JP2010189487A - Method for producing aqueous dispersion for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aqueous pigment dispersion for inkjet recording which dispersion is excellent in filterability because of less coarse particles and also excellent in storage stability, and to provide an aqueous ink for inkjet recording that contains the aqueous dispersion produced by the method and is excellent in storage stability. <P>SOLUTION: The method for producing the aqueous dispersion for inkjet recording includes: a step (I) of subjecting a mixture containing a polymer having a salt-forming group, a neutralizer in such an amount that the neutralization degree of the salt-forming group of the polymer is 10-70 mol%, water and an organic solvent having a weight ratio of water to the organic solvent (water/organic solvent) of 1-3, and a pigment to a dispersion treatment to obtain a dispersion (1); a step (II) of adding a neutralizer and water to the resultant dispersion (1) to increase the neutralization degree of the salt-forming group of the polymer and increase the weight ratio of (water to the organic solvent) to obtain a dispersion (2) having a neutralization degree of the salt-forming group of the polymer of 50-100 mol% and a weight ratio of (water to the organic solvent) of > 3 and ≤20; and a step (III) of subjecting the resultant dispersion (2) to dispersion treatment to obtain a dispersion (3). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them.
Until now, electrophotographic printers have been generally used in offices and the like. However, the ink jet printer is energy saving because it does not perform heat fixing, and it is good for the environment by using water as a solvent, and the weather resistance and water resistance equivalent to those of electrophotography are obtained by using a pigment as a colorant. Therefore, an ink jet printer equipped with a water-based pigment ink has recently been used for office use.

In Patent Document 1, a water-insoluble polymer having a salt-forming group, an organic pigment dispersion, which can reduce the particle size of a pigment at the time of pigment dispersion and obtain a printed matter having excellent glossiness, is provided. A method for producing an aqueous pigment dispersion in which an emulsion composition containing a solvent, a neutralizing agent and water and a pigment are mixed and dispersed under a condition where the weight ratio of (organic solvent / water) is 0.1 to 0.9. Is disclosed.
Patent Document 2 contains a pigment, a polymer having a salt-forming group, a neutralizing agent, an organic solvent, and water for the purpose of obtaining a water-based pigment ink having a small average particle size and excellent filterability and gloss. A method for producing an aqueous dispersion of a pigment in which a mixture having a solid content concentration of 50 to 80% by weight is kneaded and diluted by adding water and / or an organic solvent is disclosed.
Patent Document 3 discloses a pigment in which water is mixed with a mixture of an organic solvent solution of a polymer and a pigment, and the dispersion treatment is performed, in order to obtain a water-based ink that has excellent water resistance and dispersion stability and does not have a printed matter. A method for producing a water-based ink containing polymer particles is disclosed.

JP 2005-188775 A Japanese Patent Laid-Open No. 2004-131697 JP 2001-247800 A

Inkjet recording pigment aqueous dispersions and water-based inks are usually produced by pulverizing and dispersing pigments with a size of several tens to several hundreds of microns in water to atomize them to several tens to several hundreds of nanometers. However, the particle diameter is still distributed, and coarse pigment particles having a size of several microns remain, causing clogging of the ink discharge nozzles. For this reason, measures are taken such as filtering many times at the time of manufacture and attaching a filter to the ink flow path of the printer. However, the filtration operation at the time of production greatly reduces the productivity. On the other hand, even if the filter is installed in the printer, pressure fluctuations at the nozzles occur, and this causes a failure in accurate printing.
The present invention relates to a method for producing a pigment aqueous dispersion for ink jet recording having few coarse particles and excellent filterability, and an aqueous ink for ink jet recording excellent in storage stability containing the aqueous dispersion obtained by the method. The issue is to provide.

The present inventor changes the neutralization degree of the polymer as a dispersant and the weight ratio of (organic solvent / water) and controls them to an appropriate range in the process of dispersing the pigment in the production of the aqueous dispersion for inkjet recording. Thus, it has been found that the above problems can be solved.
That is, the present invention provides the following [1] and [2].
[1] A method for producing an aqueous dispersion for inkjet recording, comprising the following steps (I) to (III).
Step (I): a polymer containing a salt-forming group, a neutralizing agent in such an amount that the degree of neutralization of the salt-forming group of the polymer is 10 to 70 mol%, and the weight ratio of water to the organic solvent (water / organic solvent) Step of obtaining a dispersion (1) by subjecting a mixture containing water, an organic solvent, and a pigment, each of which is 1 to 3 to dispersion (1) Step (II): In the dispersion (1) obtained in Step (I), A neutralizing agent and water are added, the degree of neutralization of the salt-forming groups of the polymer is increased, the weight ratio of (water / organic solvent) is increased, and the degree of neutralization of the salt-forming groups of the polymer is 50 to 100 mol. Step of obtaining dispersion (2) in which the weight ratio of (water / organic solvent) exceeds 3 and is 20 or less Step (III): The dispersion obtained in Step (II) is subjected to dispersion treatment Step [2] for obtaining a dispersion: A water-based ink for ink-jet recording containing the water dispersion obtained by the method of [1] above.

  INDUSTRIAL APPLICABILITY According to the present invention, a method for producing a pigment aqueous dispersion for inkjet recording having few coarse particles and excellent filterability, and an aqueous system for inkjet recording excellent in storage stability containing the aqueous dispersion obtained by the method. Ink can be provided.

The method for producing an aqueous dispersion for inkjet recording of the present invention comprises the following steps (I) to (III).
Step (I): a polymer containing a salt-forming group, a neutralizing agent in such an amount that the degree of neutralization of the salt-forming group of the polymer is 10 to 70 mol%, and the weight ratio of water to the organic solvent (water / organic solvent) Step of obtaining a dispersion (1) by subjecting a mixture containing water, an organic solvent, and a pigment, each of which is 1 to 3 to dispersion (1) Step (II): In the dispersion (1) obtained in Step (I), A neutralizing agent and water are added, the degree of neutralization of the salt-forming groups of the polymer is increased, the weight ratio of (water / organic solvent) is increased, and the degree of neutralization of the salt-forming groups of the polymer is 50 to 100 mol. Step of obtaining dispersion (2) in which the weight ratio of (water / organic solvent) exceeds 3 and is 20 or less Step (III): The dispersion obtained in Step (II) is subjected to dispersion treatment Step of obtaining dispersion The components and steps used in the production method of the present invention will be described below.

