JP7256312B2 - Aqueous ink composition for writing instrument and writing instrument using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-based ink composition for writing instruments, and more particularly to a water-based ink composition for writing instruments having excellent ink stability over time and excellent metallic luster of handwriting, and a writing instrument using the same.

Conventionally, regarding water-based ballpoint pens with metallic luster, metallic pigments based on aluminum powder, brass powder, etc., glass flake pigments based on glass, and metal-coated resin film powders based on resin have been used. As a result, a water-based ball-point pen having good metallic luster in handwriting was obtained.

As such prior art, those using aluminum powder are disclosed in JP-A-8-151547 "Aqueous Metallic Lustrous Color Ink", and those using glass flake pigments having a structure in which glass flakes are coated with metal or the like. , Japanese Patent Application Laid-Open No. 2001-262014 ``Glittering water-based ink composition'', and Japanese Patent No. 4346000 ``Glittering water-based ink composition for ballpoint pens'' in which aluminum is vapor-deposited on aluminum-deposited polyethylene terephthalate film powder are disclosed. ing.

"Japanese Unexamined Patent Publication No. 8-151547" "Japanese Unexamined Patent Publication No. 2001-262014" "Patent No. 4346000"

However, as in Patent Document 1, when aluminum powder is used, a certain degree of metallic luster can be obtained in handwriting, but the elution of metal ions reduces the viscosity of the ink, which affects the dispersibility of the pigment. As a result, the stability of the ink over time tends to deteriorate, and the writing performance is likely to be affected by precipitates formed by the reaction between the metal ions and the ink components. Furthermore, the shear resistance by a mixer or the like during ink production is also weak, and when the aluminum powder surface is damaged, metal ions are more likely to be eluted, and similarly, the ink tends to affect aging. In addition, as in Patent Documents 2 and 3, when the surface is coated with a metal such as a glass flake pigment or a metal-coated resin film powder, the metallic luster is good, but the ink stability over time is the same as in Cited Document 1. Furthermore, since the ball seat is covered with metal, wear of the ball seat is likely to be accelerated due to metal resistance between the metal and the ball seat, and poor writing is likely to occur.
Furthermore, in Patent Documents 1 to 3, metal such as aluminum powder reacts with water or the like, causing problems such as generation of air bubbles and loss of metallic luster over time.

Furthermore, when a metal pigment is used in a ballpoint pen, the metal contact resistance between the metal pigment and the ball seat is large, and the wear of the ball seat is severe, which may cause poor writing. When using , the smaller the diameter of the ball, the higher the number of rotations of the ball when writing at the same distance. .

An object of the present invention is to provide a water-based ink composition for a writing instrument which has excellent ink stability over time, does not corrode metal powder (metallic pigment), and gives excellent metallic luster to handwriting, and a writing instrument using the same.

In order to solve the above problems, the present invention
"1. An aqueous ink composition for writing instruments, comprising water, metal powder, and alkylphosphonic acid.
2. 2. The water-based ink composition for writing instruments according to claim 1, wherein the metal powder is a metal pigment surface-treated with an alkylphosphonic acid.
3. Item 1 or 2, wherein the total mass of the alkylphosphonic acid is 0.001 to 0.5 times the total mass of the metal powder in the total mass of the ink composition. A water-based ink composition for writing instruments.
4. 4. The water-based ink composition for writing instruments according to any one of items 1 to 3, wherein the alkyl group of the alkylphosphonic acid has 1 to 20 carbon atoms.
5. 5. The water-based ink composition for writing instruments according to any one of items 1 to 4, wherein the water-based ink composition for writing instruments contains a bubble absorbent.
6. 6. The water-based ink composition for writing instruments according to any one of items 1 to 5, wherein the pH value of the water-based ink composition for writing instruments is 6-10.
7. 7. A writing utensil characterized by directly packing the water-based ink composition for writing utensils according to any one of items 1 to 6 in an ink container. "
and

The present invention provides a water-based ink composition for writing utensils in which metal powder dispersibility is improved by suppressing the elution of metal ions, the ink has excellent stability over time, and the metal powder (metal pigment) does not corrode. , the effect that the metallic luster of the handwriting is good can be exhibited.

A feature of the present invention is that a metal powder (metal pigment), an alkylphosphonic acid and imidazolines are used in combination in an aqueous ink composition for writing instruments.

In the present invention, a metal pigment is used as the colorant, and the metal powder of the metal pigment is a metal powder such as aluminum, brass, stainless steel, bronze, titanium oxide, iron oxide, aluminum oxide, or an alloy thereof. . In the present invention, it is important to use metal powder and alkylphosphonic acid in combination. This is because the dispersibility of the metal powder is improved, the ink is excellent in stability over time, the generation of air bubbles in the ink is suppressed, and the metallic luster of handwriting is improved.

