JP5431897B2 - Method for producing aqueous dispersion for ink jet recording - Google Patents

Description

  The present invention relates to a method for producing an aqueous dispersion for inkjet recording excellent in ejection reliability, and an aqueous ink containing the aqueous dispersion obtained by the method.

The ink jet recording system is a recording system in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle and attaching them to a recording member. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording member and non-contact with the object to be printed.
In recent years, pigment-based inks in which pigments are dispersed in water have been mainly used as inks used for inkjet recording, from the viewpoint of water resistance and weather resistance.

In Patent Document 1, for the purpose of improving storage stability, glossiness, and the like, it is composed of a resin and a pigment having an acid value of 30 to 120 based on a carboxy group, and the pH is neutral or acidic with an acidic compound. Disclosed is a method for producing an aqueous pigment dispersion having a specific average particle size in which a water-containing cake obtained by a step of fixing to a pigment is dispersed in an aqueous medium by neutralizing a carboxy group with a basic compound. Has been.
In Patent Document 2, a water-based ink containing a colorant, a thickener, and water is different from a kind of gas such as nitrogen or a rare gas or the atmosphere for the purpose of preventing blur due to the generation of bubbles over time and preventing corrosion. Disclosed is an ink manufacturing method in which a gas mixture of composition is dissolved in the ink.

JP-A-9-31360 JP 2004-352917 A

If ink using a dispersible colorant that is insoluble in water such as pigment is used for inkjet, the discharge nozzle part of the inkjet printer is fine, so deposits due to drying etc. are likely to remain on the discharge nozzle part and clogging There is a problem that ejection failures such as these are likely to occur.
An object of the present invention is to provide a method for producing an aqueous dispersion for inkjet recording excellent in ejection reliability, and an aqueous ink containing the aqueous dispersion obtained by the method.

The present inventors have found that the reason why it is difficult to obtain sufficient ejection reliability with an ink using a dispersible color material insoluble in water, such as pigment, is that the color material and particle size are not sufficiently adsorbed by the dispersant. We considered that the particles are unstable particles that tend to aggregate due to drying of ink such as small coloring materials. As a result, it was found that the discharge reliability can be improved by mixing and dispersing an aqueous dispersion containing anionic colored particles and carbon dioxide gas.
That is, the present invention provides the following (1) to (2).
(1) A method for producing an aqueous dispersion for inkjet recording, comprising the following steps (I) to (III).
Step (I): An aqueous dispersion containing anionic colored particles having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s and carbon dioxide gas are mixed, and the viscosity (B) at 25 ° C. is 100 mPa. -Step of obtaining a thickened product that is s or more Step (II): Step of mixing the thickened product obtained in Step (I) and water Step (III): Dispersing the mixture obtained in Step (II) Process (2) Water-based ink for ink-jet recording containing the water dispersion obtained by the method of (1).

  According to the production method of the present invention, it is possible to efficiently produce an aqueous dispersion for inkjet recording excellent in ejection reliability. The water-based ink containing this water dispersion is excellent in ejection reliability.

The method for producing an aqueous dispersion for inkjet recording of the present invention comprises the following steps (I) to (III).
Step (I): An aqueous dispersion containing anionic colored particles having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s and carbon dioxide gas are mixed, and the viscosity (B) at 25 ° C. is 100 mPa. -Step of obtaining a thickened product that is s or more Step (II): Step of mixing the thickened product obtained in Step (I) and water Step (III): Dispersing the mixture obtained in Step (II) Process to Process The reason why the water dispersion obtained by the production method of the present invention and the water-based ink containing the water dispersion are excellent in ejection reliability is not clear, but is considered as follows.
When the aqueous dispersion containing anionic colored particles is treated with carbon dioxide gas to lower the pH of the aqueous dispersion, the dispersion state of the anionic colored particles in the aqueous dispersion becomes slightly unstable, Of the particles in the dispersion, only unstable particles such as a color material that is not sufficiently adsorbed with a dispersant or a color material having a very small particle size selectively and strongly aggregates in an attempt to maintain a stable state. By dispersing this agglomerate, the unstable part is not crushed and only the part that can be stably dispersed is crushed and dispersed again in the aqueous medium, so that the obtained aqueous dispersion and the aqueous system containing it are obtained. The ink is considered to be excellent in ejection reliability.
Carbon dioxide gas will be destabilized too much when mixed with the water dispersion, will not cause the particles to aggregate more than necessary, and will be removed before the dispersion process, so It is considered that the discharge reliability is improved without leaving impurities such as inorganic substances that have an adverse effect. On the other hand, when using, for example, an aqueous hydrochloric acid solution as the acidic substance, a concentrated region of the acidic substance is born in the aqueous dispersion when the aqueous hydrochloric acid solution is dropped, and all particles are firmly aggregated in the region. Thereafter, it is considered that the ink cannot be sufficiently dispersed, and the discharge reliability cannot be improved.
Hereinafter, each component and process used in the present invention will be described.

[Anionic colored particles]
The anionic colored particles used in the present invention are not particularly limited as long as they are anionic particles containing a colorant. For example, (i) particles consisting only of a colorant such as a pigment, (ii) particles where a colorant is dispersed with an anionic surfactant, (iii) a colorant is dispersed with an anionic polymer dispersant Particles, (iv) anionic polymer particles containing a colorant, and the like.
From the viewpoint of improving the dispersion stability in the ink and the printing density of the ink, anionic pigment particles in which the colorant is a pigment are preferred, (iv) anionic polymer particles containing a colorant are more preferred, and a pigment is used. More preferably, the anionic polymer particles are contained. Further, (iv) the anionic polymer particle containing a colorant may be an anionic crosslinked polymer particle containing a colorant, and includes, for example, an anionic polymer particle containing a colorant as described later. A crosslinking agent can be added to the aqueous dispersion to obtain an aqueous dispersion of anionic crosslinked polymer particles containing a colorant.

