JP5455441B2 - Water-based ballpoint pen ink composition - Google Patents

Description

  The present invention relates to an ink composition for water-based ballpoint pens. Specifically, the water-based ballpoint pen comprises an aqueous phase comprising a pigment dispersion, and a dye dissolved in the oily phase is contained in an oil-in-water emulsion type with respect to the aqueous phase. The present invention relates to an ink composition.

  A characteristic of the water-based ballpoint pen is that it has a low viscosity and a large amount of ink outflow, and a clear drawing line can be obtained with a light writing taste, but on the other hand, it has a drawback that it feels grity. A pigment or dye is used as the colorant. The pigment has an advantage of high weather resistance, but has a weak coloring power and a high drawing density is difficult to obtain. Further, when a large amount of pigment is added to increase the concentration, there arises a problem that the dispersion stability is impaired. Furthermore, variations in toning are not as good as dyes. On the other hand, the dye has the advantage that the coloring power and the degree of freedom of toning are high, but there are problems that the weather resistance is low and the drawn lines are likely to bleed when water adheres.

  Oil-based ballpoint pens have the advantages of high ink viscosity and low ink outflow, so that there is no harshness at the time of writing and there is little blurring of drawn lines. In addition, the dye that can be used as a colorant has water resistance because it has a molecular structure that is insoluble or hardly soluble in water, and is found in inks that use water-soluble dyes. No bleeding occurs.

  In recent years, oil-based ballpoint pens that improve the writing quality by reducing the viscosity of oil-based inks have been developed. However, low-viscosity oil-based inks increase the amount of writing outflow, so that the dryness of drawn lines deteriorates, causing ink to penetrate to the back side of the paper and cause voids.

  Japanese Patent Application Laid-Open No. 2004-156611 describes a low-viscosity oil-based ballpoint pen ink using a W / O organic solvent containing water as an organic solvent. However, this ink has a problem in storage stability, and most of the ink composition is an organic solvent. Therefore, if the amount of written outflow is increased, a strike-through occurs.

  In JP-A-2007-327003, water droplets composed of an aqueous component in which a pigment is dispersed by adding a pigment to the aqueous component in advance and mixing it with the oily component are dispersed in W / An O-type emulsion ink composition is described. A ballpoint pen ink with improved writing quality and the like has been disclosed by using this ink composition, but lacks stability such that water droplets coalesce and localize during long-term storage. Further, since the amount of the oil component in the ink composition is large, when the amount of writing outflow is increased as in the case of a water-based ballpoint pen, the showthrough and the deterioration of the drawn line dryness are remarkable.

  Japanese Patent Application Laid-Open No. 55-152768 discloses a writing that can be erased with an eraser, in which a colored composition obtained by dispersing a pigment in a polymer solution comprising a polymer and a solvent for dissolving the polymer is emulsified and dispersed in water. Ink for use is described. However, in this ink, the coloring material is a pigment, and the dispersed particles have a very high viscosity. Therefore, when used in a ballpoint pen, the writing property is poor, and the dispersed particles easily coalesce and settle, and the storage stability is also improved. There was a problem.

  Japanese Patent Application Laid-Open No. 2004-323618 discloses that an ink composition composed of a water-soluble ink containing a water-soluble dye and an oil-soluble ink containing an oil-soluble dye is shaken during writing to form an unstable emulsion. A multicolor ink for a writing instrument is described which is formed and whose writing lines are short and vary irregularly and continuously. This ink is described as being separated into two layers in a stationary state, and is not suitable as a normal ballpoint pen ink.

  Japanese Patent Application No. 2008-145150, which is a patent application devised by the present inventor, discloses an ink composition for water-based ballpoint pens that has the advantages of water-based ballpoint pens and oil-based ballpoint pens and whose ink properties are emulsions of oil-in-water droplets. Has been. The aqueous phase achieves a high spillage and light writing quality, and the oily phase of the oil film provides a writing quality that does not cause blurring or back-throwing and does not feel greasy. The invention described in the specification of Japanese Patent Application No. 2008-145150 is an unprecedented water-based ink composition for ballpoint pens, and has an excellent performance. On the other hand, this emulsion has a high viscosity and a solvent to be used. From the viewpoint of stability, a high boiling point is preferred. For this reason, the emulsion itself has low volatility. The ink has a problem that the dryness of drawn lines deteriorates when the emulsion concentration is high, and there is a problem that the drawn line density is insufficient when the concentration is low. As another problem, there is a problem that an emulsion mainly composed of a dye solution as a colorant has difficulty in light resistance. In Example 2 of Japanese Patent Application No. 2008-145150, a formulation in which carbon black is added is described, but this is not sufficient for solving these problems, and further improvements are desired.

