JP2019116578A - Aqueous ink composition for writing instrument, and writing instrument using the same - Google Patents

Abstract

To provide an aqueous ink composition for writing instrument which is excellent in dispersion stability and can obtain good handwriting, and writing instrument using the same.SOLUTION: An aqueous ink composition for writing instrument contains styrene-acrylonitrile resin particles, a coloring agent, polyglyceryl fatty acid ester and water. A combination of the styrene-acrylonitrile resin particles and the coloring agent can be styrene-acrylonitrile resin particles colored with the coloring agent. The ink composition can be used in writing instrument.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous ink composition for writing instruments, and a writing instrument using the same.

  In recent years, high water resistance and light resistance are desired for water-based ink compositions for writing instruments, and ink compositions using pigments have been proposed to improve their properties.

  However, since the pigment is insoluble in water, which is the main solvent of the ink composition, aggregation and sedimentation are likely to occur, and the color development of the ink composition may be reduced unless the pigment is uniformly dispersed and stabilized. The ink discharge amount from the pen tip may be reduced to cause streaks or streaks, or writing may become impossible, which may make it impossible to obtain sufficient performance as an aqueous ink composition for a writing tool.

  Then, in order to improve the dispersibility of a pigment, many ink compositions in which various dispersants are added to the ink composition have been proposed.

  For example, in Patent Document 1, an ink composition comprising a polymer compound obtained by copolymerizing N-vinyl pyrrolidone or a derivative thereof with an alkene compound as a dispersant is disclosed in Patent Document 2 as a carboxyl group-containing compound. An ink composition comprising an alkali salt of the following as a dispersant has been proposed.

  However, although these dispersants exert the effect of improving the dispersibility, they may not be sufficient. As a result, when the addition amount of the dispersant is small, the streaks may not be sufficiently resolved, and when a large amount of the dispersant is added for the purpose of obtaining a good dispersion effect, the viscosity of the ink composition is excessive. In some cases, the components of the ink composition may coagulate and separate after storage with time. Therefore, there is room for further improvement when using these dispersants.

  Further, in recent years, color variations are desired for the ink composition so as to express various colors. In order to meet such needs, different types of pigments need to be prepared, and each pigment requires a great deal of effort to adjust its dispersion stability. Then, in order to reduce such a load, the ink composition using the colored resin particle which colored resin particles with a pigment or dye is proposed. Such an ink composition uses a colored resin material in place of the pigment. Since the colored resin particles are colored with the coloring agent to the resin particles, the specific gravity is smaller compared to the conventionally used pigment, and the type of the resin particles is the same in selecting the dispersant. There is an advantage that selection of the dispersant can be reduced since the same dispersant can be used if it is. However, according to the study of the present inventors, it is difficult for such colored resin particles to be uniformly colored in a desired color, in which the resin particles aggregate at the time of coloring, and the ink composition When used in ink, although it shows good dispersion stability at the time of preparation of the ink composition, problems such as aggregation and sedimentation may occur after the passage of time, and there is room for improvement.

  In addition, the ink composition using the colored resin particles as a coloring agent generally has a high solid content. As a result, the ink flowability is lowered, and handwriting may be blurred. Therefore, it has been desired to improve the ink flowability as well as the dispersibility.

JP-A-8-176488 JP, 2004-018675, A

  The present invention provides an aqueous ink composition for a writing instrument which is excellent in ink fluidity and dispersion stability and can give a good handwriting, and further provides a writing instrument using the same.

  The aqueous ink composition for a writing instrument according to the first aspect of the present invention is characterized by comprising styrene-acrylonitrile resin particles, a colorant, a polyglycerin fatty acid ester, and water.

  An aqueous ink composition for a writing instrument according to a second aspect of the present invention is characterized by comprising styrene-acrylonitrile resin particles colored by a colorant, a polyglycerin fatty acid ester, and water. .

  A writing instrument according to the present invention is characterized in that it contains any one of the above ink compositions.

  According to the present invention, a water-based ink composition for a writing instrument excellent in writing performance, such as good ink flowability and coloring properties and good handwriting with improved line jumps and brush marks, and a writing instrument using the same Can be provided. Furthermore, the ink composition according to the present invention is excellent not only in the dispersion stability immediately after preparation but also in the dispersion stability after aging, and is less susceptible to fading after being stored for a long time. And when such an ink composition is accommodated in a transparent ink container, since the color of an ink composition is visually recognized uniformly from an ink container, it is excellent in quality. In addition, it is possible to realize a writing instrument group having various color variations by using colored resin particles which are colored in various colors.

  Hereinafter, embodiments of the present invention will be described in detail. In the present specification, “parts”, “%”, “ratios” and the like indicating the composition are on a mass basis unless otherwise specified, and the content is a component based on the mass of the ink composition. % By mass of

<Water-based ink composition for writing instrument>
An aqueous ink composition for a writing instrument according to a first aspect of the present invention (hereinafter sometimes referred to as an ink composition) contains styrene-acrylonitrile resin particles, a colorant, a polyglycerin fatty acid ester, and water. It is a thing.

  The aqueous ink composition for a writing instrument according to the second aspect of the present invention comprises styrene-acrylonitrile resin particles colored with a colorant, polyglycerin fatty acid ester, and water.

The first ink composition differs in that it uses a combination of styrene-acrylonitrile resin particles and a colorant, and the second ink composition uses styrene-acrylonitrile resin particles colored with a colorant, Is basically the same.
Hereinafter, these ink compositions will be described in detail.

<Styrene-Acrylonitrile Resin Particles>
The first ink composition according to the present invention comprises styrene-acrylonitrile resin particles. The resin particles are colorless before coloring, but when incorporated into the ink composition as they are, there is a coloring effect that brings whiteness to the ink composition. Also, according to the study of the present inventors, it was found that when used in combination with a colorant, it has a function as a coloring aid, adjusting the color of the ink composition together with the colorant. . As a result, styrene-acrylonitrile resin particles provide excellent color development to the ink composition.

  Styrene-acrylonitrile resin particles are resin particles obtained by copolymerizing styrene and acrylonitrile as a monomer. Although the compounding ratio of styrene and acrylonitrile is not particularly limited, in general, 10 to 90 mol% of styrene and 90 to 10 mol% of acrylonitrile are compounded. In addition, monomers other than styrene and acrylonitrile can be combined in the range which does not impair the effect of this invention.

  The styrene-acrylonitrile resin particles in the present invention can be obtained by any conventionally known method, but in consideration of the color developability of the ink composition, the dispersion stability, and the ink dischargeability from the pen point, uniform particles can be obtained. Are preferably resin particles obtained by emulsion polymerization of styrene and acrylonitrile, and further preferably used as a styrene-acrylonitrile resin particle dispersion in a state of being dispersed in a dispersion medium such as water in advance. . It is also possible to use a commercial item as the styrene-acrylonitrile resin particle dispersion.

