JP2019189802A - Colored resin particle dispersion and method for producing the same, and aqueous ink composition for writing instrument containing colored resin particle dispersion, and writing instrument - Google Patents

Abstract

To provide a colored resin particle dispersion having excellent dispersion stability, and an aqueous ink composition for writing instruments that has excellent dispersion stability and ensures excellent handwriting, and a method for producing the same.SOLUTION: The present invention provides a colored resin particle dispersion containing a styrene-acrylonitrile resin particle, a colorant, a specific dispersant, and water, and an aqueous ink composition for writing instruments containing the same. The ink composition can be used for writing instruments. A dispersion thereof is produced by adding a colorant, a colorant aqueous solution, or a colorant aqueous dispersion to a mixture of a styrene-acrylonitrile resin particle or styrene-acrylonitrile resin particle dispersion, a specific dispersant, and water, and subjecting it to dispersion treatment.SELECTED DRAWING: None

Description

  The present invention relates to a colored resin particle dispersion, a water-based ink composition for a writing instrument comprising the same, and a writing instrument using the same.

  In recent years, high water resistance and light resistance have been desired for water-based ink compositions for writing instruments, and ink compositions using pigments have been proposed in order to improve these properties.

  However, since the pigment is insoluble in water, which is the main solvent of the ink composition, unless it is uniformly dispersed and stabilized, aggregation and sedimentation are likely to occur and the color developability of the ink composition may be reduced. In some cases, sufficient performance as a water-based ink composition for a writing instrument cannot be obtained, for example, the amount of ink discharged from the nib is reduced to cause line skipping or fading, or writing becomes impossible.

  Accordingly, many ink compositions have been proposed in which various dispersants are added to the ink composition in order to improve the dispersibility of the pigment.

  For example, Patent Document 1 discloses an ink composition containing, as a dispersant, a polymer compound obtained by copolymerizing N-vinylpyrrolidone or a derivative thereof and an alkene compound, and Patent Document 2 includes a carboxyl group-containing compound. There has been proposed an ink composition comprising an alkali salt of as a dispersant.

  However, although these dispersants exhibit a dispersibility improving effect, they may not be sufficient. As a result, if the amount of the dispersant added is small, line skipping and blurring may not be sufficiently solved. If a large amount of the dispersant is added for the purpose of obtaining a good dispersion effect, the viscosity of the ink composition becomes excessive. In some cases, the writing quality is poor, and the components of the ink composition may aggregate and separate after storage over time. For this reason, there is room for further improvement when these dispersants are used.

  In recent years, color variations have been desired for ink compositions so that various colors can be expressed. In order to meet such needs, it is necessary to prepare different types of pigments, and furthermore, it takes a lot of labor to adjust the dispersion stability of each pigment. Therefore, in order to reduce such a load, an ink composition using colored resin particles obtained by coloring resin particles with a pigment or a dye has been proposed. In such an ink composition, colored resin particles are used instead of the pigment. Since the colored resin particles are colored with a colorant with respect to the resin particles, the specific gravity is smaller than that of a conventionally used pigment, and the type of the resin particles should be the same when selecting the dispersant. For example, since the same dispersant can be used, there is an advantage that the selection of the dispersant can be facilitated. However, according to the study by the present inventors, such colored resin particles are difficult to be uniformly colored in a desired color, in which the resin particles agglomerate at the time of coloring, and the ink composition When used in the ink composition, although it showed good dispersion stability at the time of preparation of the ink composition, problems such as aggregation and sedimentation occurred after lapse of time, and there was room for improvement.

  Moreover, the ink composition using the colored resin particles as a colorant generally has a high solid content. As a result, the ink fluidity is lowered, and handwriting fading may occur. For this reason, it has been desired to improve ink flowability in addition to dispersibility.

JP-A-8-176488 JP 2004-018675 A

  The present invention provides a colored resin particle dispersion excellent in dispersion stability and a method for producing the same. In addition, the present invention provides a water-based ink composition for a writing instrument that is excellent in dispersion stability and provides a good handwriting, and further provides a writing instrument using the same.

（式中、
ｘは、１〜５の整数であり、
Ｃ_２Ｈ_４Ｏはエチレンオキシド基、Ｃ_３Ｈ_６Ｏはプロピレンオキシド基であり、
ここで、前記エチレンオキシド基および前記プロピレンオキシド基は、それぞれブロックを形成していても、ランダムに配列されていてもよく、
ｙおよびｚは、それぞれ、エチレンオキシド付加モル数およびプロピレンオキシド付加モル数であり、ｙ≧１かつｚ≧０である）
水と、
を含んでなることを特徴とするものである。 The colored resin particle dispersion according to the present invention is:
Styrene-acrylonitrile resin particles;
A colorant;
A dispersant having a group R ¹ of the formula (1),

(Where
x is an integer of 1 to 5,
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged,
y and z are the number of moles of ethylene oxide added and the number of moles of propylene oxide added, respectively, y ≧ 1 and z ≧ 0)
water and,
It is characterized by comprising.

  A water-based ink composition for a writing instrument according to the present invention is characterized by comprising the above colored resin particle dispersion.

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

（式中、
ｘは、１〜５の整数であり、
Ｃ_２Ｈ_４Ｏはエチレンオキシド基、Ｃ_３Ｈ_６Ｏはプロピレンオキシド基であり、
ここで、前記エチレンオキシド基および前記プロピレンオキシド基は、それぞれブロックを形成していても、ランダムに配列されていてもよく、
ｙおよびｚは、それぞれ、エチレンオキシド付加モル数およびプロピレンオキシド付加モル数であり、ｙ≧１かつｚ≧０である）
水と、
を含んでなる混合液中に、
着色剤、着色剤水溶液、または着色剤水性分散液を
添加し、分散処理することを含んでなることを特徴とするものである。 Furthermore, the method for producing a colored resin particle dispersion according to the present invention includes:
Styrene-acrylonitrile resin particles or styrene-acrylonitrile resin particle dispersion,
A dispersant having a group R ¹ of formula (1);

(Where
x is an integer of 1 to 5,
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged,
y and z are the number of moles of ethylene oxide added and the number of moles of propylene oxide added, respectively, y ≧ 1 and z ≧ 0)
water and,
In a mixture comprising
It is characterized by comprising adding a colorant, an aqueous colorant solution, or an aqueous colorant dispersion and dispersing it.

  Moreover, the manufacturing method of the ink composition by this invention is characterized by including the manufacturing method of the said colored resin particle dispersion.

  According to the present invention, a colored resin particle dispersion having excellent dispersion stability can be provided. According to the present invention, a water-based ink composition for a writing instrument that has excellent writing performance, such as excellent dispersion stability, good ink fluidity and color developability, and good writing with improved line skipping and blurring of handwriting and the like. A writing instrument using the same can be provided. Furthermore, the water-based ink composition for writing instruments according to the present invention is excellent not only in the dispersion stability immediately after preparation but also in the dispersion stability after aging, and has less blur after storage for a long time. And when such an ink composition is accommodated in a transparent ink container, since the color of the ink composition is visually recognized from the ink container, the quality is excellent. Moreover, the writing implement group provided with various color variations is realizable using the colored resin particle which gave various coloring.

  Hereinafter, embodiments of the present invention will be described in detail. In the present specification, “part”, “%”, “ratio” and the like indicating the composition are based on mass unless otherwise specified, and the content is a constituent component based on the mass of the ink composition. % By mass.

<Colored resin particle dispersion>
The colored resin particle dispersion (hereinafter sometimes referred to as dispersion) according to the present invention comprises styrene-acrylonitrile resin particles, a colorant, a specific dispersant, and water.
Here, in the present invention, the dispersion refers to a dispersion in which resin particles are dispersed in a liquid dispersion medium. The use of the dispersion is not particularly limited, but the dispersion according to the present invention is preferably used in a water-based ink composition for writing instruments (hereinafter sometimes referred to as an ink composition). In some cases, the dispersion itself can be used as a water-based ink composition.

  Below, the component used for the dispersion by this invention is demonstrated.

Styrene-acrylonitrile resin particles Styrene-acrylonitrile resin particles are excellent in alkali resistance, acid resistance, and heat resistance, so they are likely to exist stably in dispersions containing various components such as additives, and in a thermal environment. Therefore, a dispersion excellent in stability over time can be suitably obtained. Further, when the styrene-acrylonitrile resin particles are used together with a colorant, the color of the dispersion can be adjusted in various colors and with good color development. Therefore, by using styrene-acrylonitrile resin particles, a dispersion excellent in color developability and stability over time can be obtained.
In addition, when it mix | blends with a dispersion and the ink composition containing the styrene-acrylonitrile resin particle alone without using a coloring agent, it also has an effect which brings about whiteness, and can be used as a coloring aid.

  Styrene-acrylonitrile resin particles are resin particles obtained by copolymerizing styrene and acrylonitrile as monomers. The blending ratio of styrene and acrylonitrile is not particularly limited, but is generally blended at a ratio of 10 to 90 mol% styrene and 90 to 10 mol% acrylonitrile. In addition, monomers other than styrene and acrylonitrile can be combined as long as the effects of the present invention are not impaired.