JP 2004-115611 A JP 2007-327003 A JP 55-152768 A JP 2004-323618 A Japanese Patent Application No. 2008-145150

  As described above, each of the water-based ballpoint pen and the oil-based ballpoint pen has advantages and disadvantages. It is an object of the present invention to provide a novel water-based ballpoint pen ink composition that combines the advantages of both.

  As a result of diligent research, the present inventors have found that the above problem can be solved by combining an oily dye solution as an oil-in-water emulsion with an aqueous phase composed of a pigment dispersion, thereby completing the present invention. did.

That is, the present invention
(1) An ink composition for water-based ballpoint pens, in which an oily phase containing an oily solution in which a dye is dissolved in an organic solvent is contained in an oil-in-water emulsion type with respect to an aqueous phase comprising a pigment dispersion.

  (2) The solvent having one or more aromatic rings in the molecular skeleton in the total solvent of the oily solution occupies 50% or more by mass, and includes an emulsifier having one or more aromatic rings in the molecular skeleton. (1) The water-based ballpoint pen ink composition.

  (3) The water-based ballpoint pen ink composition according to (2), wherein the emulsifier includes at least an aromatic emulsifier having an ethylene oxide addition mole number of 40 or more.

  (4) The water-based ballpoint pen ink composition as described in any one of (1) to (3), wherein the oily solution has a boiling point of 200 ° C. or higher.

  (5) The solubility in water at 25 ° C. is 1% or less on a mass basis, and the solvent having one or more aromatic rings in the molecular skeleton occupies 50% or more on a mass basis in the total solvent of the oily solution. The water-based ballpoint pen ink composition as described in any one of (1) to (4) above.

  (6) The water-based ballpoint pen ink composition according to any one of (1) to (5), wherein an average particle size of oil droplets of the oil-in-water emulsion is 200 nm or less.

  (7) The water-based ballpoint pen ink composition according to any one of (1) to (6), wherein the ratio of the oil phase component in the ink composition is 1 to 20% on a mass basis.

  (8) The aqueous ballpoint pen ink composition according to any one of (1) to (7), wherein the dispersant contained in the pigment dispersion is a styrene acrylic resin.

  The ink composition for water-based ballpoint pens of the present invention is characterized in that the aqueous phase contains a pigment dispersion and the dye solution is contained in the form of an oil-in-water emulsion. As a result, in addition to the light writing taste that is an advantage of the conventional pigment-type water-based ballpoint pen and the water resistance and weather resistance of the pigment, the oil-in-water emulsion exhibits the following effects. In other words, the oil film of the oily phase provides a writing feeling that does not feel gritty, and the use of a dye enables an improvement in color density and a high degree of freedom in toning, and at the same time provides water resistance. . The present invention provides an aqueous ball-point pen ink composition having the advantages of water-based ball-point pen ink and oil-based ball-point pen ink and having good storage stability.

  In the ink composition of the present invention, the aqueous phase is composed of a pigment dispersion, and the aqueous phase includes an oily dye solution in the form of an oil-in-water emulsion. Hereinafter, components of the ink composition of the present invention will be described in detail.

  The oily phase of the ink composition of the present invention comprises an oily solution in which at least a dye as a coloring material is dissolved in an organic solvent. As the solvent for the oily solution, a solvent having an aromatic ring in the molecular skeleton is preferable from the viewpoint of dissolving the dye, and any solvent having an aromatic ring can be used. Preferably, the solvent having an aromatic ring in the molecular skeleton is preferably 50% or more, and most preferably 70% or more, based on mass with respect to the total solvent of the oily phase solution.

