JPH11148043A - Water base gel ink for ball-point pen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink having a good thixotropic property, having a brilliant color and excellent light resistance, and having good writing touch, good stability to temperature, and good storage stability by adding a specific thickening gelation agent. SOLUTION: This ink contains (A) xanthane gum and (B) a hectorite inorganic thickener as thickening gelation agents. The component B is preferably added in an amount of 0.1-0.5 wt.%. The component B comprises one kind of montmorillonite stone mineral, preferably its synthetic one. The component A is preferably added in an amount of 0.1-1%. Thereby, the addition amount of the xanthane gum can be reduced, and the coloration and somberness due to the xanthane gum are prevented. The ink having a brilliant color can be expected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gel ink containing a viscosity modifier, which can be used for an aqueous ballpoint pen.

[0002]

2. Description of the Related Art An ink composition obtained by adding a viscosity modifier to an aqueous ink is called an aqueous gel ink.
It is widely used for water-based ballpoint pens that directly fill ink into ink reservoirs. As an example of such a conventional water-based ink for a ballpoint pen, there is known a water-based ink in which a specific amount of xanthan gum is added to adjust the viscosity as disclosed in Japanese Patent Publication No. 64-8673.

[0003]

The gel ink for an aqueous ballpoint pen has a thixotropy by adding a polymer-based thickening gelling agent such as xanthan gum, and a portion which is subjected to a shearing stress by rotation of the ball during writing. However, the portion that is not stressed is gel-like, and is usually configured not to flow out from the tip. Therefore, when the amount of the coloring agent added is increased, the overall viscosity increases, so that the fluidity is reduced and the writing taste is deteriorated. Therefore, conventional gel inks generally use a dye-based colorant or have a limited amount of addition even in the case of a pigment-based colorant, making it difficult to obtain a dark color. However, there was a drawback that excellent products such as light fastness could not be obtained.

[0004] Further, the conventional gel ink using xanthan gum has a drawback that the color is dull due to the influence of xanthan gum, so that a clear color ink cannot be obtained.

[0005] Further, inks using xanthan gum are susceptible to temperature, and when the temperature is higher than 50 ° C, there is a problem that the thickening effect is reduced and the thixotropy is reduced. Aqueous ballpoint pens filled with the gel ink may actually have a temperature during transportation or storage of more than 50 ° C., and thus are required to have temperature stability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the gel ink using the above-mentioned conventional xanthan gum as a thickening gelling agent, which has good thixotropy, clear color and light fastness and the like. An object of the present invention is to provide a water-based ballpoint pen gel ink which is excellent, has good writing characteristics, has good stability against temperature, and has excellent storage stability.

[0007]

The present invention provides (1) a gel ink for aqueous ballpoint pens, which comprises xanthan gum and a hectorite-based inorganic thickener as a thickening gelling agent; The amount of the thickener added is 0.
A gel ink for an aqueous ballpoint pen according to the above (1), which is 1 to 0.5% by weight.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The gel ink of the present invention uses xanthan gum and a hectorite-based inorganic thickener as a thickening gelling agent. The hectorite-based inorganic thickening gelling agent is a kind of montmorillonite group mineral, and may be either a natural product or a synthetic product, but a synthetic product is preferably used. The synthetic product has particularly low coloration and excellent transparency, does not contain crystalline impurities that do not swell, and has strong gel strength because the primary particles are small and uniform.

The synthetic hectorite-based inorganic thickener is Lap
orte Industries Ltd. A product commercially available under the registered trademark “LAPONITE” manufactured by Nippon Silica Kogyo Co., Ltd. under the trade name “Laponite” can be used. The synthetic hectorite-based inorganic thickener is an agglomerate composed of fine disk-shaped primary particles having a diameter of 20 to 40 μm and a thickness of about 1 nm, and has a chemical composition represented by the following formulas (1) and (2). Have.

