JP2008231410A - Ink composition for writing material, and aqueous gel ink and aqueous marking pen ink using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition for a writing material that has solved particular problems associated with ink for a writing material when used as writing utensils, such as super-fine ballpoint pens, etc., realizes clear color writing and clear line drawing, and can maintain good feeling of writing due to its good temporal stability, and to provide an aqueous gel ink and aqueous marking pen ink using the same. <P>SOLUTION: The ink composition for a writing material comprises pigment particles wherein the ratio (MV/MN) of a mean volume average particle size (MV) to a mean number average particle size (MN) is ≤1.80. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink composition for stationery containing fine particles of build-up pigment, and an aqueous gel ink and an aqueous marking pen ink having excellent writing quality using the composition.

  Inks are usually compositions in which a colorant is contained in a solvent. Recently, functional inks with improved component compositions have been developed in order to meet various needs. For example, recently, a writing instrument with high performance and high added value has been proposed, and in order to cope with it, improved development of the ink material has been promoted. Specifically, a super extra-fine ball-point pen, an environmentally friendly marking pen, etc. are mentioned.

  As for ultra-fine ballpoint pens, there is one that maintains a certain writing quality by making the ball diameter of the pen tip ultrafine to 0.18 mm (Patent Document 1). The ballpoint pen is not particularly limited as a colorant, and a general dye or pigment is used, but the ball outer diameter and ink viscosity are adjusted to a specific range.

Here, regarding the water-based gel ink ball-point pen, it is generally composed of a pen tip (a ball and a chip holder holding the ball), an ink storage tube, a pen shaft, and a water-based gel ink. As the ink, water-based gel ink having an intermediate viscosity between water-based ink and oil-based ink and having a characteristic that ink viscosity decreases and flows out smoothly by rotation of the ball, that is, shear thinning viscosity is used. As a result, smooth writing can be realized even with an extremely fine nib. Such water-based gel inks have the following features: suppression of shaking (inhibition of ink outflow inhibition due to impact generated during writing), suppression of dry-up (inhibition of writing defects due to drying of the nib), suppression of DC phenomenon (from the tip of the tip) Inhibition of bleeding and so-called blurring and ejection of ink that naturally flows out), suppression of bleeding, and the like are required.
Usually, shaking and dry-up tend to occur when the structural viscosity of the ink is too large. On the other hand, the direct current phenomenon and bleeding tend to occur if they are too small. That is, they are contradictory properties and are not easy to satisfy at the same time. Furthermore, further research and development is desired to improve the writing quality in consideration of the compatibility with the structure of each pen.

  Next, the development of environmentally friendly marking pens can be mentioned. The ink used for this is required to be able to be easily erased after writing on a writing board and then lightly wiping the handwriting with a dry cloth. So far, in this product area, the performance has been improved by improving and changing the solvent instead of the colorant. Conventionally, there is a solvent using an organic solvent as a solvent (see Patent Document 2), but improvement in human influence, odor, irritation and the like has been demanded. A water-based ink using water as a solvent has been proposed (see Patent Documents 3 and 4). However, with the ink, there was a tendency for the writing board to become dirty when rubbing with a cloth or the like immediately after writing. This is due to the fact that the emulsion resin in the ink itself does not have a sufficient film formed immediately after drying. Thereby, when rubbing with a dry cloth or the like, the colorant and the release agent component remain on the writing board, and the writing board is soiled. In consideration of this, a marking pen ink for a writing board with improved emulsion has been proposed (see Patent Document 5).

  On the other hand, regarding pigments, techniques for making particles finer are being studied. As a general method for making fine particles, there is a breakdown method (pulverization method), but it is not suitable for making particles fine. This method requires a great amount of time and energy to sufficiently refine the particles, and the production efficiency is low. Moreover, the substance which can be used will also be limited. In contrast, attempts have been made to grow particles in the gas phase or in the liquid phase. For example, a method for preparing an aqueous dispersion in which pigment particles are precipitated in a liquid in a flask is disclosed (see Patent Documents 6, 7, and 8). However, the specific properties confirmed in the dispersions of pigment particles described in these are only properties suitable for inks for ink jet recording, and are shown in a patent (see Patent Document 8) in which viscosity is described. The dispersion has only a low viscosity (less than 5 mPa · s) suitable for ink jet recording ink. Aside from this, a method for obtaining organic pigment particles by a microchemical process has been disclosed (see Patent Documents 9 and 10), but the characteristics when this is used for stationery ink are not known.

JP 2006-181905 A Japanese Examined Patent Publication No. 62-9149 Japanese Patent Laid-Open No. 2-133477 Japanese Unexamined Patent Publication No. 1-225281 JP-A-6-16991 JP 2003-26972 A JP 2003-113341 A JP 2004-43776 A JP 2005-307154 A JP 2006-342304 A

  The present invention solves the problems specific to the above stationery ink when used in writing instruments such as ultra-fine ballpoint pens, realizes clear colored writing and drawing, and maintains good writing quality with high temporal stability. An object of the present invention is to provide an ink composition for stationery, a water-based gel ink and a water-based marking pen ink using the ink composition.

The above object of the present invention has been achieved by the following means.
(1) An ink composition for stationery, comprising pigment fine particles having a ratio (MV / MN) of volume average particle diameter (MV) to number average particle diameter (MN) of 1.80 or less.
(2) The ink composition for stationery according to (1), wherein the pigment fine particles are build-up pigment fine particles.
(3) The build-up pigment fine particles are obtained by bringing a pigment solution in which a pigment is dissolved in a good solvent into contact with a poor solvent in the presence of a dispersant to precipitate the pigment as nanometer-sized fine particles. And (2) the ink composition for stationery.
(4) The ink composition for stationery according to (3), wherein the pigment solution and the poor solvent are brought into contact with each other in the flow process in the flow path.
(5) The ink composition for stationery according to (3) or (4), wherein the pH of the pigment solution is changed by contacting the pigment solution with a poor solvent.
(6) A water-based gel ink comprising the stationery ink composition according to any one of (1) to (5).
(7) The aqueous gel ink according to (6), which exhibits non-Newtonian viscosity.
(8) The aqueous gel ink according to (7), wherein the n value of the non-Newtonian viscosity index is 0.40 to 0.80.
(9) The water-based gel ink according to any one of (6) to (8), wherein the ink is used for a ballpoint pen.
(10) Maltitol, reducing sugar containing maltitol as a main component, sorbitol, reducing sugar containing sorbitol as a main component, reducing oligosaccharide, reducing maltooligosaccharide, reduced starch degradation product, reducing dextrin, reducing maltodextrin, α-cyclo (6) to (9), wherein one or more selected from the group consisting of dextrin, β-cyclodextrin, and maltosyl cyclodextrin are contained as a moisturizing agent. Water-based gel ink.
(11) An aqueous marking pen ink comprising the stationery ink composition according to any one of (1) to (5).

The ink composition for stationery of the present invention, when used as a water-based gel ink, simultaneously suppresses vibration blurring, dry-up, direct current phenomenon, and bleeding, achieves clear colored writing and drawing, and has high temporal stability, It has the excellent effect of suppressing discoloration and alteration when stored or used by being incorporated into various writing instruments and maintaining excellent writing taste for a long period of time.
The ink composition for stationery of the present invention, when used as a water-based marking pen ink for a writing board, maintains excellent writing quality with a high stability over time, and further with a cloth while leaving a dark and clear handwriting. There is an excellent effect that it can be easily wiped off.

The present invention is described in detail below.
In the present invention, the “build-up method” refers to a method of forming pigment fine particles from a pigment or pigment precursor dissolved (molecularly dispersed) in a solvent through a chemical reaction (including change in solubility). According to this build-up method, it is possible to efficiently form nanometer-sized pigment fine particles, particularly organic pigment fine particles, which are difficult to form by the breakdown method. In the present invention, pigment fine particles formed by the build-up method are defined as “build-up pigment fine particles”.

  In the present invention, the liquid phase method is preferable among the build-up methods, and the coprecipitation method is more preferable. In the present invention, the coprecipitation method is a method in which a pigment solution in which a pigment is dissolved in a good solvent (molecular dispersion) is gradually brought into contact with a poor solvent (such as an aqueous medium) to precipitate the pigment. This is a method for forming fine particles. The mode of coexisting the dispersant in the coprecipitation method is not particularly limited, but it is preferable to contain the dispersant in either or both of the pigment solution and the poor solvent, thereby improving the dispersion stability during the precipitation of the fine particles. It can be improved effectively. In the coprecipitation method, when a dispersant is not allowed to coexist, the fine particle formation method may be particularly distinguished from the “reprecipitation method”.

  In the present invention, when the build-up pigment fine particles are formed by the coprecipitation method, it is preferable to change the hydrogen ion index (pH) of the pigment solution by bringing the pigment solution into contact with a poor solvent. When the pigment fine particles are precipitated from the pigment dissolved in the alkali, the change of the hydrogen ion index (pH) is preferably lowered within the range of pH 16.0 to 5.0, and pH 16.0 to 10.0. It is more preferable to lower within the range. When pigment fine particles are precipitated from a pigment dissolved in an acid, the pH is preferably increased within the range of pH 1.5 to 9.0, and more preferably increased within the range of pH 1.5 to 4.0. . The width of the change depends on the value of the hydrogen ion exponent (pH) of the pigment solution, but may be a width sufficient for prompting the precipitation of the pigment. As described above, the formation of fine particles through a chemical reaction of pH change is preferable because stable pigment fine particles can be obtained.

  In the present invention, it is preferable to deposit pigment fine particles by bringing the pigment solution and the poor solvent into contact with each other in the flow process in the flow path. By carrying out in this way, it is possible to carry out the pigment fine particles under uniform conditions as compared with the batch method in which the precipitation is carried out in a normal reaction kettle. More preferably, it is carried out under a laminar flow or a transient state located between laminar flow and turbulent flow, and it is particularly preferred to carry out in a laminar flow process. Laminar flow and turbulent flow are described as follows. When water is poured into the tube, a thin tube is inserted into its central axis and colored liquid is injected, the colored liquid flows as a single line while the flow rate of water is low, and the water flows on the tube wall. It flows straight in parallel. However, when the flow velocity is increased and reaches a certain flow velocity, the water flow suddenly becomes turbulent, and the colored liquid is mixed with the water flow to become a colored flow. The former flow is called laminar flow, and the latter flow is called turbulent flow. This is called a transient flow.

Whether the flow becomes laminar or turbulent depends on whether or not the Reynolds number, which is a dimensionless number indicating the state of the flow, is below a certain critical value. The smaller the Reynolds number, the easier it is to form a laminar flow. The Reynolds number Re of the flow in the pipe is expressed by the following equation.
Re = D <υ _x > ρ / μ
D is the equivalent diameter of the tube, <υ _x > is the average cross-sectional velocity, ρ is the density of the fluid, and μ is the viscosity of the fluid. As can be seen from this equation, the smaller the equivalent diameter, the smaller the Reynolds number. Therefore, in the case of an equivalent diameter of μm, it becomes easy to form a stable laminar flow. It can also be seen that the liquid physical properties of density and viscosity also affect the Reynolds number, and the smaller the density and the larger the viscosity, the smaller the Reynolds number and the easier it is to form a laminar flow.

The critical Reynolds number at which the flow changes is called the critical Reynolds number. The critical Reynolds number is not necessarily constant, but the following value is the standard (see Fumimaru Kanno, “Chemical Engineering Handbook”, p37, 2004, Asakura Shoten).

Re <2300 laminar flow
Re> 4000 Turbulence
4000 ≧ Re ≧ 2300 Transient state

As a flow in a transient state, for example, there are a Karman vortex and a Taylor vortex that are flows including a laminar vortex region to a turbulent region. Details of the “non-laminar flow” including the Karman vortex and the Taylor vortex will be described later.
Particle formation (from nucleation to nucleation) in a laminar or transient (Re <4000) flow process, stabilizing the particle growth rate, resulting in small particle size and narrow distribution, turbidity A highly transparent pigment fine particle dispersion with a small amount of water can be efficiently prepared. Pigment fine particles formed by combining fine particle precipitation during the distribution process and fine particle precipitation due to the above-described change in pH are particularly preferable because of excellent particle size, distribution, and dispersion stability, and high production efficiency. In particular, low turbidity is related to pigment fine particles having a narrow particle size distribution (excellent monodispersity), thereby improving the writing quality of stationery ink.

  In the stationery ink composition of the present invention, it is preferable to use a microreactor device for forming the build-up pigment fine particles. In particular, it is preferable to use a microreactor apparatus that employs a solution confluence mode called a center collision type that can easily adjust a flow in a transient state from a laminar flow. FIG. 1 is an exploded perspective view schematically showing one embodiment of a center collision type microreactor apparatus. The three-dimensional microreactor apparatus 100 of this embodiment is mainly configured by a supply block 11, a merge block 12, and a reaction block 13 each having a cylindrical shape. In order to assemble the microreactor device 100, the cylindrical blocks 11, 12, and 13 are arranged in a cylindrical shape by aligning the side surfaces with each other in this order. For example, each block is bolted in this state.・ Tighten together with nuts.