<Polymer containing salt-forming group>
Examples of the polymer containing a salt-forming group used in the present invention include polyesters, polyurethanes, vinyl polymers obtained by addition polymerization of vinyl monomers, etc., but filterability and storage stability of aqueous dispersions and aqueous inks. In view of the above, a vinyl polymer is preferable, and a water-insoluble polymer is more preferable. Here, the water-insoluble polymer means that when 100 g of polymer solids equivalent is dried at 105 ° C. for 2 hours, reaches a constant weight, and then dissolved in 100 g of water at 25 ° C., the dissolved amount is 10 g or less, preferably It refers to a polymer that is 5 g or less, more preferably 1 g or less. When the polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the polymer is neutralized 100% with acetic acid or sodium hydroxide depending on the type.

[Vinyl polymer]
The vinyl polymer includes (a) a salt-forming group-containing monomer (hereinafter also referred to as “(a) component”), (b) a macromer (hereinafter also referred to as “(b) component”) and / or (c) a hydrophobic monomer. A vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to simply as “monomer mixture”) containing (hereinafter also referred to as “component (c)”) is preferable. This vinyl polymer has a structural unit derived from the component (a), a structural unit derived from the component (b) and / or a structural unit derived from the component (c). Especially, what contains all the structural unit derived from the structural unit derived from (a) component, the structural unit derived from (b) component, and the structural unit derived from (c) component is preferable.

[(A) salt-forming group-containing monomer]
The salt-forming group-containing monomer (a) is used from the viewpoint of improving the dispersibility of the resulting aqueous dispersion. It is considered that if the dispersibility of the aqueous dispersion increases, the filterability and storage stability of the aqueous dispersion and the water-based ink are improved. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group, and a carboxy group is particularly preferable.
Examples of the salt-forming group-containing monomer (a) include a cationic monomer and an anionic monomer.
Representative examples of the cationic monomer include amine-containing monomers and ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.

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, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, and the like. It is done.
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 aqueous dispersion.

[(B) Macromer]
(B) 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 is used from the viewpoint of increasing the affinity of the polymer for the pigment. If the affinity of the polymer for the pigment is increased, the dispersion stability of the aqueous dispersion is improved, and the filterability and storage stability of the aqueous dispersion and the water-based ink are considered to be improved. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and more preferably a methacryloyloxy group. The number average molecular weight is 500 to 100,000, preferably 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.
As the (b) macromer, a styrene macromer, an aromatic group-containing (meth) acrylate macromer, and a silicone macromer are preferable from the viewpoint of increasing the affinity of the polymer for the pigment.
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. In the case of a copolymer, the content of the styrenic monomer is preferably 50% by weight or more, and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the pigment. Other monomers to be copolymerized include aromatic group-containing (meth) acrylates or acrylonitrile. Examples of the styrenic monomer include styrene and 2-methylstyrene.
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 aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. In the case of a copolymer, the content of the aromatic group-containing (meth) acrylate is preferably 50% by weight or more and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the pigment. The aromatic group-containing (meth) acrylate is a (meth) acrylate having an arylalkyl group having 7 to 12 carbon atoms or an aryl group, which may have a substituent containing a hetero atom, such as benzyl (meth). Examples include acrylate and phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate is preferred. Examples of other monomers to be copolymerized include styrene monomers and acrylonitrile.
The macromer may be a silicone macromer, and examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.

[(C) Hydrophobic monomer]
(C) The hydrophobic monomer is used from the viewpoint of increasing the affinity of the polymer for the pigment. 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.
Examples of the aromatic group-containing monomer include styrene monomers and aromatic group-containing (meth) acrylates. As the styrenic monomer, styrene and 2-methylstyrene are preferable, and as the aromatic group-containing (meth) acrylate, benzyl (meth) acrylate and phenoxyethyl (meth) acrylate are preferable.

[(D) Nonionic monomer]
The monomer mixture may further contain (d) a nonionic monomer (hereinafter also referred to as “component (d)”).
(D) As a component, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethyleneglycol (n = 2-30, n shows the average addition mole number of an oxyalkylene group. The same hereafter). (Meth) acrylate, polypropylene glycol (n = 2 to 30) (meth) acrylate, poly (ethylene glycol (n = 1 to 15) / propylene glycol (n = 1 to 15)) (meth) acrylate, methoxypolyethylene glycol ( 1-30) (meth) acrylate, methoxypolytetramethylene glycol (1-30) (meth) acrylate, ethoxypolyethylene glycol (1-30) (meth) acrylate, octoxypolyethylene glycol (1-30) (meth) acrylate , Polyethylene grease (1-30) (meth) acrylate 2-ethylhexyl ether, (iso) propoxypolyethylene glycol (1-30) (meth) acrylate, butoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1 -30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (1-30, ethylene glycol: 1 to 29 therein) (meth) acrylate, and the like.

Specific examples of the commercially available component (d) include NK Esters M-40G, 90G, and 230G from Shin-Nakamura Chemical Co., Ltd., Bremer PE-90, 200, and 350 from Nippon Oil & Fats Co., Ltd. PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800, 50PEP-300, 50POEP-800B, 43PAPE600B, etc. .
The components (a) to (d) can be used alone or in admixture of two or more.

At the time of vinyl polymer production, the content of the components (a) to (d) in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or derived from the components (a) to (d) in the vinyl polymer The content of the structural unit is as follows.
The content of the component (a) is preferably 3 to 40% by weight, more preferably 4 to 30% by weight, and further preferably 5 to 25% by weight from the viewpoint of improving the dispersibility of the aqueous dispersion.
The content of the component (b) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, from the viewpoint of increasing the affinity of the polymer for the pigment.
The content of the component (c) is preferably 5 to 98% by weight, more preferably 10 to 60% by weight, from the viewpoint of increasing the affinity of the polymer for the pigment.
The content of the component (d) is preferably 5 to 60% by weight, more preferably 17 to 50% by weight, from the viewpoint of enhancing the dispersibility of the aqueous dispersion.

[Production of polymer]
The polymer used in the present invention is produced by copolymerizing a monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is preferably a polar organic solvent. When the polar organic solvent is miscible with water, it can be used by mixing with water. As the polar organic solvent, for example, aliphatic alcohols having 1 to 3 carbon atoms; ketones having 3 to 8 carbon atoms; esters such as ethyl acetate; or a mixed solvent of one or more of these with water.
In the polymerization, a known radical polymerization initiator such as an azo compound or an organic peroxide can be used. The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide may be further added.
Although the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, solvent, etc. used, it cannot be generally stated, but usually the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C. The polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the polymer produced by a known method can be isolated. Further, the obtained polymer can be purified by removing the unreacted monomer and the like by re-precipitation by membrane separation, chromatographic method, extraction method or the like.
The weight average molecular weight of the polymer used in the present invention is preferably 5,000 to 500,000, more preferably 10,000 to 400,000, and 10,000 to 300,000 from the viewpoint of the storage stability of the aqueous dispersion and the aqueous ink. Further preferred is 20,000 to 300,000. In addition, the weight average molecular weight of a polymer can be measured by the method as described in an Example.

