JP7210264B2 - Water-based ink composition for writing instruments - Google Patents

Description

The present invention relates to a water-based ink composition for writing instruments. More particularly, it relates to a water-based ink composition for writing instruments which is excellent in the drying property of handwriting.

The main solvent of the water-based ink composition for writing instruments is water. For this reason, for example, if the pen tip of a water-based ballpoint pen continues to be exposed to the atmosphere, water evaporates from the pen tip, increasing the viscosity of the ink at that portion, which may result in blurred handwriting. Therefore, in order to suppress evaporation of water in the ink composition, it is common practice to add a polyhydric alcohol solvent such as glycerin or ethylene glycol. Although drying of the nib can be suppressed by this method, it takes time to completely dry the resulting handwriting. At this time, if the handwriting that is not dry is touched, the writing surface or the handwriting itself may become dirty.

On the other hand, it has been studied to prevent staining of the writing surface by lowering the surface tension of the ink composition and improving the penetrability of the ink composition into a writing object such as a paper support. For example, many proposals have been made to add a specific alcohol or a specific surfactant to the ink composition. However, there is a demand for further improvements in terms of improving the penetrability of the ink composition and the dryness of handwriting.

Japanese Unexamined Patent Application Publication No. 2012-77102

The present invention provides an ink composition that has improved penetrability into writing objects and excellent handwriting drying properties. Furthermore, the present invention provides a writing utensil using the same.

（式中、
Ｒ^１は、炭素数１～６の、直鎖または分岐の、アルキル基であり、かつ
Ｒ^２およびＲ^３は、それぞれ独立に、水素、または炭素数１～４の、直鎖もしくは分岐の、アルキル基である）
を含んでなる、筆記具用水性インキ組成物であって、
前記アミド化合物の含有量が、前記組成物の総質量を基準として、１～３５質量％であることを特徴とするものである。 The water-based ink composition for writing instruments according to the present invention is
water and,
a coloring agent;
an amide compound represented by formula (1);

(In the formula,
R ¹ is a straight or branched alkyl group having 1 to 6 carbon atoms, and R ² and R ³ are each independently hydrogen or a straight or branched chain having 1 to 4 carbon atoms, alkyl group)
A water-based ink composition for writing instruments comprising
The content of the amide compound is 1 to 35% by mass based on the total mass of the composition.

A writing instrument according to the present invention is characterized by containing the water-based ink composition described above.

When the ink composition according to the present invention is used, the penetrability of the composition to the writing object is improved, and as a result, the drying property of the writing surface can be improved. By using such an ink composition, handwriting is prevented from being smeared.

Aqueous Ink Composition for Writing Instruments The aqueous ink composition for writing instruments according to the present invention (hereinafter sometimes referred to as "ink composition") comprises water, a colorant, and an amide compound having a specific structure.

<Water>
The water used in the present invention is not particularly limited, and for example, ion-exchanged water, ultrafiltered water, distilled water, or the like can be used. The ink composition in the present invention contains water as a main solvent. The content of water is 50 to 95% by mass, based on the total mass of the water in the ink composition, the amide compound represented by formula (1), and the water-soluble organic solvent described later, which is optionally included. Preferably, it is 60 to 90% by mass.

<Colorant>
The coloring agent used in the present invention is not particularly limited and may be selected appropriately from dyes, pigments and the like.

Dyes that can be used in the present invention are not particularly limited as long as they are soluble or dispersible in an aqueous medium. Examples thereof include various dyes such as acid dyes, basic dyes, reactive dyes, direct dyes, disperse dyes and food colorings, and these can be used alone or in combination of two or more. The content of the dye is preferably 0.1 to 20% by mass, more preferably 0.1 to 10% by mass, based on the total mass of the ink composition.

Specifically, as the acid dye, C.I. I. Acid Red 18, C.I. I. Acid Red 51, C.I. I. Acid Red 52, C.I. I. Acid Red 87, C.I. I. Acid Red 92, C.I. I. Acid Red 289, C.I. I. Acid Orange 10, C.I. I. Acid Yellow 3, C.I. I. Acid Yellow 7, C.I. I. Acid Yellow 23, C.I. I. Acid Yellow 42, C.I. I. acid green 3, C.I. I. Acid Green 16, C.I. I. acid blue 1, C.I. I. Acid Blue 9, C.I. I. Acid Blue 22, C.I. I. Acid Blue 90, C.I. I. Acid Blue 239, C.I. I. Acid Blue 248, C.I. I. Acid violet 15, C.I. I. Acid Violet 49, C.I. I. Acid Black 1, C.I. I. Acid Black 2 and basic dyes such as C.I. I. Basic Orange 2, C.I. I. Basic Orange 14, C.I. I. Basic Green 4, C.I. I. Basic Blue 9, C.I. I. Basic Blue 26, C.I. I. Basic Violet 1, C.I. I. Basic Violet 3, C.I. I. Basic Violet 10, and as a direct dye, C.I. I. Direct Red 28, C.I. I. Direct Yellow 44, C.I. I. Direct Blue 86, C.I. I. Direct Blue 87, C.I. I. Direct Violet 51, C.I. I. Direct Black 19, food coloring such as C.I. I. Food Yellow 3, C.I. I. Food Black 2 and the like.

Pigments that can be used in the present invention include inorganic, organic, and processed pigments. Specifically, carbon black, aniline black, ultramarine blue, chrome, titanium oxide, iron oxide, phthalocyanine, azo, Examples include quinacridone-based, quinophthalone-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, aluminum pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, and complementary color pigments. In addition, microcapsule pigments obtained by encapsulating or solid-solubilizing 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, liquid crystals, Microcapsule pigments encapsulating functional materials such as reversible thermochromic compositions and photochromic materials may also 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 dyes and pigments may be used alone or in combination of two or more. The content is preferably 1 to 30% by mass based on the total mass of the ink composition.
In addition, conventionally, since pigments are dispersed in ink compositions, they tend to have poorer penetrability into writing objects than dye-based ink compositions, making it difficult to improve handwriting drying properties. However, in the present invention, even when a pigment is used as the colorant, the handwriting drying property can be improved. Furthermore, by using a surfactant described later, the handwriting drying property can be further improved. Furthermore, the pigment is excellent in water resistance and light resistance, and good color development can be obtained. For the above reasons, it is preferable to use a pigment as the coloring agent.

式中、
Ｒ^１は、炭素数１～６の、直鎖または分岐の、アルキル基であり、かつ
Ｒ^２およびＲ^３は、それぞれ独立に、水素、または炭素数１～４の、直鎖もしくは分岐の、アルキル基である。 <Amide compound>
The amide compound used in the present invention is represented by formula (1).

During the ceremony,
R ¹ is a straight or branched alkyl group having 1 to 6 carbon atoms, and R ² and R ³ are each independently hydrogen or a straight or branched chain having 1 to 4 carbon atoms, is an alkyl group.

Preferably, R ¹ is a straight-chain alkyl group having 1 to 4 carbon atoms, and both R ² and R ³ are methyl groups.
R ¹ is more preferably methyl or butyl, more preferably methyl.