  Two annular grooves 15 and 16 are formed concentrically on the side surface 14 of the supply block 11 facing the merging block 12. When the microreactor apparatus 100 is assembled, the two annular grooves 15 are assembled. And 16 form ring-shaped channels through which the liquid B and the liquid A flow, respectively. And the through-holes 18 and 17 which reach the outer side annular groove 16 and the inner side annular groove 15 from the opposite side surface 24 which does not oppose the confluence | merging block 12 of the supply block 11 are formed, respectively. A supply means (a pump, a connecting tube, etc.) for supplying the liquid A is connected to the through hole 18 that communicates with the outer annular groove 16 out of the two through holes 18 and 17, and communicates with the inner annular groove 15. Supply means (a pump, a connection tube, etc.) for supplying the liquid B is connected to the through-hole 17 that performs the above operation. In FIG. 1, the liquid A is allowed to flow in the outer annular groove 16 and the liquid B is allowed to flow in the inner annular groove 15.

  A circular junction 20 is formed at the center of the side surface 19 of the junction block 12 facing the reaction block 13, and four long radial grooves 21 and four short radial grooves 22 are formed radially from the junction 20. Alternately drilled. These merging holes 20 and radial grooves 21 and 22 form a circular space that becomes the merging region 20 and a radial channel through which the liquids A and B flow in the assembled state of the microreactor device 100. Further, among the eight radial grooves 21 and 22, through holes 25 are formed in the thickness direction of the merge block 12 from the tip of the long radial groove 21, and these through holes 25 are formed in the supply block 11. It communicates with the outer annular groove 16 described above. Similarly, through holes 26 are formed in the thickness direction of the merging block 12 from the tips of the short radial grooves 22, and these through holes 26 communicate with the inner annular groove 15 formed in the supply block 11.

Further, at the center of the reaction block 13, one through hole 23 communicating with the merging portion 20 is formed in the thickness direction of the reaction block 13, and this through hole 23 becomes a liquid mixing space including a micro flow channel.
As a result, the liquid A flows from the through hole 18 of the supply block 11 through the outer annular groove 16, through the through hole 25 of the merge block 12, and through the supply channel of the long radiation groove 21. The four divided flows reach the merging portion 20. On the other hand, the liquid B flows from the through hole 17 of the supply block 11 through the inner annular groove 15, through the through hole 26 of the merge block 12, and through the supply channel of the short radiation groove 22. The four divided flows reach the merging portion 20. The split flow of the liquid A and the split flow of the liquid B merge with the respective kinetic energy in the merge section 20, and then flow into the microchannel 23 by changing the flow direction by 90 °.

  It is also preferable to use a reactor having a Y-shaped channel as shown in FIG. FIG. 2 is an explanatory view of the reactor (200), and FIG. 3 is a sectional view taken along line III-III in FIG. In the apparatus of this aspect, for example, two types of liquids are supplied to the supply port 111 and the supply port 112, respectively. The shape of the cross section orthogonal to the length direction of each flow path varies depending on the microfabrication technique used, but a shape close to a trapezoid or a rectangle is preferable. The liquid injected from the introduction port 111 and the introduction port 112 by a pump or the like contacts at the fluid junction 113d via the introduction channel 113a (channel width X) and the introduction channel 113b (channel width Y), respectively. Then, a stable laminar flow is formed and flows through the reaction flow path 113c (flow path width Z, flow path length F, flow path depth H) that becomes the mixed region after the merge. And, for example, if it is a laminar flow state while flowing through the mixing region 113c (start point 113d, end point 114) as a laminar flow, they are mixed and reacted by molecular diffusion at the interface between the laminar flows. At this time, in the case of a substance with extremely slow diffusion, diffusion mixing between laminar flows does not occur, and mixing may be performed for the first time after reaching the discharge port 114. When the two liquids to be injected are easily mixed even in the flask, the flow of the liquid can be made uniform at the outlet if the flow path length F of the mixing region is long. On the other hand, even in such a combination, if the flow path length F is shortened, the laminar flow can be maintained up to the discharge port.

  In addition, a reaction apparatus having a cylindrical tube-type flow path, and an apparatus that has been improved so that it can be separated when the flow of the two liquids reaches the outlet in a laminar flow can be used (for example, JP 2005-2005). No. 307154, paragraphs 0049 to 52 and FIGS. 1 to 4). It is also preferable to use a planar microreactor or a three-dimensional microreactor in which the contact angle of two liquids and the number of contact flow paths are appropriately adjusted (for example, paragraphs 0053 to 0056 of JP-A-2006-342304 and FIGS. (See FIG. 3).

In the present invention, the build-up pigment fine particles may be formed by bringing the pigment solution and a poor solvent into contact with each other under non-laminar flow. Here, the “non-laminar flow” mentioned above is a flow including regular or irregular fluctuations, for example, from a laminar vortex region represented by a Karman vortex or a Taylor vortex to a turbulent region. The flow that contains.
As described above, a non-laminar flow is a flow that includes regular or irregular fluctuations. More specifically, as described above, a first viscous fluid (for example, water) is allowed to flow in the microchannel, and a tube that is thinner than the microchannel is inserted on the central axis of the microchannel. When two viscous fluids (for example, colored water) are injected, if the flow rate is sufficiently slow, the colored water becomes a single linear flow that does not include fluctuations and flows stably in parallel to the flow path axis. That is, it becomes a laminar flow. Then, when the flow velocity is gradually increased, the flow moves to an unstable and variable flow, and finally the second viscous fluid is mixed with the first viscous fluid in the turbulence caused by the variation. I will do it. That is, it continuously shifts from laminar flow to turbulent flow. At this time, regardless of whether the region is a laminar flow region or a turbulent flow region, there are regular and irregular forms of the flow variation described above, and the term “non-laminar flow” includes both of them.

  For example, flows including regular fluctuations include Karman vortices and Taylor vortices. On the other hand, as a flow including irregular fluctuations, there is a so-called turbulent flow in which generation and disappearance of various vortices of large and small dimensions are repeated randomly. Regarding non-laminar flow, (1) Chemical Engineering Handbook Revised 6th edition, Chemical Engineering Society, Maruzen Co., Ltd. (2) RIKEN Dictionary 5th edition, Iwanami Shoten, (3) M.M. Engler et al. , “Effective Mixing by the Use of Convenient Micro Mixers”, Conference Processings, 2005 Spring National Meeting, AIChE, 128d, etc., for example, can be referred to Japanese Patent Application Laid-Open No. 2006-342304. .

  In the present invention, the build-up pigment fine particles are preferably formed by the coprecipitation method in the laminar flow process, the coprecipitation method in the transient state, or the coprecipitation method in the non-laminar flow state. More preferably, it is formed by a coprecipitation method.

  In the present invention, the pigment is not limited in hue or structure. Examples of the organic pigment include perylene compound pigment, perinone compound pigment, quinacridone compound pigment, quinacridone quinone compound pigment, anthraquinone compound pigment, anthanthrone compound pigment, benzimidazolone compound pigment, disazo condensation compound pigment, disazo compound pigment, azo compound pigment , Indanthrone compound pigment, indanthrene compound pigment, quinophthalone compound pigment, quinoxalinedione compound pigment, metal complex azo compound pigment, phthalocyanine compound pigment, triarylcarbonium compound pigment, dioxazine compound pigment, aminoanthraquinone compound pigment, diketopyrrolo Pyrrole compound pigment, naphthol AS compound pigment, thioindigo compound pigment, isoindoline compound pigment, isoindolinone compound pigment, pyranthrone compound face , Isoviolanthrone compound pigment, or a mixture thereof.

  In the present invention, an inorganic pigment may be used as long as build-up pigment fine particles can be obtained by a build-up method, but an organic pigment is preferably used, among which anthraquinone compound pigment, naphthol compound pigment, perylene compound pigment, quinacridone Compound pigment, diketopyrrolopyrrole compound pigment, benzimidazolone compound pigment, disazo condensation compound pigment, metal complex azo compound pigment, dioxazine compound pigment, naphthtron compound pigment, phthalocyanine compound pigment, or indanthrene compound pigment, quinacridone compound More preferred are pigments, diketopyrrole compound pigments, disazo condensation compound pigments, or phthalocyanine compound pigments.

  In the present invention, the build-up pigment fine particles may be composed of a single pigment or a plurality of pigments. Furthermore, after forming as each pigment fine particle, the pigment composition which mixed them may be sufficient.

  The ink composition for stationery of the present invention is preferably prepared by the build-up method, particularly the pH conversion coprecipitation method. In the method of producing an organic pigment aqueous dispersion by the pH conversion coprecipitation method, the organic pigment must be uniformly dissolved in an organic solvent (which may be water-containing) that is basic or acidic and sufficiently mixed with water. Whether it dissolves acidic or basic is selected depending on which conditions the target pigment is easily dissolved. In general, in the case of a pigment having a group dissociable with a base in the molecule, the basicity is used. When there is no group dissociating with a base and there are many nitrogen atoms in the molecule that can easily add protons, acidity is used. For example, quinacridone, diketopyrrolopyrrole and disazo condensation pigments are basic, and phthalocyanine pigments are acidic.

  Bases used for basic dissolution are inorganic bases such as sodium hydroxide, calcium hydroxide or barium hydroxide, metal alkoxides such as sodium methoxide, sodium t-butoxide, potassium t-butoxide, or Organic bases such as trialkylamine or diazabicycloundecene (DBU) are used, and inorganic bases or metal alkoxides are preferable.

  The amount of the base used is an amount capable of uniformly dissolving the pigment, and is not particularly limited. However, in the case of an inorganic base, it is preferably 3 to 20 molar equivalents relative to the pigment, and preferably in the case of an organic base. 20 to 100 molar equivalents relative to the pigment.

  The acid used for acid dissolution is an inorganic acid such as sulfuric acid, hydrochloric acid, or phosphoric acid, or an organic acid such as acetic acid, trifluoroacetic acid, methanesulfonic acid, or trifluoromethanesulfonic acid, but is preferably an inorganic acid. is there. Particularly preferred is sulfuric acid.

  The amount of the acid used is an amount capable of uniformly dissolving the pigment, and is not particularly limited, but is often used in a large excess amount compared to the base. Regardless of the inorganic acid or organic acid, it is preferably 30 to 500 molar equivalents relative to the pigment.

  Next, an organic solvent that dissolves the pigment in the pH conversion coprecipitation method will be described. The organic solvent used is a solvent that can sufficiently dissolve the pigment by addition of a base or an acid, and an organic solvent that can be sufficiently mixed with water. For example, lower alcohol solvents such as methanol or ethanol, ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol Polyhydric alcohol solvents such as acetylene glycol derivatives, glycerin, or trimethylolpropane, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, or triethylene glycol monoethyl (or butyl) ether Lower alkyl ether solvents of polyhydric alcohols such as dimethylformamide, dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, Amide solvents such as 1,3-dimethyl-2-imidazolidinone, urea, or tetramethylurea, sulfur-containing solvents such as sulfolane, dimethyl sulfoxide, or 3-sulfolene, and polyfunctional solvents such as diacetone alcohol and diethanolamine , Carboxylic acid solvents such as acetic acid, maleic acid, docosahexaenoic acid, trichloroacetic acid or trifluoroacetic acid, and sulfonic acid solvents such as methanesulfonic acid or trifluorosulfonic acid.

  The preferred organic solvent is an amide solvent or a sulfur-containing compound solvent when basic, a carboxylic acid solvent or a sulfonic acid solvent when acidic, and more preferably a sulfur-containing compound when basic. If it is acidic, it is a sulfonic acid solvent. Particularly preferred is dimethyl sulfoxide (DMSO) when basic, and methanesulfonic acid when acidic.

  When the organic solvent contains water, the water / organic solvent mixing ratio is a ratio at which the pigment can be uniformly dissolved, and is not particularly limited. Generally, in the case of basic, it is substantially free of water or water / organic solvent = 0.005 to 10 (mass ratio). When an inorganic acid is used in the acidic case, it is preferable to use sulfuric acid alone, for example, without using an organic solvent. When an organic acid is used, the organic acid itself is an organic solvent, and a plurality of acids are mixed or water is added in order to adjust viscosity and solubility. Preferably, water / organic solvent (organic acid) = 0.005 to 0.1 (mass ratio).

  In the case where fine particles are formed in the flow channel, particularly in the micro space in the flow channel, it is preferable to introduce a uniformly dissolved solution into the flow channel. When the suspension is introduced, the particle diameter becomes large, or the pigment fine particles have a wide particle distribution. In some cases, the flow path is easily blocked. The meaning of “uniformly dissolved” is a solution in which turbidity is not observed when observed under visible light. In the present invention, the solution is obtained through a microfilter of 0.45 μm or less, or when it is passed through a 0.45 μm filter. A solution containing no matter to be filtered is defined as a uniformly dissolved solution.