  In particular, considering that the dye can be dissolved, incompatible with water, the storage stability of the formed emulsion is good, and the safety is high, a more preferable solvent is one or more aromatics in the molecule. A ring having a solubility in water of 1 g / 100 g or less at 25 ° C. is preferable. If the solubility exceeds 1 g / 100 g, the resulting emulsion may become unstable and phase separation may occur over time. In the oily solution, the solvent having one or more aromatic rings in the molecule and having a solvent solubility in water of 1 g / 100 g or less at 25 ° C. is preferably 50% or more based on the total mass of the solvent, Most preferably, it is 70% or more.

The solvent that can be used in the oily solution of the present invention is preferably a relatively low-volatile solvent.
A solvent can consist of one type of solvent chosen from the example of the solvent shown below, or can consist of multiple types of solvents.

  Examples of the solvent that can be used in the oily solution of the present invention include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkyl sulfonic acid phenyl ester, and phthalic acid. Examples include butyl, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitic acid, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, xylene, toluene, and the like. Of these, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, alkyl sulfonic acid phenyl ester, ethyl hexyl phthalate, tridecyl phthalate, trimellit, having a solubility in water at 25 ° C. of 1 g / 100 g or less. Preferred examples of the solvent include ethylhexyl acid, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, liquid xylene resin, toluene, and xylene. Most preferably, among them, alkylsulfonic acid phenyl ester, ethylhexyl trimellitic acid, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, etc., having a solubility in water at 25 ° C. of 0.1 g / 100 g or less. Liquid xylene resin, toluene, xylene and the like are preferable solvents.

  Also, from the viewpoint of work safety for dissolving the dye and from the viewpoint of suppressing destabilization due to an increase in the internal pressure of the emulsion at a high temperature, a solvent having a boiling point of 200 ° C. or higher is preferable. Examples of preferred solvents are benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkyl sulfonic acid phenyl ester, butyl phthalate, ethyl hexyl phthalate, tridecyl phthalate , Ethylhexyl trimellitic acid, diethylene glycol dibenzoate, dipropylene glycol dibenzoate and the like.

  In addition, the oily solution of the present invention may contain an arbitrary auxiliary solvent in addition to the solvent having the aromatic ring. For example, a solvent selected from alcohols, polyhydric alcohols, glycol ethers, hydrocarbons, esters, and the like can be used, but a solvent that is infinitely compatible with water can diffuse into the aqueous phase, Should not be used in large quantities to cause coalescence. The mass% of the total solvent in the oil solution should be within 10%.

  The alcohol is preferably an aliphatic alcohol having 2 or more carbon atoms, such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl. Alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclone Hexanol and other wide variety of higher alcohols, and the like.

  The polyhydric alcohols are preferably polyhydric alcohols having 2 or more carbons and 2 or more hydroxyl groups in the molecule, such as ethylene glycol, diethylene glycol, 3-methyl-1,3-butanediol, and triethylene glycol. , Dipropylene glycol, 1,3 propanediol, 1,3 butanediol, 1,5 pentanediol, hexylene glycol, octylene glycol and the like.

  Examples of glycol ethers include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1 -Butanol, 3 Methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono Examples include propyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

  Examples of the hydrocarbons include linear hydrocarbons such as hexane, isohexane, heptane, octane, nonane and decane, and cyclic hydrocarbons such as cyclohexane, methylcyclohexane and ethylcyclohexane.

  Examples of co-solvents for esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate Propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, iso Ethyl butyrate, propyl isobutyrate, methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, Methyl limethyl acetate, ethyl trimethyl acetate, propyl trimethyl acetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, oleic acid Examples include various esters such as ethyl, triglyceride caprylate, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

  Further, as an auxiliary solvent having no hydroxyl group in the molecule, diether or diester can be used. Specifically, for example, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, Examples include dipropylene glycol dimethyl ether.

  The colorant in the oily phase of the ink composition of the present invention is a dye. Any dye used in general oil-based ink compositions can be used as long as the dye used is soluble in the above-described solvent. As oil-soluble dyes according to the present invention, direct dyes, acid dyes, basic dyes, mordant / acid mordant dyes, alcoholic-soluble dyes, azoic dyes, sulfurized / sulfurized vat dyes, vat dyes used in ordinary dye ink compositions Any of dyes, disperse dyes, oil-soluble dyes, food dyes, metal complex dyes, salt-forming dyes, dyes obtained by dyeing a resin, and the like can be used. Among these, alcohol-soluble dyes such as salt-forming dyes, oil-soluble dyes, and the like that are easily soluble in organic solvents are preferable from the viewpoints of solubility and emulsion stability. Particularly preferred dyes are oil-soluble dyes.