To explain the above effects in detail, for inks using metal pigments containing metal powder, the ink is thickened using a pigment dispersant to disperse the metal powder and a resin or the like to adjust the viscosity of the ink. At that time, if a large number of metal ions are present in the ink, the metal ions hinder the dispersion of the pigment and the thickening of the ink viscosity, resulting in poor ink aging. Therefore, in the present invention, metal powder and alkylphosphonic acid are used together, and the alkylphosphonic acid is adsorbed on the surface of the metal powder, thereby suppressing the elution of metal ions in the ink and improving the dispersibility of the metal powder. By suppressing metal salt deposits generated by the reaction of metal ions with other ink components, it is possible to achieve excellent ink stability over time. In addition, by adsorbing the alkylphosphonic acid on the surface of the metal powder, it is highly resistant to shearing by a mixer during ink production, the surface of the metal powder is less likely to be damaged, and the elution of metal ions can be further suppressed. In addition, when the alkylphosphonic acid is adsorbed on the surface of the metal powder, aggregation of the metal powder in the ink is suppressed by the interposition of the alkylphosphonic acid, and an effect of stabilizing the dispersibility of the pigment is also obtained.
In addition, the metal powder with alkylphosphonic acid adsorbed on the surface of the metal powder does not easily react with water in the ink, so it is stable, suppresses the generation of bubbles, has good corrosion resistance, and has a metallic luster. can be maintained. Good reflectivity and good metallic luster are obtained even with coatings by adsorption with alkylphosphonic acids.
Furthermore, during writing, the alkylphosphonic acid reduces the writing resistance during writing to improve the writing feel, and especially when used in a ballpoint pen, accelerates the wear of the ball seat due to the metal resistance caused by the contact of the metal powder with the ball seat. However, as in the present invention, it is possible to suppress the wear of the ball seat by suppressing the metal resistance between the metal powder and the ball seat by means of the film to which the alkylphosphonic acid is adsorbed. .

(alkylphosphonic acid)
The alkylphosphonic acid used in the present invention is a phosphonic acid compound having an alkyl group, and since both the functional groups of the phosphonic acid group and the alkyl group of the alkylphosphonic acid are easily adsorbed to the metal powder, the adsorption is stable for a long period of time. Therefore, the long-term aging stability is better than that of conventional metal powders, and the above effect can be obtained for a long period of time. In particular, considering the dispersibility of the metal powder and the stability of the ink over time, it is preferable to use a metal pigment obtained by surface-treating the metal powder with an alkylphosphonic acid, and more preferably, the metal powder is previously surface-treated with an alkylphosphonic acid. It is preferred to use metal pigments.

Regarding the alkylphosphonic acid, by improving the adsorption to the metal powder, the elution of metal ions is suppressed, the dispersibility of the metal powder (metal pigment) is improved, and the metal salt deposit is suppressed. Considering good ink stability over time and metallic luster of handwriting, the number of carbon atoms in the alkyl group is preferably 1 to 20. This is because the longer the alkyl group, the wider the adsorption area. This is because it is easily adsorbed to the metal powder. Considering the balance between the stability of the ink over time and the suppression of abrasion of the ball seat of the ballpoint pen, the number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 6 to 10. and most preferably the alkyl group has 8 carbon atoms. Furthermore, the alkyl group is not limited to a straight chain structure or a branched chain structure, but an alkyl group having a straight chain structure is preferable because it has a wider adsorption area and is easily adsorbed to metal powder, and the ink is stable over time. It is preferable because it tends to have good properties.

Specific examples of the alkylphosphonic acids include methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid, isobutylphosphonic acid, pentylphosphonic acid, hexylphosphonic acid, heptylphosphonic acid, octylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, salts thereof, and the like.

Further, in the total amount of the ink composition, the total mass of the alkylphosphonic acid is preferably 0.001 to 0.5 times the total mass of the metal powder. If the ratio is less than 0.001 times, the entire surface of the metal powder is adsorbed, making it difficult to coat the metal powder. is difficult to obtain, and if it exceeds 0.5 times, the alkylphosphonic acid tends to be excessive with respect to the metal powder, and the surplus tends to precipitate or metal salt deposits tend to occur. . Considering this tendency, the content ratio is preferably 0.001 to 0.3 times by mass, and more preferably 0.005 to 0.2 times. .

As for the metal powder used in the present invention, the metal powder surface-treated with alkylphosphonic acid is processed in advance with a surfactant, a resin, a solvent, etc., and then dispersed to form a paste-like metal pigment or a liquid-like powder. A metal pigment or the like may be used, and the metal powder obtained by surface-treating the metal powder with alkylphosphonic acid is processed with wax, a surfactant, a resin, or the like, but is a solid metal pigment that does not contain a solvent. And so on. Considering the dispersion stability of the metal powder, it is preferable to use a paste-like metal pigment or a liquid metal pigment. In particular, it is preferable to surface-treat the metal powder with alkylphosphonic acid and mix it with a solvent to form a paste-like metal pigment. It is preferable to use ether solvents, polyhydric alcohol solvents, and alcohol solvents. More preferably, propylene glycol ethers and lower alcohols (having 1 to 5 carbon atoms) are used. It is preferred to use glycol ethers, most preferably propylene glycol monomethyl ether. These may be used singly or in combination of two or more.

Among metal powders, those using aluminum powder are preferable because the metallic luster of handwriting is good, the specific gravity is relatively small among metals, and the metal powder is unlikely to settle. As for the shape of the metal powder, a scaly or angular shape is preferable because light can be easily diffused and the metallic luster becomes clearer. It is easy to stick to the seat, and by suppressing the contact resistance between the ball and the ball seat, it is easy to suppress wear of the ball seat. It is more effective because resistance is easily suppressed and writing comfort is improved. In addition, there are leafing type and non-leafing type, but the leafing type is more preferable because the metal powder floats and is arranged on the surface layer of the ink film, and the metallic luster of handwriting tends to be improved.