The styrene-acrylonitrile resin particles used in the present invention preferably do not have a polar group, and particularly preferably do not have a polar group on the surface.
Specifically, among the repeating units of the molecules constituting the resin of the styrene-acrylonitrile resin particles in the present invention, the proportion of repeating units having a polar group is 30 mol% or less, preferably 20 mol% or less, more preferably 10 It is preferably not more than mol%, more preferably not more than 1 mol%, and more preferably zero.
If the ratio of the repeating unit having a polar group among the repeating units of the molecules constituting the resin of the styrene-acrylonitrile resin particle is in the above range, the polar group that can exist on the surface of the styrene-acrylonitrile resin particle. The dispersion effect of the dispersant described later can be effectively obtained without being hindered by the polar group present on the surface of the styrene-acrylonitrile resin particles. This is because a dispersion having high dispersion stability can be obtained.
In the present invention, the polar group refers to an ionic group such as a sulfonic acid group, a carboxylic acid group, or a phosphoric acid group. On the other hand, in the present invention, a nonionic group (for example, an alkyl group, an aryl group, an alkoxy group, a cyano group, etc.) is not included in the polar group. Furthermore, in the present invention, a ratio of zero means that the ratio cannot be detected by various measuring devices and is below the detection limit.

  As will be described later, the dispersant used in the present invention has a plurality of aromatic rings in one molecule. These styrene-acrylonitrile resin particles also have an aromatic ring, and a strong interaction occurs with the dispersant used in the present invention, which is considered to contribute to better dispersion stability of the dispersion. .

  The styrene-acrylonitrile resin particles in the present invention can be obtained by any conventionally known method. However, in consideration of the color developability of the dispersion, the dispersion stability, and the ink ejection from the pen tip when used in a writing instrument. The resin particles obtained by emulsion polymerization of styrene and acrylonitrile, in which uniform particles can be easily obtained, are preferred, and further, a styrene-acrylonitrile resin particle dispersion in a state of being previously dispersed in a dispersion medium such as water is used. It is preferable to use it. Commercially available products can be used as the styrene-acrylonitrile resin particle dispersion.

  The size of the styrene-acrylonitrile resin particles is not particularly limited, but in order to maintain dispersibility and prevent line skipping and blurring when used for writing instruments, it is preferable that the particle diameter is small, and high color developability. In order to obtain, it is preferable that an average particle diameter is large. From such a viewpoint, the volume-based average particle diameter is preferably 0.05 to 10 μm.

  The content of styrene-acrylonitrile resin particles in the dispersion of the present invention is preferably 20 to 60% by mass and more preferably 30 to 50% by mass based on the total mass of the dispersion. When the content of the styrene-acrylonitrile resin particles is within the above numerical range, when the dispersion is used in the ink composition, good color developability and at the same time good stability with time can be brought about.

Colorant The colorant adjusts the color of the dispersion together with the styrene-acrylonitrile resin particles. This colorant contributes to the color independently in the dispersion, develops a color adjusted by combination with styrene-acrylonitrile resin particles, or adsorbs or penetrates into the styrene-acrylonitrile resin particles in the dispersion. In some cases, colored particles are formed.
The colorant used in the present invention is preferably used for coloring styrene-acrylonitrile resin particles. Specifically, it is preferable that the styrene-acrylonitrile resin particles are adsorbed or permeated into the colorant. When using in such a state, the effect which water resistance improves can be anticipated compared with the case where a coloring agent and a styrene- acrylonitrile resin particle are used separately, respectively. Moreover, it is because the dispersion effect of a dispersing agent can be obtained efficiently and the dispersion excellent in dispersion stability can be obtained.

  As such a coloring agent, arbitrary dyes or pigments are used, and are not particularly limited.

  The dye is not particularly limited, and examples thereof include acid dyes, basic dyes, direct dyes, disperse dyes, oil-soluble dyes, reactive dyes, metal-containing dyes, food dyes, and various salt-forming dyes. Can be mentioned.

  The pigment is not particularly limited, and examples thereof include inorganic, organic, and processed pigments. Specifically, carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine pigments Azo pigments, quinacridone pigments, quinophthalone pigments, selenium pigments, triphenylmethane pigments, perinone pigments, perylene pigments, dioxazine pigments, aluminum pigments, pearl pigments, microcapsule pigments, etc. It is done. The pigment may be a water-dispersed pigment product or the like dispersed in a medium in advance using a pigment dispersant.

  Specific examples of the dye include 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 Baolet 15, C.I. I. Acid Violet 49, C.I. I. Acid Black 1, C.I. I. Acid dyes such as Acid Black 2, C.I. I. Basic Red 1: 1, C.I. I. Basic Yellow 28, C.I. I. Bay Yellow 40, C.I. I. Basic Orange 2, C.I. I. Basic Orange 14, C.I. I. Basic Green 4, C.I. I. Basic Blue 7, C.I. I. Basic Blue 9, C.I. I. Basic Blue 26, C.I. I. Basic Violet 15, C.I. I. Basic violet 11: 1, C.I. I. Basic Violet 1, C.I. I. Basic Violet 3, C.I. I. Basic dyes such as basic violet 10, 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 dyes such as direct black 19, C.I. I. Disperse Yellow 82, C.I. I. Disperse Yellow 3, C.I. I. Disperse Yellow 54, C.I. I. Disper thread 191, C.I. I. Disperse thread 60, C.I. I. Disperse dyes such as disperse violet 57, C.I. I. Food Yellow 3, C.I. I. Food dyes such as Food Black 2 are listed.

  Furthermore, as will be described later, the dispersant used in the present invention effectively works even when the styrene-acrylonitrile resin particles are colored with the colorant, suppresses aggregation of the styrene-acrylonitrile resin particles, and is uniform. Although it has an effect of further coloring and improving the dispersion stability and color developability of the dispersion, it is preferable to use a basic dye as a dye for coloring the styrene-acrylonitrile resin particles in consideration of the effect of this dispersant. .

  Furthermore, among basic dyes, xanthene-based, triaryl skeleton basic dyes, and azo skeleton basic dyes are preferred.

  The content of the colorant in the dispersion of the present invention is preferably 0.1 to 10% by mass, and preferably 0.1 to 5% by mass based on the total mass of the dispersion. In particular, in the present invention, as described above, the colorant is preferably used for coloring the styrene-acrylonitrile resin particles, and the content of the colorant in this case takes into consideration the colorability of the styrene-acrylonitrile resin particles. Then, it is more preferable that it is 0.1-3 mass% on the basis of the total mass of a dispersion.

  In addition, in order to adjust the color of the ink composition containing the dispersion, the colorant used for the preparation of the dispersion can be further added to the ink composition containing the dispersion. Further, for the purpose of adjusting the color and the like, a colorant having a different color can be further added. Further, uncolored styrene-acrylonitrile resin particles can be further combined with the ink composition containing the dispersion.

式中、
ｘは、１〜５の整数であり、好ましくは１〜３の整数である。
Ｃ_２Ｈ_４Ｏはエチレンオキシド基、Ｃ_３Ｈ_６Ｏはプロピレンオキシド基であり、
ここで、エチレンオキシド基およびプロピレンオキシド基は、それぞれブロックを形成していても、ランダムに配列されていてもよい。
ｙおよびｚは、それぞれ、エチレンオキシド付加モル数およびプロピレンオキシド付加モル数であり、ｙ≧１かつｚ≧０である。好ましくは、ｚ＝０である。 Specific dispersing agent used in dispersing agent present invention having the group R ¹ is a dispersant having a group R ¹ of the formula (1).

Where
x is an integer of 1 to 5, preferably an integer of 1 to 3.
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged.
y and z are the number of moles of ethylene oxide addition and the number of moles of propylene oxide addition, respectively, and y ≧ 1 and z ≧ 0. Preferably, z = 0.

式中、Ｒ^２は、ＯＨまたはＲ^１であり、Ｒ^１は、前記したとおりである。 Examples of the dispersant having the group R ¹ include a polyoxyalkylene phenyl ether type represented by the formula (2), a polyoxyalkylene phenyl ether phosphate type represented by the formula (3), and a polyoxyalkylene phenyl ether sulfate. An ester type is mentioned. In the present invention, the phosphate ester type and the sulfate ester type may be neutralized with a base, and examples thereof include alkali metal salts such as sodium salts and potassium salts, ammonium salts, and amine salts.
R ¹ -H (2)

In the formula, R ² is OH or R ¹ , and R ¹ is as described above.

Specific examples of the polyoxyalkylene aryl ether type include “Emulgen A-60”, “Emulgen A-500” (Kao Corporation), “Neugen EA-87”, “Neugen EA-137”, “Neugen EA”. -157 "," Neugen EA-167 "," Neugen EA-177 "," Neugen EA-197D "," Neugen EA-207D "(Daiichi Kogyo Seiyaku Co., Ltd.).
Examples of the polyoxyalkylene aryl ether phosphate ester type include Prisurf AL (Daiichi Kogyo Seiyaku Co., Ltd.).

The molecular weight of the dispersing agent having a radical ^{R 1} is not particularly limited, it preferably has a molecular weight of 200 to 20,000.