<Neutralizing agent>
As the neutralizing agent used in the steps (I) and (II) of the present invention, an acid or a base can be used depending on the kind of the salt-forming group in the polymer. For example, hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid and other acids, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine , Bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.

<Organic solvent>
The organic solvent used in the steps (I) and (II) of the present invention is preferably an organic solvent having a solubility in 100 g of water of 5 g or more at 20 ° C. from the viewpoint of dispersing the pigment while suppressing the formation of coarse particles. The thing of 10 g or more is more preferable. More specifically, the dissolution amount is preferably 5 to 80 g, more preferably 10 to 50 g. Examples thereof include aliphatic alcohols having 1 to 5 carbon atoms such as methanol, ethanol and propanol; ketones having 3 to 8 carbon atoms such as acetone and methyl ethyl ketone; esters such as ethyl acetate and the like. Of these, methyl ethyl ketone and methyl isobutyl ketone are preferred.

<Pigment>
The pigment used in the present invention 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. Of these, carbon black is preferred particularly for black aqueous inks. 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.
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. Examples of extender pigments include silica, calcium carbonate, and talc.
As the pigment, a so-called self-dispersing pigment can also be used. The self-dispersing pigment is an aqueous medium without using a surfactant or a resin by binding one or more of an anionic hydrophilic group or a cationic hydrophilic group to the surface of the pigment directly or through another atomic group. Means a pigment that is dispersible. Here, the anionic hydrophilic group is particularly preferably a carboxyl group (—COOM ¹ ) or a sulfonic acid group (—SO ₃ M ¹ ) (wherein M ¹ is a hydrogen atom, an alkali metal, or ammonium), As the cationic hydrophilic group, a quaternary ammonium group is preferable.
The above pigments can be used alone or in admixture of two or more.

<Manufacture of water dispersion for inkjet recording>
The aqueous dispersion for inkjet recording of the present invention is produced by a method having the following steps (I) to (III).
Step (I): a polymer containing a salt-forming group, a neutralizing agent in such an amount that the degree of neutralization of the salt-forming group of the polymer is 10 to 70 mol%, and the weight ratio of water to the organic solvent (water / organic solvent) Step of obtaining a dispersion (1) by subjecting a mixture containing water, an organic solvent, and a pigment, each of which is 1 to 3 to dispersion (1) Step (II): In the dispersion (1) obtained in Step (I), A neutralizing agent and water are added, the degree of neutralization of the salt-forming groups of the polymer is increased, the weight ratio of (water / organic solvent) is increased, and the degree of neutralization of the salt-forming groups of the polymer is 50 to 100 mol. Step of obtaining dispersion (2) in which the weight ratio of (water / organic solvent) exceeds 3 and is 20 or less Step (III): The dispersion obtained in Step (II) is subjected to dispersion treatment Step of obtaining dispersion (3)

In the present invention, by performing all of the steps (I) to (III), the generation of coarse particles is suppressed, and an aqueous dispersion excellent in filterability and storage stability can be obtained. The reason for this is not clear, but can be considered as follows.
In step (I), a large amount of pigment, polymer and organic solvent are contained, and the polymer is uniformly and firmly adhered to the pigment by dispersing the polymer under a low neutralization condition. Further, in steps (II) and (III ), By increasing the weight ratio of water to organic solvent (water / organic solvent) and redispersing under the condition that the degree of neutralization of the polymer is increased, the ionic repulsion between the polymers becomes stronger and finer. In addition, it is considered that a stable aqueous dispersion can be obtained.

[Process (I)]
Step (I) comprises a polymer containing a salt-forming group, a neutralizing agent in an amount such that the degree of neutralization of the salt-forming group of the polymer is 10 to 70 mol%, and the weight ratio of water to the organic solvent (water / organic solvent ) Is a step of obtaining a dispersion (1) by subjecting a mixture containing water, an organic solvent, and a pigment, each having 1 to 3 to a dispersion treatment.
In step (I), first, a polymer containing a salt-forming group is dissolved in an organic solvent, and then a neutralizing agent, water and a pigment are added to the obtained organic solvent solution and mixed to obtain an oil-in-water dispersion. The method of obtaining (1) is preferred.
In the dispersion (1) obtained in the step (I), the total amount of the pigment is preferably 5 to 50% by weight, and more preferably 10 to 40% by weight. The polymer is preferably 2 to 40% by weight, more preferably 3 to 20% by weight in the dispersion (1).
The addition amount of the neutralizing agent is such that the degree of neutralization of the salt forming group of the polymer is 10 to 70 mol% from the viewpoint of improving the dispersibility of the pigment while suppressing the formation of coarse pigment particles. The amount is preferably 20 to 70 mol%, more preferably 40 to 65 mol%, still more preferably 45 to 55 mol%.
The organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the water is preferably 10 to 70% by weight and more preferably 20 to 70% by weight.
However, the weight ratio of (water / organic solvent) is adjusted to be 1 to 3 from the viewpoint of pigment dispersibility. The weight ratio of (water / organic solvent) is preferably 1.6 to 3.0, more preferably 1.4 to 3.0, and still more preferably 2.0 to 3.0.
In the dispersion treatment of this step, it is preferable to carry out until the particle size after the treatment is 500 nm or less, more preferably 300 nm, and even more preferably 250 nm or less.

There is no restriction | limiting in particular in the dispersion method in process (I). The dispersion may be performed only once. However, after the preliminary dispersion, the shear dispersion is further applied to perform the main dispersion to control the average particle diameter of the pigment particles to a desired particle diameter. The temperature in the dispersion in the step (I) 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.
When pre-dispersing the mixture comprising the above components, commonly used mixing and stirring devices such as anchor blades, disper blades, etc., specific examples include Ultra Disper, Desperm (Asada Tekko Co., Ltd., trade name), Milder ( Ebara Manufacturing Co., Ltd., Taiheiyo Kiko Co., Ltd., trade name), TK Robotics (homodisper), TK homomixer, TK pipeline mixer, TK homojetter, TK homomic line flow, Philmix Etc.) are preferred.

