JP2015098506A - Production method of water dispersion for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a water dispersion for inkjet recording which can suppress an increase in viscosity of dry ink when compounded in an ink and which gives an ink having good re-dispersibility and thereby, resulting in excellent nozzle recovery property.SOLUTION: The production method of a water dispersion for inkjet recording includes: a step (1) of obtaining a dispersion (1) by dispersing a mixture comprising an organic solvent, (A), a pigment, a water-insoluble anionic polymer, and water; a step (2) of obtaining a water dispersion (2) by removing the organic solvent (A) from the water dispersion (1); and a step (3) of obtaining the water dispersion for inkjet recording by crosslinking the water-insoluble anionic polymer in a dispersion (3) prepared by mixing the water dispersion (2), a polyhydric alcohol (B) having 2 to 6 carbon atoms, and a crosslinking agent (C).

Description

  The present invention relates to a method for producing an aqueous dispersion for inkjet recording.

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, inks using pigments as colorants have been widely used in order to impart weather resistance and water resistance to printed matter.

Patent Document 1 contains at least a propylene oxide addition polymer of propylene glycol and a lower alcohol in an ink in which a pigment is dispersed in an aqueous medium for the purpose of improving discharge stability, nozzle clogging, and the like. An aqueous ink is disclosed.
Patent Document 2 discloses propylene oxide as a polymer particle polymer in a water-based ink containing polymer particles containing a pigment for the purpose of improving the uniformity, ejection reliability, and storage stability while maintaining a high print density. An aqueous ink using a polymer having a chain and containing a specific diol is disclosed.
In Patent Document 3, a mixture containing a pigment, a polymer, a neutralizing agent, a specific organic solvent (a good solvent for the polymer), and water is used for the purpose of improving redispersibility and initial dischargeability with few coarse particles. To obtain a dispersion, and then add a polyol having 2 to 6 carbon atoms and then remove the organic solvent, and obtain the dispersion from the aqueous dispersion. A water-based ink is disclosed.

JP 2001-002964 A JP 2010-084086 A JP 2011-127066 A

In recent years, rapid development of ink jet recording technology has made it possible to obtain high image quality, and therefore, application of ink jet recording technology to commercial printing is expected. Recently, speeding up of image formation using a recording apparatus having a long line head installed in a direction perpendicular to a direction in which a recording medium is conveyed has been performed.
In the pigment-containing ink used in the recording apparatus as described above, when the ink discharge is stopped and the ink around the hole of the ink discharge nozzle is dried, an aggregate thickening material is generated around the hole of the ink discharge nozzle, and the nozzle When clogging occurs and the purge operation of the recording head is performed, the clogging of the nozzles is not eliminated, the ink droplet ejection direction is bent, and the image may be disturbed. In order to suppress such image disturbance, it is conceivable to reduce the pigment concentration in the ink, but in such a case, it is difficult to form an image having a sufficient concentration.
The present invention has a small increase in viscosity of the ink after drying (hereinafter, also referred to as “dry ink”) even when the ink is dried, and is excellent in redispersibility of the dry ink. It is an object of the present invention to provide a method for producing an aqueous dispersion for inkjet recording, in which an ink that can be easily eliminated (hereinafter also referred to as “nozzle returnability”) can be obtained even if the nozzle of the inkjet recording apparatus temporarily becomes clogged. To do.

The present inventors removed the organic solvent from the dispersion (1) obtained by dispersing a mixture containing an organic solvent, a pigment, a water-insoluble anionic polymer, and water, and obtained the dispersion (2). An aqueous dispersion for inkjet recording obtained by crosslinking the water-insoluble anionic polymer in the dispersion (2), the dispersion (3) containing a specific polyhydric alcohol and a crosslinking agent after It has been found that when blended in the ink, an increase in viscosity of the dry ink can be suppressed and redispersibility is good, so that an ink excellent in nozzle returnability of the ink jet recording apparatus can be provided.
The present invention relates to the following [1] and [2].
[1] A method for producing an aqueous dispersion for inkjet recording, comprising the following steps (1) to (3).
Step (1): Step of obtaining a dispersion (1) by dispersing a mixture containing an organic solvent (A), a pigment, a water-insoluble anionic polymer, and water Step (2): Organic from the dispersion (1) Step of removing solvent (A) to obtain aqueous dispersion (2) Step (3): Mixing aqueous dispersion (2), polyhydric alcohol (B) having 2 to 6 carbon atoms and crosslinking agent (C) A step (2) of obtaining a water dispersion for ink jet recording by crosslinking the water-insoluble anionic polymer in the dispersion (3) obtained as described above, and a method for producing an ink for ink jet recording.
Step (4): A step of further mixing at least one selected from water and an organic solvent (D) into the aqueous dispersion for inkjet recording obtained by the method described in [1] above.

According to the present invention, when blended in an ink, an increase in viscosity of a dry ink can be suppressed, and redispersibility is good, so that an ink excellent in nozzle resetability of an ink jet recording apparatus can be obtained. A manufacturing method can be provided.
In the present invention, “good ink redispersibility” means that the dried ink is easily redispersed in the original ink before drying.

  The present invention relates to a method for producing an aqueous dispersion for inkjet recording, comprising the steps (1) to (3). According to the method of the present invention, the aqueous dispersion (2) obtained by removing the organic solvent (A) from the dispersion (1) obtained in the step (1), the specific polyhydric alcohol (B), And a water-insoluble anionic polymer (hereinafter also referred to as “polymer used in the present invention” or simply “polymer”) contained in the aqueous dispersion (2) in the presence of the crosslinking agent (C). When added to the ink, an increase in the viscosity of the dried ink can be suppressed, and since the redispersibility is also good, it is possible to provide an aqueous dispersion from which an ink excellent in nozzle returnability of an ink jet recording apparatus can be obtained.

