JPH11349885A - Direct-fill ink for water-based ballpoint pens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ball-point pen direct filling ink which is excellent in dry-up resistance and prevents dripping of ink from a pen tip without causing fuzz and crying marks in handwriting. SOLUTION: A shear-thinning agent 0.2 to 0.8% by weight obtained by mixing 50 to 100 parts by weight of xanthan gum and 10 to 75 parts by weight of succinoglucan with respect to 100 parts by weight of a crosslinked acrylic acid polymer, It is a direct filling ink used for an aqueous ballpoint pen, comprising 2 to 10% by weight of a dye, 15 to 30% by weight of a moisturizing wetting agent, 3 to 10% by weight of urea, 1 to 7.5% by weight of sorbit, and the balance water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct filling ink used for an aqueous ballpoint pen.

[0002]

2. Description of the Related Art A water-based ball-point pen in which ink having a high viscosity in an ink cylinder and a low viscosity due to a shearing force caused by the rotation of a ball during writing has a good viscosity is provided directly in the ink cylinder. Is, for example,
No. 8673, Japanese Patent Publication No. 1-16437, U.S. Pat. S. P. 5
No. 013661 and the like. However, these inks have many technical problems.

[0003]

One of the main problems is that the water-soluble or dispersible resin used for imparting shear thinning to the ink has a very high molecular weight, and the water in the ink is evaporated. When doing so, the viscosity is significantly increased, or a film is formed at the pen tip to adversely affect the writing performance. In this regard, an ink using a crosslinked acrylic acid polymer having a relatively small ink thickening rate due to water evaporation and having no film-forming property as a shear-thinning agent was also disclosed by Japanese Patent Application Laid-Open No. 7-179804. These problems are minimized. However, the ink using the cross-linked acrylic acid polymer may not decrease the viscosity to a desired position due to the shearing force at the time of writing because the degree of shaking is small, and the handwriting may be crying, fuzzy, or When the ink viscosity is set with emphasis on the writing performance, the ink dripping performance from the pen tip tends to decrease. On the other hand, when a pigment is used as a coloring material, the fastness of handwriting is improved, but the dry-up resistance is significantly deteriorated. This is because if the water in the ink evaporates at the pen tip, the dispersion of the pigment is destroyed, so that the pigment particles at the pen tip are solidified and the ink is clogged. In addition, in the case of ink using a pigment, if the dispersion is broken, the ink does not redisperse even if water is resupplied again, and does not recover to a good state. As described above, an ink which has sufficient writing performance and excellent dry-up resistance and sufficiently satisfies the ink dripping performance from a pen tip has not yet been known. Due to such a problem, an aqueous ballpoint pen using an ink provided with shear thinning viscosity must always have a measure for preventing evaporation of water in the ink in the ballpoint pen structure, and in some cases, the pen point It was also necessary to use a special cap. The present invention clarifies what causes the problem and how the problem can be solved. An object of the present invention is to provide a direct filling ink for a water-based ball-point pen, which is excellent and can also be used in a capless ball-point pen which satisfies the ink dripping performance from the pen tip.

[0004]

The present invention provides: "1. 50 to 100 parts by weight of xanthan gum and succinoglucan 1 based on 100 parts by weight of a crosslinked acrylic acid polymer.
0 to 75 parts by weight of a shear-thinning agent 0.2
0.8% by weight, dye 2-10% by weight, moisturizing humectant 15
-30% by weight, urea 3-10% by weight, sorbit 1
A direct-fill ink used for aqueous ballpoint pens, consisting of 7.5% by weight and the balance water. 2. 1 to which 0.2 to 1.5% by weight of a rust preventive lubricant was added;
A direct-fill ink used for the water-based ballpoint pen described in the above item. 3. 1.0 to 6.0% by weight of a pH adjuster was added.
Item 6. A direct filling ink used for the water-based ballpoint pen according to item 2 or 2. 4. 4. A direct-fill ink used for the water-based ballpoint pen according to any one of Items 1 to 3, to which 0.1 to 1.0% by weight of a bactericidal agent is added. 5. Moisturizing moisturizer is dihydric alcohol, trihydric alcohol,
5. A direct-fill ink for use in an aqueous ballpoint pen according to any one of items 1 to 4, which is one or more selected from these alcohol derivatives. 6. 3. The direct-fill ink used in the water-based ballpoint pen according to item 2, wherein the rust preventive lubricant is one or more selected from a phosphate ester surfactant, benzotriazole, and a fatty acid ester. 7. 4. A direct-fill ink for use in an aqueous ballpoint pen according to item 3, wherein the pH adjuster is triethanolamine. About.