The content of the amide compound represented by formula (1) may vary depending on the type and content of other additives, but is 1 to 35% by mass based on the total mass of the ink composition. If it is less than 1% by mass, the effect will be insufficient, and if it is more than 35% by mass, the amount of solvent will be too large, the solubility of various components contained in the ink composition will be too low, and pigments, resin particles, etc. will be dispersed. Stability tends to be compromised. It is preferably 1 to 30% by mass, more preferably 3 to 30% by mass, and particularly preferably 10 to 30% by mass.

Although not bound by theory, it is considered as follows. The main solvent of the water-based ink composition of the present invention is water, and water is known as a characteristic solvent in which a plurality of water molecules form a cluster structure due to strong hydrogen bonding. Water is a low-molecular substance with a simple chemical structure, but due to its strong hydrogen bonding and cluster structure, it has high surface tension and high heat capacity. Known as solvent. It is believed that the amide group contained in the structure of the amide compound represented by formula (1) used in the present invention acts to effectively break the hydrogen bond of water and has the effect of refining the cluster structure. . Therefore, it is considered that the surface tension is lowered and the permeability is improved. In addition, it is considered that the volatility is improved by making the cluster structure finer, and the handwriting drying property is more effectively improved. For the above reason, by including a specific amount of the amide compound represented by the formula (1) used in the present invention, the penetrability of the ink composition into the writing object, etc. is improved, and as a result, the writing dryness is remarkably improved. presumed to be improved.

<Other additives>
The ink composition according to the present invention can be used in various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens and various marking pens. Water-soluble organic solvents, humectants, surfactants, lubricants, polysaccharides, shear thinning agent, pH Various additives such as modifiers, rust inhibitors, antiseptics, water-soluble resins, and organic resin particles may be included.

The ink composition according to the present invention may contain a water-soluble organic solvent for the purposes of dissolution stability, prevention of moisture evaporation and drying, and the like. 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, t - 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 Glycol ethers such as ethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol are included. The content of the water-soluble organic solvent is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, based on the total mass of the ink composition.
When the ink composition according to the present invention contains the water-soluble organic solvent, the effect of the present invention may be obtained even if the content of the amide compound is relatively small. In order to obtain such effects, the total content of the amide compound and the water-soluble organic solvent is preferably 1 to 45% by mass based on the total mass of the ink composition. For example, even if the content of the amide compound is reduced to about one-half, a sufficient permeability-improving effect may be obtained by using a water-soluble organic solvent such as glycols in combination. However, the water-soluble organic solvent alone does not produce the effect of the amide compound. Therefore, it is generally preferable that the content of the amide compound is large, so the mass of the amide compound based on the total mass of the amide compound and the water-soluble organic solvent is preferably 10% by mass or more, more preferably. is 30% by mass or more, more preferably 70% by mass or more.

The ink composition according to the present invention may contain a humectant such as urea and sorbitol in addition to the water-soluble organic solvent described above for the purpose of preventing water evaporation. In this specification, the water-soluble organic solvent mentioned above is not included in the moisturizing agent. The content of the humectant is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, based on the total mass of the ink composition.

The ink composition according to the present invention may contain various surfactants such as nonionic, anionic and cationic surfactants. Also included are surfactants having acetylene bonds in their structures, silicone-based surfactants, and the like.

In the present invention, an ink composition having more preferable properties can be obtained by containing a specific surfactant and a specific water-soluble organic solvent. The surfactant contained in the ink composition can remarkably reduce the surface tension of the interface surface such as the gas-liquid interface or the liquid interface by arranging the molecules of the surfactant at the interface. In addition, since the water-soluble organic solvent can break the hydrogen bonds of water and reduce the surface tension, the surface tension of the entire ink composition can be reduced regardless of whether it is at the interface or inside the solvent. A synergistic effect can be obtained by combining an amide compound having a different mechanism of action as described above with a surfactant. In particular, the combination of the specific amide compound used in the present invention and a surfactant having a specific acetylene bond in its structure or a specific silicone surfactant can provide an ink composition having excellent hand-drying properties.

A surfactant having an acetylene bond in its structure or a silicone-based surfactant can be included in order to further improve the drying property of handwriting.

The surfactant having an acetylene bond in its structure, which is used in the ink composition according to the present invention, preferably has 10 or less moles of ethylene oxide added.
A surfactant having an acetylene bond in its structure with an ethylene oxide addition mole number of 10 or less is a surfactant having an ethylene oxide-added acetylene bond in its structure, and the surfactant has an ethylene oxide addition mole number of 10 or less. The number is 10 or less. Examples thereof include acetylene glycol-based surfactants having 10 or less ethylene oxide addition moles and acetylene alcohol-based surfactants having 10 or less ethylene oxide addition moles.
A surfactant having an acetylene bond in its structure with 10 or less ethylene oxide addition moles can remarkably improve the penetrability to a writing object. For this reason, the ink composition containing a surfactant having an acetylene bond in its structure can quickly penetrate into paper, so that the handwriting formed on the surface of the object to be written is completely dried. The composition has excellent handwriting drying properties, which shortens the time until the handwriting is removed, prevents the composition from adhering to the part where the handwriting is not present, and prevents the composition from being removed from the handwriting part when the handwriting part is rubbed. becomes.

Although the reason for this is not clear, it is because a surfactant having an acetylene bond in its structure with 10 or less ethylene oxide addition moles exhibits a suitable balance between hydrophobicity and hydrophilicity for exhibiting a penetrating effect. It is believed that there is. Considering the enhancement of the effects of surfactants having acetylene bonds in their structure, the number of moles of ethylene oxide added is preferably 8 or less. Furthermore, the number of moles of ethylene oxide to be added is preferably 4 or more. When the number of moles of ethylene oxide added is 4 or more, the solubility of the surfactant is lowered, and it becomes difficult to stably exist in the ink composition, which can prevent the deterioration of the stability of the effect of the surfactant over time.
In order for the ink composition to quickly permeate a writing object after writing, it is necessary to suitably control the surface tension of the ink composition after writing. The behavior of surfactant molecules in ink is important for instantly controlling the surface tension associated with writing action, the so-called dynamic surface tension, and for obtaining rapid penetrability into the writing target. Surfactant molecules quickly arrange at the gas-liquid interface under dynamic conditions, and in order to control the surface tension instantaneously and effectively, it is possible to use a surfactant with a specific structure. It is possible to obtain an ink composition having excellent handwriting drying properties.

In addition, a surfactant having an acetylene bond in its structure with an ethylene oxide addition mole number of 10 or less has the effect of improving the writing feeling, such as improving the drying property of handwriting and at the same time providing a smooth writing feeling. . This is because the ink composition contains a surfactant having an acetylene bond in its structure, thereby improving the lubricity between the ball of the ballpoint pen and the ballpoint pen tip and suppressing wear of the ball seat. because it can
The ink composition according to the present invention, which contains a surfactant having an acetylene bond in its structure, can contain other lubricants. It is preferable to use together with an acid ester surfactant.

Further, the surfactant having an acetylene bond in its structure used in the present invention may further have propylene oxide added thereto. In consideration of further improvement in handwriting drying property and stability over time of the ink composition, in the present invention, a surfactant having in its structure an acetylene bond to which ethylene oxide and propylene oxide are further added is selected. It is preferable to use This is because a surfactant having an acetylene bond in its structure has a better balance of hydrophobicity and hydrophilicity when both ethylene oxide and propylene oxide are added.
The ratio of the number of moles of ethylene oxide added to the number of moles of propylene oxide added can maintain a suitable balance between the hydrophobicity and hydrophilicity of the surfactant having an acetylene bond in its structure, and considering further improvement in the drying property of handwriting, the ratio of ethylene oxide The number of moles added: the number of moles of propylene oxide added is preferably 1:1 to 5:1.

