JPH03250074A - Water-based ink composition for ball-point pen - Google Patents

Abstract

PURPOSE:To prevent drying of an uncapped penpoint as far as possible and improve the ink discharge in starting writing by compounding a pigment, a guar gum deriv., a water-sol. org. solvent, water, and sorbitan and specifying the viscosity. CONSTITUTION:The title compsn. comprises a pigment (e.g. a carbon black), 0.2-3.0wt.% guar gum deriv. (e.g. hydroxypropylated guar gum), a water-sol. org. solvent (e.g. ethylene glycol); 0.2-2.0wt.% sorbitan, water, and a dispersant, freeze preventive, antiseptic agent, lubricant, etc., as required.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a water-based ballpoint pen that ensures better ink ejection than the first stroke by preventing drying at the pen tip as much as possible when the cap is off. The present invention relates to an ink composition.

(Prior art) Conventional water-based ink for ballpoint pens consists of pigments, water-soluble organic solvents, and water, and its viscosity varies from 1 to several cps (at 25°C) and 50 to 50 cps depending on the structure of the ballpoint pen used.
-2000 cps (25°C) is known. 1 to several cps (25°C) is mainly used in structures that use batting as an ink absorber, and
cps (25°C) is mainly used in structures using hollow cylinders as ink storage bodies.

(Problems to be Solved by the Invention) When the cap is off, the ink dries at the pen tip, resulting in noticeable blurring of the first stroke or even an inability to write.

In other words, even if the main solvent of a water-based ballpoint pen is water, the cap protects the pen from drying out, but in the case of a water-based ballpoint pen with a viscosity of 1 to several cps (at 25°C), it will last for several days. With cap-off, there was little change in the physical properties of the ink at the pen tip due to water evaporation, and there were fewer problems with fading from the first stroke. However, the viscosity is 50~2000c
ps (25℃), the evaporation of water at the pen tip when the cap is off causes the ink viscosity at the pen tip to increase significantly due to the influence of the resin used to adjust the viscosity, and as a result, the ink There was a problem that the ejection was poor and smudges were likely to occur on the first stroke, and that it became impossible to write if used for a long time.

In recent years, in order to solve these problems, attempts have been made to increase the drying properties of the pen nib by adding water-soluble high-boiling point organic solvents to water-based inks, but satisfactory results have not been obtained.

(Means for Solving the Problems) The present invention is aimed at solving the above problems, and is directed to a ballpoint pen with a viscosity of 50 to 2000 cps, which is composed of at least a pigment, a gar gum derivative, a water-soluble organic solvent, and water. The gist of the present invention is an aqueous ink composition for a ballpoint pen, characterized in that the aqueous ink composition for a ballpoint pen contains sorbitan.

This will be explained in detail below.

Examples of pigments include organic pigments such as known azo pigments, condensed polyazo pigments, phthalocyanine pigments, quinacridone pigments, indigo pigments, and thioindigo pigments, and inorganic pigments such as carbon black, barium yellow, navy blue, and red iron. , can be used alone or in combination.

Gargum derivatives are used in water-based ink compositions for ballpoint pens.
It is used to adjust the viscosity to 0 to 2000 cps, and can be adjusted without destroying the pigment dispersion system in the ink. Specific examples include hydroxypropylated gar gum,
Examples include carboxymethyl hydroxypropylated guar gum, hydroxypropyltriammonium chloride guar gum, etc., and the amount used is 0% based on the total amount of the ink composition.
It is preferably 2 to 3.0% by weight.

The water-soluble organic solvent has various qualities as a water-based ink composition for a water-based ballpoint pen, namely, prevention of ink drying at the pen tip,
It is used for purposes such as preventing ink from freezing at low temperatures, and specifically contains ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycerin, etc. Glycols, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone triethanolamine, etc. are used alone or in combination.

Sorbitan, which is the essence of the present invention, is used to prevent the nib from drying out. The amount used is preferably 0.2 to 2.0% by weight based on the total amount of the ink composition.

As the dispersant for dispersing the pigment, styrene-maleic acid copolymer-based dispersants and styrene-(meth)acrylic acid copolymer-based dispersants are preferred.

Furthermore, it goes without saying that various other additives such as antifreeze agents, preservatives, antifungal agents, and lubricants may be used as necessary.

Various methods can be used to produce the ink of the present invention, but for example, the above components are blended and mixed using a dispersing machine such as a ball mill, homomixer, sand grinder, speed line mill, or roll mill. Examples include mixing and grinding.