  The blending amount that is the lower limit of the dye is preferably 0.3% or more based on the mass of the total amount of the ink composition. If it is less than 0.3%, the coloring power is insufficient. Moreover, it is preferable that the compounding quantity used as an upper limit will be 70% or less on the mass basis of the total amount of oil-based solution. If it exceeds 70%, it is difficult to dissolve the dye, which is not preferable as a ballpoint pen ink composition. Particularly preferred is a range of 1 to 3% based on the mass of the ink composition and a range of 10 to 60% based on the mass of the oily solution.

  Salt-forming dyes used in oil-based ink compositions include Paris First Color (registered trademark, manufactured by Orient Chemical Industry Co., Ltd.), Eisenspiron dye, Eisen SOT dye (registered trademark, Hodogaya Chemical Co., Ltd.) ) Made).

  Examples of the dye in which a dye is dyed on a resin include the keiko-Colot MPI-500 series, the keiko-Colot MPI-500C series, and the keiko-Colot NKS-1000 series (registered trademark, manufactured by Nippon Fluorescent Chemical Co., Ltd.).

  A small amount of pigment can be used in combination with a dye as long as the colorant in the oily phase can maintain the stability of the emulsion. When a pigment is used, the amount of the pigment is preferably 10% or less based on the mass of the oily solution. If it exceeds 10%, the stability of the emulsion is impaired.

  Pigments that can be used in combination with dyes in the oily phase include inorganic pigments such as carbon black and titanium oxide, phthalocyanine pigments, azo pigments, diketopyrrolopyrrole pigments, anthraquinone pigments, perylene pigments And various organic pigments such as isoindolinone pigments and quinacridone pigments.

  Resin can be used in the oily solution for preparing the ink composition of the present invention in order to adjust the viscosity. The viscosity of the oily solution is preferably 500 to 1,000,000 mPa · s at 25 ° C. and a shear rate of 3.83 / sec without containing an emulsifier. When the viscosity is less than 500 mPa · s, the writing feels gritty and it is difficult to exhibit the side performance as an oil-based ink due to the oil-in-water type. Furthermore, it is not preferable for the stability of the emulsion. If it exceeds 1,000,000 mPa · s, a heavy writing feeling is obtained, which is not preferable as an ink composition for a ballpoint pen. A viscosity range of 3,000 to 500,000 mPa · s at 25 ° C. and a shear rate of 3.83 / sec is particularly preferred.

  Specific examples of resins that can be used in the ink composition of the present invention include ketone resins, sulfoamide resins, maleic resins, terpene resins, terpene phenol resins, ester gums, xylene resins, alkyd resins, phenol resins, rosins, Examples thereof include natural and synthetic resins such as polyvinyl pyrrolidone, polyvinyl butyral, polyvinyl alcohol, acrylic resin, melamine resin, and cellulose resin, and one or more of them can be used.

  The amount of the dye and other additives in the oily solution is preferably 3 to 70% based on the mass of the total oily solution as a solid content concentration. If the solid content concentration is less than 3%, sufficient viscosity cannot be imparted. If it exceeds 70%, it is difficult to dissolve the dye, which is not preferable as a ballpoint pen ink composition. The solid content concentration is particularly preferably in the range of 10% to 60%.

  The aqueous phase of the ink composition of the present invention comprises a pigment dispersion. For example, this pigment dispersion is a pigment dispersion using ion-exchanged water and purified water. Examples of pigments include inorganic pigments such as carbon black and titanium oxide, phthalocyanine pigments, azo pigments, diketopyrrolopyrrole pigments, anthraquinone pigments, perylene pigments, isoindolinone pigments, quinacridone pigments, etc. Organic pigments can be used.

