JP3383104B2 - Water-based ink for writing instruments - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a water-based ink for writing instruments,
In particular, the present invention relates to an ink that uses a mechanism for storing ink directly in a tubular ink storage portion in a writing instrument without using a fiber bundle or foam for storing ink.

[0002]

2. Description of the Related Art In general inks for writing instruments, colorants such as dyes and pigments are dissolved and / or dispersed in a solvent.
If necessary, add resin to improve fixability and adjust viscosity.
A surfactant is added to improve solubility and dispersion stability, and an antiseptic / antifungal agent is added. Here, since the viscosity of the ink is closely related to the form of the writing instrument, it has been regarded as important.

In the case of a writing instrument using a water-based ink, a writing instrument in which an ink having a viscosity of 1 to several mPa · s is impregnated in an ink storage body made of a fiber bundle has been used in many cases. However, in the case of the above-mentioned ink storage body impregnated with ink, the remaining amount of ink is difficult to see from the outside. In order to solve this point, there is a method in which the viscosity of the ink is increased and the ink is contained in a transparent tubular container, and it is possible to check both the ink holding state and the remaining amount of the ink in the container.

Conventionally, in the case of water-based ink containing water as a solvent, a resin has been used as a regulator of ink viscosity.
For example, natural gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, casein, xanthan gum, dextran, semisynthetic methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium starch glycolate, propylene glycol alginate. Ester, synthetic polyvinyl alcohol, polyvinylpyrrolidone, polyvinylmethyl ether, sodium polyacrylate, carboxyvinyl polymer, polyethylene oxide, copolymers of vinyl acetate and polyvinylpyrrolidone, water-soluble polymers such as alkali metal salts of acrylic resin One kind or a mixture of two or more kinds is shown.

When the above resin is used as the viscosity modifier of the ink, there are various problems as listed below. (1) Depending on the type of dye or pigment, dye insolubilization or pigment aggregation may occur. (2) The molecular bonds of the added resin are broken due to decomposition by microorganisms or decomposition due to oxidation, and the function of adjusting the viscosity is not exerted. As a result, the viscosity of the ink decreases with time. (3) Even if the ink viscosity is adjusted using a resin, both the ink retention state in the ink storage tube when the ink is filled in the ballpoint pen ink and left standing and the good drawing state at the time of writing are compatible. I can not do it, I can not hold the ink even when left stationary,
Ink leaks from the pen tip, and when writing, excess or deficiency of the amount of ink outflow easily causes bloating and blurring. (4) Depending on the nature of the resin used, the ink may have spinnability and tackiness, which may cause troubles in writing.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. Ink is not leaked even when the pen is left stationary, stable writing performance is obtained without change over time. It is to provide a water-based ink for a writing instrument having the same.

[0007]

The aqueous ink for writing instruments of the present invention comprises poly [N, N-dimethylacrylamide], a colorant and water. Preferred poly [N,
N-dimethylacrylamide] has a viscosity of 2 to 20 mPa · s
[Poly [N, N
-Dimethylacrylamide] having a concentration of 0.5% was measured with a B-type viscometer (rotation speed 60 rpm, rotor No. 1) at a temperature of 25 ° C. In addition, poly [N,
The content of N-dimethylacrylamide] in the ink is 0.
1 to 10% by weight, the colorant in the ink is 0.5 to 30% by weight, and the water is preferably 50% or more of the total solvent. A preferred colorant is a water-soluble dye, a pigment, or a resin latex obtained by emulsion polymerization, which is dyed with a dye.

Poly [N, N- used in the ink of the present invention
Dimethylacrylamide] is obtained by radical polymerization of N, N-dimethylacrylamide. By increasing or decreasing the amount of radical polymerization initiator used, poly [N, N-dimethylacrylamide] having different molecular weights and polymerization degrees can be obtained. In the present invention, instead of the above-mentioned molecular weight and degree of polymerization, the viscosity [using a 4% sodium chloride aqueous solution as a solvent, the concentration of poly [N, N-dimethylacrylamide] is 0.5
% Solution for B type viscometer (rotation speed 60 rpm, rotor N
According to o.1), the measurement was performed at a temperature of 25 ° C.]. The preferred viscosity of the poly [N, N-dimethylacrylamide] used in the ink of the present invention is 2 to 20 mPa · s. The viscosity and the amount of poly [N, N-dimethylacrylamide] used in the ink of the present invention vary depending on the desired ink viscosity, ink characteristics, and colorant used, but the preferred viscosity is 2 to 20 mPa · s, the amount used. Is 0.1 to 10% by weight in the ink
Is. Within the range of 2 to 20 mPa · s, 2 to 5 mPa · s,
5-10 mPa ・ s, 10-15 mPa ・ s, 15-20 mPa ・ s
In the same range of 0.1-10%, the amount used is 0.1-0.5%, 0.5-2.5%, 2.5
It is preferable to select each in the range of 10%.