  Examples of means for applying the shear stress of the dispersion include a kneader such as an atmospheric pressure kneader (manufactured by Moriyama), a kneader such as a roll mill and an extruder, and a homovalve type typified by a high pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name). High pressure homogenizer, microfluidizer (trade name), nanomizer (Yoshida Kikai Kogyo Co., Ltd., trade name), optimizer, starburst (Sugino Machine Co., trade name), etc. Examples thereof include media type dispersing machines such as a shaker and a bead mill. Commercially available media-type dispersers include Ultra Apex Mill (trade name, manufactured by Kotobuki Industries Co., Ltd.), Picomill (trade name, manufactured by Asada Tekko Co., Ltd.), Dino Mill (trade name, manufactured by Shinmaru Enterprises Co., Ltd.), etc. Is mentioned. A plurality of these devices can be combined.

[Process (II)]
In step (II), a neutralizing agent and water are added to the dispersion (1) obtained in step (I) to increase the degree of neutralization of the salt-forming groups of the polymer, and (water / organic solvent) By increasing the weight ratio, a dispersion (2) is obtained in which the degree of neutralization of the salt-forming groups of the polymer is 50 to 100 mol%, and the weight ratio of (water / organic solvent) is more than 3 and 20 or less. It is a process.
In step (II), a neutralizing agent and water are added, but these may be added simultaneously, or either may be added first. In addition, batch addition or divided addition divided into a plurality of times may be used.
In step (II), an organic solvent may be added in addition to the neutralizing agent and water in order to adjust the degree of neutralization and the weight ratio of (water / organic solvent) to predetermined values. However, the weight ratio of (water / organic solvent) is set higher than the condition of step (I).
The addition amount of the neutralizing agent in the step (II) is such that the degree of neutralization of the salt forming groups of the polymer is 50 to 100 mol% from the viewpoint of improving the dispersibility of the pigment while suppressing the formation of coarse pigment particles. The amount is preferably 60 to 100 mol%, more preferably 60 to 70 mol%, and still more preferably 62 to 66 mol%.

The amount of the organic solvent contained in the dispersion (2) obtained in the step (II) is preferably 5 to 20% by weight and more preferably 5 to 18% by weight from the viewpoint of suppressing the formation of the pigment coarse particles.
The amount of water contained in the dispersion (2) is preferably 60 to 75% by weight, more preferably 62 to 75% by weight, from the viewpoint of suppressing the formation of coarse particles.
The weight ratio of (water / organic solvent) contained in the dispersion (2) is more than 3 from the viewpoint of efficiently dispersing in the next step (III) and suppressing the formation of coarse pigment particles. 20 or less, preferably 3.5 to 17, more preferably 3.8 to 16, and still more preferably 4.0 to 5.0.
The amount of water added in step (II) is relative to the total solid content concentration of the polymer containing the salt-forming group and the pigment (hereinafter also referred to as “total solid content concentration”) from the viewpoint of suppressing the formation of coarse pigment particles. The amount is preferably 2.5 to 5 times, and more preferably 3.5 to 4 times. Further, an organic solvent may be added, but the addition amount is preferably 0.1 to 1.5 times the total solid content concentration from the viewpoint of suppressing the formation of coarse pigment particles, and 0.2 An amount of ~ 0.3 times is more preferable.
In the step (II), the total solid content concentration is decreased, and the polymer and pigment in the dispersion (2) with respect to the total solid content concentration of the polymer and pigment containing the salt-forming group in the dispersion (1) Is preferably 0.20 to 0.99, more preferably 0.30 to 0.95, and even more preferably 0.70 to 0.90.
Thus, by reducing the solid content concentration from step (I) to step (II) so that the solid content concentration ratio is 0.20 to 0.99, in the next step (III), strong shear It is possible to efficiently disperse the stress and suppress the generation of coarse particles.
The adjustment of the weight ratio of water to the organic solvent (water / organic solvent) and the total solid content concentration can be performed by adding both water and the organic solvent as described above. It is preferable to add only.

[Process (III)]
Step (III) is a step of obtaining a water dispersion (3) by dispersing the dispersion (2) obtained in step (II).
The dispersion method in step (III) may be any of the dispersion methods described in the column of step (I), but it is preferable to disperse under a condition that gives a stronger shearing stress. Examples of the disperser preferably used include those exemplified in step (I), such as a kneader such as a roll mill, a kneader, and an extruder, a homovalve type high pressure homogenizer, a chamber type high pressure homogenizer, a media type disperser, and the like. Can be mentioned. A plurality of these devices can be combined. Among these, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment.
The dispersion 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.
In the dispersion treatment of step (III), it is preferable to carry out until the average particle size of the dispersion after the dispersion treatment is 400 nm or less, more preferably 250 nm, and further to 200 nm or less. preferable. Moreover, it is preferable to carry out until it becomes smaller than the average particle diameter after completion | finish of process (I), It is more preferable to carry out until the difference of the average particle diameter becomes 30 nm or more, It is still more preferable to carry out until it becomes 50 nm or more.

The dispersion (3) obtained after carrying out all the steps (I) to (III) can be used as it is or further by adding an organic solvent or the like to obtain a water-based ink. Removal, centrifugation, filtration and the like may be performed.
As a method for removing the organic solvent, a known method is used, and it is preferable that the organic solvent in the obtained aqueous dispersion is substantially removed. However, it remains as long as the object of the present invention is not impaired. May be. The amount of the residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
In the obtained aqueous dispersion, the pigment and polymer are dispersed in water as a main medium, and the surface of the pigment is preferably coated with the polymer adsorbed or adhered.
Here, as a form of dispersion when the polymer is water-insoluble, for example, (i) the water-insoluble polymer adheres to the surface of the pigment to form particles including a plurality of pigment particles and is dispersed. Form, (ii) Form in which the pigment is encapsulated and dispersed in the water-insoluble polymer, (iii) Form in which the pigment is exposed and dispersed on the surface of the water-insoluble polymer particle, (iv) Water-insoluble on the surface of the pigment Examples of the mixed form include a form in which the polymer is partially adhered and dispersed.

