JP2009263591A - Water-based ink composition for ballpoint pen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink composition for a ballpoint pen which is excellent in water-resistance of handwriting, rapid in drying of handwriting, and excellent in feeling of writing. <P>SOLUTION: An oil-soluble dye excellent in water resistance is made to dissolve in water with an alkali-soluble styrene-acrylic acid resin and a basic material to form the water-based ink composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water-based ink composition for ballpoint pens which has excellent water resistance of handwriting, fast handwriting drying and excellent writing feeling.

Conventionally, water-based ballpoint pen inks and water-based ballpoint pen inks that use water-soluble dyes have the characteristics that the handwriting is vivid and the writing feeling is good, but the disadvantage is that the water resistance of the handwriting is inferior because the colorant is a water-soluble dye. There is. For this reason, the invention described in JP-A-10-306243 (Patent Document 1) contains a fluorine-based compound containing a fluoroalkyl group and an amino group in the molecule, a water-soluble dye, and an aqueous medium, thereby improving the water resistance of the handwriting. Ink imparting properties is disclosed. JP-A-57-59970 (Patent Document 2) discloses an oil-soluble dye comprising an oil-soluble dye, a water-soluble organic solvent having a dielectric constant of 8 or more and a boiling point of 80 to 300 ° C. at normal pressure, and water. An ink in which an oil-soluble dye is solubilized in water by using a special solvent that dissolves in water and water resistance is disclosed. Many inks in which a colorant is a pigment that does not dissolve in water are also disclosed.
Japanese Patent Laid-Open No. 10-306243 JP-A-57-59970

  Conventionally, water-based ballpoint pen inks that use a water-soluble dye as a colorant have the disadvantage of being inferior in the water resistance of handwriting. However, as in the invention described in Patent Document 1, the water repellent property is used to impart water resistance to the handwriting. Addition of water-based fluorine compounds reduces the surface tension of the ink, so that the ink can easily penetrate the paper, causing blotting and back-throwing of the ink, and ink leakage from the pen tip. .

  In addition, as in the invention described in Patent Document 2, an ink using a water-soluble organic solvent that dissolves an oil-soluble dye and also dissolves in water as a solubilizer is a water-resistant dye because the colorant is an oil-soluble dye. Although oil-soluble dyes are stable, only about 5% or less can be dissolved stably, and as a ballpoint pen ink, the handwriting density is low. In addition, such a solvent has a large penetration into the paper and needs to be added in a large amount for solubilizing the dye, so that the dryness of the handwriting is deteriorated and the paper surface and hands are soiled during writing. A show-through occurs where the ink penetrates to the back of the paper.

  In addition, there are many inks that impart water resistance to the handwriting by using a colorant as a pigment. However, if the colorant is a pigment, the color of the handwriting is inferior. If a large amount of pigment is added, the ink viscosity increases and the writing feeling is increased. There is a problem that the writing density is lower than that of the aqueous dye ink.

  An object of the present invention is to provide a water-based ink composition for ballpoint pens that uses an oil-soluble dye as a colorant, has excellent water resistance of handwriting, has fast handwriting drying, and has excellent writing feeling.

  The present invention relates to a water-based ink composition for ballpoint pens comprising at least an oil-soluble dye as a colorant, an alkali-soluble styrene-acrylic acid resin, a basic substance for dissolving the alkali-soluble styrene-acrylic acid resin in water, and water. Is the gist.

  By using an alkali-soluble styrene-acrylic acid resin and a basic substance that dissolves this in water, an oil-soluble dye that does not dissolve in water alone can be solubilized in water at a sufficient concentration. While maintaining the vivid color developability of the ink, it can form dark and vivid handwriting without problems such as high viscosity and dispersion stability of the ink. It also has the water resistance of handwriting, and it is not necessary to add a large amount of water-soluble organic solvent. Therefore, the handwriting can be dried quickly and the viscosity can be adjusted to a low level, so the writing quality is light.