In addition, the total number of moles of ethylene oxide added and that of propylene oxide added is preferably 10 or less in consideration of the alignment property to the gas-liquid interface. If the number of added moles is too large, the surfactant molecules tend to be too long, and steric hindrance tends to occur when arranging at the gas-liquid interface. It is particularly preferable because it maintains a suitable balance between hydrophobicity and hydrophilicity, and also provides an effect that takes into consideration the influence of steric hindrance during alignment on the air-liquid interface.
Furthermore, in consideration of the improvement of handwriting drying property and the stability of the ink composition over time, a surfactant having an ethylene oxide addition mole number of 5 and a propylene oxide addition mole number of 2 having an acetylene bond in the structure is used. It is more preferable to use

The HLB value of the surfactant having an acetylene bond in its structure is preferably 3-14, more preferably 6-12, and particularly preferably 7-9. When the HLB value of the surfactant having an acetylene bond in its structure is 3 or more, it is preferable because it can stably exist without being dissolved in water, which is a solvent, and can be effective initially and over time. .

Surfactants having an acetylene bond in their structure include, for example, acetylene alcohol-based surfactants and acetylene glycol-based surfactants. It is preferable to use an acetylene glycol-based surfactant, considering that it is easy to use.

Specific examples of surfactants having an acetylene bond in their structure include Olphine series, Surfynol series, and Dynol series (all manufactured by Nissin Chemical Industry Co., Ltd.).

The silicone-based surfactant balances the Si skeleton in the structure, the hydrophobic group such as propylene oxide, and the hydrophilic group such as ethylene oxide, and is suitable, so that it is stable in the ink composition and the active agent Since the molecules are readily arranged at the air-liquid interface, the surface tension of the ink composition can be quickly controlled during writing, and the permeability can be improved. can. Among silicone surfactants, it is preferable that the weight average molecular weight is 500 to 3,000. Regarding the alignment of the surfactant to the gas-liquid interface, if the weight average molecular weight exceeds 3,000, the molecules of the silicone-based surfactant become too large, and the alignment of the surfactant to the gas-liquid interface tends to be delayed. Therefore, the handwriting drying property may not be sufficient. On the other hand, when the weight-average molecular weight is 3,000 or less, the molecules of the silicone-based surfactant become relatively small, so that the molecules of the surfactant tend to be rapidly arranged at the gas-liquid interface, resulting in a poor handwriting. Easy to improve drying. Also, if the weight average molecular weight is less than 500, it is difficult to obtain the desired handwriting drying property. Considering the above effects, the weight average molecular weight is preferably 500 to 3,000, more preferably 500 to 2,000. It is preferably between 000 and 2,000.

In addition, silicone-based surfactants have the effect of improving the writing feeling, such as improving the dryness of handwriting and providing a smooth writing feeling. This is because the ink composition containing a silicone surfactant improves the lubricity between the ball of the ballpoint pen and the tip of the ballpoint pen, and can suppress wear of the ball seat. be.
The ink composition according to the present invention containing a silicone surfactant can contain other lubricants. In particular, among the lubricants, a phosphoric acid ester surfactant described later It is preferable to use in combination with

Regarding the solubility parameter (hereinafter referred to as SP value) of the silicone surfactant, the SP value is preferably 8 to 13 in consideration of the dryness of handwriting, and more preferably, the SP value is 9 to 12. is preferred, and an SP value of 10 to 11 is particularly preferred. The SP value of water, which is the main component of the solvent, is 23.4. tend to be difficult to achieve. When the SP value is within the above range, the molecules of the activator are readily arranged at the gas-liquid interface, and stability in the ink composition is also obtained, which is preferable.

Specific examples of silicone surfactants include Silface series (manufactured by Nissin Chemical Industry Co., Ltd.), BYK series (manufactured by BYK Chemie Co., Ltd.), Silsoft Spread series, and Coatosil series (all of which are manufactured by Momentive Performance Materials Co., Ltd.). ) and the like. You may use these individually or in mixture of 2 or more types.

Further, the total content of the surfactant having an acetylene bond in its structure or the silicone surfactant is more preferably 0.01 to 3.0% by mass based on the total mass of the ink composition. This is because if the total content of a surfactant having an acetylene bond in its structure or a silicone surfactant is less than 0.01% by mass, it is difficult to obtain the desired handwriting drying property, and 3.0% by mass , the stability of the ink composition over time is likely to be affected. Furthermore, taking into consideration, 0.05 to 2.0% by mass is preferable, and 0.1 to 1.5% by mass is particularly preferable.

In addition, the ink composition according to the present invention may further contain a phosphate surfactant. The phosphate ester-based surfactant has the effect of improving the dispersibility of the ink composition, and also acts as a lubricant when the ink composition is used for a ball-point pen. Lubricants improve the lubricity between the ball of the ballpoint pen and the ballpoint pen tip to smoothen the rotation of the ball, thereby suppressing the wear of the ball seat and improving the writing feel. The phosphate ester surfactant having a phosphate group used in the present invention has the property that the phosphate group easily adsorbs to metal, so it improves lubricity, suppresses wear of the ball seat and improves writing comfort. Easy to improve. Therefore, when the ink composition according to the present invention is applied to a ballpoint pen, particularly excellent writing feel can be achieved. However, since this surfactant contributes not only to the improvement of lubricity but also to the improvement of dispersibility, it works effectively even when the ink composition is used for writing instruments other than ballpoint pens.

Furthermore, the phosphate surfactant also has the effect of adjusting the surface tension. For this reason, in a writing instrument having a comb groove-shaped ink flow control member, which will be described later, and a supply mechanism for supplying an ink composition to the pen tip, the wettability of the ink flow control member is excellent. It is preferred because it exhibits character. Therefore, the ink composition according to the present invention is also preferable for fountain pens, marking pens, felt-tip pens, ball-point pens and the like having comb groove-shaped ink flow control members.

Phosphate ester surfactants include linear alcohol surfactants, styrenated phenol surfactants, nonylphenol surfactants, and octylphenol surfactants. It is preferable to use a phosphate ester surfactant.

In the present invention, the phosphate surfactant preferably has an HLB value of 5-15, more preferably 6-13. In the present invention, the number of carbon atoms in the alkyl group or alkylallyl group of the phosphate ester-based surfactant is preferably 6 to 30, more preferably 8 to 18, and more preferably 10 to 14. Especially preferred. This is because linear phosphate ester surfactants with a specific HLB value and carbon number have excellent writing stability, such as stably obtaining good handwriting with improved line scatter and blurring. In addition, it is possible to synergistically improve the dispersing effect together with the dispersant used in the present invention, and at the same time provide a lubricating effect.

In the present invention, the HLB value of the phosphate ester-based surfactant means the HLB value of the raw material nonionic surfactant for the phosphate ester-based surfactant, which is calculated by the Kawakami method. and is calculated by the following formula.
HLB = 7 + 11.7 log (Mw/Mo), (Mw; molecular weight of hydrophilic group, Mo; molecular weight of lipophilic group)

Specific examples of phosphate ester surfactants include Plysurf series (Daiichi Kogyo Seiyaku Co., Ltd.), and linear alcohol phosphate ester surfactants include Plysurf A212C, Examples include A208B, A213B, A208F, A215C, A219B, and A208N. Examples of styrenated phenol-based phosphate surfactants include PRLYSURF AL, and examples of nonylphenol-based surfactants include PRLYSURF. 207H, A212E, and A217E, and the octylphenol type includes PLYSURF A210G.