<Water dispersion for inkjet recording>
The content of each component in the inkjet recording water dispersion is as follows from the viewpoint of storage stability.
The total pigment content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 1 to 10% by weight, and the polymer content is preferably 0.5 to 20%. % By weight, more preferably 1-15% by weight, still more preferably 1-10% by weight.
The total content of pigment and polymer is preferably 1 to 30% by weight, more preferably 2 to 25% by weight.
The water content is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.
The average particle size of the dispersed polymer particles in the aqueous dispersion is preferably 40 to 400 nm, more preferably 50 to 300 nm, and still more preferably 60 to 200 nm, from the viewpoints of filterability and storage stability. The average particle size is measured by the method described in the examples.
The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s in order to obtain a good viscosity when used as a water-based ink. The viscosity of the aqueous dispersion is measured using an E-type viscometer under the conditions of a measurement temperature of 20 ° C., a measurement time of 1 minute, a rotation speed of 100 rpm, and a standard rotor (1 ° 34 ′ × R24).
The preferable surface tension (20 ° C.) of the aqueous dispersion of the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m.

<Water-based ink for inkjet recording>
The aqueous ink of the present invention contains the aqueous dispersion of the present invention, and additives such as a wetting agent, a dispersant, an antifoaming agent, an antifungal agent, and a chelating agent can be added as necessary. There is no restriction | limiting in particular in the mixing method of these additives.
The content of each component in the water-based ink for inkjet recording is as follows from the viewpoint of storage stability.
The total pigment content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 1 to 10% by weight, and the polymer content is preferably 0.5 to 20%. % By weight, more preferably 1-15% by weight, still more preferably 1-10% by weight.
The total content of pigment and polymer is preferably 1 to 30% by weight, more preferably 2 to 25% by weight.
The water content is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.
The average particle size of the dispersed polymer particles in the water-based ink is preferably 40 to 400 nm, more preferably 50 to 300 nm, and still more preferably 60 to 200 nm, from the viewpoints of filterability and storage stability. In addition, an average particle diameter is measured by the method as described in an Example.
The viscosity (20 ° C.) of the water-based ink is preferably 2 to 12 mPa · s, more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties. The viscosity of the water-based ink is measured using an E-type viscometer under the conditions of a measurement temperature of 20 ° C., a measurement time of 1 minute, a rotation speed of 100 rpm, and a standard rotor (1 ° 34 ′ × R24).
The preferred surface tension (20 ° C.) of the aqueous ink of the present invention is preferably 25 to 50 mN / m, more preferably 27 to 45 mN / m, and the pH is preferably 4 to 10.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is suitable for a piezo ink jet printer suitable for discharging a dispersion containing particles such as dispersible colorants such as pigments.

In the following production examples, preparation examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. In addition, the weight average molecular weight of the polymer is measured by the following method, the average particle size is measured after step (I) and step (III), the number of coarse particles is measured and the filterability is evaluated for the aqueous dispersion. The water-based ink was evaluated for filterability and storage stability.
(1) Measurement of polymer weight average molecular weight Gel chromatography method using a solution obtained by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide so as to have a concentration of 60 mmol / L and 50 mmol / L, respectively. Measurement was performed using polystyrene as a standard substance with a GPC apparatus (HLC-8120GPC) manufactured by Tosoh Corporation, a column (TSK-GEL, α-M × 2) manufactured by Tosoh Corporation, and a flow rate of 1 mL / min].

(2) Measurement of the number of coarse particles A solution of 0.5 ml of water dispersion diluted to 5 ml with pure water was prepared, and single particle optical detection method (SPOS) was performed using ACCUSIZER manufactured by PARTICLE SIZING SYSTEMS at a measurement temperature of 25 ° C. And measured. The number of particles having a particle diameter of 0.51 μm or more contained in the aqueous dispersion was defined as coarse particles. The smaller the number of coarse particles, the better.
Coarse particle number ratio (%) = ([number of particles of 0.8 μm or more] / [number of all particles]) × 100
(3) Water dispersion filterability and ink filterability A needleless syringe of 25 mL capacity equipped with a 5 μm membrane filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Sartorius, trade name: Minisart) [Terumo Corporation The amount of liquid passing until one filter was clogged was measured and evaluated based on the following evaluation criteria.
〔Evaluation criteria〕
A: The flow rate is 100 mL or more B: The flow rate is 50 mL or more and less than 100 mL C: The flow rate is 10 mL or more and less than 50 mL D: The flow rate is less than 10 mL (4) Storage stability of water-based ink Water-based ink is made of glass The viscosity after filling in an airtight container and storing at 70 ° C. for 30 days was measured at 20 ° C. using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80L), and the rate of viscosity change was determined from the following formula. The smaller the absolute value of the change rate, the better the storage stability.
Storage stability (Viscosity change rate) (%) = (([viscosity after storage] − [viscosity before storage]) / [viscosity before storage]) × 100
(5) Measurement of average particle diameter after step (I) and step (III) Measurement was performed using ELS-8000 (cumulant analysis) of a laser particle analysis system of Otsuka Electronics Co., Ltd. A dispersion diluted with water so that the solid content concentration to be measured was 3 × 10 ^{−3 to} 7 × 10 ⁻³ wt% was used. The measurement conditions were a temperature of 25 ° C., an angle between the incident light and the detector of 90 °, and an integration count of 200. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. In addition, Uniform Microparticles (average particle size: 204 nm) manufactured by Seradyn was used as a standard substance.

Production Example 1 (Production of polymer (A))
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.2 part of 2-mercaptoethanol, and (a) 16 parts of methacrylic acid (Mitsubishi Gas Chemical Co., Ltd., trade name: GE-110), (b) styrene macromer ( Toa Gosei Co., Ltd., trade name: AS-6S, number average molecular weight 6,000) 15 parts, (c) n-butyl methacrylate (Mitsubishi Gas Chemical Co., Ltd., trade name: GE-310), 10 parts, (c) styrene 34 parts of monomer (Nippon Steel Chemical Co., Ltd.) and 25 parts of (d) octoxy polyethylene glycol polypropylene glycol monomethacrylate (EO chain 8 mol, PO chain 6 mol, manufactured by NOF Corporation, trade name: BLEMMER 50POEP-800B) 10% of each was added and mixed, and nitrogen gas substitution was sufficiently performed. It was obtained.
On the other hand, the remaining 90% of each of the above monomers was charged in a dropping funnel, and then 0.27 part of 2-mercaptoethanol, 60 parts of methyl ethyl ketone and 2,2′-azobis (2,4-dimethylvaleronitrile) 1. 2 parts were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a dropped monomer solution.
Under a nitrogen atmosphere, the initially charged monomer solution in the reaction vessel was heated to 75 ° C. while stirring, and the dropped monomer solution in the dropping funnel was gradually dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the temperature of the reaction solution was maintained at 75 ° C. for 2 hours, and then a solution in which 0.3 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in 5 parts of methyl ethyl ketone was reacted. In addition to the solution, the mixture was further aged at 75 ° C. for 2 hours and 85 ° C. for 2 hours to complete the reaction, and a polymer solution was obtained.
The obtained polymer solution was dried at 105 ° C. under reduced pressure for 2 hours, and the polymer (A) was isolated by removing methyl ethyl ketone. The weight average molecular weight of the obtained polymer was 124,000.