  As the alkali-soluble styrene-acrylic acid resin used in the present invention, styrene having a molecular weight of 20000 or less or a mixture of α-methylstyrene and styrene and an oligomer obtained by bulk polymerization of acrylic acid can be used. These may be those obtained by neutralizing a resin solid provided with a basic substance and dissolving it in water, or those provided by neutralizing and dissolving in advance with various basic substance aqueous solutions. The molecular weight here is a weight average molecular weight (Mw). When the molecular weight exceeds 20000, the alkali solubility is lost and insolubilized, so that it is usually provided in the form of a styrene-acrylic acid emulsion that is not neutralized. However, the emulsion type does not have the ability to solubilize oily dyes in water. Further, the solid content acid value of the alkali-soluble styrene-acrylic acid resin is preferably 180 or more. If the acid value is 60 or less, it does not dissolve in water even if it is neutralized with a basic substance, and therefore a solvent such as alcohol is necessary. If the acid value is greater than 60 but less than 180, the oil-soluble dye has very high solubilization performance. A small and sufficient amount of the dye cannot be solubilized or the dye once dissolved may easily precipitate over time. Basic substances that can be used to neutralize the alkali-soluble styrene-acrylic resin and dissolve it in water include alkali metal hydroxide compounds such as sodium hydroxide and potassium hydroxide, monoethanolamine, diethanolamine, and triethanolamine. Any basic substance that is soluble in water, such as organic basic compounds such as aminomethylpropanol and ammonia, can be used without particular limitation, and a plurality of these may be used in combination. Those neutralized with a high-boiling liquid amine may have slow handwriting drying and poor water resistance. When neutralized with ammonia, the resin film after handwriting drying is insolubilized in water, and thus the water resistance of the handwriting is further improved, which is particularly preferable.

  Specific examples that can be used as the alkali-neutralized aqueous solution of alkali-soluble styrene-acrylic acid resin and alkali-soluble styrene-acrylic acid resin used in the present invention include John, manufactured by BASF Japan Ltd., as alkali-soluble styrene-acrylic acid resin. Examples include Krill 67, 678, 586, 611, 680, 682, 683, and 690, which can be used after neutralizing and dissolving with an aqueous basic substance solution. As alkali neutralized aqueous solution of alkali-soluble styrene-acrylic acid resin, BASF Japan Co., Ltd. Jongkrill 52J, 57J, 60J, PDX-6650, 61J, 62J, 63J, 70J, HPD -96J, HPD-96MEAJ, PDX-6137A, 354J, 6610, etc. The amount of resin used can be 5% to 45% by weight based on the total amount of ink. From the solubility of the dye, it is preferably about 8% to 25% by weight, and a plurality of these may be used in combination.

In order to suppress bleeding and leakage from the pen tip as a ballpoint pen ink, and to make the ink lighter in writing, it is usual to impart shear thinning viscosity to the ink, but the oil-soluble dye is an alkali-soluble styrene-acrylic acid resin. Since there are a large amount of hydrophobic substances in the ink system that do not normally dissolve when solubilized with an alkali neutralized aqueous solution of water, general water-soluble thickeners such as xanthan gum, succinoglucan, welan gum, lambzan gum, guar gum, etc. Polysaccharides and their derivatives, polyacrylic acid, acrylic acid-alkyl methacrylate copolymers, celluloses such as hydroxypropylcellulose, carboxymethylcellulose, sodium polyalginate, polyethylene oxide, etc. do not thicken or precipitate. The ink viscosity cannot be adjusted. . However, it has been found that a special acrylic thickener having a hydrophobic group introduced in its structure can impart shear thinning. This special acrylic thickener is an alkali-soluble emulsion polymer that is a copolymer of the following monomers (A), (B), and (C).
(A) Acrylic acid and / or methacrylic acid.
(B) 1 type, or 2 or more types chosen from acrylic acid alkylester and methacrylic acid alkylester.
(C) One or more selected from esters of polyoxyalkylene monoalkyl ether and acrylic acid and esters of polyoxyalkylene monoalkyl ether and methacrylic acid.
These are alkali-soluble emulsion polymers, which are low-viscosity polymer emulsions that are cloudy to slightly cloudy. However, when an oil-soluble dye is added to an aqueous ink solubilized with an alkali-neutralized aqueous solution of an alkali-soluble styrene-acrylic acid resin, it is alkali-soluble The basic substance used for neutralizing the styrene-acrylic acid resin can increase the viscosity transparently and impart shear thinning viscosity to the entire ink. Both acrylate / ceteth-20 methacrylate copolymer and acrylate / steareless-50 acrylate Polymers, acrylate / steareth-20 methacrylate copolymers, acrylate / Beheneth-25 methacrylate copolymers, etc. are exemplified, and commercially available products such as Aculin 22 and Aculin 28 (Rohm and Haas Japan Co., Ltd.) are suitable. Can be used for The amount used can be about 0.01 wt% or more and 5 wt%, preferably 0.1 wt% or more and 2 wt% or less. If the added amount is small, the ink leaks from the pen tip, and if the added amount is too large, the ink viscosity at the time of writing becomes high and the writing quality becomes poor. These may be used alone or in combination.
Common water-soluble thickeners are thickened by sufficiently spreading hydrophilic groups in the polymer into water, but the presence of substances with hydrophobic groups such as this ink inhibits the spread of hydrophilic groups. The alkali-soluble emulsion polymer has an alkyl group having about 10 to 22 carbon atoms introduced as a hydrophobic group in the structure, and this hydrophobic property is not included in oil-soluble dyes. It is thought that the shearing viscosity can be stably imparted because the functional group is oriented and the hydrophilic group can sufficiently swell and dissolve on the water side.