In the present specification, “anionic” means that when an unneutralized compound or the like is dispersed or dissolved in pure water, the pH is less than 7, or the compound or the like is insoluble in pure water. When the pH cannot be measured clearly, it means that the zeta potential of the dispersion dispersed in pure water becomes negative.
The average particle diameter of the anionic colored particles is preferably 30 to 300 nm, more preferably 40 to 200 nm, still more preferably 50 to 150 nm, and particularly preferably 60 to 90 nm from the viewpoint of the printing density of the ink. The average particle size is measured by the method described in the examples.

(Coloring agent)
The colorant used for the anionic colored particles is not particularly limited, and pigments, hydrophobic dyes and the like can be used. From the viewpoint of printing density, pigments and hydrophobic dyes are preferable, and pigments are more preferable.
When the pigment and the hydrophobic dye are used in an aqueous dispersion and an aqueous ink, it is preferable to use a surfactant and a polymer to form fine particles that are stable in the aqueous dispersion and the aqueous ink. In particular, from the viewpoints of bleeding resistance, water resistance, and the like, it is preferable to include a pigment and / or a hydrophobic dye in the polymer particles.
The pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with extender pigments.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. In the black water-based ink, carbon black is preferable. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
The hue is not particularly limited, and any chromatic color pigment such as a red organic pigment, a yellow organic pigment, a blue organic pigment, an orange organic pigment, or a green organic pigment can be used.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed. Moreover, solid solution pigments, such as a quinacridone solid solution pigment, can be used.
The quinacridone solid solution pigment includes unsubstituted quinacridone such as β-type and γ-type, and dichloroquinacridone such as 2,9-dichloroquinacridone, 3,10-dichloroquinacridone, and 4,11-dichloroquinacridone. The quinacridone solid solution pigment is preferably a solid solution pigment comprising a combination of unsubstituted quinacridone (CI Pigment Violet 19) and 2,9-dichloroquinacridone (CI Pigment Red 202).

In the present invention, a self-dispersing pigment can also be used. Self-dispersing pigments are those in which one or more hydrophilic functional groups (anionic hydrophilic groups such as carboxy groups and sulfonic acid groups, or cationic hydrophilic groups such as quaternary ammonium groups) are directly or other atomic groups. It means an inorganic pigment or an organic pigment that can be dispersed in an aqueous medium without using a surfactant or a resin.
The hydrophobic dye is not particularly limited as long as it can be contained in the polymer particles. The hydrophobic dye is dissolved in an amount of 2 g / L or more, preferably 20 to 500 g / L (25 ° C.) with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer from the viewpoint of efficiently containing the dye in the polymer. What to do is desirable.
Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable. Examples of the oil-soluble dye include C.I. I. Solvent Black, C.I. I. Solvent Yellow, C.I. I. Solvent Red, C.I. I. Solvent Violet, C.I. I. Solvent Blue, C.I. I. Solvent Green, and C.I. I. One or more types of products selected from the group consisting of Solvent Orange are listed, which are commercially available from Orient Chemical Co., Ltd., BASF Co., etc.
The above colorants can be used alone or in admixture of two or more at any ratio.

[Anionic polymer particles containing colorant]
(Anionic polymer)
The anionic polymer used for the anionic polymer particles containing the colorant (hereinafter also referred to as “colorant-containing polymer particles”) is a water-insoluble polymer from the viewpoint of improving the print density of the aqueous dispersion and aqueous ink. It is preferable. Here, the water-insoluble polymer refers to a polymer that is dried at 105 ° C. for 2 hours and dissolved in 100 g of water at 25 ° C. and has a dissolution amount of 10 g or less. The amount is preferably 5 g or less, and more preferably 1 g or less. The dissolution amount is the dissolution amount when the anionic group of the polymer is neutralized 100% with sodium hydroxide.
Examples of the polymer to be used include polyester, polyurethane, and vinyl polymer. From the viewpoint of storage stability of the aqueous dispersion, vinyl obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound). Based polymers are preferred.

  The anionic vinyl polymer includes a monomer mixture (a) an anionic monomer (hereinafter also referred to as “(a) component”) and (b) a hydrophobic monomer (hereinafter also referred to as “(b) component”) ( In the following, a vinyl polymer obtained by copolymerizing a simple monomer mixture) is preferred. This vinyl polymer has a structural unit derived from the component (a) and a structural unit derived from the component (b). Especially, what contains the structural unit derived from (c) macromer (henceforth "(c) component") is preferable.

[(A) Anionic monomer]
(A) The anionic monomer is used as a monomer component of the anionic polymer in order to stably disperse the colorant-containing polymer particles in the aqueous dispersion and the aqueous ink.
Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and 3-sulfopropyl (meth) acrylate.
Examples of the phosphoric acid monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, and the like.
Among the anionic monomers, a carboxylic acid monomer is preferable and acrylic acid and methacrylic acid are more preferable from the viewpoint of dispersion stability of the colorant-containing polymer particles in an aqueous dispersion and an aqueous ink.

[(B) Hydrophobic monomer]
(B) The hydrophobic monomer is used as a monomer component of the anionic polymer from the viewpoint of enhancing the adsorption of the polymer to the pigment and enhancing the ejection reliability of the water-based ink. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates. “(Meth) acrylate” indicates acrylate and / or methacrylate.

As the aromatic group-containing monomer, a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a hetero atom, is preferable, and a styrene monomer or an aromatic group-containing (meth) acrylate. Are more preferable, and it is also preferable to use these in combination.
As the styrenic monomer, styrene, 2-methylstyrene, and divinylbenzene are preferable, and styrene is more preferable.
Moreover, as an aromatic group containing (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable, and benzyl (meth) acrylate is more preferable.
[(C) Macromer]
(C) A macromer is a compound having a number average molecular weight of 500 to 100,000 having a polymerizable functional group at one end, and from the viewpoint of storage stability in an aqueous dispersion and aqueous ink of colorant-containing polymer particles, Used as a monomer component of an anionic polymer. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and more preferably a methacryloyloxy group. (B) The number average molecular weight of the macromer is preferably from 500 to 100,000, more preferably from 1,000 to 10,000. The number average molecular weight is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent.
(C) As the macromer, from the viewpoint of dispersion stability of the colorant-containing polymer particles in an aqueous dispersion and an aqueous ink, an aromatic group-containing monomer macromer and a silicone macromer are preferable, and an aromatic group-containing monomer macromer. Is more preferable.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromer include the aromatic group-containing monomers described in the above (b) hydrophobic monomer, styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable. preferable.
Specific examples of the styrenic macromer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.