The size of the metal powder preferably has an average particle size of 1 to 30 μm. This is because the metal powder in the ink tends to be clogged in the ink and tends to cause poor writing. Taking this tendency into account, the average particle size is preferably 3 to 20 μm, and most preferably 5 to 15 μm, taking into account wear suppression of the ball seat. Here, the average particle size is measured using a laser diffraction method, specifically, a laser diffraction particle size distribution analyzer (trade name “Microtrac HRA9320-X100”, Nikkiso Co., Ltd.), using standard samples and other measuring methods. It can be obtained from the particle diameter (D50) at 50% volume accumulation of the particle size distribution measured based on the numerical value calibrated by the .
It is preferable to determine the particle size of the metal powder in the dispersed state because the metal powder exerts the above-described effect in the dispersed state of the metal powder in the ink composition.

If the content of the metal powder is less than 1.0% by mass, the desired metallic luster of the handwriting cannot be obtained, and if it is 10.0% by mass or more, the ink will not be stable over time. 1.0 to 10.0% by mass is preferable. Furthermore, considering the improvement of dry-up performance and wear of the ball seat, the content is more preferably 1.0 to 7.0% by mass, and more preferably 1.0 to 5.0% by mass.

In addition, it preferably contains imidazolines to prevent corrosion of the metal powder. As for imidazolines, 2-alkyl-1-hydroxyethylimidazoline and 2-alkyl-1-ethyleneamineimidazoline are preferably used, and 2-alkyl-1-hydroxyethylimidazoline is preferred in consideration of stability in ink. is preferably used. As for imidazolines, it is preferable to mix metal powder, alkylphosphonic acid, solvent, and imidazolines in advance to obtain a paste-like metal powder pigment in consideration of stability in ink.

(Pigment dispersant)
In addition, as a pigment dispersant used for the purpose of improving the dispersibility of the metal powder (metal pigment) and suppressing the sedimentation and aggregation of the metal powder, acidic resins, basic resins, nonionic surfactants, anionic surfactants agent, etc., but it is preferable to use an acidic resin in consideration of long-term pigment dispersion stability. Examples of acidic resins include acidic resins having carboxyl groups, phenyl groups, sulfonic acid groups, etc. Specific examples include acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, phenolic resins, polyvinyl-sulfonic acid. Among the above acidic resins, an acidic resin having a carboxyl group is preferred. Acidic resins having carboxyl groups are preferable, more preferably styrene groups, because they easily adsorb to the metal powder or alkylphosphonic acid, tend to stabilize metal powder dispersion for a long period of time, and have good handwriting fixability. A styrene-acrylic resin having a styrene group and a carboxyl group is most preferable because the metal powder tends to be easily dispersed and stabilized by facilitating repulsion of the metal powder due to the hindrance due to the steric structure of .

If the content of the pigment dispersant is less than 0.1% by mass relative to the total amount of the ink composition, it is difficult to obtain the desired pigment dispersing effect. Therefore, 0.1 to 5.0% by mass is preferable. More preferably, it is 1.0% by mass to 4.0% by mass.

When metal powder is used as in the present invention, the shape of the metal powder in the metal powder may be scaly or angular, and air bubbles entrained during ink production tend to be difficult to escape. It is preferable to use agents. Foam absorbers include hydroxylamines, ascorbic acids, erythorbic acids, and polyphenols. These air bubble absorbents are compounds exhibiting reducing properties, and absorb oxygen in the ink to exhibit air bubble absorption effects. In addition, regarding hydroxylamines, ascorbic acids, erythorbic acids, and polyphenols, hydroxylamine, hydroxylamine derivatives, polyphenols, polyphenol derivatives, ascorbic acid, ascorbic acid derivatives, erythorbic acid, erythorbic acid derivatives, and salts thereof etc.

As for the air-bubble absorbent, some ascorbic acids are strongly acidic (pH value = 2), and by reacting with the components in the ink, they affect the stability of the ink over time and the dispersibility of the metal powder used in the present invention. Ascorbic acids and polyphenols are likely to be released, and furthermore, hydroxylamines and erythorbic acids are preferably used because they tend to affect the color tone. Moreover, it is preferable to use erythorbic acids because hydroxylamines may give off an amine odor.

The content of the air-bubble absorbent is preferably 0.01 to 5.0% by mass with respect to the total amount of the ink composition. This is because if the content is 0.01% by mass or less, it tends to be difficult to sufficiently absorb oxygen in the ink, and if it exceeds 5.0% by mass, the ink tends to affect the stability over time. It's for. Considering this tendency, the content is preferably 0.1 to 3.0% by mass, most preferably 0.1 to 1.0% by mass.

The pH value of the water-based ink composition for writing instruments of the present invention is preferably 6.0 to 10.0 in consideration of the ink stability over time. This is because when approaching the acidic side of less than pH 6 or approaching the strongly alkaline side of exceeding pH 10, the metal powder is likely to corrode, affecting the metallic luster and the dispersibility of the metal powder (metal pigment). This is because it becomes easier to In particular, when aluminum powder is used, the pH value is more preferably 7.0 to 9.0 in consideration of corrosion of aluminum. The pH value is the value measured at 20° C. using a pH meter HM-30R manufactured by DKK Toa.

Regarding the pH value, if the ink is left for a long period of time, carbon dioxide in the air tends to cause the pH value of the ink to shift to the acidic side. It is preferable to contain urea in order to prevent it from becoming less than.