  Moreover, 10-19 are preferable about the HLB value of the dispersing agent represented by Formula (2). This is because when the HLB value is in the above range, the fluidity and dispersion stability tend to be improved. Furthermore, excellent dispersion stability is obtained by the solubility of the dispersant in water or water-soluble organic solvent and stable adsorption to the styrene-acrylonitrile resin particles, and the effects of the present invention can be demonstrated stably over a long period of time. Considering that it is easy, the HLB value is more preferably 10 to 16, and particularly preferably 12 to 14.

In addition, the HLB value of the dispersing agent represented by Formula (2) is a value calculated from the Griffin method, and is calculated by the following formula.
HLB value = 20 × (mass% of hydrophilic group) = 20 × (total formula weight of hydrophilic group / molecular weight of surfactant)

In the dispersion according to the present invention, the dispersant having a radical R ^1, but is capable of uniformly dispersing the components that may be present in insoluble state in water is the main solvent, in particular, styrene - acrylonitrile resin particles In contrast, it exhibits an excellent dispersion effect.

Furthermore, according to the study by the present inventors, the dispersant having the group R ¹ works effectively when the styrene-acrylonitrile resin particles are colored with the colorant. In particular, it has been found that there is an effect of suppressing aggregation of the styrene-acrylonitrile resin particles before coloring, and further suppressing aggregation of the obtained colored resin particles, thereby providing excellent dispersion stability to the dispersion. It was. Furthermore, since the dispersant having the group R ¹ also has an effect of uniformly coloring the styrene-acrylonitrile resin particles uniformly with a colorant, the resulting dispersion and the ink composition comprising the dispersion are: It was also found that the color developability was excellent. Therefore, in the present invention, the dispersant having the group R ¹ is extremely effective to be used for coloring and dispersing the styrene-acrylonitrile resin particles, and is good for the ink composition comprising the dispersion and the dispersion. Color development and dispersion stability can be achieved.

Further, according to the study by the present inventors, an excellent dispersion stability can be obtained by using a dispersant having the group R ^1. Therefore, in an ink composition comprising the dispersion according to the present invention, an ink It was also found that the fluidity was improved and the blurring at the time of writing was improved. Ink compositions that do not contain a dispersant having the group R ¹ may cause fading when used for writing after a lapse of time, but such fading is improved in an ink composition comprising a dispersion according to the present invention. . This is because the dispersant having the group R ¹ acts on the surface of the styrene-acrylonitrile resin particles to reduce the contact resistance between the particles, whereby the fluidity of the ink composition comprising the dispersion or the dispersion (ink It is considered that (fluidity) is improved and blurring is reduced. Such an effect is obtained by comparing the styrene-acrylonitrile resin particles and the group R ¹ in comparison with the case where a commonly used inorganic pigment, an organic pigment such as phthalocyanine blue or quinacridone red, and the dispersant having the group R ¹ are used in combination. This is noticeable when used in combination with a dispersing agent having a.

This is not desired to be bound by theory, but is presumed as follows. The dispersant having the group R ¹ has an alkylene oxide group and a plurality of aromatic rings, and has a hydrophilic part and a hydrophobic part in one molecule. Hydrophobic sites can be adsorbed on the surface of pigments, inorganic particles, resin particles, and the like to suppress aggregation of the pigments. In particular, the aromatic ring portion contained in the group R ¹ causes an interaction between the pigment and, in particular, a styrene-acrylic resin particle having a phenyl group, etc., and therefore has excellent adsorptivity and contributes to dispersion stability. it is conceivable that. In the present invention, since the resin particles have an aromatic ring and a strong interaction occurs with the dispersant used in the present invention, it is considered that better dispersion stability can be obtained.

The content of the dispersant having a group R ¹ in the dispersion of the present invention is preferably 0.1 to 10% by mass based on the total mass of the dispersion. If the content of the dispersant having the group R ¹ is 0.1% by mass or more, an effect as a dispersant of the dispersant having the group R ¹ can be obtained, and excellent dispersion stability can be obtained. if 10 mass% or less, suppress the occurrence of preventing residual air bubbles in the dispersion resulting from the foaming characteristics the dispersant has having the group R ^1, precipitates from the dispersant further comprising a group R ¹ can do. Furthermore, when coloring the styrene-acrylonitrile resin particles, considering aggregation of the styrene-acrylonitrile resin particles and uniform coloring, it is preferably 0.1 to 5% by mass, It is especially preferable that it is 5 mass%.

The dispersion according to the present invention may contain a dispersant other than the dispersant having the group R ¹ . Such a dispersant can be arbitrarily selected. However, in the present invention because it is achieved by using a dispersing agent having a group R ¹ better characteristics than the conventional dispersants, the content thereof is preferably low. For example, a dispersant having a nonylphenol skeleton such as polyoxyalkylene aryl ether such as polyoxyethylene nonylphenyl ether has been used as a dispersant to be blended in a conventional dispersion. However, based on the total mass of the dispersion, it is preferably 1% by mass or less, more preferably 0.2% by mass or less, particularly preferably 0.02% by mass or less, and the content is Most preferably it is zero. In recent years, it has been found that a dispersant having a nonylphenol skeleton tends to have higher safety when the addition amount is smaller. Therefore, the dispersion according to the present invention also realizes higher safety. In the present invention, the content of zero means that it is below the detection limit, which cannot be detected by various measuring devices.

The water solution is not particularly limited, for example, may be used conventional water such as ion exchanged water, distilled water, and tap water.

Other Additives The dispersion according to the present invention may contain any additive as required. The additive that can be used is described as follows.

  The dispersion according to the invention preferably further comprises a preservative. As preservatives, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetrachloro-4- (methylsulfonyl) pyridine, 2-pyridinethiol-1- Examples include sodium oxide, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and 2-n-octyl-4-isothiazolin-3-one.

The dispersion according to the present invention preferably further comprises a pH adjuster. Examples of the pH adjuster include basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, and sodium hydroxide, basic organic compounds such as sodium acetate, triethanolamine, and diethanolamine, lactic acid, and citric acid. In the present invention, compatibility with the dispersing agent having a group R ^1, if further consideration of the temporal stability of the dispersion, it is preferable to use a basic organic compound, if more considered, triethanolamine is weakly basic Is preferably used. These pH adjusters may be used alone or in combination of two or more.

  The dispersion according to the present invention preferably further comprises a water-soluble organic solvent. Preliminary inclusion of a water-soluble organic solvent when preparing the dispersion is effective because it can be expected to prevent sedimentation and improve dispersion stability by adjusting the specific gravity of the dispersion medium with the water-soluble organic solvent and improving the wettability of the colored resin particle surface. Is. Examples of the water-soluble organic solvent that can be used include polyhydric alcohols and glycol ethers. Among them, polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin are preferably selected and used.

<Water-based ink composition for writing instruments>
The water-based ink composition for writing instruments according to the present invention comprises styrene-acrylonitrile resin particles, a colorant, a specific dispersant, and water. About each component, it is fundamentally the same as the case where it is used as the said dispersion body, and there exists the same effect. In the present invention, the water-based ink composition for writing instruments does not necessarily contain the above-described dispersion, but only contains each component, and exhibits excellent dispersion stability and the like due to its constitution.

  When the color is adjusted with a combination of styrene-acrylonitrile resin particles and a colorant, to achieve the same color as when using inorganic pigments such as ultramarine and iron oxide, and organic pigments such as phthalocyanine blue and quinacridone red In general, a larger amount of colorant is required. Therefore, in order to achieve excellent color developability in the ink composition according to the present invention, the content of the styrene-acrylonitrile resin particles may be 5 to 35% by mass based on the total mass of the ink composition. More preferably, it is 15-25 mass%, and it is especially preferable.

In the production of the ink composition, it is preferable to produce a colored resin particle dispersion in advance and prepare an ink composition using the dispersion in terms of uniformity of dispersion, dispersion stability, and other properties and processes.
Therefore, the ink composition according to the present invention preferably comprises a dispersion. In this case, the content of the dispersion in the ink composition according to the present invention is preferably 20 to 80% by mass, more preferably 30 to 60%, based on the total mass of the ink composition.

  The ink composition according to the present invention can contain any additive as required. Optional additives can also include the preservatives, pH adjusters and water-soluble organic solvents exemplified above in the dispersion. Arbitrary additives other than the above will be described as follows.

  Preferred additives include polysaccharides. Polysaccharides bring about various effects, but mainly bring about effects such as adjustment of ink viscosity, application of shear thinning, and improvement of anti-drying performance as described later. Specific examples include dextrin, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivative, and diutane gum.

  The ink composition according to the present invention preferably comprises an ink viscosity modifier. This is because, when the ink composition according to the present invention is used for a writing instrument, it can be expected to prevent sedimentation of styrene-acrylonitrile resin particles or the like and to easily maintain a uniform and good dispersion state. In particular, when used in a ballpoint pen, it is preferable to use a shear thinning agent as the ink viscosity modifier. This is because by using a shear thinning agent, the viscosity at the time of standing of the ink composition is kept high, it is easy to maintain a uniform and good dispersion state, and while preventing sedimentation of styrene-acrylonitrile resin particles, When writing, the shear force generated by the rotation of the ball at the tip of the tip is applied to the ink composition, the viscosity of the ink composition is reduced, and good ink ejection properties are obtained. It is.