The reason why the above effect can be obtained by the method for producing an aqueous dispersion of the present invention is not clear, but is considered as follows.
First, in step (1), the polymer can be sufficiently adhered to the pigment surface by dispersing the pigment in the presence of the organic solvent (A) and the water-insoluble anionic polymer. Then, the polymer on the pigment surface can be firmly attached to the pigment by removing the organic solvent (A) having high polymer solubility in the step (2). Furthermore, in the step (3), the dispersibility of the crosslinking agent (C) is improved by crosslinking the polymer in the dispersion with the crosslinking agent (C) in the presence of the specific polyhydric alcohol (B). The uniformity of the crosslinking reaction is improved, and the polymer on the pigment surface can be more firmly attached. As a result, the ink containing the aqueous dispersion obtained by the production method of the present invention is less likely to cause polymer detachment from the pigment surface even when the ink is dried. It is thought that an increase in viscosity can be suppressed.
In the method for producing an aqueous dispersion, if the polyhydric alcohol (B) is not present during the crosslinking treatment in the step (3), the crosslinking reaction of the polymer does not proceed uniformly, and the polymer is firmly attached to the pigment surface. Therefore, the effect of the present invention cannot be obtained. However, after the pigment dispersion, when the polyhydric alcohol (B) is mixed before the organic solvent (A) is removed (that is, before the end of the step (2)), the organic solvent (A) is removed. The pigment surface polymer may be detached in the polyhydric alcohol (B) and the pigment dispersion may aggregate. As a result, even if the dispersion is blended with the ink, the increase in the viscosity of the dry ink cannot be suppressed, the redispersibility is also lowered, and the nozzle clogging that is the subject of the present invention may not be eliminated.
Hereinafter, each component and each process used for this invention are demonstrated.

[Pigment]
Examples of the pigment used in the present invention include various inorganic pigments and organic pigments.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, metal chloride and the like. Among these, carbon black is preferably used as the black pigment. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

Examples of organic pigments include azo, disazo, phthalocyanine, benzimidazolone, quinacridone, isoindolinone, isoindoline, dioxazine, perylene, perinone, indigo, thioindigo, anthraquinone And quinophthalone pigments. Among these, from the viewpoint of color developability and safety, azo series such as PY74, disazo series such as PY128, PY155, phthalocyanine series such as PB15: 3, PB15: 4, PB15: 6, PY180, PY151, etc. Benzimidazolone series, isoindolinone series such as PY109, quinacridone series such as PR122 and PV19, and quinophthalone series such as PY138.
In this invention, a pigment can be used individually or in mixture of 2 or more types in arbitrary ratios. In addition, pigment derivatives obtained by chemically modifying the pigment surface, self-dispersing pigments and the like can also be used.

  When the pigment is used in an aqueous dispersion, it is preferable to form fine particles that are stable in the dispersion medium using a surfactant or a water-insoluble anionic polymer described later. From the viewpoints of dispersion stability, suppression of bleeding, and improvement in water resistance, it is more preferable to include a pigment in the water-insoluble anionic polymer particles.

(Water-insoluble anionic polymer)
The water-insoluble anionic polymer used in the present invention disperses the pigment in an aqueous medium containing the organic solvent (A) and water by adsorbing to the pigment surface and suppressing aggregation of the pigments, thereby improving dispersion stability. It is thought to improve. Further, it is considered that the polymer forms polymer particles containing a pigment (hereinafter also simply referred to as “polymer particles”) in the dispersion.
Here, “anionic” means that when an unneutralized substance is dispersed or dissolved in pure water, the pH is less than 7, or the substance is insoluble in pure water, and the pH is clearly measured. When it cannot, it means that the zeta potential of the dispersion dispersed in pure water becomes negative.
The polymer is a water-insoluble polymer from the viewpoint of dispersion stability of an aqueous dispersion and an ink containing the aqueous dispersion. Here, “water-insoluble” means that when a substance which has been dried at 105 ° C. for 2 hours and reaches a constant weight is dissolved in 100 g of water at 25 ° C., the dissolved amount is 10 g or less. The amount of dissolution in the polymer used in the present invention is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of dispersion stability. When the polymer has an anionic group, the dissolved amount is a dissolved amount when the anionic group is neutralized 100% with sodium hydroxide.
Examples of the polymer include polyesters, polyurethanes, vinyl polymers, and the like, from the viewpoint of storage stability of the aqueous dispersion, preferably vinyl polymers, and more preferably selected from vinyl compounds, vinylidene compounds, and vinylene compounds. It is a vinyl polymer obtained by addition polymerization of one or more kinds of vinyl monomers.

  The polymer is preferably a monomer mixture containing (a) an anionic monomer (hereinafter also referred to as “(a) component”) and (b) a hydrophobic monomer (hereinafter also referred to as “(b) component”). Hereinafter, it is a vinyl polymer obtained by copolymerization of simply “monomer mixture”. The vinyl polymer preferably has a structural unit derived from the component (a) and a structural unit derived from the component (b), more preferably derived from (c) a macromer (hereinafter also referred to as “component (c)”). It has a structural unit.