The content of urea is preferably 0.1 to 5.0% by mass with respect to the total amount of the ink composition. This is because if the content is 0.1% by mass or less, there is a tendency that the effect of suppressing the pH value from becoming less than 7 for a long period of time cannot be obtained. because it tends to affect Considering this tendency, the content is preferably 0.1 to 3.0% by mass, most preferably 1.0 to 3.0% by mass.

Specific examples of pH adjusters include alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine and diisopropanolamine, ammonia, sodium carbonate, Alkaline inorganic salts such as potassium carbonate, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium hydrogen phosphate and potassium hydrogen phosphate, and organic acids such as lactic acid, acetic acid and citric acid. Among them, it is preferable to use triethanolamine, which is more weakly basic, in consideration of ink stability over time. Further, when an acidic resin is used as a metal powder dispersant, it is difficult to obtain a sufficient effect for neutralizing the acidic resin. It is preferable to neutralize using a pH adjuster other than triethanolamine, such as monoethanolamine, diethanolamine, dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, diisopropanolamine, ammonia, etc., and a small amount By containing it, the pH value can be easily adjusted to 6.0 or higher. However, if a pH adjuster other than triethanolamine is used alone, it is too basic and the pH value tends to exceed 10.0, so it is preferable to use triethanolamine in combination. As the pH adjuster other than triethanolamine, it is preferable to use diethanolamine or ammonia in consideration of ink stability over time. Therefore, in the present invention, it is preferable to use two or more pH adjusters, and most preferably two or more alkanolamines.

Regarding the content of the pH adjuster, the content of triethanolamine is preferably 0.1 to 10.0% by mass in consideration of the ink stability over time. In addition, if the content of the pH adjuster other than triethanolamine, such as diethanolamine, dimethylethanolamine, and ammonia, is less than 0.1% by mass, it is difficult to obtain the effect of neutralizing the acidic resin, and the content is 5.0% by mass. 0.1 to 5.0% by mass is more preferable because if the content exceeds

Further, when metal powder is used in a ballpoint pen, it is preferable to contain a surfactant because metal resistance of the metal powder in contact with the ball seat tends to accelerate wear of the ball seat. This is because the surface-active agent improves lubricity and smoothes the rotation of the ball, thereby suppressing wear of the ball seat and improving the writing feel. Examples of surfactants include phosphate surfactants, silicone surfactants, acetylene glycol surfactants, fluorine surfactants, fatty acid salts thereof, and the like. Among them, it is preferable to use phosphate surfactants, fatty acids, salts thereof, and the like. These surfactants may be used alone or in combination of two or more.

Among them, it is preferable to use a phosphate surfactant or a salt of a fatty acid, because the phosphoric acid group or fatty acid group adsorbs metal to further improve lubricity and suppress wear of the ball seat. In view of lubricity, it is preferable to use a phosphate ester-based surfactant, and it is preferable to use a phosphate ester-based surfactant having an alkyl group.
Types of alkyl group-containing phosphate surfactants include styrenated phenol, nonylphenol, lauryl alcohol, tridecyl alcohol, octylphenol, and octyl alcohol surfactants. Among these, if it has a phenyl skeleton, the lubricity is likely to be affected by steric hindrance, and furthermore, the compatibility with the metal powder tends to affect the ink stability over time. It is preferred to use an active agent.

Another effect of the phosphate ester-based surfactant having an alkyl group is that even if the film of the alkylphosphonic acid adsorbed on the metal powder is peeled off, the phosphate group and the alkyl group of the phosphate ester-based surfactant However, by adsorbing to the peeled portion, the elution of metal ions is suppressed, so that the dispersibility of the metal powder is improved, the metal salt deposit is easily suppressed, and the ink stability over time is easily improved. . Furthermore, in ballpoint pens with tip bodies and ink containers made of metals such as stainless steel and nickel silver, the use of phosphate ester surfactants reduces the manganese content in stainless steel and nickel silver materials. It also has the effect of suppressing the elution of metal ions such as manganese ions such as chromium and copper, chromium ions, and copper ions. is. Furthermore, considering the suppression of elution of metal ions and the stability of the ink over time, the number of carbon atoms in the alkyl group is preferably 1 to 20. This is because it is easily adsorbed. Considering the balance between the stability of the ink over time and the suppression of abrasion of the ball seat of the ballpoint pen, the number of carbon atoms in the alkyl group is preferably 6 to 18, more preferably 10 to 15, and further 11 to 14. preferable.

Phosphate ester-based surfactants include polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphate monoester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphate diester, and polyoxyethylene alkyl ether. or polyoxyethylene alkyl aryl ether phosphate triesters, alkyl phosphates, alkyl ether phosphates or derivatives thereof, and these phosphate ester-based surfactants or fatty acids may be used alone or in combination of two or more. can be used as

The content of the surfactant is preferably 0.1 to 5.0% by mass with respect to the total amount of the ink composition. This is because if the amount exceeds 5.0% by mass, the ink stability over time tends to be affected. Considering this tendency, the amount is preferably 0.1 to 3.0% by mass.

Considering the improvement of metal powder (metal pigment) dispersibility, it is preferable to use a shear thinning agent. Examples of the shear thinning agent include polyacrylic acid, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, oxidized cellulose, diutan gum and the like. By forming a three-dimensional network structure in the ink, it becomes easier to stabilize the metal powder dispersion. These shear thinning agents may be used alone or in combination of two or more.