[0010]

## STR1 ## [Si ₈ (Mg _5.34 Li _0.66 ) O ₂₀ (O
H) ₄ ] M + _0.66

## STR2 ## [Si ₈ (Mg _5.34 Li _0.66 ) O ₂₀ (OH.
F) ₄ ] M + _0.66

These synthetic hectorites have a three-layer structure as shown in FIG. 1, and extend two-dimensionally to form platelet particles. Some of the magnesium atoms in the platelet particles are isomorphously substituted with lower-valent lithium (monovalent cation), and the platelet particles are negatively charged due to charge deficiency. The primary particles of the synthetic hectorite in a dry state are secondarily aggregated into a large flat plate bundle.

As shown in FIG. 1, the synthetic hectorite-based inorganic thickener has an ionic bond, which is easily broken when a shear stress is applied thereto, and is easily regenerated when allowed to stand. Shows high thixotropy. This property is due to a different mechanism from that of increasing the viscosity by entanglement of fibers of a long chain polymer of a high molecular weight such as xanthan gum.

As described above, the hectorite-based inorganic thickener has a large thickening effect and a high thixotropy. Therefore, when used alone, the effect of preventing sedimentation of the pigment is improved, but the viscosity increases after storage. Too much, resulting in an extremely low fluidity and an instability such as a poor writing quality. In the gel ink of the present invention, by using xanthan gum in combination with the hectorite-based inorganic thickener, the instability of this hectorite-based inorganic thickener is improved, the gel state is appropriately adjusted, and the fluidity is ensured to be stable. The obtained thixotropic ink is obtained.

The amount of the hectorite-based inorganic thickener in the gel ink of the present invention is preferably in the range of 0.1 to 1% by weight. If the amount of the hectorite-based inorganic thickener exceeds 1% by weight, the gel structure may become too strong after storage and the like over time and the writing taste may be impaired. There is a possibility that sufficient thixotropy may not be obtained, and the stability of viscosity with respect to temperature may be reduced.

The amount of xanthan gum added is preferably in the range of 0.1 to 1% by weight. The amount of xanthan gum added is 0.
If the amount is less than 1% by weight, sufficient stability of the ink may not be obtained. If the amount exceeds 1% by weight, the viscosity of the ink as a whole may be too high and the thixotropic property may be reduced. In addition, xanthan gum alone cannot greatly increase the thixotropy, and has problems such as a low effect of preventing sedimentation of the pigment and a decrease in viscosity due to aging after storage. Further, when the amount of added xanthan gum is increased, the overall viscosity increases, the thixotropy is not significantly improved, and the writing taste is reduced.

Xanthan gum can be used, for example, as a commercial product under the trade name "Kelzan" of Sansei Co., Ltd.

The ink of the present invention can be colored into various colors by adding a coloring agent in addition to the thickening gelling agent. As such a coloring agent, for example,
Carbon black, Carmine 6B, CI Pigment Red, C.
Pigment such as I.PigmentGreen7, CI PigmentBlue, CIAci
dRed87, CIAcidRed92, CIAcidYellow28, CIAci
dBlue9, CIAcidViolet, CIAcidBlue7, CIAcidO
Acid dyes such as range56, CIAcidBlack2, CIAcidRed18, CIDirectBlack19, CIDirectBlack38, CIDire
ctBlack154, CIDirectOrange6, CIDirectYellow4
4, direct dyes such as CIDirectYellow87 and CIDirectBlue71. The colorant is preferably a pigment-based one from the viewpoint of light resistance and the like.

The ink composition of the present invention contains water, an aqueous medium, a preservative, a rust inhibitor, a sequestering agent, a surfactant, and a dispersant as components other than the above-mentioned thickening gelling agent and coloring agent. ,
Known components conventionally used, such as a pH adjuster, can be added to this type of aqueous ballpoint pen gel ink.

As the aqueous medium, an organic compound miscible with water is used, and alcohols, glycol ethers, polar organic solvents and the like are used. Specifically, as alcohols, monohydric alcohols such as ethanol and isopropyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, 1,3 propanediol, propylene glycol, 1,3 butylene glycol, 1,4 butanediol, Dihydric alcohols such as 2,3 butylene glycol, neopentyl glycol, hexylene glycol, thiodiglycol, glycerin, trimethylolethane, trimethylolpropane,
Polyhydric alcohols such as 3-methylpentane-1,3,5-triol, diglycerin, and sorbite;
Examples of the glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and the like. 2-pyrrolidone, dimethylformamide and the like.