Production Example 2 (Production of polymer (B))
As monomers, (a) 14 parts of methacrylic acid (trade name: GE-110), (b) 15 parts of styrene macromer (AS-6S), (c) 46 parts of styrene monomer, and (d) polypropylene glycol monomethacrylate (PO) 8 to 10 mol of chain, manufactured by Nippon Oil & Fats Co., Ltd., trade name: Blemmer PP-500, 20 parts, (d) methoxypolyethylene glycol monomethacrylate (23 mol of EO chain, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK Ester M-230G) Polymer (B) was obtained in the same manner as in Production Example 1, except that 5 parts were used. The weight average molecular weight of the obtained polymer was 80,000.

Example 1 (Preparation of water dispersion (1) for inkjet recording)
[Process (I)]
A solution obtained by dissolving 20.0 parts of the polymer (A) obtained in Production Example 1 in 20.0 parts of methyl ethyl ketone in an ultra disper (manufactured by Asada Tekko Co., Ltd.), which is a high-speed stirring and mixing apparatus, is a 5N sodium hydroxide aqueous solution ( Sodium hydroxide concentration 16.8%) 4.4 parts (polymerization carboxy group neutralization degree 50 mol%) and ion-exchanged water 26.6 parts (weight ratio of water to organic solvent (water / organic solvent) 1 5) was added, and the disper blade was rotated 2000 times per minute and treated for 30 minutes. After the obtained mixture was charged into an atmospheric pressure kneader (manufactured by Moriyama Co., Ltd.), 80.0 parts (solid content concentration 67%) of magenta organic pigment (manufactured by DIC Corporation, trade name: FASTOGEN Super Magenta RG) was added. The kneader was covered and sealed, and 1 ° C. cooling water was passed through the jacket and kneaded at 25 ° C. for 2 hours to obtain a dispersion (1-1).
The degree of neutralization of the carboxy group of the polymer with sodium hydroxide (NaOH) was 50 mol% as a result of calculation as follows.
Number of moles of NaOH = 4.4 / 40 × 0.168 = 0.185 mole Number of moles of carboxy group of polymer = 20 × 0.16 / 86 = 0.0372 mole degree of neutralization = 0.0185 / 0.0372 × 100 = 50 (mol%)
However, the molecular weight of NaOH is 40, and the molecular weight of methacrylic acid is 86.
The weight ratio of water to the organic solvent (water / organic solvent) was {4.4 × (1−0.168) +26.6} /20=1.5.
The solid content concentration was (20 + 80 + 4.4 × 0.168) / (20 + 20 + 80 + 4.4 + 26.6) × 100 = 67 (% by weight).

[Process (II)]
To the dispersion (1-1) obtained in the step (I), 222.1 parts of ion-exchanged water was added, and the disperse blade was rotated 8000 per minute and treated at 15 ° C. for 1 hour. Furthermore, 1.0 part of 5N sodium hydroxide aqueous solution and 46.3 parts of ion-exchanged water were added, and the mixture was charged into TK Robotics (Homodisper) manufactured by Primix Co., Ltd., and the disper blade was rotated 8000 per minute at 15 ° C. The dispersion (1-2) was obtained by treating for 1 hour.
The degree of neutralization of the carboxy group of the polymer in the obtained dispersion (1-2) was 61 mol% as a result of calculation as follows.
Number of moles of NaOH = (4.4 + 1.0) /40×0.168=0.0227 mol Degree of neutralization = 0.0227 / 0.0372 × 100 = 61 (mol%)
The weight ratio of water to the organic solvent (water / organic solvent) was {(4.4 + 1.0) × (1−0.168) + 26.6 + 222.1 + 46.3} /20=15.0. .
The solid content concentration was {20 + 80 + (4.4 + 1.0) × 0.168} / (20 + 20 + 80 + 4.4 + 1.0 + 26.6 + 222.1 + 46.3) × 100 = 24 (% by weight).

[Process (III)]
Dispersion (1-2) obtained in step (II) was treated with a microfluidizer (trade name, manufactured by Microfluidics) for 20 passes at a pressure of 200 MPa to obtain dispersion (1-3).
[Post-treatment process]
To dispersion (1-3) obtained in step (III), 250 parts of ion-exchanged water is added and stirred, and then methyl ethyl ketone and a part of water are removed under reduced pressure at 60 ° C. to contain a pigment. An aqueous dispersion (1) for ink jet recording containing 20% by weight of polymer particles was obtained.

Comparative Example 1 (Preparation of Inkjet Recording Water Dispersion (2))
In Example 1, an inkjet recording water dispersion (2) was obtained in the same manner as in Example 1 except that the step (II) was changed as follows.
[Process (II)]
Dispersion (1-1) obtained in step (I) was charged with 269.2 parts of ion-exchanged water and charged into TK Robotics, manufactured by Primics Co., Ltd., and treated in the same manner as in Example 1 to obtain a dispersion (2- 2) was obtained. The degree of neutralization of the polymer in the obtained dispersion (2-2) was 50 mol%.
The weight ratio of water to the organic solvent (water / organic solvent) of the obtained dispersion (2-2) was [4.4 × (1−0.168) + 26.6 + 269.2] /20=15.0. Met.
The solid content concentration was (20 + 80 + 4.4 × 0.168) / (20 + 20 + 80 + 4.4 + 26.6 + 269.2) × 100 = 24 (% by weight).

