JP2021084990A - Oil-based ink composition for writing instruments and writing instrument including the same - Google Patents

Abstract

To provide an oil-based ink composition for writing instruments that achieves improvement in start-of-writing performance and writing feel and achieves excellent ink stability with time, and a writing instrument including the same.SOLUTION: An oil-based ink composition for writing instruments contains a colorant, an organic solvent, and polyglycerol condensed fatty acid ester.SELECTED DRAWING: None

Description

The present invention relates to an oil-based ink composition for writing tools and a writing tool using the same.

In an oil-based ink composition for writing tools, if the tip tip is left in the air, the solvent in the ink evaporates and the colorant, resin, etc. dries and solidifies, causing handwriting blurring during writing during dry-up. There was a drawback that it would be done.

In order to improve the writing performance at the time of such dry-up, it has been considered to use various solvents and additives. For example, as a solvent containing a non-volatile organic solvent having a vapor pressure of 0.005 to 0.5 mmHg (20 ° C.) as a main solvent, Japanese Patent Application Laid-Open No. 6-247093 "Oil-based ballpoint pen" is disclosed and specified. As a solvent containing polyethylene glycol having a molecular weight of 200 to 4,000,000, Japanese Patent Application Laid-Open No. 7-196971 “Ink Composition for Oil-based Ballpoint Pen” is disclosed, which includes decamacademia nut oil fatty acid decaglyceryl and an alkyl group. The one containing at least a polyoxyethylene alkyl ether which has 16 or more carbon atoms and is solid at room temperature is disclosed in Japanese Patent Application Laid-Open No. 2008-88264 “Oil Ink Composition for Ballpoint Pen” and the like.

However, in Patent Document 1, when a non-volatile organic solvent having a vapor pressure of 0.005 to 0.5 mmHg (20 ° C.) is contained as the organic solvent, it has an effect of preventing the ink from completely drying, but handwriting. The drying property of the ink was poor, and it was not possible to satisfy the writing performance at the time of drying up by itself.

Further, in Patent Document 2, when polyethylene glycol having a specific molecular weight is contained as an additive, a resin film is formed on the tip of the chip to suppress further drying of the tip of the chip and increase the amount of ink in the chip. Although it is possible to improve the writing performance to some extent by suppressing the stickiness, since the resin film is hard, handwriting blurring occurs during writing during dry-up, and sufficient writing performance cannot be obtained. ..

Further, in Patent Document 3, it is possible to improve the writing performance to some extent by using the decamacademia nut oil fatty acid decaglyceryl and the polyoxyethylene alkyl ether in combination, but the lubricity is not sufficient and the writing quality is inferior. Furthermore, since a special surfactant is used, depending on the selection of colorants, organic solvents, other surfactants, etc., the stability of the ink over time will be affected, and dyes and other surfactants will be used. If it is not compatible with the above, precipitates will be generated, and problems that cause writing defects are likely to occur.

Further, in Patent Document 4, in order to improve the lubricity and the writing quality, in Japanese Patent Application Laid-Open No. 2007-176995, "Ink for oil-based ballpoint pen", as a new lubricant, N-acylamino acid, N- Although acylmethyltauric acid and N-acylmethylalanine were used, the writing resistance between the writing tip and the writing surface can be reduced to some extent, but the writing resistance is not sufficiently satisfactory and the writing performance is also satisfactory. Performance could not be obtained and there was room for improvement.

"Japanese Patent Laid-Open No. 6-247093" "Japanese Patent Laid-Open No. 7-196971" "Japanese Patent Laid-Open No. 2008-88264" "Japanese Patent Laid-Open No. 2007-176995"

There is a need for an oil-based ink composition for writing instruments that can satisfy both the writing performance at the time of dry-up and the writing taste, which cannot be satisfied by the above-mentioned Patent Documents 1 to 4. In particular, when a haunting type writing tool (oil-based ballpoint pen) such as a knock-type writing tool (oil-based ballpoint pen) or a rotary feeding type writing tool (oil-based ballpoint pen) is used, the writing performance is likely to be affected, which is important.
Furthermore, in recent years, in order to improve the writing quality with oil-based ballpoint pen ink, the viscosity of the ink has been reduced, and when writing with high writing pressure (high writing pressure resistance, writing load 300 to 500 gf). , The lubricity is easily affected, and the writing performance is easily affected by the wear of the ball seat. Therefore, in order to further reduce the writing resistance between the writing tip and the writing surface, it is required to further improve the lubricity and improve the high writing pressure resistance.

An object of the present invention is to obtain an oil-based ink composition for a writing tool, which improves writing performance and writing taste, and has good ink stability over time, and a writing tool using the same.

In order to solve the above problems, the present invention comprises "1. an oil-based ink composition for writing utensils, which comprises a colorant, an organic solvent, and a polyglycerin condensed fatty acid ester.
2. The oil-based ink composition for writing tools according to item 1, wherein the content of the polyglycerin condensed fatty acid ester is 0.1 to 10% by mass with respect to the total amount of the ink composition.
3. 3. The oil-based ink composition for stationery according to item 1 or 2, wherein the organic solvent is an aromatic alcohol.
4. The oil-based ink composition for writing tools according to any one of Items 1 to 3, wherein the ink viscosity at 20 ° C. and a shear rate of 5 sec ^{-1 is 30,000 mPa · s or less.}
5. A writing tool comprising the oil-based ink composition for writing tools according to any one of paragraphs 1 to 4.
6. A ballpoint pen tip that rotatably holds a ball is provided at the tip of the ink containing cylinder, and the oil-based ink composition for writing instruments according to any one of items 1 to 4 is placed in the ink containing cylinder. An oil-based ballpoint pen that is characterized by being housed. ".

