JP7424817B2 - Water-based ink composition for writing instruments, writing instruments and water-based ink products using the same - Google Patents

Description

The present invention relates to a water-based ink composition for writing instruments, writing instruments using the same, and water-based ink products. More specifically, the present invention relates to a water-based ink composition for writing instruments that has excellent antibacterial performance, pigment dispersion stability, and safety, writing instruments using the same, and water-based ink products.

Water-based ink compositions for writing instruments (hereinafter referred to as "water-based ink compositions" or "ink compositions" as the case may be) generally contain water as a main solvent, so microorganisms such as bacteria, mold, or yeast can grow. It's easy to do. Propagation of microorganisms causes the ink composition to rot, resulting in changes in the physical properties of the ink composition such as viscosity, the formation of foreign substances such as precipitates and aggregates in the ink composition, and the discoloration of the ink composition. In some cases, the function of the ink composition may be impaired. Therefore, adding antibacterial substances to ink compositions to suppress the propagation of microorganisms and the like has been actively carried out (see Patent Documents 1, 2, and 3).
However, if the same antibacterial substance is continued to be used in an ink composition, there is a possibility that microorganisms that are resistant to the antibacterial substance (hereinafter referred to as resistant bacteria) will develop and propagate. There was room.

To address the problem of the proliferation of resistant bacteria, it is being considered to improve storage stability by incorporating two or more types of antibacterial substances into inkjet ink compositions and ballpoint pen ink compositions (Patent Document 4 and 5).
However, the ink compositions disclosed in Patent Documents 4 and 5 do not have sufficient antibacterial performance against resistant bacteria and antibacterial performance against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus (black mold). There was room for.

In addition, when the ink composition is stored in an ink storage container with an opening/closing opening such as an ink bottle, or when such an ink composition is stored in a writing instrument equipped with an ink flow rate regulator having a comb-like ink storage part such as a fountain pen, such an ink composition may be used. There is a particularly high possibility that the above-mentioned problems will occur when using objects.
For example, when a conventional ink composition stored in an ink storage container is used in a fountain pen, the antibacterial performance is not sufficient, so foreign substances such as precipitates and aggregates caused by the growth of microorganisms may be present in the ink supply mechanism. may occur, and the flow path for supplying the ink composition may become narrow. As a result, the amount of ink supplied may decrease, which may affect the writing quality, such as blurring handwriting. Furthermore, if the amount of foreign matter increases or the size of aggregates becomes large, the flow path for supplying ink may be blocked by the foreign matter, making it impossible to supply ink and making it impossible to write. In addition, even if an ink composition generates a small amount of foreign matter, if it is used in a writing instrument such as a fountain pen that is repeatedly filled with ink, it may have good writing properties at the beginning of use, but after repeated filling and use. As a result, foreign matter gradually accumulates in the flow path that supplies ink, and the influence on writing performance becomes greater. If the filling and use are repeated, the accumulation of foreign matter in the flow path will further progress, and the flow path may become blocked, making it impossible to write.

Furthermore, if the ink composition itself is often exposed to the outside air, such as when the ink composition is stored in a storage container and the aqueous ink composition is taken out from the container and used by filling it into a writing instrument, There are also more opportunities for microorganisms to be contaminated. As a result, there is a strong tendency for microorganisms including resistant bacteria to proliferate abnormally, and depending on the amount of antibacterial substances added, there are problems such as insufficient antibacterial performance and a decrease in the dispersion stability of colorants. had.

Japanese Patent Application Publication No. 2015-196745 Japanese Patent Application Publication No. 2015-010124 Japanese Patent Application Publication No. 2015-010125 Japanese Patent Application Publication No. 2000-226545 Japanese Patent Application Publication No. 2003-155430

The present invention provides a water-based ink composition for writing instruments that has excellent ink storage stability, such as good dispersion stability of pigments and excellent antibacterial performance, a writing instrument using the same, and water-based ink products. .

The present invention has solved the above problems by including a water-based ink composition for writing instruments containing a colorant and an alkanediol having 4 to 10 carbon atoms.
That is, the present invention
1. A water-based ink composition for a writing instrument comprising water, a colorant, and an antibacterial substance, wherein the antibacterial substance is an alkanediol having 4 to 10 carbon atoms; A water-based ink composition for a writing instrument, characterized in that the total amount of the antibacterial substance added to the total mass of is 1,000 to 100,000 ppm.
2. 2. The aqueous ink composition for writing instruments according to item 1, wherein the colorant is self-dispersing carbon black.
3. The water-based ink composition for a writing instrument according to any one of Items 1 to 2, wherein the antibacterial substance further contains an isothiazoline-based antibacterial substance.
4. A writing instrument filled with the aqueous ink composition for writing instruments according to any one of items 1 to 3.
5. A water-based ink product obtained by storing the water-based ink composition for writing instruments according to any one of items 1 to 3 in an ink storage container. ”.