[Anionic monomer: component (a)]
The component (a) is preferably used as a monomer component constituting the polymer used in the present invention. The structural unit derived from component (a) is considered to stably disperse the polymer particles in the aqueous dispersion by electrostatic repulsion.
(A) As a component, the monomer etc. which have a carboxy group, a sulfo group, a phosphoric acid group, and a phosphonic acid group are mentioned.
Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Examples of the monomer having a sulfo group include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and 3-sulfopropyl (meth) acrylate.
Examples of the monomer having a phosphoric acid group include vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, and the like.
Examples of the monomer having a phosphonic acid group include vinylphosphonic acid.
Among the components (a), from the viewpoint of dispersion stability of the polymer particles in the aqueous dispersion, the monomer is preferably a monomer having a carboxy group, more preferably at least one selected from acrylic acid and methacrylic acid.

[Hydrophobic monomer: component (b)]
The component (b) is preferably used as a monomer component constituting the polymer. It is considered that the structural unit derived from the component (b) contributes to the dispersion stability of the polymer particles in the aqueous dispersion by promoting the adsorption of the polymer to the pigment surface.
The component (b) is preferably one selected from alkyl (meth) acrylate and an aromatic compound having an ethylenic double bond (hereinafter also referred to as “aromatic monomer”) from the viewpoint of ease of production of the polymer. From the viewpoint of the dispersion stability of the polymer particles, aromatic monomers are more preferable.
The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate is preferably 1 or more, more preferably 6 or more, from the viewpoint of dispersion stability of the polymer particles, and preferably 22 from the viewpoint of ease of production of the polymer. Below, more preferably 18 or less.
Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, pentyl, isopentyl, cyclohexyl, 2-ethylhexyl, octyl, isooctyl, and decyl. Group, isodecyl group, lauryl group, isododecyl group, stearyl group, isostearyl group and the like.
The alkyl (meth) acrylate is preferably one or more selected from methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and stearyl (meth) acrylate from the viewpoint of availability. In view of dispersion stability, it is more preferably at least one selected from 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and stearyl (meth) acrylate. In the present specification, “(meth) acrylate” represents one or more selected from acrylate and methacrylate.

The aromatic monomer is preferably a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, and more preferably having a styrene monomer and an aromatic group from the viewpoint of ease of production of the polymer ( One or more selected from (meth) acrylates.
The styrenic monomer is preferably one or more selected from styrene, 2-methylstyrene and divinylbenzene, and more preferably styrene from the viewpoint of availability.
The (meth) acrylate having an aromatic group is preferably at least one selected from benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, more preferably benzyl (meth) acrylate, from the viewpoint of availability.
Moreover, as an aromatic monomer, it is preferable to use together a styrene-type monomer and aromatic (meth) acrylate from a pigment dispersible viewpoint, and it is more preferable to use styrene and benzyl (meth) acrylate together.

[Macromer: Component (c)]
The component (c) is a compound having a polymerizable functional group at one end and having a number average molecular weight of 500 or more, and is preferably used as a monomer component constituting the polymer from the viewpoint of dispersion stability in an aqueous dispersion of polymer particles. It is done. The polymerizable functional group present at one end is preferably one or more selected from an acryloyloxy group and a methacryloyloxy group, more preferably a methacryloyloxy group.
(C) The number average molecular weight of a component becomes like this. Preferably it is 1,000 or more, Preferably it is 100,000 or less, More preferably, it is 10,000 or less. 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 component (c), from the viewpoint of dispersion stability of the polymer particles in the aqueous dispersion, the constituent unit of the macromer has an aromatic group (hereinafter also referred to as “aromatic macromer”) and the silicone macromer. Aromatic macromers are preferred and more preferred.
Examples of the monomer from which the structural unit of the aromatic macromer is derived include the aromatic monomers, preferably one or more selected from styrene and benzyl (meth) acrylate, and more preferably styrene.
Examples of the aromatic macromer having a structural unit derived from styrene include “AS-6 (S)”, “AN-6 (S)”, “HS-6 (S)” manufactured by Toagosei Co., Ltd., and the like.
Examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.

[Nonionic monomer: component (d)]
A nonionic monomer (hereinafter also referred to as “component (d)”) is preferably used as a monomer component constituting the polymer used in the present invention. The structural unit derived from the component (d) is considered to contribute to the dispersion stability of the polymer particles in the aqueous dispersion by steric repulsion due to the nonionic group.
Examples of the component (d) include compounds represented by the following general formula (1).

In Formula (1), R ¹ is a hydrogen atom or a methyl group, R ² is an alkanediyl group having 2 or 3 carbon atoms, and n is an average number of structural units represented by (R ² O) of 1 or more and 100 the following numbers, R ³ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.
The carbon number of R ² is preferably 2 from the viewpoint of the ease of production of the component (d), and preferably 3 from the viewpoint of dispersion stability of the polymer particles in the aqueous dispersion. n is preferably 1 or more, more preferably 4 or more, and still more preferably 8 or more, from the viewpoint of dispersion stability of the polymer particles in the aqueous dispersion. From the viewpoint of ease of production of the component (d), Preferably it is 30 or less, More preferably, it is 15 or less. R ³ is preferably at least one selected from a hydrogen atom, a methyl group and a phenyl group from the viewpoint of availability.
Examples of the compound represented by the formula (1) include 2-hydroxyethyl (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol polypropylene glycol (meth) acrylate, and the like. As the component (d), polypropylene glycol (meth) acrylate and phenoxy polyethylene glycol polypropylene glycol (meth) acrylate are preferable from the viewpoint of storage stability of the ink, and it is more preferable to use these in combination.