According to the present invention, the film formed by the resin and polyglycerin condensed fatty acid ester contained in the ink is easily peeled off, thereby improving the writing performance and at the same time, even during writing (when the ball is rotated). By reducing the writing resistance (rotational resistance of the ball) at the tip of the writing, the writing quality is improved, and since it is difficult to show ionicity, the oil-based ink composition for writing tools and the ink composition having good stability over time. I was able to obtain a writing instrument using it.

Hereinafter, embodiments of the present invention will be described in detail. In the present specification, "part", "%", "ratio", etc. indicating the composition are based on mass unless otherwise specified, and the content is a constituent component based on the mass of the ink composition. Is the mass% of.

A feature of the present invention is to prepare an oil-based ink composition for writing utensils containing a polyglycerin condensed fatty acid ester. This is because when the tip of the chip is dried, the film formed by the resin and polyglycerin condensed fatty acid ester contained in the ink at the tip of the chip is a stable, uniform and brittle film, which is easily peeled off. , While improving the writing performance, at the same time, even during writing (when the ball is rotating), the coating is brittle, so the writing resistance (rotational resistance of the ball) at the tip of the writing is reduced compared to the past, so that the writing taste is improved. Can be improved.
Furthermore, by forming a lubricating layer by containing polyglycerin condensed fatty acid, the lubricity between the writing tip and the writing surface (including the lubricity between the ball and the tip body) is maintained. , The writing resistance (rotational resistance of the ball) at the tip of writing can be suppressed to improve the writing quality. Therefore, the writing resistance (ball rotation resistance) of the writing tip due to the brittle coating formed as described above is reduced, and the writing resistance (ball) of the writing tip is formed by forming the lubricating layer. It is effective because the writing quality can be improved by the synergistic effect of reducing (rotational resistance). In particular, in the case of a ballpoint pen, the ballpoint pen tip made of a metal material is effective because it is easily adsorbed on the metal surface, a lubricating layer is easily formed, and the writing quality can be further improved.
Further, the polyglycerin condensed fatty acid is less likely to exhibit ionicity, is less likely to generate precipitates due to other components in the ink, and can improve the stability of the ink with time.
Therefore, as described above, it is possible to improve all of the writing performance, writing taste, and ink stability over time.

(Polyglycerin condensed fatty acid ester)
In the present invention, the polyglycerin condensed fatty acid ester is obtained by further ester-bonding an ester obtained by condensing the fatty acids with a fatty acid having one hydroxyl group and polyglycerin obtained by polymerizing glycerin.

Examples of the polyglycerin constituting the polyglycerin condensed fatty acid ester used in the present invention include those having an average degree of polymerization of 2 to 15, specifically, diglycerin (average degree of polymerization 2) and triglycerin (average degree of polymerization 3). ), Tetraglycerin (average degree of polymerization 4), hexaglycerin (average degree of polymerization 6), octaglycerin (average degree of polymerization 8), decaglycerin (average degree of polymerization 10), etc. It works favorably on moisture absorption and at the same time easily suppresses thickening of ink at the tip of the chip, so it tends to be advantageous in writing performance. Therefore, it is difficult to exert the effect of writing performance, so that the average degree of polymerization is preferably 3 to 12. Considering the writing performance, the average degree of polymerization is preferably 4 to 10, and further preferably the average degree of polymerization is 4 to 8.

The polyglycerin condensed fatty acid ester preferably has an HLB value of 10 or less in consideration of further improving both writing performance and lubricity. This is because when the HLB value is 10 or less, the lipophilicity tends to be strong, which is effective in the present invention. Further, when the HLB value is 5 or less, when the tip tip is dried, the formed film tends to be a stable, uniform and brittle film and easily peels off, so that the writing performance can be easily improved and the writing tip can be easily peeled off. It is preferable because it is easy to suppress the writing resistance (rotational resistance of the ball) and improve the writing quality, and more preferably, the HLB value is 0.3 to 5. The HLB can be obtained by the Griffin method or the like.
In particular, unlike cap-type ballpoint pens, infested ballpoint pens such as knock-type ballpoint pens and rotary-feed-out type ballpoint pens, the pen tip is always exposed to the outside, which affects the writing performance of the writing tip when it dries. Since it is easy, it is more preferable to use the polyglycerin condensed fatty acid ester having the above HLB value.

In addition, the fatty acids constituting the polyglycerin condensed fatty acid ester should have an appropriate length of carbon atoms in order to exert the above-mentioned effects in consideration of improving writing performance and writing quality. It is preferable to use a fatty acid having 12 to 20 carbon atoms, and more preferably, a fatty acid having 16 to 20 carbon atoms is preferably used. Specifically, polyglycerin-condensed ricinol acid ester and polyglycerin-condensed stearic acid ester are preferable, but in consideration of improving writing performance and writing quality and improving ink stability over time, polyglycerin-condensed ricinol is preferable. It is preferable to use an acid ester.
Specific examples of the polyglycerin condensed ricinoleic acid ester include Poem PR-100, Poem PR-300 (manufactured by Riken Vitamin Co., Ltd.), SY Glycer CR-310, CR-500, and CR-ED (Sakamoto Yakuhin Kogyo Co., Ltd.). ), Sunsoft 818SK (manufactured by Taiyo Kagaku Co., Ltd.) and the like.