According to the present invention, it is possible to provide a water-based ink composition for writing instruments that has good pigment dispersion stability, high antibacterial performance, and excellent storage stability.

Embodiments of the present invention will be described in detail below. In this specification, "parts", "%", "ratio", etc. indicating formulations are based on mass unless otherwise specified, and content refers to the composition based on the mass of the water-based ink composition. It is mass % of the component.

The aqueous ink composition for writing instruments according to the present invention comprises water, a colorant, and an antibacterial substance, wherein the antibacterial substance is an alkanediol having 4 to 10 carbon atoms, One feature is that the total amount of the antibacterial substance added to the total mass of the aqueous ink composition for writing instruments is 1,000 to 100,000 ppm.

<Colorant>
The aqueous ink composition for writing instruments according to the present invention comprises a colorant.
As the colorant, pigments and dyes normally used in aqueous ink compositions for writing instruments can be used.

The pigment is not particularly limited as long as it can be dispersed in an aqueous medium. Examples include inorganic pigments, organic pigments, processed pigments, etc., but specific examples include carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine, azo, quinacridone, quinophthalone, and pigments, triphenylmethane series, perinone series, perylene series, dioxazine series, aluminum pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments. In addition, microcapsule pigments may be used, in which a colored body formed by dispersing a pigment in a medium as a colored resin particle body is encapsulated or dissolved in a shell body made of a resin wall forming substance using a known microencapsulation method. good. Furthermore, the pigment may be a water-dispersed pigment product that is finely and stably dispersed in an aqueous medium using a surfactant or resin in advance.
The dye is not particularly limited as long as it is soluble in the solvent. For example, direct dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming type dyes can be used.
These pigments and dyes may be used alone or in combination of two or more.

Among these colorants, pigments are preferred because they provide excellent water resistance and light resistance for handwriting, and self-dispersing carbon black is particularly preferred because it provides excellent density and water resistance for handwriting.
Self-dispersing carbon black refers to carbon black that can be dispersed in an aqueous medium without using a dispersant.For example, by subjecting carbon black to physical or chemical treatment, carbon black can be dispersed. A substance that has hydrophilic functional groups on its surface. Since self-dispersing carbon black does not contain components such as dispersants, better color development can be obtained compared to forced dispersion type carbon black dispersions. Moreover, since the ink composition has excellent redispersibility, even if the ink composition sticks to the writing tip or ink flow rate regulator of a writing instrument, it can be easily cleaned.

Examples of the physical treatment include vacuum plasma treatment, and examples of the chemical treatment include a wet oxidation method in which oxidation is performed in water with an oxidizing agent, and bonding of p-aminobenzoic acid to the pigment surface. Examples include a method of bonding a carboxyl group via a phenyl group.

The self-dispersing carbon black that can be used in the present invention is not particularly limited; for example, commercially available products include the Microjet series manufactured by Orient Chemical Industry Co., Ltd., the CAB-O-JET series manufactured by Cabot Corporation, and Tokai Carbon Co., Ltd. Examples include the Aqua-Black series manufactured by the company and the Fuji-JET Black series manufactured by Fuji Shiki Co., Ltd.

These self-dispersing carbon blacks include anionic and cationic self-dispersing carbon blacks, but the dispersion stability remains even when an alkanediol having 4 to 10 carbon atoms, which is an antibacterial substance described later, is added. It is preferable to use anionic self-dispersing carbon black because it is less likely to affect the carbon black. Further, each of the self-dispersing carbon blacks can be used alone or in a mixture of two or more types. However, when using a mixture of two or more types, it is preferable that their ionicity be the same, and it is more preferable that their surface hydrophilic groups be the same, so as not to affect the dispersion stability of carbon black. preferable.

The content of self-dispersed carbon black in the aqueous ink composition is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the aqueous ink composition. is preferably 1 to 5% by mass. When the content of self-dispersing carbon black is within the above range, it is possible to prevent deterioration in ink tracking performance to the tip of writing, and to obtain handwriting with good color development.

<Antibacterial substance>
The aqueous ink composition for writing instruments according to the present invention uses an alkanediol having 4 to 10 carbon atoms as the antibacterial substance. Alkanediols having 4 to 10 carbon atoms are safer than conventional antibacterial substances.