Next, the hydrogen index (pH) will be described. The hydrogen index (pH) is a common logarithm of the reciprocal of the hydrogen ion concentration (molar concentration). The hydrogen ion concentration is the concentration of hydrogen ions H ⁺ in the solution, and means the number of moles of hydrogen ions present in 1 L of solution. Since the hydrogen ion concentration varies within a very wide range, the hydrogen ion concentration is usually expressed using the hydrogen index (pH). For example, pure water contains ^10-7 moles of hydrogen ions at 1 atmosphere and 25 ° C, so its pH is 7 and neutral. An aqueous solution with pH <7 is acidic, and an aqueous solution with pH> 7 is alkaline. As a method for measuring the pH value, there are a potentiometric method and a colorimetric method.

  In order to prepare the ink composition for stationery of the present invention, it is preferable to prepare pigment fine particles by changing the hydrogen index (pH) in the process of flowing through the flow path. This is performed using a flow path having an introduction port different from the introduction port. Specifically, a homogeneous solution in which an organic pigment is dissolved is introduced into one introduction port, a neutral, acidic or alkaline aqueous solution is introduced into the other introduction port, and both solutions are brought into contact with each other in the flow path E to generate hydrogen. The ion concentration, that is, the hydrogen index (pH) is changed to near neutrality.

  The change in the hydrogen index (pH) is a change in the range of about pH 15.0 to 5.0, and preferably pH 14.0 to 7.7 when pigment fine particles are produced from a pigment dissolved in an alkaline aqueous medium. It is a change within the range of 0. In the case of producing pigment fine particles from a pigment dissolved in an acidic aqueous medium, the change is generally within the range of pH 1.0 to 9.0, preferably within the range of pH 1.0 to 7.0. .

  The reaction temperature in the flow path is desirably within a range where the solvent does not solidify or vaporize, but is preferably -20 to 90 ° C, more preferably 0 to 50 ° C. Especially preferably, it is 5-15 degreeC.

  The speed (flow rate) of the fluid flowing in the flow path is preferably 0.1 mL to 300 L / hr, more preferably 0.2 mL to 30 L / hr, still more preferably 0.5 mL to 15 L / hr, and 1.0 mL to 6 L. / Hr is particularly preferable.

  In producing the stationery ink composition of the present invention, a dispersant can be added in a solution containing an organic pigment or / and in an aqueous solution for changing the hydrogen index (pH). The dispersant (1) has a function of adsorbing rapidly on the surface of the deposited pigment to form fine pigment particles, and (2) preventing these particles from aggregating again. In the present invention, as such a dispersant, an anionic, cationic, amphoteric, nonionic or pigmentary low or high molecular dispersant, or a high molecular dispersant can be used. These dispersants can be used alone or in combination.

  Examples of anionic dispersants (anionic surfactants) include acylmethyl taurate, fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene. Examples thereof include sulfonic acid formalin condensate and polyoxyethylene alkyl sulfate ester salt. Of these, acylmethyl taurate is preferred. These anionic dispersants can be used singly or in combination of two or more.

  Cationic dispersants (cationic surfactants) include quaternary ammonium salts, alkoxylated polyamines, aliphatic amine polyglycol ethers, aliphatic amines, diamines and polyamines derived from aliphatic amines and fatty alcohols, fatty acids And imidazolines derived from these and salts of these cationic substances. These cationic dispersants can be used singly or in combination of two or more.

  The amphoteric dispersant is a dispersant having both an anion group part in the molecule of the anionic dispersant and a cationic group part in the molecule of the cationic dispersant.

  Nonionic dispersants (nonionic surfactants) include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, Examples thereof include glycerin fatty acid esters. Of these, polyoxyethylene alkylaryl ether is preferable. These nonionic dispersants can be used singly or in combination of two or more.

  The pigment-based low molecular or high molecular dispersant is a pigment-based dispersant that is derived from an organic pigment as a parent substance and is produced by chemically modifying the parent structure. For example, sugar-containing pigment dispersants, piperidyl-containing pigment dispersants, naphthalene or perylene-derived pigment dispersants, pigment dispersants having functional groups linked to the pigment parent structure through methylene groups, and polymer-modified pigment parents. A dispersant having a structure, a pigment dispersant having a sulfonic acid group, a pigment dispersant having a sulfonamide group, a pigment dispersant having an ether group, or a pigment dispersant having a carboxylic acid group, a carboxylic ester group, or a carboxamide group There is.

  Further, as the polymer dispersant, specifically, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyacrylamide, vinyl alcohol-vinyl acetate copolymer, polyvinyl alcohol-part Formalized product, polyvinyl alcohol-partially butyralized product, vinylpyrrolidone-vinyl acetate copolymer, polyethylene oxide / propylene oxide block copolymer, polyacrylate, polyvinyl sulfate, poly (4-vinylpyridine) salt, polyamide, poly Allylamine salt, condensed naphthalene sulfonate, styrene-acrylate copolymer, styrene-methacrylate copolymer, acrylate-acrylate copolymer, acrylic Acid ester-methacrylate copolymer, methacrylate ester-acrylate copolymer, methacrylate ester-methacrylate copolymer, styrene-itaconate copolymer, itaconate-itaconate copolymer , Vinyl naphthalene-acrylate copolymer, vinyl naphthalene-methacrylate copolymer, vinyl naphthalene-itaconate copolymer, acid value 60 to 200, and the side where the carboxylic acid group is a terminal group Examples thereof include acrylic polymers having a chain, cellulose derivatives, starch derivatives and the like. In addition, natural polymers such as alginate, gelatin, albumin, casein, gum arabic, tragacanth gum, and lignin sulfonate can also be used. Of these, polyvinylpyrrolidone is preferable. These polymers can be used alone or in combination of two or more.

  In the present invention, a block copolymer can be used as the polymer dispersant. This block copolymer will be described in more detail. Specific examples of the block copolymer include the following. That is, acrylic, methacrylic block copolymers, polystyrene and other addition polymerization or condensation polymerization block copolymers, block copolymers having polyoxyethylene and polyoxyalkylene blocks, and the like. A conventionally known block copolymer can also be used. In the present invention, the block copolymer is more preferably a block form such as AB, ABA, ABD or the like. A, B, and D indicate different block segments. The block copolymer used in the present invention is preferably amphiphilic. As a particularly preferred form, there can be mentioned an AB diblock copolymer comprising a hydrophilic segment having a hydrophobic segment and an organic acid or an ionic salt unit thereof. Further, an ABC triblock copolymer having a hydrophobic segment and a hydrophilic segment having an organic acid or an ionic salt unit thereof and another segment is preferably used. In the case of an ABC triblock, a form in which A is a hydrophobic segment, B is a nonionic hydrophilic segment, and C is a hydrophilic segment having an organic acid or an ionic salt unit thereof is preferably used. preferable.

  The molecular weight distribution = Mw (weight average molecular weight) / Mn (number average molecular weight) of the block copolymer that can be used in the present invention is preferably 2.0 or less. More preferably, it is 1.6 or less, More preferably, it is 1.3 or less. More preferably, it is 1.2 or less. The number average molecular weight Mn of the block polymer used in the present invention is preferably 1000 to 300,000. When the number average molecular weight Mn of the block polymer used in the present invention is 1000 to 300,000, a substance having a predetermined function can be well dispersed in a solvent.

  Further, in order to improve dispersion stability and inclusion, it is preferable that the molecular mobility of the block copolymer is more flexible because it has a point of being easily entangled and affinityd with the surface of the color material. . Further, as described later in detail, it is preferable that the coating layer is flexible in that a coating layer can be easily formed on the recording medium. In particular, when used as an ink, it is preferable that it is flexible in that a coating layer of a block copolymer can be easily formed on a recording medium. This block copolymer coating layer can suppress the oxidation and light degradation of the encapsulated color material and improve the environmental resistance. For this purpose, the glass transition temperature Tg of the main chain of the block polymer is preferably 20 ° C. or lower, more preferably 0 ° C. or lower, and further preferably −20 ° C. or lower. Also in this respect, a polymer having a polyvinyl ether structure is preferably used because it has a low glass transition point and flexible properties.

  In order to further improve the uniform dispersibility and storage stability of the pigment, the blending amount of the dispersant is preferably in the range of 0.1 to 250 parts by mass, more preferably 1 to 100 parts by mass of the pigment. It is the range of -100 mass parts.

  A preferred embodiment of the method for preparing an ink composition for stationery of the present invention is to contain at least one anionic surfactant as a dispersant. The anionic surfactant to be used is preferably an anionic surfactant having a solubility of 2% by mass or more in an organic solvent used for dissolving the pigment, and more preferably an anionic surfactant having a solubility of 5% by mass or more. preferable. Particularly preferred is an anionic surfactant having a solubility of 5% by mass or more in dimethyl sulfoxide (DMSO) which is an aprotic polar solvent. The reason is that it is preferable that the anionic surfactant is contained in an organic solvent in which the pigment is dissolved when the aqueous pigment dispersion is prepared by the pH conversion coprecipitation method. Compared to containing in water used for pH conversion, the particle size of the fine particles is smaller, the particle distribution is narrower, and a stable aqueous dispersion that is less likely to aggregate even when the concentration is increased is obtained.

  The stationery ink composition of the present invention is preferably heat-treated. A preferable heating temperature is 30 ° C to 99 ° C, and more preferably 50 ° C to 90 ° C. Heating may be performed by a batch reaction apparatus or by a flow in a microchannel. The viscosity of the dispersion can be lowered by heat treatment, and the storage stability can be improved. The heat treatment performed for such a purpose is sometimes referred to as “dispersion stabilization treatment heating” in distinction from “polymerization treatment heating” of the polymerizable compound described later.

The stabilization treatment heating in the present invention will be described in detail below.
In the stabilization treatment heating, the heating temperature varies depending on the type and amount of the polymer compound and the organic pigment, but is preferably 40 ° C to 100 ° C, more preferably 50 to 100 ° C, and particularly preferably 60 to 95 ° C. preferable. The organic pigment fine particle dispersion before the heat treatment is preferably at most 60 ° C, more preferably from 0 to 40 ° C, particularly preferably from 10 to 40 ° C. The temperature before the heat treatment can be determined by the temperature of the organic pigment fine particle precipitation step in the microreactor apparatus in the build-up method, and therefore the temperature in the apparatus can be lower than the temperature of the heat treatment. Specifically, it is preferable to set it as 0-40 degreeC, and it is preferable to set it as 10-40 degreeC. By this stabilization treatment heating, the change in the particle size of the build-up pigment fine particles over time can be suppressed. The factors for obtaining such an action are considered as follows. That is, it is conceivable that stabilization treatment heating causes the presence of pigment fine particles or a compound coexisting with them in a dispersion of fine particles having a specific volume average particle diameter to reach a thermodynamically stable state. Especially when synthesized by the build-up method or when microparticles are used to instantly form fine pigment particles, there is no process of applying mechanical energy for a long time like the pulverization method. The state may not have been reached, and it is presumed that this causes an increase in viscosity or a change in particle size. Even in such a case, it is considered that a thermodynamically stable state can be achieved by performing the stabilization heating in the dispersion liquid of fine particles having a specific volume average particle diameter.

  When the stabilization heating is performed in the flow path, the diameter of the flow path is not particularly limited, but the equivalent diameter is preferably 0.1 mm or more and 16 mm or less. By reducing the diameter of the flow path and reducing the thickness of the wall of the flow path, heat exchange can be accelerated and the internal temperature can be quickly raised to substantially the same temperature as the external temperature. As a result, the entire liquid can be heated to a uniform temperature. However, since the amount of liquid that can be heated per unit time may be reduced or the heating time may be too short, it is preferable to select a flow path having an appropriate diameter according to the purpose. It is possible to connect a thick channel for ensuring sufficient heating time after a narrow channel for performing heat exchange quickly, which is one of the preferable methods.

  There are no particular limitations on the flow velocity and flow path length of the portion where the stabilization treatment heating is performed, and it can be appropriately adjusted to preferred values. However, as a combination of the diameter of the heated portion, the flow velocity, and the channel length, it is preferable that the heating time of the liquid is 10 seconds or more. If the heating time is too short, the desired effect may not be obtained. Although there is no particular upper limit on the heating time, it is preferably 5 hours or less from the viewpoint of particle size maintenance and cost. The heating time is more preferably 15 seconds or more and 3 hours or less, still more preferably 20 seconds or more and 2.5 hours or less, and most preferably 60 seconds or more and 2.5 hours or less.

  Depending on the pigment type, the crystal form of the pigment particles may change upon heating for the stabilization treatment. In the present invention, such a change can be used to obtain a dispersion exhibiting desired characteristics.

  In the stabilization treatment heating, it is preferable to contain a polymer compound in the organic pigment dispersion. The polymer compound is preferably a compound having a molecular weight of 1000 or more and a repeating structure. The repeating structure represents a structure in which a specific partial structure is repeatedly included. For example, when a polymerization reaction is performed using a polymerizable compound as a raw material, a polymer in which a partial structure derived from the raw material is repeatedly contained is obtained. Moreover, it is preferable to use what has a function of a pigment dispersant as said high molecular compound. Further, the polymer compound is preferably water-soluble. Here, being water-soluble means that the solubility in water is 0.1% or more, preferably 0.2% or more, and more preferably 1 to 20%.