The content of the polyglycerin condensed fatty acid ester is more preferably 0.1 to 10% by mass with respect to the total amount of the ink composition. This is because if it is less than 0.1% by mass, it is difficult to obtain the desired writing performance and writing taste, and if it exceeds 10% by mass, the ink aging tends to become unstable, and this tendency is taken into consideration. Therefore, it is preferably 0.3 to 5% by mass, and more preferably 0.5 to 3% by mass, based on the total amount of the ink composition.

(Organic solvent)
Examples of the organic solvent used in the present invention include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and diethylene glycol dimethyl ether, 3. Glycol ether solvents such as −methoxybutanol and 3-methoxy-3-methylbutanol, glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol and ethylene glycol, benzyl alcohol, methanol and ethanol. , 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butin-3-ol, ethylene glycol monomethyl ether acetate and other higher alcohols. Examples thereof include organic solvents generally used as inks for writing tools, such as alcohol solvents.

Among these organic solvents, aromatic alcohol has an aromatic ring to improve lubricity, and is easily dissolved and stable with polyglycerin condensed fatty acid ester and polyoxyalkylene glyceryl ether described later, so that aromatic alcohol is aromatic. It is preferable to use a group alcohol solvent.
In addition, when a glycol ether solvent is used, it easily absorbs moisture, so that the strength of the film formed when the tip of the chip dries is softened and the writing performance is easily improved. When the polyoxyalkylene glyceryl ether described later is used, it is more effective, and considering the stability in the ink, it is preferable to use the aromatic glycol ether solvent.

Further, the content of the organic solvent is preferably 10 to 90% by mass with respect to the total amount of the ink composition in consideration of improving solubility, lubricity, handwriting drying property, etc., and more considered, 20 to 90%. It is preferably by mass, more preferably 40 to 70% by mass.

(Colorant)
The colorant used in the present invention is not particularly limited to dyes, pigments and the like, and can be appropriately selected and used, and dyes and pigments may be used in combination. Examples of dyes include oil-soluble dyes, acidic dyes, basic dyes, gold-containing dyes, and various salt-forming type dyes such as salt-forming dyes of acidic dyes and basic dyes, basic dyes and organic acids. Types such as salt-forming dyes with and salt-forming dyes with acidic dyes and organic amines can be mentioned. These dyes may be used alone or in combination of two or more.

Further, as the colorant, it is preferable to use a pigment in consideration of lubricity. This is because the pigment particles enter the gap between the ball and the chip body, so that the action like a bearing easily works and metal contact is formed. It is preferable to use a pigment because it is easy to obtain the effect of improving the lubricity, improving the writing quality, and suppressing the wear of the ball bearing by suppressing it. Further, the pigment is preferable because it has excellent water resistance and light resistance and good color development can be obtained.

Examples of pigments include inorganic, organic, and processed pigments. Specifically, carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine, azo, quinacridone, and diketo. Examples thereof include pyrrolopyrrole-based, quinophthalone-based, slene-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, metallic pigments, pearl pigments, fluorescent pigments, phosphorescent pigments and the like.

Further, as the colorant, it is preferable to use a pigment in consideration of lubricity. This is because the pigment particles enter the gap between the ball and the chip body, so that the action like a bearing easily works and metal contact is formed. It is preferable to use a pigment because it is easy to obtain the effect of improving the lubricity, improving the writing quality, and suppressing the wear of the ball bearing by suppressing it. Further, the pigment is preferable because it has excellent water resistance and light resistance and good color development can be obtained.

When a dye is used, it is preferable to use a salt-forming dye in consideration of the stability over time due to compatibility with the polyoxyalkylene glyceryl ether, and the stability over time can be maintained because the salt-forming bond is stable. Considering this, it is preferable to use from among salt-forming dyes of basic dyes and organic acids, salt-forming dyes of acidic dyes and basic dyes, and salt-forming dyes of acidic dyes and organic amines. Considering the stability with the components in the ink, a salt-forming dye containing a basic dye and an organic acid is preferable.

The content of the colorant is preferably 5 to 30% by mass with respect to the total amount of the ink composition. This is because if it is less than 5% by mass, it tends to be difficult to obtain a dark handwriting, and if it exceeds 30% by mass, it tends to affect the solubility in the ink and the stability over time of the ink. In consideration of the above, 7 to 25% by mass is preferable, and further considering, 10 to 20% by mass is more preferable.

When the polyglycerin condensed fatty acid ester is contained as in the present invention, it is preferable that the organic solvent having a solubility parameter (SP value) of 16 to 30 is further contained in addition to the organic solvent. This makes it easier to obtain a surface active effect in which the polyglycerin condensed fatty acid ester gathers at the interface between the highly polar organic solvent and the low polar polyglycerin condensed fatty acid ester, which is an effect of the present invention. This is because it is easy to suppress wear of the ball seat and improve writing performance under writing pressure, and more consideration is given to the solubility parameter (SP value) of 16 to 27.
In particular, when the HLB value is set low, specifically, when a polyglycerin condensed fatty acid ester having an HLB value of 10 or less is used, an organic solvent within the range of the solubility parameter (SP value) as described above is used. It is effective because it becomes easier to obtain the above-mentioned surface active effect, and it is easy to suppress wear of the ball seat and improve the writing performance under high writing pressure, which is the effect of the present invention. A polyglycerin condensed fatty acid ester having an HLB value of 5 or less is preferable. Further, regarding the organic solvent which is in the range of the solubility parameter (SP value) as described above, in the case of a ballpoint pen, it is easy to be adsorbed on the metal surface in the ballpoint pen tip of a metal material, and a lubricating layer is easily formed. Effective because it can improve the taste,
The SP value in the present invention means the solubility parameter (SP value) of the organic solvent and is a value represented by the square root of the molecular aggregation energy. The SP value is described in Chapter IV, Solubility Parameter Values of Polymer HandBook (Second Edition), and the value is used as the SP value in the present invention. The unit is (MPa) ^1/2 , which indicates a value at 25 ° C.