As the alkanediol having 4 to 10 carbon atoms, those in which the alkyl group is linear or branched can be used, and the carbon atoms substituted by the two hydroxyl groups may be in any position.
Specifically, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isopentanediol, 1,2-pentanediol, 1,3-pentanediol, 1, 4-pentanediol, 1,5-pentanediol, 3-methyl-1,3-butanediol, 2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 1,2-heptanediol, 1,3-heptanediol, 1,4-heptanediol, 1,5-heptanediol, 1,6-heptanediol, 1,7-heptanediol, 1 , 2-octanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-nonanediol, 1,9-nonanediol , 2-butyl-2-ethyl-1,3-propanediol, 1,2-decanediol, 1,10-decanediol and the like.
Among these, alkanediols having 5 to 8 carbon atoms are preferred, and alkanediols having 5 carbon atoms are more preferred, from the viewpoint of high antibacterial performance, odor, and ease of formulation. In particular, 3-methyl-1,3-butanediol has high antibacterial properties and is effective against dispersion stability of colorants, antibacterial properties of water-based ink compositions, and writing performance such as bleeding and strike-through of handwriting. , which is preferable.
These may be used alone or in combination of two or more.

Conventional antibacterial substances such as 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and 2-n-octyl-4-isothiazolin-3-one are In particular, when self-dispersing carbon black is used as a colorant, the antibacterial effect tends to decrease. This is a self-dispersing carbon black with antibacterial substances such as 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and 2-n-octyl-4-isothiazolin-3-one. It is thought that this is because the antibacterial performance of the vehicle decreases due to adsorption to the ink composition, making it difficult to obtain the original antibacterial performance of the ink composition.

However, alkanediols with a carbon number of 4 to 10 are safer than conventional antibacterial substances, so they can be added in larger amounts to the ink, so they are not adsorbed by self-dispersing carbon black. This is thought to be because the original antibacterial performance of the ink can be maintained without reducing the antibacterial performance of the vehicle.
In addition, alkanediols with 4 to 10 carbon atoms do not impair the dispersion stability of self-dispersing carbon black even when used together with antibacterial substances such as isothiazoline antibacterial substances, and have a synergistic effect on antibacterial performance. This is preferable because it can give Considering more antibacterial performance, isothiazoline antibacterial properties such as 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 2-methyl-4-isothiazolin-3-one are recommended. It is preferable to select one or more of these substances and use them in combination with an alkanediol having 4 to 10 carbon atoms.If antibacterial performance and resistant bacteria performance, which will be described later, are taken into consideration, isothiazoline antibacterial substances are It is preferable to select at least three types of isothiazoline antibacterial substances, and more preferably, to select three or more types of isothiazoline antibacterial substances.

The alkanediol having 4 to 10 carbon atoms used in the present invention does not reduce the mobility in the ink tank of a writing instrument, that is, the ink reversibility. When conventional antibacterial substances are added to an ink composition in an amount sufficient to provide sufficient antibacterial performance, there is a risk that ink reversibility may be reduced. is preferable because it can achieve both antibacterial performance and ink reversal performance.

As a writing instrument in which the aqueous ink composition for a writing instrument according to the present invention can be suitably used, a pen nib is attached to the end of the barrel via an appropriate ink flow rate regulator that adjusts the ink flow rate, and an aqueous ink composition is provided within the barrel. Examples include a writing instrument that is equipped with an ink tank that stores an ink composition.
When this type of writing instrument is placed horizontally or with the nib facing upward, when the nib is turned downward for writing, the water-based ink composition contained in the ink tank is released onto the inner wall of the ink tank. By flowing down toward the pen tip, writing becomes possible. (The mobility of this water-based ink composition is called ink reversibility.)
Many parts of writing instruments, including the ink tank, are often made of resin, which is hydrophobic, so if the wettability of the water-based ink composition is insufficient, even if the writing instrument's nib is pointing downward, Due to the drag force caused by surface tension, the aqueous ink composition does not flow down and remains in its original position. In this state, the aqueous ink composition is not supplied to the pen tip, resulting in blurred handwriting or the inability to write.
However, even if the alkanediol having 4 to 10 carbon atoms used in the present invention is added to the water-based ink composition in an amount that provides sufficient antibacterial performance, it does not affect the wettability of the water-based ink composition to the ink tank. Therefore, the ink reversibility of the water-based ink composition in the ink tank does not deteriorate, and even when the writing instrument is placed horizontally or the nib is facing upwards, it can be changed to a position where the nib is facing downwards for writing. , the water-based ink composition does not stay at its original position in the ink tank, and the ink can smoothly flow down toward the pen tip.

The amount of the alkanediol having 4 to 10 carbon atoms used in the aqueous ink composition for writing instruments of the present invention is preferably 1,000 to 100,000 ppm based on the total mass of the aqueous ink composition. More preferably, it is 1,000 to 50,000 ppm. If the amount is less than this range, the antibacterial performance tends to be slightly inferior, and when pigments are used as colorants, the dispersion stability of the pigment tends to decrease. If the amount is more than this range, ink reversibility and handwriting There is a risk that writing performance may be affected, such as bleeding or bleed-through. When it is within the above range, sufficient antibacterial performance can be obtained, it also works effectively on the dispersion stability of pigments, and there is little effect on ink reversibility and writing performance such as bleeding and strike-through of handwriting. This is preferable because it also ensures sufficient safety.