  Specifically, as this polymer compound, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyacrylamide, vinyl alcohol-vinyl acetate copolymer, polyvinyl alcohol-partial formalized product, polyvinyl Alcohol-partial butyral, vinylpyrrolidone-vinyl acetate copolymer, polyethylene oxide / propylene oxide block copolymer, polyacrylate, polyvinyl sulfate, poly (4-vinylpyridine) salt, polyamide, polyallylamine salt, condensation Naphthalene sulfonate, styrene-acrylate copolymer, styrene-methacrylate copolymer, acrylate ester-acrylate copolymer, acrylate ester -Methacrylate copolymer, methacrylate ester-acrylate copolymer, methacrylate ester-methacrylate copolymer, styrene-itaconate copolymer, itaconate-itaconate copolymer, Examples thereof include a vinyl naphthalene-acrylate copolymer, a vinyl naphthalene-methacrylate copolymer, a vinyl naphthalene-itaconate copolymer, a cellulose derivative, and a starch derivative. In addition, natural polymers such as alginate, gelatin, albumin, casein, gum arabic, tonganto gum and lignin sulfonate can also be used.

  Among them, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, styrene-acrylate copolymer, styrene-methacrylate copolymer, acrylate ester-acrylate copolymer, acrylate ester -A methacrylate copolymer, a methacrylic acid ester-acrylic acid salt copolymer, and a methacrylic acid ester-methacrylic acid salt copolymer are preferable, and polyvinylpyrrolidone is more preferable. These polymer dispersants can be used singly or in combination of two or more.

  As for the said high molecular compound used for this invention, 1000 or more are preferable, as for a mass mean molecular weight, 2000-500000 are more preferable, 5000-100000 are especially preferable. In the present invention, the molecular weight means a mass average molecular weight unless otherwise specified, and means a mass average molecular weight in terms of polystyrene measured by a gel permeation chromatography method (Cartain tetrahydrofuran). In the ink composition for stationery of the present invention, the dispersion stability of the organic pigment fine particle dispersion can be further enhanced by performing stabilization treatment heating in the presence of the polymer compound. Although this function includes uncertain points, the polymer compound is fixed and bonded to the surface of the organic pigment fine particles by heating through the thermodynamic stabilizing action as described above, so that the dispersion stability in the medium is improved. It is possible to increase.

  The organic pigment dispersion of the present invention is preferably an aqueous dispersion in which organic pigment fine particles are dispersed in an aqueous medium when the stabilization treatment heating is performed during circulation in the flow path. Here, the aqueous dispersion may contain a water-soluble organic solvent, preferably a dispersion containing at least 50% by volume of water, and more preferably 70% by volume or more of water. When heated as an organic solvent dispersion, particle size may increase.

  In the present invention, the build-up pigment fine particles may have a polymer of a polymerizable compound immobilized on the pigment fine particles. Immobilization refers to a state in which all (or part of) the polymerizable compound contained is in contact with the pigment fine particles by homopolymerization (or in a copolymerized state). At this time, the polymer may be present either on the surface of the pigment fine particles or inside the pigment fine particles, as long as all (or part of) the polymer is in contact with the pigment fine particles. Adhesion is preferably performed so as not to be detached even by movement in the dispersion. Here, the polymer means a compound produced as a result of polymerization of two or more molecules of the polymerizable compound, and it is not necessary that all the polymerizable compounds on the fine particles are involved in the polymerization reaction. It may remain.

  As the polymerizable compound, any of water-soluble and water-insoluble polymerizable compounds can be used, and there is no particular limitation as long as it is dispersible together with the pigment, but an ethylenically unsaturated monomer is preferable. Specifically, for example, (meth) acrylic acid esters (for example, methyl acrylate, ethyl acrylate, butyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, cyclohexyl acrylate, methyl methacrylate, Ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, propyl γ-hydroxyacrylate, δ-hydroxy Butyl acrylate, β-hydroxyethyl methacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylene glycol methyl methacrylate, ethylene glycol dimethacrylate, Tetraethylene glycol dimethyl methacrylate and the like and derivatives thereof), vinyl aromatic monomers (for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, p-butylstyrene, p-t-butylstyrene, p-hexylstyrene, p-octylstyrene, p-nonylstyrene, p-decylstyrene, p-dodecylstyrene, 2,4 -Dimethylstyrene, 3,4-dichlorostyrene, α-methylstyrene, divinylbenzene, divinylnaphthalene, etc., and derivatives thereof), vinyl esters (vinyl acetate, vinyl propionate, vinyl benzoate, etc., and derivatives thereof), N-vinylamides (eg N-vinylpyrrolide) ), (Meth) acrylic amides, alkyl-substituted (meth) acrylamides, methacrylamides, N-substituted maleimides, vinyl ethers (vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether, divinyl ether, etc. , And derivatives thereof), olefins (ethylene, propylene, isobutylene, 1-butene, 1-pentene, 4-methyl-1-pentene, butadiene, isoprene, chloroprene, etc., and derivatives thereof) diallyl phthalate, maleic anhydride, (Meth) acrylonitrile, methyl vinyl ketone, vinylidene chloride, etc. can be used.

  Furthermore, a water-soluble monomer having an anionic group such as a sulfonic acid group, a phosphoric acid group, and a carboxylic acid group is also used. For example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, p-vinylbenzoic acid Examples thereof include monomers having a carboxyl group such as acids, or alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts thereof, and the like. Specific examples are styrene sulfonic acid, sodium styrene sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, 2-hydroxymethyl methacryloyl phosphate, 2-hydroxyethyl methacryloyl phosphate, and 3-chloro-2-hydroxypropyl methacryloyl phosphate. As mentioned. These may be used alone or in combination with each other.

  The polymerizable compound is preferably a polymerizable surfactant, a reactive surfactant or a reactive emulsifier in which the molecule has a hydrophilic / hydrophobic function separated. For example, α, β-ethylenically unsaturated groups such as vinyl groups, allyl groups, propenyl groups, (meth) acryloyl groups, and ion-dissociable groups such as sulfonic acid groups or salts thereof, and hydrophilic groups such as alkyleneoxy groups And those having a group. These are generally used for emulsion polymerization and are anionic or nonionic surfactants having at least one unsaturated bond capable of radical polymerization in the molecule.

  The above-mentioned polymerizable surfactants may be used alone, in combination with different ones, or with a polymerizable compound other than the polymerizable surfactant. Preferable polymerizable surfactants include, for example, Kao Corporation, Sanyo Chemical Co., Ltd., Daiichi Kogyo Seiyaku Co., Ltd., Asahi Denka Kogyo Co., Ltd., Nippon Emulsifier Co., Ltd., Nippon Oil & Fats. Examples are commercially available from Co., Ltd., etc., described in “Cutting-edge Technology of Fine Particles / Powder, Chapter 1, Fine Particle Design Using Reactive Emulsifiers, pp23-31”, 2000 CMC Co., Ltd. And the like.

  In the present invention, when the build-up pigment fine particles obtained by polymerizing the polymerizable compound are prepared in a dispersion, the polymerization method of the polymerizable compound is not particularly limited as long as it can be polymerized in the pigment dispersion. A method in which a radical is generated using an agent to polymerize is preferable. Although there are various triggers for initiating polymerization, it is preferable to use heat, light, ultrasonic waves, microwaves, or the like. As the polymerization initiator, water-soluble or oil-soluble persulfates, peroxides, azo compounds, and the like can be used. Specifically, ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, 2,2′-azobisisobutyro and tolyl, 2,2′-azobis (2-amidino (Propane) dihydrochloride, 2,2′-azobis (2-N-benzylamidinopropane) dihydrochloride, 2,2′-azobis [2-N- (2-hydroxyethyl) amidinopropane] dihydrochloride, etc. For example, the homepage (www.wako-chem.co.jp) of Wako Pure Chemical Industries, Ltd. has various water-soluble azo polymerization initiators, oil-soluble azo polymerization initiators, and polymer azo polymerizations. Initiators are described and available with a 10 hour half-life temperature and its structural formula. Although the addition amount of a polymerization initiator is not specifically limited, It is preferable to set it as 0.1-30 mass% with respect to all the monomer components, It is more preferable to set it as 1-20 mass%, and 2-10 mass% It is particularly preferable to do this.

  In the present invention, when the build-up pigment fine particles obtained by polymerizing the polymerizable compound are prepared in a dispersion, the dispersion may be copolymerized with a monomer that is copolymerized with the polymerizable compound. The timing for containing the copolymerization monomer is not particularly limited, but it is preferable to contain at least one copolymerization monomer in at least one of the pigment solution and the poor solvent. The copolymerization monomer is not particularly limited as long as it does not hinder the precipitation of fine particles and the stabilization of the dispersion, and examples thereof include the polymerizable compounds mentioned above.

  Various inorganic or organic functional additives may coexist in the dispersion liquid of the build-up pigment fine particles, regardless of whether or not they are copolymerized. Although the time which contains a functional additive is not specifically limited, For example, the case where it adds to at least one of a pigment solution and a poor solvent is mentioned preferably. The functional additive is not particularly limited as long as it does not hinder the precipitation of fine particles and the stabilization of the dispersion. For example, a metal sequestering agent, a bactericidal agent, a fungicide, a fragrance, an ultraviolet absorber, an antioxidant, and a surface tension modifier. , Water-soluble resins, pH adjusters, urea and the like.

  In the build-up pigment fine particles in which the polymerizable compound is fixed, it is preferable that the pigment is precipitated as fine particles in the presence of the polymerizable compound and the polymerizable compound in the dispersion is polymerized as it is. Thereby, extremely high dispersion stability can be realized in the pigment dispersion. This action is considered as follows. Since the polymerizable compound is present in the process of depositing the pigment in the dissolved state to form fine particles, the polymerizable compound is adsorbed integrally with the precipitated fine particles, and the fine particles are efficiently surrounded by the polymerizable compound without gaps. For this reason, the adsorption state of the polymerizable compound, which cannot be obtained simply by mixing the pigment fine particles and the polymerizable compound, can be obtained. By subjecting this to a polymerization reaction as it is, the polymerizable compound can be surely polymerized so as to densely wrap the entire surface of the pigment fine particles, and preferably, it can be firmly and uniformly fixed and not detached. In particular, when the polymerizable compound is a polymerizable surfactant, the stabilizing effect is further enhanced because it is more strongly adsorbed on the surface of the fine particles and surrounds the fine particles. Thus, by using a polymerizable compound, both the size control function at the time of build-up and the subsequent encapsulation function can be exhibited. Thereby, high dispersion stability and storage stability can be imparted to nanosized pigment fine particles having a uniform particle diameter.

In the formation of the build-up pigment fine particles obtained by polymerizing and fixing the polymerizable compound, an embodiment in which fine particles are precipitated by a coprecipitation method and the polymerizable compound is polymerized is described. The timing and method for polymerizing the polymerizable compound are not particularly limited. For example, the following two processes are shown as examples. Even if the polymerization reaction is performed during or after the process (1), the process It may be performed during or after (2) or both.
(1) A process of mixing a pigment solution and a poor solvent.
(2) A process of concentrating and purifying the dispersion after mixing.

Similarly, the timing and method of addition of the polymerization initiator are not particularly limited. For example, the following four embodiments may be used, or any of them may be used in combination.
(1) Add to the pigment solution.
(2) Add to poor solvent.
(3) The pigment solution and the poor solvent are mixed and then added.
(4) The dispersion after mixing is added after concentration and purification.

  When the build-up pigment fine particles are precipitated by the coprecipitation method, the polymerizable compound is preferably contained in at least one of the pigment solution and the poor solvent, and is preferably contained in the pigment solution. When other polymerizable compounds and dispersants are used in combination, the mode is not particularly limited. For example, they may be dissolved in either the pigment solution or the poor solvent, or may be added to the dispersion after mixing. . Further, when the fine particles are precipitated, a liquid other than the pigment solution or the aqueous medium may be mixed as necessary, and three or more liquids may be mixed simultaneously or sequentially.

  The polymerization reaction temperature when the polymerizable compound is heated by polymerization treatment can be selected according to the type of the polymerization initiator, and is preferably 40 ° C to 100 ° C, more preferably 50 ° C to 90 ° C, and particularly preferably 50 ° C to 80 ° C. It can be carried out at ° C. The polymerization reaction time can be 1 to 12 hours, although it depends on the polymerizable compound used, its concentration, and the reaction temperature of the polymerization initiator.