As the component (d), “M-20G”, “40G”, “90G” of “NK Ester” series manufactured by Shin-Nakamura Chemical Co., Ltd .; “PE-90” of “Blemmer” series manufactured by NOF Corporation, “200”, “350”, “PME-100”, “PME-200”, “PME-400”, “PP-500”, “PP-800”, “AP-150”, “AP-400”, “AP-550”, “50PEP-300”, “50POEP-800B”, “43PAPE-600B” and the like can be mentioned.
The components (a) to (d) can be used alone or in combination of two or more.

The preferable content of the structural unit derived from the components (a) to (d) in the polymer is as follows.
The content of the component (a) is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and preferably 40% by mass or less, from the viewpoint of the storage stability of the ink. More preferably, it is 30 mass% or less, More preferably, it is 25 mass% or less.
The content of the component (b) is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 98% by mass or less, more preferably 80% by mass or less, from the viewpoint of improving the printing density of the ink. More preferably, it is 60 mass% or less.
The content of the component (c) is preferably 1% by mass or more, more preferably 5% by mass or more, preferably 25% by mass or less, more preferably 20% by mass from the viewpoint of enhancing the interaction between the pigment and the polymer. It is as follows.
The content of component (d) is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 35%, from the viewpoints of ink storage stability and nozzle returnability. It is below mass%.
The mass ratio of [(a) component / [(b) component + (c) component]] is from the viewpoint of the dispersion stability of the polymer particles in the aqueous dispersion and the print density of the ink containing the aqueous dispersion. Preferably it is 0.01 or more, More preferably, it is 0.02 or more, More preferably, it is 0.03 or more, Preferably it is 1 or less, More preferably, it is 0.67 or less, More preferably, it is 0.50 or less.

(Manufacture of polymers)
The polymer is produced, for example, by copolymerizing a monomer mixture by a known polymerization method. Preferable content of the said (a)-(d) component in a monomer mixture is the same as preferable content of the structural unit derived from the (a)-(d) component in the above-mentioned polymer.
As the polymerization method, a solution polymerization method is preferable. The solvent used in the solution polymerization method is preferably an organic solvent (A) described later from the viewpoint of ease of production of the polymer and the dispersion. From the viewpoint of dispersibility, the solvent used in the solution polymerization method is more preferably 4 or more and 8 or less carbon atoms, one or more selected from ketones, alcohols, ethers and esters, and further preferably 4 or more and 8 or less carbon atoms. And more preferably methyl ethyl ketone (hereinafter also referred to as “MEK”).
In the polymerization, a known polymerization initiator or polymerization chain transfer agent can be used. The polymerization initiator is preferably 2,2′-azobis (2,4-dimethylvaleronitrile), and the polymerization chain transfer agent 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 ° C. or higher and 80 ° C. or lower, and the polymerization time is preferably 1 hour or longer and 20 hours or shorter. The polymerization is preferably performed in an inert gas atmosphere such as nitrogen gas 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 polymer is preferably 5,000 or more, more preferably 10,000 or more, further preferably 20,000 or more, and preferably 500,000 or less, from the viewpoint of dispersion stability of the polymer particles in the aqueous dispersion. 400,000 or less is more preferred, 300,000 or less is more preferred, and 200,000 or less is even more preferred. The weight average molecular weight is measured by the method described in the examples.

〔Neutralizer〕
In this invention, you may neutralize the anionic group which the said polymer has using a neutralizing agent. Examples of the neutralizing agent include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and various amines.
From the viewpoint of dispersion stability, the degree of neutralization of the polymer before the crosslinking treatment in the step (3) is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more. From the viewpoint of the adsorptive property and crosslinking efficiency, it is preferably 90 mol% or less, more preferably 80 mol% or less, and still more preferably 70 mol% or less.
The degree of neutralization of the polymer can be determined by the following formula.
Degree of neutralization (mol%) = {[mass of neutralizer (g) / gram equivalent of neutralizer] / [acid value of polymer (KOH mg / g) × polymer mass (g) / (56 × 1000) ] × 100
The acid value of the polymer can be calculated from the ratio of monomer components at the time of polymer production. Moreover, it can obtain | require by the method of melt | dissolving a polymer in the solvent which can melt | dissolve polymers, such as MEK, and titrating with an alkaline agent.

[Organic solvent (A)]
The organic solvent (A) used for this invention is an organic solvent except a C2-C6 polyhydric alcohol (B). From the viewpoint of sufficiently attaching the polymer to the pigment surface in the step (1), an organic solvent having polarity and capable of dissolving the polymer is preferable. The organic solvent (A) is preferably one or more selected from ketones, alcohols, ethers and esters having 4 to 8 carbon atoms, more preferably ketones having 4 to 8 carbon atoms. These organic solvents are suitable for dispersion because they are easy to dissolve the water-insoluble anionic polymer, and have excellent wettability to the pigment because of their polarity.
The ketone having 4 to 8 carbon atoms is preferably a ketone having 4 to 6 carbon atoms such as MEK, methyl isobutyl ketone and diethyl ketone, more preferably MEK, from the viewpoint of solubility of the polymer and ease of removal. One or more selected from methyl isobutyl ketone, more preferably MEK.
Examples of the alcohol having 4 to 8 carbon atoms include isobutyl alcohol and n-butyl alcohol.
Examples of the ether having 4 to 8 carbon atoms include chain ethers such as dibutyl ether, and cyclic ethers such as tetrahydrofuran and dioxane.
Examples of the ester having 4 to 8 carbon atoms include ethyl acetate and butyl acetate.
These organic solvents (A) can be used alone or in combination of two or more.