[(D) Nonionic monomer]
The monomer mixture preferably further contains (d) a nonionic monomer (hereinafter also referred to as “component (d)”).
(D) As a component, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polypropylene glycol (n = 2-30, n shows the average addition mole number of an oxyalkylene group. The same hereafter). Polyalkylene glycol (meth) acrylates such as (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylates such as methoxypolyethylene glycol (1-30) (meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymer) (1 to 1) 30, ethylene glycol: 1 to 29) (meth) acrylate and the like among them, polypropylene glycol (n = 2 to 30) (meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymer) (Meth) acrylate are preferable, polypropylene glycol (n = 2 to 30) (meth) acrylate are more preferred.
Specific examples of the commercially available component (d) include NK Esters M-20G, 40G, and 90G from Shin-Nakamura Chemical Co., Ltd., Bremer PE-90, 200, and 200 from NOF Corporation. 350, PME-100, 200, 400, etc., PP-500, 800, etc., AP-150, 400, 550, 50PEP-300, 50POEP-800B, 43PAPE-600B, and the like.
The components (a) to (d) can be used alone or in admixture of two or more.

Content (a) to (d) component in the monomer mixture of the above-mentioned components (a) to (d) at the time of vinyl polymer production (content as an unneutralized amount, the same applies hereinafter) or vinyl polymer The content of the structural unit derived from is as follows.
The content of the component (a) is preferably 3 to 40% by weight, more preferably 4 to 30% by weight, particularly preferably from the viewpoint of stably dispersing the colorant-containing polymer particles in the aqueous dispersion and the aqueous ink. 5 to 25% by weight.
The content of component (b) is preferably 5 to 98% by weight, more preferably 10 to 80% by weight, from the viewpoint of improving the print density of the aqueous dispersion and aqueous ink.
The content of the component (c) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, from the viewpoint of dispersion stability of the colorant-containing polymer particles in the aqueous dispersion and aqueous ink.
The content of the component (d) is preferably 5 to 60% by weight, more preferably 15 to 50% by weight, from the viewpoint of improving the dispersibility of the aqueous dispersion and the aqueous ink.
The weight ratio of [(a) component / [(b) component + (c) component]] is determined by the dispersion stability of the colorant-containing polymer particles in the aqueous dispersion and aqueous ink, and the aqueous dispersion and aqueous ink. From the viewpoint of the print density, it is preferably 0.01 to 1, more preferably 0.02 to 0.67, and still more preferably 0.03 to 0.50.

(Production of anionic polymer)
The anionic polymer is produced by copolymerizing a monomer mixture by a known polymerization method. As the polymerization method, a solution polymerization method is preferable.
Although there is no restriction | limiting in the solvent used by the solution polymerization method, Polar organic solvents, such as C1-C3 aliphatic alcohol, ketones, ethers, and esters, are preferable, specifically, methanol, ethanol, acetone, and methyl ethyl ketone. And methyl ethyl ketone is preferred.
In the polymerization, a polymerization initiator or a polymerization chain transfer agent can be used. As the polymerization initiator, 2,2′-azobis (2,4-dimethylvaleronitrile) is preferable, and the polymerization chain transfer agent is used. Is preferably 2-mercaptoethanol.
Although preferable polymerization conditions vary depending on the type of polymerization initiator and the like, the polymerization temperature is preferably 50 to 80 ° C., and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen or argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. In addition, unreacted monomers and the like can be removed from the obtained polymer by reprecipitation, membrane separation, chromatographic methods, extraction methods and the like.
The weight average molecular weight of the anionic polymer used in the present invention is preferably from 5,000 to 500,000, preferably from 10,000 to 400,000, from the viewpoint of dispersion stability of the colorant-containing polymer particles in the aqueous dispersion and aqueous ink. Is more preferable, 10,000 to 300,000 is still more preferable, and 20,000 to 300,000 is particularly preferable. In addition, the weight average molecular weight of a polymer is measured by the method shown in an Example.

[Production of Anionic Polymer Particles Containing Colorant]
Anionic polymer particles containing a colorant (colorant-containing polymer particles) can be efficiently produced as an aqueous dispersion of colorant-containing polymer particles by a method having the following steps (1) and (2). it can.
In addition, from the viewpoint of the storage stability of the aqueous dispersion and the water-based ink, the following step (3) is performed, whereby an anionic crosslinked polymer particle containing a colorant (hereinafter also referred to as “colorant-containing crosslinked polymer particle”). ).
Step (1): A step of dispersing a mixture containing an anionic polymer, an organic solvent, a colorant, and water to obtain a dispersion of colorant-containing polymer particles Step (2): obtained in step (1) Step of removing the organic solvent from the obtained dispersion to obtain an aqueous dispersion of colorant-containing polymer particles Step (3): adding a crosslinking agent to the dispersion obtained in step (2) to contain a colorant Step of obtaining an aqueous dispersion of crosslinked polymer particles