Additives such as UV absorbers, antioxidants, fragrances, fungicides, surface tension modifiers, water-soluble resins, bactericides, pH adjusters, urea, etc. for the purpose of increasing the fastness of fine particles of build-up pigments May be. The timing and method of addition of these are not particularly limited. For example, the following four aspects may be used, and any of these may be performed in combination.
(1) Add to the pigment solution.
(2) Add to poor solvent.
(3) The pigment solution and the poor solvent are mixed and then added.
(4) The dispersion after mixing is added after concentration and purification.
In order to adjust the degree of polymerization (molecular weight), various chain transfer agents (for example, catechols, alcohols, thiols, mercaptans) may be used.
In order to further improve the uniform dispersibility and storage stability of the pigment, the content of the polymerizable compound is preferably in the range of 0.1 to 1000 parts by mass, more preferably 100 parts by mass of the pigment. It is the range of 1-500 mass parts, Most preferably, it is the range of 10-250 mass parts. If the amount is too small, the dispersion stability of the pigment fine particles may not be improved.

Next, the average particle size of the build-up pigment fine particles used in the ink composition for stationery of the present invention (in the present invention, the average particle size refers to the average diameter of the particles, and may be referred to as the average particle diameter or the average particle diameter). ) And particle size distribution.
There is a method for expressing the average size of a population by digitizing the particle size measurement method of fine particles, but it is often used that corresponds to the mode diameter indicating the maximum value of the distribution and the median value of the integral distribution curve. Median diameter and various average diameters (length average, area average, mass average, number average (MN), volume average (MV), etc.). The average particle size of the build-up pigment fine particles used in the ink composition for stationery of the present invention is preferably 80 nm or less in volume average (MV), more preferably 3 to 70 nm, and particularly preferably 10 to 50 nm.

When the particle size of the fine particles is the same (that is, the monodispersed fine particle system), it means that the size of the contained particles is the same, but the particle properties are not only that, but also the chemical composition and crystal structure within the particle This also suggests that there is no variation between particles, which can be an important factor in determining particle performance. In particular, ultrafine particles having a particle size of nanometers may have a great influence as a factor governing the properties of the particles.
In the ink composition for stationery of the present invention, the build-up pigment fine particles are preferably not only fine particles having a small particle size of nanometer size, but also fine particles having a uniform size in which the size is controlled. It is important for the writing quality of stationery ink that the pigment particles are uniform in size, that is, have a narrow particle size distribution (high monodispersity). As an index indicating that the sizes are uniform, a value (MV / MN) obtained by dividing the volume average particle diameter MV by the number average particle diameter MN can be expressed as an index of monodispersity.
In the present invention, unless otherwise specified, the monodispersity of the fine particles is indicated by the above MV / MN value. The smaller this value is and the closer it is to 1, the better the monodispersity.
The MV / MN of the pigment particles contained in the ink composition for stationery of the present invention is 1.80 or less, preferably 1.60 or less, and more preferably 1.40 or less. The volume average particle diameter MV and the number average particle diameter MN are values measured by a dynamic light scattering method or the like unless otherwise specified.

  The content of the build-up pigment fine particles in the ink composition for stationery of the present invention is not particularly limited, but is preferably 50% by mass or less, and preferably 1 to 30% by mass with respect to the total amount of the ink composition. More preferred.

  The ink composition for stationery of the present invention is used for a stationery, that is, a writing instrument for stationery. For example, it is preferably used as a pen or marker ink as a stationery, and particularly preferably used as an aqueous gel ink or aqueous marking pen ink described later. However, other stationery, for example, fountain pens, milli-point pens, ballpoint pens, fluorescent pens, sign pens, magic pens, glass pens, brush pens, markers, marking pens and the like may be used as ink.

  The aqueous gel ink of the present invention comprises the above-mentioned ink composition for stationery and contains at least the above-mentioned fine particles of the build-up pigment, but water (purified water, distilled water, pure water, ultrapure water, ion-exchanged water, etc.), colorant , A shear thinning agent, and an ink composition containing a water-soluble liquid medium, and more preferably a humectant.

  The build-up pigment fine particles are used as a colorant component, but may contain other colorants such as dyes as long as they are dissolved or dispersed in water. As the colorant, the build-up pigment fine particles can be used alone or in admixture of two or more. The amount of use can be appropriately determined depending on the desired drawn line density of the ink. The colorant containing the build-up pigment fine particles is usually preferably 0.1 to 40% by mass, more preferably 2 to 30% by mass, and more preferably 3 to 20% by mass with respect to the total amount of the ink. It is particularly preferred.

  The shear thinning agent is for adjusting the viscosity of the aqueous gel ink, and a substance soluble or dispersible in water is effective. Specific examples include natural polymer substances, cellulose compounds, synthetic polymer compounds, and inorganic substances. Natural polymer substances include xanthan gum composed of monosaccharides and polysaccharides such as glucose, mannose, galactose, rhamnose, and glucuronate, succinoglycan, an organic acid-modified heteropolysaccharide of glucose and galactose, welan gum, Tamarind gum, carrageenan gum, tragacanth gum, locust bean gum, gum arabic, guar gum, tara gum, guard run, pectin, agar, gelatin, mannan, alginic acid alkyl ester compounds, benzylidene sorbitol and benzylidene xylitol, fatty acid amide or derivatives thereof, hardened castor oil Etc. Examples of the cellulose compound include methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose.

  Synthetic polymer compounds include acrylic synthetic polymers, urethane synthetic polymers, polyvinylpyrrolidone, styrene / maleic acid copolymer alkali salts, vinyl acetate / crotonic acid copolymer alkali salts, and modified polyvinyl alcohol. And vinyl alcohol, methyl vinyl ether / maleic acid copolymer, polyalkylene oxide such as polyethylene oxide, and derivatives thereof.

  Examples of the acrylic synthetic polymer include polyacrylic acid, alkali salt of polymethacrylic acid, alkali salt of acrylic acid or methacrylic acid-containing copolymer, alkyl methacrylate ester, cross-linked acrylic polymer such as cross-linked polyacrylic acid And associative acrylic polymers such as associative polyacrylic acid.

  Examples of inorganic substances include inorganic natural or semi-synthetic compounds such as smectite, montmorillonite, bentonite, and silica.

  Among these, natural polymer substances such as xanthan gum, acrylic synthetic polymer compounds, and polyvinylpyrrolidone are preferable.

  The shear thinning agents can be used alone or in admixture of two or more. The shear thinning agent is preferably contained in the ink in an amount of 0.05 to 20% by mass, more preferably 0.1 to 10% by mass, and particularly preferably 0.1 to 5% by mass. preferable.

  The water-soluble liquid medium means water and a polar solvent other than water. Examples of polar solvents other than water include water-soluble organic solvents. Specific examples include polyhydric alcohol compounds, polyalkylene glycol compounds, glycerol compounds, and lower alkyl ethers of glycols.

  Examples of the polyhydric alcohol compound include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-prompadiol, 1,2-butanediol, 2 , 3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol Examples include 2-methylpentane-2,4-diol, 3-methylpentane-1,3,5 triol, 1,2,3-hexanetriol, and glycerin.

  Examples of the polyalkylene glycol compound include polyethylene glycol and polypropylene glycol.

  Examples of the glycerol compound include glycerol, diglycerol, triglycerol and the like. Examples of the lower alkyl ether of glycol include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether and the like. In addition, diglycerin ethylene oxide adduct, ethylene glycol monoethyl ether acetate, thiodiethanol, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like can also be used. In these, polyhydric alcohol compounds, such as ethylene glycol, propylene glycol, diethylene glycol, and glycerol, and a diglycerol ethylene oxide adduct are preferable.

  These water-soluble liquid media can be used alone or in admixture of two or more. The content of the water-soluble organic solvent is preferably 1 to 40% by mass, more preferably 5 to 35% by mass, and particularly preferably 8 to 30% by mass with respect to the total amount of the ink. .

  The aqueous gel ink of the present invention preferably contains a humectant other than a water-soluble liquid in order to improve phenomena such as vibration blur, dry-up, and bleeding. As humectants, from the viewpoints of environmental compatibility, water solubility, and moisture retention, maltitol, reducing sugars based on maltitol, sorbitol, reducing sugars based on sorbitol, reducing oligosaccharides, reducing One or more selected from malto-oligosaccharides, reduced starch degradation products, reduced dextrin, reduced maltodextrin, α-cyclodextrin, β-cyclodextrin and maltosyl cyclodextrin are preferred. These have a function of improving writing quality and drying resistance without changing ink viscosity and pH with time. Further, since it does not affect anionic or cationic substances, there is an advantage that it can be arbitrarily selected as a colorant from various pigments.

  The content of the humectant is preferably 20% by mass or less, more preferably 0.5 to 20% by mass, still more preferably 1 to 15% by mass, based on the total amount of the ink. It is especially preferable to set it as 10 mass%. When this content is too large, the spinnability becomes strong and the writing quality may be lowered.

  The water-based gel ink of the present invention can further contain an alkylene oxide adduct. Examples of the alkylene oxide adduct include an alkylene oxide adduct of polyglycerin, an alkylene oxide adduct of glycerin, and an alkylene oxide adduct of trimethylolpropane. These may be used alone or in admixture of two or more. be able to.

  The alkylene oxide adduct of polyglycerin is obtained by adding 1 mol or plural moles of alkylene oxide to polyglycerin having a polymerization degree of 2 to 4, and the alkylene oxide adduct of trimethylolpropane is added to trimethylolpropane. An alkylene oxide adduct is added by 1 mol or plural mols. These improve the anti-bleeding property, lubricity, and stability of ink outflow, and by combining with the above moisturizers, they prevent syneresis and increase the stability over time. Arise.

  The content of these alkylene oxide adducts is preferably 40% by mass or less, more preferably 2 to 30% by mass, and particularly preferably 5 to 20% by mass with respect to the total amount of the ink. . If the content is too small, the effect of improving the writing quality may not be sufficient, and if it is too large, the drying property may decrease.

  The water-based gel ink of the present invention can contain various additives (for example, a dispersant, a surfactant, an antiseptic, a rust inhibitor, a pH adjuster, etc.) as necessary.

  Examples of the dispersant include water-soluble polymers such as ammonium salt of styrene maleic acid resin and ammonium salt of styrene acrylic acid resin. The content of the dispersant is preferably 10% by mass or less, more preferably 0.5 to 5% by mass with respect to the total amount of the ink.

  Surfactants can be added to adjust the surface tension of the ink and improve writing quality. For example, fluorinated alkyl groups such as nonionic surfactants, anionic surfactants, and perfluoroalkyl phosphate esters can be used. And a surfactant having fluorine.

  Nonionic surfactants include polyglycerin fatty acid ester compounds, ethylene oxide adducts of glycerin fatty acid esters, polyoxyethylene sorbit fatty acid ester compounds, polyoxyethylene sorbitan fatty acid ester compounds, polyoxyethylene fatty acid ester compounds, polyoxyethylene alkyls. Examples include ether compounds, polyoxyethylene alkylphenyl ether compounds, polyoxyethylene polyoxypropylene alkyl ether compounds, fatty acid monoethanolamide compounds, polyoxyethylene fatty acid amide compounds, polyoxyethylene alkylamine compounds, and sugar ester compounds.

  Examples of the anionic surfactant include phosphate compounds such as alkyl phosphate esters, naphthalene sulfonic acid formalin condensates, dialkyl sulfosuccinic acid esters or sodium salts thereof.

  The content of the surfactant is preferably 5% by mass or less, more preferably 0.05 to 2% by mass with respect to the total amount of the ink.

  Examples of preservatives include potassium sorbate, sodium benzoate, sodium pentachlorophenyl, sodium dehydroacetate, sodium omadin, 1,2-benzisothiazoline. The content of the preservative is preferably 5% by mass or less, more preferably 0.01 to 2% by mass with respect to the total amount of the ink.

  The rust inhibitor is used to prevent corrosion of metal materials such as ink holders and balls, and examples thereof include benzotriazole, tolyltriazole, dicyclohexylammonium nitrate, and saponins. The content of the rust inhibitor is preferably 5% by mass or less, and more preferably 0.01 to 2% by mass with respect to the total amount of the ink.

  Examples of the pH adjuster include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium phosphate, aminomethyl propanol, triethanolamine and the like. The pH of the water-based gel ink is usually adjusted to 7 to 8, but the content of the pH adjuster used at that time is preferably 5% by mass or less, and 0.01 to 3% by mass with respect to the total amount of the ink. % Is more preferable.

  Said dispersing agent, surfactant, antiseptic | preservative, rust preventive agent, and pH adjuster can be used individually or in mixture of 2 or more types, respectively.

  The aqueous gel ink of the present invention can be produced by a general method such as mixing, stirring, filtration purification, and the like.

The viscosity of the aqueous gel ink of the present invention is preferably 200 to 600 mPa · s, more preferably 250 to 550 mPa · s, and particularly preferably 300 to 500 mPa · s. If the ink viscosity is too low, a direct current phenomenon or bleeding may easily occur. On the other hand, if it is too high, the ink outflow property is lowered, and it becomes easy to be affected by the dry-up due to the volatilization of the liquid component, which may lead to a reduction in drawing quality such as blurring.
〔viscosity〕
In the present invention, when referred to as “viscosity”, unless otherwise specified, at a temperature of 25 ° C., a cone plate type rotational viscometer (1 ° 34′R24 cone) (manufactured by Tokimec Co., Ltd., RE-100 type viscometer (trade name)) ) Is a value measured under the condition of a rotational speed of 1 rpm.