  Examples of the shear thinning agent include cross-linked acrylic acid polymers, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, diutan gum and other association thickeners. Agents. Of these, it is preferable to use polysaccharides. Furthermore, when the ink composition according to the present invention is used with a ballpoint pen, xanthan gum or succinoglycan, which is easy to obtain excellent dispersion stability and good handwriting, is used. It is particularly preferable to use succinoglycan. These shear thinning agents may be used alone or in combination of two or more.

In the present invention, when an ink viscosity modifier is included, the ink viscosity of the ink composition of the present invention is 500 to 5,000 mPa · s at a shear rate of 1.92 sec ⁻¹ in a 20 ° C. environment. Preferably, when the ink viscosity is within the above numerical range, it is possible to obtain good handwriting that is excellent in ink fluidity and dispersion stability, has good ink ejection properties, and is free from blurring and blurring of handwriting. In particular, the ink viscosity is 1,000 to 3,000 mPa · s in consideration of dispersibility of styrene-acrylonitrile colored resin particles colored with a colorant and good ink discharge properties from the pen tip of the ink composition. Is more preferable.

  In addition, the ink composition of the present invention preferably comprises dextrin. When the ink composition contains a component that can exist in an insoluble state in water, which is the main solvent such as styrene-acrylonitrile resin particles and pigments, the water evaporates at the pen tip of a writing instrument containing the ink, and the ink May dry and solidify and clog the ink flow path. When such a phenomenon occurs, ink ejection properties are affected, and the writing instrument may have a remaining amount of ink but may not be able to write again. For this reason, it is preferable to improve dry-up resistance. Therefore, for example, it is necessary to consider improvement in dry-up resistance at the tip of a ballpoint pen tip. Dextrin has the effect of forming a film on the nib and preventing evaporation of the solvent in the ink. For this reason, the use of dextrin is effective because an ink composition having excellent dry-up resistance can be obtained. In particular, when the content of styrene-acrylonitrile resin particles is high in order to make it easy to obtain good color developability, the total solid content in the ink also increases, and the dry-up resistance at the tip of the chip tends to decrease. Therefore, it is preferable to use dextrin. Dextrin is a general term for substances in which several α-glucoses are polymerized by glycosidic bonds, and is a kind of dietary fiber, and is obtained by hydrolysis of starch or the like.

  The mass average molecular weight of dextrin is preferably 5,000 to 120,000. When it is 120,000 or more, the coating film formed on the pen tip is hard, and there is a tendency that the handwriting tends to be blurred during writing at the time of dry-up. On the other hand, if it is less than 5,000, it is difficult to give a viscosity change that improves the dispersion stability over time, dampness of dextrin tends to be high, and the film formed on the pen tip is soft and stable at the pen tip. It is difficult to maintain, and the evaporation of the solvent in the ink tends to be difficult to suppress. Considering further improvement of the above effect, it is preferable to use dextrin having a mass average molecular weight of 20,000 to 100,000.

  The dextrin content is preferably 0.1 to 5% by mass based on the total mass of the ink composition. This is because if the amount is less than 0.1% by mass, the effect of improving the dry-up resistance property tends not to be obtained sufficiently, and if it exceeds 5% by mass, it tends to be difficult to dissolve in the ink. If considering the dissolution stability in the ink, 0.1 to 3% by mass is preferable, and considering the improvement of the dry-up resistance, 1 to 3% by mass is most preferable.

  Therefore, when the ink composition according to the present invention is used for a writing instrument, it preferably contains a polysaccharide, more preferably contains two or more kinds of polysaccharides, and exhibits excellent dispersion stability and dry resistance. Up performance can be obtained. In particular, when the ink composition of the present invention is used with a ballpoint pen, it preferably comprises succinoglycan or xanthan gum and dextrin, and particularly preferably comprises succinoglycan and dextrin.

  In order to improve the dry-up resistance, it is preferable to add a water-soluble organic solvent to the ink composition. Examples of the water-soluble organic solvent that can be used include polyhydric alcohols and glycol ethers. Among them, polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin are preferably selected and used. This is because these solvents reduce the specific gravity difference between the styrene-acrylonitrile resin particles and the dispersion medium, improve the wettability, contribute to the dispersion aid of the dispersion, and the moisture absorption effect of polyhydric alcohols. This is because it can be imparted to a product and the dry-up resistance can be improved.

  The ink composition according to the present invention can also comprise resin particles other than styrene-acrylonitrile resin particles.

The dispersant having the group R ¹ used in the present invention significantly improves the dispersion stability of the styrene-acrylonitrile resin particles, but also contributes to the dispersion stability of other resin particles. For this reason, even when resin particles are added for various purposes such as ink leakage suppression and writing quality improvement, the ink composition of the present invention can maintain excellent dispersion stability. For this reason, in the present invention, further comprising resin particles (excluding styrene-acrylonitrile resin particles) further obtains desired performance obtained by various resin particles without impairing the dispersion stability of the ink composition. Can be effective.

Examples of the resin particles include olefin resin particles, acrylic resin particles, urethane resin particles, styrene-butadiene resin particles, polyester resin particles, vinyl acetate resin particles, and benzoguanamine / formaldehyde resin particles.
The ink composition according to the present invention comprising the dispersant having the group R ¹ , the styrene-acrylonitrile resin particles, and the colorant is particularly excellent in dispersion stability. Therefore, there is a high possibility that ink leakage will occur. For this reason, in this invention, it is preferable to use the resin particle of an olefin resin particle and a benzoguanamine formaldehyde resin particle with a high nib ink leak suppression effect.

  In addition, the ink composition of the present invention may further contain additives such as a rust inhibitor, a chelating agent, a moisturizing agent, a penetrating agent, and a lubricant for the purpose of further improving the ink physical properties and functions.

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

  Examples of the humectant include urea or sorbit, N, N, N-trialkylamino acids such as trimethylglycine, triethylglycine, and tripropylglycine in addition to the polyhydric alcohol solvent.

  Furthermore, various surfactants may be included as a penetrating agent and a surface tension adjusting agent, and examples thereof include nonionic, anionic, and cationic surfactants. Also included are surfactants having an acetylene bond in the structure, silicone surfactants, fluorine surfactants, and the like.

  In addition, the ink composition according to the present invention may contain a chelating agent for sequestering metals present in the ink composition. Such chelating agents include ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol etherdiaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethyl Examples thereof include glycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and alkali metal salts, ammonium salts, and amine salts thereof. Here, for example, in a writing instrument such as a ballpoint pen or a fountain pen, the metal component may be eluted in the ink composition because the ink composition contacts the metal. Such metal ions are believed to inhibit the stability of the ink composition, and conventional ink compositions generally contain a chelating agent. However, as a result of further intensive studies by the present inventors, the ink composition according to the present invention containing a specific material is particularly excellent in the temporal stability of the ink composition by making the addition amount of the chelating agent below a certain level. I found. Further, when a specific phosphoric acid ester is used, the ink composition of the present invention is characterized in that no deterioration of stability due to metal ions is observed even if it does not contain a chelating agent. In other words, the ink composition according to the present invention has high stability even when the ink composition is used in a ballpoint pen or a fountain pen, which has many opportunities to come into contact with metal. For this reason, the content of the chelating agent in the ink composition according to the present invention is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, based on the total mass of the ink composition. Preferably, it is 0.05 mass% or less, more preferably 0.02 mass% or less, and most preferably the content is zero.

  Further, the ink composition of the present invention can further contain a phosphate ester surfactant. In addition, the compound represented by Formula (3) may be contained as this phosphate ester type surfactant. In addition to the effect of improving the dispersibility of the ink composition, this surfactant also acts as a lubricant when the ink composition is used in a ballpoint pen. The lubricant improves the lubricity between the ball and the ballpoint pen tip of the ballpoint pen, and smoothes the rotation of the ball, thereby suppressing the wear of the ball seat and improving the writing quality. The phosphoric acid ester-based surfactant having a phosphoric acid group used in the present invention has a property that the phosphoric acid group is easily adsorbed to a metal, so that it improves lubricity and suppresses wear and writing of the ball seat. Easy to improve. For this reason, when the ink composition of the present invention is applied to a ballpoint pen, a particularly excellent writing quality can be realized. However, since this surfactant contributes not only to the lubricity but also to the improvement of the dispersibility, it works effectively even when the ink composition is used for a writing instrument other than a ballpoint pen.

  Furthermore, the phosphate ester surfactant has an effect of adjusting the surface tension. For this reason, particularly in a writing instrument having a comb groove-like ink flow rate adjusting member, which will be described later, and having a supply mechanism for interposing this to supply the ink composition to the pen tip, excellent wetting with respect to the ink flow rate adjusting member It is preferable because it exhibits properties. Therefore, the ink composition according to the present invention is also preferable for fountain pens, markers, sign pens, ballpoint pens and the like having comb groove-shaped ink flow rate adjusting members.