When the ink composition according to the present invention contains a phosphate ester surfactant, its content is preferably 0.1 to 2.0% by mass, preferably 0.5 to 1.5% by mass, based on the total mass of the ink composition. % by mass is more preferred.
A ball-point pen can achieve excellent writability when the ink composition forms an appropriate film between the ball and the ball seat at the nib. Phosphate ester-based surfactants are effective in forming such a film, so it is preferable to use a phosphate ester-based surfactant in the ink composition used for ball-point pens.
When the phosphate ester surfactant is used in the ink composition according to the present invention, the phosphate ester surfactant acts as an extreme pressure agent. In general, extreme pressure agents are substances that react easily with metal surfaces when the temperature rises due to frictional heat, form a soft solid film, and have the effect of increasing lubricity. It is added to obtain a feeling of writing. The phosphate group of the phosphate surfactant, which is a phosphate ester surfactant, is adsorbed on the metal surface, exerting extreme pressure action, so that a good writing feeling can be obtained even under high writing pressure.
That is, the lubricating effect of the phosphate ester surfactant is such that the phosphoric acid group adsorbs to the respective metal surfaces of the ball receiving seat and the ball of the chip, the hydrophobic group extends into the ink, and the physical contact between the ball and the ball seat is reduced. It is thought to be expressed by inhibiting direct contact. Therefore, it is believed that the cushioning action of the hydrophobic groups extending between the tip and the ball provides a desirable lubricating effect as a ball-point pen, that is, a smooth and soft writing feel.
The above phosphate ester-based surfactants can also be used after being properly neutralized with an alkaline substance such as amines or alkali metals.
On the other hand, in fountain pens and marking pens, there is no friction between the ball and the ball seat, so the ink composition used for fountain pens or marking pens may not require a phosphate surfactant.

In addition to the surfactants described above, those that can be used as lubricants include alkylbenzenesulfonic acids, amino acids, N-acylamino acids, aliphatic amide alkylene oxide adducts, terpenoid acid derivatives, and salts thereof. More specifically, oleic acid, stearic acid, linoleic acid, linolenic acid, ricinoleic acid, dodecylbenzenesulfonic acid, alanine, glycine, lysine, threonine, serine, proline, sarcosine, N-acylsarcosine, polyoxyethylene fatty acid amide and salts thereof.

When the ink composition according to the present invention is used in a fountain pen or a marking pen, an ink reversal material capable of maintaining moderate wettability to the inner wall of the ink tank is used in order to improve ink transfer due to reversal of the ink tank. be able to. Examples of ink reversal materials include polyetheramine, glycyrrhizic acid and/or its salts, oligomeric esters of polyglycerin and dicarboxylic acid, polyoxyethylene/polyoxypropylene alkyl ethers, polyoxyethylene/polyoxypropylene block polymers, and the like. The content is preferably 0.01 to 10% by mass based on the total mass of the ink composition.
In addition, the ink reversal material can maintain appropriate wettability not only for the ink tank but also for the ink flow control member. Therefore, it is possible to sufficiently obtain the function of the ink flow rate adjusting body, and it is possible to maintain good ink ejection performance from the pen tip. can smoothly flow in, so it is possible to suppress the dripping phenomenon of ink.

The ink composition according to the invention can contain a polysaccharide. Polysaccharides bring about various effects, but mainly bring about effects such as adjustment of ink viscosity, provision of shear thinning properties, and improvement of dry-up resistance performance, as will be described later. Specific examples include dextrin, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, diutan gum and the like.

When the ink composition contains a component such as a pigment that can exist in an insoluble state in water, which is the main solvent, the water evaporates at the nib of a writing instrument containing the ink, and the ink dries and solidifies to form an ink channel. etc. may be clogged. When such a phenomenon occurs, the ink jetting performance is affected, and although the writing instrument has ink remaining, it may become impossible to write again. Therefore, it is preferable to improve the dry-up resistance performance. Therefore, for example, it is necessary to consider improving the dry-up resistance of the tip of a ball-point pen. Dextrin has the effect of forming a film on the nib of the pen and preventing the solvent in the ink from evaporating. Therefore, the use of dextrin is effective because an ink composition having excellent dry-up resistance can be obtained.

The weight average molecular weight of dextrin is preferably from 5,000 to 120,000. When it is 120,000 or more, the film formed on the pen tip is hard, and the handwriting tends to be blurred when writing at the time of dry-up. On the other hand, if it is less than 5,000, it is difficult to change the viscosity enough to improve the dispersion stability over time. It is difficult to maintain, and it tends to be difficult to suppress the evaporation of the solvent in the ink. Considering the improvement of the above effects, it is preferable to use a dextrin having a mass average molecular weight of 20,000 to 100,000.

The content of dextrin is preferably 0.1 to 5% by mass based on the total mass of the ink composition. This is because if it is less than 0.1% by mass, the effect of improving dry-up resistance tends to be insufficient, and if it exceeds 5% by mass, it tends to be difficult to dissolve in the ink. Considering the dissolution stability in the ink, the content is preferably 0.1 to 3% by mass, and considering the improvement of dry-up resistance, 1 to 3% by mass is most preferable.

The ink composition according to the invention may contain two or more polysaccharides.

In particular, when the ink composition according to the present invention is used for a ballpoint pen, it is preferable to use a shear thinning agent to adjust the ink viscosity. Keeps the viscosity of the ink composition high when it is still, making it easier to maintain a uniform and good dispersion state. When writing, the ink composition is subjected to shearing force due to the rotation of the ball at the tip of the tip, reducing the viscosity of the ink composition. This is because it is possible to obtain good ink jettability and to obtain handwriting with good color development without bleeding. Ink compositions that require a relatively low viscosity, such as ink compositions used for fountain pens and marking pens, may not contain a shear thinning agent in some cases. By adopting such a configuration, it is possible to secure ink flow and improve writing performance.

Examples of shear-thinning agents include non-crosslinked acrylic acid polymers and crosslinked acrylic acid polymers in addition to the polysaccharides described above. The shear thinning agent may be used alone or in combination of two or more.

（式中、Ｒ^１１は、水素またはメチル基である）
で示される繰り返し単位と、
以下の式（ｉｉ）：

（式中、
Ｒ^１２は、水素またはメチル基であり、かつ
Ｒ^１３は、炭素数１～５の、直鎖または側鎖を有するアルキル基である）
で示される繰り返し単位と
を含んでなる非架橋型アクリル酸共重合体を用いることが好ましい。 As the non-crosslinked acrylic acid polymer, the following formula (i):

(wherein R ¹¹ is hydrogen or a methyl group)
A repeating unit indicated by
Formula (ii) below:

(In the formula,
R ¹² is hydrogen or a methyl group, and R ¹³ is a straight or branched alkyl group having 1 to 5 carbon atoms)
It is preferable to use a non-crosslinked acrylic acid copolymer containing a repeating unit represented by.

