JPH06192611A - Water-based pigment ink composition for writing utensil - Google Patents

Abstract

PURPOSE:To obtain a compsn. which is excellent in dispersion stability an hiding power and does not require operations such as stirring before the use by fixing fine titanium oxide particles on the surfaces of resin particles to form composite particles with specified particle sizes. CONSTITUTION:The compsn. contains, as a coloring matter, composite particle having a mean particle size of 0.2-2mum and obtd. by fixing fine titanium oxide particles having a mean particle size of 0.1mum or lower on the surfaces of resin particles. The resin particle reduces the apparent density of the oxide particles, improving the dispersion stability of the latter particles, and increases the apparent particle size of the latter, improving the whiteness and hiding power of the latter. The composite particles are obtd. by mixing the resin and the oxide particles and fixing the oxide particles on the surfaces of the resin particles by causing the oxide particles to be adsorbed by the surface or to be forced into the resin particles, e.g. by mixing and grinding with an automatic mortar, a jet mill, etc., and/or giving a mechanical impact with a hammer mill, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pigment ink for writing instruments, and more particularly to a pigment ink composition which has excellent dispersion stability and hiding power and does not require a work such as stirring before use.

[0002]

2. Description of the Related Art Conventionally, inks containing various dyes and pigments as coloring materials have been used as inks for writing instruments. In general, pigment inks are superior to dye inks in handwriting fastness and hiding power. In particular, when the object to be written is black or dark colored paper, it is almost impossible to use dye ink, so pigment ink is used. As a pigment ink used for such black or dark color paper, a white inorganic pigment, particularly a titanium oxide pigment having a particle diameter of 0.2 to 0.5 μm, is known alone or in combination with other pigments.

[0003]

The particle size is 0.2 to 0.5.
The μm titanium oxide pigment is an ideal white pigment that is superior in whiteness, hiding power, coloring power, heat resistance, light resistance, and chemical resistance compared to other white inorganic pigments, but it has a large specific gravity. Dispersion stability is poor, and sedimentation and separation of pigments occur, which causes problems such as a difference in the density of handwriting and clogging at the pen tip. Therefore, in a writing instrument using the above titanium oxide pigment, redispersion work of the pigment by stirring is indispensable, so the structure of the writing instrument becomes complicated and expensive, and the writing instrument must be shaken before use to redisperse the pigment. Have the hassle of having to do.

Therefore, in recent years, a number of ink compositions have been proposed in which resin particles having various particle diameters, shapes and materials are used as coloring agents instead of titanium oxide pigments. However, these do not have sufficient hiding power and whiteness.

An object of the present invention is to provide a pigment ink composition having excellent dispersion stability and sufficient hiding power.

[0006]

According to the present invention, fine particles of titanium oxide having an average particle size of 0.1 μm or less are adhered to the surface of resin particles as a coloring material, and the average particle size is 0.2 to 2 μm.
The gist is an aqueous pigment ink composition for a writing instrument, which contains at least the composite particles of

The present invention will be described in more detail. The composite particles are used as a coloring material, and have fine particle titanium oxide fixed to the surface of the resin particles as described later. The average particle size of the composite particles needs to be 0.2 to 2 μm. This is because when the average particle size of the composite particles is less than 0.2 μm, the composite particles do not appear white, and when the average particle size is more than 2 μm, the whiteness is lowered and the composite particles do not have sufficient hiding power. . Further, when the average particle diameter is larger than 2 μm, even when it is used as an ink for a writing instrument, it becomes difficult to eject from the pen tip of the writing instrument, and problems such as clogging easily occur. The amount of the composite particles used is preferably 10 to 70% by weight with respect to the total amount of the ink. The average particle size of the composite particles is measured using a scanning electron micrograph.

The fine particle titanium oxide has an average particle diameter of 0.1.
Titanium oxide having a particle size of not more than μm. This is because titanium oxide having an average particle diameter of more than 0.1 μm lowers the whiteness of the composite particles. As such fine particle titanium oxide, MT-100S (average particle diameter 0.015 μm),
MT-150W (average particle diameter 0.015 μm), MT-
500B (average particle size 0.035 μm), MT-500
SA (average particle size 0.035 μm), MT-500HD
(Average particle size 00.3 μm), MT-600B (average particle size 0.05 μm), MT-600SA (average particle size 0
0.5 μm) (above, manufactured by Teika Co., Ltd.) and the like. In particular, fine particle titanium oxide having a hydrophilic surface by a surface treatment with silica, alumina, zirconia or the like is preferable. The average particle size of the fine particle titanium oxide is calculated from the specific surface area, assuming that the particles of the fine particle titanium oxide are spherical.