  Examples of phosphate ester surfactants include linear alcohol-based surfactants, styrenated phenol-based surfactants, nonylphenol-based surfactants, octylphenol-based surfactants, among others, linear alcohol-based surfactants and styrenated phenol-based surfactants. It is preferable to use a phosphate ester surfactant.

  In the present invention, the phosphate ester-based surfactant preferably has an HLB value of 5 to 15, and more preferably 6 to 13. Moreover, it is preferable that carbon number of the alkyl group or alkylallyl group which a phosphoric acid ester type surfactant has in this invention is 6-30, It is more preferable that it is 8-18, It is 10-14. Particularly preferred. This is because a linear phosphate ester surfactant with a specific HLB value and carbon number has excellent writing stability, such as good handwriting with improved line skipping and faintness can be stably obtained. This is because the dispersion effect can be improved synergistically with the dispersant used in the present invention, and at the same time a lubrication effect can be brought about.

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

  In addition, as a specific example of a phosphate ester-based surfactant, Plysurf series (Daiichi Kogyo Seiyaku Co., Ltd.) and the like can be mentioned. As a linear alcohol phosphate-based surfactant, Plysurf A212C, A208B, A213B, A208F, A215C, A219B, A208N, and styrenated phenol-based surfactants include Plysurf AL. Nonylphenol-based Plysurf 207H, A212E, and A217E, and the octylphenol type includes Prisurf A210G. The same compound as that used in the dispersant according to the present invention may be used as a lubricant for the ink composition.

  When the phosphate ester surfactant is added, the content is preferably 0.1 to 2.0% by mass, and preferably 0.5 to 1.5% by mass based on the total mass of the ink composition. More preferred. In the ink composition according to the present invention, materials other than the phosphate ester surfactant can be used as the surfactant or lubricant. Such materials include surfactants other than phosphate ester surfactants and fatty acids.

  Specific examples of the fatty acid include linoleic acid and oleic acid, and specific examples include OS soap, NS soap, FR-14, FR-25 (Kao Corporation) and the like.

In addition, the ink composition according to the present invention contains a dispersant having a group R ¹ , a phosphate ester surfactant, and a chelating agent such as ethylenediaminetetraacetic acid within a specific range. Since there exists an effect which improves stability with time, it is more preferable. Specifically, the total content of the dispersant having the group R ¹ , the phosphate ester surfactant, and the chelating agent is preferably 0.1 to 10% by mass based on the total mass of the ink composition. Furthermore, it is preferable that it is 0.1-3 mass%.

  Moreover, it is preferable that the compounding ratio of the chelating agent with respect to the phosphate ester-based surfactant is 0 or more and less than 0.05 on a mass basis.

Further, in the present invention, with respect to the total amount of dispersant and phosphoric acid ester-based surfactant having a group R ^1, better low ratio of the amount of the chelating agent, jump line when using the ink composition in the writing instrument And there is a tendency to reduce scum. Specifically, (the amount of chelating agent) / [(the amount of dispersing agent having group R ¹ ) + (the amount of phosphoric acid ester surfactant)] is preferably 0.025 or less. , 0.005 or less, and more preferably zero.

The total content and the dispersing agent and the phosphoric acid ester surfactant and a chelating agent having a group R ^1, for a phosphoric acid ester surfactant, the compounding ratio of the chelating agent is within the above range, the ink composition Since the product exhibits good stability and good handwriting can be obtained by using the ink composition, it is more preferable.

The total content of the dispersant having the group R ¹ , the phosphate ester-based surfactant and the chelating agent, and the total amount of the dispersant having the group R ¹ and the phosphate ester-based surfactant, If the ratio of the blending amounts is within the above numerical range, the ink composition exhibits particularly good stability, so that a good handwriting can be obtained by using the ink composition, which is most preferable.

  The pH of the ink composition according to the present invention is preferably 6-10. This is because when the pH value approaches the acidic side of less than 6, the aging stability of the ink composition may deteriorate, and when the ink composition of the present invention is used for a ballpoint pen or a fountain pen, the ink composition Corrosion of metal members in contact with objects tends to occur, and when the pH value exceeds 10 and approaches the strong alkali side, the ink composition tends to fade or discolor and it is difficult to obtain good handwriting. It is. Also, when the styrene-acrylonitrile resin particles are colored with a colorant and used as styrene-acrylonitrile colored resin particles, the ink composition has good aging stability and good handwriting with good color development and improved line skipping and fading. In particular, the pH value is preferably 7 to 9 in consideration of improvement in writability such as being obtained. In the present invention, the pH value indicates a value measured at 20 ° C. using an IM-40S type pH meter.

<Method for producing dispersion>
Although the preparation method of the dispersion by this invention is not specifically limited, It can prepare as follows. Styrene-acrylonitrile resin particles or styrene-acrylonitrile resin particle dispersion, a dispersant, water, and optionally an optional additive are uniformly mixed to prepare a mixed solution. The styrene-acrylonitrile resin particles used here are preferably those obtained by emulsion polymerization. A colorant, a colorant aqueous solution, or a colorant aqueous dispersion is added to the mixed solution, and the mixture is subjected to a dispersion treatment. A dispersion of styrene-acrylonitrile resin particles is generally easy to obtain and facilitates dispersion treatment, so that a dispersion of particles is preferably used. The particle dispersion preferably includes an aqueous dispersion medium.
The dispersion treatment is preferably performed under heating conditions. More preferably, it is carried out under a temperature condition of 60 ° C. or higher, more preferably 70 ° C. or higher. The temperature can also be changed as the dispersion process proceeds. The upper limit of the temperature is not particularly limited, but for example, by performing the treatment at 90 ° C. or less, the dispersion treatment can be performed without special equipment. Specifically, a colorant, an aqueous colorant solution, or an aqueous colorant dispersion is added to a mixed liquid containing styrene-acrylonitrile resin particles at 20 to 30 ° C. while stirring with a propeller stirrer. And Thereafter, the temperature is gradually raised and the mixture is stirred at 70 to 80 ° C. for 1 to 24 hours to color the styrene-acrylonitrile resin particles, whereby a dispersion can be produced. In addition, various stirring machines, such as a propeller stirrer, a high-speed shearing stirrer, and a homogenizer, can be used for a dispersion process.

<Method for producing ink composition>
The method for preparing the ink composition according to the present invention is not particularly limited, but a colorant, a dispersant, a styrene-acrylonitrile resin particle, or a styrene-acrylontolyl resin particle dispersion, water, and necessary. It is preferable to add other components depending on the ink composition to obtain an ink composition. At this time, the mixing order is not particularly limited.
In addition, the ink composition according to the present invention is preferably prepared by adding a dispersion prepared in advance and, if necessary, other components. By sequentially adding other components to the styrene-acrylonitrile resin particles in a stable state, it is possible to obtain an ink composition while maintaining dispersion stability, the dispersion stability of the ink composition is further improved, and the color developability of handwriting, This is effective because ink ejection from the pen tip can also be improved. Such a method is preferable because the dispersion stability of the ink composition and the color development of the handwriting can be further improved.

  The ink composition according to the present invention can be produced by any conventionally known method. Specifically, it can be produced by blending the necessary amounts of the above components and mixing them with various agitators such as propeller agitation, homodisper, or homomixer, and various dispersers such as a bead mill.

<Writing instruments>
The structure and shape of the writing instrument filled with the water-based ink composition for a writing instrument of the present invention are not particularly limited, and those conventionally used can be applied, and fiber tips, felt tips, plastic tips, ball tip tips, etc. can be used as pen tips. It can be used for various writing instruments such as a marking pen, a ballpoint pen, and a fountain pen using a metal pen tip.

  In addition, the writing instrument that can use the ink composition according to the present invention may have a configuration in which the ink composition is directly filled, or an ink container or ink occlusion that can be filled with the ink composition. The body may be provided. The ink container or ink occlusion body may be an ink cartridge type writing instrument having a structure that can be detachably replaced with the writing instrument body.

  In addition, the writing instrument that can use the ink composition according to the present invention includes a cap-type writing instrument having a cap that covers the pen tip, and a protrusion and depression that can accommodate the pen tip in a shaft cylinder such as a knock type, a rotary type, and a slide type. A ballpoint pen is used.

  Further, the supply mechanism of the writing instrument in which the ink composition of the present invention can be used is not particularly limited. For example, (Mechanism 1) an ink guide core composed of a fiber bundle or the like is provided as an ink flow rate adjusting member, and the ink A mechanism for supplying the composition to the pen tip, (mechanism 2) a mechanism for supplying an ink flow rate adjusting member in the form of a comb groove and interposing it, and a mechanism for supplying the ink composition to the pen tip, (mechanism 3) an ink flow rate by a valve mechanism Examples include a mechanism that includes an adjusting member and supplies the ink composition to the pen tip, and (mechanism 4) a mechanism that directly supplies the ink composition to the pen tip without the ink flow rate adjusting member.

  When the specification of the ball-point pen when the water-based ink composition for a writing instrument according to the present invention is filled into the ball-point pen is examined, the ink consumption per 100 m of the water-based ball-point pen is A (mg), and the ball diameter is B (mm). 150 ≦ A / B ≦ 500, preferably 250 ≦ A / B ≦ 450. This is because it is easy to obtain good handwriting by making the ink consumption good by controlling the ink consumption with respect to the ball diameter and by suppressing the handwriting scraping by setting the above range. It is.