In the present invention, it is essential to use a crosslinked acrylic acid polymer, xanthan gum, and succinoglycan to form a ternary system in order to impart shear thinning to the viscosity structure of the ink. The crosslinked acrylic acid polymer does not remarkably thicken or form a film even when the water in the ink evaporates. However, there is a problem that the degree of fluctuation is small and it is difficult to reduce the ink viscosity to a desired viscosity at the time of writing and to maintain a high viscosity at rest. In addition, xanthan gum has a large degree of shaking, and when used in ink for ballpoint pens, it is easy to adjust the ink viscosity so that the ink does not hang down from the pen tip and gives good handwriting when writing, but water evaporation in the ink is easy. However, there is a problem that the dry-up resistance is reduced due to film formation due to the formation of a film, and xanthan gum alone cannot be used as a good ink. On the other hand, succinoglycan can give the ink a very large degree of thixability with a very small amount of addition. In this regard, the addition of a small amount minimizes the problem of dry-up due to evaporation of water in the ink, and it is easy to set the ink viscosity so that the ink dripping from the pen tip and the writing performance are both good. However, there is a drawback in that the ink lacks fluidity and thus lacks the ability to follow fast writing.

The present inventors have conducted intensive studies based on this situation, and have obtained the following findings. 1. In a binary system using a crosslinked acrylic acid polymer and xanthan gum simultaneously, both dry-up resistance and sagging performance cannot be improved. When the cross-linked acrylic acid polymer is used alone, the above-mentioned disadvantage that the thixotropic property is small occurs. To compensate for this drawback, use xanthan gum in combination and add xanthan gum until the viscosity is sufficient to prevent dripping of the ink, resulting in reduced dry-up resistance, and the amount of xanthan gum added is reduced to the extent that dry-up resistance is satisfied. In such a case, the ink dripping performance decreases. 2. In a binary system in which a crosslinked acrylic acid polymer and succinoglycan are simultaneously used, the ink followability is reduced due to lack of ink fluidity, and the fast writing performance is reduced. 3. In a binary system using xanthan gum and succinoglycan at the same time, the ink fluidity is further reduced, resulting in a drawback in fast writing performance. In addition, dry-up resistance is significantly reduced due to deposition and film formation at the time of ink drying at the pen tip. 4. When the cross-linked acrylic acid polymer and succinoglycan are used at the same time, the above-mentioned drawbacks occur, but when xanthan gum is added thereto, the dry-up resistance is also good and ink dripping from the pen tip does not occur, An ink with excellent writing performance was obtained. Originally, it was expected that the addition of xanthan gum having a relatively large thixotropic degree would further reduce the ink followability compared to the binary system of the crosslinked acrylic acid polymer and succinoglycan, but the result was unexpectedly very high. A good ink could be obtained. According to the results of intensive studies by the inventors, the relationship between these crosslinked acrylic acid polymers, succinoglycans and xanthan gum is such that the total amount of the three components is 0.2 to 0.8% by weight based on the total ink composition. %, The xanthan gum 50 to 100 based on the crosslinked acrylic acid polymer 100
It was found that various synergistic effects would improve various performances only in the case of 10% by weight of succinoglycan and 10 to 75% by weight of succinoglycan.

