JPS6152869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-based ink with excellent drying resistance.

Traditionally, for example, writing instruments, specifically writing instruments with pen nibs made of fiber, felt, or monofilament,
Or, for capillary type writing instruments such as fountain pens, even if the pen tip is exposed to the atmosphere for a long time during storage or when the cap is removed from the writing instrument body, ink always flows smoothly without clogging the ink flow path of the pen tip. There was a need for a water-based ink that would flow and allow extremely smooth writing.

In order to meet these demands, glycol solvents such as ethylene glycol and propylene glycol, glycol ether solvents such as ethylene glycol monomethyl ether, glycol ether ester solvents such as ethylene glycol monomethyl ether acetate, amine solvents such as triethanolamine, and formamide. Water-based inks are known that improve drying resistance by incorporating water-soluble organic solvents such as amide solvents such as amide solvents, or hygroscopic inorganic compounds such as lithium chloride into an aqueous solution of water-soluble dyes. It was not possible to obtain a product that satisfactorily satisfies drying resistance. The reason for this is that glycol solvents generally have a high viscosity and a high boiling point, so when used in large quantities, the viscosity of the ink increases, and when used in writing instruments that require low viscosity, the outflow of the ink is inhibited.
It causes the ink to run out, and it also makes handwriting difficult to dry, and there is a limit to the amount that can be used, making it impossible to add enough to satisfy drying resistance.

Glycol ether solvents and glycol ether ester solvents generally have low surface tension, so handwriting tends to smear, and the ink may penetrate to the back side of the paper or smudge on the surface, making it impossible to obtain clear handwriting. It has drawbacks such as low dissolving power for dyes, making it impossible to obtain sufficient color development, and strong odor, and similarly to the above, it is not possible to add it in an amount sufficient to satisfy drying resistance.

Since amine solvents have an unpleasant odor peculiar to amines, they cannot be added in an amount sufficient to satisfy drying resistance.

Amide solvents undergo significant hydrolysis and lower PH, so they cannot be used for dyes that are highly PH-dependent. Furthermore, since it is highly corrosive to metals, it has the disadvantage that there are limits to the materials that can be used for writing instruments.

Hygroscopic inorganic compounds such as lithium chloride and calcium chloride react with dyes to form salts and reduce the solubility of dyes, making it difficult to prepare highly concentrated inks and requiring only a sufficient amount to satisfy drying resistance. cannot be added.

The inventors of the present invention have conducted various studies to solve the conventional problems mentioned above, and have found that when a certain substance is included in an aqueous solution of water-soluble dye, the drying resistance is good and the viscosity increases rapidly. The present invention was completed based on the discovery that a water-based ink with excellent dye solubility can be obtained without the above-mentioned methods.

That is, the gist of the present invention is a water-based ink containing at least water, a water-soluble dye, and 1,3-dimethyl-2-imidazolidinone.

Next, each component of the water-based ink of the present invention will be explained in more detail. As water-soluble dyes, most dyes such as acid dyes, direct dyes, and basic dyes can be used. Specific examples of acid dyes include Eiseneosin GH (CI45380), Nigrosin NBconc. (CI50420), solvable blue
OBB (CI42780), Soluble Blue OBC (C.
Direct dyes include Direct Deep Black EX (CI30235), Kayala Black Gconc. (CI35225), and Water Black #100 (CI35255), and basic dyes include Victoria Blue FB (CI35255). CI44045), Methyl Violet FN (CI42535), Rhodamine
F4G (CI45160) and the like can be used alone or in combination with other water-soluble dyes. The amount of water-soluble dye used varies depending on the purpose of use, but for example, when used as an ink for writing instruments, the amount of water-soluble dye used is
Suitable results are obtained when 0.1 to 30% by weight is used. The amount of 1,3-dimethyl-2-imidazolidinone to be used is 2 to 50% by weight based on the total amount of the ink, however, as an ink for writing instruments, it is preferably used in an amount of 5 to 40% by weight.

As described below, the present invention greatly improves drying resistance by incorporating 1,3-dimethyl-2-imidazolidinone into an aqueous solution of a water-soluble dye, but this compound is odorless. There is no need to worry about odors. Also, if necessary, glycol-based
Glycol ether-based, amine-based, amide-based solvents, and additives such as surfactants and preservatives may be appropriately selected and used.

Hereinafter, embodiments of the present invention will be described using ink for writing instruments as an example. In the examples, "parts" simply indicate "parts by weight."

Example 1 (Black ink) Kayarasu Black Gconc. (CI35225) 5.0 parts 1,3-dimethyl-2-imidazolidinone 35.0〃 Water 60.0〃 A mixture of the above components was heated to 40 to 50°C and 1 After stirring for an hour, the viscosity is 2.4 cps (at 25℃)
The desired black ink could be obtained. When this ink was filled into a writing instrument similar to a commercially available felt-tip pen and written on paper, the ink flowed out smoothly, and after removing the cap and leaving it in the air for 20 days, there was no smudging when writing. I was able to write it down. Further, the ink did not penetrate to the back side of the paper or bleed. However, when propylene glycol was used instead of 1,3-dimethyl-2-imidazolidinone, when the cap was removed and left in the atmosphere, complete smearing occurred within 4 hours.

Example 2 (black ink) Nigrosine NBconc. (CI50420) 4.0 parts 1,3-dimethyl-2-imidazolidinone 25.0〃 Water 60.6〃 Ethylene glycol 10.0〃 Inogen P (surfactant) 0.2〃 Formalin (preservative) 0.2 〃 Example 3 (Red ink) Eiseneosin GH (CI45380) 10.0 parts 1,3-dimethyl-2-imidazolidinone 20.0〃 Water 64.2〃 Ethylene glycol monomethyl ether 5.0〃 Score Roll 900 (surfactant) 0.4〃 Formalin ( Preservative) 0.4〃 Example 4 (Blue ink) Victoria Blue FB (CI44045) 3.0 parts 1,3-dimethyl-2-imidazolidinone 35.0〃 Water 57.0〃 Diethylene glycol 5.0〃 Also carried out for the above Examples 2, 3, and 4 Viscosity 2.8 cps (at 25℃) and 3.5 cps respectively as in Example 1.
(at 25℃) and 4.0 cps (at 25℃) of the desired ink. Further, when the ink was filled in a writing instrument and written on paper in the same manner as in Example 1, the flow of the ink was slightly different, but the flow was good in all cases. In other respects, almost the same results as in Example 1 were obtained.

Although the present invention has been described above with respect to a water-based ink for writing instruments, it can also be applied to water-based inks for stamps, printing, etc.

Claims (1)

[Claims] 1 Water, water-soluble dye and 1,3-dimethyl-2
- A water-based ink containing at least imidazolidinone.