  The ink consumption was determined by using five test samples at a writing speed of 4 m / min under the conditions of 20 ° C., writing paper JIS P3201 writing paper, a writing angle of 65 ° and a writing load of 100 g. 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. The ball diameter is not particularly limited, but generally a ball of about 0.1 to 2.0 (mm) is used.

As for the specifications of the ball-point pen tip, the movable amount (clearance) of the ball in the ball-point pen tip in the vertical axis direction is preferably 20 to 50 μm, and more preferably 30 to 45 μm. This is because if it is in the above range, it is easy to obtain good handwriting by appropriately adjusting the ink discharge amount and suppressing line skipping and blurring, and if the clearance is within the above range, The ratio A / B is easy to adjust.
The amount of movement of the ball-point pen tip in the vertical axis direction (clearance) refers to the distance that the ball can move in the vertical axis direction of the ball-point pen tip body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Examples 101 to 110 and Comparative Examples 101 to 103: Dispersion>
Raw materials were blended as shown in Table 1 to prepare dispersions of Examples 101 to 110 and Comparative Examples 101 to 103. In addition, the numerical value of a composition in a table | surface shows the mass%.
For example, the dispersion of Example 101 was performed as follows. Dispersing agent, water dispersion of styrene-acrylonitrile resin particles, preservative, water-soluble organic solvent, pH adjuster, and water are uniformly mixed with the resulting liquid mixture. The dissolved aqueous solution was added at room temperature with stirring to obtain a uniform mixed solution. Thereafter, the temperature was gradually raised, and the mixture was stirred at 80 ° C. for 2 hours to color the styrene-acrylonitrile resin particles, thereby preparing a dispersion.

The obtained dispersion was evaluated by the following method. The obtained results are as shown in Table 1.
Dispersibility The dispersions of Examples 101 to 110 and Comparative Examples 101 to 103 were each collected on a glass slide and observed using an optical microscope, and the dispersibility of the dispersion was evaluated according to the following evaluation criteria.
The viscosity of the dispersion was measured by using an E-type rotational viscometer (model: DV-II + Pro, rotor: CPE-42, manufactured by Brookfield) at a shear rate of 19.2 sec-1 (rotation speed: 5 rpm) in a 20 ° C environment. ).
A: Aggregates were not confirmed and were uniformly dispersed.
B: Aggregates were not confirmed, but thickening of the dispersion was confirmed.
C: Aggregates were confirmed.
Dispersion stability The dispersions of Examples 101 to 110 and Comparative Examples 101 to 103 were placed in a tightly opened and closed glass test tube having a diameter of 15 mm and allowed to stand at 50 ° C. for 30 days, and then each dispersion was collected on a slide glass. The dispersion was observed using an optical microscope, and the dispersion stability of the dispersion was evaluated according to the following evaluation criteria.
The viscosity of the dispersion was measured by using an E-type rotational viscometer (model: DV-II + Pro, rotor: CPE-42, manufactured by Brookfield) at a shear rate of 19.2 sec-1 (rotation speed: 5 rpm) in a 20 ° C environment. ).
A: Aggregates were not confirmed, and a uniformly dispersed state was maintained.
B: Although the thickening or separation of the dispersion was slightly confirmed, it was at a practical level.
C: Aggregates were confirmed.
Dispersibility (overall evaluation)
A +: The dispersion was in a good state.
A: As a dispersion, it was a level with no practical problem.
B: It was a usable level as a dispersion.
C: As a dispersion, the level was not practical.

表中、
スチレン−アクリロニトリル樹脂粒子の水分散液：スチレン−アクリロニトリル樹脂粒子５０％水分散液、スチレン−アクリロニトリル樹脂粒子の平均粒子径０．４μｍ
分散剤Ａ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−８７」（第一工業製薬株式会社）、ＨＬＢ値１０．６、
分散剤Ｂ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−１３７」（第一工業製薬株式会社）、ＨＬＢ値１３．０、
分散剤Ｃ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−１５７」（第一工業製薬株式会社）、ＨＬＢ値１４．３、
分散剤Ｄ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−１６７」（第一工業製薬株式会社）、ＨＬＢ値１４．８、
分散剤Ｅ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−１７７」（第一工業製薬株式会社）、ＨＬＢ値１５．６、
分散剤Ｆ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−１９７Ｄ」（第一工業製薬株式会社）、ＨＬＢ値１７．５、
分散剤Ｇ：ポリオキシエチレンスチレン化フェニルエーテル「ノイゲンＥＡ−２０７Ｄ」（第一工業製薬株式会社）、ＨＬＢ値１８．７、
分散剤Ｈ：ポリオキシエチレンスチレン化フェニルエーテル「エマルゲンＡ−６０」（花王株式会社）、ＨＬＢ値１２．８、
分散剤Ｉ：ポリオキシエチレンスチレン化フェニルエーテル「エマルゲンＡ−５００」（花王株式会社）、ＨＬＢ値１８．０、
分散剤Ｊ：ポリオキシエチレンスチレン化フェニルエーテルリン酸エステル「プライサーフＡＬ」（第一工業製薬株式会社）、
分散剤Ｋ：ポリオキシエチレンアルキルエーテルリン酸エステル「プライサーフＡ２１９Ｂ」（第一工業製薬株式会社）、
分散剤Ｌ：β−ナフタレンスルホン酸ホルマリン縮合物ナトリウム塩、
着色剤Ａ：Ｃ．Ｉ．ベーシックバイオレット１１：１、
着色剤Ｂ：Ｃ．Ｉ．ベーシックレッド１：１、
防腐剤：１，２−ベンゾイソチアゾリン−３−オン、
ｐＨ調整剤：トリエタノールアミン、
水溶性有機溶剤Ａ：グリセリン
水溶性有機溶剤Ｂ：エチレングリコール

In the table,
Aqueous dispersion of styrene-acrylonitrile resin particles: 50% aqueous dispersion of styrene-acrylonitrile resin particles, average particle diameter of styrene-acrylonitrile resin particles 0.4 μm
Dispersant A: Polyoxyethylene styrenated phenyl ether “Neugen EA-87” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 10.6,
Dispersant B: Polyoxyethylene styrenated phenyl ether “Neugen EA-137” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 13.0,
Dispersant C: polyoxyethylene styrenated phenyl ether “Neugen EA-157” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 14.3,
Dispersant D: Polyoxyethylene styrenated phenyl ether “Neugen EA-167” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 14.8,
Dispersant E: Polyoxyethylene styrenated phenyl ether “Neugen EA-177” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 15.6,
Dispersant F: Polyoxyethylene styrenated phenyl ether “Neugen EA-197D” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 17.5,
Dispersant G: Polyoxyethylene styrenated phenyl ether “Neugen EA-207D” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 18.7,
Dispersant H: Polyoxyethylene styrenated phenyl ether “Emulgen A-60” (Kao Corporation), HLB value 12.8,
Dispersant I: polyoxyethylene styrenated phenyl ether “Emulgen A-500” (Kao Corporation), HLB value 18.0,
Dispersant J: Polyoxyethylene styrenated phenyl ether phosphate "Price Surf AL" (Daiichi Kogyo Seiyaku Co., Ltd.)
Dispersant K: Polyoxyethylene alkyl ether phosphate ester “Plysurf A219B” (Daiichi Kogyo Seiyaku Co., Ltd.),
Dispersant L: β-naphthalenesulfonic acid formalin condensate sodium salt,
Colorant A: C.I. I. Basic violet 11: 1,
Colorant B: C.I. I. Basic Red 1: 1
Preservative: 1,2-benzisothiazolin-3-one,
pH adjuster: triethanolamine,
Water-soluble organic solvent A: Glycerin Water-soluble organic solvent B: Ethylene glycol

<Examples 111 and 112: Change content of dispersant>
Dispersions of Examples 111 and 112 were prepared in the same manner except that the contents of the dispersants B and J were changed from 2.0 to 4.0% by mass with respect to Examples 102 and 110, respectively. The evaluation results of the obtained dispersion were equivalent to those of Examples 102 and 110, respectively.

<Examples 113 to 116: Change colorant>
For Examples 102 and 110, 0.6% by weight of Colorant A and 0.6% by weight of Colorant B were added to C.I. I. Dispersions of Examples 113 and 114 were prepared in the same manner except that the basic violet 15 was changed to 1.0% by mass. The evaluation results of the obtained dispersion were equivalent to those of Examples 102 and 110, respectively.
Further, in the same manner as in Examples 102 and 110, except that Colorant A 0.6% by mass and Colorant B 0.6% by mass were changed to Pigment Blue 15: 3 1.0% by mass. 115 and 116 dispersions were prepared. The evaluation results of the obtained dispersion were equivalent to those of Examples 102 and 110, respectively.

<Examples 201 to 216 and Comparative Examples 201 to 203: Ink compositions>
Using the dispersions prepared above (Examples 101 to 116 and Comparative Examples 101 to 103), the raw materials were blended as shown in Table 2, and the ink compositions of Examples 201 to 216 and Comparative Examples 201 to 203 were used. Adjusted. In addition, the numerical value of a composition in a table | surface shows the mass%.