The amount of the alkanediol having 4 to 10 carbon atoms used in the aqueous ink composition for writing instruments of the present invention is preferably in a mass ratio of 1:3 to 1:0.03 based on the colorant. , more preferably 1:1 to 1:0.1. If it is within this range, it is preferable because it is good for the dispersion stability of the colorant, the antibacterial performance of the aqueous ink composition, and the writing performance such as blurring and strike-through of handwriting.

The aqueous ink composition for writing instruments of the present invention preferably further contains an isothiazoline-based antibacterial substance within a range that does not impair the performance of the ink composition.
Specifically, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl- Examples include 4-isothiazolin-3-one and 4,5-dichloro-2-octyl-4-isothiazolin-3-one.
When an alkanediol with a carbon number of 4 to 10 is used in combination with an isothiazoline antibacterial substance, when a pigment is used as a colorant, it has a synergistic effect on antibacterial performance without impairing the dispersion stability of the pigment, improving dispersion stability. This is preferable because it makes it possible to reduce the total amount of antibacterial substances while maintaining antibacterial performance, resulting in a water-based ink composition that is more safe in terms of skin irritation and the like.
In particular, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 2-methyl-4-isothiazolin-3-one are antibacterial substances that decompose even in alkaline conditions. It is preferable because it is possible to obtain an ink composition that does not irritate the skin, has good heat resistance, is negative in the Ames test, has low skin irritation, and is odorless.
Further, it is more preferable to use a plurality of isothiazoline-based antibacterial substances in combination, because in addition to the antibacterial performance against each resistant bacteria, the antibacterial performance against the other resistant bacteria is enhanced.

In the aqueous ink composition for writing instruments of the present invention, an alkanediol having 4 to 10 carbon atoms and an isothiazoline antibacterial substance may be used in combination; The mass ratio is preferably 1:0.1 to 1:0.0001, more preferably 1:0.1 to 1:0.001, and 1:0.05 to 1. :0.001 is more preferable. If it is within this range, the dispersion stability of the colorant and the antibacterial performance of the aqueous ink composition are favorable, so it is preferable.

In the aqueous ink composition for writing instruments of the present invention, an alkanediol having 4 to 10 carbon atoms and 2-phenoxyethanol can be used in combination.
When an alkanediol with a carbon number of 4 to 10 is used in combination with 2-phenoxyethanol, when a pigment is used as a colorant, it has a synergistic effect on antibacterial performance without impairing the dispersion stability of the pigment, and improves dispersion stability and antibacterial performance. This is preferable because it is possible to reduce the total amount of antibacterial substances while maintaining performance, resulting in a water-based ink composition that is more safe in terms of skin irritation and the like.

In the aqueous ink composition for writing instruments of the present invention, an alkanediol having 4 to 10 carbon atoms and 2-phenoxyethanol may be used in combination, but the addition amount ratio is based on the alkanediol having 4 to 10 carbon atoms. The mass ratio is preferably 1:10 to 1:0.1, more preferably 1:2 to 1:0.5. If it is within this range, the dispersion stability of the colorant and the antibacterial performance of the aqueous ink composition are favorable, so it is preferable.

The aqueous ink composition for writing instruments of the present invention may contain an alkanediol having 4 to 10 carbon atoms, an isothiazoline antibacterial substance, and 2-phenoxyethanol in combination, as long as the performance of the ink composition is not impaired. .
When an alkanediol with a carbon number of 4 to 10, an isothiazoline antibacterial substance, and 2-phenoxyethanol are used in combination, it has a synergistic effect on antibacterial performance, and while maintaining the dispersion stability of the colorant and antibacterial performance, it improves the skin's appearance. This is preferable because it results in a water-based ink composition with excellent safety in terms of irritation and the like.

<Water>
The water is not particularly limited, and for example, tap water, ion-exchanged water, ultrafiltrated water, distilled water, or the like can be used.

<Other ingredients>
The aqueous ink composition for writing instruments according to the present invention may contain various additives such as a wetting agent, a water-soluble organic solvent, a pH adjuster, a humectant, and a rust preventive, within a range that does not impair the effects of the present invention.

The aqueous ink composition for writing instruments according to the present invention can contain various wetting agents in order to improve the wettability of the ink flow rate regulator when used in writing instruments. The wetting agent is not particularly limited, but it is preferable to use polyetheramine. When self-dispersing carbon black is used as a colorant, polyetheramine can improve the dispersion stability of self-dispersing carbon black and maintain appropriate wettability with respect to the ink flow rate regulator.