As the colorant, oil-soluble dyes conventionally used in oil-based ballpoint pen inks can be used without limitation. As the dye, acid dyes, basic dyes, metal complex dyes, salt-forming dyes, azine dyes, anthraquinone dyes, phthalocyanine dyes, triphenylmethane dyes and the like can be used. Specifically, Bali First Yellow # 3104, Bali First Yellow # 3105, Bali First Yellow # 1105, Bali First Yellow AUM, Orient Spirit Black AB, Bali First Black # 3804, Bali First Black # 3806, Bali First Black # 1802, Bali First Black # 1805, Bali First Yellow # 1109, Bali First Orange # 2210, Bali First Red # 1320, Bali First Blue # 1605, Bali First Violet # 1701, Orient Oil Scarlet # 3 8. Nigrosine Base EX-BP (Oil-based dye manufactured by Orient Chemical Co., Ltd.), Spiron Black GMH Special, Spiron Yellow C-2GH, Spiron Red C-GH, Spiron Red C-BH, Spiron Blue BPNH, Spiro Blue C-RH, Spiro Violet C-RH, S. P. T.A. Orange 6, S. P. T.A. Blue-111 (oil dye manufactured by Hodogaya Chemical Co., Ltd.), Rhodamine B base (CI. 45170B, oil dye manufactured by Sumitomo Chemical Co., Ltd.), Victoria Blue F4R, Nigrosine Base LK (Germany) Country, manufactured by BASF), methyl violet 2B base (manufactured by National Annline Div.), Etc. can be used, but salt forming dyes are particularly preferable because they are most stably dissolved in alkali-soluble styrene-acrylic resin alkali neutralized aqueous solutions. . The amount used can be from about 3% by weight to about 30% by weight, and preferably from 10% by weight to 20% by weight for sufficient handwriting concentration and dye dissolution stability. If it is 10% by weight or less, the concentration of the handwriting may not be sufficient. If it exceeds 20% by weight, the dye tends to precipitate over time even if it is once solubilized.
These may be used alone or in combination.

  Water is used as an essential component of the ink solubilized with the oil-soluble dye. This water is preferably ion-exchanged water for the dissolution and stabilization of dyes and resins. In addition to these essential ingredients, conventionally known dye dissolution accelerators, antioxidants, UV absorbers, antiseptics, rust preventives, antifoaming agents, pH adjusters, ball seat wear prevention and brushing improvement Therefore, the lubricant for use can be used as needed.

Conventionally known water-soluble organic solvents and polyhydric alcohols can be blended to prevent the ballpoint pen tip from drying and freeze, but it is desirable that the amount added does not adversely affect the dryness of the handwriting. Is a water-soluble organic solvent such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycerin, diglycerin, triglycerin, tetraglycerin Polyhydric alcohols such as sorbitol, maltitol and fructose can be used, and the blending amount is preferably 30% by weight or less.
These may be used alone or in combination.

  The method for preparing an oil-soluble dye aqueous ink in which an oil-soluble dye is dissolved in water is not particularly limited, and an alkali neutralized composition of water and a styrene-acrylic resin and an oil-soluble dye are mixed with a stirrer, homomixer, or homogenizer. For example, it can be prepared by stirring at an appropriate temperature. Further, filtration and centrifugation can be performed to remove impurities and insoluble matters.

Example 1
Spiron violet C-RH (dye: Hodogaya Chemical Co., Ltd.) 3.0% by weight
Spiro Yellow C-GNH (dye: Hodogaya Chemical Co., Ltd.) 2.0% by weight
Joncrill 683 neutralized aqueous solution 23.0% by weight
Ethylene glycol 5.0% by weight
Ion-exchanged water 67.0% by weight
Joncryl 683 resin (styrene-acrylic acid resin: acid value 160, molecular weight 8000, manufactured by BASF Japan Ltd.) is previously neutralized with KOH to prepare a 30% solids aqueous solution.
The neutralized aqueous solution of Joncryl 683, ethylene glycol, and ion-exchanged water were stirred with a magnetic stirrer for 10 minutes, the dye was added, stirred at 50 ° C. for 2 hours, and then cooled to prepare a black ink.