This non-crosslinked acrylic acid copolymer is a (meth)acrylic acid-(meth)acrylic acid ester copolymer. In the present invention, (meth)acryl means to include both acryl and methacryl. Specifically, acrylic acid-acrylic acid ester copolymer, methacrylic acid-acrylic acid ester copolymer, acrylic acid-methacrylic acid ester copolymer, methacrylic acid-methacrylic acid ester copolymer, acrylic acid-methacrylic acid - acrylic acid ester copolymer, acrylic acid-methacrylic acid-methacrylic acid ester copolymer, acrylic acid-acrylic acid ester-methacrylic acid ester copolymer, methacrylic acid-acrylic acid ester-methacrylic acid ester copolymer, acrylic acid-acrylic acid ester-methacrylic acid-methacrylic acid ester copolymer and the like. Random copolymers, block copolymers, and the like can be used as non-crosslinked acrylic acid copolymers. These non-crosslinked acrylic differential copolymers can be used alone or in combination of two or more.

In addition, R ¹³ of the non-crosslinked acrylic acid copolymer is an alkyl group having a straight chain or a side chain with 1 to 5 carbon atoms. Cohesive force between alkyl groups is reduced. In addition, when the number of carbon atoms is more than 5, the hydrophobicity of the alkyl group increases, so separation or precipitation tends to occur in some areas, which may result in non-uniformity. Therefore, the stability in the ink composition tends to be poor. When the number of carbon atoms is in the range of 1 to 5, the cohesive force between the alkyl groups acts strongly to physically bond to form an intermolecular network, which is preferable. Further, it is preferred that the alkyl group is linear, because steric hindrance is less than that of an alkyl group having a side chain. In particular, when R ¹³ is a methyl group having 1 carbon atom or an ethyl group having 2 carbon atoms, the hydrophobicity is not large, so that it is possible to design a relatively large amount of alkyl group to be introduced into the molecule. By increasing the amount of alkyl groups introduced, it becomes possible to arrange many physical bonding points between alkyl groups, and effects such as higher static viscosity and lower shear viscosity can be obtained. Especially preferred.

The number ratio of the repeating units of formula (i) to the number of repeating units of formula (ii) is 1:0.05 to 1:10, more preferably 1:0.1 to 1:5, and further Preferably, it is 1:0.3 to 1:3. If the ratio of the repeating units of the formula (ii) is too small, the physical bonding effect of the alkyl groups tends to be insufficient, and the thickening property and the viscosity gradient between standing and shearing tend to decrease. If it is too high, the hydrophobicity of the copolymer increases, which may result in partial separation or precipitation. Within this range, it is possible to achieve both a high static viscosity and a low shearing viscosity, which is particularly preferred.

The weight average molecular weight of the non-crosslinked acrylic acid copolymer is preferably 1,000 or more, more preferably 5,000 or more, and still more preferably 20,000 or more. If it is smaller than the above, it may become difficult to develop sufficient viscosity. Also, it is preferably 1,000,000 or less, more preferably 700,000 or less, and still more preferably 600,000 or less. If it is larger than the above, the viscosity at high shear may become too high. Here, the weight average molecular weight is a weight average molecular weight in terms of polystyrene, and can be measured by gel permeation chromatography using polystyrene as a standard.

The content of the non-crosslinked acrylic acid copolymer can be in the range of 0.01 to 10% by mass based on the total mass of the ink composition. It is preferably in the range of 0.05 to 5% by mass, more preferably in the range of 0.1 to 2% by mass. If it is larger than this range, the viscosity of the ink composition increases when standing, the dispersion stability of the ink composition improves, and the handwriting does not bleed, but the viscosity of the ink tends to increase slightly when sheared, and the writing performance slightly deteriorates. A downward trend can be seen. If it is less than this range, the viscosity of the ink during shearing will be low, and the handwriting will not be blurred or the line will be broken, but the handwriting will tend to blur. Within the above range, while maintaining the dispersion stability of the ink composition, there is no faintness or line cracking when writing, the handwriting does not blur, and excellent ink stability and writing performance can be obtained. ,preferable.

When the ink composition according to the present invention contains a non-crosslinked acrylic acid copolymer, it may further contain a crosslinking agent. The cross-linking agent used in the present invention is a compound capable of forming a reversible physical cross-link with the above-described non-cross-linking acrylic acid copolymer. It is a compound that can express intermolecular cohesive force by group and van der Waals. When the ink composition is in a static state, the cross-linking agent can form cross-linking points through physical bonding with the alkyl groups of the copolymer used in the present invention to form a strong network. It is a compound in which the physical bonds at the cross-linking points are easily broken when a shearing force is applied to the material.

Specific examples of cross-linking agents include alkyl-modified glucose, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, alkyl-modified polyethylene oxide, phenyl-modified polyethylene oxide, and phenylalkyl-modified polyethylene oxide. The effect can be obtained by using either a polymer compound containing an alkyl group or a low-molecular-weight compound as a cross-linking agent. It is preferable because the viscosity gradient at time can be increased. The alkyl group has 1 to 30 carbon atoms, preferably 1 to 22 carbon atoms, more preferably 1 to 18 carbon atoms. In particular, when the number of carbon atoms in the alkyl groups is the same, it is preferable to use a compound with less steric hindrance, because the effect will be greater.

By using a non-crosslinked acrylic acid copolymer, the shearing viscosity of the ink composition during writing is made lower than that of conventional crosslinked acrylic acid polymers, so the ink composition is composed of paper fibers, etc., more than before. It can be quickly penetrated into a writing object (for example, a paper support). When the ink composition further contains the above-described surfactant having an acetylene bond or a silicone surfactant, the penetration promoting effect exhibits a synergistic effect with the effect of the non-crosslinked acrylic acid copolymer, and the writing object It is thought that the permeability to the is further improved. As a result, the above-described components in the ink composition act to reduce the viscosity of the ink composition and improve the permeability, resulting in high handwriting drying properties.

When the ink composition according to the present invention is used for a ballpoint pen, the ink viscosity is preferably 500 to 5,000 mPa s at a shear rate of 1.92 sec ⁻¹ in an environment of 20° C., and the ink viscosity is within the above numerical range. Within this range, the ink has excellent fluidity and dispersion stability, has good ink jettability, and can obtain good handwriting free from fading and bleeding. In particular, in consideration of good ink jetting properties from the nib of the ink composition, the ink viscosity is more preferably 1,000 to 3,000 mPa·s.

Examples of pH adjusters include inorganic salts such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide and sodium acetate, organic basic compounds such as water-soluble amine compounds such as triethanolamine and diethanolamine, lactic acid and citric acid. is mentioned. The content of the pH adjuster is preferably 0.1 to 25% by mass, more preferably 5 to 20% by mass, relative to the ink composition.

Rust inhibitors include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, dialkylthiourea, and the like.

Preservatives include 2-methyl-4-isothiazolin-3-one (hereinafter sometimes referred to as MIT), 2-n-octyl-4-isothiazolin-3-one (hereinafter sometimes referred to as OIT), 1 , 2-benzisothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, 2-pyridinethiol -1-oxide sodium, 3-iodo-2-propynylbutylcarbamate sodium benzoate, benzotriazole and phenol. The content of these preservatives is preferably 20 to 200 ppm based on the total weight of the ink composition. Moreover, it is preferable to use MIT and OIT in combination among these because the antibacterial properties are improved. In this case, the content of OIT is preferably 1 to 50 ppm based on the total mass of the ink composition, and the blending ratio of OIT and MIT is preferably 1:1 to 10:1 based on mass. preferable.