[Polyhydric alcohol (B)]
The polyhydric alcohol (B) used in the present invention is a polyhydric alcohol having 2 to 6 carbon atoms. The dispersion (2) in which the organic solvent (A) is removed in the step (2) to reduce the solubility of the polymer and the polymer is firmly attached to the pigment is used in the polyhydric alcohol ( If the polymer is subjected to a crosslinking treatment in the presence of B), the dispersibility of the crosslinking agent (C) is improved and the uniformity of the crosslinking reaction is improved, so that the effect of the present invention is considered to be exhibited.
Examples of the polyhydric alcohol having 2 to 6 carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, diethylene glycol, Diols such as propylene glycol and neopentyl glycol; triols such as glycerin and trimethylolpropane; pentaerythritol, inositol, sorbitol and the like.
Among these, from the viewpoint of obtaining the effects of the present invention and obtaining good ink performance even when remaining in the ink, at least one selected from diols having 2 to 4 carbon atoms and glycerin is preferable. 1 or more types chosen from glycerol and propylene glycol are more preferable.
These polyhydric alcohols (B) can be used alone or in combination of two or more.

[Crosslinking agent (C)]
The crosslinking agent (C) used in the present invention is used for crosslinking the polymer adhering to the pigment surface and improving the dispersion stability of the resulting aqueous dispersion and ink containing the same.
The crosslinking agent (C) is preferably a compound having two or more functional groups capable of reacting with the anionic group of the polymer in the molecule. The molecular weight of the crosslinking agent (C) is preferably 120 or more, more preferably 150 or more, and 2000 or less, from the viewpoint of suppressing the increase in the viscosity of the dry ink when the aqueous dispersion is blended with the ink and the redispersibility of the ink. Is preferable, 1500 or less is more preferable, and 1000 or less is still more preferable.

When the anionic group of the polymer is a carboxy group, the crosslinking agent (C) is preferably a compound having two or more epoxy groups in the molecule.
Compounds having two or more epoxy groups in the molecule include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylol. One or more selected from polyglycidyl ethers such as propane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether and hydrogenated bisphenol A type diglycidyl ether . Among these, Preferably it is 1 or more types chosen from ethylene glycol diglycidyl ether and a trimethylol propane polyglycidyl ether, More preferably, it is a trimethylol propane polyglycidyl ether.

[Production of water dispersion for inkjet recording]
The manufacturing method of the water dispersion for inkjet recording of this invention has the following process (1)-(3).
Step (1): Step of obtaining a dispersion (1) by dispersing a mixture containing an organic solvent (A), a pigment, a water-insoluble anionic polymer, and water Step (2): Organic from the dispersion (1) Step of removing solvent (A) to obtain aqueous dispersion (2) Step (3): Mixing aqueous dispersion (2), polyhydric alcohol (B) having 2 to 6 carbon atoms and crosslinking agent (C) Cross-linking the water-insoluble anionic polymer in the resulting dispersion (3) to obtain an aqueous dispersion for inkjet recording

[Step (1)]
Step (1) is a step of obtaining a dispersion (1) by dispersing a mixture containing an organic solvent (A), a pigment, a water-insoluble anionic polymer, and water. A neutralizing agent may be added to the mixture in order to neutralize the water-insoluble anionic polymer. The organic solvent (A), pigment, water-insoluble anionic polymer, and neutralizing agent are as described above.
In the dispersion treatment of step (1), a water-insoluble anionic polymer is dissolved in an organic solvent (A) to prepare an organic solvent solution of the polymer, and then a pigment, water and, if necessary, a neutralizing agent, a surfactant A method of adding an agent or the like to the obtained polymer solution and mixing and dispersing to obtain an oil-in-water dispersion (1) is preferred. Although there is no restriction | limiting in the order which adds a pigment, water, and a neutralizing agent to the organic solvent solution of an anionic polymer, It is preferable to add in order of a neutralizing agent, water, and a pigment.
The content of the pigment in the mixture is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less. Content of the organic solvent (A) in the said mixture becomes like this. Preferably it is 10 mass% or more, Preferably it is 70 mass% or less, More preferably, it is 50 mass% or less. The content of the polymer in the mixture is preferably 2% by mass or more, more preferably 3% by mass or more, preferably 40% by mass or less, more preferably 20% by mass or less. The water content in the mixture is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 70% by mass or less.
The amount of the polymer with respect to 100 parts by mass of the pigment in the mixture of the step (1) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more from the viewpoint of dispersion stability, and from the same viewpoint, preferably 100 It is not more than part by mass, more preferably not more than 60 parts by mass.
The amount of the organic solvent (A) in the mixture of step (1) is preferably 10 parts by mass or more, more preferably 15 parts by mass, from the viewpoint of pigment dispersibility and ink redispersibility. From the same viewpoint, it is preferably 40 parts by mass or less, more preferably 30 parts by mass or less.
The neutralizing agent is preferably used so that the pH of the finally obtained aqueous dispersion is 7 or more and 11 or less.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (1). Although the average particle size of the pigment particles can be atomized only by the main dispersion until the desired particle size is obtained, preferably the pre-dispersion is performed, and then the main dispersion is further performed by applying a shear stress to obtain the average particle size of the pigment particles. It is preferable to control the diameter to a desired particle diameter.
The temperature in the dispersion in the step (1) is preferably 0 ° C. or higher, preferably 50 ° C. or lower, more preferably 35 ° C. or lower. The dispersion time is preferably 1 hour or longer, more preferably 2 hours or longer, preferably 30 hours or shorter, more preferably 25 hours or shorter.
When the mixture is predispersed, a generally used mixing and stirring device such as an anchor blade or a disper blade, particularly a high-speed stirring and mixing device is preferable.
Examples of means for applying the shear stress of this dispersion include a kneader such as a roll mill and a kneader, and a media type disperser such as a high-pressure homogenizer, a paint shaker, and a bead mill. Among these, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment particles.
Examples of the high-pressure homogenizer include “Microfluidizer” manufactured by Microfluidics. Examples of the media type disperser include “Ultra Apex Mill” manufactured by Kotobuki Industries Co., Ltd., “Pico Mill” manufactured by Asada Iron Works Co., Ltd., and the like. A plurality of these devices can be combined.

