JP2000319570A - Water-color ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-color ink composition enabling written lines to be dried at higher rate and also capable of exhibiting effect on preventing a penpoint from being dried. SOLUTION: This water-color ink composition comprises at least coloring matter, water and 1,4-cyclohexanedimethanol and, optionally, at least one kind selected from the group consisting of ethyl alcohol, n-propyl alcohol and isopropyl alcohol in an amount of 5-20 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink for a printing tool, and more particularly to an ink used for a printing tool such as a writing tool, a marking tool or an ink jet, which can suppress drying of the ink at the tip of the pen. Composition.

[0002]

2. Description of the Related Art Water-based inks used in writing instruments have been used for a long period of time with the pen tip open, and the liquid components (water and organic solvents) in the ink evaporate to reduce the viscosity of the ink. Often, the ink dries and becomes unwritable. Therefore, in order to impart drying resistance, it has been quite common to add a hygroscopic organic solvent such as glycerin, ethylene glycol, propylene glycol, or diethylene glycol. However, in order to obtain the effect of suppressing drying with these hygroscopic organic solvents, at least about 15 to 25% by weight must be added to the ink. However, there was a drawback that it became slow. Particularly recently, writing instruments filled with water-based ink that can be written on non-absorbing surfaces such as glass and plastic, which have been rarely used in the past, have been used in many cases, in which case large amounts of hygroscopic organic solvents have been used. Addition significantly slows down the drying of the writing line on the non-absorbing surface, which is a fatal drawback.

[0003] As described above, a decrease in ink performance (bleeding, drying property, etc.) caused by adding a large amount of the above-mentioned hygroscopic organic solvent to an ink composition in order to improve drying resistance is suppressed, and drying resistance is reduced. Various proposals have hitherto been made in order to obtain an aqueous ink composition having excellent properties. For example, blending of hydroquinone (JP-A-9-241570) and blending of saligenin (JP-A-9-675)
37, and the addition of para-xylene glycol (Japanese Patent Application Laid-Open No. 9-12957).

[0004]

It is another object of the present invention not only to suppress the drying at the tip of the pen but also to speed up the drying of the writing line after writing by using the above-mentioned drying inhibitor. One object of the present invention is as follows. That is, while the present invention minimizes the addition of the hygroscopic organic solvent to the minimum necessary to speed up the drying of the writing line, the pen nib in the open state causes precipitation of 1,4-cyclohexanedimethanol added to the ink. The present invention provides an aqueous ink composition which can suppress the evaporation of liquid components (water and lower alcohol) in the ink to prevent drying, and further, can provide the effect of accelerating the drying of writing lines by adding a lower alcohol. The purpose is to do so.

[0005]

The above objects can be achieved by the following inventions. (1) An aqueous ink composition comprising at least a colorant, water and 1,4-cyclohexanedimethanol. (2) The aqueous ink composition according to the above (1), further comprising 5 to 20% by weight of at least one alcohol selected from ethyl alcohol, n-propyl alcohol and isopropyl alcohol.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art. As a result, when 1,4-cyclohexanedimethanol represented by the following chemical formula was added to the aqueous ink, the ink at the pen tip portion was removed. It was discovered that the effect of suppressing the drying of the ink was obtained, and furthermore, one or more of ethyl alcohol, n-propyl alcohol and isopropyl alcohol were added to the ink, so that the drying of the writing line was simply accelerated. In addition to the above effects, the present invention has been confirmed by confirming that the water-based ink to which 1,4-cyclohexanedimethanol has been added has an effect of further improving the drying suppression effect at the pen tip. .

[0007]

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[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the amount of 1,4-cyclohexanedimethanol added is 3 to 12% by weight, preferably 5 to 10% by weight, based on the composition. Here, if the amount is less than 3% by weight, the effect of suppressing drying at the pen tip portion is not sufficient, and if it exceeds 12% by weight, the effect does not increase so much. This is not preferable because of the adverse effect of lowering the value.

The aqueous ink of the present invention comprises a colorant, water and 1,
It is characterized by containing at least 4-cyclohexanedimethanol, but as the colorant, dyes and pigments used in conventional aqueous inks can be used without any restrictions. In addition, commonly used preservatives, fungicides, pH adjusters, surface tension adjusters and the like can be used as necessary. However, as already mentioned,
Glycerin, propylene glycol, ethylene glycol, diethylene glycol, etc., which are usually used as humectants or deicers, have the disadvantage of slowing down the drying of writing lines, and drying on permeable writing surfaces such as paper is still glass. In the case of writing on a non-absorbing surface such as plastic or plastic, there is a fatal drawback. Here, the amount of the coloring agent used is
Usually, it is about 3 to 10% by weight as required, but is not particularly limited.

In the present invention, the direct drying suppression effect by the addition of 1,4-cyclohexanedimethanol does not necessarily require the drying suppression effect by the addition of the above-mentioned humectant, but may reduce the effect. Test results have been obtained. Regarding the purpose of preventing freezing, which is another purpose of using the humectant, it has been recognized that the same purpose can be achieved by the addition of alcohols of the above (2). Of course, it is clear that alcohols have the effect of accelerating the drying of the writing line more directly from the respective evaporation rates, but as mentioned above,
It is clear from the test results that an unexpected effect of further increasing the effect of suppressing the drying of 1,4-cyclohexanedimethanol by adding alcohols may be exhibited. The reason is not always clear.