Example 2
Spiro violet C-RH (previously described) 6.0 wt%
Spiron Yellow C-GNH (mentioned above) 4.0% by weight
Joncrill 62J 26.5% by weight
Ethylene glycol 5.0% by weight
Ion-exchanged water 58.5% by weight
The above-mentioned Joncryl 62J (neutralized aqueous solution of styrene-acrylic acid resin with ammonia, acid value 200, molecular weight 12000, resin solid content 34%, manufactured by BASF Japan Ltd.), ethylene glycol, ion-exchanged water with a magnetic stirrer 50 The mixture was heated to 0 ° C., stirred for 5 minutes, charged with a dye, stirred at 50 ° C. for 3 hours and then cooled to prepare a black ink.

Example 3
Spiron Violet C-RH (mentioned above) 12.0% by weight
Spiron Blue C-RH (dye, manufactured by Hodogaya Chemical Co., Ltd.) 3.0% by weight
Jonkrill 52J 26.5 wt%
Ion-exchanged water 43.3% by weight
The above-mentioned Joncryl 52J (neutralized aqueous solution of styrene-acrylic resin with ammonia, acid value 238, molecular weight 1700, resin solid content 60%, manufactured by BASF Japan Ltd.), ion-exchanged water was heated to 50 ° C. with a three-one motor. The mixture was stirred for 5 minutes, the dye was added, stirred at 50 ° C. for 4 hours, and then cooled to prepare a blue ink.

Example 4
Spiro Yellow C-GNH (mentioned above) 5.0% by weight
Spiron Red C-GH (dye, manufactured by Hodogaya Chemical Co., Ltd.) 6.6% by weight
Spiron Red C-BH (dye, manufactured by Hodogaya Chemical Co., Ltd.) 8.4% by weight
30.0% by weight of neutralized aqueous solution of Joncryl 682
Ion exchange water 50.0% by weight
Joncrill 682 resin (styrene-acrylic acid resin, acid value 238, molecular weight 1700, manufactured by BASF Japan Ltd.) is previously neutralized with KOH and ion-exchanged water to prepare a 60% solids aqueous solution.
This neutralized aqueous solution of Joncryl 682 and ion-exchanged water were stirred with a three-one motor at 50 ° C. for 5 minutes, a dye was added, and the mixture was stirred at 50 ° C. for 4 hours and then cooled to prepare a red ink.

Example 5
Spiro Yellow C-GNH (described above) 6.3% by weight
Spiron Red C-GH (previously described) 8.2% by weight
Spiron Red C-BH (mentioned above) 10.5% by weight
Jonkrill 52J (mentioned above) 50.0% by weight
Ion-exchanged water 25.0% by weight
The above-mentioned Jonkrill 52J and ion exchange water were heated to 50 ° C. with a three-one motor, stirred for 5 minutes, charged with a dye, stirred for 4 hours at 50 ° C., and then cooled to prepare a red ink.

Example 6
Spiro violet C-RH (previously described) 7.2% by weight
Spiro Yellow C-GNH (mentioned above) 4.8% by weight
Jonkrill HPD-96J 59.0 wt%
Ion-exchanged water 28.0% by weight
Aculine 22 (shear thinning agent, manufactured by Rohm and Haas Japan)
1.0% by weight
Joncryl HPD-96J (neutralized aqueous solution of styrene-acrylic acid resin with ammonia, acid value 270, molecular weight 16500, resin solid content 34%, manufactured by BASF Japan Ltd.), ion-exchanged water for 10 minutes with a magnetic stirrer Stirring and adding a dye, stirring at 50 ° C. for 2 hours, cooling and stirring, added aculine 22 and stirring for 1 hour to prepare a black ink.

Example 7
Spiro violet C-RH (previously described) 9.6% by weight
Spiron Blue C-RH (described above) 2.4% by weight
Jonkrill HPD-96MEAJ 59.7% by weight
Ion-exchanged water 27.3% by weight
Aculine 28 (shear thinning agent: manufactured by Rohm and Haas Japan)
1.0% by weight
Joncrill HPD-96MEAJ (neutralized aqueous solution with styrene-acrylic acid resin monoethanolamine, acid value 270, molecular weight 16500, resin solid content 33.5%, manufactured by BASF Japan Ltd.), ion-exchanged water as magnetic stirrer The mixture was stirred for 10 minutes, the dye was added, and the mixture was stirred at 50 ° C. for 2 hours.