Next, the present invention employs a dye as a coloring material in the ink. When a pigment is used, the stability of the ink is destroyed due to the evaporation of water in the ink. When the ink is solidified, the original good dispersion state is not obtained even if the ink is supplied again. On the other hand, since the dye has resolubility, even if it is solidified with the pen tip, it has the characteristic of returning to the original good state again when the ink is supplied. In other words, when a dye is used as a coloring material, there is an advantage that even if the ink at the pen tip dries due to evaporation of water in the ink, the dried ink is re-dissolved when the ink is supplied, and the writing performance is not impaired.

In the present invention, it is necessary to add urea as an ink component. Urea has a function of dissolving the dye in addition to the action of suppressing the evaporation of water, and when the water in the ink evaporates and the dye is solidified, urea greatly functions as a dissolution aid for re-dissolving. That is, when a dye is used as a coloring material, a combination with urea greatly contributes to improvement in dry-up resistance. However, in the case of a combination with a pigment, it is difficult to add urea to the ink because of lack of ink stability. Also, since the pigment does not redisperse,
The function of urea cannot be fully utilized. As described above, in the ink using the dye, the addition of urea is particularly effective for improving the dry-up resistance.

The present invention also requires the addition of sorbite. Sorbit is rich in hygroscopicity and plays a major role in retaining water in ink. Further, since the viscosity increase due to ink dry-up is relatively low, it greatly contributes to maintaining the performance of ballpoint pens over time.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention is used for an aqueous ballpoint pen comprising a shear-thinning agent comprising a crosslinked acrylic acid polymer, xanthan gum and succinoglycan, water, a dye, a moisturizing wetting agent, urea and sorbit. It is a direct filling ink. The amount of the dye used is 2 to 10% by weight based on the total composition of the ink. If it is less than 2% by weight, the handwriting is faint and 10% by weight
Exceeding the limit causes hardening of the pen tip during ink dry-up, resulting in poor writing performance.

As the humectant, one or more selected from dihydric alcohols, trihydric alcohols and derivatives thereof are employed. Specific examples include ethylene glycol, polyethylene glycol, and glycerin, and one or more selected from these polyhydric alcohols. If the compounding amount of the moisturizing wetting agent is less than 15% by weight, the dry-up resistance is not good, and the ink hardens easily at the pen tip. On the other hand, if it exceeds 30% by weight, bleeding and crying are generated in the handwriting. Therefore, the compounding amount is 15% with respect to the whole ink composition.
３０30% by weight.

If the amount of urea used is less than 3% by weight, the moisture retention and dye re-dissolving performance are not good, and the dry-up resistance is not sufficient. On the other hand, if the content exceeds 10% by weight, urea crystals are precipitated during the evaporation of water, which is adversely affected. Therefore, the compounding amount is 3 to 10% by weight based on the whole ink composition. The amount of sorbitol used is 1 to 7.5% by weight based on the total ink composition. If it is less than 1% by weight, the moisturizing performance is lacking, and if it exceeds 7.5% by weight, the ink thickening rate increases due to the evaporation of water in the ink, and consequently the dry-up resistance decreases.

The amount of the shear thinning agent used is 0.2 to 0.8% by weight based on the total weight of the ink composition. 0.2% by weight
If the amount is less than 0.8%, the viscosity of the ink will not be sufficient to prevent ink dripping. If the amount exceeds 0.8% by weight, the resin content in the ink will increase. The dry-up resistance is significantly reduced due to precipitation or film formation with a pen tip. The composition ratio of the shear-thinning agent is 50 to 100% by weight of xanthan gum and 100% of succinoglycan based on 100 of the crosslinked acrylic acid polymer.
Must be 0-75% by weight. If the amount of xanthan gum is 50% by weight or less and the amount of succinoglycan is 10% by weight or less based on the crosslinked acrylic acid polymer, a desired ink viscosity cannot be obtained and ink dripping occurs. When xanthan gum is 100% by weight or more and succinoglycan 75% by weight or more, the ink dripping performance is good, but the dry-up resistance is significantly reduced. When the compounding ratio of xanthan gum is small and the compounding ratio of succinoglycan is too large, the ink followability is reduced, and when the compounding ratio of xanthan gum is too large and the compounding ratio of succinoglycan is small, the dry-up resistance is remarkable. Will decrease.