In the aqueous gel ink of the present invention, the n value of the non-Newtonian viscosity index is preferably 0.40 to 0.80, more preferably 0.45 to 0.70, and more preferably 0.50 to 0.00. Particularly preferred is 65. The non-Newtonian viscosity index refers to n in the viscosity equation represented by the following formula 1.
S = αD ⁿ (where 1>n> 0) Equation 1
Here, S is a shear stress (dyn / cm ² ), D is a shear rate (s ⁻¹ ), and α is a non-Newtonian viscosity coefficient. If the n value is too small, the increase in the viscosity of the ink in a stationary state is large, so that the decrease in fluidity combined with the increase in the viscosity due to the volatilization of the liquid component becomes remarkable, and writing failure due to dry-up tends to occur. In addition, by adjusting the n value and the above viscosity within a predetermined range, vibration blur, dry-up, bleeding, and direct current phenomenon can be more effectively suppressed, and the writing performance and drawing performance of the ballpoint pen can be enhanced. In the present invention, the non-Newtonian viscosity index (n value) means a value measured under the following conditions unless otherwise specified.
[Measurement and calculation of non-Newtonian viscosity index (n value)]
Using a cone plate type rotational viscometer (1 ° 34'R24 cone) (manufactured by Tokimec Co., Ltd., RE-100 viscometer (trade name)) at a temperature of 25 ° C. and a rotational speed of 1 to 100 rpm, a plurality of rotations A number of shear stresses are measured and applied to Equation 1 above to calculate a non-Newtonian viscosity index (n value).

The aqueous gel ink of the present invention is excellent in stability over time. Here, the temporal stability means that excellent writing quality is maintained even after a certain period of time while being stored or used by being incorporated in various writing instruments. If the change in writing taste is indicated by, for example, the viscosity increase of the ink, it is preferably 100 mPa · s or less, and more preferably 50 mPa · s or less. In the present invention, the viscosity increase means a value measured under the following conditions unless otherwise specified.
[Measurement of viscosity increase]
Using a cone plate type rotational viscometer (1 ° 34′R24 cone) (manufactured by Tokimec Co., Ltd., RE-100 type viscometer (trade name)), the measurement is performed under conditions of a temperature of 25 ° C. and a rotational speed of 1 rpm. “Initial viscosity” is a viscosity value measured immediately after ink preparation, and “aging viscosity” is a viscosity value after heating at 50 ° C. for 100 hours. A value obtained by subtracting the value of the “initial viscosity” from the value of the “viscosity viscosity” is defined as a viscosity increase.

  The water-based gel ink of the present invention can be used for ordinary water-based gel ink ballpoint pens, preferably used for ultra-fine pens having a ball outer diameter of 0.25 mm or less, and used for those having a ball outer diameter of 0.06 to 0.2 mm. Is more preferable. Even with such an ultra-fine pen tip, there is no vibration blur, dry-up, and bleeding, and the writing performance and drawing performance of the ballpoint pen are stable over time, and an excellent writing quality can be realized.

In a water-based gel ink ballpoint pen, when a longitudinal impact is applied to the shaft, particularly when the tip is in an upward state, the viscosity of the ink is drastically lowered, and air is trapped in the ink container through the tip. Sometimes. Even if writing is attempted in such a state, drawing of the ink is interrupted or splattered because the outflow of the ink is inhibited until the entrained air is discharged from the tip of the chip. The ink flow path of the ultrafine water-based ballpoint pen is more prominently affected by vibration blur than the conventional ballpoint pen.
In addition, about the structure of a water-based gel ink ball-point pen, a writing characteristic, etc., paragraphs 0010-0016 of Unexamined-Japanese-Patent No. 2006-181905 can be referred.

Next, the water-based marking pen ink using the ink composition for stationery of this invention is demonstrated.
The water-based marking pen ink of the present invention contains the above-mentioned build-up pigment fine particles, but is preferably used as a pigment colorant aqueous dispersion using water as a solvent, and further includes a water-soluble resin, a release agent, and a film formation aid. It is preferable to contain an agent.

  In the water-based marking pen ink of the present invention, when water is used as a solvent, the amount of water in the ink is preferably 60 to 90% by mass, and preferably 70 to 85% by mass with respect to the total amount of ink. More preferred.

  Examples of the pigment used in the aqueous marking pen ink of the present invention include those described above, and those such as indanthrene compounds such as carbon black, azo compounds, phthalocyanine compounds, and selenium blue are preferable. As the dispersant, a resin dispersant is preferable.

  The amount of the pigment in the colorant aqueous dispersion is preferably 20 to 35% by mass. The amount of the dispersant is preferably 6 to 12 parts by mass with respect to 30 parts by mass of the pigment as a solid content ratio. The colorant aqueous dispersion is preferably contained in the range of 1 to 30% by mass and more preferably in the range of 5 to 20% by mass with respect to the total amount of the ink. When the amount of the colorant aqueous dispersion is too large, the viscosity of the ink becomes too high, and the writing property and the erasability may be deteriorated. On the other hand, if the amount is too small, the concentration of the handwriting is thin and not practical.

  Water-soluble resin should be used to improve the film-forming and leveling properties of the writing surface, and to be able to be easily erased when the handwriting is lightly rubbed with a dry cloth or flexible paper. Is preferred. The water-soluble resin includes a polyalkylene oxide compound having a mass average molecular weight of 100 or more obtained by addition polymerization of an alkylene oxide containing ethylene oxide to an organic compound having two active hydrogen groups, a polyvalent carboxylic acid, its anhydride or its lower A hydrophilic high molecular weight compound having a mass average molecular weight of 10,000 or more obtained by reacting with an alkyl ester or diisocyanate is preferred.

Examples of the organic compound having two active hydrogens as the starting material in the polyalkylene compound include ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, 1,6-hexanediol, and aniline. Etc. Furthermore, examples of the alkylene oxide added to the organic compound include ethylene oxide alone or a mixture of ethylene oxide and propylene oxide, putylene oxide, styrene oxide, α-olefin epoxide, glycidyl ethers, and the like. The addition polymerization of alkylene oxide can be carried out by a usual method. Alternatively, the method described in paragraph 0015 of JP-A-6-16991 may be used.
The high molecular weight compound preferably has a mass average molecular weight of 10,000 or more. The content of the water-soluble resin is preferably 0.1 to 15% by mass and more preferably 0.3 to 10% with respect to the total amount of ink.

  As a water-soluble resin, a water-soluble resin which is a hydrophilic high molecular weight compound having a mass average molecular weight of 10,000 or more obtained by reacting a polyalkylene oxide compound and a polyvalent carboxylic acid, its anhydride or its lower alkyl ester or isocyanate is used. In addition, it is preferable to contain a fluorine-based surfactant.

  As an exfoliation accelerator that makes it easy to erase the handwriting written with marking pen ink, together with a component that softens the water-soluble resin in the ink, when the ink becomes handwriting on the writing board and dries, the resin film and the writing board It is preferable to add an incompatible oily substance to the resin that moves between the two.

  As the component for softening the water-soluble resin, various surfactants, polyhydric alcohols, and 2-ethylhexanoic acid hexadecyl aqueous emulsion which is a liquid aliphatic carboxylic acid ester compatible with the water-soluble resin at room temperature are used. It is preferable. The 2-ethylhexanoic acid hexadecyl emulsion is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on the total amount of ink.

  As the incompatible oily substance for the water-soluble resin, an emulsion of a higher hydrocarbon or an emulsion of a higher alcohol may be used. Preferably, the aliphatic carboxylic acid ester and / or the phthalic acid ester are in an aqueous emulsion state. Used in As the aliphatic carboxylic acid ester, a monobasic acid ester is preferably used. Specific examples include methyl oleate, butyl oleate, 2-ethylhexyl palmitate, isopropyl isostearate, isocetyl stearate, isocetyl isostearate, isostearyl palmitate and the like. These are used alone or as a mixture of two or more. Examples of the phthalate ester include dibutyl phthalate and dioctyl phthalate.

  The incompatible aliphatic carboxylic acid ester emulsion or phthalic acid ester emulsion is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on the total amount of the ink. If the total amount is too small, sufficient handwriting erasability cannot be obtained. If the total amount is too large, the handwriting is stretched and the writing surface is soiled, and the handwriting erasability may be lowered.

  The emulsification of the aliphatic carboxylic acid ester or phthalic acid ester preferably has storage stability over time, and preferably does not have separation such as creaming during storage. Usually glycerin is used as a stabilizer. As emulsifiers, fatty acid soaps, sodium alkyl sulfates or sorbitan surfactants are usually used. The emulsification method can be prepared by a method using a normal emulsifier.

In the aqueous marking pen ink of the present invention, it is preferable to use a fluorine-based surfactant as a film forming aid. In the case where no fluorine-based surfactant is added, when writing on a writing board such as a polypropylene board or a melamine baking board, there is a case where ink is not carried well and writing performance is not good. In general, the fluorine-based surfactant is preferably 5% by mass or less, and more preferably in the range of 0.2 to 3% by mass.
In the aqueous marking pen ink of the present invention, a lower aliphatic alcohol may be added to accelerate the drying of the handwriting. As the lower alcohol, ethanol or isopropanol is preferably used, and this is usually preferably 10% by mass or less, more preferably 5% or less, so that the emulsion in the ink is not broken.

The aqueous marking pen ink of the present invention is excellent in stability over time. The stability over time has the same meaning as described above. For example, in terms of the viscosity increase of the ink, it is preferably within ± 10%, and more preferably within ± 5%. In the present invention, the viscosity increase means a value measured under the following conditions unless otherwise specified.
[Measurement of viscosity increase]
Using a cone plate type rotational viscometer (1 ° 34′R24 cone) (manufactured by Tokimec Co., Ltd., RE-100 type viscometer (trade name)), the measurement is performed under conditions of a temperature of 25 ° C. and a rotational speed of 1 rpm. “Initial viscosity” is the viscosity at 25 ° C. measured immediately after ink preparation. “Viscosity with time” is the viscosity at 25 ° C. after heating the ink at 50 ° C. for 50 hours. The value of “viscosity with time” is divided by the value of “initial viscosity”, and the percentage obtained by subtracting 1 from the value is defined as the viscosity increase.

The present invention will be described below in more detail based on examples, but the present invention is not limited to these examples. In the following, “%” and “parts” indicating composition ratios represent “% by mass” and “parts by mass” unless otherwise specified.
The particle size and particle size distribution of the pigment particles were measured using Nanotrac UPA150EX (trade name) manufactured by Nikkiso Co., Ltd.

(Example 1 and Comparative Example 1)
(Preparation of aqueous dispersion sample A-1)
0.59 g of 2,9-dimethylquinacridone (PR122, manufactured by Clariant, HOSTAPERM PINK E (trade name)), 5.0 mL of dimethyl sulfoxide, methanol solution of 28% sodium methoxide (manufactured by Wako Pure Chemical Industries, Ltd.) 0.85 mL and 25% Aqualon KH-10 (trade name) (Daiichi Kogyo Seiyaku Co., Ltd.) were mixed and dissolved in 2.0 mL of DMSO solution at room temperature (IA solution). The pH of the IA solution exceeded the measurement limit (pH 14) and could not be measured. Distilled water was used as the IIA solution. Impurities such as dust were removed by passing these through a 0.45 μm microfilter (manufactured by Sartorius).

  Next, a simple reaction apparatus having a Y-shaped channel configuration like the reaction apparatus of FIG. 2 was prepared and reacted in the following procedure. That is, two Teflon (registered trademark) tubes having a length of 50 cm and an equivalent diameter of 1 mm are connected to two connectors of a Teflon (registered trademark) Y-shaped connector (Tokyo Rika Kikai Co., Ltd.) having an equivalent diameter of 500 μm. Were connected to each other, and syringes containing IA solution and IIA solution were connected to the tip of the tube and set in a pump. A Teflon (registered trademark) tube having a length of 1.5 m and an equivalent diameter of 500 μm was connected to the outlet of the connector. The IA liquid was sent out at a liquid sending speed of 96 mL / h, and the IIA liquid was sent out at a liquid feeding speed of 600 mL / h (Reynolds number: about 500). Since a pigment dispersion of 2,9-dimethylquinacridone was obtained from the tube outlet tip, it was collected. At this time, the pH of the pigment dispersion was 13.06.

Furthermore, 5% amount of potassium persulfate (K ₂ S ₂ O ₈ ) of Aqualon KH-10 contained in this pigment dispersion was added, and polymerization treatment was performed at 70 ° C. for 5 hours. The volume average particle size MV of the pigment fine particles of the obtained dispersion was 19.5 nm, and the ratio of volume average particle size MV / number average particle size MN, which is an index of monodispersibility, was 1.52. Next, the pigment dispersion is purified by adding ultrafiltration equipment (Advantech Toyo Co., Ltd., UHP-25K (trade name), molecular weight cut off: 200,000) while maintaining the liquid volume while adding distilled water, and then concentrated. As a result, an aqueous dispersion (ink composition for stationery) sample A-1 having a pigment concentration of 7.5% by mass was obtained.