  Further, the size of the styrene-acrylonitrile resin particles is not particularly limited, but in order to maintain dispersibility and to prevent line jumps and blurs when used in a writing instrument, it is preferable that the particle diameter is small, and high color development In order to obtain, it is preferable that the average particle size is large. From such a viewpoint, the volume-based average particle diameter is preferably 0.05 to 10 μm.

  The content of the styrene-acrylonitrile resin particles in the ink composition of the present invention is preferably 0.1 to 50% by mass, and preferably 1 to 30% by mass, based on the total mass of the ink composition. Is more preferred. If the content of the styrene-acrylonitrile resin particles is within the above-mentioned numerical range, it is possible to provide the ink composition with a good color forming property and at the same time provide a good temporal stability.

  In order to achieve color development equivalent to the case of using an inorganic pigment such as ultramarine blue or iron oxide, or an organic pigment such as phthalocyanine blue or quinacridone red when using a coloring agent containing styrene-acrylonitrile resin particles as a main component, Generally, a larger amount of colorant is required. Therefore, in the ink composition according to the present invention, the content of the styrene-acrylonitrile resin particles is 12 to 35% by mass based on the total mass of the ink composition in order to achieve excellent color development. Is more preferable, and 15 to 25% by mass is particularly preferable.

<Colorant>
The colorant in the first ink composition of the present invention is to adjust the color of the ink composition together with the styrene-acrylonitrile resin particles. The coloring agent contributes to color independently in the ink composition, and also develops color adjusted by the combination with the styrene-acrylonitrile resin particles, or adsorbs or penetrates into the styrene-acrylonitrile resin particles in the ink composition. May form colored particles.

  As such a coloring agent, any dye or pigment is used, and it is not particularly limited.

  The dye is not particularly limited, and, for example, acid dyes, basic dyes, direct dyes, disperse dyes, oil-soluble dyes, reactive dyes, metal-containing dyes, food dyes, various salt types dyes, etc. Can be mentioned.

  The pigment is not particularly limited, and examples thereof include inorganic, organic and processed pigments. Specifically, carbon black, aniline black, ultramarine blue, yellow lead, titanium oxide, iron oxide, phthalocyanine type Pigments, azo pigments, quinacridone pigments, quinophthalone pigments, Sureren pigments, triphenylmethane pigments, perinone pigments, perylene pigments, dioxazine pigments, aluminum pigments, pearl pigments, microcapsule pigments, etc. It can be mentioned. The pigment may be a water-dispersed pigment product or the like dispersed in a medium in advance using a pigment dispersant.

  Specifically, C.I. I. Acid Red 18, C.I. I. Acid Red 51, C.I. I. Acid Red 52, C.I. I. Acid Red 87, C.I. I. Acid Red 92, C.I. I. Acid Red 289, C.I. I. Acid Orange 10, C.I. I. Acid Yellow 3, C.I. I. Acid Yellow 7, C.I. I. Acid Yellow 23, C.I. I. Acid Yellow 42, C.I. I. Acid green 3, C.I. I. Acid Green 16, C.I. I. Acid Blue 1, C.I. I. Acid Blue 9, C.I. I. Acid Blue 22, C.I. I. Acid Blue 90, C.I. I. Acid Blue 239, C.I. I. Acid Blue 248, C.I. I. Acid Baolet 15, C.I. I. Acid Violet 49, C.I. I. Acid Black 1, C.I. I. Acid dyes such as acid black 2, C.I. I. Basic red 1: 1, C.I. I. Basic Yellow 28, C.I. I. Beyello 40, C.I. I. Basic Orange 2, C.I. I. Basic orange 14, C.I. I. Basic Green 4, C.I. I. Basic Blue 7, C.I. I. Basic Blue 9, C.I. I. Basic Blue 26, C.I. I. Basic Violet 15, C.I. I. Basic Violet 11: 1, C.I. I. Basic Violet 1, C.I. I. Basic Violet 3, C.I. I. Basic dyes such as Basic Violet 10, C.I. I. Direct red 28, C.I. I. Direct Yellow 44, C.I. I. Direct blue 86, C.I. I. Direct Blue 87, C.I. I. Direct violet 51, C.I. I. Direct dyes such as direct black 19, C.I. I. Disperse Yellow 82, C.I. I. Disperse Yellow 3, C.I. I. Disperse Yellow 54, C.I. I. Disperse thread 191, C. I. Disperse thread 60, C.I. I. Disperse dyes such as disperse violet 57, C.I. I. Food Yellow 3, C.I. I. Food pigments such as Food Black 2 can be mentioned.

  Furthermore, as described later, the polyglycerin fatty acid ester works effectively even when the styrene-acrylonitrile resin particles are colored with a coloring agent, suppresses the aggregation of the styrene-acrylonitrile resin particles, and uniformly and uniformly colored, Although it has the effect of further improving the dispersion stability and color development of the ink composition, it is preferable to use a basic dye as the dye for coloring the styrene-acrylonitrile resin particles, considering the effect of the polyglycerin fatty acid ester .

  Furthermore, among the basic dyes, xanthene-based and triaryl-based basic dyes and azo-based basic dyes are preferable.

  The content of the colorant in the ink composition of the present invention is preferably 0.1 to 30% by mass, and more preferably 0.1 to 10% by mass, based on the total mass of the ink composition. In particular, in the present invention, as described above, the colorant is preferably used for coloring styrene-acrylonitrile resin particles, and in this case, the content of the coloring agent is the coloring property to the styrene-acrylonitrile resin particles. When it considers, it is preferable that it is 0.1-2 mass% on the basis of the total mass of an ink composition, and it is more preferable that it is 0.3-1 mass%.

<Styrene-Acrylonitrile Resin Particles Colored by Colorant>
The second ink composition according to the present invention comprises styrene-acrylonitrile resin particles (hereinafter sometimes referred to simply as colored resin particles) colored by a colorant. The colored resin particles are preferably those obtained by coloring the above-mentioned styrene-acrylonitrile resin particles by the above-mentioned coloring agent. By using such colored resin particles, the color developability of the ink composition can be further improved. This is because the styrene-acrylonitrile resin particles have high transparency, so they can be colored to a desired color by a coloring agent, and can be colored resin particles excellent in coloring ability that can express various colors. It is. In addition, when colored resin particles are used, the dispersion effect of the polyglycerin fatty acid ester is efficiently obtained as compared with the case where the coloring agent and the styrene-acrylonitrile resin particles are individually used, and the ink composition having excellent dispersion stability. You can get things. Therefore, it is preferable to use colored resin particles instead of the combination of the styrene-acrylonitrile resin particles and the colorant in the first ink composition.

  In addition, styrene-acrylonitrile resin particles are excellent in alkali resistance, acid resistance and heat resistance, and colored resin particles obtained using them as a raw material are stably present even in an ink composition containing various components such as additives. It is easy to do and is not easily affected by the thermal environment. Therefore, by using the colored resin particles, it is possible to obtain an ink composition which is also excellent in color developability and temporal stability.

