JPH0423670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous pigment ink, and more particularly to an aqueous pigment ink having excellent dispersion stability and drying resistance.

Conventionally, water-based pigment inks have excellent water resistance and light resistance, and have been used for various purposes.

However, when used in low viscosity ink for writing instruments, etc., there was a problem that the dispersibility of the pigment was unstable and agglomerated easily, making writing impossible.

Therefore, as a dispersant for dispersing pigments,
Although various surfactants have been used, they have not yet been sufficient. In recent years, emulsions such as acrylic acid copolymers, amines and ammonium salts of acrylic acid copolymers have also been used, but since emulsions dry quickly, they may dry on the nib of a writing instrument, for example, or may not be exposed to solvents. There was a problem that the emulsion was sometimes destroyed.

Furthermore, particularly for ink for writing instruments, it is necessary to prevent drying at the pen tip as much as possible.

As a result of various studies as an agent for improving the dispersibility and drying resistance of the above-mentioned aqueous pigment ink, the present inventors found that the combination of resin acid and acetamide and/or its derivatives improves the dispersibility and drying resistance of the water-based pigment ink. They discovered that it is highly effective and completed the present invention.

That is, the gist of the present invention is an aqueous pigment ink characterized by containing a resin acid and an acetamide and/or a derivative thereof represented by the following general formula.

general formula (In the formula, R ₁ = - (CH ₂ CH ₂ O) nH, R ₂ = - (
_CH2CH2O )mH n=integer of 0 to 50, m ₌ integer of 0 to 50. ) Resin acids have been used in pigment inks for a long time, but this takes advantage of the ability of resin acids to form a film. There was a problem that it became impossible to write or the writing taste was bad.

Therefore, in the present invention, the above-mentioned problems are solved by using resin acid as a dispersant and acetamide and/or its derivatives, which prevent the resin acid from forming a film and have an effect on drying resistance. This is what I did.

The present invention will be explained in detail below.

Examples of resin acids include shellacs such as general shellac, dewaxed shellac, bleached shellac, and bleached shellac, humic acid, and rosin.

Compounds represented by the general formula include acetamide, N-acetylethanolamine, N,N'-dihydroxyethyl acetamide, N-(polyhydroxyethyl)acetamide, N,N'-bis(polyhydroxyethyl)acetamide, etc. Can be mentioned.

All commonly available pigments can be used as pigments; examples include carbon black, phthalocyanine blue (C.
I.74160), Phthalocyanine Green (CI74260),
Hansa Yellow 3G (CI11670), Jisuazo Yellow GR
(CI21100), Permanent Red 4R (CI12335),
Briantocarmine 6B (CI15850), Quinacridone Red (CI46500), etc. can be used, and the amount used is preferably 5 to 20% by weight based on the total amount of the ink.

Incidentally, the type and proportion of the pigment used are selected as appropriate.

As the solvent, not only water but also water-soluble organic solvents such as glycol solvents, glycol ether solvents, glycol ether ester solvents, glycerin, and pyrrolidone can be used.

In addition, antiseptic and fungicides such as 1,2-benzisothiazolin-3one, pentachlorophenol, and cresol, lubricants such as water-soluble silicone oil, and various surfactants can be appropriately selected and used.

The manufacturing method of water-based pigment ink consists of 5-20% by weight of pigment, 70-40% by weight of water, 10-30% by weight of water-soluble organic solvent, 1-30% by weight of resin acid, 0.05-20% by weight of acetamide and its derivatives ( In order to improve wetting of the pigment, 0.1 to 1% by weight of a surfactant may be used.) using a pigment dispersion machine such as a ball mill, roll mill, sand mill, super mill, dyno mill, or attritor. Mix, grind and disperse.

The aqueous pigment ink thus obtained has unprecedented dispersion stability.

Hereinafter, the present invention will be described in detail based on Examples, where "parts" in the Examples indicate "parts by weight."