Example 8
In Example 7, Aculin 22 was replaced with 5.0% by weight of 5% aqueous solution of Kelzan AR (Xanthan Gum, manufactured by Sanki Co., Ltd.), and ion exchanged water was changed to 24.0% by weight. A black ink was made.

Example 9
Spiro violet C-RH (previously described) 9.6% by weight
Spiron Blue C-RH (described above) 2.4% by weight
Jonkrill 52J (mentioned above) 30.0% by weight
Ion exchange water 43.0% by weight
Pemulen TR-1 (acrylic thickener, manufactured by Nikko Chemicals) 0.3% by weight
Joncrill 52J, ion-exchanged water was stirred with a magnetic stirrer for 10 minutes, a dye was added, stirred at 50 ° C. for 2 hours, then cooled and stirred with Pemulene TR-1 and stirred for 2 hours to give blue ink. Created.

Comparative Example 1
Spiro violet C-RH (mentioned above) 3.0% by weight
Spiro Yellow C-GNH (mentioned above) 2.0% by weight
N-methyl-2-pyrrolidone 35.0% by weight
Ethylene glycol 5.0% by weight
Ion exchange water 55.0% by weight
Dye is added to the above N-methyl-2-pyrrolidone and ethylene glycol, and the mixture is stirred with a magnetic stirrer at 50 ° C. for 1 hour, stirred with a magnetic stirrer for 45 minutes while adding ion-exchanged water little by little, and then cooled to black ink. It was created.

Comparative Example 2
In Example 2, Joncryl PDX7630A (Styrene-acrylic acid resin emulsion, acid value 200, molecular weight of about 20000, solid content 32% emulsion, BASF Japan ( The product was the same as in Example 2 except that the ion exchanged water was changed to 57.0% by weight, but the dye did not dissolve at all and settled and solidified at the bottom of the container with a stirrer. Stirring was impossible and ink could not be created.

Comparative Example 3
A 40% aqueous solution of Jurimer AC-10NP (sodium polyacrylate resin, molecular weight 7000, manufactured by Nippon Pure Chemical Co., Ltd.) is prepared in advance.
In Example 2, 40% aqueous solution of Jurimer AC-10NP, which is a sodium acrylate resin having no styrene monomer, was replaced with 22.5% by weight in place of Joncrill 62J, and ion exchanged water was changed to 67.5% by weight. Produced a black ink in the same manner as in Example 2, but became an opaque ink in which a large amount of dye powder was dispersed in the ink.

Comparative Example 4
Water Pink # 2 (CI ACID RED92, manufactured by Orient Chemical Industry Co., Ltd.)
5.0% by weight
Water Yellow # 6C (CI ACID YELLOW23, manufactured by Orient Chemical Industry Co., Ltd.) 1.0% by weight
Kelzan AR (mentioned above) 0.5% by weight
Ethylene glycol 25.0% by weight
Glycerin 10.0% by weight
Sarcosinate OH (N-oleoyl sarcosine, surfactant, Nikko Chemicals Co., Ltd.)
Manufactured) 1.0% by weight
Sodium hydroxide 0.1% by weight
Ion-exchanged water 57.4% by weight
The above Kelzan AR and water are stirred for 30 minutes with a laboratory mixer and uniformly dissolved to prepare a Kelzan AR aqueous solution. The remaining components are added thereto, and the mixture is further stirred for 2 hours to obtain a water-based red ink. Obtained.

Preparation of test sample Cap-type ballpoint pen (cap) having a ballpoint pen tip holding each ballpoint ink composition obtained in Examples 1 to 5 and Comparative Examples 1 and 3 and holding a carbide ball having a diameter of 0.5 mm 1.7 g of the ink containing tube of the formula Energel, product code BLN55, manufactured by Pentel Co., Ltd. was filled into a test ballpoint pen sample.
Each of the ballpoint pen ink compositions obtained in Examples 6 to 9 and Comparative Example 4 is a knock type ballpoint pen having a ballpoint pen tip holding a superhard ball having a diameter of 0.5 mm (a knock type energ, product code BLN75). , Manufactured by Pentel Co., Ltd.) was filled with 1.7 g of ink containing tubes, and used as test ballpoint pen samples.