  For example, the ink composition of Example 201 was prepared as follows. A base ink was prepared by heating and stirring the dispersion, dextrin, lubricant, rust inhibitor, preservative, pH adjuster, water-soluble organic solvent, and water of Example 101 with a magnetic hot stirrer.

  Then, while heating the prepared base ink, succinoglycan, which is an ink viscosity modifier (shear thinning agent), is added and thoroughly mixed and stirred using a homogenizer stirrer until uniform. Then, filtration was performed using a filter paper to obtain an ink composition.

  The obtained ink composition was evaluated by the following method. The obtained results are shown in Table 2.

In addition, as a result of measuring the pH value of the ink composition at 20 ° C. using the IM-40S type pH meter (manufactured by Toa DKK Co., Ltd.), the pH value of the ink composition of Example 202 was 8.2. . Further, the viscosity of the ink composition was measured using an E-type rotational viscometer (model: DV-II + Pro, rotor: CPE-42, manufactured by Brookfield) at a shear rate of 1.92 sec ⁻¹ (rotation number 0) in an environment of 20 ° C. The ink viscosity was measured under the condition of 0.5 rpm) and found to be 1540 mPa · s.

Dispersion stability test The ink compositions of Examples 201 to 216 and Comparative Examples 201 to 203 were placed in a 15 mm diameter closed glass test tube and allowed to stand at 50 ° C. for 30 days, and then each ink composition was slid. The sample was collected on glass and observed using an optical microscope, and the dispersion stability of the ink composition was evaluated according to the following evaluation criteria. The evaluation was as summarized in Table 2.
A: A good state in which aggregates are not confirmed and are uniformly dispersed.
B: Although the aggregate was slightly confirmed, it was a level with no problem in practical use.
C: Agglomerates were confirmed, and there was practical concern.
D: Sedimentation of aggregates was observed.

A ballpoint pen tip (ball ball tip) in which the ink compositions (1.0 g) of the writing performance test examples 201 to 216 and the comparative examples 201 to 203 were rotatably held by a cemented carbide ball having a diameter of 0.7 mm. A refill is prepared by filling the inside of an ink container having a longitudinal movement amount (clearance) of 30 μm), and this refill is attached to a gel ink ballpoint pen (trade name: G-2) manufactured by Pilot Corporation. And got a ballpoint pen. The obtained ballpoint pen was used as a test ballpoint pen, and the following writing performance test was performed.

Using a test ballpoint pen that has been confirmed to be writable, hand-draw and continuously write a spiral circle on the test paper (JIS P3201, writing paper A), and visually check the status of the resulting handwriting The writing performance was evaluated according to the following evaluation criteria. The results are summarized in Table 2.
A +: A good handwriting with good color development and no line skipping or blurring was obtained.
A: Although line skipping and blurring were slightly confirmed in the handwriting, a handwriting with good color development was obtained.
B: Slight line skipping and blurring were confirmed in the handwriting, but handwriting with good color development was obtained.
C: Although line skipping and blurring were confirmed in the handwriting, it was a level with no practical problem.
D: A lot of line skips and blurs were confirmed in the handwriting, good handwriting was not obtained, or writing was impossible.

Stability test over time The test ballpoint pen used for the writing performance test was left at 50 ° C. for 30 days with the pen point down, and then handwritten in a spiral on the test paper (JIS P3201, writing paper A). The circle was continuously written, the situation of the obtained handwriting was visually confirmed, and writing performance was evaluated according to the following evaluation criteria. The results are summarized in Table 2.
A +: A good handwriting with good color development and no line skipping or blurring was obtained.
A: Although line skipping and blurring were slightly confirmed in the handwriting, a handwriting with good color development was obtained.
B: Slight line skipping and blurring were confirmed in the handwriting, but handwriting with good color development was obtained.
C: Although line skipping and blurring were confirmed in the handwriting, it was a level with no practical problem.
D: A lot of line skips and blurs were confirmed in the handwriting, good handwriting was not obtained, or writing was impossible.

表中、
デキストリン：デキストリン、質量平均分子量１００，０００、サンデックシリーズ（三和デンプン工業株式会社）、
サクシノグリカン：サクシノグリカン、三晶株式会社
潤滑剤Ａ：ポリオキシエチレンアルキル（Ｃ_１２、Ｃ_１３）エーテルリン酸エステル「プライサーフＡ２０８Ｎ」（第一工業製薬株式会社）、ＨＬＢ値７
潤滑剤Ｂ：ポリオキシエチレンラウリルエーテルリン酸エステル「プライサーフＡ２１９Ｂ」（第一工業製薬株式会社）、ＨＬＢ値１６．２
防錆剤：ベンゾトリアゾール
防腐剤：１，２−ベンゾイソチアゾリン−３−オン
ｐＨ調整剤：トリエタノールアミン
水溶性有機溶剤Ｂ：エチレングリコール
キレート剤：エチレンジアミン四酢酸

In the table,
Dextrin: dextrin, weight average molecular weight 100,000, Sandeck series (Sanwa Starch Co., Ltd.),
Succinoglycan: Succinoglycan, Sanki Co., Ltd. Lubricant A: Polyoxyethylene alkyl (C ₁₂ , C ₁₃ ) ether phosphate ester “Plisurf A208N” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 7
Lubricant B: Polyoxyethylene lauryl ether phosphate “Price Surf A219B” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 16.2
Rust inhibitor: Benzotriazole Preservative: 1,2-Benzisothiazolin-3-one pH adjuster: Triethanolamine Water-soluble organic solvent B: Ethylene glycol Chelating agent: Ethylenediaminetetraacetic acid

<Examples 217 to 222: Changing the polysaccharide in the ink composition>
Inks of Examples 217 and 218 were the same as in Examples 202 and 210 except that the dextrin was changed to a dextrin having a weight average molecular weight of 30,000 (Sandeck Series (Sanwa Starch Co., Ltd.)). A composition was prepared. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
Ink compositions of Examples 219 and 220 were prepared in the same manner as in Examples 202 and 210, except that succinoglycan was changed to xanthan gum (Sanki Co., Ltd.). The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.

Ink compositions of Examples 221 and 222 were prepared in the same manner as in Examples 202 and 210, except that dextrin was not included. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
With the pen tip of the test ballpoint pen exposed to the air, leave it for one day at 50 ° C and completely dry, and then continuously write letters (letter size is 8 mm in length and width) on the test paper to recognize the handwriting. When the number of characters until returning to the extent possible was counted, the ballpoint pens using the ink compositions of Example 202 and Example 210 containing dextrin showed the ink compositions of Examples 221 and 222 containing no dextrin. Compared to the ballpoint pen used, the number of characters until return was small, and the dry-up resistance tended to be excellent.

<Examples 223 to 228: Changing the lubricant in the ink composition>
The same as in Examples 202 and 210, except that the lubricant A was changed to polyoxyethylene tridecyl ether phosphate “Price Surf A215C” (Daiichi Kogyo Seiyaku Co., Ltd.), HLB value 11.5. Thus, the ink compositions of Examples 223 and 224 were prepared. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
For Examples 202 and 210, except that the lubricant A was changed to a polyoxyethylene styrenated phenyl ether phosphate “Price Surf AL” (Daiichi Kogyo Seiyaku Co., Ltd.), an HLB value of 5.6, In the same manner, ink compositions of Examples 225 and 226 were prepared. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
Ink compositions of Examples 227 and 228 were prepared in the same manner as in Examples 202 and 210, except that the lubricant A was changed to the lubricant B. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.

<Examples 229 to 232: Further adding resin particles in the ink composition>
Implementation was performed in the same manner as in Examples 202 and 210, except that benzoguanamine formaldehyde condensate (“Eposter M05”, particle size 5 μm, manufactured by Nippon Shokubai Co., Ltd.) was added to 0.2 mass%. The ink compositions of Examples 229 and 230 were prepared. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
The inks of Examples 229 and 230 were the same as in Examples 202 and 210 except that olefin resin particles ("Chemical M200", Mitsui Chemicals, Inc.) were further added to 0.2% by mass. A composition was prepared. The evaluation results of the obtained ink composition were equivalent to those of Examples 202 and 210, respectively.
Furthermore, a weight of 40 g is attached to the shaft cylinder portion of the test ballpoint pen, and the ballpoint pen tip is discharged downward to keep the ballpoint pen tip ball in contact with the bottom of the ballpoint pen display case at 20 ° C. and 65%. When left in an RH environment for one day, the amount of ink leakage from the tip of the ballpoint pen tip was measured and an ink leakage test was conducted. Examples 229 to 232 containing resin particles (excluding styrene-acrylonitrile resin particles) were used. The ball-point pen using the ink composition of Example 1 229 to 232 has less ink leakage than the ball-point pen using the ink composition that does not contain resin particles (excluding styrene-acrylonitrile resin particles). The ballpoint pen using the pen is excellent in dispersion stability, writing performance, and stability over time, and further prevents ink leakage from the pen tip. It was found to be an excellent ballpoint pen can be suppressed.