(Preparation of aqueous dispersion sample A-2)
A pigment dispersion was prepared in the same manner as in the aqueous dispersion A-1, except that Aqualon KH10 was replaced with an equal mass of styrene (special grade, manufactured by Wako Pure Chemical Industries, Ltd.). Further, 1% by mass of K ₂ S ₂ O ₈ of styrene contained in this pigment dispersion was added, followed by polymerization treatment heating at 70 ° C. for 5 hours. When the particle diameter of the obtained pigment dispersion was measured, the volume average particle diameter MV of the pigment fine particles was 39.8 nm, and the ratio of volume average particle diameter MV / number average particle diameter MN, which is an index of monodispersibility, was 1.80.
Next, this pigment dispersion is purified by adding ultrafiltration equipment (Advantech Toyo Co., Ltd., UHP-25K, fractional molecular weight 200,000) while maintaining the liquid volume while adding distilled water, followed by concentration. An 8 mass% aqueous dispersion sample A-2 was obtained.

(Preparation of aqueous dispersion sample A-3)
A stirring bar was placed in a 50 mL beaker, and 25.0 mL of the IIA solution was stirred at room temperature. To this, 0.5 mL of IA solution was poured using a syringe to obtain a pigment dispersion of 2,9-dimethylquinacridone (PR122). Next, polymerization treatment, purification, and concentration were performed in the same manner as Sample A-1, to obtain a 7.5 mass% aqueous dispersion sample A-3. At this time, the volume average particle diameter MV of the pigment fine particles was 46.5 nm, and the ratio of volume average particle diameter MV / number average particle diameter MN, which is an index of monodispersibility, was 1.78.

(Preparation of aqueous dispersion sample A-4)
PR254 (Ciba Specialty Chemicals, CROMOPHTALRED 2030 (trade name)) 0.6 g, dimethyl sulfoxide 4.88 mL, 8 mol / L KOH aqueous solution (Wako Pure Chemical Industries, Ltd.) 0.63 mL, 25% Aqualon KH-10 (trade name) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was dissolved in 2.18 mL of a mixed DMSO solution at room temperature (ID solution). The pH of the ID solution exceeded the measurement limit (pH 14) and could not be measured. Distilled water was used as the IID liquid.

  Impurities such as dust were removed by passing these through a 0.45 μm microfilter (manufactured by Sartorius). Next, a simple type reaction apparatus having a Y-shaped channel configuration as shown in FIG. 2 was prepared, and the reaction was performed according to the following procedure. Using two Teflon (registered trademark) tubes with a length of 50 cm and an equivalent diameter of 1 mm at the two inlets of a Teflon (registered trademark) Y-shaped connector (Tokyo Rika Kikai Co., Ltd.) having an equivalent diameter of 500 μm. It connected, the syringe which put ID liquid and IID liquid in the tip was connected, and it set to the pump. A Teflon (registered trademark) tube having a length of 1.5 m and an equivalent diameter of 500 μm was connected to the outlet of the connector. The ID solution was sent out at a delivery rate of 96 mL / h and the IID solution was sent out at a delivery rate of 600 mL / h (Reynolds number of about 500). A pigment dispersion of Pigment Red 254 was obtained from the tip of the tube outlet and was collected. At this time, the pH of the pigment dispersion was 13.12.

A 5% amount of K ₂ S ₂ O ₈ of Aqualon KH-10 was added to this pigment dispersion, and polymerization treatment was performed at 70 ° C. for 5 hours. The volume average particle size MV of the pigment fine particles of the dispersion thus obtained was 39.5 nm, and the ratio of volume average particle size MV / number average particle size MN, which is an index of monodispersibility, was 1.40. It was. Next, this pigment dispersion is purified and concentrated while adding distilled water so as to maintain the amount of liquid with an ultrafiltration device (manufactured by Advantech Toyo Co., Ltd., UHP-25K (trade name), molecular weight cut off 200,000). A 8.2 mass% pigment aqueous dispersion sample A-4 was obtained.

(Preparation of aqueous dispersion sample A-5)
3.0 g of PY128 (manufactured by Ciba Specialty Chemicals, CROMOPHTAL YELLOW 8GNP (trade name)), dimethyl sulfoxide 45.5 mL, 28% sodium methoxide in methanol (Wako Pure Chemical Industries, Ltd.) 2.49 mL Aqualon KH-10 (trade name) (Daiichi Kogyo Seiyaku Co., Ltd.) 2.4 g, N-vinylpyrrolidone (Wako Pure Chemical Industries, Ltd.) 0.6 g, Polyvinylpyrrolidone K30 (trade name) ( It dissolved at room temperature (IE liquid) with 0.15 g of Tokyo Chemical Industry Co., Ltd.) and 1.5 g of VPE0201 (trade name) (manufactured by Wako Pure Chemical Industries, Ltd.). The pH of the IE solution exceeded the measurement limit (pH 14) and could not be measured. Distilled water was used as the IIE solution. Impurities such as dust were removed by passing these through a 0.45 μm microfilter (manufactured by Sartorius). As the microreactor device, a three-dimensional microreactor device having the following number of divisions (number of flow paths) and the like as shown in FIG. 1 was used.
(I) Number of supply flow paths (n): Divided into 5 for each of the two types of reaction liquids (a total of 10 flow paths merge. In addition, the apparatus of FIG. It is a device to do.)
(Ii) Width (W) of supply flow paths 21 and 22: 400 μm each
(Iii) Depth (H) of supply flow paths 21 and 22: 400 μm each
(Iv) Diameter (D) of merging region 20 800 μm
(V) Diameter (R) of microchannel 23 ... 800 μm
(Vi) Intersection angle between the central axes of the supply flow channels 21 and 22 and the micro flow channel 23 in the merge region 20 ... 90 °
(Vii) Material of the device: stainless steel (SUS304)
(Viii) Flow path machining method: This was performed by micro electric discharge machining, and the sealing method of the three parts of the supply block 81, the merging block 12, and the reaction block 13 was performed by metal surface sealing by mirror polishing. Two Teflon (registered trademark) tubes having a length of 50 cm and an equivalent diameter of 1 mm were connected to the two inlets using a connector, and syringes containing IE solution and IIE solution were connected to the ends of the tubes and set in a pump. A Teflon (registered trademark) tube having a length of 1.5 m and an equivalent diameter of 2 mm was connected to the outlet of the connector. The IE solution was delivered at a delivery rate of 150 mL / min, and the IIE solution was delivered at a delivery rate of 600 mL / min. Pigment yellow 128 pigment dispersion was obtained from the tip of the tube outlet. This was collected, heated at 80 ° C. for 5 hours, and then subjected to polymerization treatment, and the particle size was measured. The ratio of volume average particle diameter MV / number average particle diameter MN, which is an index of 25.5 nm and monodispersibility, was 1.48. At this time, the pH of the pigment dispersion was 12.88.
The dispersion was purified and concentrated while adding distilled water to maintain the liquid volume with an ultrafiltration device (manufactured by Advantech Toyo Co., Ltd., UHP-62K (trade name), molecular weight cut off 50,000), and the pigment concentration was 7.1. A mass% pigment aqueous dispersion sample A-5 was obtained.

(Preparation of aqueous dispersion sample A-6)
Reaction liquids A to D were prepared as follows. Each solution was a uniform solution, and after preparation, filtered through a 500 μm PTFE (polytetrafluoroethylene) microfilter was used. The abbreviations represent the following compounds. PC-2Na; disodium phthalocyanine, DMSO; dimethyl sulfoxide, PVP; polyvinylpyrrolidone.
Solution A: PC-2Na, 2.5 g (4.5 mmol) was stirred at room temperature and dissolved in DMSO to make 500 ml. Blue-green solution.
Liquid B: PVP (mass average molecular weight 360,000), 5.0 g, was dissolved in DMSO by stirring at 100 ° C. to make 500 ml. A clear colorless solution.
Solution C: N-oleoyl-N-methyltaurine sodium salt, 5.0 g (11.7 mmol) was stirred at room temperature for 1 hour and dissolved in DMSO to make 500 ml. A clear colorless solution.
Liquid D: CuBr ₂ , 10.1 g (45.0 mmol) was stirred at room temperature and dissolved in DMSO to make 500 ml. Yellow solution.
200 ml of solution B and 100 ml of solution D were placed in a flask and mixed and stirred at room temperature under a nitrogen stream. A mixed solution of 100 ml of liquid A and 100 ml of liquid C was added dropwise over 1 hour using a syringe pump. The resulting precipitate was filtered through a 0.1 μm PTFE filter. The DMSO layer, which is the filtrate, was light yellow and contained no blue compound. The obtained blue substance and the PTFE filter to which the blue substance was attached were placed in a flask, and 100 ml of 1.0% by mass N-oleoyl-N-methyltaurine sodium salt aqueous solution was added to the flask, and after ultrasonic irradiation for 10 minutes (30 W , Using an ultrasonic cleaner with an oscillation frequency of 45 KHz) and stirring with a stirrer for 1 hour. When the solution was passed through a 0.45 μm CE filter, the blue color almost went to the filtrate and very little material was separated. When the particle diameter of the filtrate was measured, the volume average particle diameter MV was 55.8 nm (number distribution). When the pigment concentration was measured, it was 6.5% by mass of PB15 (copper phthalocyanine) pigment aqueous dispersion sample (A-6).

(Preparation of aqueous dispersion sample A-7)
Pigment Yellow 128 (Ciba Specialty Chemicals, CROMOPHTAL YELLOW 8GNP (trade name)) 80 g, 28% sodium methoxide methanol solution (Wako Pure Chemical Industries, Ltd.) 63 g, Aqualon KH-10 64 g, polyvinylpyrrolidone 20 g of K30 (trade name, manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 1,200 mL of dimethyl sulfoxide at room temperature, and this was used as an IF solution. Distilled water was used as the IIF solution. As the microreactor apparatus, the same three-dimensional microreactor apparatus of FIG. Two Teflon (registered trademark) tubes having a length of 50 cm and an equivalent diameter of 1 mm were connected to the two inlets using a connector, and syringes containing the IF solution and IIF solution were connected to the ends of the tubes and set in the pump. A Teflon (registered trademark) tube having a length of 10 m and an equivalent diameter of 8 mm was connected to the outlet of the connector.

  IF solution is 40mL / min in a 6m length (1m to 7m point from the outlet) of the Teflon tube connected to the outlet of the connector immersed in an oil bath maintained at 90 ° C for stabilization treatment heating. The IIF solution was sent out at a solution feed rate of 160 mL / min. Since a dispersion of Pigment Yellow 128 was obtained from the tip of the tube outlet, it was collected. The volume average diameter MV of the pigment particles of this liquid was 18.0 nm, and the ratio of volume average diameter Mv / number average diameter MN, which is an index of monodispersibility, was 1.35.

  After purifying this liquid while adding distilled water with an ultrafiltration apparatus (Advantech Toyo Co., Ltd., UHP-62K (trade name), molecular weight cut off 50,000) to eliminate the filtrate and keeping the volume constant, pigment 9. Concentrated to 0% by weight. When the concentrated dispersion is diluted to 1% by mass and the particle diameter is measured, the volume average diameter MV of the contained fine particles is 18.5 nm, and the volume average diameter MV / number average diameter MN, which is an index of monodispersity, The ratio was 1.36.

(Preparation of aqueous dispersion sample A-8)
An IG solution (1340 ml) was prepared in the same manner except that Aqualon KH-10 was removed from the IF solution in the preparation of the aqueous dispersion sample A-7. N-oleoyl-N-methyltaurine sodium salt (64 g) was dissolved in distilled water to prepare IIG solution (5360 ml). A pigment yellow 128 dispersion was obtained in exactly the same manner except that these liquids were replaced with the IF and IIF liquids in the aqueous dispersion sample A-7. The volume average diameter MV of the pigment particles of this liquid was 40.0 nm, and the ratio of volume average diameter MV / number average diameter MN, which is an index of monodispersibility, was 1.70. This liquid was concentrated in the same manner as in the aqueous dispersion sample A-7 to obtain a 10.5 mass% dispersion.

(Preparation of aqueous dispersion samples A-9 to A-12)
The particle size and particle size distribution of a pigment dispersion sample for comparison prepared by the breakdown method (ultrasonic dispersion) are shown below. The dispersant used was the surfactant Aqualon KH-10. The concentration was adjusted to 8% by mass.
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Sample MV MV / MN
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PR122 aqueous dispersion sample (A-9) 101.2 nm 2.2
PR254 aqueous dispersion sample (A-10) 105.7 nm 2.3
PY128 aqueous dispersion sample (A-11) 110.6 nm 2.2
PB15 aqueous dispersion sample (A-12) 98.8 nm 2.0
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(Production of water-based gel ink)
The aqueous dispersion samples A-1 to A-8 were used as colorants, and as shown in Table 1, the following additives (dispersant, shear thinning agent, water-soluble liquid medium, humectant, surfactant, (A preservative, a rust preventive, and a pH adjuster) and water were mixed (the values in the table are ratios in the total amount of 100% by mass), stirred, and coarse particles were filtered to prepare the aqueous gel ink samples 1 to 15 of the present invention. .