Examples of the pH adjuster include sodium hydroxide, sodium carbonate, triethanolamine and the like; surfactants such as anionic and nonionic surfactants; rust preventives such as benzotriazole; As sequestering agents such as methyl-P-hydroxybenzoate, potassium sorbate, sodium pentachlorophenol, and sodium dehydroacetate;
DTA and the like. These additives are added in appropriate amounts as needed.

[0021]

EXAMPLES Specific examples of the present invention will be described below. Example 1 The following components were mixed to obtain a black ink gel ink for an aqueous ballpoint pen.・ SP-BK 8406 * 1 42.0 parts by weight ・ Xanthan gum 0.5 〃 ・ Laponite S * 2 0.28 〃 ・ Propylene glycol 8.0 〃 ・ Ethylene glycol 12.0 〃 ・ Score roll * 3 1.0 重量-Neugen EA-120B * 4 1.0 * Tetron 410 * 5 0.4 * Sodium benzoate 0.4 * Benzotriazole 0.7 * Water 33.72 *

* 1: About 20% of black pigment component * 2: Synthetic hectorite-based thickening and gelling agent [manufactured by Nippon Silica Industry Co., Ltd.] * 3: Surfactant [manufactured by Kao Corporation] * 4: Surfactant, dispersant [Daiichi Kogyo Seiyaku Co., Ltd.] * 5: Sequestering agent [Meisei Chemical Co., Ltd.]

FIG. 2 shows the measurement results of the viscosity of the ink of Example 1. The viscosity was measured at a temperature of 25 ° C. using a R115 type viscometer manufactured by Toki Sangyo Co., Ltd. and a RC-105A type computer manufactured by Toki Sangyo Co., Ltd. The results obtained by measuring the viscosity of a commercially available gel ink for aqueous ballpoint pens under the same conditions as in Example 1 are shown as Reference Examples.

Comparative Example 1 The same composition as in Example 1 was used except that xanthan gum was omitted. Comparative Example 2 The composition was the same as in Example 1 except that Laponite S was omitted. For the inks of Example 1 and Comparative Examples 1 and 2,
Table 1 shows the test results of the writing taste and the taste immediately after production and after storage. After storage, the state after storage at 50 ° C. for 7 days is shown.

[0025]

[Table 1] In the sedimentation separation test, when the ink filled in the ink storage tube was visually observed, there was no sedimentation, and there was no color unevenness when actually written, and ○ was given when there was some sedimentation or color unevenness. , Settling or severe color unevenness was evaluated as x. Further, in the writing taste test, a case where good writing was actually performed was evaluated as ○, a case where the smoothness was slightly lacking was evaluated as △, and a case where there was no smoothness was evaluated as ×.

[0026]

As described above, the ink of the present invention has excellent thixotropic properties by using xanthan gum and a hectorite-based inorganic thickener as a thickening gelling agent. Compared with the ink using as a thickening gelling agent, any dye-based or pigment-based coloring agent can be used, the amount of addition can be increased, dark color, excellent light resistance, and writing A gel ink with excellent taste is obtained.

Further, compared to the conventional ink using only xanthan gum as a thickening gelling agent, the amount of added xanthan gum can be reduced, so that coloring and dulling of xanthan gum can be prevented, and clear color can be obtained. Is obtained.

Further, in the ink of the present invention, since the hectorite-based inorganic thickener is hardly affected by the temperature, the thixotropic property does not decrease even at a temperature of 50 ° C. or more. Even if the temperature reaches 50 ℃ or more during storage, the gel structure will not be broken.
Excellent storage stability without deterioration in writing taste after storage.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the structure of a synthetic hectorite.

FIG. 2 is a graph showing viscosity characteristics of the ink of the present invention.

Claims (2)

[Claims] 1. A gel ink for aqueous ball-point pens, comprising xanthan gum and a hectorite-based inorganic thickener as a thickening gelling agent. 2. The amount of addition of a hectry inorganic thickener of 0.
The aqueous gel ink for a ballpoint pen according to claim 1, wherein the content is 1 to 0.5% by weight.