In addition, 0.2 to 1.5% by weight of a rust preventive lubricant, 1.0 to 6.0% by weight of a pH adjuster, and 0.1% by weight of a bactericide.
1-1.0% by weight can be added. The rust preventive lubricant is one or more selected from phosphate ester surfactants, benzotriazoles, and fatty acid esters. Examples of the pH adjuster include triethanolamine.

[0015]

Next, the present invention will be described with reference to examples. Example 1 Direct black 154 7.5% by weight Moisturizing moisturizer 20.0% by weight Urea 5.0% by weight Sorbit 3.0% by weight Rust preventive lubricant 1.0% by weight pH adjuster 2.0% by weight Bactericidal protection 0.5% by weight Crosslinked acrylic acid polymer 0.25% by weight Xanthan gum 0.15% by weight Succinoglycan 0.10% by weight Ion exchange water 60.5% by weight Ion exchange water 60.5% by weight, moisturizing and moisturizing 20.0% by weight of ethylene glycol as an agent is heated and mixed with a magnet hot stirrer at 60 ° C. Then 5.0% by weight of urea,
3.0% by weight of sorbitol, trade name Plysurf A-208S which is a phosphate ester surfactant as a rust preventive wetting agent
1.0% by weight (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 2.0% by weight of triethanolamine as a pH adjuster, 0.5% by weight of 1,2-benzoisothiazolin-3-one as a bactericide, and as a dye Direct Black 154 7.5% by weight was mixed and stirred in the same manner to completely dissolve. Next, as a crosslinked acrylic acid polymer, Hibiswako
104 (manufactured by Wako Pure Chemical Industries, Ltd.) 0.25% by weight, trade name Kerzan (manufactured by Sansho Co., Ltd.) as xanthan gum
0.10% by weight and 0.10% by weight of Meipoly (manufactured by Sansho Co., Ltd.) as succinoglycan were added, and mixed and stirred using a homogenizer stirrer until a uniform state was obtained to obtain a final ink. .

Examples 2 to 12 Direct-packing water-based inks for ballpoint pens were obtained in the same procedure as in Example 1 except that the formulations of the inks were as shown in Tables 1 and 2.

Comparative Example A directly packed water-based ballpoint pen ink was obtained in the same procedure as in Example 1 except that the composition of the ink was as shown in Tables 3 and 4.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

Tests and Evaluations The following tests were conducted on the inks for water-filled ball-point pens of Examples 1 to 12 and Comparative Example, and evaluated. Writing performance: も の indicates that the handwriting was particularly good without causing crying and scuffing of the handwriting, ○ indicates that the handwriting was practicable, △ indicates that it was slightly inferior, and X indicates that it was very poor. Dry-up resistance; left for 3 months in a 50 ° C., 30% RH environment with the ball-point pen cap removed. After standing, write a straight line with the refill which has been returned to room temperature.
Those that could be written out with m were rated as ○, those that could be written out with 5-10 cm were rated as Δ, and those that could not be written out more than 10 cm were rated as x. Ink dripping: Leave the pen tip downward for 2 hours in an environment of 30 ° C. and 80% RH, and confirm ink leakage from the pen tip. ◎ indicates that no sagging occurred, and ○ indicates that the pen tip was wet enough to cry,
An ink droplet generated at the pen tip was evaluated as x. Ink stability; leave the cap-off ballpoint pen in an environment of 50 ° C. and 0% RH. If no ink precipitates are generated in the ink for 3 months or more and the rate of change of the ink viscosity is within 30%, ◎ When no precipitate was generated in the ink for 2 to 3 months and the rate of change of the ink viscosity was within 30%,
When no precipitate was generated in the ink for 1 to 2 months and the rate of change of the ink viscosity was within 30%, it was marked as Δ, and when it was out of the stable condition within 1 month, it was marked as x. The evaluation results of each example and comparative example are as shown in Tables 1, 2 and 3.