  For example, C.I. I. Pigment Black 1, 7, C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 34, 35, 42, 53, 55, 65, 73, 74, 75, 81, 83, 86, 93, 94, 95, 97, 98, 99, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151.153, 154 155, 166, 167, 168, 173C, 174, 180, 185, etc., C.I. I. Pigment Red 1, 2, 3, 5, 7, 8, 9, 10, 12, 16, 17, 19, 22, 38, 41, 43, 48, 48: 2, 48: 3, 49, 50: 1 52, 53, 53: 1, 57, 57: 1, 58: 2, 60, 63: 1, 63: 2, 64: 1, 86, 88, 90, 9, 112, 122, 123, 127, 146 149,166,168,170,175,176,177,179,180,181,184,185,189,190,192,194,198,202,206,207,209,215,216,217,220, 223, 224, 226, 227, 228, 238, 240, 245, 254, 225, etc., C.I. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 22, 25, 60, 64, 66, etc., C.I. I. Pigment Orange 5, 10, 13, 16, 36, 40, 43, 48, 49, 51, 55, 59, 61, 71, C.I. I. Pigment Violet 1,3,5: 1,16,19,23,29,30,31,33,36,37,38,40,42,50, C.I. I. Pigment Green 7, 10, 36 etc., C.I. I. Pigment Brown 23, 25, 26 and the like.

  The color of the pigment dispersed in the aqueous phase and the color of the dye dissolved in the oily phase may be the same or different. When a dye having the same color as the pigment is used, the color of the ink is improved and the color density is improved by the dye. When a dye having a color different from that of the pigment is used, a toning variation with a high degree of freedom can be obtained.

  Various commercially available dispersants for obtaining the pigment dispersion can be used, and are not particularly limited. However, from the viewpoint of compatibility with coexisting oil-in-water emulsions and storage stability, a polymer resin A system dispersant is preferable, and a material different from a material used as an emulsifier used for forming an emulsion is preferable. For example, a styrene acrylic resin or a polyoxyethylene dispersant can be used. A particularly preferred dispersant is a styrene acrylic resin which is a high molecular polymer.

  The amount of the pigment used here is 3 to 15%, preferably 5 to 10%, based on the total mass of the ink composition. When the amount of the pigment is 3% or less, as the main component of the colorant, the light resistance is deteriorated, and the density of the drawn line is lacking. When the amount of the pigment is 15% or more, it is not preferable from the viewpoint of dispersion stability of the pigment. The amount of the dispersant used is preferably in the range of 20 to 100% with respect to the total mass of the pigment in the pigment dispersion.

  Examples of the method for dispersing the pigment in the aqueous phase include a method of uniformly mixing each component with a mixing stirrer, and a dispersing machine such as a ball mill, a bead mill, a roll mill, a homomixer, a disper, an ultrasonic dispersing machine, and a high-pressure homogenizer. Can be used.

  In addition, the aqueous phase can contain additives intended to prevent ink freezing at low temperatures and to prevent ink drying at the nib, specifically, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol. , Polyethylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycols such as glycerin, ethers such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether, and the like can be used alone or in combination. The amount of the additive used is 0 to 50%, preferably 0 to 30%, based on the mass of the aqueous phase. Addition of 50% or more causes a problem in the stability of the resulting emulsion.

  The aqueous phase contains an emulsifier to mix with the oily solution described above to form a stable emulsion. The emulsifier that forms a long-term stable emulsion by mixing with the main solvent of the oily solution according to the present invention is an emulsifier having one or more aromatic rings in the molecular skeleton. The emulsifier having one or more aromatic rings in the molecular skeleton is considered to form a long-term stable emulsion because the aromatic ring which is a lipophilic group has high affinity for the dye solution of the oily phase.

  The aromatic emulsifier that can be used in the ink composition of the present invention is not particularly limited as long as it has one or more aromatic rings. The properties of the emulsifier can usually be changed by the number of moles of ethylene oxide (EO) added. In relation to the main solvent used in the oily solution, those having an ethylene oxide addition mole number of 40 mol or more are preferable. This is because coalescence of the particles is suppressed by the long chain ethylene oxide chain.

  The above-mentioned emulsifier having an ethylene oxide addition mole number of 40 mol or more and an emulsifier having an ethylene oxide addition mole number of 3 to 15 mol which is strongly oriented to the oil phase can be used in combination. This is because it is considered that the micelle concentration at the interface is increased and the stability of the emulsion is increased by combining an oily phase having a strong orientation and an aqueous phase having a strong orientation.