Examples of the organic solvent having a solubility parameter (SP value) of 16 to 30 include polyoxyalkylene glyceryl ether, alkylene glycol alkyl ether, and alkylene glycol, but consideration is given to further improving both writing performance and lubricity. Therefore, it is preferable to use polyoxyalkylene glyceryl ether. The polyoxyalkylene glyceryl ether is obtained by addition polymerization of alkylene oxide to glycerin or polyglycerin, and examples thereof include polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, and polyoxyalkylene triglyceryl ether.
The polyoxyalkylene glyceryl ether is a compound having an alkylene oxide in its structure and having hydrophilicity and lipophilicity. By having a highly polar hydrophilic group in the structure, in the case of a ballpoint pen, it becomes easy to be adsorbed on the metal material of the ballpoint pen tip, and by forming a lubricating layer, the lubricity can be further improved. Even under the pressure (writing load 300 to 500 gf), it is possible to suppress the wear of the ball seat and improve the writing quality. Further, by using the polyglycerin condensed fatty acid ester and the polyoxyalkylene glyceryl ether used in the present invention in combination, they have a glycerin skeleton in each other's structure and form a more effective lubricating layer, so that the lubricity is further improved. It is preferable because it is easy to do.
Further, since the polyoxyalkylene glyceryl ether is hard to evaporate, it is easy to improve the writing performance even when the writing tip is left in the air. In particular, the polyglycerin condensed fatty acid ester and the polyoxyalkylene glyceryl ether used in the present invention can be used. When used in combination, it is preferable because it improves hygroscopicity and at the same time easily suppresses thickening due to ink evaporation at the tip of the chip, and it is easy to obtain a synergistic effect in terms of writing performance.
Further, the polyoxyalkylene glyceryl ether is preferable because it has a glycerin skeleton like the polyglycerin condensed fatty acid ester used in the present invention and is stable in the ink, so that the ink time is easily stabilized. ..

As described above, the polyoxyalkylene glyceryl ether is preferable because it easily suppresses evaporation and can improve the ink followability by suppressing the ink thickening of the oil-based ink composition for writing tools as much as possible. Further, when a pigment is used as a colorant, the ink viscosity generally increases with time due to the aggregation of the pigment and the ink followability decreases, but the polar group in the structure of the polyoxyalkylene glyceryl ether is the pigment surface. Since the pigment is stably dispersed in the oil-based ink, the ink followability can be improved by suppressing the increase in the ink viscosity due to the aggregation of the pigment.
Further, the polyoxyalkylene glyceryl ether includes polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, etc., but by having a propylene group, it is excellent in lipophilicity, and by suppressing moisture absorption of the ink, the ink can be used over time. It is preferable to use polyoxypropylene glyceryl ether because it is stable.

Considering that polyoxyalkylene glyceryl ether suppresses wear of the ball seat under high writing pressure (writing load 300 to 500 gf), improves writing quality, and further improves writing performance and ink aging stability due to ink absorption. , The average number of moles of alkylene oxide added ((m + n + o + p), (w + x + y + z)) is preferably 1 to 50. Considering the stability of ink with time due to ink absorption, the average number of moles of alkylene oxide added is 1 to 30. The average number of moles of alkylene added is 5 to 20 in consideration of suppressing wear of the ball seat under high writing pressure, improving writing quality, and improving writing performance and ink stability over time. Is preferable.
In particular, considering the suppression of wear of the ball seat under high writing pressure, the average number of moles of propylene oxide added (m + n + o + p) is preferably 1 to 30, and more considered, the average number of moles of propylene oxide added is 5 to 5. It is preferably 20 and preferably 8 to 16. Further, considering that the effect of the present invention is easily exhibited, the structure of the polyoxyalkylene glyceryl ether is preferably a structure of (Chemical formula 1) or (Chemical formula 2), and the ink with time due to ink absorption is more preferable. Considering the stability, the structure of (Chemical formula 1) is preferable.

The average weight molecular weight of the polyoxyalkylene glyceryl ether is preferably 5000 or less. If the average weight molecular weight is too large, the hygroscopicity tends to increase, which affects the ink stability over time in the oil-based ink. This is because the ink is likely to come out, the ink viscosity is likely to be high, and the ink followability is likely to be affected. Considering the stability of the ink over time and the ink followability, the average weight molecular weight is preferably 3000 or less, and the average weight molecular weight is preferably 1500 or less, preferably 1200 or less. On the other hand, if the average weight molecular weight is too small, the wear suppression, writeability, and pigment dispersibility of the ball seat under high writing pressure are likely to be affected. Therefore, the average weight molecular weight is preferably 300 or more, under higher writing pressure. Considering the suppression of wear of the ball seat, the average weight molecular weight is preferably 500 or more.
The weight average molecular weight is a value obtained in terms of polystyrene using GPC (gel permeation chromatography).