In addition, the polyetheramine can maintain appropriate wettability to the ink flow rate regulator, so it can fully function as an ink flow rate regulator, and when the writing instrument is placed horizontally or when the pen tip is facing upward. Even when the pen tip is turned downward for writing, the ink composition can flow smoothly toward the writing tip, and good ink ejection performance from the writing tip can be maintained. Furthermore, since excess ink flows smoothly into the ink flow rate regulator, it is possible to suppress the phenomenon of ink dripping. Furthermore, when a water-based ink composition for writing instruments using polyetheramine is built into a writing instrument and used for writing, it has a high permeability into the paper surface, causing handwriting to smudge or bleed through. It is possible to obtain good handwriting.

The HLB value of the polyetheramine that can be used in the present invention is preferably 10 to 20. This is because when the HLB value of polyetheramine is 10 or more, it completely dissolves in water, and when self-dispersing carbon black is used as a colorant, it does not form aggregates with self-dispersing carbon black. Therefore, it does not affect the dispersion stability in the ink composition.

Further, the average number of added moles of ethylene oxide (EO number) of the polyetheramine is preferably 10 to 35, more preferably 13 to 30. If the average number of added moles of ethylene oxide (EO number) of the polyetheramine is within the above range, the polyetheramine has a high solubility in water, so that the effects of the polyetheramine can be stably obtained.

The polyether amines include polyoxyethylene stearylamine, polyoxyethylene (20) alkyl (C14-C18) amine, polyoxyethylene tallow alkylamine, polyoxyethylene alkylamine ether, polyoxyethylene laurylamine, polyoxyethylene Examples include alkyl (coco) amines.

The content of the polyetheramine in the aqueous ink composition for writing instruments is preferably 0.1 to 2.0% by mass, and 0.5 to 1.0% by mass, based on the total mass of the aqueous ink composition. % is more preferable.

Examples of water-soluble organic solvents include (i) glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, or glycerin, (ii) methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, and - alcohols such as butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate and other higher alcohols, and (iii) ethylene glycol monomethyl ether, ethylene glycol mono Examples include glycol ethers such as ethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol. These water-soluble organic solvents may be used alone or in combination of two or more.

Among water-soluble organic solvents, it is preferable to use a mixed solvent consisting of water and a water-soluble organic solvent that can be dissolved in water. This is because the alkanediol having 4 to 10 carbon atoms is stabilized in the ink, and the effect of dry-up resistance can be easily obtained.
Furthermore, in consideration of improving dry-up resistance, it is preferable to select and use glycols among the water-soluble organic solvents. This is because by using the glycols, the hygroscopic effect of glycols can be imparted to the ink composition, and in consideration of further improving dry-up resistance, it is preferable to use polyhydric alcohols. Among the polyhydric alcohol solvents, it is preferable to select and use one or more of ethylene glycol, diethylene glycol, and glycerin.
When a pigment such as self-dispersing carbon black is used as a colorant, the writing performance during dry-up, which occurs when the pen tip is left in the atmosphere, is likely to be poor, so it is effective. Retractable writing instruments, such as sliding type and rotary type, are effective and preferable because the pen tip is constantly left in the atmosphere, which tends to dry the tip and cause scratches when starting to write.

The amount of water-soluble organic solvent added should be determined based on the amount of water-based ink composition, considering the stability of the ink, the ability to obtain good handwriting with improved handwriting with less blurring and fading, and the improvement of dry-up resistance. It is preferably 0.1 to 10% by weight, more preferably 0.1 to 7% by weight.

Examples of pH adjusters include basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, and sodium hydroxide, basic organic compounds such as sodium acetate, triethanolamine, and diethanolamine, and lactic acid and citric acid. Considering the stability of the ink composition over time, it is preferable to use a basic organic compound, and more preferably, triethanolamine, which is weakly basic, is used. These pH adjusters may be used alone or in combination of two or more.
The content of the pH adjuster is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, based on the total mass of the aqueous ink composition.

In addition to the water-soluble organic solvents mentioned above, examples of humectants include urea, sorbitol, N,N,N-trialkyl amino acids, and the like. In particular, N,N,N-trialkyl amino acids are preferred because they have an extremely high moisture retention capacity during drying compared to other humectants. The amount of the humectant added is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, based on the aqueous ink composition.

The N,N,N-trialkyl amino acid can be represented by the following formula (1).

As R ₁ to R ₃ , a wide variety of linear or branched alkyl groups can be used. Specifically, examples thereof include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and tert-butyl group. Note that R ₁ to R ₃ may be the same or different. Specifically, n=1 trimethylglycine, triethylglycine, tripropylglycine, triisopropylglycine, n=2 trimethyl-β-alanine, n=3 trimethyl-γ-aminobutyric acid, and the like. Considering the improvement in dry-up resistance performance and the storage stability of the aqueous ink composition, it is preferable to select and use trimethylglycine.