Process (1)
In the step (1), first, an anionic polymer is dissolved in an organic solvent to obtain an organic solvent solution of the polymer, and the organic solvent solution is added with a colorant, water, and a neutralizer, a surfactant and the like as necessary. Is preferably added to the obtained organic solvent solution and mixed to obtain an oil-in-water dispersion. Although there is no restriction | limiting in the order added to the organic solvent solution of an anionic polymer, It is preferable to add in order of a neutralizing agent, water, and a coloring agent. As the organic solvent solution of the polymer, a polymer solution obtained by polymerizing the polymer may be used as it is or further diluted with an organic solvent.
In the mixture, the colorant is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the anionic polymer is 2-40 weight% is preferable, 3-20 weight% is more preferable, 10-70 weight% is preferable and, as for water, 20-70 weight% is more preferable.
The weight ratio of the amount of the colorant to the amount of the anionic polymer [colorant / anionic polymer] is preferably 50/50 to 90/10 from the viewpoint of dispersion stability of the colorant-containing polymer particles. More preferably, it is 70/30 to 85/15.
When using a neutralizing agent, it is preferable to neutralize so that pH may be 7-11. Examples of the neutralizing agent include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and various amines. Further, the anionic polymer may be neutralized in advance.
Although there is no restriction | limiting in the organic solvent in which an anionic polymer is dissolved, C1-C3 aliphatic alcohol, ketones, ethers, esters, etc. are preferable and methyl ethyl ketone is preferable. When the anionic polymer is synthesized by a solution polymerization method, the solvent used in the polymerization may be used as it is.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (1). Although the average particle size of the colorant-containing polymer particles can be atomized only by the main dispersion until the desired particle size is obtained, it is preferably pre-dispersed and then subjected to the main dispersion by further applying a shearing stress. It is preferable to control the average particle size of the contained polymer particles to a desired particle size. The temperature in the dispersion in the step (1) is preferably 0 to 50 ° C., more preferably 0 to 35 ° C., and the dispersion time is preferably 1 to 30 hours, more preferably 2 to 25 hours.
When the mixture is predispersed, a commonly used mixing and stirring device such as an anchor blade, particularly a high-speed stirring and mixing device is preferable.
Examples of means for imparting the shear stress of the present dispersion include a kneader such as a roll mill and a kneader, a high-pressure homogenizer such as a microfluidizer (trade name), a media shaker such as a paint shaker and a bead mill. Examples of commercially available media dispersers include Ultra Apex Mill (trade name, manufactured by Kotobuki Industries Co., Ltd.), Pico Mill (trade name, manufactured by Asada Tekko Co., Ltd.), and the like. A plurality of these devices can be combined. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle diameter of the colorant-containing polymer particles.
In order to remove coarse particles from the obtained aqueous dispersion, membrane treatment such as dialysis and ultrafiltration, centrifugation treatment, gel filtration treatment, etc. are preferably performed. From the viewpoint of efficiency and cost, centrifugation treatment is performed. More preferably.

Process (2)
In step (2), an aqueous dispersion of colorant-containing polymer particles can be obtained by distilling off the organic solvent from the obtained dispersion by a known method. The organic solvent in the aqueous dispersion containing the obtained colorant-containing polymer particles is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. When performing, if necessary, it may be removed again after crosslinking. The amount of the residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
If necessary, the dispersion can be heated and stirred before the organic solvent is distilled off.
The resulting aqueous dispersion of the colorant-containing polymer particles is one in which the solid content of the polymer containing the colorant is dispersed in water as the main medium. Here, the form of the colorant-containing polymer particles is not particularly limited as long as the particles are formed of at least the colorant and the anionic polymer. For example, a particle form in which a colorant is included in the polymer, a particle form in which a colorant is uniformly dispersed in the polymer, a particle form in which a colorant is exposed on the polymer particle surface, and the like are included.

Step (3)
Step (3) is a step in which a crosslinking agent is added to the dispersion obtained in step (2) to obtain an aqueous dispersion of colorant-containing crosslinked polymer particles.
The crosslinking of the anionic polymer can also be performed by mixing the dispersion of the colorant-containing polymer particles obtained in the step (1) and the crosslinking agent. In this case, the aqueous dispersion of the present invention is obtained by performing the step of removing the organic solvent from the aqueous dispersion of the anionic crosslinked polymer particles obtained in the crosslinking step in the same manner as in the step (2). Can do.
The crosslinking treatment of the anionic polymer may be performed before removing the organic solvent in the step (2), but is preferably performed after the step (2) from the viewpoint of improving storage stability. By cross-linking after the step (2), it is considered that cross-linking occurs more appropriately between the polymer particles, and the storage stability of the aqueous dispersion and aqueous ink of the present invention can be further improved.
Here, preferable examples of the crosslinking agent include a compound having two or more epoxy groups in the molecule, a compound having two or more oxazoline groups in the molecule, and a compound having two or more isocyanate groups in the molecule. In these, the compound which has a 2 or more epoxy group in a molecule | numerator is preferable, and a trimethylol propane polyglycidyl ether is more preferable.

The colorant-containing polymer particles or the colorant-containing crosslinked polymer particles obtained by the above method are treated by mixing carbon dioxide gas as an aqueous dispersion having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s. The The viscosity (A) at 25 ° C. can be adjusted by adjusting the amount of water and, if necessary, the amount of the organic solvent to be added.
The average particle diameter of the colorant-containing polymer particles or the colorant-containing crosslinked polymer particles is preferably 40 to 1000 nm, more preferably 60 to 600 nm, and still more preferably, from the viewpoint of the print density of the aqueous dispersion and the water-based ink. 80-300 nm. The average particle size is measured by the method described in the examples.

[Production of water dispersion for inkjet recording]
The method for producing an aqueous dispersion for inkjet recording of the present invention includes the following steps (I) to (III).
Step (I): An aqueous dispersion containing anionic colored particles having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s and carbon dioxide gas are mixed, and the viscosity (B) at 25 ° C. is 100 mPa. -Step of obtaining a thickened product that is s or more Step (II): Step of mixing the thickened product obtained in Step (I) and water Step (III): Dispersing the mixture obtained in Step (II) Process to Process In the method for producing an aqueous dispersion for inkjet recording of the present invention, the following process (IV) is preferably performed between the process (II) and the process (III) from the viewpoint of improving discharge reliability.
Step (IV): A step of removing carbon dioxide gas from the mixture obtained in Step (I) and raising the pH by 0.1 or more.