Comparative Example 2 (Preparation of aqueous dispersion for ink jet recording (3))
In Example 1, an inkjet recording water dispersion (3) was obtained in the same manner as in Example 1 except that the steps (I) and (II) were changed as follows.
[Process (I)]
A solution obtained by dissolving 20.0 parts of the polymer (1) obtained in Production Example 1 in 20.0 parts of methyl ethyl ketone in Ultra Disper (manufactured by Asada Tekko Co., Ltd.), which is a high-speed stirring and mixing apparatus, 5N sodium hydroxide aqueous solution 4 .4 parts (neutralization degree of polymer carboxy group 50 mol%) and ion-exchanged water 295.3 parts (weight ratio of water to organic solvent (water / organic solvent) 15) were added, and the disperse blade was moved for 1 minute. And rotated for 2000 minutes. Next, 80.0 parts (FASTOGEN Super Magenta RG) of magenta organic pigment (FASTOGEN Super Magenta RG) was added and treated for 60 minutes to obtain Dispersion (3-1).
The weight ratio of water to organic solvent (water / organic solvent) was (4.4 × (1−0.168) +295.3) /20=15.0.
The solid content concentration was (20 + 80 + 4.4 × 0.168) / (20 + 20 + 80 + 4.4 + 295.3) × 100 = 24 (% by weight).
[Process (II)]
To the dispersion obtained in step (I), 1.0 part of 5N aqueous sodium hydroxide solution was added and charged into TK Robotics, manufactured by Primics Co., Ltd., and treated in the same manner as in Example 1 to prepare dispersion (3-2). Obtained. The degree of neutralization of the polymer in the obtained dispersion (3-2) was 61 mol%.
The weight ratio of water to the organic solvent (water / organic solvent) was [(4.4 + 1.0) × (1−0.168) +295.3] /20=15.0.
The solid content concentration was {20 + 80 + (4.4 + 1.0) × 0.168} / (20 + 20 + 80 + 4.4 + 1.0 + 295.3) × 100 = 24 (% by weight).

Comparative Example 3 (Preparation of water dispersion for inkjet recording (4))
In Example 1, an inkjet recording water dispersion (4) was obtained in the same manner as in Example 1 except that the step (II) was changed as follows.
[Process (II)]
To the dispersion (1-1) obtained in the step (I), 222.1 parts of ion-exchanged water was added, and the disperse blade was rotated 8000 per minute and treated at 15 ° C. for 1 hour. Further, after adding 8.9 parts of 5N sodium hydroxide aqueous solution and 40.0 parts of ion-exchanged water so that the solid content concentration becomes 24%, it was charged into TK Robotics manufactured by Primics Co., Ltd. The same treatment was performed to obtain Dispersion (4-2).
The degree of neutralization of the polymer in the obtained dispersion (4-2) was 150 mol% as a result of calculation as follows.
Number of moles of NaOH = (4.4 + 8.9) /40×0.168=0.0559 mole Degree of neutralization = 0.0559 / 0.0372 × 100 = 150 (mol%)
The weight ratio of water to organic solvent (water / organic solvent) was [(4.4 + 8.9) × (1−0.168) + 26.6 + 222.1 + 40.0] /20=15.0. It was.
The solid content concentration was {20 + 80 + (4.4 + 8.9) × 0.168} / (20 + 20 + 80 + 4.4 + 8.9 + 26.6 + 222.1 + 40.0) × 100 = 24 (% by weight).

Example 2 (Preparation of water dispersion for inkjet recording (5))
[Process (I)]
A solution prepared by dissolving 25.0 parts of the polymer (B) obtained in Production Example 2 in 73.4 parts of methyl ethyl ketone, 4.8 parts of a 5N aqueous sodium hydroxide solution (the neutralization degree of the carboxy group of the polymer is 50 mol%), and Add 209.5 parts of ion-exchanged water (weight ratio of (organic solvent / water) 1 / 2.9) and stir, then charge to TK Robotics (Homo Disper) manufactured by Primix Co., Ltd. After 2600 rotations and treatment for 10 minutes, 75.0 parts of organic pigment magenta (trade name: CROMOPHTAL jet Magenta DMQ, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added, and the disperse blade was rotated 8000 rotations per minute. And treated at 15 ° C. for 1 hour to obtain Dispersion (5-1).
The degree of neutralization of the polymer in the obtained dispersion (5-1) was 50 mol% as a result of calculation as follows.
Number of moles of NaOH = 4.8 / 40 × 0.168 = 0.0202 mole Number of moles of carboxy group of polymer = 25 × 0.14 / 86 = 0.0407 mole Degree of neutralization = 0.0227 / 0.0407 × 100 = 50 (mol%)
The weight ratio of water to the organic solvent (water / organic solvent) was (4.8 × (1−0.168) +209.5) /73.4=2.9.
The solid content concentration was (25 + 75 + 4.8 × 0.168) / (25 + 73.4 + 75 + 4.8 + 209.5) × 100 = 26 (% by weight).

[Process (II)]
To the dispersion (5-1) obtained in the step (I), 50.6 parts of ion exchange water was added, and the mixture was stirred at 8000 rpm with a homodisper at 15 ° C. for 0.5 hour. Furthermore, 1.5 parts of 5N sodium hydroxide aqueous solution and 41.5 parts of ion-exchanged water were added, and the mixture was stirred at 8000 rpm with a homodisper at 15 ° C. for 1 hour to obtain dispersion (5-2).
The degree of neutralization of the polymer in the obtained dispersion (5-2) was 65 mol% as a result of calculation as follows.
Number of moles of NaOH = (4.8 + 1.5) /40×0.168=0.0265 mol Degree of neutralization = 0.0265 / 0.0407 × 100 = 65 (mol%)
The weight ratio of water to organic solvent (water / organic solvent) was [(4.8 + 1.5) × (1−0.168) + 209.5 + 50.6 + 41.6] /73.4=4.2. .
The solid concentration was {25 + 75 + (4.8 + 1.5) × 0.168} / (25 + 73.4 + 75 + 4.8 + 1.5 + 209.5 + 50.6 + 41.5) × 100 = 21 (% by weight).

[Process (III)]
Dispersion (5-2) obtained in step (II) was treated with a microfluidizer (trade name, manufactured by Micro fluidics) for 20 passes at a pressure of 200 MPa to obtain Dispersion (5-3).
Post-treatment step: To dispersion (5-3) obtained in step (III), 250 parts of ion-exchanged water was added to the obtained dispersion and stirred, and then methyl ethyl ketone and a part thereof under reduced pressure at 60 ° C. This water was removed to obtain an aqueous dispersion (5) for ink jet recording containing 20% by weight of polymer particles containing a pigment.

Comparative Example 4 (Preparation of water dispersion for inkjet recording (6))
In Example 2, an inkjet recording water dispersion (6) was obtained in the same manner as in Example 2 except that the step (II) was changed as follows.
[Process (II)]
To the dispersion (5-1) obtained in step (I), 92.3 parts of ion-exchanged water was added, and the mixture was supplied to Primics Co., Ltd., TK Robotics (Homo Dispers), and the Disper blade was rotated 8000 per minute. The mixture was treated at 15 ° C. for 1 hour to obtain Dispersion (6-2).
The degree of neutralization of the resulting dispersion (6-2) was 50 mol%.
The weight ratio of water to the organic solvent (water / organic solvent) was {4.8 × (1−0.168) + 209.5 + 92.3} /73.4=4.2.
The solid content concentration was (25 + 75 + 4.8 × 0.168) / (25 + 73.4 + 75 + 4.8 + 209.5 + 92.3) × 100 = 21 (% by weight).