  Regarding the HLB value (hydrophilic / lipophilic balance value), it is preferable to use at least one emulsifier having an HLB value of 15 or more for the nonionic surfactant. This is because even if the number of moles of ethylene oxide added is large, if the HLB value is low, the emulsifier is excessively taken into the oil phase.

  An emulsifier having 40 mol or more of ethylene oxide is a polycyclic phenyl type nonionic surfactant such as polyoxyethylene distyrenated phenyl ether, polyoxyethylene monostyrenated phenyl ether, polyoxyethylene cumyl phenyl ether, or ethylene oxide. Examples include those added with 40 mol or more of chain, and ionic surfactants such as sulfates thereof. The number of moles of ethylene oxide added is preferably 40 mol or more and 200 mol or less. In the case of an emulsifier added in an amount of 200 mol or more, the viscosity is remarkably increased and may be inappropriate for use.

  In addition, those having an ethylene oxide addition mole number of 3 to 15 include polycyclic phenyl type nonionic surface activity such as polyoxyethylene distyrenated phenyl ether, polyoxyethylene monostyrenated phenyl ether, polyoxyethylene cumylphenyl ether and the like. Examples of the agent include those obtained by adding 3 to 15 mol of ethylene oxide chain, ionic surfactants such as sulfates thereof, and alkylphenol type nonionic surfactants such as polyoxyethylene alkylphenyl ether.

  In addition to the surfactant having an aromatic ring in the molecule, any emulsifier having another structure can be additionally added as the emulsifier. Examples thereof include polyoxyethylene hydrogenated castor oil, linear hydrocarbon type nonionic surfactants such as polyoxyethylene alkyl (C10 to C18) ester, and sorbitan derivatives. The amount of the emulsifier is preferably 5 to 150%, and most preferably 10 to 100%, based on the mass of the oily solution.

  In addition to pigment dispersions and emulsifiers, the aqueous phase contains various additives commonly used in aqueous ballpoint pens, such as rust inhibitors, preservatives, pH adjusters, lubricants, moisturizers, resins, natural polysaccharides and the like. It can contain a sticking agent and the like.

  The ratio of the oil phase component in the oil-in-water type aqueous ballpoint pen ink composition of the present invention is 1 to 20%, preferably 3 to 15%, more preferably 5 to 10% on a mass basis. If the proportion of the oil phase component is less than 1%, satisfactory performance cannot be obtained with improved color density and writing property, and the water-based ballpoint pen is no different. On the other hand, if the proportion of the oil phase component is greater than 20%, the emulsion may become unstable due to the interaction with the pigment dispersion, and the oil content increases, which adversely affects the drawn line drying.

  The average particle size of the emulsion is preferably 200 nm or less, more preferably 150 nm or less. The reason why the average particle diameter is 200 nm or less is to suppress sedimentation of particles and coalescence due to collision between particles. The adjustment of the particle diameter can be controlled by an emulsification method to be described later, and can be refined by a mechanical shear force using an emulsifier such as a high-pressure homogenizer.

As the emulsification method of the oil-in-water emulsion of the present invention, various emulsification methods known in the prior art, for example, phase inversion emulsification method, D phase emulsification method, PIT emulsification method, and mechanical emulsification method may be used. it can. For example, in the phase inversion emulsification method, the oil-in-water emulsion of the present invention is produced by the following steps:
a) stirring an oily solution component containing at least a dye as a coloring material in an organic solvent to dissolve solids;
b) adding an emulsifier to the aqueous component and stirring to dissolve it;
c) A step of gradually adding the aqueous component obtained in step b while stirring the oily solution obtained in step a to obtain a water-in-oil emulsion.
d) A step of adding an aqueous component while stirring to obtain an oil-in-water emulsion through phase transition.

In the step of preparing the aqueous phase containing the pigment dispersion, a conventionally known method can be adopted as the aqueous pigment ink. For example:
a) a step of stirring the pigment, dispersant, solvent and pH adjuster with a stirrer for 3 hours;
b) a step of dispersing in a sand mill for 5 hours;
c) a step of removing coarse particles of the pigment dispersion with a centrifuge;
d) A step of diluting the pigment dispersion and adding other components.