  In addition, a coloring agent can also be combined with colored resin particles. That is, in order to further strengthen the color of the colored resin particles, the coloring agent used for preparation of the colored resin particles can be further added to the ink composition. In addition, colorants having different colors can be combined for the purpose of color adjustment and the like. In addition, uncolored styrene-acrylonitrile resin particles can be combined with the colored resin particles.

  The content of the colored resin particles is based on the total of the styrene-acrylonitrile resin particles and the colorant in the first ink composition. If the colored resin particles are combined with a coloring agent or styrene-acrylonitrile resin particles, the total amount taken into consideration also corresponds to the total amount of the styrene-acrylonitrile resin particles and the coloring agent in the first ink composition.

<Polyglycerin fatty acid ester>
The polyglycerin fatty acid ester used in the ink composition according to the present invention is represented by the following general formula.
RO- (CH ₂ -CH (OR) -CH ₂ -O-) _n R
During the ceremony
R is hydrogen or a fatty acid residue, and n is a number representing the degree of polymerization.
Here, R is preferably a fatty acid residue having 10 to 20 carbon atoms. More specifically, residues derived from stearic acid, oleic acid, lauric acid, myristic acid, caprylic acid, behenic acid, erucic acid, linoleic acid, condensed linoleic acid and the like can be mentioned, and these fatty acids are used depending on the purpose. You may use in combination of 2 or more types. Among them, residues derived from lauric acid, stearic acid or oleic acid are preferred. This is because ink flowability and dispersion stability are excellent, and an effect of obtaining good handwriting can be easily obtained. Furthermore, it is preferable that it is a residue derived from lauric acid in consideration of ink temporal stability.
Moreover, 5-20 are preferable, 6-14 are more preferable, and 8-12 are especially preferable. This is because when the polymerization degree is in the above range, the ink flowability and the dispersion stability are excellent, and a good handwriting tends to be obtained.
Further, the molecular weight of the polyglycerin fatty acid ester is not particularly limited, but it is preferable that the mass average molecular weight is 300 to 5,000. In the present invention, the mass average molecular weight is measured by gel permeation chromatography based on polystyrene.
In the ink composition according to the present invention, the polyglycerin fatty acid ester acts as a dispersant, and can uniformly disperse components which may be present in a water-insoluble state as a main solvent. The polyglycerin fatty acid ester exerts an excellent dispersing effect, in particular, on styrene-acrylonitrile resin particles.

  The HLB value of the polyglycerin fatty acid ester is preferably 4 to 18. This is because ink flowability and dispersion stability tend to be improved when the HLB value is in the above range. Furthermore, by stabilizing the dissolution stability of the polyglycerin fatty acid ester in water or the water-soluble organic solvent, the effect of the present invention can be stably exhibited over a long period of time, so that the HLB value is 10 to 18 Preferably, 11 to 17 is particularly preferable.

Here, the HLB value is calculated by the following equation according to the Atlas method.
HLB = 20 × (saponification value of 1-ester / acid value of fatty acid)
Atlas method: A saponification value is S, an acid value of a fatty acid is A, and an HLB value is defined as 20 × (1−S / A). The acid value is "the number of mg of potassium hydroxide necessary to neutralize the free fatty acid present in 1 g of the ester".

  Furthermore, as a result of intensive investigations by the present inventors, the dispersion effect of the polyglycerin fatty acid ester is not only styrene-acrylonitrile resin particles before coloring but also a series of styrene-acrylonitrile to colored styrene-acrylonitrile resin particles at coloring. By exerting an effect on resin particles and obtaining excellent styrene-acrylonitrile colored resin particles, and by using the obtained colored resin particles for an ink composition, the dispersion stability, the color forming property, and the like can be further enhanced. Moreover, it turned out that it can be set as the ink composition excellent in writing performance.

  According to the study of the present inventors, polyglycerin fatty acid ester works effectively when styrene-acrylonitrile resin particles are colored with a colorant. In particular, the aggregation of the styrene-acrylonitrile resin particles before coloring is suppressed, and further, the aggregation of the colored resin particles obtained is suppressed, and the ink composition can be provided with excellent dispersion stability. I understand. Furthermore, since the polyglycerin fatty acid ester also has the effect of uniformly coloring the styrene-acrylonitrile resin particles uniformly with the coloring agent, the ink composition using the obtained colored resin particles is excellent in color development. It also turned out to be a thing. Therefore, in the present invention, it is extremely effective to use polyglycerin fatty acid ester for coloring and dispersing styrene-acrylonitrile resin particles, and it is possible to provide the ink composition with good color forming property and dispersion stability. .

  Further, according to the study of the present inventors, it was also found that the use of the polyglycerin fatty acid ester improves the ink flowability and improves the blurring at the time of writing. Ink compositions that do not contain polyglycerin fatty acid esters may cause blur when used for writing over time, but such ink films containing polyglycerin fatty acid esters improve such blur. This is because polyglycerin fatty acid ester acts on the surface of styrene-acrylonitrile resin particles to reduce the contact resistance between the particles, thereby improving the flowability (ink flowability) of the ink composition and reducing the fogging. it is conceivable that. Such effects can be obtained by using styrene-acrylonitrile resin particles and polyglycerin fatty acid ester, as compared to the case where a polyglycerin fatty acid ester is used in combination with an inorganic pigment generally used or an organic pigment such as phthalocyanine blue or quinacridone red. It is remarkable when used together. This is considered to be due to the difference in the surface properties of the particles and the difference in the content of styrene-acrylonitrile resin particles used in the ink composition. In particular, the content of styrene-acrylonitrile resin particles is relatively higher than that of a general ink composition, in particular, based on the total mass of the ink composition, in order to easily obtain better color development. , 12 to 35% by mass. In such a case, the contact resistance between particles tends to be influenced, but in the present invention, the effect of the polyglycerin fatty acid ester is more effective because the ink flowability is improved.

  Further, in the present invention, by combining castor oil and a polyglycerin fatty acid ester, the ink fluidity tends to further improve, and the writing taste also tends to improve, which is effective.

  In the present invention, the polyglycerin fatty acid ester as described above may be used as one or a mixture of two or more.

  The content of the polyglycerin fatty acid ester in the ink composition of the present invention is preferably 0.01 to 10% by mass, and 0.05 to 5% by mass, based on the total mass of the ink composition. Is more preferred. If the content of the polyglycerin fatty acid ester is 0.01% by mass or more, the effect of the polyglycerin fatty acid ester as a dispersant can be obtained, and the excellent dispersion stability of the ink composition can be obtained. If the content is 10% by mass or less, it is possible to prevent residual air bubbles in the ink composition caused by the foamability characteristic of the polyglycerin fatty acid ester, and to suppress the generation of precipitates derived from the polyglycerin fatty acid ester. Furthermore, when coloring the styrene-acrylonitrile resin particles, in view of suppressing aggregation with the styrene-acrylonitrile resin particles and uniformly coloring, it is preferably 0.1 to 5% by mass, and 0.3 to 5% by mass. Particularly preferred is 3% by mass.