In addition, among shear-thinning agents, polyacrylic acid is preferred because polyacrylic acid has the effect of stabilizing the dispersibility of metal powder (metal pigment) for a long period of time. Furthermore, metal ions in the metal powder are eluted in the ink and may react in the ink to form precipitates, which tends to make the ink unstable over time. Therefore, among polyacrylic acids, it is preferable to use a crosslinked acrylic acid polymer. By forming a three-dimensional crosslinked structure, it improves the dispersibility of metal powder with a high specific gravity. Furthermore, since the acrylic acid polymer has a large number of carboxyl groups ( ^-COO- ), it can be used in a wide range of inks. , suppresses the elution of metal ions, and is presumed to facilitate good ink aging. Therefore, in order to improve ink aging, it is most preferable to use a crosslinked acrylic acid polymer.

The viscosity of the ink is preferably 1000 to 5000 (Pa·s) at a shear rate of 0.001 (sec ^-1 ) in an environment of 20°C. When the ink viscosity is less than 1000 (Pa·s), the ink viscosity is too low and tends to affect the dispersibility of the metal powder. It's for. Considering the tendency to improve metal powder dispersibility, dry-up performance and ink followability, it is preferably 1000 to 3000 (Pa·s).

The surface tension (mN/m) of the ink composition for water-based ballpoint pens is preferably 20 to 35 (mN/m) in an environment of 20°C. If it is less than 20 (mN/m), the handwriting tends to bleed and strike-through on paper tends to occur, and if it exceeds 35 (mN/m), the handwriting drying property is likely to be affected. 23 to 30 (mN/m) is preferable in consideration of the tendency and the metallic luster of handwriting. The surface tension is measured in a 20° C. environment using a surface tension measuring instrument manufactured by Kyowa Interface Science Co., Ltd., using a glass plate, and measured by the vertical plate method.

When using these shear-thinning agents, it is preferable to use an aminocarboxylic acid. It is easy to interfere, and there is a risk that the ink viscosity will be reduced. By containing aminocarboxylic acid, the metal ion is wrapped in aminocarboxylic acid, which stably forms a three-dimensional network structure of the shear thinning agent. This is because the metal powder dispersibility is easily stabilized. In addition, when metal ions are eluted in the ink, the metal ions may react with other ink components to form metal salt deposits. Therefore, the effect of facilitating the suppression of metal salt deposits tends to be obtained.

Specific examples of aminocarboxylic acids include ethylenediaminetetraacetic acid (EDTA), L-aspartic acid (ASDA), L-glutamic diacetic acid (GLDA), cyclohexanediaminetetraacetic acid (CyDTA), and hydroxyethylethylenediaminetriacetic acid (HEDTA). , diethylenetriamine pentaacetic acid (DTPA), dihydroxyethylglycine (DHEG), hydroxyethylimino diacetic acid (HIDA), and salts thereof such as alkali metal salts, ammonium salts and amine salts. These may be used alone or in combination of two or more. Among them, it is preferable to use ethylenediaminetetraacetic acid (EDTA) and its salts, which easily envelop metal ions and easily suppress metal salt deposits. The content of aminocarboxylic acid is preferably 0.1 to 2.0% by mass based on the total amount of the ink composition. If it is less than 0.1% by mass, the effect of wrapping metal ions tends to be inferior, and if it exceeds 2.0% by mass, the ink becomes unstable over time. .3 to 1.0% by mass.

In addition, it is preferable to use a water-soluble solvent in consideration of dissolution stability of water, prevention of drying by evaporation of water, and the like. Polyhydric alcohol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerin, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol , 3-methyl-1-butyn-3-ol, alcohol solvents such as ethylene glycol monomethyl ether acetate and other higher alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 3-methoxybutanol, 3-methoxy- Examples include glycol ether solvents such as 3-methylbutanol. Among them, it is preferable to use a polyhydric alcohol solvent in consideration of the dissolution stability with the metal powder used in the present invention. A polyhydric alcohol solvent is a solvent that is a compound in which two or more hydroxyl groups are bonded to different carbon atoms of an aliphatic or alicyclic compound. When the nib dries in the air, the dry-up performance (writing performance) tends to be poor, and considering the tendency to improve the dry-up performance, aliphatic polyhydric alcohols are preferable. Most preferably, it contains at least a polyhydric alcohol having a divalent or trivalent hydroxyl group. These may be used alone or in combination of two or more.

The content of the solvent is preferably 10.0 to 25.0% by mass, more preferably 10.0 to 20.0% by mass, based on the total amount of the ink composition in consideration of solubility, dry-up property, bleeding, and the like. 0% by weight is preferred.

Therefore, it is preferable to contain dextrin, which enables the formation of a sufficient coating on the pen tip. In particular, scaly or angular particles such as metal powder are likely to be caught in the gaps between balls of the pen tip, so that the inclusion of dextrin is effective.

Further, the weight average molecular weight of dextrin is more preferably 5,000 to 120,000. If the weight-average molecular weight exceeds 120,000, the film formed on the pen tip is hard, and the handwriting tends to be blurred when writing at the time of dry-up. This is because the film on the pen tip tends to soften, carbon dioxide in the atmosphere easily enters through the gaps in the pen tip, and the stability of the ink over time is likely to be affected. Also, if the weight average molecular weight is less than 20,000, the film tends to be thin, so the weight average molecular weight is most preferably 20,000 to 120,000.