  The oil-in-water emulsion prepared as described above and the aqueous phase containing the pigment dispersion are mixed with stirring. In this stirring and mixing, for example, each component is dispersed using a method of uniformly mixing each component with a mixing stirrer or a dispersing machine such as a ball mill, a bead mill, a roll mill, a homomixer, a disper, an ultrasonic disperser, or a high-pressure homogenizer. A mixing method can be used. At this time, the oil phase component and the aqueous phase component may be stirred and mixed or dispersed and mixed simultaneously, and each component may be stirred and mixed or dispersed and mixed sequentially.

  In addition, a pigment dispersion prepared in advance may be used as an aqueous component in the production of an oil-in-water emulsion, but it may have an adverse effect on the pigment dispersion when phase transition is performed by phase inversion emulsification or the like. The oil-in-water emulsion production process and the pigment dispersion process are preferably performed separately.

  The viscosity of the ink composition for water-based ballpoint pens of the present invention is preferably 25 ° C., and the viscosity at a shear rate of 380 / sec is 1 to 100 mPa · s, more preferably 5 to 50 mPa · s. When it is 100 mPa · s or more, the viscosity of the ink is increased, and the followability of the ink in the ink refill is deteriorated.

  The preferred embodiments of the present invention and the excellent effects thereof will be specifically described below with the most representative examples. In the following, all parts are parts by mass, and all% are% by mass.

For Examples 1 to 18, ink compositions were prepared as follows.
First, the oily solution components shown in Table 1 were heated to a temperature of 50 ° C. to 60 ° C. while stirring to completely dissolve these components. The oil solution viscosity in the table is the value of this solution. Separately, the emulsifiers listed in Table 2 were dissolved in purified water with stirring to prepare an aqueous emulsifier solution. In addition, when mix | blending an emulsifier with strong orientation to an oily phase, it can also add to the said oily solution and stir at normal temperature.

  Next, the aqueous emulsifier solution was gradually added to the oily solution while stirring to invert the phase from w / o to o / w to obtain an oil-in-water emulsion. Then, about Examples 1-4, 6-9, 11-18, and the comparative example 4, the emulsification process was performed until it reached | attained the predetermined average particle diameter using the commercially available high pressure homogenizer. In Examples 5 and 10, the high-pressure homogenizer treatment was not performed.

  The average particle size was measured using a particle size measuring device N4Plus (manufactured by COULTER). At the time of measurement, the sample was diluted with water until the recommended concentration of N4Plus was reached, and the measurement was performed at a temperature condition of 25 ° C. In addition, the term of the average particle diameter used in the present specification refers to the median diameter.

A pigment dispersion having a pigment concentration of 20% was separately prepared according to the above steps.
The prepared pigment dispersion was subjected to dilution in step d) and addition of other components so that the final ink component amounts were as shown in Table 2. At that time, the amount of each component used in the emulsifier aqueous solution was adjusted to be reduced.

  The oil-in-water emulsion and the pigment dispersion are mixed and stirred with a disper, and for Examples 10, 11, 16 and Comparative Example 4, the thickener component is finally stirred and dissolved. An ink composition was obtained.

  For measurement of the viscosity of the ink, a rheometer manufactured by HAAKE, Rheo Stress 600, was used. A cone cone having a diameter of 20 mm and an inclination angle of 1 degree was used. The measurement conditions were a 25 ° C. shear rate of 380 / sec, and a stable value measured for 30 seconds was taken as the viscosity.

  Each composition produced in Examples 1 to 18 was incorporated into a UMR-07 refill manufactured by Mitsubishi Pencil Co., Ltd., and the following evaluation was performed.

  As Comparative Examples 1 to 4, ink compositions described in Table 3 were prepared. Comparative Example 4 is the ink composition of Example 1 of Japanese Patent Application No. 2008-145150, which is the prior application of the applicant of the present application. For Comparative Example 1, Mitsubishi Pencil Co., Ltd. SA-07N Refill, for Comparative Examples 2 and 4, Mitsubishi Pencil Co., Ltd. UMR-07 Refill, for Comparative Example 3, Mitsubishi Pencil Co., Ltd. UB157 Each shaft was filled with ink and evaluated.