  The ink composition according to the present invention may contain a dispersant other than polyglycerin fatty acid ester. Such dispersants can be selected arbitrarily. However, in the present invention, since the characteristics superior to conventional dispersants are achieved by using polyglycerin fatty acid ester, the content is preferably low. For example, polyoxyalkylene aryl ethers such as polyoxyethylene nonylphenyl ether have been used as dispersants to be incorporated into conventional ink compositions, but the content of such conventional dispersants is the total of the ink composition. The content is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, particularly preferably 0.01% by mass or less, and the content is zero. Is most preferred. In recent years, it has been found that the safety of the polyoxyalkylene aryl ether tends to be higher as the addition amount is smaller, so that the ink composition according to the present invention also realizes higher safety. In the present invention, the content rate being zero means that the content can not be detected by various measuring devices and is below the detection limit.

<Phosphate ester surfactant>
Moreover, it is preferable that the ink composition of this invention comprises phosphate ester type surfactant. In addition to the effect of improving the dispersibility of the ink composition, the surfactant also acts as a lubricant when the ink composition is used for a ballpoint pen. The lubricant improves the lubricity between the ball and the ballpoint pen tip possessed by the ballpoint pen and smoothens the rotation of the ball, thereby suppressing the wear of the ball seat and improving the writing taste. The phosphate ester surfactant having a phosphoric acid group used in the present invention has a property that the phosphoric acid group is easily adsorbed to a metal, thereby improving the lubricity and suppressing the wear of the ball seat and the writing taste. Easy to improve. Therefore, when the ink composition of the present invention is applied to a ballpoint pen, particularly excellent writing taste can be realized. However, since this surfactant contributes not only to the lubricity but also to the improvement of the dispersibility, it works effectively also when the ink composition is used for writing instruments other than ballpoint pens.

  Furthermore, phosphate ester surfactants also have the effect of adjusting the surface tension. For this reason, a writing instrument particularly provided with a comb groove-like ink flow rate adjustment member described later and having a supply mechanism for supplying the ink composition to the pen tip with the intervening ink groove being superior to the ink flow rate adjustment member It is preferable because it exhibits wettability. Therefore, the ink composition according to the present invention is also preferable to a fountain pen and marker having an ink flow rate adjusting member in the form of comb grooves, a marker pen, a ballpoint pen and the like.

  Examples of the phosphate ester surfactant include linear alcohol based, styrenated phenol based, nonylphenol based, octylphenol based phosphoric acid based surfactants, among which linear alcohol based, styrenated phenol It is preferable to use a phosphate ester surfactant of a system.

  In the present invention, the phosphate ester surfactant preferably has an HLB value of 5 to 15, and preferably 6 to 13. Further, in the present invention, the carbon number of the alkyl group or the alkyl allyl group which the phosphate ester surfactant has is preferably 6 to 30, more preferably 8 to 18, and more preferably 10 to 14. Particularly preferred. This is because a linear phosphate ester surfactant having a specific HLB value and carbon number can synergistically improve the dispersing effect together with the polyglycerin fatty acid ester and at the same time provide a lubricating effect. .

  In the present invention, the HLB value of the phosphate ester surfactant means the HLB value of the raw material non-ionic surfactant of the phosphate ester surfactant, and HLB = 7 + 11. as a general formula. 7 log (Mw / Mo), (Mw; molecular weight of hydrophilic group, Mo; molecular weight of lipophilic group).

  In addition, as a specific example of phosphoric acid ester type surfactant, Plysurf series (Daiichi Kogyo Seiyaku Co., Ltd.) etc. are mentioned, and as linear alcohol type phosphoric acid ester type surfactant, Plysurf A 212 C, A208B, A213B, A208F, A215C, A219B, A208N can be mentioned, and as a styrenated phenolic phosphate ester surfactant, Plysurf AL can be mentioned, and as a nonylphenol type, plysurf can be mentioned. Examples thereof include 207H, A212E, and A217E. Examples of octylphenols include Plysurf A210G.

  The content of the phosphate ester surfactant, when added, is preferably 0.1 to 2.0% by mass, and 0.5 to 1.5% by mass, based on the total mass of the ink composition. It is more preferable that In the ink composition according to the present invention, materials other than phosphate ester surfactants can also be used as surfactants or lubricants. As such materials, surfactants and fatty acids other than phosphate ester surfactants can be mentioned.

  Specific examples of the fatty acid include linoleic acid and oleic acid, and specific examples include OS soap, NS soap, FR-14, FR-25 (Kao Corporation) and the like.

<Water>
The water is not particularly limited, and for example, conventional water such as ion exchanged water, distilled water, and tap water can be used.

<Other additives>
The ink composition according to the present invention may optionally contain any additive. The additives which can be used will be described as follows.

It is preferable to further use a water-soluble organic solvent in the ink composition of the present invention.
When the ink contains a component that can be present in water-insoluble state, which is a main solvent such as resin particles and pigments, the water is evaporated by the pen tip of the writing instrument containing the ink, and the ink is dried and solidified. The ink flow path may be clogged. When such a phenomenon occurs, it is difficult to eliminate the clogging by the ink to be followed later, and the writing instrument may not be able to write again although there is a remaining amount of ink. For this reason, it is preferable to improve the dry-up performance. In the present invention, by adding a water-soluble organic solvent to the ink composition, the dry-up resistance can be improved, and therefore, the use of a water-soluble organic solvent is preferable. Examples of water-soluble organic solvents that can be used include polyhydric alcohols and glycol ethers. Among them, polyhydric alcohols such as ethylene glycol, diethylene glycol and glycerin are preferably selected and used. These solvents can impart the hygroscopic effect of polyhydric alcohols to the ink composition without significantly affecting the dispersion stability of the ink composition, and can improve the dry-up performance.

  In addition, as described above, in the present invention, it is preferable to prepare in advance a colored resin particle dispersion for a writing instrument comprising a colorant, a styrene-acrylonitrile resin particle, a polyglycerin fatty acid ester, and water. However, when preparing the colored resin particle dispersion for writing instruments, including the water-soluble organic solvent in advance prevents sedimentation by adjusting the specific gravity of the dispersion medium with the water-soluble organic solvent and improving the wettability of the colored resin particle surface It is effective because improvement of dispersion stability can be expected.

The ink composition of the present invention preferably comprises dextrin.
As mentioned above, when it contains components which can be present in water-insoluble state, which is the main solvent such as styrene-acrylonitrile resin particles and pigments, it is necessary to consider, for example, improvement of the dry-up performance at the tip of the tip of a ballpoint pen is there. The dextrin has the effect of forming a film on the pen point and preventing the evaporation of the solvent in the ink by the film. Therefore, using dextrin is effective because an ink composition having excellent dry-up performance can be obtained. In particular, when the content of styrene-acrylonitrile resin particles is high in order to easily obtain good color development, the total solid content in the ink tends to be high, and the dry-up performance at the tip of the tip tends to decrease. Preferably, dextrin is used. And, since dextrin has an appropriate wetting effect, it works as a dispersion aid, and it has the effect of facilitating the improvement of dispersibility by combination with polyglycerin fatty acid ester, so combining alkyl sulfate and dextrin Is effective. In addition, dextrin is a generic term of a substance in which several α-glucoses are polymerized by glycosidic bond, and is a kind of dietary fiber, and is obtained by hydrolysis of starch and the like.