The content of dextrin is preferably 0.1 to 5.0% by mass with respect to the total amount of the ink composition. This is because if it is less than 0.1% by mass, the effect of forming a film on the pen tip tends to be insufficient, and if it exceeds 5.0% by mass, it tends to be difficult to dissolve in the ink. . 0.1 to 3.0% by mass is preferable in consideration of solubility in ink, and 0.5 to 3.0% by mass is most preferable in consideration of the effect of forming a film on the pen tip. .

Further, an ink containing tube having a pen tip filled directly with a water-based ink composition for writing instruments is slidably disposed in the barrel so that the pen tip can be projected and retracted from a tip opening of the barrel. In retractable writing instruments such as knock-type writing instruments and rotary feeding-type writing instruments, the pen tip is kept out than the cap-type writing instrument, so carbon dioxide in the atmosphere easily enters through the gap in the nib. Since the pH value of the ink in the tip tends to be on the acidic side, the stability of the ink over time is likely to be affected, so it is preferable to cover the pen tip as soon as possible.

In the present invention, a coloring agent other than metal powder may be used in combination. Inorganic, organic, processed pigments, etc. may be used, and specific examples include carbon black, aniline black, ultramarine blue, yellow lead, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, quinophthalone-based, threne-based, triphenylmethane-based pigments. , perinone-based, perylene-based, gioxazine-based, pearl pigments, fluorescent pigments, phosphorescent pigments, and the like. In addition, a microcapsule pigment obtained by encapsulating or dissolving a colored body, which is obtained by dispersing a pigment in a medium as a colored resin particle body, in a shell made of a resin wall film-forming substance by a known microencapsulation method or the like may be used. good. Moreover, you may use dye together as a coloring agent. As for dyes, direct dyes, acid dyes, basic dyes, metallized dyes, and various salt forming type dyes can be used. Furthermore, colored resin particles obtained by covering a pigment with a transparent or translucent resin or the like, or colored resin particles or colorless resin particles colored with a pigment or dye can also be used. These pigments and dyes may be used alone or in combination of two or more. The content is preferably 0.01% by mass to 20% by mass with respect to the total amount of the ink composition.

In addition, additives such as acrylic resin emulsions, urethane resin emulsions, styrene-butadiene resin emulsions, and polyolefin resin particles, and antibacterial agents such as 1,2-benzisothiazolin-3-one, may be added as desired. agents, rust inhibitors such as benzotriazole, and the like can be added. These can be used alone or in combination of two or more.

(writing implements)
The water-based ink composition of the present invention can be used in writing instruments such as marking pens and ballpoint pens with pen tips such as fiber tips, felt tips, plastic tips, ballpoint pen tips, and fountain pens with metal pen tips. can be done.

In the case of a ball-point pen, the ball material is not particularly limited, but may be a cemented carbide ball containing tungsten carbide as a main component, or a ball having a carbonaceous film formed on the surface of the ball. Examples include balls having atoms and oxygen atoms bonded to the carbon atoms, silicon carbide, alumina, zirconia, silicon nitride, and the like. It is preferable to use a silicon carbide ball in consideration of the feeling of writing without being affected by metal corrosion. The size of the ball is determined by the application of the writing instrument and the width of the drawn line required during writing, and is generally selected within the range of 0.1 to 2.0 mm. The present invention can exhibit a more favorable effect when using a small-diameter ball, for example, a small-diameter ball having a diameter of 0.5 mm or less. This is because the smaller the diameter of the ball, the higher the number of revolutions of the ball when writing for the same distance, and the ball seat tends to wear out easily.

Considering the suppression of wear of the ball seat and the improvement of writing comfort, it is preferable to set the arithmetic average roughness (Ra) of the ball surface to 0.1 to 10 nm. This is because if the arithmetic mean roughness (Ra) exceeds this range, the surface of the ball becomes too rough and the rotational resistance between the ball and the ball seat tends to increase, which tends to affect the writing quality and wear of the ball seat. If the amount is below this range, the metal pigment is not sufficiently applied to the surface of the ball, which tends to affect writability such as faint handwriting. Therefore, in order to suppress the wear of the ball seat, improve the writing feel, and obtain the writability, it is preferable that the arithmetic mean roughness (Ra) of the ball surface is 0.1 to 10 nm. The ball surface preferably has an arithmetic mean roughness (Ra) of 0.1 to 5 nm.
Regarding the arithmetic average roughness of the ball surface, the arithmetic average roughness (Ra) is defined by the direction of the average line from the roughness curve measured by a surface roughness measuring instrument (manufactured by Seiko Epson, model name SPI3800N). It is the value obtained by extracting the length, summing the absolute values of the deviations from the average line of the sampled portion to the measurement curve, and averaging them.

The amount of movement of the ball of the ball-point pen tip in the vertical axis direction is preferably 30 to 50 μm. This is because the resistance to ink leakage tends to be poor. Considering the metallic luster of handwriting, the thickness is preferably 35 to 45 μm.

In the case of a ballpoint pen, the ink consumption per 100 m is preferably 100 to 400 (mg), considering the metallic luster of the handwriting, the dryness of the handwriting, the writing feel, and the wear of the ball seat. Taking this into consideration, it is preferable to set it to 150 to 300 (mg). Regarding ink consumption, 5 test samples were measured on JIS P3201 writing paper A as writing paper at a writing speed of 4 m/min under conditions of a writing angle of 65 ° and a writing load of 100 g under an environment of 20 ° C. A spiral writing test is carried out using the tape, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m.