Comparative Example 1 is an example in which the amount of the dye is too large. If the ink dries at the pen tip, it becomes a firm mass and causes poor writing. Therefore, the dry-up resistance is not good. In addition, since the thickener is not sufficiently lubricated and dispersed due to the influence of the dye, it is not possible to set an appropriate viscosity, which causes deterioration of writing performance and ink dripping. Comparative Example 2
Is an example in which the amount of the dye is small. In this case, not only the density of the handwriting is low and it is not practical, but also the effect of the thickener during drying of the ink is strong, which causes dry-up resistance and ink dripping. Comparative Example 3 is an example in which a pigment was used as a coloring material. Pigment inks are inferior in lubrication performance of the pen tip, so that writing feel and handwriting are not good. Further, the ink dripping performance is good due to severe drying and solidification, but the dry-up resistance is remarkably inferior because there is no redispersibility. Comparative Example 4 is an example in which the amount of the moisturizing wetting agent is too large. In this case, the dry-up resistance is of course good, but the drying at the pen tip does not contribute to the prevention of dripping, so that the ink dripping performance is not good.
Further, since the thickener does not swell and disperse sufficiently, it is not possible to set an appropriate viscosity, which causes deterioration of writing performance and ink dripping.

Comparative Example 5 is an example in which the amount of the moisturizing wetting agent is small. In this case, since the drying with the pen tip proceeds rapidly, the ink dripping performance is improved. However, as a matter of course, the dry-up resistance is remarkably deteriorated, and the ink wettability is poor, so that the writing performance is not good. Comparative Example 6 is an example in which the amount of urea is small. If the amount of urea is small, it is not possible to control the evaporation of water in the ink well, and the dry-up resistance is not good. In addition, due to the influence, crying and blurring are easily generated in the handwriting, and the writing performance is not good. Comparative Example 7 is an example in which the amount of urea is too large. In this case, ballpoint pen evaluation was not performed because urea crystals precipitated in the ink and were not stable as the ink. Comparative Example 8 is an example in which the blending amount of sorbite is small. Also in this case, as in the case where the blending amount of urea is small, the suppression of water evaporation in the ink cannot be controlled well, and the dry-up resistance is not good. In addition, due to the influence, crying and blurring are easily generated in the handwriting, and the writing performance is not good. Comparative Example 9 is an example in which the blending amount of sorbite is too large. A large amount of sorbitol is effective in suppressing the evaporation of water in the ink due to moisture absorption. The proper ink viscosity cannot be maintained. Therefore, not only the writing performance but also the writing performance is not good due to the remarkable thickening due to the evaporation of water. Further, although the viscosity increases, the drying at the pen tip is delayed due to the effect of suppressing the evaporation of water, so that the ink dripping performance is not good.

Comparative Example 10 is an example in which the amount of xanthan gum is extremely large and the amount of succinoglycan is small relative to the amount of the crosslinked acrylic acid polymer. In this case, the ink viscosity becomes too high, and the ink dripping performance is good, but the handwriting is blurred and the brush feel is heavy. Further, precipitation and film formation occur at the pen tip when the ink is dried, so that the dry-up resistance is significantly reduced.

