and PDX7199 (Tg; 88° C.) manufactured by BASF. ° C.), PDX7537 (Tg; -4° C.), or KE-1062 (96° C.) and PE-1304 (Tg; 9° C.) manufactured by Seiko PMC.

The (total: solid content) 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, particularly Preferably, it is 1 to 10% by mass.
If the content of the water-soluble resin or resin emulsion is less than 0.1% by mass, the drawn line quality deteriorates, such as a decrease in abrasion resistance. Dischargeability deteriorates.

The water-based ink composition for writing instruments of the present invention contains at least the above-described colorant, a neutralized isobutylene/maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and/or In addition to the resin emulsion, water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as a solvent as the remainder, dispersant, lubricant, and pH adjustment within a range that does not impair the effects of the present invention agents, rust inhibitors, antiseptics or antibacterial agents, thickeners, and the like can be contained as appropriate.

As dispersants that can be used, nonionic, anionic surfactants and water-soluble resins are used. A water-soluble polymer is preferably used.
Examples of lubricants include nonionics such as polyhydric alcohol fatty acid esters, sugar higher fatty acid esters, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, and alkylsulfonic acid higher fatty acid amides, which are also used as surface treatment agents for pigments. Salts, anionic surfactants such as alkylallylsulfonates, derivatives of polyalkylene glycol, fluorine-based surfactants, and polyether-modified silicones can be used.

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. etc. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of antiseptics or antibacterial agents include phenol, sodium omadine, sodium benzoate, and benzimidazole compounds. mentioned.
Examples of thickeners that can be used include cellulose derivatives such as hydroxyalkylcellulose, carboxymethylcellulose (CMC) or salts thereof, fermented cellulose, crystalline cellulose, and polysaccharides. Polysaccharides that can be used include, for example, 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, nigelan, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkasi gum, succinoglycan, locust bean gum, tara gum, etc. be done.
Examples of synthetic polymers include polyacrylic acids, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, bisacrylamide methyl ether, polyacrylamide, polyethyleneimine, polyethylene glycol, polydioxolane, polystyrenesulfonic acid, polypropylene oxide, and the like. mentioned.
These may be used individually by 1 type, and may use 2 or more types together. Moreover, if these commercial products are available, they can be used.

The water-based ink composition for writing instruments of the present invention comprises at least the above coloring material, a neutralized isobutylene/maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and/or a resin emulsion, water, Other components are appropriately combined according to the application of the ink for writing instruments (for ballpoint pens, marking pens, etc.), stirred and mixed with a stirrer such as a homomixer, homogenizer or disper, and if necessary, filtered. By removing coarse particles in the ink composition by centrifugation or the like, an aqueous ink composition for writing utensils having excellent color developability can be obtained.
The pH (25° C.) of the water-based ink composition for writing instruments of the present invention is adjusted to 5 to 10 with a pH adjuster or the like from the viewpoints of usability, safety, stability of the ink itself, and compatibility with the ink container. It is preferably adjusted, more preferably 6 to 9.5.

The water-based ink composition for a writing instrument of the present invention configured as described above contains at least the colorant,
It 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. Aggregation occurs and unevenness is formed on the surface of the coating film, but by adding polyol, aggregation due to volatilization of water is alleviated and uniform loose aggregation is promoted, so a low-gloss, uniform coating film can be obtained. is formed, and even if writing is performed on a non-absorptive surface, an aqueous ink composition for writing instruments that is excellent in abrasion resistance, water adhesion resistance, and the like can be obtained.

〈Writing implements〉
The writing instrument of the present invention is equipped with the water-based ink composition for writing instruments having the above characteristics, and forms a low-gloss, uniform coating film, and even when writing on a non-absorptive surface, it has abrasion resistance and water adhesion resistance. A writing instrument excellent in such as is obtained.
Examples of writing implements include ballpoint pens, marking pens, and the like having a pen tip such as a ballpoint tip, fiber tip, felt tip, plastic tip, fiber core, or porous core.