Example 1 Carbon black 10.0 parts Propylene glycol 5.0 parts Ethylene glycol 15.0 parts Ceramic 2.0 parts Acetamide 20.0 parts Labelin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., anionic surfactant) 0.1 part Emulgen 931 (manufactured by Kao Atlas Co., Ltd., nonionic) Surfactant) 0.1 part Sodium pentachlorophenol (preservative)
0.1 part water 47.7 parts Among the above ingredients, add shellac to a solution of water and acetamide, stir and dissolve at room temperature. Next, Emulgen 931, ethylene glycol, and the remaining ingredients were sequentially added, premixed using a stirrer for 2 hours, and further ground in a ball mill for 20 hours, after which coarse particles were removed by filtration or the like.

The black water-based pigment ink obtained in this way was suction-filtered with 100 ml of Toyo Roshi No. 5c.
The entire amount passed through the filter paper within 30 seconds, and almost no residue was observed on the filter paper.

In addition, this ink was centrifuged at 5,000 rpm,
Although the treatment was carried out for 30 minutes, no precipitation of the pigment was observed.

Furthermore, even after filling a ballpoint pen with this ink, removing the cap, and leaving it in a constant temperature and humidity room at 20°C and 65% humidity for 10 days, the pen tip did not dry out and writing was still possible. .

Comparative Example 1 A water-based pigment ink was obtained in the same manner as in Example 1 except that shellac was removed and water was added. This ink has many coarse particles, and Toyo Roshi No.
It was not possible to filter with 5c.

Example 2 Copper phthalocyanine blue 15.0 parts Ethylene glycol 15.0 parts Propylene glycol 5.0 parts Decolorizing shellac 1.0 parts N-acetylethanolamine 10.0 parts Proxel GBX (manufactured by ICI, preservative) 0.1 parts Water 53.9 parts Adjusted in the same manner as in Example 1 After premixing, the mixture was mixed and ground in a sand mill for 10 hours to remove coarse particles to obtain a blue water-based pigment ink.

When this ink was suction filtered using 100 ml of Toyo Roshi No. 5c, the entire amount passed through the filter paper within 30 seconds, and no residue was observed on the filter paper.

In addition, this ink was centrifuged at 5,000 rpm,
Although the treatment was carried out for 30 minutes, no precipitation of the pigment was observed.

Furthermore, even after filling a ballpoint pen with this ink, removing the cap, and leaving it in a constant temperature and humidity room at 20°C and 65% humidity for 10 days, the pen tip did not dry out and writing was possible. .

Comparative Example 2 A water-based pigment ink was obtained in the same manner as in Example 2 except that N-acetylethanolamine was removed and water was added. The pen tip of this ink dried in one day under the same conditions as in Example 2.

Example 3 Copper phthalocyanine blue 10.0 parts Disazo yellow 5.0 parts Glycerin 2.0 parts Ethylene glycol 20.0 parts Humic acid 2.0 parts N,N'-dihydroxyethylacetamide 10.0 parts Emulgen A-60 (manufactured by Kao Soap Co., Ltd., nonionic surfactant) 0.1 part water 50.9 parts A green water-based pigment ink was obtained in the same manner as in Example 1.

When this ink was suction filtered using 100 ml of Toyo Roshi No. 5c, the entire amount passed through the filter paper within 30 seconds, and almost no residue was observed on the filter paper.

In addition, this ink was centrifuged at 5,000 rpm,
Although the treatment was carried out for 30 minutes, no precipitation of the pigment was observed.

Furthermore, even after filling a ballpoint pen with this ink, removing the cap, and leaving it in a constant temperature and humidity room at 20°C and 65% humidity for 10 days, the pen tip did not dry out and writing was still possible. .

As explained above, the water-based pigment ink of the present invention using resin acid and acetamide and/or its derivatives has excellent dispersibility and dispersion stability, and has good drying resistance, so it can be particularly used as a low viscosity ink. Specifically, it can be suitably used for writing instruments using fibers, felt, and monofilament, capillary type writing instruments such as fountain pens, narrow rod type and ball point type writing instruments, and also for recorders, printing, and stamps. It can also be applied to jet printers, etc.

Claims (1)

[Scope of Claims] 1. An aqueous pigment ink comprising a resin acid and an acetamide and/or a derivative thereof represented by the following general formula. general formula (In the formula, R ₁ = - (CH ₂ CH ₂ O) nH, R ₂ = - (
_CH2CH2O )mH n=integer of 0 to 50, m ₌ integer of 0 to 50. )