Further, it can be considered from the above test results that when a solvent having a lower evaporation rate than water dissolves the drying inhibitor better than water, the effect of suppressing the drying is hardly obtained, and the evaporation rate is lower than that of water. If the fast solvent dissolves the drying inhibitor better than water, the drying inhibitory effect tends to be easily obtained. Have a tendency to be large. The selection, combination and addition amount of the type of alcohol must be determined by comprehensively evaluating the drying suppression effect and the drying time of the writing line, strikethrough when writing on paper, etc. If the amount of the alcohol exceeds 20% by weight, strike-through occurs even on a slightly thick paper such as Kent paper, and 5% by weight.
If it is less than 3, the effect of accelerating the drying of the writing line on the non-absorbing surface cannot be sufficiently obtained. A preferred range is from 8 to 18% by weight.

As described above, the alcohols described above serve as an antifreezing agent for ink and a drying accelerator for writing lines, and sometimes suppress the drying of ink by adding 1,4-cyclohexanedimethanol at the pen tip. It can be added as a material to further increase, but when the above-mentioned alcohols are added to an aqueous dispersion of the pigment (the pigment is suspended in an aqueous medium and then dispersed in fine particles using a disperser such as a bead mill). In such a case, an ink is prepared using only the above (1) regardless of the above (2), and a minimum amount of a hygroscopic organic solvent (glycerin, propylene glycol) is used. , Ethylene glycol, etc.) to ensure freezing of the ink. Incidentally, the "water medium of the pigment" generally contains about several% of a hygroscopic organic solvent in addition to a water-soluble polymer dispersant and a surfactant.

[0013]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. (Example 1) WM-Z color black 76.8% by weight (carbon black 13% aqueous dispersion, trade name, manufactured by Dainichi Seika Industry Co., Ltd.) (pigment content 10% by weight) Deltop 100 (preservative, Takeda) 0.2% by weight of 1,4-cyclohexanedimethanol 5.0% by weight and ion-exchanged water 18.0% by weight, and the mixture was stirred.
Was added with stirring. After the stirring was continued to confirm that was dissolved, coarse particles were removed by a centrifuge to obtain an aqueous black ink composition.

(Example 2) WM-Z color black 69.2% by weight (pigment content 9% by weight) Deltop 100 0.2% by weight 1,4-cyclohexanedimethanol 5.0% by weight Ethyl alcohol 6.0 % Of n-propyl alcohol 6.0% by weight of ion-exchanged water 13.6% by weight was added and dissolved, and the resulting solution was poured while stirring. When the whole became uniform, coarse particles were removed by a centrifuge to obtain an aqueous black ink composition.

Comparative Example 1 WM-Z Color Black 61.5% by weight (Pigment content 8% by weight) Deltop 100 0.2% by weight Ethylene glycol 10.0% by weight Glycerin 10.0% by weight Deionized water 18 Was mixed and dissolved, and the resulting solution was poured while stirring. When the whole became uniform, coarse particles were removed by a centrifuge to obtain an aqueous black ink composition. In Examples 1, 2 and Comparative Example 1, the pigment content was adjusted to 10 to 8% by weight in order to make the viscosity of the ink the same to some extent.

(Test Method) Each of the inks of Examples 1, 2 and Comparative Example 1 was filled into a batting (ink-absorbing body) with the ink in the same manner as a commercially available batting-type marking pen. , A tip, a tail plug, and a cap were fitted and left horizontally for one day to obtain a test sample.

Drying Resistance Test with Pen Tip (Evaluation of Drying Inhibiting Effect) Caps of a plurality of the test samples were removed, left horizontally, and handwritten on a writing paper at regular intervals, with no significant blurring. The maximum time during which the writing state was obtained was defined as "writable time".

Using the test sample, a line about 30 cm long is drawn by hand on Kent paper and glass. Lightly rub with an eraser in the direction perpendicular to the writing line at regular intervals, and the shortest time when the writing line does not scrape or extend is the "drying time of the writing line"
And

(Test Results) The test results are shown in Table 1.

[Table 1]

As is evident from the test results in Table 1, the "writable time" in Example 1 is significantly improved as compared with Comparative Example 1. On the other hand, with respect to the "writing line drying time", there is not so much difference in the "writing line drying time" when writing on Kent paper. However, the "drying time of the writing line" when writing on glass is much shorter in Example 1, and the effect of the invention (1) is remarkably exhibited. In this regard, when comparing Example 1 and Example 2 with respect to this point, Example 2 has a shorter "drying time of the writing line" than Example 1, and also has an effect of suppressing drying with the pen tip. It was further improved, and the effect of the invention (2) was demonstrated.

[0021]

According to the present invention, in order to obtain a predetermined drying suppression effect with a hygroscopic organic solvent, a considerably large amount of a hygroscopic organic solvent of 15 to 25% by weight had to be conventionally used. In many cases, it is still not possible to obtain a sufficient drying-suppressing effect in the ink that has been used, whereas according to the aqueous ink composition of the present invention, the amount of the ink is reduced to a necessary minimum to speed up the drying of the writing line. In the open nib portion, the 1,4-
The effect of suppressing drying as much as possible can be exhibited by the effect of cyclohexanedimethanol.

Claims (2)

[Claims] 1. An aqueous ink composition comprising at least a colorant, water and 1,4-cyclohexanedimethanol. 2. The aqueous ink composition according to claim 1, further comprising 5 to 20% by weight of at least one alcohol selected from ethyl alcohol, n-propyl alcohol and isopropyl alcohol.