  The mass average molecular weight of the dextrin is preferably 5,000 to 120,000. If it is 120000 or more, the film formed on the pen tip is hard, and there is a tendency for the handwriting to be easily blurred in the writing at the time of dry-up. On the other hand, if it is less than 5000, it is difficult to impart viscosity change to improve the dispersion stability with time, and the hygroscopicity of dextrin tends to be high, and the coating formed on the pen tip is soft and stably maintained by the pen tip It is difficult to suppress the evaporation of the solvent in the ink. In consideration of the improvement of the above effect, it is preferable to use a dextrin having a mass average molecular weight of 20,000 to 100,000.

  The content of the dextrin is preferably 0.1 to 5% by mass based on the total mass of the ink composition. This is because if it is less than 0.1% by mass, the effect of improving the dry-up performance tends not to be sufficiently obtained, and if it exceeds 5% by mass, it tends to be difficult to dissolve in the ink. In consideration of the dissolution stability in the ink, 0.1 to 3% by mass is preferable, and 1 to 3% by mass is most preferable in consideration of the improvement of the dry-up performance.

  Moreover, in the present invention, it is preferable to contain resin particles (except for styrene-acrylonitrile resin particles).

  The polyglycerin fatty acid ester used in the present invention is also excellent in the dispersion stability of resin particles other than styrene-acrylonitrile resin particles. Therefore, even when resin particles are added for various purposes such as ink leakage suppression and writing taste improvement, the ink composition of the present invention can maintain excellent dispersion stability. For this reason, in the present invention, further including resin particles (excluding styrene-acrylonitrile resin particles) further obtains desired performance obtained by various resin particles without impairing the dispersion stability of the ink composition. Because it can be effective.

Examples of the resin particles include olefin resin particles, acrylic resin particles, urethane resin particles, styrene-butadiene resin particles, polyester resin particles, vinyl acetate resin particles, benzoguanamine / formaldehyde resin particles, and the like.
The ink composition of the present invention comprising the polyglycerin fatty acid ester, the styrene-acrylonitrile resin particles, and the coloring agent is particularly excellent in dispersion stability, so that the ink fluidity is high, and the ink leaks from the pen point. Is likely to occur. For this reason, in the present invention, it is preferable to use resin particles of an olefin-based resin particle and benzoguanamine-formaldehyde resin particle, which have a high effect of suppressing ink leak in a pen tip.

The ink composition of the present invention may also include pH adjustment.
Examples of pH adjusters include basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate and sodium hydroxide, basic organic compounds such as sodium acetate, triethanolamine and diethanolamine, lactic acid and citric acid, etc. In the present invention, in consideration of compatibility with polyglycerin fatty acid ester and the temporal stability of the ink composition, it is preferable to use a basic organic compound, and more preferably, triethanolamine which is weakly basic. Is preferred. These pH adjusters may be used alone or in combination of two or more.

  The ink composition of the present invention preferably further comprises an ink viscosity modifier. When the ink composition of the present invention is used in a writing instrument, it is preferable to use a shear thinning agent as the ink viscosity modifier. This is because the ink composition can easily maintain the uniform and good dispersion obtained by the polyglycerin fatty acid ester by using a shear reducing viscosity imparting agent, and prevents the sedimentation of styrene-acrylonitrile resin particles, pigments and the like. As a result, good ink dischargeability can be obtained, and bleeding and the like can be obtained, and a good coloring can be obtained.

Examples of the shear thinning agent include cross-linked acrylic acid polymers, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, polysaccharides such as cellulose and diutatan gum, and association-type increase. There may be mentioned tackifiers. Among these, it is preferable to use the polysaccharide, and it is more preferable to use succinoglycan.
These shear thinning agents may be used alone or in combination of two or more.

In the present invention, when the ink composition further comprises an ink viscosity modifier, the ink viscosity of the ink composition of the present invention is 500 to 5000 mPa · s at a shear rate of 1.92 sec- ¹ under an environment of 20 ° C. If the ink viscosity is within the above-mentioned numerical range, it is possible to obtain excellent ink fluidity and dispersion stability, good ink dischargeability, and good handwriting free of blurring and bleeding of the handwriting. In particular, the ink viscosity is more preferably 1000 to 3000 mPa · s, considering the dispersibility of styrene-acrylonitrile colored resin particles colored with a colorant and good ink dischargeability from the pen tip of the ink composition. .

  The ink composition of the present invention may further contain additives such as a rust inhibitor, preservative, chelating agent, moisturizer, penetrant, lubricant and the like for the purpose of further improving the ink physical properties and functions.

  The rust inhibitor includes benzotriazole and derivatives thereof, tolyltriazole, dicyclohexyl ammonium nitrite, diisopropyl ammonium nitrite, sodium thiosulfate, saponin, dialkyl thiourea and the like.

  As preservatives, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl p-hydroxybenzoate, 2,3,5,6-tetrachloro-4- (methylsulfonyl) pyridine, 2-pyridinethiol-1- Sodium oxide, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one and the like can be mentioned.

  As the humectant, in addition to the polyhydric alcohol solvent, urea, or sorbite, N, N, N-trialkyl amino acids such as trimethylglycine, triethylglycine, tripropylglycine and the like can be mentioned.

  Furthermore, various surfactants may be included as a penetrant and a surface tension regulator, and examples thereof include nonionic, anionic and cationic surfactants. In addition, surfactants having an acetylene bond in the structure, silicone surfactants, fluoro surfactants and the like can also be mentioned.

  The ink composition according to the present invention can also contain a chelating agent for sequestering metals present in the ink composition. As such a chelating agent, ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol ether diamine tetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyl iminodiacetic acid (HIDA), dihydroxyethyl Glycine (DHEG), diethylene triamine pentaacetic acid (DTPA), triethylene tetramine hexaacetic acid (TTHA) and their alkali metal salts, ammonium salts or amine salts, etc. may be mentioned. Here, for example, in a writing instrument such as a ballpoint pen or a fountain pen, the metal component may elute in the ink composition because the ink composition contacts metal. Such metal ions are believed to inhibit the stability of the ink composition, and conventional ink compositions generally contained a chelating agent. However, as a result of intensive studies by the present inventors, the ink composition according to the present invention containing a specific material is particularly excellent in the temporal stability of the ink composition by setting the addition amount of the chelating agent to a certain amount or less. Found out. Furthermore, when a specific phosphoric ester is used, the ink composition of the present invention is characterized in that no deterioration in stability due to metal ions is observed even if it does not contain a chelating agent. That is, the ink composition according to the present invention has high stability even when it is used for a ballpoint pen, a fountain pen, etc., in which the ink composition often contacts metal. Therefore, the content of the chelating agent in the ink composition according to the present invention is preferably 0.5% by mass or less based on the total mass of the ink composition, and more preferably 0.1% by mass or less The content is more preferably 0.05% by mass or less, more preferably 0.02% by mass or less, and most preferably zero.