The water-based ink of the present invention, as a colorant,
Although it is possible to use a wide range of dyes and pigments conventionally used in water-based ink compositions, examples of dyes include:
C. I. Direct Black 19, C.I. I. Direct Black 154, C.I. I. Direct dyes typified by Direct Blue 87, C.I. I. Acid Black 2,
C. I. Acid Yellow 23, C.I. I. Acid Red 18, C.I. I. Acid Blue 9, C.I. I. Acid dyes represented by Acid Violet 49 and the like can be mentioned. A wide variety of dyes can be used in the present invention as long as they are water-soluble and are not limited to the examples given here.

The pigments usable in the present invention include general pigments such as carbon black, cyanine blue, and naphthol red, as well as pseudo pigments obtained by dyeing a resin latex obtained by emulsion polymerization. It may be a pigment. As the pseudo pigment, an acrylic resin latex dyed with a fluorescent dye is used for writing instrument ink. The type of these pigments is not particularly limited as long as they can be well dispersed in water. The dyes and pigments can be used alone or in combination of two or more, and the dyes and pigments can be mixed. The content of the colorant is not particularly limited, but in the case of dyes and general pigments, it is 0.5
.About.15%, and in the case of a similar pigment, 1 to 30% is the usual content range.

The solvent of the present invention essentially requires water, and various organic solvents soluble in water can be mixed and used.
Specific examples of the organic solvent include organic solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1,3-propanediol, ethylene glycol, propylene glycol, diethylene glycol and glycerin. These organic solvents are not limited to the above examples as long as they are freely mixed with water or have extremely high water solubility close to that. Further, two or more kinds of organic solvents can be mixed and used. Appropriately less than 50% of the total amount of the organic solvent is used.

In the ink of the present invention, various polymer dispersants and surfactants are used for the purpose of satisfying the characteristics of the writing instrument, in order to disperse the pigment, develop lubricity, and improve the wetting of the ink on the paper surface and members. Can be used. Examples of the polymer dispersant include ionic ones such as salts of styrene-maleic acid copolymers and styrene-acrylic acid copolymers, and nonionic ones such as polyvinyl alcohol, polyvinylpyrrolidone and polyethylene glycol. . Further, as the surfactant, fatty acid salts such as potassium oleate, higher alcohol sulfate ester salts such as sodium lauryl sulfate, anionic surfactants such as phosphate ester salts, polyoxyethylene alkyl ethers, sorbitan alkyl esters, etc. Nonionic surfactants may be mentioned.

Further, the ink of the present invention may contain an antiseptic / antifungal agent such as phenol or sodium benzoate in order to prevent deterioration of the ink due to mold or microorganisms. Further, in the case of a writing instrument such as a ballpoint pen that uses a metal in a portion that comes into contact with ink, a rust preventive agent such as benzotriazole or ethylenediamine tetraacetate can be used to prevent corrosion of the metal. Additives other than poly [N, N-dimethylacrylamide], a colorant, water, and a water-soluble organic solvent in the ink of the present invention are preferably less than 5% of the total amount of the ink.

The ink of the present invention can be obtained by mixing and stirring the essential components poly [N, N-dimethylacrylamide], a colorant and water. If necessary, an operation of removing impurities mixed in by filtration, centrifugation, or the like may be performed. Examples of writing means using the ink of the present invention include a ballpoint pen, a writing instrument using a writing brush, a fiber bundle nib, a synthetic resin nib, and the like, and a ballpoint pen is particularly preferable.

Poly [N, N-dimethylacrylamide]
By using, it is possible to obtain a water-based ink in which the ink does not leak from the pen tip even when the ink is directly placed in a tubular container and allowed to stand, even though the ink has a relatively low viscosity. Therefore even be compatible is drawn lines state at the time of writing and holding of the ink when standing in inks of any viscosity, easier to see the ink remaining amount, mechanism is simple, it can be realized writing instrument with good writing characteristics. In addition, the above poly [N, N-dimethylacrylamide] is a stable ink for a long period of time because it does not cause the growth of bacteria and does not hinder the dissolution and dispersion of dyes and pigments as compared with the commonly used natural viscosity modifiers. It is possible to obtain

[0016]

EXAMPLES The ink of the present invention will be described below with reference to Examples and Comparative Examples. The viscosity of the poly [N, N-dimethylacrylamide] used in the examples is a B-type viscometer prepared by preparing a 0.5% poly [N, N-dimethylacrylamide] solution using a 4% sodium chloride aqueous solution as a solvent. (Rotation speed 60 rpm,
Value (mPa) measured at a temperature of 25 ° C with rotor No. 1)
・ S).

Example 1 (Dye ink type) Eosin 4.0 parts by weight (CI Acid Red 87) Poly [N, N-dimethylacrylamide] (viscosity: 9.0 mPa · s) 4.0 parts by weight benzo Triazole 0.1 parts by weight Potassium oleate 0.1 parts by weight Sodium benzoate 0.1 parts by weight Ethylene glycol 30.0 parts by weight Water 61.7 parts by weight The above composition is stirred for 3 to 4 hours at room temperature and then filtered. hand,
I got red ink.