(Effect) The reason why the sorbitan according to the present invention is effective in drying the pen tip is estimated as follows.

In other words, it is presumed that the hydroxyl group in the structure of sorbitan forms hydrogen bonds, which acts as a protective agent for gar gum derivatives, which are dispersants and viscosity modifiers, thereby contributing to dispersion stability and prevention of drying. It is thought that the drying resistance is improved due to the hygroscopic property of sorbitan.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, "r parts" indicates "parts by weight."

Carbon black io, o parts Ammonium salt of styrene-acrylic acid copolymer (dispersant) 5.0 parts Hydroxypropylated gar gum 0.5 parts (viscosity modifier) Ethylene glycol 20.0 parts Glycerin 13 .0 parts sorbitan
1.0 part water
50.5 parts Among the above ingredients, the ingredients other than gar gum and sorbitan were mixed and dispersed in a ball mill for 24 hours, then these two ingredients were added and dispersed again for 3 hours, and coarse particles were removed using a filter, etc. After removal, a black ink of 300 cps (25° C.) was obtained.

In Example 1, everything was done in the same manner as in Example 1 except that sorbitan was removed and water was added, and 290 cps was used.
(25°C) black ink was obtained.

Loss 1 Copper phthalocyanine blue 10.0 parts Ammonium salt of styrene-maleic acid copolymer (dispersant) 5.0 parts Hydroxypropylated gar gum 0.5 parts (viscosity modifier) Ethylene glycol 20.0 parts Glycerin 13. 0 part broxel XL
-20.2 parts (preservative, manufactured by ICI Japan) Sorbitan 1.5 parts water
49.8 parts The above ingredients were prepared in the same manner as in Example 1, and 265 cps (25°C)
A blue ink was obtained.

In Example 2, everything was done in the same manner as in Example 2 except that sorbitan was removed and water was added.
(25°C) blue ink was obtained.

Example l C, 1, Pig+went Red 21
10, 0 parts Ammonium salt of styrene-maleic acid copolymer (dispersant) 5.0 parts Carboxymethylhydroxypropylated gar gum 0.5 parts (viscosity modifier) Sorbitan 1.0 parts Propylene glycol 20.0 parts Ethylene glycol Monoethyl ether 10.0 parts Benzotriazole (rust inhibitor) 0.4 parts Water
53.1 parts A red ink of 280 cps (25° C.) was obtained by using the above ingredients in the same manner as in Example 1.

In Example 3, everything was the same as in Example 3 except that sorbitan was removed and water was added accordingly, and 275 cp
s (25°C) was obtained.

Phthalocyanine Green 8.0 parts Ammonium salt of styrene-acrylic acid copolymer (dispersant) 8. o part ethylene glycol 20.0 parts sorbitan
1.0 part Hydroxypropylated gar gum 0.5 part (viscosity modifier) Benzotriazole (rust preventive agent) 0.2 part water
62.3 parts The above ingredients were prepared in the same manner as in Example 1, and 300 cps (2
5°C) green ink was obtained.

Comparison ■± Viscosity 295 cps (25°C) in the same manner as in Example 4 except that sorbitan in Example 4 was removed and water was added in the same amount.
A green ink was obtained.

(Effect of the invention) The ballpoint pen ink compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were applied to a nickel silver ballpoint pen tip (ball material:
Cemented carbide) was directly filled into a transparent ink storage tube consisting of a polypropylene hollow cylinder connected to one end, and each tube was left horizontally at room temperature without a cap, until it could write normally using a writing tester after 7 days. I wrote it down.

Test method: A commercially available self-rotating continuous writing test machine (spiral machine) was used.

Continuous writing was performed at a writing speed of 7 cm/sec, a writing load of 100 g, and a writing angle of 70°, and the distance from the beginning of writing until the writing was completed normally was measured.

The results are shown in Table-1.

Table 1 As is clear from Table 1, the aqueous ink composition for ballpoint pens according to the present invention allows writing with almost no fading even after being filled into a ballpoint pen and left without a cap. That is, the aqueous ink composition for ballpoint pens according to the present invention has excellent effects in that drying of the pen tip can be prevented as much as possible, and problems such as smearing due to drying of the pen tip and, ultimately, inability to write can be solved as much as possible.

Claims (1)

[Claims] A water-based ink composition for a ballpoint pen having a viscosity of 50 to 2000 cps and comprising at least a pigment, a gar gum derivative, a water-soluble organic solvent, and water, characterized in that the water-based ink composition for a ballpoint pen contains sorbitan. Water-based ink composition for ballpoint pens.