<Examples 233 to 236: Changing the chelating agent in the ink composition>
Ink compositions of Examples 233 and 234 were prepared in the same manner as in Examples 223 and 224, except that a chelating agent (ethylenediaminetetraacetic acid) was added to 0.01% by mass. The evaluation results of the obtained ink composition were equivalent to those in Examples 223 and 224, respectively.
Ink compositions of Examples 235 and 236 were prepared in the same manner as in Examples 223 and 224, except that no chelating agent was contained. The evaluation results of the obtained ink composition were equivalent to those in Examples 223 and 224, respectively. In addition, Example 233 and 234 had the stable ink discharge property compared with Example 223 and 224, and Example 235 and 236 had the more stable ink discharge property.

<Example 301: Ink composition containing no dispersion>
The ink composition of Example 301 was obtained by the following composition and method.
Aqueous dispersion of styrene-acrylonitrile resin particles (50% aqueous dispersion of styrene-acrylonitrile resin particles, average particle diameter of styrene-acrylonitrile resin particles 0.4 μm) 40.0% by mass
・ Polyoxyethylene styrenated phenyl ether phosphate "Price Surf AL" (Daiichi Kogyo Seiyaku Co., Ltd.) 2.0% by mass
Colorant A: C.I. I. Basic violet 11: 1 0.3% by mass
Colorant B: C.I. I. Basic Red 1: 1 0.3% by mass
Dextrin: mass average molecular weight 100,000, Sandeck series (Sanwa Starch Co., Ltd.) 1.0% by mass
・ Succinoglycan (Sanki Co., Ltd.) 0.4% by mass
・ Rust preventive agent: 0.5% by mass of benzotriazole
Preservative: 1,2-benzisothiazolin-3-one 0.105% by mass
PH adjuster: triethanolamine 2.25% by mass
Water-soluble organic solvent: ethylene glycol 13.0% by mass
・ Water-soluble organic solvent: 3.0% by mass of glycerin
・ Water balance

Each component other than the above succinoglycan was heated and stirred with a magnetic hot stirrer to prepare a base ink. Then, while heating the base ink prepared above, succinoglycan was added, mixed and stirred thoroughly using a homogenizer stirrer until uniform, then filtered using filter paper, and the ink composition Got.
The obtained ink composition was evaluated in the same manner as described above. As for the obtained evaluation results, all of the dispersion stability test, the writing performance test, and the time stability test were superior to those of Comparative Examples 201 to 203, but compared with Example 226, the dispersion stability test. The results were equivalent, the writing performance test was equivalent, and the stability test over time was slightly inferior. That is, the ink composition containing no dispersion subjected to the dispersion treatment in advance has a low evaluation of stability over time as compared with the ink composition containing the dispersion. This is because the dispersion stability is improved by the combination of the styrene-acrylonitrile resin particles and the specific dispersant, but the styrene-acrylonitrile is not preliminarily treated with the colorant and the styrene-acrylonitrile resin particles. It is thought that the penetration and adsorption of the colorant to the resin particles were insufficient, and the effect of improving the stability over time was relatively small.
Further, Example 226 containing a dispersion was superior in water resistance to Example 301 containing no dispersion. This is presumably because, as described above, the ink composition containing the dispersion is preliminarily dispersed, so that there is little colorant not permeated and adsorbed on the styrene-acrylonitrile resin particles. However, since Example 301 contained a specific dispersant, it exhibited better water resistance than a conventional ink composition using a dye alone.

<Examples 401 and 402, and Comparative Example 401: Marking pen ink composition>
The ink composition of Example 401 was obtained by the following composition and method.
-Dispersion of Example 102 45.0 mass%
-Penetration agent: Nikkor PBC-34 1.0% by mass
Preservative: 1,2-benzisothiazolin-3-one 0.1% by mass
Water-soluble organic solvent: Glycerin 20.0% by mass
-Water remainder A dispersion, a penetrating agent, a preservative, and a water-soluble organic solvent were added and mixed by stirring with a propeller to obtain an ink composition. As a result of measuring the pH value of the ink composition at 20 ° C. using an IM-40S type pH meter (manufactured by Toa DKK Co., Ltd.), the pH value was 8.0.

  An ink composition 402 was obtained in the same manner as in Example 401 except that the dispersion was changed to the dispersion of Example 110.

  The ink composition of Comparative Example 401 was obtained in the same manner except that the dispersion of Example 401 was changed to the dispersion of Comparative Example 103. As a result of measuring the pH value of the ink composition at 20 ° C. using an IM-40S type pH meter (manufactured by Toa DKK Co., Ltd.), the pH value was 8.0.

  The obtained ink compositions of Examples 401 and 402 and Comparative Example 401 were put into a tightly opened and closed glass test tube having a diameter of 15 mm and allowed to stand at 50 ° C. for 30 days, and then each ink composition was collected on a slide glass. When observed with an optical microscope, the ink compositions of Examples 401 and 402 were more uniformly dispersed than the ink composition of Comparative Example 401.

  Further, the ink compositions of Examples 401 and 402 and Comparative Example 401 were impregnated in an ink occlusion body in which a polyester sliver was coated with a synthetic resin film, and accommodated in a shaft cylinder made of polypropylene resin, and the shaft was inserted through a holder. A marking pen tip (chisel type) made of polyester fiber was assembled in a connected state at the tip of the cylinder, and a cap was attached to obtain a marking pen.

  The obtained marking pen was used as a test writing tool, and spiral circles were continuously written by hand, and the state of the obtained handwriting was confirmed. With the test writing tool using the ink compositions of Examples 401 and 402, The obtained handwriting had less blur and good color development than the handwriting obtained with the test writing instrument using the ink composition of Comparative Example 401. In addition, the test writing instrument was left for 30 days at 50 ° C. with the pen tip down, and then handwritten and a spiral circle was continuously written on the test paper (JIS P3201, writing paper A). The handwriting obtained by the test writing instrument using the ink composition of Examples 401 and 402 was obtained by the test writing instrument using the ink composition of Comparative Example 401. Compared to the handwriting, there were few lines skipping and blurring and it was good.

  As described above, the ink composition according to the present invention is excellent in dispersion stability, and the components in the ink composition are uniformly dispersed without settling and agglomeration, resulting in good handwriting without blurring or line skipping. In addition, it was confirmed that the writing performance was excellent, the stability over time was also excellent, and it was easy to apply to writing tools of various colors, and the writing tool using the ink composition was excellent as a writing tool. It turned out to be a thing.

  The ink composition comprising the dispersion according to the present invention can be used for a writing instrument such as a water-based ballpoint pen, and the writing instrument in which the ink composition is accommodated can provide excellent characteristics.

Claims (14)

Styrene-acrylonitrile resin particles;
A colorant;
A dispersant having a group R ¹ of formula (1);

(Where
x is an integer of 1 to 5,
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged,
y and z are the number of moles of ethylene oxide added and the number of moles of propylene oxide added, respectively, y ≧ 1 and z ≧ 0)
water and,
A colored resin particle dispersion comprising:   The dispersion according to claim 1, wherein x is 1 to 3 and z is 0 in the dispersant. The dispersion according to claim 1 or 2, wherein the dispersant is represented by the formula (2).
R ¹ -H (2) The dispersion according to claim 1 or 2, wherein the dispersant is represented by the formula (3).

(Wherein R ² is OH or R ¹ )   The dispersion according to any one of claims 1 to 4, wherein the content of the dispersant is 0.1 to 10% by mass based on the total mass of the dispersion.   The dispersion according to claim 1, wherein the styrene-acrylonitrile resin particles have no polar group.   A water-based ink composition for a writing instrument, comprising the dispersion according to any one of claims 1 to 6.   The ink composition according to claim 7, wherein the ink composition further comprises a polysaccharide.   The ink composition according to claim 7 or 8, wherein the ink composition further comprises a colorant different from the colorant or the colorant. Styrene-acrylonitrile resin particles;
A colorant;
A dispersant having a group R ¹ of formula (1);

(Where
x is an integer of 1 to 5,
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged,
y and z are the number of moles of ethylene oxide added and the number of moles of propylene oxide added, respectively, y ≧ 1 and z ≧ 0)
water and,
A water-based ink composition for a writing instrument, comprising:   A writing instrument comprising the ink composition according to any one of claims 7 to 10. Styrene-acrylonitrile resin particles or styrene-acrylonitrile resin particle dispersion,
A dispersant having a group R ¹ of formula (1);

(Where
x is an integer of 1 to 5,
C ₂ H ₄ O is an ethylene oxide group, C ₃ H ₆ O is a propylene oxide group,
Here, the ethylene oxide group and the propylene oxide group may each form a block or may be randomly arranged,
y and z are the number of moles of ethylene oxide added and the number of moles of propylene oxide added, respectively, y ≧ 1 and z ≧ 0)
water and,
In a mixture comprising
A method for producing a colored resin particle dispersion, comprising adding a colorant, an aqueous colorant solution, or an aqueous dispersion of a colorant and dispersing the colorant.   The method according to claim 12, wherein the dispersion treatment is performed under warming conditions.   A method for producing an ink composition, comprising the method for producing a colored resin particle dispersion according to claim 12.