In addition, the ink composition according to the present invention may contain a water-soluble resin such as an acrylic resin, an alkyd resin, a cellulose derivative, polyvinylpyrrolidone, or polyvinyl alcohol for the purpose of improving the scratch resistance of handwriting. can. Further, the resin emulsion may include an emulsion containing an acrylic resin, a urethane resin, a styrene-butadiene resin, a polyester resin, a vinyl acetate resin, or the like.

The ink composition according to the present invention can contain organic resin particles for the purpose of suppressing ink sagging. Organic resin particles that can be used in the present invention include olefin resin particles such as polyethylene resin and polypropylene resin, melamine/formaldehyde resin, benzoguanamine/formaldehyde resin, benzoguanamine/melamine/formaldehyde resin, urea formaldehyde resin, nylon resin, and the like. Nitrogen-containing resin particles containing a nitrogen atom in the chemical structure of, acrylic resin particles, styrene resin particles, epoxy resin particles, urethane resin particles, cellulose resin particles, and the like. These organic resin particles may be used alone or in combination of two or more.

Among organic resin particles, olefin resin particles and nitrogen-containing resin particles are preferably used. This is because the olefin-based resin particles are hydrocarbon compounds and are non-polar, so they tend to aggregate in water. It is presumed that this is because it is easy to form an optimized aggregation structure that prevents problems such as insufficient ink discharge while suppressing ink leakage. In addition, since olefin resin particles have a high melting temperature, they tend to exist stably even in high-temperature environments. It can be suitably used as an ink additive.

Materials for the olefinic resin particles include polyolefins such as polyethylene, polypropylene, polybutene, and mixtures thereof. Among these, it is preferable to use polyethylene in view of suppressing ink leakage and improving writing comfort. Specific examples include low-density polyethylene, high-density polyethylene, low-molecular-weight polyethylene, modified polyethylene, and modified high-density polyethylene. etc. Among them, low-density polyethylene, low-molecular-weight polyethylene, and modified polyethylene are preferable considering the effect of suppressing ink leakage. In particular, low-density polyethylene has a lower melting point than other types of polyethylene and is soft, so polyethylene particles adhere closely. Low-density polyethylene is preferable because it is easy to wash, does not easily cause gaps between particles, and does not easily leak ink. Low-density polyethylene is soft and can be used preferably because it improves writing comfort. The olefin-based resin particles may contain materials other than polyolefin as needed.

Among the nitrogen-containing resin particles, it is preferable to have an amino group or an imino group. This is because the presence of an amino group or an imino group facilitates the formation of a stable aggregation structure for a long period of time and facilitates the suppression of ink leakage. The nitrogen-containing resin particles having functional groups such as amino groups and imino groups also include tertiary amines and quaternary amines.
Furthermore, among the nitrogen resin particles having amino groups or imino groups, it is preferable to use nitrogen-containing resin particles having a chemically bonded three-dimensional crosslinked structure. This is because when it has a chemically bonded three-dimensional crosslinked structure, it is particularly excellent in strength, heat resistance, solvent resistance, etc., and is stable without moisture absorption in water-based ink, so it is excellent in stability over time. Therefore, it is preferable. Furthermore, due to the stability of the nitrogen-containing resin particles themselves and mutual hydrogen bonding between the nitrogen-containing resin particles, it is easy to form an aggregated structure for a long period of time, and it is easy to stably suppress ink leakage. In particular, among the nitrogen-containing resin particles having a crosslinked structure, resin particles having a heterocyclic structure such as melamine/formaldehyde resin, benzoguanamine/formaldehyde resin, and benzoguanamine/melamine/formaldehyde resin are less likely to absorb moisture and are stable. preferable.
Specific examples of the nitrogen-containing resin particles having a crosslinked structure include amino resin particles such as melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin, and urea-formaldehyde resin. Examples of nitrogen-containing resin particles having an amide bond include nylon resins such as nylon 6 and nylon 12, and urethane resin particles such as polycarbonate polyurethane resins, polyether polyurethane resins, polyester polyurethane resins, and urethane urea resins. be done.

As for the shape of the organic resin particles, spherical or irregularly shaped particles can be used, but spherical resin particles are preferable in consideration of reducing the frictional resistance. The spherical resin particles referred to here are not limited to true spheres, and may be substantially spherical resin particles or substantially ellipsoidal resin particles.

Further, the content of the organic resin particles is more preferably 0.01 to 10.0% by mass based on the total mass of the ink composition. This is because if the content of the organic resin particles is less than 0.01% by mass, it is difficult to suppress ink leakage, and if it exceeds 10.0% by mass, the aggregation structure tends to become strong, which affects writing quality and dry-up performance. This is because it is easy for Furthermore, taking into consideration, 0.02 to 5.0% by mass is preferable, 0.03 to 1.0% by mass is particularly preferable, and 0.05 to 0.5% by mass is most preferable.

The viscosity gradient of the ink composition according to the invention can be expressed by the viscosity index n at 20°C. Here, the viscosity index n refers to n in the viscosity formula represented by S=αDn. S is shear stress (dyn/cm ² =0.1 Pa), D is shear rate (s ⁻¹ ), and α is viscosity coefficient. The viscosity index n can be calculated by measuring the ink viscosity using an E-type rotational viscometer (DV-II+Pro, cone rotor CPE-42, manufactured by Brookfield).

<Writing implements>
The aqueous ink composition for writing instruments according to the present invention can be accommodated in various writing instruments. Such a writing instrument can form a handwriting on the surface by writing on a writing object such as a paper support, wood, or a cloth made of a hydrophilic organic material. The structure and shape of the writing instrument to be filled with the water-based ink composition for writing instrument according to the present invention are not particularly limited. It can be used for various writing instruments such as a marking pen, a ballpoint pen, and a fountain pen using a metal nib.

The writing instrument to which the ink composition according to the present invention can be applied may be of a construction in which the ink composition is directly filled, or may be an ink containing body or an ink storage body capable of being filled with the ink composition. It may have a body. Also, the ink cartridge type writing instrument may have a structure in which the ink container or the ink absorbing body can be detachably replaced with the writing instrument main body.

The writing instruments to which the ink composition according to the present invention can be applied include cap-type writing instruments equipped with a cap that covers the pen tip, and knock-type, rotary-type, and slide-type writing instruments that can accommodate the pen tip in the barrel. type writing instruments ballpoint pens.

The supply mechanism of the writing instrument to which the ink composition according to the present invention can be applied is not particularly limited. Mechanism for supplying the composition to the pen tip, (Mechanism 2) Mechanism for supplying the ink composition to the pen tip with a comb groove-shaped ink flow control member interposed therebetween, (Mechanism 3) Ink flow rate by the valve mechanism A mechanism for supplying the ink composition to the pen tip with an adjusting member, and (Mechanism 4) a mechanism for directly supplying the ink composition to the pen tip without an ink flow rate adjusting member.
In particular, in the case of providing an ink guiding core made of a fiber bundle like the mechanism 1 using capillary action, or in the case of providing a comb groove-like ink flow control member like the mechanism 2, the capillary force is effectively applied. Therefore, a low-viscosity ink composition is used, and the amount of ink ejected during writing tends to increase. For this reason, it takes time to dry the handwriting completely. Therefore, it is preferable that the ink composition according to the present invention has an excellent handwriting drying property. When it has, it is preferably used.