Further, when the content of the polyoxyalkylene glyceryl ether is less than 0.1% by mass with respect to the total amount of the ink composition, wear suppression of the ball seat under high writing pressure as described above, writing taste, writing performance, and the like. The effect of ink followability may not be obtained, and if it exceeds 40% by mass, it may affect the stability over time of the ink and ink leakage. Therefore, 0.1 to 40% by mass is added to the total amount of the ink composition. Preferably, 3 to 30% by mass is preferable in consideration of the above effects, and 5 to 25% by mass is preferable, and 5 to 25% by mass is most preferable in consideration of the balance between the suppression of wear of the ball seat and the stability with time of the ink. It is 8 to 25% by mass.

In the present invention, the compounding ratio of polyoxyalkylene glyceryl ether to polyglycerin condensed fatty acid ester (polyoxyalkylene glyceryl ether / polyglycerin condensed fatty acid ester) is preferably 1 to 25 times by mass, and 3 to 20 times. It is more preferably doubled, and most preferably 5 to 12 times. This is because, within the above range, it is possible to suppress wear of the ball seat and improve writing quality, writing performance, and ink followability in a well-balanced manner.

(resin)
Further, in order to further improve the suppression of ink leakage, it is preferable to use a resin as an ink viscosity modifier. As the resin, polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, etc. Examples thereof include alkyd resin, phenoxy resin, and polyvinyl acetate resin, and among them, polyvinyl butyral resin or ketone resin is preferably contained.

For polyvinyl butyral resin, it is easy to form a lubricating layer that can obtain a higher lubricating effect. This is because when the polyvinyl butyral resin is used, an elastic ink layer is always formed between the balls and the ball seats to make it difficult to make direct contact with each other, so that it is easy to improve the writing quality and the polyglycerin condensed fatty acid ester. , A higher lubricating effect can be easily obtained due to the synergistic effect of the lubricating layer formed by the combined use with the polyoxyalkylene glyceryl ether. Further, when the polyvinyl butyral resin is used, it is preferable because the film formed makes it easier to improve ink leakage, and when a pigment is used as a colorant, a pigment dispersion effect can be obtained. Therefore, the polyvinyl butyral resin is used. It is preferable to use it.
Here, the polyvinyl butyral resin is obtained by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure having a butyral group, an acetyl group, and a hydroxyl group.

The polyvinyl butyral resin preferably has a hydroxyl group content of 25 mol% or more. This is because polyvinyl butyral resin with a hydroxyl group content of less than 25 mol% does not have sufficient solubility in an organic solvent, and it is difficult to obtain a sufficient lubricating effect and an effect of suppressing ink leakage. Then, it is preferable to use a polyvinyl butyral resin having a hydroxyl group content of 25 mol% or more. Further, the polyvinyl butyral resin having a hydroxyl group content of 30 mol% or more is preferable because the writing quality is easily improved. This is because at the time of writing, frictional heat is generated by the rotation of the ball, which warms the ink at the tip of the chip and raises the temperature of the ink, but the polyvinyl butyral resin is different from other resins. Even if the ink temperature rises, it has the property of making it difficult for the ink viscosity to decrease, and an elastic ink layer is always formed between the ball and the ball seat to make it difficult to make direct contact, improving the writing quality. It tends to be easy. In particular, ballpoint pens are effective for oil-based ballpoint pens because they often write with high writing pressure. Further, when a polyvinyl butyral resin having a hydroxyl group content of more than 40 mol% is used, the amount of moisture absorbed tends to increase and the stability with time with the ink component tends to be affected. Therefore, a polyvinyl butyral resin having a hydroxyl group content of 40 mol% or less is preferable. Therefore, a polyvinyl butyral resin having a hydroxyl group content of 30 to 40 mol% is preferable, and a hydroxyl group content of 30 to 36 mol% is more preferable.
The amount of hydroxyl groups (mol%) of the polyvinyl butyral resin is the content of hydroxyl groups (mol%) with respect to the total amount of mol of butyral groups (mol%), acetyl groups (mol%), and hydroxyl groups (mol%). It shows the rate.

Regarding the average degree of polymerization of the polyvinyl butyral resin, when the average degree of polymerization is 200 or more, the ink leakage suppression performance is likely to be improved, and when the average degree of polymerization exceeds 2500, the ink viscosity becomes too high. The average degree of polymerization is preferably 200 to 2500 because it tends to affect the writing quality. Further, more consideration is given, the average degree of polymerization is preferably 1500 or less, and the average degree of polymerization is 200 to 1000, considering the mutual lubrication effect with the polyglycerin condensed fatty acid ester and the polyoxyalkylene glyceryl ether. Is preferable. Here, the average degree of polymerization refers to the number of basic units constituting one molecule of polyvinyl butyral resin, and a value measured based on the method specified in JIS K6728 (2001 version) can be adopted. ..

The content of the polyvinyl butyral resin is 50% or more with respect to the content of the total resin in the oil-based composition for oil-based ballpoint pens, and it is preferable to use it as the main resin. This is because when the content of the polyvinyl butyral resin is less than 50% of the content of the total resin, it is easy for other resins to hinder the formation of an elastic ink layer, which has the effect of improving the writing quality. It becomes difficult to obtain, and it is easy to inhibit the formation of the resin film at the tip of the chip, the ink dripping cannot be suppressed, and the formation of an elastic ink layer is inhibited, so that the effect of improving the writing quality is obtained. This is because it becomes difficult to get rid of. Considering the tendency to improve the writing taste and the ink dripping performance, the content of the polyvinyl butyral resin is preferably 70% or more, preferably 90% or more, based on the total resin content.