Examples of the rust inhibitor include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, and dialkylthiourea.

Chelating agents include ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol etherdiaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), and dihydroxyethylglycine (DHEG). ), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and their alkali metal salts, ammonium salts, or amine salts.

Among the writing instruments filled with the aqueous ink composition for writing instruments of the present invention, for example, a writing instrument equipped with an ink flow rate regulator having a comb-like ink retention part, such as a fountain pen, can be repeatedly refilled with ink by the user. Refill ink may be contained in an ink container such as a glass bottle. Glass bottles are cheap, easy to mold, and easy to obtain the desired strength, but on the other hand, especially when inexpensive and versatile soda lime glass is used, it is difficult to store water-based ink compositions for long periods of time. There is a high possibility that the alkaline component in the glass will be eluted into the aqueous ink composition, and the eluted alkali component and the components of the aqueous ink composition may react to form a precipitate. Therefore, in the aqueous ink composition used in the present invention, the alkali component eluted from the glass ink container is captured, and the alkali component reacts with the components in the aqueous ink composition to form water-insoluble precipitates. It is preferable to contain the above-mentioned chelating agent, which can prevent the occurrence of such occurrences and prevent the ink flow path from being blocked by generated precipitates and the like, resulting in blurred handwriting or inability to write.
Among the above-mentioned chelating agents, aminocarboxylic acids and their salts are preferably used, considering that they can sufficiently supplement the alkaline component and that the physical properties and performance of the water-based ink composition are unlikely to change before and after the chelating agent is added. is preferable, and more preferably, ethylenediaminetetraacetic acid (EDTA) and its salts are used.

When a pigment such as self-dispersing carbon black is used as a colorant, the effect of stabilizing the pigment dispersion can be obtained without using a dispersant, so even when the ink viscosity is adjusted to a low viscosity, the pigment It is particularly effective for low viscosity inks because it can suppress sedimentation.
Therefore, the viscosity of the water-based ink composition for writing instruments is preferably 50 mPa·s or less, and 1.0 to 10 mPa·s, as measured using a B-type rotational viscometer at a rotational speed of 60 rpm and 20°C. More preferably, it is s. If it is larger than this range, ink will not be stably supplied to the writing tip, especially when used with a writing instrument equipped with an ink flow regulator having a comb-shaped ink retention part, resulting in blurred handwriting or inability to write. There is a fear. More preferably, it is 1.0 to 3.0 mPa·s, and still more preferably 1.0 to 2.0 mPa·s. If the ink viscosity is within the above range, when used in a writing instrument in which the pen core is arranged as an ink flow regulator, ink will be stably supplied to the writing tip and good handwriting will be obtained. This is because performance can be improved.

The ink viscosity in the present invention can be measured according to JIS Z 8803:2011 using a B-type rotational viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd.).

The surface tension at 20° C. of the aqueous ink composition for writing instruments according to the present invention is preferably 30 to 70 mN/m, more preferably 35 to 65 mN/m. If the surface tension of the aqueous ink composition is within the above numerical range, when used in a writing instrument equipped with an ink flow rate regulator having a comb-like ink retention part, the wettability to the ink flow rate regulator can be maintained appropriately. can be kept. Therefore, even when the internal pressure of the ink storage section increases, overflowing ink smoothly enters the ink storage section within the pen core, making it possible to effectively suppress ink dripping from the writing tip. . Furthermore, since the wettability of the writing surface is maintained appropriately, it is possible to prevent the resulting handwriting from blurring, from drying out, and from being rubbed and smudged. Note that the surface tension is determined by measuring with a surface tension measuring device (model: DY-200, manufactured by Kyowa Interface Science Co., Ltd., in a 20° C. environment, platinum plate, vertical plate method).

<Method for manufacturing ink composition>
The aqueous ink composition for writing instruments according to the present invention can be produced by any conventionally known method. Specifically, the above-mentioned components can be mixed in required amounts and mixed using various stirrers such as a propeller stirrer, homodisper, homomixer, and planetary stirrer, and various dispersion machines such as a bead mill.

<Writing implements>
The aqueous ink composition for writing instruments of the present invention can be used in writing instruments such as marking pens and ballpoint pens with a fiber tip, felt tip, plastic tip, or ballpoint pen tip, and fountain pens with a metal nib. .

The writing instrument of the present invention may be configured to be directly filled with an aqueous ink composition, or may be provided with an ink container or an ink storage body capable of being filled with an aqueous ink composition.