The following tests were performed on each example and comparative example. The results are shown in Table 1.
Confirmation of dye solubility A small amount of each of the ink compositions for ballpoint pens obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was taken on a slide glass and visually observed for insoluble matters at a magnification of 400 times that of an optical microscope.
○: Insoluble matter is not confirmed in the field of view △: Slightly insoluble matter is present ×: A large amount of insoluble matter is present, and observation under transmitted light is difficult

Confirmation of dye solubility after aging of heat cycle 10 g of each of the ink compositions for ballpoint pens and the blended compositions obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was used for a screw cap glass bottle with a lid (19 × 70 mm, Nichidenka) After 5 cycles of heat cycle in which it was placed at -5 ° C for 24 hours and then placed at 50 ° C for 24 hours, left for 1 day at room temperature and lightly stirred A small amount was taken on a slide glass and the insoluble matter was visually observed at a magnification of 400 times that of an optical microscope.
○: Insoluble matter is not confirmed in the field of view △: Slightly insoluble matter is present ×: A large amount of insoluble matter is present, and observation under transmitted light is difficult

Handwriting dryness test Using the above test ballpoint pen sample, write five consecutive circles with a diameter of about 2 cm by hand on JIS P3201 writing paper A at a writing angle of 70 °, a writing load of 100 g, and a writing speed of 7 cm / sec. When a filter paper (No. 2 manufactured by Advantech) with a weight of 500 g was placed on the handwriting while changing the time after writing, the time until ink was not applied to the filter paper was determined. An ink having a short time is an ink having excellent handwriting dryness.

Handwriting water resistance test Using the above test ballpoint pen sample, handwritten 15 consecutive circles of about 2 cm in diameter on JIS P3201 writing paper A twice, left for 1 hour, and then immersed in ion-exchanged water for 1 hour To do. Then, it took out from water and determined the degree of fading with a gray scale (JIS L-0804). The gray scale is from 1 to 5, and the larger the number, the smaller the density difference between the handwriting before and after the test, indicating water resistance.

Confirmation of show-through of handwriting Using the above test ball-point pen sample, write 15 consecutive circles with a diameter of about 2cm by hand on JIS P3201 writing paper A twice in an environment of 30 ° C and 60% RH for one day. After standing, the back side of the writing was observed.
○: No ink show-through △: Slight show-through x: Clear show-through

Initial Viscosity Measurement Using a VAR 100 type rheometer (Jusco International Co., Ltd.), a 1 °, 20 mm cone plate was used, and the ink composition viscosities at temperatures of 25 ° C. and shear rates of 5 s ⁻¹ and 500 s ⁻¹ were measured.

Quick leak test after humidification 10 ballpoint pen test samples are fixed with the ball holder protruding so that nothing touches the tip, and writing paper A is placed underneath and left in a constant temperature bath at 50 ° C for 1 week. After that, ink oozed out and leaked into the ball holder.
○: No leakage: No ink leakage or bleeding from the ball holder △: Leaking: There is ink bleeding from the ball holder, but no dropping occurs.
×: Leakage large: A dropout occurred in the lower writing paper.

  As described above in detail, the water-based ink composition for ballpoint pens of the present invention is a water-based ink for ballpoint pens that has excellent water resistance of handwriting, quick handwriting drying, and excellent writing feeling.

Claims (3)

An aqueous ink composition comprising at least an oil-soluble dye, an alkali-soluble styrene-acrylic acid resin, a basic substance for dissolving the alkali-soluble styrene-acrylic acid resin in water, and water. The use amount of the oil-soluble dye as the colorant is 10% by weight or more and 20% by weight or less, and the alkali-soluble styrene-acrylic acid resin having a solid content acid value of 180 or more is 8% by weight or more and 25% by resin solid content. The aqueous ink composition for ballpoint pens according to claim 1, wherein the basic substance contained in an amount of not more than wt% and dissolved in water is ammonia. 2. The alkali-soluble emulsion polymer, which is a copolymer obtained by copolymerizing the following monomers (A), (B), and (C) as a shear thinning agent: 2. A water-based ink composition for ballpoint pens according to 2.
(A) Acrylic acid and / or methacrylic acid.
(B) 1 type, or 2 or more types chosen from acrylic acid alkylester and methacrylic acid alkylester.
(C) One or more selected from esters of polyoxyalkylene monoalkyl ether and acrylic acid and esters of polyoxyalkylene monoalkyl ether and methacrylic acid.