(Process (I))
In step (I), an aqueous dispersion containing anionic colored particles having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s and carbon dioxide gas are mixed, and the viscosity (B) at 25 ° C. This is a step of obtaining a thickened product having a viscosity of 100 mPa · s or more.
As the aqueous dispersion containing the anionic colored particles, those prepared by the method for producing the anionic polymer particles containing the colorant can be preferably used, but the viscosity at 25 ° C. is 50 mPa · s. When exceeding, it dilutes with water or a water-soluble organic solvent, makes the viscosity in 25 degreeC below 50 mPa * s, and uses it for this process.
The viscosity (A) at 25 ° C. of the aqueous dispersion containing the anionic colored particles is 1 to 50 mPa · s. From the viewpoint of ink ejection reliability and good mixing with carbon dioxide gas, 2 20 mPa · s is preferable, 2 to 10 mPa · s is more preferable, and 3 to 6 mPa · s is still more preferable.

In the step (I), there is no particular limitation on the mixing method of the aqueous dispersion containing anionic colored particles and carbon dioxide gas, but a method of introducing carbon dioxide gas into the aqueous dispersion containing anionic colored particles is preferable. .
Specific examples of the carbon dioxide gas introduction method include the following methods (i) to (iv).
(I) A tube is connected to a gas cylinder or a gas generating device, the other end of the tube is put into a container of an aqueous dispersion containing anionic colored particles, and carbon dioxide gas is passed through the aqueous dispersion. Method.
(Ii) A method of introducing carbon dioxide gas into an aqueous dispersion by putting an aqueous dispersion containing anionic colored particles into a decompressed container and opening the container in an atmosphere containing carbon dioxide gas.
(Iii) A method in which a partially opened container containing an aqueous dispersion containing anionic colored particles is placed in an atmosphere containing carbon dioxide gas, pressurized, and carbon dioxide gas is introduced into the aqueous dispersion.
(Iv) Put a solution of carbon dioxide gas dissolved in a solvent into a sealed container, connect a tube to the sealed container, and put the other end of the tube into a container of an aqueous dispersion containing anionic colored particles, A method of introducing the generated carbon dioxide gas into an aqueous dispersion by heating the solution.
(V) A sublimable solid that becomes carbon dioxide gas upon sublimation is charged into an aqueous dispersion containing anionic colored particles, and gas is directly generated in the aqueous dispersion using sublimation phenomenon, and the carbon dioxide gas is converted into water. Introducing into the dispersion.
Among these, the method (i) in which the introduction of gas is easy to adjust is preferable from the viewpoint of preventing rapid destabilization and improving ink ejection reliability.
Also in the method (i), as a device for generating carbon dioxide gas, it is possible to accurately determine the amount of gas added by using a container containing a sublimable solid that becomes carbon dioxide gas when sublimated as listed in (v). This is preferable from the standpoints that it can be performed, and that sudden instability is prevented and ink ejection reliability is improved.
As the sublimable solid that becomes carbon dioxide gas, dry ice is preferably used.

The mixing amount of the carbon dioxide gas is preferably 1 to 300 parts by weight with respect to 100 parts by weight of the anionic colored particles. The carbon dioxide gas obtained by sublimation of dry ice is used as the carbon dioxide gas. The amount of ice is preferably 1 to 300 parts by weight and more preferably 10 to 200 parts by weight with respect to the anionic colored particles.
In the step of mixing the aqueous dispersion containing anionic colored particles and carbon dioxide gas of the present invention, the pH of the dispersion before mixing the carbon dioxide gas is 7.0 to improve the ink ejection reliability. 10.0 is preferable, 8.0 to 9.5 is more preferable, and 8.5 to 9.5 is more preferable.
Further, from the viewpoint of increasing the print density of the aqueous dispersion and aqueous ink, it is preferable to lower the pH of the aqueous dispersion by 0.5 to 6.0 by mixing carbon dioxide gas, and 2.0 to 4. It is more preferable to reduce it to 0, and it is further preferable to decrease it by 2.5 to 3.5.
However, the pH after carbon dioxide gas mixing is measured after mixing water in step (II).

In the step (I), a thickened product having a viscosity of 100 mPa · s or more is obtained by mixing an aqueous dispersion containing anionic colored particles and carbon dioxide gas.
The viscosity (B) of the thickened material is preferably 200 mPa · s or more, and more preferably 300 mPa · s or more, from the viewpoint of aggregating unstable fine particles and improving ejection reliability. Further, the upper limit of the viscosity (B) is preferably 1200 mPa · s or less, more preferably 800 mPa · s or less, from the viewpoint of efficiently performing the mixing step of the step (II) and the dispersion step of the step (III).
From the above viewpoint, the viscosity (B) of the thickened material is preferably 100 to 1200 mPa · s, and more preferably 300 to 800 mPa · s.
Moreover, it is preferable that the viscosity (B) of a thickened material is 20 times or more of the viscosity (A) in 25 degreeC of this aqueous dispersion. The viscosity (B) of the thickened material is preferably 20 to 1000 times, more preferably 20 to 300 times, more preferably 70 to 300 times the viscosity (A) from the viewpoint of aggregating unstable fine particles and improving ejection reliability. 200 times is more preferable.
The thickened material obtained in this step is preferably pasty. Here, “paste-like” means a state that has fluidity but does not follow when the container is shaken.

(Process (II))
Step (II) is a step of mixing the thickened product obtained in step (I) with water.
The water mixed in the thickened material may contain a water-soluble organic solvent or the like as long as the effects of the present invention are not impaired, but water alone is more preferable. There is no particular limitation on the method of mixing the thickened material and water, but a method of adding water to the container in which the thickened material is obtained and mixing is preferable. From the viewpoint of sufficient mixing, a stirrer or the like is used. preferable.
Moreover, when performing process (IV), you may mix this thickener and water in the container for removing the carbon dioxide gas used by process (IV).
The pH of the dispersion after adding water in step (II) is preferably 4.0 to 7.0, and more preferably 5.0 to 5.8.