When the specifications of a ball-point pen filled with the water-based ink composition for writing instruments according to the present invention were examined, the amount of ink consumed per 100 m of the water-based ball-point pen was A (mg), and the diameter of the ball was B (mm). , 150≦A/B≦500, and preferably 250≦A/B≦450. This is because, by setting the amount in the above range, by making the ink consumption appropriate for the ball diameter, the ink fluidity is improved, and by suppressing blurring of handwriting, etc., it is easy to obtain good handwriting. is.

Regarding the ink consumption, 5 test samples were measured under the conditions of 20 ° C., a writing angle of 65 ° on writing paper JIS P3201 writing paper, a writing load of 100 g, and a writing speed of 4 m / min. A writing test is performed, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m. Also, the diameter of the ball is not particularly limited, but a ball having a diameter of about 0.1 to 2.0 (mm) is generally used.

Regarding the specifications of the ball-point pen tip, the amount of movement (clearance) of the ball in the ball-point pen tip in the longitudinal direction is preferably 20 to 50 μm, preferably 30 to 45 μm, when the ball-point pen is manufactured or used. is preferred. This is because within the above range, it is easy to obtain good handwriting by appropriately adjusting the ink discharge amount and suppressing line skipping and blurring. The ratio A/B is also easy to adjust.
The movable amount (clearance) of the ball of the ball-point pen tip in the vertical axis direction indicates the distance that the ball can move in the vertical axis direction of the ball-point pen tip body. Here, the movable amount generally increases with use because the ball and ball seat wear with use. The movable amount is related to the ink discharge amount. Therefore, in general, the movable amount at the time of manufacture or at the start of use of the ball-point pen is set within the above range. Preferably.
When a ball-point pen tip with a large clearance is used, the amount of ink ejected increases and the density of handwriting can be increased. Therefore, the ink composition according to the present invention is suitably used even when a ball-point pen tip with a large clearance is used. In addition, when the ink discharge amount is large, it is preferable to contain the above-described organic resin particles to prevent sagging.
When combining such a ballpoint pen with the ink composition according to the present invention,
water and,
a coloring agent;
an amide compound represented by formula (1) having a content of 1 to 35 masses based on the total mass of the ink composition; and a lubricant such as a phosphate surfactant;
It is preferred to use an ink composition comprising

When the water-based ink composition for writing instruments according to the present invention is combined with a marking pen, the pen tip is not particularly limited, and may be, for example, a fiber tip, a felt tip, or a plastic tip. It may be a mold, a chisel type or a brush pen type or the like.
When combining such a marking pen with the water-based ink composition according to the present invention,
water and,
a coloring agent;
It is preferable to use an ink composition containing an amide compound represented by formula (1) in an amount of 1 to 35 mass based on the total mass of the ink composition.

Furthermore, when the water-based ink composition for writing instruments according to the present invention is combined with a fountain pen, a nib made of metal or ceramic, a shaft having a comb groove mechanism, or the like can be employed. Furthermore, the ink composition according to the present invention can be applied to a fountain pen that can write by filling a replaceable cartridge or the like and loading it. When the water-based ink composition according to the present invention is combined with such a fountain pen, based on the total weight of the ink composition,
water and,
a coloring agent;
an amide compound represented by formula (1) having a content of 1 to 35 mass based on the total mass of the ink composition; and an ink reversible material;
It is preferred to use an ink composition comprising

<Method for producing ink composition>
The ink composition according to the present invention can be produced by any conventionally known method. Specifically, the required amount of each component is blended and mixed with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, and various dispersers such as a bead mill.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
An ink composition was obtained by the formulation composition and method described below.
Water: ion-exchanged water 77.8% by mass
Coloring agent: carbon black 8.0% by mass
Amide compound: 3-methoxy-N,N-dimethylpropanamide 10.0% by mass
pH adjuster: triethanolamine 1.0% by mass
Antirust agent: 0.5% by mass of benzotriazole
Preservative: 1,2-benzisothiazolin-3-one 0.2% by mass
Phosphate ester surfactant: Plysurf A215C (manufactured by Daiichi Kogyo Co., Ltd.) 1.0% by mass
Polysaccharide: dextrin (mass average molecular weight 30,000, Sundec series, Sanwa Starch Industry Co., Ltd.) 1.5% by mass

Water, a coloring agent, a pH adjuster, an antirust agent, an antiseptic agent, a phosphate surfactant, and dextrin were heated and stirred with a disper to prepare a base ink. After that, while heating the base ink, it was sufficiently mixed and stirred using a homogenizer stirrer until it was in a uniform state, and filtered using filter paper to obtain an ink composition of Example 1.

<Example 2, Comparative Example 1>
With respect to the composition of Example 1, 0.5% by mass of Surfynol 2502 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, was added, and water was changed to 77.3% by mass. , and the ink composition of Example 2 was prepared in the same manner.
An ink composition of Comparative Example 1 was prepared in the same manner as in Example 1, except that the content of the amide compound was changed to 0 and the content of water was changed to 87.8% by mass.

The ink compositions (1.0 g) of Examples 1 and 2 and Comparative Example 1 were applied to a ball-point pen tip in which a cemented carbide ball with a diameter of 0.7 mm was rotatably held (the amount of movement in the vertical axis direction of the ball (clearance ) 30 μm) at the tip was filled inside an ink container, and this refill was attached to a gel ink ballpoint pen (trade name: G-2) manufactured by Pilot Corporation to obtain a ballpoint pen. The ball-point pen thus obtained was used as a ball-point pen for testing, and the following handwriting dryness evaluation was performed.

The test ballpoint pen was used to handwrite the word "ei" on commercial report paper at room temperature, and after 0, 3, 5, 10 and 30 seconds respectively, the writing was rubbed in one direction with the thumb. The state of the handwriting at that time was visually confirmed, and the results obtained are shown in Table 1. Evaluation criteria are as follows.
A: Good handwriting was left without staining the surroundings.
B: Slight staining occurred, but good handwriting was left.
C: Some stains occurred, but good handwriting was left.
D: Smudges occurred on the entire handwriting.
E: Significant staining occurred over the entire handwriting.

Each of the ink compositions of Examples 1 and 2 and Comparative Example 1 was sampled on a slide glass and observed using an optical microscope to evaluate ink stability (speculum). In addition, the appearance of each ink composition was visually observed to evaluate ink stability (appearance). The results obtained are shown in Table 1. Evaluation criteria are as follows.
Ink stability A: No aggregates were observed, and the ink was uniformly dispersed.
B: Aggregates were slightly observed, but were in a good dispersed state.
C: Aggregates were observed, but at a practically non-problematic level.
D: Aggregates were observed, and the level was of concern for practical use.
Ink stability (appearance)
A: Good ink fluidity was obtained.
B: Viscosity of ink was confirmed, but fluidity was maintained.
C: It was confirmed that the fluidity tends to be poor due to gelling of the ink.

In Example 2, the acetylene glycol-based surfactant Surfynol 2502 is replaced with, for example, an acetylene glycol-based surfactant Dynol 604 (manufactured by Nissin Chemical Industry Co., Ltd.) or a silicone surfactant BYK345 (Bik Chemie Co., Ltd.), the effect of the present invention can be obtained.