If the content of the resin is less than 1% by mass with respect to the total amount of the ink composition, the desired lubricity and ink leakage suppressing performance are likely to be inferior, and if it exceeds 40% by mass, the solubility in the ink is likely to be inferior. , 1 to 40% by mass is preferable with respect to the total amount of the ink composition. Further, considering it, 5% by mass or more is preferable, and if it exceeds 30% by mass, the ink viscosity tends to be too high and affects the writing taste. Therefore, 5 to 30% by mass is preferable, and 10% by mass is more considered. ~ 25% by mass is preferable.

In the present invention, the lubricity of the writing tip (ballpoint pen and ballpoint pen) is improved to improve the writing quality, and the writing tip is left in the air for a longer period of time to write when the writing tip dries. Considering that the performance (long-time writing performance) is improved and that the rust preventive effect can be easily obtained when the ballpoint pen tip and the ink container are made of a metal material, a phosphate ester-based surfactant is further included. Is preferable.
This is because the phosphate ester-based surfactant has a phosphate group, so that in the case of a ball pen, it is easily adsorbed on the metal surface of the ball pen tip, and in particular, a lubricating layer is formed between the ball and the ball seat. Therefore, the phosphoric acid ester-based surfactant can improve the writing performance for a longer period of time than the polyglycerin condensed fatty acid ester while improving the lubricity and the writing quality. Therefore, when a phosphoric acid ester-based surfactant is used in combination with a polyglycerin condensed fatty acid ester or a polyoxyalkylene glyceryl ether, both lubrication actions work to synergistically improve the lubricity between the balls and the locus. It can be improved and brings a smooth writing taste. Furthermore, the phosphoric acid ester-based surfactant also has the effect of improving the writing performance, and when used in combination with the polyglycerin condensed fatty acid ester or the polyoxyalkylene glyceryl ether, the writing performance can be further improved. A rust preventive effect can also be obtained.
Therefore, in the present invention, it is effective to use a phosphoric acid ester-based surfactant in combination with a polyglycerin condensed fatty acid ester or a polyoxyalkylene glyceryl ether.
Further, in the present invention, when polyvinyl butyral is used, the use of a phosphoric acid ester-based surfactant further improves the lubricity by the lubricating layer made of polyvinyl butyral and the lubricating layer made of a phosphoric acid ester-based surfactant. Easy, effective and preferable.

The HLB value of the phosphoric acid ester-based surfactant is preferably 6 to 14, in consideration of further improving both lubricity and writing performance. This is because when the HLB value exceeds 14, the hydrophilicity tends to be strong and the solubility in the ink tends to be inferior, so that the effect of the phosphoric acid ester-based surfactant is difficult to obtain, and in particular, the lubricating effect is difficult to obtain. Because. On the other hand, if the HLB value is less than 6, the lipophilicity becomes too strong, the compatibility with the organic solvent is likely to be affected, the stability over time of the ink is difficult to obtain, and the writing performance is difficult to improve. Further, considering the lubricity, the HLB value is preferably 12 or less, the HLB value is preferably 6 to 12, and more considering the writing performance, the HLB value is preferably 7 to 12. In particular, unlike cap-type ballpoint pens, infested ballpoint pens such as knock-type ballpoint pens and rotary-feed-out type ballpoint pens, the pen tip is always exposed to the outside, which affects the writing performance of the writing tip when it dries. It is more preferable to use a phosphate ester-based surfactant having the above HLB value because it is easy to use. The HLB can be obtained from the Griffin method, the upstream method, or the like.

Examples of the phosphoric acid ester-based surfactant include _{a phosphoric acid ester having an alkoxy group (Ca} H _{2a + 1} O), a polyoxyethylene alkyl ether or a phosphoric acid monoester of a polyoxyethylene alkyl aryl ether, a polyoxyethylene alkyl ether or a poly. Examples thereof include a phosphoric acid diester of an oxyethylene alkylaryl ether, a phosphoric acid triester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, an alkyl phosphoric acid ester, an alkyl ether phosphoric acid ester or a derivative thereof.

When a phosphoric acid ester-based surfactant is used, the acid value is preferably 150 or less, in order to facilitate the improvement of lubricity by the phosphoric acid ester-based surfactant. The acid value is preferably 30 to 120 in consideration of stability and lubricity in the ink, and more preferably 70 to 120 in consideration of the acid value. The acid value is contained in 1 g of the sample. It shall be represented by the number of mg of potassium hydroxide required to neutralize the acidic component.

In the present invention, it is preferable to use an organic amine in consideration of the stability of the ink component in the ink. Amines having ethylene oxide such as oxyethylenealkylamine and polyoxyethylenealkylamine, alkylamines such as laurylamine and stearylamine, dimethylalkylamines such as distearylamine, dimethyllaurylamine, dimethylstearylamine and dimethyloctylamine, etc. Among them, amines having ethylene oxide and dimethylalkylamines are preferable in consideration of stability in ink, and dimethylalkylamines are preferable in further consideration.

Regarding the reactivity of the organic amine with other components in the ink, the primary amine is the strongest, followed by the secondary amine and the tertiary amine, and the reactivity is smaller. It is preferable to use a secondary amine or a tertiary amine. These may be used alone or in admixture of two or more.