(Process (III))
Step (III) is a step of dispersing the mixture obtained in step (II) or step (IV) described later.
As the dispersion conditions and the dispersion apparatus used for dispersion in the step (III), those used in the production of the anionic polymer particles containing the colorant are preferably used. Among them, a high-pressure homogenizer is preferable, and a chamber-type high-pressure homogenizer is preferably used. More preferred. Specifically, a microfluidizer (trade name, Microfluidics) is preferably used.
The temperature in the step (III) is preferably 5 to 50 ° C, more preferably 10 to 35 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 2 to 25 hours.

(Process (IV))
Step (IV) is a step of removing carbon dioxide gas from the mixture obtained in step (II) and raising the pH by 0.1 or more.
Even if the step (IV) is not performed, since the carbon dioxide gas is a gas, it is removed in the dispersion treatment step performed in the step (III) performed after this step, so that the effect of the present invention can be obtained. By removing the carbon dioxide gas before the dispersion treatment step, it is possible to obtain an aqueous dispersion and water-based ink with less change in viscosity and the like during storage.
The pH to be raised before and after the step (IV) of removing the carbon dioxide gas is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1.0 or more, and particularly preferably 2.0 or more. The upper limit of the pH to be raised is preferably 6.0 or less, more preferably 4.0 or less, and still more preferably 3.7 or less.
Further, from the viewpoint of improving the ink ejection reliability, the pH after carbon dioxide gas removal is preferably 7.0 to 10.0, and more preferably 8.0 to 9.0.
The method for removing carbon dioxide gas from the mixture obtained in step (II) is not particularly limited. For example, the method for removing the mixture by heating, the method for removing the mixture by sealing the container containing the mixture and reducing the pressure. The method of performing both simultaneously is preferable.
As a heating temperature, 40-80 degreeC is preferable and 50-70 degreeC is more preferable from a viewpoint of maintaining the dispersion stability of a dispersion liquid and improving discharge reliability.
The absolute pressure when removing under reduced pressure is preferably 1 to 50 kPa, more preferably 5 to 20 kPa, from the viewpoint of maintaining dispersion stability of the dispersion and improving ejection reliability.
As an apparatus for removing carbon dioxide gas from the mixture, an apparatus that can simultaneously perform heating and decompression can be preferably used, and a rotary evaporator is more preferably used.

[Water dispersion for inkjet recording]
The aqueous dispersion obtained by the method of the present invention can be used as an aqueous ink as it is.
The content of the colorant contained in the anionic colored particles used in the aqueous dispersion is preferably 2 to 35% by weight, more preferably 3 to 3% in the aqueous dispersion from the viewpoint of increasing the printing density of the aqueous dispersion. 30% by weight, more preferably 5 to 25% by weight.
The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The surface tension (20 ° C.) of the aqueous dispersion is preferably 30 to 70 mN / m, more preferably 35 to 65 mN / m.
The viscosity (20 ° C.) of 20% by weight (solid content) of the aqueous dispersion is preferably 1 to 12 mPa · s, more preferably 1 to 9 mPa · s, still more preferably 2 to 6 mPa · s, and particularly preferably 2 ˜5 mPa · s.

[Water-based ink for inkjet recording]
The water-based ink for ink-jet recording of the present invention contains the water dispersion obtained by the above production method, and further includes a wetting agent, a penetrating agent, a dispersant, a surfactant, a viscosity, which are usually used for water-based inks. An adjuster, an antifoaming agent, an antiseptic, an antifungal agent, an antirust agent and the like can be added.
As the wetting agent or penetrating agent, glycerin, triethylene glycol or the like is preferably used, and as the surfactant, 10 mol of ethylene oxide of 2,4,7,9-tetramethyl-5-decyne-4,7-diol is added. A thing etc. are used preferably.
The content of the colorant contained in the anionic colored particles in the aqueous ink of the present invention is preferably 1 to 25% by weight, more preferably 2 to 20% by weight in the aqueous ink from the viewpoint of increasing the printing density of the aqueous ink. %, More preferably 4 to 15% by weight, particularly preferably 5 to 12% by weight.
The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The preferred surface tension (20 ° C.) of the water-based ink of the present invention is 23 to 50 mN / m, more preferably 23 to 45 mN / m, and still more preferably 25 to 40 mN / m.
In order to maintain good ejection reliability, the viscosity (20 ° C.) of the aqueous ink of the present invention is preferably 2 to 20 mPa · s, more preferably 2.5 to 16 mPa · s, and still more preferably 2. 5 to 12 mPa · s.
The ink jet recording system to which the water-based ink of the present invention is applied is not particularly limited, but the effect of the present invention is particularly exerted in a thermal ink jet printer that discharges water-based ink by heating.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. The weight average molecular weight of the polymer, the average particle diameter of the anionic colored particles, the viscosity and pH of the aqueous dispersion and the like were measured by the following methods, and the ejection reliability of the water-based ink was evaluated by the following methods.
(1) Measurement of weight average molecular weight of anionic polymer Gel chromatography using a solution obtained by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide so as to have concentrations of 60 mmol / L and 50 mmol / L, respectively. It was measured using polystyrene as a standard substance by the method [GPC apparatus (HLC-8120GPC) manufactured by Tosoh Corporation, column (TSK-GEL, α-M × 2), manufactured by Tosoh Corporation, flow rate: 1 mL / min].
(2) Measurement of average particle diameter of anionic colored particles Measurement was performed using a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. A dispersion diluted with water so that the concentration of particles to be measured was 5 × 10 ⁻³ wt% was used. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and the number of integrations of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent.
(3) Measurement of viscosity The aqueous dispersion, the thickened product or the mixture was measured with an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80L) using a standard rotor (1 ° 34 '× R24) at a measurement temperature of 25 ° C Measurement was performed under the conditions of a measurement time of 1 minute. The highest number of rotations that can be measured was used. However, a maximum of 100 rpm was used.
(4) Measurement of pH It measured at 20 degreeC using the pH ion meter by Horiba, Ltd., brand name: F-23 (electrode for measurement # 6367-10D).