Comparative Example 11 is an example in which the total amount of the shear thinning agent is small. In this case, no precipitation or film formation occurs at the pen tip, so that the dry-up resistance is good, but the desired ink viscosity is not obtained, so that good writing performance and ink dripping performance cannot be obtained. Comparative Examples 12 and 13 are examples in which the total amount of the shear-thinning agent was large. In this case, although the ink had a higher viscosity than appropriate, the ink dripping performance was good, but the handwriting was fuzzy and good writing was obtained. Performance cannot be obtained. Further, a strong dry residue is generated at the pen tip when the ink is dried, so that the dry-up resistance is significantly reduced.

Comparative Example 14 is an example in which the amount of xanthan gum is smaller than the amount of the crosslinked acrylic acid polymer and the amount of succinoglycan. In this case, since the compounding amount of succinoglycan is below the lower limit, the dry-up resistance is good, but the desired ink viscosity is not obtained, and good writing performance and ink dripping performance cannot be obtained. Comparative Example 1
5 is an example in which the amount of succinoglycan is smaller than the amount of the crosslinked acrylic acid polymer. In this case, as a result of increasing the amount of the cross-linked acrylic acid polymer and xanthan gum to the maximum, we succeeded in preventing ink dripping and borrowing performance at last, but for this reason the total amount of the shear thinning agent was increased and good writing performance was achieved. , Dry-up resistance could not be obtained.

Comparative Example 16 is an example in which the amount of xanthan gum is too large relative to the crosslinked acrylic acid polymer. The amount of succinoglycan was set as low as possible to improve the dry-up resistance, but the amount of xanthan gum was greater than that of the cross-linked acrylic acid polymer, so the cross-linked acrylic acid The effect of the coalescence on the dry-up resistance was reduced, and the dry-up resistance was not improved. In addition, although the writing performance was improved, the ink viscosity was not sufficient to prevent ink dripping because the amount of succinoglycan was intentionally set low.

Comparative Example 17 is an example in which the amounts of xanthan gum and succinoglycan are both smaller than the amounts of the crosslinked acrylic acid polymer. In this case, the viscosity was forced to be set by relying on the crosslinked acrylic acid polymer, so that the handwriting became crying and ink dripping occurred. Comparative Example 1
8 is an example in which the amounts of xanthan gum and succinoglycan are both too large with respect to the amount of the crosslinked acrylic acid polymer. In this case, it goes without saying that the ink dripping performance is improved, but the ink followability is lacking,
Drying resistance significantly decreases due to drying at the pen tip.

[0029]

The ink of the present invention has excellent dry-up resistance and prevents dripping of ink from a pen tip, and does not cause crying or blurring in handwriting.

Claims (7)

[Claims] 1. A shear-thinning agent obtained by mixing 50 to 100 parts by weight of xanthan gum and 10 to 75 parts by weight of succinoglucan with respect to 100 parts by weight of a crosslinked acrylic acid polymer. 2 to 10% by weight of a dye, 15 to 30% by weight of a moisturizing moisturizer, 3 to 10% by weight of urea, 1 to 7.5% by weight of sorbit, and the balance being water. 2. A direct-fill ink for use in an aqueous ball-point pen according to claim 1, further comprising 0.2 to 1.5% by weight of a rust preventive lubricant. 3. The direct-filling ink for use in an aqueous ballpoint pen according to claim 1, further comprising 1.0 to 6.0% by weight of a pH adjuster. 4. A direct-fill ink for use in an aqueous ball-point pen according to claim 1, further comprising 0.1 to 1.0% by weight of a bactericidal agent. 5. The aqueous ballpoint pen according to claim 1, wherein the moisturizing wetting agent is at least one selected from dihydric alcohols, trihydric alcohols, and derivatives of these alcohols. Direct filling ink to use. 6. A rust preventive lubricant selected from phosphate ester surfactants, benzotriazoles and fatty acid esters.
Or the direct filling ink used for the water-based ball-point pen of Claim 2 which is 2 or more. 7. The direct-fill ink for use in an aqueous ball-point pen according to claim 3, wherein the pH adjuster is triethanolamine.