インキ安定性（外観）の評価において、比較例１－ｈのインキ組成物では、増粘する様子が確認され、比較例１－ｉのインキ組成物は、析出物が発生する様子が確認された。 <Examples 1-a to 1-g and Comparative Examples 1-h and 1-i>
Examples 1-a to 1-g and Comparative Example 1 were prepared in the same manner as in Example 1 except that the amount of amide compound shown in Table 2 was included instead of 10% by mass of the amide compound. -h and 1-i ink compositions were prepared.
These ink compositions were evaluated for writing dryness and ink stability in the same manner as described above. The results obtained are shown in Table 2.

In the evaluation of the ink stability (appearance), it was confirmed that the ink composition of Comparative Example 1-h increased in viscosity, and that the ink composition of Comparative Example 1-i generated precipitates. .

All of these examples were evaluated in combination with a ballpoint pen for comparison. It can also be suitably used for pens. When used for a fountain pen, the effect of the present invention can be obtained even if the shear thinning agent such as polysaccharide is not included.

In particular, when the ink composition according to the present invention is used in a fountain pen, polyoxyethylene, which is an ink reversible material, does not contain a phosphate ester-based surfactant and a polysaccharide, as opposed to the ink composition of Example 1. - An ink composition containing 0.1% by mass of a polyoxypropylene block polymer and containing 80.2% by mass of water can be used, and this ink composition can obtain the effects of the present invention. .

<Examples 3, 4, and Comparative Example 2>
For the composition of Example 1, (meth) acrylic acid - methyl (meth) acrylate copolymer (molar ratio of carboxylic acid and methyl ester 1: 2.1, repeating units derived from acrylic acid and repeating units derived from methacrylic acid An ink composition of Example 3 was prepared in the same manner, except that 0.21% by mass of repeating unit molar ratio (1:0.36) was added and water was changed to 77.59% by mass.
With respect to the composition of Example 3, 0.5% by mass of Surfynol 2502 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, was added, and water was changed to 77.09% by mass. , and the ink composition of Example 4 was prepared in the same manner.
An ink composition of Comparative Example 2 was prepared in the same manner as in Example 3, except that the amide compound was 0 and the water was 87.59% by mass.

The ink compositions of Examples 3 and 4 and Comparative Example 2 were evaluated for handwriting drying and ink stability in the same manner as described above. The results obtained are shown in Table 3.

<Examples 4-a to 4-c>
Inks of Examples 4-a to 4-c were prepared in the same manner as in the composition of Example 4, except that the amide compound and diethylene glycol in the amounts shown in Table 2 were included instead of 10% by mass of the amide compound. A composition was prepared.
These ink compositions were evaluated for writing dryness and ink stability in the same manner as described above. The results obtained are shown in Table 4.

The ink compositions of Examples 3, 3-a to 3-c and 4 are particularly suitable for ballpoint pens.

<Examples 5, 6, and Comparative Example 3>
An ink composition of Example 5 was prepared in the same manner as in Example 1, except that 0.33% by mass of xanthan gum (manufactured by Sansho Co., Ltd.) was added and water was changed to 77.47% by mass. prepared.
With respect to the composition of Example 5, 0.5% by mass of Surfynol 2502 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, was added, and water was changed to 76.97% by mass. , and the ink composition of Example 6 was prepared in the same manner.
An ink composition of Comparative Example 3 was prepared in the same manner as in Example 5, except that the amide compound was 0 and the water was 87.47% by mass.

The ink compositions of Examples 5 and 6 and Comparative Example 3 were evaluated for handwriting drying and ink stability in the same manner as described above. The results obtained are shown in Table 5.

The ink compositions of Examples 5 and 6 are particularly suitable for use in ballpoint pens.

<Examples 7, 8, and Comparative Example 4>
An ink composition of Example 7 was prepared in the same manner as in Example 1, except that 0.15% by mass of succinoglycan (manufactured by Sansho Co., Ltd.) was added and water was changed to 77.65% by mass. prepared the product.
With respect to the composition of Example 7, 0.5% by mass of Surfynol 2502 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, was added, and water was changed to 77.15% by mass. Similarly, an ink composition of Example 8 was prepared.
An ink composition of Comparative Example 4 was prepared in the same manner as the composition of Example 7 except that the amide compound was 0 and the water was 87.65% by mass.

The ink compositions of Examples 7 and 8 and Comparative Example 4 were evaluated for handwriting drying and ink stability in the same manner as described above. The results obtained are shown in Table 6.

The ink compositions of Examples 7 and 8 are particularly suitable for use in ballpoint pens.

<Example 9>
With respect to the composition of Example 1, except that 10% by mass of 3-butoxy-N,N-dimethylpropanamide was included instead of 10% by mass of 3-methoxy-N,N-dimethylpropanamide as the amide compound. Similarly, an ink composition of Example 9 was prepared.
The obtained ink composition was evaluated for the drying property of handwriting in the same manner as described above, and it was confirmed that the effect of the present invention was obtained. Ink stability evaluation results of Example 1 were better.

Claims (9)

water and,
a coloring agent;
an amide compound represented by formula (1);

(In the formula,
R ¹ is a straight or branched alkyl group having 1 to 6 carbon atoms, and R ² and R ³ are each independently hydrogen or a straight or branched chain having 1 to 4 carbon atoms, is an alkyl group) ,
Phosphate ester surfactant and
A water-based ink composition for writing instruments comprising
A water-based ink composition for writing instruments, wherein the content of the amide compound is 1 to 35% by mass based on the total mass of the composition. water and,
a coloring agent;
an amide compound represented by formula (1);

(In the formula,
R. ¹ is a linear or branched alkyl group having 1 to 6 carbon atoms, and
R. ² and R ³ are each independently hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms),
with polysaccharides
A water-based ink composition for writing instruments comprising
A water-based ink composition for writing instruments, wherein the content of the amide compound is 1 to 35% by mass based on the total mass of the composition. water and,
a coloring agent;
an amide compound represented by formula (1);

(In the formula,
R. ¹ is a linear or branched alkyl group having 1 to 6 carbon atoms, and
R. ² and R ³ are each independently hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms),
Formula (i) below:

(In the formula, R ¹¹ is a hydrogen or methyl group)
A repeating unit indicated by
Formula (ii) below:

(In the formula,
R. ¹² is a hydrogen or methyl group, and
R. ¹³ is an alkyl group having a linear or side chain having 1 to 5 carbon atoms) and a repeating unit represented by
a copolymer comprising
A water-based ink composition for writing instruments comprising
A water-based ink composition for writing instruments, wherein the content of the amide compound is 1 to 35% by mass based on the total mass of the composition. The composition according to any one of claims 1 to 3, wherein R ¹ is a straight-chain alkyl group having 1 to 4 carbon atoms, and both R ² and R ³ are methyl groups. The composition according to any one of claims 1 to 4 , further comprising a surfactant having an acetylene bond in its structure or a silicone surfactant. 3. The composition of claim 2 , wherein said polysaccharide is dextrin. The composition according to any one of claims 1 to 6, which is an ink composition for fountain pens or marking pens. The composition according to any one of claims 1 to 6 , which is an ink composition for water-based ballpoint pens. A writing utensil containing the composition according to any one of claims 1 to 8 .