The mechanism for ejecting and retracting the pen tip in the writing instrument of the present invention is not particularly limited, and examples thereof include a cap type that includes a cap that covers the pen tip, a knock type, a rotating type, and a sliding type. Alternatively, it may be a retractable type in which the pen tip can be accommodated within the barrel.

Further, the ink supply mechanism of the writing instrument is not particularly limited. (2) A mechanism for supplying the water-based ink composition to the nib by providing a flow rate adjustment member having a groove-toothed ink retention section, and (3) A mechanism for supplying the water-based ink composition to the pen tip using the flow rate adjustment member having a groove-toothed ink retention portion. Examples include a mechanism for supplying the composition to the pen nib, and (4) a mechanism for directly supplying the aqueous ink composition to the pen nib from an ink container or barrel equipped with the pen nib.

The writing instrument used in the present invention has a writing tip and an ink storage section, and between the writing tip and the ink storage section, ink can be supplied from the ink storage section to the writing tip, and overflow occurs as the internal pressure of the ink storage section increases. It is preferable to use a writing instrument equipped with an ink flow rate regulator having a comb-shaped ink storage part that temporarily holds the ink that has been absorbed. The ink flow regulator having the comb-shaped ink storage section supplies the water-based ink composition from the ink storage section to the writing tip, and temporarily removes the water-based ink composition that overflows as the internal pressure of the ink storage section increases. It is possible to maintain the Specific examples of the writing implement include fountain pens, ballpoint pens, calligraphy pens, and the like.

In other embodiments, the writing instrument is a marking pen, the nib may be, for example, without limitation, a fiber tip, a felt tip or a plastic tip, and the shape is bullet-shaped, chisel-shaped, etc. Alternatively, it may be in the form of a brush pen.

In other embodiments, the writing instrument is a ballpoint pen, preferably a ballpoint pen equipped with an ink backflow preventer.

<Water-based ink products>
The water-based ink product for writing instruments of the present invention can be used in a water-based ink product containing an ink composition in an ink storage container. In particular, the ink storage container has an opening/closing opening for dispensing ink, and the ink composition separated from the ink storage container is filled into a writing instrument having an ink flow rate regulator having a comb-like ink retention section. It is preferable to use it for water-based ink products.

As the ink storage container used in the present invention, an ink storage container used for ordinary ink storage or refillable ink can be used. Specific examples include ink bottles made of glass and containers made of resin such as polyethylene, polypropylene, and polyethylene terephthalate.

A water-based ink composition for writing instruments was obtained using the following formulation and method.
(Example 1)
Self-dispersed carbon black 1 15.0% by mass
(Product name: Fuji Jet Black-20, manufactured by Fuji Color Co., Ltd., ionicity: anionic carbon black 20% water dispersion)
3-Methyl-1,3-butanediol 3.0% by mass (equivalent to 30,000ppm)
Triethanolamine (pH adjuster) 1.0% by mass
1,2-benzisothiazolin-3-one 0.0045% by mass (45ppm equivalent)
2-n-octyl-4-isothiazolin-3-one 0.0045% by mass (45ppm equivalent)
Ion-exchanged water Remainder An antibacterial substance and a pH adjuster were added to the ion-exchanged water and mixed by propeller stirring to obtain a base liquid. Thereafter, self-dispersing carbon black was added to the base liquid and mixed by propeller stirring to obtain a water-based ink composition for writing instruments. The viscosity of the obtained aqueous ink composition for writing instruments was measured according to JIS Z 8803:2011 using a B-type rotational viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd., sample amount: 20 ml). Specifically, the ink viscosity at 20° C. and a rotational speed of 60 rpm was 1.60 mPa·s. In addition, the surface tension of the obtained aqueous ink composition was measured using a surface tension measuring device (model: DY-200, manufactured by Kyowa Interface Science Co., Ltd., in a 20°C environment, platinum plate, vertical plate method), and found to be 57. It was .8 mN/m.

(Examples 2 to 4, Comparative Example 1)
An antibacterial substance, a water-soluble organic solvent (diethylene glycol), and a pH adjuster are added to ion-exchanged water, mixed by propeller stirring to obtain a base liquid, and the ink composition is formulated as shown in (Table 1). Aqueous ink compositions for writing instruments of Examples 2 to 4 and Comparative Example 1 were obtained in the same manner as in Example 1, except for the following.