[Step (2)]
Step (2) is a step of removing the organic solvent (A) from the dispersion (1) to obtain an aqueous dispersion (2). It is considered that the polymer on the pigment surface can be firmly attached to the pigment by removing the organic solvent (A) having high solubility of the water-insoluble anionic polymer. When removing the organic solvent (A), a part of water may be removed. In the step (2), the organic solvent (A) is removed from the dispersion obtained in the step (1) to obtain an aqueous dispersion (2), whereby the polymer particles having a desired average particle diameter are dispersed in water. You can get a body.
The organic solvent (A) contained in the dispersion (1) can be removed by a general method such as distillation under reduced pressure. The organic solvent (A) in the obtained aqueous dispersion (2) has been substantially removed, and the content of the organic solvent (A) in the aqueous dispersion (2) is preferably 0.1% by mass. Hereinafter, it is preferably 0.01% by mass or less. Furthermore, in order to obtain polymer particles having a desired particle size, it is preferable to remove coarse particles by filtering the aqueous dispersion (2). Further, the aqueous dispersion (2) may be centrifuged and separated.

As an apparatus for removing the organic solvent (A) used in the step (2), for example, a batch type evaporation apparatus is preferable. Among the batch type evaporators, it is more preferable to use a stirred tank batch type evaporator, and it is more preferable to use a stirred tank thin film type evaporator.
Here, the “batch type evaporation device” means that a heating part such as a jacket part or a heat transfer heater that can pass or vent a heat medium such as hot water or steam is disposed on the outer wall surface of the tank, or It means an evaporation apparatus in which a coil capable of passing or venting a heat medium such as hot water or steam is disposed inside the tank, and the solvent can be evaporated and removed by heating.
The “stirred tank batch type evaporator” refers to an evaporator in which a batch type evaporator is provided with a stirrer and can evaporate and remove the solvent while stirring in the tank.
The “stirred tank thin film evaporator” refers to an evaporator capable of forming a thin film such as a solution using a heating inner wall surface and evaporating and removing the solvent from the thin film surface in the stirred tank batch evaporator. . Examples of the stirred tank thin film evaporator include “Wall Wetter” manufactured by Kansai Chemical Machinery Manufacturing Co., Ltd.

  It is preferable that the mixture in step (1) and the dispersion (1) used in step (2) do not substantially contain a polyhydric alcohol (B) having 2 to 6 carbon atoms. Specifically, the content of the polyhydric alcohol (B) in the mixture of step (1) and the dispersion (1) used in step (2) is preferably 2% by mass or less, more preferably Is 0.5% by mass or less, more preferably 0% by mass. In the step (1), when the mixture substantially contains the polyhydric alcohol (B), the adhesion of the polymer to the pigment surface may be inhibited, or the polymer may not be allowed to adhere to the pigment surface. Further, when the dispersion (1) used in the step (2) substantially contains the polyhydric alcohol (B), the polymer on the pigment surface is contained in the polyhydric alcohol (B) in the step of removing the organic solvent (A). The pigment dispersion may be agglomerated due to desorption. As a result, even if the dispersion is blended with the ink, the increase in the viscosity of the dry ink cannot be suppressed, the redispersibility is also lowered, and the nozzle clogging that is the subject of the present invention may not be eliminated. Therefore, when the mixture (1) used in the step (1) and the dispersion (1) used in the step (2) contain a polyhydric alcohol (B), the amount is limited to a small amount that does not affect the effects of the present invention.

[Step (3)]
Step (3) is a dispersion (3) obtained by mixing the water dispersion (2) obtained in step (2), the polyhydric alcohol (B) having 2 to 6 carbon atoms and the crosslinking agent (C). ) In which the water-insoluble anionic polymer is crosslinked to obtain an aqueous dispersion for inkjet recording. In the step (3), water such as ion exchange water may be further mixed.
The content of the polyhydric alcohol (B) in the dispersion (3) in the step (3) is the viewpoint of suppressing the increase in the viscosity of the dry ink when the aqueous dispersion is blended with the ink and the redispersibility of the ink. Therefore, it is preferably 1% by mass or more, more preferably 3% by mass or more, and from the same viewpoint, it is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably 10% by mass or less. Moreover, in the step (3), a preferable mixing amount of the polyhydric alcohol (B) with respect to the dispersion (3) is the same as the content.
The solid content of the dispersion (3) in the step (3) is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, preferably 50% by mass or less, more preferably It is 40 mass% or less, More preferably, it is 35 mass% or less.

  The amount of the crosslinking agent (C) used is 100 parts by mass of the polymer from the viewpoint of storage stability of the dispersion, suppression of increase in viscosity of the dried ink when the aqueous dispersion is blended with the ink, and redispersibility of the ink. On the other hand, it is preferably 0.3 parts by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, preferably 50 parts by mass or less, more preferably 35 parts by mass or less, still more preferably 30 parts by mass. Hereinafter, it is more preferably 25 parts by mass or less, and still more preferably 20 parts by mass or less.