In addition, as a viscosity modifier, a pseudoplasticizing agent such as fatty acid amide or hydrogenated castor oil may be used, and a colorant stabilizer, a plasticizer, a chelating agent or the like may be appropriately used. These may be used alone or in combination of two or more.

The ink viscosity of the oil-based ink composition for writing tools of the present invention is not particularly limited, but ^{when the ink viscosity at 20 ° C. and a shear rate of 5 sec -1} (at rest) exceeds 30,000 mPa · s, writing performance and writing are performed. Since the taste and ink followability are likely to be inferior, ^{the ink viscosity at 20 ° C. and a shear rate of 5 sec -1} (at rest) is preferably 30,000 mPa · s or less. Further, if the ink viscosity at 20 ° C. and a shear rate of 5 sec ^-1 (at rest) is less than 1000 mPa · s, it is difficult to suppress ink leakage, so it is preferably 1000 mPa · s or more. The ink viscosity is more preferably 1000 to 25000 mPa · s in consideration of further improving ink leakage suppression, writing taste, ink tracking performance, and writing performance, and further considering writing taste and writing performance, 2000 to 2000. 20000 mPa · s is preferable.

(Stationery)
The oil-based ink composition for writing instruments according to the present invention can be applied to various writing instruments, and there are oil-based ballpoint pens, oil-based marking pens, etc., but it is preferable to use it for oil-based ballpoint pens, which can easily exert the effects of the present invention. It is preferable to use it for a hit-and-miss type ballpoint pen such as a knock type or a rotary feeding type. Such a ballpoint pen includes a storage cylinder containing the oil-based ink composition according to the present invention, and a ballpoint pen tip arranged at the tip of the storage cylinder and rotatably holding a ball in a ball holding chamber. Is. The ballpoint pen tip can be retracted from the tip opening of the shaft cylinder, and has a structure generally called a retractable ballpoint pen. Generally, when the ink composition is used for a haunting ballpoint pen whose pen tip is not sealed, the tip tip is constantly left in the air, so that the tip tip dries and blurring is likely to occur during writing. , The composition according to the present invention is preferable because such a problem is improved.

(Ballpoint pen tip)
The arithmetic mean roughness (Ra) of the ball surface of the ballpoint pen tip used in the present invention is preferably 0.1 to 12 nm. This is because if the arithmetic mean roughness (Ra) is less than 0.1 nm, it is difficult for ink to be sufficiently applied to the ball surface, it is difficult to obtain a dark handwriting when writing, and lines are likely to be skipped and blurring is likely to occur in the handwriting. If the roughness (Ra) exceeds 12 nm, the surface of the ball is too rough and the rotation resistance between the ball and the ball seat is large, so that the ball seat is likely to be worn and the writing quality is inferior. This is because the writing performance such as unevenness is likely to be affected. Further, when the arithmetic mean roughness (Ra) is 0.1 to 10 nm, when an ink composition as in the present invention is used, it is more preferable because the writing quality is improved and the ink is easily placed on the ball surface. Considering the writing taste, 2 to 8 nm is preferable. The surface roughness can be measured by (model name SPI3800N manufactured by Seiko Epson Corporation).

The material used for the balls is not particularly limited, but is limited to cemented carbide balls containing tungsten carbide as a main component, metal balls such as stainless steel, and ceramics such as silicon carbide, silicon nitride, alumina, silica, and zirconia. Examples include balls and ruby balls.

The material of the ball pen tip includes metal materials such as stainless steel, nickel silver, brass (brass), aluminum bronze, and aluminum, and resin materials such as polycarbonate, polyacetal, and ABS. Considering the property, it is preferable to use a stainless steel chip body.

(Example)
Next, the present invention will be described with reference to examples.
The oil-based ink composition for writing instruments of Example 1 was prepared by adding an organic solvent, a pigment, and a pigment dispersant in advance and dispersing them with a three-roll disperser to prepare a pigment dispersion. Then, a pigment dispersion, an organic solvent, a polyglycerin condensed fatty acid ester, polyvinylpyrrolidone, and polyvinyl butyral resin are used, weighed in a predetermined amount, heated to 60 ° C., and completely dissolved using a disperser stirrer. An oil-based ink composition for writing utensils was obtained. The specific blending amount is as follows.
The ink viscosity of Example 1 was measured at a ^{shear rate of 5 sec -1} (rotation speed 2.5 rpm) in an environment of 20 ° C. using a viscometer Viscometer RVDVII + Pro CP-52 spindle manufactured by Brookfield Co., Ltd. The ink viscosity was 3000 mPa · s.

Example 1
Pigment dispersion (containing 20% pigment, 20% polyvinyl butyral) 20.0% by mass
Alcohol solvent (benzyl alcohol) 76.5% by mass
Polyglycerin condensed fatty acid ester (hexaglycerin ester: average degree of polymerization 6, constituent fatty acids: ricinol (18 carbon atoms)) 2.0% by mass
Polyvinylpyrrolidone 0.5% by mass
Polyvinyl butyral resin 1.0% by mass

Examples 2-19
As shown in the table, ink was blended in the same procedure as in Example 1 except that each component was changed to obtain an oil-based ink composition for writing tools of Examples 2 to 19. The evaluation results are shown in the table.

Comparative Examples 1-2
As shown in the table, oil-based ink compositions for writing tools of Comparative Examples 1 and 2 were obtained in the same procedure as in Example 1 except that each component was changed. The evaluation results are shown in the table.