Comparative Example 5 (Preparation of aqueous dispersion for ink jet recording (7))
In Example 2, an inkjet recording water dispersion (7) was obtained in the same manner as in Example 2 except that the steps (I) and (II) were changed as follows.
[Process (I)]
A solution prepared by dissolving 25.0 parts of the polymer (B) obtained in Production Example 2 in 73.4 parts of methyl ethyl ketone, 4.8 parts of a 5N aqueous sodium hydroxide solution (the neutralization degree of the carboxy group of the polymer is 50 mol%), and Add 301.0 parts of deionized water (weight ratio of (organic solvent / water) 1 / 4.2) and stir, then charge into TK Robotics (Homo Disper) manufactured by Primics Co., Ltd. After rotating and treating for 10 minutes, 75.0 parts of organic pigment magenta (trade name: CROMOPHTAL jet Magenta DMQ manufactured by Ciba Specialty Chemicals Co., Ltd.) was added, and the disperse blade was rotated 8000 per minute, The dispersion (7-1) was obtained by treatment at 15 ° C for 1 hour.
The weight ratio of water to organic solvent (water / organic solvent) was (4.8 × (1−0.168) +301.0) /73.4=4.2.
The solid content concentration was (25 + 75 + 4.8 × 0.168) / (25 + 73.4 + 75 + 4.8 + 301.0) × 100 = 21 (% by weight).

[Process (II)]
To the dispersion (7-1) obtained in the step (I), 1.5 parts of 5N aqueous sodium hydroxide solution was added, and the mixture was stirred at 8000 rpm with a homodisper for 1 hour at 15 ° C. 2) was obtained.
The degree of neutralization of the polymer in the obtained dispersion (7-2) was 65 mol%.
The weight ratio of water to the organic solvent (water / organic solvent) was {(4.8 + 1.5) × (1−0.168) +301.0} /73.4=4.2.
The solid content concentration was {25 + 75 + (4.8 + 1.5) × 0.168} / (25 + 73.4 + 75 + 4.8 + 1.5 + 301.0) × 100 = 21 (% by weight).

Comparative Example 6 (Preparation of aqueous dispersion for ink jet recording (8))
In Example 2, an inkjet recording water dispersion (8) was obtained in the same manner as in Example 2 except that the step (II) was changed as follows.
[Process (II)]
To the dispersion (5-1) obtained in the step (I), 50.6 parts of ion-exchanged water was added, and the disperse blade was rotated 8000 per minute and treated at 15 ° C. for 1 hour. Further, 9.7 parts of 5N sodium hydroxide aqueous solution and 39.8 parts of ion-exchanged water were added so that the solid content concentration became 21%, and then charged into TK Robotics (Homo Disper) manufactured by Primics Co., Ltd. The blade was rotated 8000 per minute and treated at 15 ° C. for 1 hour to obtain dispersion (8-2).
The degree of neutralization of the polymer in the obtained dispersion (8-2) was 150 mol% as a result of calculation as follows.
Number of moles of NaOH = (4.8 + 9.7) /40×0.168=0.0609 mol Degree of neutralization = 0.0609 / 0.0407 × 100 = 150 (mol%)
The weight ratio of water to organic solvent (water / organic solvent) was [(4.8 + 9.7) × (1−0.168) + 209.5 + 50.6 + 39.8] /73.4=4.3. .
The solid concentration was {25 + 75 + (4.8 + 9.7) × 0.168} / (25 + 73.4 + 75 + 4.8 + 9.7 + 209.5 + 50.6 + 39.8) × 100 = 21 (% by weight).

Preparation Example (Manufacture of water-based ink)
37.5 parts of the aqueous dispersions (1) to (10) for inkjet recording obtained in Examples 1 and 2 and Comparative Examples 1 to 6, 10 parts of glycerin (manufactured by Kao Corporation), 2- {2- (2 -Butoxyethoxy) ethoxy} ethanol (Wako Pure Chemical Industries, Ltd.) 5 parts, 1,2-hexanediol (Tokyo Chemical Industry Co., Ltd.) 2 parts, 2-pyrrolidone (Wako Pure Chemical Industries, Ltd.) 1 part Acetyleneol E100 (manufactured by Kawaken Fine Chemical Co., Ltd .: 1.0 part of EO adduct (n = 10), 0.3 part of Proxel BDN (manufactured by Arch Chemicals Japan Co., Ltd.), and 43.2 parts of ion-exchanged water were mixed. The mixture was stirred at room temperature for 15 minutes to obtain a mixed solution, which was filtered through a 1.2 μm membrane filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Sartorius, trade name: Minisart). To obtain a water-based ink.

  From Table 1, the aqueous dispersions of the examples had fewer coarse particles and excellent filterability than the aqueous dispersions of the comparative examples, and water-based inks produced using the aqueous dispersions of the examples were also filtered. It can be seen that the properties are excellent and the storage stability is also excellent.

Claims (4)

The manufacturing method of the aqueous dispersion for inkjet recording which has the following process (I)-(III).
Step (I): a polymer containing a salt-forming group, a neutralizing agent in such an amount that the degree of neutralization of the salt-forming group of the polymer is 10 to 70 mol%, and the weight ratio of water to the organic solvent (water / organic solvent) Step of obtaining a dispersion (1) by subjecting a mixture containing water, an organic solvent, and a pigment, each of which is 1 to 3 to dispersion (1) Step (II): In the dispersion (1) obtained in Step (I), A neutralizing agent and water are added, the degree of neutralization of the salt-forming groups of the polymer is increased, the weight ratio of (water / organic solvent) is increased, and the degree of neutralization of the salt-forming groups of the polymer is 50 to 100 mol. Step of obtaining dispersion (2) in which the weight ratio of (water / organic solvent) is more than 3 and not more than 20 Step (III): Dispersing dispersion (2) obtained in step (II) Processing to obtain dispersion (3)   The ratio of the total solid content concentration of the polymer and pigment in the dispersion (2) to the total solid content concentration of the salt-containing polymer and pigment in the dispersion (1) is 0.20 to 0.99. The method for producing an aqueous dispersion for ink jet recording according to claim 1.   The method for producing an aqueous dispersion for inkjet recording according to claim 1 or 2, wherein the polymer is a water-insoluble polymer.   An aqueous ink for inkjet recording, comprising the aqueous dispersion for inkjet recording obtained by the production method according to claim 1.