  In the crosslinking treatment in step (3), a dispersion (3) is prepared by mixing an aqueous dispersion (2), a polyhydric alcohol (B) having 2 to 6 carbon atoms and a crosslinking agent (C). It is preferable to carry out by stirring under heating conditions. The temperature during the crosslinking treatment can be appropriately selected depending on the types of the polyhydric alcohol (B) and the crosslinking agent (C) to be used, but from the viewpoint of promoting the crosslinking reaction, it is preferably 50 ° C. or more, more preferably 70 ° C or higher, more preferably 80 ° C or higher, and preferably 100 ° C or lower. The crosslinking treatment time is preferably 0.5 hours or more, more preferably 1 hour or more, further preferably 2 hours or more, preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 8 hours or less. .

  The crosslinking rate of the crosslinked polymer is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more, preferably 80 mol% or less, more preferably 70 mol% or less, still more preferably. 60 mol% or less. The crosslinking rate is obtained by dividing the number of moles of reactive functional groups of the used crosslinking agent (C) by the number of moles of reactive groups capable of reacting with the crosslinking agent (C) of the polymer.

  The average particle size of the polymer particles in the aqueous dispersion for ink jet recording obtained after the crosslinking treatment in the step (3) is determined according to the dispersibility, the suppression of the increase in the viscosity of the dried ink of the ink obtained using the dispersion, From the viewpoint of dispersibility, it is preferably 30 nm or more, more preferably 40 nm or more, still more preferably 50 nm or more, preferably 300 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less. The average particle size is measured by the method described in the examples.

[Method for producing water-based ink for inkjet recording]
Moreover, this invention provides the manufacturing method of the water-based ink for inkjet recording which has the following process (4).

Step (4): Step of further mixing one or more selected from water and an organic solvent (D) into the water dispersion for ink jet recording obtained by the above method. “Water dispersion for ink jet recording obtained by the above method” The “body” means the aqueous dispersion for inkjet recording obtained in the step (3).

[Step (4)]
Step (4) is a step of further mixing at least one selected from water and an organic solvent (D) into the aqueous dispersion for inkjet recording obtained in the step (3). By performing the step (4), an aqueous ink having ink properties such as a desired concentration and viscosity can be obtained.
Examples of the organic solvent (D) used in the step (4) include polyhydric alcohols, polyhydric alcohol alkyl ethers, and nitrogen-containing heterocyclic compounds.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4 butanediol, and 3-methyl- 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, 1,2,4-butanetriol, Examples include 1,2,3-butanetriol, petriol, triethylene glycol, tripropylene glycol, and glycerin. In these, 1 or more types chosen from glycerol, propylene glycol, and diethylene glycol are preferable.
Examples of the polyhydric alcohol alkyl ether include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoisobutyl ether, tetraethylene glycol. Examples include monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and triethylene glycol monobutyl ether.
Examples of the nitrogen-containing heterocyclic compound include N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, and ε-caprolactam.
The said organic solvent (D) can be used individually by 1 type or in combination of 2 or more types.

(Water dispersion for inkjet recording)
In order to prevent drying, a humectant and an organic solvent can be added to the aqueous dispersion for inkjet recording obtained by the production method of the present invention having the steps (1) to (3). Commonly used wetting agents, penetrants, dispersants, surfactants, viscosity modifiers, antifoaming agents, preservatives, antifungal agents, rustproofing agents, etc. can be added and used as water-based inks as they are.
From the viewpoint of obtaining a high-concentration ink, the solid content of the aqueous dispersion obtained by the production method of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more. From the viewpoint of dispersion stability, it is preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably 25% by mass or less.

In addition, the water-based ink obtained by the production method of the present invention has a small increase in viscosity and is excellent in redispersibility even after the ink is dried to obtain a dry ink. For this reason, even if nozzle clogging of the ink jet recording apparatus due to ink drying occurs, nozzle clogging can be easily eliminated.
The content of the pigment in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 4% by mass or more, and still more preferably 5% by mass from the viewpoint of increasing the printing density of the water-based ink. That's it. Further, from the viewpoint of the viscosity and stability of the water-based ink, it is preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and still more preferably 12% by mass or less.
The viscosity of the water-based ink is preferably 2 mPa · s or higher, more preferably 2.5 mPa · s or higher, more preferably 20 mPa · s or lower, at 20 ° C., from the viewpoint of maintaining good ejection stability. Preferably it is 16 mPa * s or less, More preferably, it is 12 mPa * s or less.

In relation to the above-described embodiment, the present invention discloses the following method for producing an aqueous dispersion for inkjet recording and a method for producing an aqueous ink for inkjet recording.
<1> A method for producing an aqueous dispersion for inkjet recording, comprising the following steps (1) to (3).
Step (1): Step of obtaining a dispersion (1) by dispersing a mixture containing an organic solvent (A), a pigment, a water-insoluble anionic polymer, and water Step (2): Organic from the dispersion (1) Step of removing solvent (A) to obtain aqueous dispersion (2) Step (3): Mixing aqueous dispersion (2), polyhydric alcohol (B) having 2 to 6 carbon atoms and crosslinking agent (C) Cross-linking the water-insoluble anionic polymer in the resulting dispersion (3) to obtain an aqueous dispersion for inkjet recording

<2> The organic solvent (A) is preferably one or more selected from ketones, alcohols, ethers and esters having 4 to 8 carbon atoms, more preferably ketones having 4 to 8 carbon atoms, and more preferably MEK. 1 or more selected from methyl isobutyl ketone and diethyl ketone, more preferably one or more selected from MEK and methyl isobutyl ketone, and more preferably MEK. Method.