(5) Evaluation of ejection reliability The inside of a genuine black ink cartridge (ink tank BCI-321BK) of an inkjet printer (manufactured by Canon Inc., model number: PIXUS iP3600) was washed and dried, and this was used as an evaluation cartridge.
The cartridge for evaluation was filled with the water-based ink for inkjet recording obtained in Examples and Comparative Examples, sealed, and mounted on an inkjet printer (PIXUS iP3600). Next, using a personal computer connected to the printer, data was created and printed by PowerPoint (trade name, manufactured by Microsoft Corporation) so as to obtain a rectangular solid print with a width of 204 mm and a length of 275 mm. The printing conditions were paper type: plain paper, mode setting: standard, and plain paper (trade name: XEROX 4200, manufactured by XEROX) was used for printing.
By this printing method, the number of nozzles that failed to discharge on the 11th sheet after printing 10 sheets was visually counted from the printed paper. The smaller the number of non-ejection nozzles (the number of non-ejections), the better the ejection reliability.

Production Example 1 (Production of aqueous dispersion of colorant-containing polymer particles)
(1) Synthesis of anionic polymer (a) 32 parts of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent), (b) 88 parts of styrene (manufactured by Wako Pure Chemical Industries, Ltd., reagent), (c) styrene macromer (Toagosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6000, solid content concentration 50%) 20 parts (as solid content), (d) polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name) : BLEMMER PP-800, propylene oxide average addition mole number 13, terminal: hydroxyl group) 60 parts were mixed to prepare a monomer mixture.
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of 2-mercaptoethanol (polymerization chain transfer agent) and 10% of the monomer mixture were mixed and sufficiently substituted with nitrogen gas.
Meanwhile, in the dropping funnel, the remaining 90% of the monomer mixture, 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone, and an azo radical polymerization initiator (trade name: V-65, manufactured by Wako Pure Chemical Industries, Ltd.) , 2,2′-azobis (2,4-dimethylvaleronitrile)) 1.2 parts mixed solution, and the temperature of the monomer mixed solution in the reaction vessel was increased to 65 ° C. with stirring in a nitrogen atmosphere, The mixed solution in the dropping funnel was dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution in which 0.3 part of the polymerization initiator was dissolved in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours. Weight average molecular weight: 80000).

(2) Preparation of Aqueous Dispersion of Colorant-Containing Polymer Particles 25 parts of the polymer obtained by drying the polymer solution obtained in (1) above under reduced pressure is dissolved in 70 parts of methyl ethyl ketone, and 5N as a neutralizing agent therein. 9.3 parts of sodium hydroxide aqueous solution (neutralization degree 80%) and 230 parts of ion-exchanged water were added, and 75 parts of black pigment (carbon black, manufactured by Cabot Specialty Chemicals, Inc., trade name: Monarch 880) was further added. , TK Robomix (trade name) + TK homodisper type 2.5, and dispersed for 60 minutes at a rotational speed of 8000 / min. Further, with a microfluidizer (Microfluidics, trade name: M140K) at a pressure of 180 MPa 10-pass distributed processing.
After adding 250 parts of ion-exchanged water to the obtained dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was removed to obtain a dispersion (solid content 25%).
The obtained dispersion is put into a centrifugal settling tube 500PA bottle manufactured by Hitachi Koki Co., Ltd., and centrifuged at 12000 rpm using a cooling centrifuge “himacCR22G” manufactured by the same company and a rotor (R12A, radius 15.1 cm). An acceleration of 24300 G was applied, and this state was maintained for 30 minutes (12150 G · hr), and then the precipitated portion was removed to obtain an aqueous dispersion of colorant-containing polymer particles.
The obtained dispersion was filtered with a 25 mL needleless syringe (Terumo Corporation) attached with a 5 μm pore size filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation) and then ion exchanged. An aqueous dispersion of colorant-containing polymer particles having a solid content concentration of 20% (viscosity at 25 ° C., 4.2 mPa · s, average particle size of 105 nm) was obtained by adjusting with water. The obtained aqueous dispersion had a pH of 9.3.

Example 1 (Production of water dispersion for ink jet recording)
100 g of the aqueous dispersion of colorant-containing polymer particles obtained in Production Example 1 was placed in a 300 mL eggplant-shaped flask containing a stirrer (length: 3 cm). Next, 20 g of dry ice is placed in a four-necked separable flask and allowed to stand at room temperature to gradually sublimate dry ice to generate carbon dioxide gas. Carbon dioxide gas was introduced into the space of and stirred. Stirring was performed for 1 hour to obtain a paste-like product (thickened product).
The viscosity of the obtained paste at 25 ° C. was 300 mPa · s (step (I)).
50 g of ion-exchanged water was added to and mixed with the eggplant-shaped flask containing the paste. The pH of the mixture at this time was 5.8 (step (II)).
An eggplant-shaped flask was attached to a rotary evaporator, the pressure was reduced to 10.3 kPa in absolute pressure, and further heated to 60 ° C. in a water bath to remove carbon dioxide. The pH of the obtained mixture was 8.4 (step (IV)).
The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name: M-110EH, manufactured by Microfluidics) at a pressure of 150 MPa (step (III)).
Ion exchange water was added to the obtained dispersion to adjust the solid content concentration to 20%, and the mixture was filtered with a syringe equipped with the filter to obtain an aqueous dispersion for ink jet recording having a solid content concentration of 20%. .