<Evaluation>
(A) Sedimentation resistance test The refill with the pen tip facing the centrifugal direction was centrifuged for 5 hours under the conditions of a rotation radius of 20 cm and a rotation speed of 2000 rpm (about 900 G), and then the writing paper had a diameter of about 2 cm. A circle was written and compared with the drawn line concentration before centrifugation.
A: No difference in density from the initial value.
○: Slightly dark line, but no problem with writing.
Δ: It can be clearly recognized that the drawn line is dark, but writing is possible.
◆: The drawn line is dark and the wrinkled writing is conspicuous and cannot be used.
×: Writable

(B) Lightness test of writing feeling Five rounds were written on writing paper, and the lightness of writing feeling was determined as follows.
A: Very light.
○: Light.
Δ: Normal.
◆: Heavy.
X: Unbearable for use.

(C) Grit feeling test The grit feeling of writing at the time of the lightness feeling test as described in (a) was determined as follows.
A: I don't care at all.
○: I feel a little, but there is no problem.
Δ: A little worrisome
◆: I am quite worried.
X: It is worrisome.

(D) Water resistance test The drawn line on the writing paper was wetted with water, and the state after 1 minute was observed.
A: The drawn line does not change at all.
○: Slight blotting is observed, but there is no problem.
Δ: Striking of drawn lines is conspicuous but can be distinguished.
X: Difficult to distinguish.

(E) Light resistance test The drawn line written on the writing paper was exposed to sunlight for 12 hours to determine the degree of fading.
A: No fading.
○: Although fading slightly, it is clearly visible.
Δ: Remaining drawn lines can be confirmed.
X: Not visible at all.

(F) Drawing density test The writing line drawn on the writing paper was visually compared with the water-based ink and gel ink of the comparative example.
A: Darker than the comparative sample.
○: Equivalent to the comparative sample.
Δ: Slightly inferior to the comparative sample.
X: Inferior to the comparative sample.

(G) Line drawing dryness test The line drawn on the writing paper was rubbed with a piece of vinyl 10 seconds later to confirm the degree of elongation of the drawn line and contamination.
A: Not stretched at all and the drawn lines are not stained.
○: It hardly stretches and the drawn lines are not stained.
Δ: Slightly stretched drawn line
X: The drawn line is dirty.

(F) Storage stability test The pen body was allowed to stand for 3 months under the condition of 50 ° C, and the writing property was confirmed.
A: Initial and no change.
○: Although there is a slight change compared with the initial stage, there is no problem in writing.
Δ: Deterioration of the drawn line is observed, but writing is possible.
◆: The drawn line is significantly deteriorated.
×: Cannot be written.

  The results of the above tests are shown in Tables 4-6. From these results, it can be seen that the ink composition of the present invention shows superior results as compared with the comparative inks (oil-based ink, gel ink, water-based ink, the applicant's prior invention).

Claims (6)

An oily phase containing an oily solution in which a dye is dissolved in an organic solvent is contained in an oil-in-water emulsion state with respect to the aqueous phase composed of the pigment dispersion .
In the total solvent of the oily solution, the solvent having one or more aromatic rings in the molecular skeleton accounts for 50% or more on a mass basis,
Polycyclic aromatic having 40 or more moles of ethylene oxide selected from the group consisting of polyoxyethylene distyrenated phenyl ether, polyoxyethylene monostyrenated phenyl ether, polyoxyethylene cumylphenyl ether, and sulfates thereof A water-based ballpoint pen ink composition comprising a system emulsifier .   The water-based ballpoint pen ink composition according to claim 1, wherein the boiling point of the solvent of the oily solution is 200 ° C. or more.   The solubility in water at 25 ° C. is 1% or less on a mass basis, and the solvent having one or more aromatic rings in the molecular skeleton accounts for 50% or more on a mass basis in the total solvent of the oily solution. The ink composition for water-based ballpoint pens according to claim 1 or 2.   The ink composition for water-based ballpoint pens according to any one of claims 1 to 3, wherein an average particle diameter of oil droplets of the oil-in-water emulsion is 200 nm or less.   The water-based ballpoint pen ink composition according to any one of claims 1 to 4, wherein a ratio of the oil phase component in the ink composition is 1 to 20% on a mass basis.   The aqueous ballpoint pen ink composition according to any one of claims 1 to 5, wherein the dispersant contained in the pigment dispersion is a styrene acrylic resin.