The resin particles are used for the purpose of reducing the apparent specific gravity of the composite particles to improve the dispersion stability and increasing the apparent particle size of the fine particle titanium oxide to improve the whiteness and the hiding power. To do. Particles of polyethylene, polypropylene, polymethylmethacrylate, polystyrene, nylon, silicone resin, urea-formaldehyde resin, etc. can be used. An example of a commercially available product is MP-
1000, MP-1450, MP-1401, MP-1
451 (above, polymethylmethacrylate resin, manufactured by Soken Chemical Co., Ltd.). The particle diameter is preferably about 10 times the particle diameter of the fine titanium oxide particles to be fixed, and the particle diameter of 0.1 to 1 μm can be used.

The composite particles are obtained by mixing fine particle titanium oxide and resin particles, and mixing the particles with an automatic mortar, ball mill, jet mill, atomizer, etc., grinding and / or hammer mill, hybridizer (trade name, ( It can be obtained by adhering fine particles of titanium oxide to the surface of the resin particles, or by sticking them to the surface of the resin particles so as to fix the particles, by applying a mechanical impact force with Nara Machinery Co., Ltd.).

In addition, known materials used for water-based ink can be used as necessary. As the aqueous medium, one or a mixture of two or more of water-soluble organic solvents such as alcohols, glycols, cellosolves and carbitols, which do not dissolve the resin particles used, and water can be used. The amount used is preferably 20 to 95% by weight with respect to the total amount of ink.

As the viscosity modifier of the ink, synthetic (co) polymers such as polyvinylpyrrolidone, polyethylene oxide, salts of polyacrylic acid, methyl vinyl ether maleic anhydride copolymer, and celluloses such as carboxymethyl cellulose and hydroxypropyl cellulose are used. Systematic thickeners, hydrogenated castor oil, gelling agents such as polycarboxylic acid amides, plant-based thickeners such as guar gum and gum arabic, and water-soluble polymers such as animal-based thickeners such as gelatin and shellac. All can be used, and these can be used alone or in combination of two or more.

In addition to the above components, conventionally known organic pigments, inorganic pigments, extender pigments, etc. can be used for color matching. Other surfactants, dispersants, preservatives, antifungal agents, lubricants and the like may be appropriately selected.

Various methods can be employed for producing the water-based pigment ink composition of the present invention. For example, the above-mentioned components are blended and the resulting mixture is blended with a ball mill, homomixer, sand grinder, speed line mill, roll mill or the like. It can be easily obtained by mixing and dispersing with a disperser.

[0015]

The fine particle titanium oxide having an average particle size of 0.1 μm or less used in the composite particles of the present invention is different from the commonly used titanium oxide pigment having a particle size of 0.2 to 0.5 μm. Since it has a large light transmittance in the visible light portion and therefore has a small hiding power and coloring power, it was not used as a white pigment.

However, since the fine titanium oxide particles are fixed on the surface of the resin particles to form composite particles having a predetermined average particle diameter, the composite particles have an optically predetermined average particle diameter. It is considered as one titanium oxide particle that has. In addition, the composite particles have sufficient whiteness and hiding power because they diffuse light at the interface between the resin particle surface and the fine titanium oxide particles, and the apparent specific gravity is smaller than that of the titanium oxide pigment. Therefore, the water-based pigment ink composition containing the composite particles as a colorant is an ink having extremely excellent dispersion stability and sufficient hiding power.

[0017]

【Example】

(Production Example of Composite Particles) Production Example 1 MP-1000 (polymethylmethacrylate resin, average particle size 0.4 μm, manufactured by Soken Chemical Industry Co., Ltd.) 45 parts by weight MT-500SA (rutile titanium dioxide, average particle size) 0.035 μm, manufactured by Teika Co., Ltd. 55 parts by weight The above components were mixed in an automatic mortar for 2 hours, and composite particles (A) in which titanium oxide was adsorbed on resin particles (average particle size: 0.
47 μm) was obtained.