Separately from the above, comparative samples C1 to C6 shown in Table 1 were prepared using the aqueous dispersion samples A-9 to A-12.
<Dispersant>
B-1: Ammonium salt of styrene maleic acid resin (Daiichi Kogyo Seiyaku Co., Ltd., trade name: DISCOAT N-14)
B-2: Styrene acrylate resin ammonium salt (manufactured by Johnson Polymer Co., Ltd., trade name: Jonkrill 61J)
<Shear thinning agent>
C-1: Xanthan gum (trade name: KELZAN HP, manufactured by Sankisha Co., Ltd.)
C-2: Cross-linked polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., trade name: Hibiswako 105)
C-3: Polyvinylpyrrolidone (manufactured by GAF, trade name: PVP-K90)
<Water-soluble liquid medium>
D-1: Propylene glycol D-2: Ethylene glycol D-3: Diglycerin ethylene oxide 13 mol adduct (Sakamoto Yakuhin Kogyo Co., Ltd., trade name: SC-E750)
<Humectant>
E-1: Maltitol (product name: Amarty MR-50, manufactured by Towa Kasei Co., Ltd.)
E-2: Reducing oligosaccharide (manufactured by Nikken Chemical Co., Ltd., trade name: S100)
E-3: Reduced starch degradation product (Towa Kasei Kogyo Co., Ltd., trade name: PO-300)
<Surfactant>
F-1: alkyl phosphate ester (manufactured by Toho Chemical Co., Ltd., trade name: Phosphanol RS-610)
F-2: alkyl phosphate ester (manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RD-510Y)
<Preservative>
G-1: benzoisothiazoline (manufactured by Zeneca Co., Ltd., trade name: Proxel TN)
<Rust preventive>
-H-1: Benzotriazole (Chemipro Kasei Co., Ltd., trade name: Chemitech BT-G)
<PH adjuster>
・ I-1: Aminomethylpropanol ・ I-2: Triethanolamine

The ink viscosity and non-Newtonian viscosity index n values shown in Table 1 were measured by the following methods.
(1) Viscosity increase of ink viscosity The viscosity increase of each ink was measured according to the above-mentioned conditions of [Measurement of viscosity increase].
(2) Non-Newtonian viscosity index (n value)
The non-Newtonian viscosity index (n value) of each ink was measured according to the above-mentioned [Measurement and calculation of non-Newtonian viscosity index (n value)].

  In consideration of good writing quality as an ink for water-based gel ballpoint pens, practical requirements can be satisfied if the ink viscosity is 200 to 600 mPa · s, and high satisfaction is obtained if it is 300 to 500 mPa · s. can get. As for the viscosity increase, practical requirements can be satisfied if it is within ± 10%, and high satisfaction can be obtained if it is within ± 5%.

  Next, using a ball pen shaft, an inner diameter of 3.8 mm, a length of 113 mm, a polypropylene ink containing tube and a stainless tip (hard metal ball: ball diameter 0.3 mm), and the containing tube and the tip are connected. Refills made of joints to be filled were filled with the inks of Samples 1 to 15 and Comparative Samples C1 to C6, respectively. Next, a follower was loaded at the rear end of the ink to prepare each aqueous gel ink ballpoint pen. The following evaluation tests were conducted using the pen body. The results are shown in Table 2.

(1) Vibration scraping After the pen tip of the pen body with the cap removed is turned upward from the position of 5 cm in height from the rear end twice on the desk, the writing paper is 1 to 2 cm in diameter. The drawn state obtained by performing “spiral writing” was evaluated according to the following criteria.
◎: Normal writing possible within 3 laps ○: Normal writing possible within 5 laps △: Normal writing possible within 10 laps X: More than 10 laps of “spiral writing” are required before normal writing is achieved.

(2) Dry-up Under the conditions of a temperature of 50 ° C. and a relative humidity of 30% RH, the pen body with the cap removed was left in a horizontal and horizontal state for 16 hours, and then allowed to cool at 25 ° C. for 2 hours. “Spiral writing” was performed at a size of ˜2 cm, and the obtained drawn state was evaluated according to the following criteria.
◎: Normal writing possible within 3 laps ○: Normal writing possible within 5 laps △: Normal writing possible within 15 laps X: More than 15 laps of “spiral writing” are required before normal writing.

(3) Bleeding On the writing paper, “Fuji Film” was written with a size of about 1 cm in length and breadth, and the presence or absence of blotting of the handwriting at that time was visually observed and evaluated according to the following criteria.
◎: No bleeding at all ○: Slight bleeding to some extent △: Slightly blurred overall ×: Significant bleeding

(4) DC phenomenon After writing “spiral writing” with a diameter of about 2 cm on writing paper for 10 laps, immediately leave it for 5 minutes with the pen tip facing downward, and observe the ink flowing out of the pen tip. Evaluation was made according to the following criteria.
◎: Almost absent ○: Slightly present △: Slightly more ×: Many

(5) Line drawing quality Using a writing tester, the line drawing state of 200 m written under the conditions of 4.5 m / min, angle 60 °, and load 100 gf was evaluated according to the following criteria.
◎: Good ○: Slight shading △: Slight shading occurs depending on writing direction ×: Scratch occurs

(6) Writing Taste “Spiral writing” was performed on a writing paper with a ball pen with a diameter of about 2 cm, and the average writing quality obtained by repeating this 10 times was evaluated according to the following evaluation criteria.
◎: Smooth and stable writing taste ○: Writing taste that feels slightly caught Δ: Writing taste that feels slightly caught ×: Writing taste that feels caught slightly, and there are line breaks and directionality.

As shown in Table 1, the samples 1 to 17 of the present invention all have a non-Newtonian viscosity (n value) suitable as an aqueous gel ballpoint pen ink in the range of 0.40 to 0.80. Therefore, compared with the samples C1 to C6, the viscosity (mPa · s) was kept low in an appropriate range, and the viscosity increase (%) was also kept low. From this result, it is possible to make the aqueous gel ink have a suitable viscosity by using the ink composition of the present invention containing the build-up pigment fine particles as a colorant, and to improve the stability over time. I understand.
In addition, as shown in Table 2, the samples C1 to C6 for comparison in terms of vibration blur, dry-up, bleeding, DC phenomenon, line drawing quality, and writing quality are not practically sufficient (×) in any performance. was there.
On the other hand, Samples 1 to 17 of the present invention did not have insufficient (x) points in all the above performance items. Further, according to the present invention, extremely excellent performance (◎) can be realized in all items (Samples 1, 2, 12, and 16), and practical requirements can be satisfied at a high level. The handwriting of the aqueous gel ink of the present invention is clear in each color of red (samples 1-4, 7-13), yellow (samples 5, 14, 16, 17), and blue (samples 6, 15). It was.

(Example 2 and Comparative Example 2)
(Preparation of water-soluble resin P-1)
Water-soluble resin P-1 having a mass average molecular weight of 130,000 is obtained by adding 2.2 parts of dimethyl terephthalate to 100 parts of polyethylene glycol (mass average molecular weight of 10,000) obtained by adding ethylene oxide to ethylene glycol. Got.

(Preparation of water-soluble resin P-2)
100 parts by mass of polyalkylene oxide compound (mass average molecular weight 20,000) obtained by block addition polymerization of 85% ethylene oxide and 15% propylene oxide to bisphenol A, 0.84 parts by mass of hexamethylene diisocyanate and a small amount of dibutyl Tin dilaurate was added and urethanized at 100 ° C. to obtain a water-soluble resin P-2 of a hydrophilic polymer compound having a mass average molecular weight of 250,000.

(Preparation of emulsion EM-1)
35 parts by mass of water, 50 parts by mass of hexadecyl 2-ethylhexanoate, 3 parts by mass of sodium oleate, 2 parts by mass of sodium lauryl sulfate, and 10 parts by mass of glycerin were stirred and emulsified with a homogenizer, hexadecyl 2-ethylhexanoate Emulsion EM-1 was obtained.

(Preparation of emulsion EM-2)
56 parts by mass of water, 30 parts by mass of butyl oleate, 3.18 parts by mass of sorbitan nonionic active agent nonion OP80R (trade name) (manufactured by NOF Corporation), and nonion OT221 (trade name) (manufactured by NOF Corporation) 82 parts by mass Glycerol 10 parts by mass was stirred and emulsified with a homogenizer to obtain butyl oleate emulsion EM-2.

(Production of water-based marking pen ink)
The aqueous dispersion samples A-1 to A-8 and the water-soluble resins P-1, P-2, emulsions EM-1, EM-2, fluorosurfactants (Florard FC128 (trade name), Sumitomo 3M Co., Ltd.), water, and ethanol were mixed at the mixing ratio shown in Table 3 (the values in the table are ratios in the total amount of 100% by mass) to prepare ink samples 18 to 25 of the present invention. Next, ink samples C7 to C10 for comparison shown in Table 3 were produced using the aqueous dispersion samples A-9 to A-12.

  With respect to the ink samples 18 to 25 and the samples C7 to C10, the viscosity increase was measured under the conditions described in the above [Measurement of viscosity increase]. When the viscosity increase was within ± 5%, it was good (◯), when it was within ± 10%, it was slightly insufficient (Δ), and when it exceeded that, it was insufficient (×). The results are shown in Table 3 as ink stability.

  Next, Samples 18 to 25 and Comparative Samples C7 to C10 were respectively placed on the marker shaft, written on a melamine baked white board, and after 5 minutes, the handwriting was rubbed with a dry cloth to erase the handwriting (initial erasability). ) And erasability after standing for 15 days (daily erasability). Good (○) when almost erased by rubbing within 2 times, slightly insufficient (△) when almost erased by 2 to 4 times, and insufficient (×) when more times are required did. The results are shown in Table 3.

  As shown in Table 3, all of the samples 18 to 25 of the present invention showed good results in all of the ink stability, initial erasability, and day-to-day erasability with respect to the comparative samples C7 to C10. The handwriting of the marking pen ink of the present invention was dark and clear in each color of red (samples 18 to 21), yellow (samples 22, 24, and 25), and blue (sample 23).

It is a disassembled perspective view which shows typically one embodiment of a center collision type | mold microreactor apparatus. It is explanatory drawing of the reaction apparatus which has a Y-shaped channel. It is sectional drawing of the III-III line of FIG.

Explanation of symbols

100, 200 reactor (microreactor)
DESCRIPTION OF SYMBOLS 11 Supply block 12 Merge block 13 Reaction block 16 Outer annular groove 15 Inner annular groove 17, 18 Through hole of supply block 20 Merge part (merging area)
21 Long radial groove 22 Short radial groove 23 Through-hole of reaction block (liquid mixing space consisting of micro flow path)
25, 26 Through-holes 111, 112 in the confluence block 113 Inlet 113 Channel 113a, 113b Inlet channel 113c Reaction channel (liquid mixing space consisting of micro channels)
113d Fluid confluence 114 Discharge port

Claims (11)

  An ink composition for stationery, comprising pigment fine particles having a ratio (MV / MN) of volume average particle diameter (MV) to number average particle diameter (MN) of 1.80 or less.   2. The ink composition for stationery according to claim 1, wherein the pigment fine particles are build-up pigment fine particles.   The build-up pigment fine particles are obtained by bringing a pigment solution obtained by dissolving a pigment in a good solvent and a poor solvent into contact with each other in the presence of a dispersant to precipitate the pigment as nanometer-sized fine particles. Item 3. An ink composition for stationery.   The ink composition for stationery according to claim 3, wherein the pigment solution and the poor solvent are brought into contact with each other in a flow process in the flow path.   The ink composition for stationery according to claim 3 or 4, wherein the pH of the pigment solution is changed by contact between the pigment solution and a poor solvent.   A water-based gel ink comprising the stationery ink composition according to any one of claims 1 to 5.   The water-based gel ink according to claim 6, which exhibits non-Newtonian viscosity.   8. The water-based gel ink according to claim 7, wherein the n value of the non-Newtonian viscosity index is 0.40 to 0.80.   The water-based gel ink according to any one of claims 6 to 8, wherein the ink is used for a ballpoint pen.   Maltitol, reducing sugar based on maltitol, sorbitol, reducing sugar based on sorbitol, reducing oligosaccharide, reduced maltooligosaccharide, reduced starch degradation product, reduced dextrin, reduced maltodextrin, α-cyclodextrin, β The aqueous gel ink according to any one of claims 6 to 9, wherein one or more selected from the group consisting of cyclodextrin and maltosyl cyclodextrin are contained as a moisturizing agent.   A water-based marking pen ink comprising the stationery ink composition according to any one of claims 1 to 5.

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