In the present invention, considering the improvement of the metallic luster of the handwriting, it is easy to improve the metallic luster of the handwriting by paying attention to the ink consumption (mg) per 100 m with respect to the ball diameter (mm). Specifically, when "ball diameter (mm) is A (mm)" and "ink consumption (mg) per 100 m is B (mg)", it is preferable that 200 ≤ B/A ≤ 500. . This is because if it is in the above range, the metallic luster of the handwriting can be improved, and the writing properties such as dryness, tearing, bleeding, writing feel, and wear of the ball seat can be improved. For example, it is preferable that 250≤B/A≤400. In particular, it is preferable to set the amount of movement of the ball of the ball-point pen tip in the vertical axis direction to 35 to 45 μm because it is easy to achieve the B/A range.

The present invention will now be described with reference to examples.
(Ink composition for water-based ballpoint pen)
Example 1
Metal pigment (65% aluminum powder, 3% octylphosphonic acid, leafing type)
5.0 parts by mass Pigment dispersant (acidic resin) 2.0 parts by mass Water 69.0 parts by mass Water-soluble solvent (diethylene glycol) 15.0 parts by mass Foam absorbent (erythorbic acid) 0.5 parts by mass Urea 1.0 Parts by mass pH adjuster (diethanolamine) 1.0 parts by mass pH adjuster (triethanolamine) 3.0 parts by mass Aminocarboxylic acid (ethylenediaminetetraacetic acid) 0.5 parts by mass Lubricant (phosphate surfactant) 1.0 parts by mass Dextrin (weight molecular weight: 100000) 1.0 parts by mass Rust inhibitor (benzotriazole) 0.5 parts by mass Shear thinning agent (crosslinked acrylic acid polymer) 0.5 parts by mass

First, metal powder was surface-treated with alkylphosphonic acid (octylphosphonic acid), and imidazoline and propylene glycol monomethyl ether were mixed to prepare a paste-like metal pigment.
Furthermore, the metal pigment prepared above, a pigment dispersant, water, a water-soluble solvent, a bubble absorber, urea, an aminocarboxylic acid, a pH adjuster, a lubricant, a dextrin, and a rust inhibitor are heated and stirred with a magnetic hot stirrer. to create a base ink.

After that, while heating the base ink prepared above, a shear thinning agent is added, and the mixture is sufficiently mixed and stirred using a homogenizer stirrer until a uniform state is obtained. got
The viscosity of the ink in Example 1 was measured using a TA Instruments Rheometer AR-G2 viscometer (cone plate 40 mm, angle 2°) under an environment of 20°C at a shear rate of 0.001 (sec ^-1 ), the ink viscosity was 1450 (Pa·s). Further, the pH value of Example 1 was measured at 20° C. using a pH meter HM-30R manufactured by Toa DKK Corporation, and was found to be pH=8.0.
Further, in a 20° C. environment, the surface tension of the water-based ink composition for writing instruments was measured by the vertical plate method using a glass plate using a surface tension measuring instrument manufactured by Kyowa Interface Science Co., Ltd. The surface tension of the water-based ink composition for writing instruments was 26 (mN/ m).

Examples 2-12
Aqueous ink compositions for writing instruments of Examples 2 to 12 were obtained in the same manner as in Example 1, except that the ink formulation was changed as shown in the table. The table shows ink formulations and evaluation results.

The present invention will now be described with reference to examples.
(Aqueous ink composition for writing instruments)
Example 13
Metal pigment (65% aluminum powder, 3% alkylphosphonic acid, leafing type)
5.0 parts by mass Pigment dispersant (acidic resin) 2.0 parts by mass Water 70.5 parts by mass Water-soluble solvent (diethylene glycol) 15.0 parts by mass Foam absorbent (erythorbic acid) 0.5 parts by mass Urea 1.0 Parts by mass pH adjuster (diethanolamine) 1.0 parts by mass pH adjuster (triethanolamine) 3.0 parts by mass Aminocarboxylic acid (ethylenediaminetetraacetic acid) 0.5 parts by mass Dextrin (weight molecular weight 100000) 1.0 parts by mass Rust inhibitor (benzotriazole) 0.5 parts by mass

First, metal powder was surface-treated with alkylphosphonic acid, and imidazoline and propylene glycol monomethyl ether were mixed to prepare a paste-like metal pigment.
Furthermore, the metal pigment prepared above, a pigment dispersant, water, a water-soluble solvent, a bubble absorber, urea, an aminocarboxylic acid, a pH adjuster, a lubricant, a dextrin, and a rust inhibitor are heated and stirred with a magnetic hot stirrer. to create a base ink.

Examples 14 and 15
A water-based ink composition for writing instruments was obtained in the same manner as in Example 12, except that the ink formulation was changed as shown in the table. Table 1 shows ink formulations and evaluation results.

Comparative Examples 1-4
Water-based ink compositions for writing instruments of Comparative Examples 1 to 4 were obtained in the same procedure as in Example 1, except that the ink formulation was changed as shown in the table. The table shows ink formulations and evaluation results.