Example 2 (Production of water dispersion for inkjet recording)
An aqueous dispersion for ink jet recording having a solid content concentration of 20% was obtained in the same manner as in Example 1 except that carbon dioxide gas was introduced and stirred for 3 hours in Step (I) of Example 1. The viscosity of the paste and the pH of the mixture are as shown in Table 1.

Example 3 (Production of water dispersion for inkjet recording)
An aqueous dispersion for inkjet recording having a solid content concentration of 20% was obtained in the same manner as in Example 1 except that carbon dioxide gas was introduced and stirred for 30 minutes in the step (I) of Example 1. The viscosity of the paste and the pH of the mixture are as shown in Table 1.

Example 4 (Production of water dispersion for inkjet recording)
An aqueous dispersion for inkjet recording having a solid content concentration of 20% was obtained in the same manner as in Example 1 except that carbon dioxide gas was introduced and stirred for 4 hours in Step (I) of Example 1. The viscosity of the paste and the pH of the mixture are as shown in Table 1.

Comparative Example 1 (Production of water dispersion for inkjet recording)
100 g of the aqueous dispersion of colorant-containing polymer particles obtained in Production Example 1 was placed in a 300 mL eggplant-shaped flask containing a stirrer (length: 3 cm). Next, 0.1 g of concentrated hydrochloric acid was placed in a 50 mL eggplant type flask equipped with a three-way tube connected with a silicone tube, and the eggplant type flask was heated in a 50 ° C. warm bath to gradually generate hydrogen chloride gas. The hydrogen chloride gas was introduced into the space portion of the eggplant-shaped flask with a silicone tube and stirred. Stirring was performed for 1 hour to obtain a paste (Step (I)). Subsequent steps were performed in the same manner as in Example 1 to obtain an aqueous dispersion for inkjet recording having a solid content concentration of 20%. The viscosity of the paste and the pH of the mixture are as shown in Table 1.

Comparative Example 2 (Production of water dispersion for inkjet recording)
100 g of the aqueous dispersion of colorant-containing polymer particles obtained in Production Example 1 was placed in a 300 mL eggplant-shaped flask containing a stirrer (length: 3 cm). Next, 2 g of 1N hydrochloric acid aqueous solution was added while stirring the dispersion to obtain a paste.
The viscosity of the obtained paste at 25 ° C. was 380 m · s (step (I)).
50 g of ion-exchanged water was added to and mixed with the eggplant-shaped flask containing the paste. The pH of the mixture at this time was 5.8 (step (II)).
An eggplant-shaped flask was attached to a rotary evaporator, and the pressure was reduced to 10.3 kPa, and further heated to 60 ° C. in a water bath and treated for 60 minutes. The pH of the obtained mixture was 6.0 (step (IV)).
2 g of 1N aqueous sodium hydroxide solution was added to the resulting mixture, and the mixture was stirred with a rotary evaporator to lower the viscosity of the mixture, and then subjected to 5-pass dispersion treatment at a pressure of 150 M with a microfluidizer (M-110EH). (Step (III).

Example 5 (Production of water-based ink)
25 parts of the aqueous dispersion obtained in Example 1, 15 parts of glycerin, 7 parts of triethylene glycol, acetylenol E100 (manufactured by Kawaken Fine Chemical Co., Ltd., 2,4,7,9-tetramethyl-5-decyne-4, 0.5 parts of 7-diol ethylene oxide adduct) and 52.5 parts of ion-exchanged water were mixed by stirring with a magnetic stirrer, and a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, A water-based ink was obtained by filtration through a needleless syringe with a capacity of 25 mL equipped with Fujifilm Corporation.
Table 1 shows the evaluation results of the ejection reliability of the obtained water-based ink.

Examples 6 to 8 and Comparative Examples 3 to 4 (Production of water-based ink)
In Example 5, in place of the aqueous dispersion obtained in Example 1, as shown in Table 1, the inkjet recording water dispersion obtained in Examples 2 to 4 and Comparative Examples 1 and 2 was used. Was the same as Example 5 to obtain a water-based ink. The results are shown in Table 1.
Comparative Example 5 (Production of water-based ink)
In Example 5, instead of the aqueous dispersion obtained in Example 1, as shown in Table 1, Example 5 was used except that the aqueous dispersion of the colorant-containing polymer particles obtained in Production Example 1 was used. In the same manner, a water-based ink was obtained. The results are shown in Table 1.

  From Table 1, it can be seen that the aqueous inks of Examples 5 to 8 are superior in ejection reliability to the aqueous inks of Comparative Examples 3 to 5.

Claims (7)

The manufacturing method of the aqueous dispersion for inkjet recording which has the following process (I)-(III).
Step (I): An aqueous dispersion containing anionic colored particles having a viscosity (A) at 25 ° C. of 1 to 50 mPa · s and carbon dioxide gas are mixed, and the viscosity (B) at 25 ° C. is 100 mPa. -Step of obtaining a thickened product that is s or more Step (II): Step of mixing the thickened product obtained in Step (I) and water Step (III): Dispersing the mixture obtained in Step (II) Process to process The manufacturing method of the water dispersion for inkjet recording of Claim 1 which performs the following process (IV) between process (II) and process (III).
Step (IV): A step of removing carbon dioxide gas from the mixture obtained in Step (II) and raising the pH by 0.1 or more.   The manufacturing method of the water dispersion for inkjet recording of Claim 1 or 2 whose viscosity (B) is 20 times or more with respect to a viscosity (A).   The method for producing an aqueous dispersion for inkjet recording according to any one of claims 1 to 3, wherein the colorant contained in the anionic colored particles is a pigment.   The method for producing an aqueous dispersion for inkjet recording according to any one of claims 1 to 4, wherein the anionic colored particles are anionic polymer particles containing a colorant.   The method for producing an aqueous dispersion for inkjet recording according to any one of claims 1 to 5, wherein in step (I), the pH of the aqueous dispersion is lowered by 0.5 to 6.0 by mixing carbon dioxide gas. .   A water-based ink for ink-jet recording, comprising the water dispersion obtained by the production method according to claim 1.