  The ink composition according to the present invention contains an acidic group-containing substance such as polyglycerin fatty acid ester and phosphoric acid ester surfactant. Such acidic group-containing materials also include other chelating agents such as ethylenediaminetetraacetic acid. It is more preferable that the ink composition according to the present invention contain such an acidic group-containing substance within a specific range, since this has the effect of improving the ink temporal stability. Specifically, the total content of the polyglycerin fatty acid ester, the phosphate ester surfactant, and the chelating agent containing an acidic group is 0.1 to 10% by mass based on the total mass of the ink composition. Preferably, it is more preferably 0.1 to 3% by mass.

  Moreover, it is preferable that the compounding ratio of an acidic group containing chelating agent with respect to phosphoric acid ester type surfactant is 0 or more and less than 0.05 on a mass basis.

  In the present invention, the lower the ratio of the blending amount of the acid group-containing chelating agent to the total blending amount of the polyglycerin fatty acid ester and the phosphate ester surfactant, the line jumps when the ink composition is used for a writing instrument. It is preferable because it tends to reduce scraping. Specifically, it is preferable that (blended amount of acid group-containing chelating agent) / [(blended amount of polyglycerin fatty acid ester) + (blended amount of phosphate ester surfactant)] is 0.025 or less Is more preferably 0.005 or less, and most preferably zero.

  If the total content of the acidic group-containing substance and the compounding ratio of the acidic group-containing chelating agent to the phosphoric acid ester-based surfactant are within the above numerical range, the ink composition exhibits particularly good stability, and the ink Use of the composition is preferable because good handwriting can be obtained.

<PH value of ink composition>
The pH of the ink composition according to the present invention is preferably 6 to 10. This is because when the pH value approaches the acid side less than 6, the temporal stability of the ink composition may deteriorate, and when the ink composition of the present invention is used for a ballpoint pen, a fountain pen, etc., the ink composition Corrosion of the metal member with which the object comes in contact, and when the pH value exceeds 10 and approaches the strong alkali side, the ink composition tends to be discolored and discolored, and it is difficult to obtain good handwriting It is. In addition, when the styrene-acrylonitrile resin particles are colored with a coloring agent and used as a styrene-acrylonitrile colored resin particle, good stability of the ink composition with time, good color development, and good handwriting with improved streaking and the like. It is preferable that pH value is 7-9, when considering the improvement of writing nature, such as being obtained. In addition, in this invention, pH value shows the value measured at 20 degreeC using IM-40 S type pH meter.

<Method of Producing Ink Composition>
The preparation method of the first ink composition according to the present invention is not particularly limited, but the colorant, the styrene-acrylonitrile resin particles, the polyglycerin fatty acid ester, water, and others as needed. It is preferable to make the ink composition by adding the components of At this time, the mixing order is not particularly limited.

  The first ink composition according to the present invention can be produced by any method known in the art. Specifically, the respective components can be compounded in necessary amounts, and mixed by various stirring machines such as propeller stirring, homodisper or homomixer, various dispersing machines such as bead mill, or the like.

  Particularly, in the second ink composition, a colored resin particle dispersion is prepared in advance by blending and dispersing a colorant, styrene-acrylonitrile resin particles, polyglycerin fatty acid ester, and water, Furthermore, phosphate ester surfactants and other components can be mixed and produced as required. The ink composition can be obtained while maintaining the dispersion stability by sequentially adding other components to the styrene-acrylonitrile resin particles in a stable state, the dispersion stability of the ink composition is further improved, and the color development of the handwriting, This is effective because the ink dischargeability from the pen tip can also be improved. Such a method is preferable because the dispersion stability of the ink composition and the color development of the handwriting can be further improved. The styrene-acrylonitrile resin particles used here are preferably those obtained by emulsion polymerization. Moreover, it is preferable to colorize under a normal pressure and 60-90 degreeC.

  When forming the colored resin particle dispersion, the blending amounts of the styrene-acrylonitrile resin particles, the coloring agent and the polyglycerin fatty acid ester are respectively styrene-acrylonitrile resin particles based on the total mass of the colored resin particle dispersion. Is preferably 20 to 60% by mass, the colorant is 0.1 to 5% by mass, and the polyglycerin fatty acid ester is preferably 0.1 to 5% by mass.

<< Writing Instruments >>
The structure and shape of the writing instrument filled with the aqueous ink composition for a writing instrument according to the present invention are not particularly limited, and those generally used conventionally can be applied, and fiber tips, felt tips, plastic tips or ballpoint tips etc. It can be used for various writing instruments such as marking pens, ballpoint pens, and pens made of metal.

  Moreover, as a writing instrument which can use the ink composition of this invention, it may be a thing of the structure which is directly filled with an ink composition, and an ink container or ink occlusion which can be filled with an ink composition. It may have a body. In addition, the ink container type or ink storage type may be an ink cartridge type writing tool having a structure that can be detachably replaced with the writing tool main body.

  In addition, a writing instrument which can use the ink composition of the present invention is a cap-type writing instrument provided with a cap for covering the pen tip, and an insertion and retraction that can accommodate the pen tip in a knock type, rotary type and slide type shaft cylinder. Examples include a ballpoint pen.

  Further, the supply mechanism of the writing instrument which can use the ink composition of the present invention is not particularly limited, and, for example, an ink induction core composed of (mechanism 1) fiber bundle etc. is provided as an ink flow rate adjusting member A mechanism for supplying the composition to the pen point, (Mechanism 2) An ink flow rate adjusting member in the form of a comb groove is interposed and a mechanism for supplying the ink composition to the pen point, (Mechanism 3) It may be provided with a control member, a mechanism for supplying the ink composition to the pen point, and (Mechanism 4) a mechanism for directly supplying the ink composition to the pen point without the ink flow rate control member.

  When the specifications of the ballpoint pen when the water based ink composition for writing instruments of the present invention was filled in a ballpoint pen were examined, the ink consumption per 100 m of the water based ballpoint pen was A (mg) and the ball diameter was B (mm) It is preferable to set it as the relationship of 150 <= A / B <= 500, and it is preferable to set it as the relationship of 250 <= A / B <= 450. In this range, by setting the ink consumption to an appropriate amount with respect to the ball diameter by setting it in the above-mentioned range, the ink flowability is made favorable, and a good handwriting can be easily obtained by suppressing handwriting blur and the like. It is.