自己分散型カーボンブラック１：商品名：Ｆｕｊｉ Ｊｅｔ Ｂｌａｃｋ－２０ 冨士色素株式会社製、イオン性：アニオン カーボンブラック２０％水分散体

Self-dispersing carbon black 1: Product name: Fuji Jet Black-20, manufactured by Fuji Color Co., Ltd., ionicity: anionic carbon black 20% aqueous dispersion

(Dispersion stability test)
The aqueous ink compositions for writing instruments of Examples 1 to 4 and Comparative Example 1 were filled into a 30 ml screw tube, left at room temperature for 4 weeks, and the ink compositions at the top and bottom of the screw tube were observed under a microscope.
A: The pigment was uniformly dispersed in both the top and bottom parts, and the dispersion stability was good.
B: Slight aggregation of pigment was observed, and there was less pigment at the top than at the bottom.
C: Pigment aggregates were observed, and there was less pigment at the top than at the bottom, and uniform dispersion was not obtained.

(Antibacterial performance test)
In the water-based ink compositions for writing instruments of Examples 1 to 4 and Comparative Example 1, Aspergillus sp. (BIT-resistant bacteria) were inoculated at approximately 1.0 x 10 ⁶ cells per ml, and each ink composition after being left for 3 days was used as a test ink. Each test ink was cultured at 28° C. for 7 days using the pour plate method on a potato dextrose agar medium, and the antibacterial performance was evaluated based on the number of bacteria detected.
A: The number of bacteria detected is less than 1×10 ⁰ cfu/ml.
B: The number of bacteria detected is 1×10 ⁰ cfu/ml or more and less than 1×10 ² cfu/ml.
C: The number of bacteria detected is 1×10 ² cfu/ml or more and less than 1×10 ⁶ cfu/ml.
D: The number of bacteria detected is 1×10 ⁶ cfu/ml or more.

(Safety evaluation)
The safety of the water-based ink compositions for writing instruments of Examples 1 to 4 and Comparative Example 1 was evaluated according to the following evaluation criteria.
A: The amount of the isothiazoline antibacterial substance added is less than 100 ppm.
B: The amount of the isothiazoline antibacterial substance added is 100 ppm or more and less than 500 ppm.
C: The amount of the isothiazoline antibacterial substance added is 500 ppm or more.

(Written performance test)
The water-based ink compositions for writing instruments of Examples 1 to 4 and Comparative Example 1 were injected into a polyethylene ink cartridge, and the cartridge was attached to a fountain pen manufactured by Pilot Corporation (product name: Custom 74, pen type M), and a writing paper A was used. I wrote down the . The handwriting at that time was visually observed.
A: Good handwriting was obtained without any bleeding or strike-through.
B: Bleeding and strike-through occurred in the handwriting.
C: Severe bleeding and strike-through occurred in the handwriting.

(Ink reversibility test in ink tank)
The fountain pen used in the writing performance test was placed with the pen tip facing upward, and all the aqueous ink composition in the filled ink tank was dropped from the pen tip side to the opposite side of the pen tip. After this, when the pen tip is gently turned downward, visually check how the water-based ink composition flows down to the pen tip side in the ink tank, and evaluate the ink reversal performance in the ink tank according to the following criteria. did.
A: The water-based ink composition completely flowed down to the pen tip side of the ink tank within 10 seconds.
B: Most of the water-based ink composition flowed down to the pen tip side of the ink tank within 10 seconds, but some of the water-based ink composition did not flow down and remained on the wall inside the ink tank.
C: All of the water-based ink composition did not flow down to the pen tip side of the ink tank even after 10 seconds had passed.

The aqueous ink composition for writing instruments of the present invention can be used for various writing instruments such as fountain pens, ballpoint pens, calligraphy pens, calligraphy pens, and various markers. In particular, since storage stability and safety are improved, it can be suitably used as an ink composition for writing instruments, such as fountain pens and dip pens, where the ink is often exposed to the outside air.

Claims (6)

A water-based ink composition for writing instruments, comprising water, a colorant, an antibacterial substance , and 2-phenoxyethanol , wherein the antibacterial substance is 3-methyl-1,3-butanediol; The total amount of the antibacterial substance added to the total mass of the ink composition is 1,000 to 100,000 ppm, and the ratio of the amounts of 3-methyl-1,3-butanediol to 2-phenoxyethanol is 3-methyl-1,3-butanediol and 2-phenoxyethanol. A water-based ink composition for writing instruments , characterized in that the mass ratio is 1:2 to 1:0.5 based on -1,3-butanediol . The aqueous ink composition for writing instruments according to claim 1, characterized in that the aqueous ink composition for a writing instrument contains two or more selected isothiazoline-based antibacterial substances as the antibacterial substance. The aqueous ink composition for writing instruments according to claim 1 or 2, wherein the colorant is self-dispersing carbon black. A writing instrument filled with the aqueous ink composition for a writing instrument according to any one of claims 1 to 3 . 5. The writing instrument according to claim 4 , further comprising an ink flow rate regulator having a comb-shaped ink reservoir. A water-based ink product obtained by storing the water-based ink composition for writing instruments according to any one of claims 1 to 5 in an ink storage container.