Production Example 2 MP-1450 (polymethylmethacrylate resin, average particle size 0.25 μm, manufactured by Soken Chemical Industry Co., Ltd.) 60 parts by weight MT-150W (rutile titanium dioxide, average particle size 0.015 μm, taker) 40 parts by weight of the above components were treated with a hybridizer for 5 minutes to obtain composite particles (B) (average particle diameter 0.28 μm) in which resin particles were impregnated with titanium oxide.

Production Example 3 MP-1401 (polymethylmethacrylate resin, average particle size 0.8 μm, manufactured by Soken Chemical Industry Co., Ltd.) 55 parts by weight MT-150W (rutile titanium dioxide, average particle size 0.05 μm, taker) 45 parts by weight The above components were mixed in an automatic mortar for 30 minutes and then treated with a hybridizer for 3 minutes to obtain composite particles (C) (average particle diameter 0.9 μm).

Production Example 4 Nipol U2000 series (crosslinked polystyrene resin, average particle size 2.0 μm, manufactured by Nippon Zeon Co., Ltd.) 70 parts by weight JR-805 (rutile titanium dioxide, average particle size 0.30 μm, Teika (stock) )) 30 parts by weight The above components were mixed in an automatic mortar for 30 minutes and then treated with a hybridizer for 3 minutes to obtain composite particles (D) (average particle diameter 2.6 μm).

Production Example 5 MP-1451 (polymethylmethacrylate resin, average particle size 0.15 μm, manufactured by Soken Chemical Industry Co., Ltd.) 40 parts by weight MT-150W (rutile titanium dioxide, average particle size 0.015 μm, taker) 60 parts by weight of the above components were mixed in an automatic mortar for 30 minutes and then treated with a hybridizer for 3 minutes to obtain composite particles (E) (average particle diameter 0.18 μm).

Example 1 Composite particles (A) 45 parts by weight Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight The above components were mixed and mixed in a ball mill. Dispersion treatment was carried out for 24 hours to obtain a white ink composition.

Example 2 Composite particles (B) 45 parts by weight Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight Same as Example 1 for each of the above components. Then, a white ink composition was obtained.

Example 3 Composite particles (C) 45 parts by weight Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight Same as Example 1 for each of the above components. Then, a white ink composition was obtained.

Comparative Example 1 JR-800 (rutile type titanium dioxide, average particle diameter 0.27 μm, manufactured by Teika Co., Ltd.) 45 parts by weight Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight In the same manner as in Example 1 for each of the above components, a white ink composition was obtained.

Comparative Example 2 MP-1000 (polymethylmethacrylate resin, average particle size 0.4 μm, manufactured by Soken Chemical Industry Co., Ltd.) 45 parts by weight Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight In the same manner as in Example 1 for each of the above components, a white ink composition was obtained.

Comparative Example 3 45 parts by weight of composite particles (D) Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight Same as Example 1 for each of the above components. To obtain a white ink composition.

Comparative Example 4 45 parts by weight of composite particles (E) Ammonium salt of styrene-acrylic acid copolymer 5 parts by weight Glycerin 10 parts by weight Isopropyl alcohol 5 parts by weight Water 35 parts by weight Same as Example 1 for each of the above components. To obtain a white ink composition.

Using the white ink compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 4, the sedimentation test and the spatula density test were carried out. The results are shown in Table 1.

Sedimentation test: The ink obtained was 1 cm in diameter,
It was put in a settling tube having a length of 30 cm and left at 50 ° C. for 3 months, and the settling state was visually observed. ◯: No sedimentation x: Sedimentation Spatling density test: The obtained ink was applied to black drawing paper (New Color 418, manufactured by Lintec Co., Ltd.) with a spatula made of silicone rubber, and the whiteness and the density were visually determined. . ◯: The whiteness is high and the base is completely hidden. ×: Low whiteness and the effect of the base appears

[0031]

[Table 1]

[0032]

As described above, the aqueous pigment ink composition for a writing instrument of the present invention can provide extremely excellent dispersion stability, sufficient hiding power and whiteness.

Claims (1)

[Claims] 1. A fine particle titanium oxide having an average particle diameter of 0.1 μm or less is adhered to the surface of resin particles as a coloring material.
A water-based pigment ink composition for a writing instrument, which comprises at least composite particles having an average particle diameter of 0.2 to 2 μm.