Tests and Evaluations The ink compositions for water-based ballpoint pens prepared in Examples 1 to 12 and Comparative Examples 1 to 4 were used as ballpoint pen tips (ballpoint pen A refill filled in an ink storage cylinder (made of polypropylene) equipped with a tip holder with a movement amount of the tip in the vertical axis direction of the ball of 40 μm and an arithmetic average roughness (Ra) of the ball surface (Ra) of 2.0 nm). ) Attached to a gel ink ballpoint pen (trade name: G-knock) manufactured by Pilot Corporation, the following tests and evaluations were performed, and the evaluation of the color tone test and abrasion resistance test was performed using JIS P3201 writing paper A as the writing test paper. rice field.
Similarly, the water-based ink composition for writing instruments prepared in Examples 13 to 15 was filled into an ink container equipped with a nib of a commercially available marking pen (manufactured by Pilot Corporation; Super Petite (SEG-10M)) for marking. A pen was produced and subjected to the following tests and evaluations.
Further, a spiral writing test was performed using the water-based ballpoint pen ink composition of Example 1, and the ball diameter (mm) was A (mm), and the ink consumption (mg) after writing 100 m was B (mg). ), A=0.5 (mm), B=170 (mg), and B/A=340.
Further, a spiral writing test was performed using the water-based ballpoint pen ink composition of Example 2, and the ball diameter (mm) was A (mm), and the ink consumption (mg) after writing 100 m was B (mg). ), A=0.5 (mm), B=145 (mg), and B/A=290.

Ink aging test: After leaving the ballpoint pen and marking pen in an environment of 50°C for 2 months, the ink in the ink container was observed under a microscope.
No agglomeration of metal powder, no deposits, good condition ・・・◎
Agglomeration of metal powder or minute precipitates ・・・○
Aggregation of metal powder or generation of precipitates occurred, but there is no practical problem ・・・△
Poor practicality due to aggregation of metal powder or aggregation of precipitates

Color tone test: The color tone after handwriting was visually observed.
Very good metallic luster・・・◎
Good metallic luster ・・・○
Slightly inferior metallic luster ・・・△
Poor metallic luster and poor practicality ・・・×

Abrasion resistance test: Abrasion of the ball seat was measured after the writing test was completed using a running tester with a load of 100 gf, a writing angle of 65°, and a speed of 4 m/min.
Abrasion of the ball seat is less than 20μm・・・◎
Abrasion of the ball seat is 20 or more and less than 30 μm ・・・○
Wear of the ball seat is 30 or more and less than 40 μm ・・・△
Abrasion of the ball seat of 40 μm or more: ×

Air bubble generation test: The number of air bubbles was observed after leaving the pen point of the writing instrument downward for 2 months in an environment of 50°C.
No air bubbles・・・◎
Those with 1 to 2 air bubbles ・・・○
Those with 3 or more bubbles ・・・×

From the results shown in the table, in Examples 1 to 12, the ink aging test, color tone test, abrasion resistance test, and air bubble generation test all performed satisfactorily or satisfactorily. In Example 10, although the level was practically acceptable, an amine odor due to hydroxylamines was confirmed. Similarly, in Examples 13 to 15, good performance was obtained in the ink aging test, color tone test, and bubble formation test.

From the results in the table, in Comparative Examples 1 to 4, since no alkylphosphonic acid was used, the wear of the ball seat was 40 μm or more, and writing failure occurred in some cases. Agglomeration of metal powder occurred.

In the present invention, when the water-based ink composition for writing instruments is used in a ballpoint pen, a coil spring that presses the ball is arranged on the inner wall of the tip edge of the tip of the ballpoint pen to maintain the sealability of the tip of the tip of the ballpoint pen. is more preferable because it is easy to suppress entry of carbon dioxide in the atmosphere through the gap at the tip end, and it is easy to suppress the pH value of the ink in the tip from becoming acidic.
In addition, as in the examples, the refill filled with the water-based ink composition for writing instruments in the ink container cylinder is attached to the barrel and used as a writing instrument. may be used as a barrel, filled with a water-based ink composition for writing instruments, and used as a writing instrument.

The present invention is not limited to the ballpoint pens and marking pens of the examples, but can be suitably used for fountain pens, felt-tip pens, plate pens, and the like. Can be widely used as a writing instrument.

Claims (8)

A water-based ink composition for writing instruments comprising water and a metal pigment ,
The metal pigment is obtained by premixing metal powder surface-treated with alkylphosphonic acid, a solvent, and imidazolines,
Further, the alkylphosphonic acid is an alkyl group having a linear structure, and the alkyl group has 1 to 20 carbon atoms.
A water-based ink composition for writing instruments characterized by: 2. The water-based ink composition for writing instruments according to claim 1, wherein said metal pigment is in the form of a paste. 3. The water-based ink composition for writing instruments according to claim 1 , wherein the solvent comprises propylene glycol ether and lower alcohol. 4. The total mass of the alkylphosphonic acid is 0.001 to 0.5 times the total mass of the metal powder in the total mass of the ink composition. 3. The water-based ink composition for writing instruments according to . 5. The water-based ink composition for writing instruments according to claim 1 , further comprising a bubble absorbent. 6. The water-based ink composition for writing instruments according to claim 1, further comprising a surfactant. 7. The water-based ink composition for writing instruments according to claim 1, further comprising an acidic resin. 8. A writing instrument, wherein the water-based ink composition for writing instrument according to any one of claims 1 to 7 is directly packed in an ink container.