Tests and Evaluations The oil-based ink composition for writing tools prepared in Examples 1 to 19 and Comparative Examples 1 and 2 was placed on the tip of an ink container (made of polypropylene) with a ball (φ0.7 mm, arithmetic average roughness of the ball surface) ( A ballpoint pen tip that rotatably holds Ra): 7 nm)) is mounted, and the oil-based ballpoint pen ink (0.2 g) of Example 1 is directly stored in the ink storage cylinder to hold the ballpoint pen refill. ) An oil-based ballpoint pen manufactured by Pilot Corporation (trade name: Super Grip (registered trademark)) was placed to prepare an oil-based ballpoint pen, and the following tests and evaluations were performed using the writing paper JIS P3201 as the writing test paper.

Abrasion resistance test (wear test of ball seat): Wear of the ball seat after the writing test was measured with a running tester having a load of 400 gf and a writing angle of 70 ° and 4 m / min.
Ball seat wear less than 5 μm ・ ・ ・ ◎
Ball seat wear of 5 μm or more and less than 10 μm ・ ・ ・ ○
The wear of the ball seat is 10 μm or more and less than 20 μm, but it is writable ... △
The ball seat wears so badly that it causes poor writing ... ×

Writing taste: A handwritten sensory test was conducted and evaluated.
Very smooth ... ◎
Smooth ... ○
Smoothness at a level that does not cause any problems in practical use ・ ・ ・ △
Heavy things ... ×

Writing performance test: After writing by hand, leave the tip of the tip in an environment of 20 ° C and 65% RH for 24 hours, then write in the running test under the following writing conditions, and the length of the handwriting blur in writing. Was measured.
<Writing conditions> Under the conditions of a writing load of 200 gf, a writing angle of 70 °, and a writing speed of 4 m / min, straight-line writing was performed with a running tester and evaluated.
Handwriting cassoulet length is less than 5 mm ... ◎
The length of the handwriting blur is 5 mm or more and less than 10 mm ... ○
The length of the handwriting blur is 10 mm or more and less than 20 mm ... △
Handwriting cassoulet length of 20 mm or more ... ×

Ink aging test: The ink in the chip body was observed under a microscope one month later in an environment of 50 ° C.
Good with no deposits ... ◎
A small amount of precipitates ... ○
Precipitates were generated, but there is no problem in practical use ... △
Precipitates that cause blurring and poor writing ... ×

Ink follow-up performance test: In an environment of 50 ° C., one month later, continuous quick writing was performed by hand for 10 seconds.
Handwriting cassoulet, no line skipping ... ◎
There were some handwriting cassoulet and line skipping, but it was at a level where there was no problem in practical use ... ○
Handwriting cassoulet, line skipping ... △
Handwriting cassoulet, terrible line skipping ... ×

In Examples 1 to 19, good performance was obtained in all of the wear resistance test (ball seat wear test), writing quality, writing performance test, ink aging test, and ink follow-up performance test.
In Examples 1 to 17 and 19, a pigment was used as the colorant, but the pigment dispersibility was good and stable.

Further, in Comparative Examples 1 and 2, since the polyoxyalkylene glyceryl ether was not used, the wear resistance test (wear test of the ball seat) was poor, and further, the writing taste, the writing performance test, the ink aging test, and the ink followability test were also performed. It was inferior.

In addition, when using a haunting type oil-based writing instrument (ballpoint pen, marking pen) such as a knock-type oil-based writing instrument (ballpoint pen, marking pen) or a rotary feeding type oil-based writing instrument (ballpoint pen, marking pen), writing performance is one of the important performances. Therefore, it is effective to use an ink composition as in the present invention.

Further, in the present embodiment, an oil-based ballpoint pen in which a ballpoint pen refill containing an oil-based ink composition for a writing tool is arranged in a shaft cylinder is illustrated, but the writing tool of the present invention holds the shaft cylinder itself in ink. It may be a direct-packed ballpoint pen that is a cylinder and the oil-based ink composition for writing tools is directly stored in the shaft cylinder, an oil-based ballpoint pen that is a marking pen, or an oil-based marking pen. A structure may be used in which the composition (refill) is used as it is as a ballpoint pen or a marking pen.

The present invention can be used as an oil-based ink composition for writing instruments, and more specifically, it can be widely used as a cap-type, knock-type or the like oil-based ballpoint pen or oil-based marking pen filled with the oil-based writing instrument ink composition.

Claims (6)

An oil-based ink composition for writing utensils, which comprises a colorant, an organic solvent, and a polyglycerin condensed fatty acid ester. The oil-based ink composition for writing tools according to claim 1, wherein the content of the polyglycerin condensed fatty acid ester is 0.1 to 10% by mass with respect to the total amount of the ink composition. The oil-based ink composition for stationery according to claim 1 or 2, wherein the organic solvent is an aromatic alcohol. The oil-based ink composition for writing tools according to any one of claims 1 to 3, wherein the ink viscosity at 20 ° C. and a shear rate of 5 sec ^{-1 is 30,000 mPa · s or less.} A writing tool comprising the oil-based ink composition for writing tools according to any one of claims 1 to 4. A ballpoint pen tip that rotatably holds a ball is provided at the tip of the ink storage cylinder, and the oil-based ink composition for writing instruments according to any one of claims 1 to 4 is stored in the ink storage cylinder. An oil-based ballpoint pen that is characterized by being made of ink.