  Regarding ink consumption, under the conditions of 20 ° C, writing paper JIS P3201 writing paper with writing angle of 65 °, writing load of 100 g, writing speed of 4 m / min, using 5 test samples and spiral A writing test is conducted, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m. The ball diameter is not particularly limited, but generally, a ball of about 0.1 to 2.0 (mm) is used.

Further, with regard to the specification of the ballpoint pen tip, the movable amount (clearance) of the ball in the ballpoint pen tip in the longitudinal direction is preferably 20 to 50 μm, and more preferably 30 to 45 μm. This is because if the above range is used, the ink discharge amount is appropriately adjusted to suppress line jumps and blurs and good handwriting is easily obtained, and if the clearance is within the above range, The ratio A / B is also easy to adjust.
The movable amount (clearance) of the ballpoint pen tip in the longitudinal axis direction of the ball indicates the distance the ball can move in the longitudinal axis direction of the ballpoint pen tip body.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1
The aqueous ball point ink composition of Example 1 was obtained by the following composition and method.
・ Styrene-acrylonitrile resin particles (average particle size 0.4 μm) 20 mass%
・ Deca glycerin laurate 1.0 mass%
・ Colorant 0.5% by mass
(Pigment: pigment blue 15: 3)
・ Dextrin 1.0% by mass
· Ink viscosity modifier 0.4% by mass
(Shear thinning agent, succinoglycan)
· Lubricant 1.0% by mass
(Phosphate ester surfactant (Plysurf A208N, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polyoxyethylene alkyl (C12, 13) ether phosphate, HLB value: 7))
· Rust inhibitor 0.5% by mass
(Benzotriazole)
・ Antiseptic 0.1% by mass
(1,2-benzisothiazolin-3-one)
・ PH adjustor 1.0 mass%
(Triethanolamine)
-Water soluble organic solvent 10.0 mass%
(ethylene glycol)
-Water-soluble organic solvent 2.5% by mass
(Diethylene glycol)
・ Water-soluble organic solvent 4.0 mass%
(Glycerin)
-Castor oil 2.5% by mass
・ Water remaining part

  Each component other than the above-mentioned ink viscosity regulator was heated and stirred with a magnet hot stirrer to prepare a base ink. Thereafter, while heating the base ink prepared above, an ink viscosity modifier (shear reducing viscosity imparting agent) is added and sufficiently mixed and stirred using a homogenizer stirrer until uniform state is obtained, and then a filter paper is used. The filtration was performed to obtain an ink composition. Furthermore, as a result of measuring the pH value of the ink composition at 20 ° C. using an IM-40S pH meter (manufactured by Toa DKK Co., Ltd.), the pH value was 7.9.

<< Preparation of Colored Resin Particle Dispersion>
Raw materials were blended as shown in Table 1 to prepare Colored Resin Particle Dispersions 1 to 9.

  For example, Colored Resin Particle Dispersion 1 was prepared as follows. A mixed solution obtained by uniformly mixing a polyglycerin fatty acid ester, a colorant, a preservative, a water-soluble organic solvent, a pH adjuster, and water with a styrene-acrylonitrile resin particle at normal temperature The mixture was added while stirring at 25 ° C. to obtain a uniform mixture. Thereafter, the temperature is gradually raised, and stirring is performed at 90 ° C. for 2 hours to color the styrene-acrylonitrile resin particles, whereby a colored resin particle dispersion 1 is produced.

<< Preparation of ink composition for aqueous ballpoint pen >>
Using the colored resin particle dispersions 1 to 9 obtained above, the raw materials were blended as shown in Table 2 to prepare ink compositions of Examples 2 to 13 and Comparative Examples 1 and 2.

  For example, the ink composition of Example 2 was prepared as follows. The colored resin particle dispersion 1, dextrin, lubricant, rust inhibitor, preservative, pH adjuster, water-soluble organic solvent, and water are heated and stirred with a magnet hot stirrer, etc. Base ink was prepared.

Thereafter, while heating the base ink prepared above, an ink viscosity modifier (shear reducing viscosity imparting agent) is added and sufficiently mixed and stirred using a homogenizer stirrer until uniform state is obtained, and then a filter paper is used. The filtration was performed to obtain an ink composition. Furthermore, as a result of measuring the pH value of the ink composition at 20 ° C. using an IM-40S type pH meter (manufactured by Toa DKK Co., Ltd.), the pH value was 8.1. In addition, the viscosity of the obtained ink composition was measured using an E-type rotational viscometer (model: DV-II + Pro, rotor: CPE-42, manufactured by Brookfield) at a shear rate of 1.92 sec ⁻¹ (in a 20 ° C. environment). The ink viscosity was measured under the conditions of a rotation speed of 0.5 rpm, and it was 1680 mPa · s.

Further, using an E-type rotational viscometer (model: DV-II + Pro, rotor: CPE-42, manufactured by Brookfield), under conditions of a shear rate of 1.92 sec- ¹ (rotation speed of 0.5 rpm) under an environment of 20 ° C. When the ink viscosity of the ink composition was measured, Example 7 had 1610 mPa · s and Example 8 had 1590 mPa · s.
Moreover, as a result of measuring pH value of the ink composition in 20 degreeC using IM-40S type pH meter (made by Toa DKK Co., Ltd.), all the ink compositions of Examples 1 to 13 are within the range of pH 6 to 10 Met.

The polyglycerin fatty acid ester used was as follows.
Decaglycerin laurate: Poem J-0021 (trade name, manufactured by Riken Vitamin Co., Ltd., HLB value 15.5, molecular weight 980)
Decaglycerin stearate: Poem J-0081HV (trade name, manufactured by Riken Vitamin Co., Ltd., HLB value 12, molecular weight 1020)
Decaglycerine oleate: Poem J-0381V (trade name, manufactured by Riken Vitamin Co., Ltd., HLB value 12, molecular weight 1060)

<< Preparation of water-based ink composition for writing instrument >>
Using the colored resin particle dispersion obtained above, an ink composition having the configuration shown in Table 2 was produced.

  For example, colored resin particle dispersion 1, dextrin, lubricant, rust inhibitor, preservative, pH adjuster, water-soluble organic solvent, and water are heated and stirred with a magnet hot stirrer, etc. The base ink was prepared.

  Thereafter, while heating the base ink prepared above, an ink viscosity modifier (shear reducing viscosity imparting agent) is added and sufficiently mixed and stirred using a homogenizer stirrer until uniform state is obtained, and then a filter paper is used. The filtration was performed to obtain an ink composition.

  The obtained ink composition was evaluated by the following method.

Dispersion stability test
The ink compositions of Examples 1 to 13 and Comparative Examples 1 and 2 are put in a closed test glass tube having a diameter of 15 mm and left at 50 ° C. for 30 days, and then the state of the ink composition is observed with an optical microscope The dispersion stability of the ink composition was evaluated using the following evaluation criteria. The evaluation is as summarized in Table 2.
A: Good state in which aggregates are not confirmed and uniformly dispersed.
B: Aggregates were slightly confirmed, but at a level at which there was no problem in practical use.
C: Aggregates were confirmed, and there was a level of concern in practical use.
D: Settling of aggregates was observed.