In the present invention, the "marking pen" means a pen having a mechanism for supplying the ink stored in the ink reservoir to the resin-made writing part by capillary action, and is referred to as a "sign-tip pen". also includes A "ballpoint pen" means a pen having a mechanism for exuding ink stored in an ink reservoir by rotation of a ball provided in a writing part.
As a ballpoint pen, the water-based ink composition for writing instruments having the above composition is contained in a ballpoint pen ink container (refill) having a ball with a diameter of 0.18 to 2.0 mm, and an ink follower is added. The ink follower contains a liquid that is not compatible with the water-based ink composition for writing instruments having the above-described characteristics contained in the ink container and has a low specific gravity relative to the water-based ink composition, such as polybutene and silicone oil. , mineral oil, etc. are used.
The structure of the ballpoint pen, the marking pen, etc. is not particularly limited, and for example, a collector structure (ink holding mechanism) in which the barrel itself is used as an ink reservoir and the aqueous ink composition for writing instruments having the above configuration is filled in the barrel. It may be a direct liquid ballpoint pen or a marking pen.

EXAMPLES 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.

[Examples 1 to 5 and Comparative Examples 1 to 2]
Each water-based ink composition for writing instruments was prepared according to the formulation shown in Table 1 below by a conventional method. When the pH of each water-based ink composition for writing instruments was measured at room temperature (25° C.) with a pH meter (manufactured by HORIBA), it was within the range of 7.9 to 8.2.
For each water-based ink composition for writing instruments obtained above, a writing instrument (a felt-tip pen) was prepared by the following method, and the shine and uniformity of the coating film, the abrasion resistance, and the water adhesion resistance were evaluated by the following evaluation methods. made an evaluation.
These results are shown in Table 1 below.

(Production of felt-tip pen)
A felt-tip pen was produced using each of the ink compositions obtained above. Specifically, a felt-tip pen [manufactured by Mitsubishi Pencil Co., Ltd., product name: PM-120T shaft is used, shaft material: recycled PP resin, pen core: (fine) PET fiber, (ultra-fine) POM resin. A felt-tip pen was prepared by loading each ink composition. Each evaluation was performed using the felt-tip pens of Examples 1 to 5 and Comparative Examples 1 to 4 obtained.

(Evaluation method for low glossiness and uniformity of coating film)
A 2 cm x 2 cm area of PET film was filled in by hand, and sensory evaluation was performed visually according to the following evaluation criteria.
<Evaluation Criteria>
A: The coating film has no gloss and has a sufficiently low glossiness B: The coating film has a slight glossiness and the low glossiness is slightly weak C: The coating film has a glossiness

(Method for evaluating abrasion resistance)
Five circles with a diameter of 15 mm were drawn continuously on a PET film by handwriting, and after 5 minutes, a Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) was placed on the drawn line, and a weight of 500 g was placed on it five times. It was rubbed and evaluated according to the following evaluation criteria.
<Evaluation Criteria>
A: No change from before rubbing.
B: Compared to before rubbing, a portion where the drawn line is thin is slightly observed.
C: The drawn line is thin over the entire drawn line compared to before rubbing.

(Evaluation method for waterproof adhesion)
In an environment with a temperature of 25 ° C and a humidity of 65%, draw a 5-fold spiral with a width of 15 mm on a PET film 8 times, spray tap water from a commercially available shower nozzle at a flow rate of 12 liters per minute, and then draw a line. was observed and evaluated according to the following evaluation criteria (n=10).
<Evaluation Criteria>
A: No change is observed in the drawn line.
B: The hue of the drawn line became light, or the drawn line was partially missing.
C: All the drawn lines have flowed.

As is clear from the results in Table 1 above, each of the aqueous ink compositions for writing instruments of Examples 1 to 5, which is the present invention, is superior to the aqueous ink compositions for writing instruments of Comparative Examples 1 and 2, which are outside the scope of the present invention. In comparison, it was found to form a uniform coating film with low gloss, and to be excellent in abrasion resistance and water adhesion resistance even when written on a non-absorbent surface.

It can be suitably used for water-based ink compositions for writing instruments such as ballpoint pens and marking pens.

Claims (4)

At least a coloring material, a neutralized isobutylene/maleic anhydride copolymer, a polyol having two or more OH groups, a water-soluble resin and/or resin emulsion, and water, A water-based ink composition for writing instruments. 2. The water-based ink composition for writing instruments according to claim 1, wherein the weight average molecular weight of the neutralized isobutylene/maleic anhydride copolymer is 3,000 to 400,000. 3. The water-based ink composition for writing instruments according to claim 1, wherein said coloring material is a pigment. A writing instrument comprising the water-based ink composition for writing instrument according to any one of claims 1 to 3.