Example 2 (Pigment ink type) Carbon black (furnace type) 7.0 parts by weight Dispersant [styrene-acrylic acid copolymer resin (NH ₃ neutralized)] 2.0 parts by weight Sodium benzoate 0.1 Parts by weight benzotriazole 0.1 parts by weight potassium oleate 0.1 parts by weight glycerin 20.0 parts by weight 2-amino-2-methyl-1-propanol 0.5 parts by weight water 68.2 parts by weight poly [N, N -Dimethylacrylamide] (viscosity: 3.6 mPa · s) 2.0 parts by weight A concentrated solution of the compounding ingredients except for the above poly [N, N-dimethylacrylamide] is first premixed and dispersed for 2 hours in a vertical sand mill. , Let down and then dilute to prepare the original formulation, classify with a centrifuge, and then add poly [N, N-dimethylacrylamide] while stirring at room temperature. Filtered after stirring for further 3 to 4 hours after the addition and Kkuri to obtain a black ink.

Example 3 (Fluorescent ink type) NKW-2317 (manufactured by Nippon Fluorescent Co., Ltd.) 50.0 parts by weight (synthetic resin latex dyed with a fluorescent dye) Poly [N, N-dimethylacrylamide] (viscosity : 3.6 mPa · s) 1.0 part by weight Phenol 0.1 part by weight Benzotriazole 0.1 part by weight Potassium oleate 0.1 part by weight Propylene glycol 30.0 parts by weight Water 19.7 parts by weight With the above composition The same treatment as in Example 1 was carried out to obtain a pink ink.

Comparative Example 1 An ink of Comparative Example 1 was obtained by preparing an ink in the same manner as in Example 1 except that guar gum was used instead of poly [N, N-dimethylacrylamide].

Comparative Example 2 An ink was prepared in the same manner as in Example 2 except that poly [N, N-dimethylacrylamide] was used and partially crosslinked sodium polyacrylate was used.

Comparative Example 3 An ink of Comparative Example 3 was obtained in the same manner as in Example 3 except that poly [N, N-dimethylacrylamide] was used in place of polyacrylamide.

Examples 1 to 3 and Comparative Examples 1 to 1 obtained as described above
For the ink of No. 3, polypropylene tubes (internal diameter 5 mm, length 110 mm) were filled with each ink, and a stainless steel chip having a ball with a diameter of 0.5 mm was fitted to one end of the ink and defoamed by centrifugation. The following test was performed with the pen body. Writing performance test: Writing on the pen at room temperature
The line quality, such as stains due to excessive spinnability, was evaluated according to the following criteria. ◯: Almost no defects of line drawing such as scratches and batters were observed,
Good drawing condition. Δ: Defects in the drawn line such as scratches and flakes are observed everywhere, and the drawn line state is not preferable. X: The state of the drawn line is poor and the characters or the like cannot be read. Ink leakage test: After the cap was removed and the pen tip was faced down, the ink was allowed to stand at room temperature for a certain time (30 minutes if a number was required), and then evaluated according to the following criteria. ◯: No change is recognized. Δ: Ink leaks around the ball and the tip of the ball-point pen holder, but ink drops do not fall. ×: Ink droplets leaking from the tip of the ballpoint pen holder fall. Ink aging performance: The ink is sealed in a glass sample bottle and left at 50 ° C., 0 ° C. and room temperature.
The physical properties such as pH and the presence or absence of aggregation of dyes and pigments were examined, and the aging performance of the ink was evaluated according to the following criteria. ◯: Almost no change in viscosity, pH, etc. was observed, and the initial performance was maintained. B: Useable, but some measured values show clear changes. X: The properties of the ink changed greatly and could not be used. The above results are shown in Table 1.

[0024]

[Table 1]

[0025]

[Effects of the Invention] Prevents ink from leaking out when it is left stationary.
Provided is a water-based ink for a writing instrument that realizes good writing performance and stability of the ink over time.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-339516 (JP, A) JP-A-5-179183 (JP, A) JP-A-6-49142 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (6)

(57) [Claims] 1. An aqueous ink for a writing instrument, which comprises poly [N, N-dimethylacrylamide], a colorant and water. 2. Poly [N, N-dimethylacrylamide] has a viscosity of 2 to 20 mPa · s [poly [N, N-dimethylacrylamide] using a 4% sodium chloride aqueous solution as a solvent.
Solution with 0.5% concentration of B-type viscometer (rotation speed 60
rpm, rotor No. 1) at a temperature of 25 ° C.]. 3. The content of poly [N, N-dimethylacrylamide] in the ink is 0.1 to 10% by weight, the colorant is 0.5 to 30% by weight in the ink, and water is 50% or more of the total solvent. The water-based ink for a writing instrument according to claim 1, which is present. 4. The water-based ink for a writing instrument according to claim 3, wherein the colorant is a water-soluble dye. 5. The water-based ink for a writing instrument according to claim 3, wherein the colorant is a pigment. 6. The water-based ink for a writing instrument according to claim 3, wherein the colorant is obtained by dyeing a latex of a resin obtained by emulsion polymerization with a dye.