<< Preparation of test ballpoint pens >>
A ballpoint pen tip (the longitudinal axis of the ball) in which the ink composition (1.0 g) of each of Examples 1 to 13 and Comparative Examples 1 and 2 is rotatably supported by a cemented carbide ball having a diameter of 0.7 mm. Refill filled in the inside of the ink container having the movement amount (clearance) of 30 μm in the direction is prepared, and this refill is attached to a gel ink ballpoint pen (trade name: G-2) manufactured by Pilot Corporation. I got a ballpoint pen. The obtained ballpoint pen was used as a test ballpoint pen, and the following test and evaluation were performed.

<Character writing performance test>
Using a test ball pen that has been confirmed to be writable, write 15 letters (about 8 mm in length and width of letters) on a test sheet (JIS P3201, writing sheet A) continuously and obtain The situation was visually confirmed, and the initial character writing performance was evaluated by the following evaluation criteria. The results are as summarized in Table 2.
A: A good handwriting was obtained with good coloring and no line jumps or streaks.
B: Striking lines and streaks were slightly confirmed in the writing, but good coloring was obtained.
C: Strokes and streaks were found in the handwriting, but this was at a level that causes no problem in practical use.
D: A large number of strokes and streaks were observed in the handwriting, and good handwriting was not obtained, and some were found to be incapable of writing.
Further, after the used ball point pen was left at 50 ° C. for 60 days, the same test was conducted to evaluate the character writing performance after aging based on the same standard as described above.

<Helix writing performance test>
Using a test ball pen confirmed to be writable, write a spiral circle continuously on a test sheet (JIS P3201, writing sheet A) by handwriting, and visually check the state of the obtained handwriting visually The following evaluation criteria evaluated the initial spiral writing performance. The results are as summarized in Table 2.
A: A good handwriting was obtained with good coloring and no line jumps or streaks.
B: Strokes and streaks were observed in the writing, but good coloring was obtained.
C: Strokes and streaks were confirmed in the handwriting, which was at a level that does not cause any practical problems.
D: A large number of strokes and streaks were observed in the handwriting, and good handwriting was not obtained, and some were found to be incapable of writing.
Further, after the used ball point pen was left at 50 ° C. for 60 days, the same test was performed to evaluate the spiral writing performance after aging based on the same standard as described above.

（１）サンデックシリーズ、三和澱粉工業株式会社製、
（２）サンデックシリーズ、三和澱粉工業株式会社製、
（３）三晶（株）製、
（４）プライサーフＡ２０８Ｎ、第一工業製薬株式会社製、ポリオキシエチレンアルキル（Ｃ１２，１３）エーテルリン酸エステル、ＨＬＢ値：７
（５）エポスターＭ０５、株式会社日本触媒製、平均粒子径５μｍ

(1) Sandeck series, manufactured by Sanwa Starch Co., Ltd.
(2) Sandeck series, manufactured by Sanwa Starch Co., Ltd.
(3) Sanki Co., Ltd. product,
(4) Plysurf A 208 N, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polyoxyethylene alkyl (C12, 13) ether phosphate, HLB value: 7
(5) Eposer M05, manufactured by Nippon Shokubai Co., Ltd., average particle diameter 5 μm

  From the results of Table 2, the ink composition according to the present invention was at a good level in dispersion stability and writing performance (initially, after storage at 50 ° C. for 60 days).

  Furthermore, a 40 g weight is attached to the barrel portion of the test ballpoint pen, the ballpoint pen tip is discharged and turned downward, and the ballpoint of the ballpoint pen tip is kept in contact with the bottom of the ballpoint pen display case. It was left to stand in an environment of RH for 1 day, and the amount of ink leakage from the tip of the ballpoint pen tip was measured to conduct an ink leakage test. As a result, the ink of Example 10 comprising resin particles (excluding styrene-acrylonitrile resin particles) The ballpoint pen using the composition has a smaller amount of ink leakage than a ballpoint pen using an ink composition not containing resin particles (except for styrene-acrylonitrile resin particles), and a ballpoint pen using the ink composition of Example 10 Is an excellent ballpoint pen that has excellent dispersion stability, writing performance, and can also suppress ink leakage from the pen point It was found.

  Furthermore, with the pen point of the test ballpoint pen exposed to the atmosphere, after standing for 1 day under conditions of 50 ° C. and total dryness, continuously write letters (size of letter 8 mm by 8 mm) on the test sheet and write When the number of characters until it was recovered to a recognizable level was counted, the ballpoint pen using the ink composition of Examples 1 to 11 and Example 13 containing dextrin contained the ink composition of Example 12 which did not contain dextrin. Compared to a ballpoint pen using the above, the number of characters before returning was small, and the dry-up resistance tended to be excellent.

A spiral writing test was conducted as an aqueous ballpoint pen using the ink compositions of Examples 2 and 7 after storage at 50 ° C. for 60 days, and the ink consumption per 100 m was A (mg), and the ball diameter was B (B In the case of mm), the relationship of A / B was as follows.
Example 2: A = 202 (mg), B = 0.7 (mm), A / B = 288
Example 7: A = 196 (mg), B = 0.7 (mm), A / B = 280
In addition, ink consumption per 100 m is 20 ° C, writing paper JIS P3201 writing paper using a writing speed of 4 m / min under the conditions of a writing angle of 65 ° and a writing load of 100 g using 5 test samples The spiral writing test was conducted to determine the average value of the ink consumption per 100 m.

  The ink composition of the present invention can be used for a writing instrument such as an aqueous ballpoint pen, and the writing instrument containing the ink composition can provide excellent characteristics.

Claims (9)

  An aqueous ink composition for a writing instrument, comprising styrene-acrylonitrile resin particles, a colorant, a polyglycerin fatty acid ester, and water.   The ink composition according to claim 1, wherein the carbon number of the alkyl group of the polyglycerin fatty acid ester is 10 to 20.   The ink composition according to claim 1, wherein a degree of polymerization of the polyglycerin fatty acid ester is 5 to 20. 4.   4. A polyoxyalkylene aryl ether according to any one of claims 1 to 3, comprising no or less than 0.5 wt% of a polyoxyalkylene aryl ether based on the total weight of the composition. Ink composition.   The ink composition according to any one of claims 1 to 4, wherein the content of the styrene-acrylonitrile resin particles is 12 to 35% by mass based on the total mass of the composition.   The ink composition according to any one of claims 1 to 5, further comprising a phosphoric acid ester surfactant.   An aqueous ink composition for a writing instrument, comprising styrene-acrylonitrile resin particles colored by a coloring agent, a polyglycerin fatty acid ester, and water.   The ink composition according to claim 7, further comprising another colorant different from the colorant or the colorant.   A writing instrument comprising the ink composition according to any one of claims 1 to 8.