<3> The content of the polyhydric alcohol (B) in the dispersion (3) is preferably 1% by mass or more, more preferably 3% by mass or more, preferably 50% by mass with respect to the dispersion (3). % Or less, more preferably 30% by mass or less, and still more preferably 10% by mass or less, The method for producing an aqueous dispersion for inkjet recording according to the above <1> or <2>.

<4> One type of polyhydric alcohol (B) having 2 to 6 carbon atoms, preferably selected from diols having 2 to 6 carbon atoms, triols having 2 to 6 carbon atoms, pentaerythritol, inositol, and sorbitol As described above, any one of <1> to <3>, more preferably one or more selected from diols having 2 to 4 carbon atoms and glycerol, and more preferably one or more selected from glycerol and propylene glycol. The manufacturing method of the aqueous dispersion for inkjet recording of description.

<5> The amount of the crosslinking agent (C) used is preferably 0.3 parts by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the water-insoluble anionic polymer. The above <1> to <4>, preferably 50 parts by mass or less, more preferably 35 parts by mass or less, further preferably 30 parts by mass or less, further preferably 25 parts by mass or less, and further preferably 20 parts by mass or less. A method for producing an aqueous dispersion for inkjet recording according to any one of the above.

<6> The crosslinking agent (C) preferably has a compound having two or more functional groups in the molecule capable of reacting with the anionic group of the water-insoluble anionic polymer, more preferably has two or more epoxy groups in the molecule. Compounds, more preferably ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether , Pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether and hydrogenated bisphenol A One or more selected from diglycidyl ether, more preferably one or more selected from ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether, more preferably trimethylolpropane polyglycidyl ether, the above <1> to < 5> The manufacturing method of the water dispersion for inkjet recording in any one of.

<7> The molecular weight of the crosslinking agent (C) is preferably 120 or more, more preferably 150 or more, preferably 2000 or less, more preferably 1500 or less, and still more preferably 1000 or less, <1> to < 6> The manufacturing method of the water dispersion for inkjet recording in any one of.

<8> When a water-insoluble anionic polymer is dried at 105 ° C. for 2 hours and a substance that has reached a constant weight is dissolved in 100 g of water at 25 ° C., the dissolved amount is preferably 10 g or less, more preferably The method for producing an aqueous dispersion for inkjet recording according to any one of <1> to <7>, wherein the amount is 5 g or less, more preferably 1 g or less.

<9> The water-insoluble anionic polymer is preferably a vinyl polymer having (a) a structural unit derived from an anionic monomer and (b) a structural unit derived from a hydrophobic monomer, more preferably (a) derived from an anionic monomer. The inkjet according to any one of <1> to <8>, wherein the inkjet polymer is a vinyl polymer having a structural unit derived from (b) a hydrophobic monomer and further having a structural unit derived from (c) a macromer. A method for producing an aqueous recording dispersion.

<10> (a) The anionic monomer is preferably a monomer having a carboxy group, a sulfo group, a phosphoric acid group, or a phosphonic acid group, more preferably a monomer having a carboxy group, still more preferably selected from acrylic acid and methacrylic acid. The manufacturing method of the aqueous dispersion for inkjet recording as described in said <9> which is 1 or more types.

<11> (b) The hydrophobic monomer is preferably one or more selected from an alkyl (meth) acrylate and an aromatic compound having an ethylenic double bond (aromatic monomer), more preferably an aromatic monomer. The method for producing an aqueous dispersion for inkjet recording according to <9> or <10>.

<12> The alkyl (meth) acrylate is preferably at least one selected from methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and stearyl (meth) acrylate, more preferably 2-ethylhexyl. The method for producing an aqueous dispersion for inkjet recording according to the above <11>, which is at least one selected from (meth) acrylate, dodecyl (meth) acrylate, and stearyl (meth) acrylate.

<13> The aromatic monomer is preferably at least one selected from vinyl monomers having 6 to 22 carbon atoms, more preferably styrene monomers and (meth) acrylates having aromatic groups. The manufacturing method of the aqueous dispersion for inkjet recording as described in said <11> or <12>.

<14> The method for producing an aqueous dispersion for inkjet recording according to <13>, wherein the styrene monomer is preferably one or more selected from styrene, 2-methylstyrene, and divinylbenzene, more preferably styrene.

<15> The (meth) acrylate having an aromatic group is preferably at least one selected from benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, more preferably benzyl (meth) acrylate, <13> Or the manufacturing method of the aqueous dispersion for inkjet recording as described in <14>.

<16> The inkjet recording according to any one of <11> to <15>, wherein the aromatic monomer is preferably a styrene monomer and an aromatic (meth) acrylate, more preferably styrene and benzyl (meth) acrylate. A method for producing an aqueous dispersion.

<17> (c) The method for producing an aqueous dispersion for inkjet recording according to any one of <9> to <16>, wherein the macromer is preferably a compound having a polymerizable functional group at one end.

<18> (c) The number average molecular weight of the macromer is preferably 500 or more, more preferably 1,000 or more, preferably 100,000 or less, more preferably 10,000 or less. <17> The method for producing an aqueous dispersion for inkjet recording according to any one of the above.

<19> (c) The macromer is preferably derived from one or more selected from aromatic macromers and silicone-based macromers, more preferably aromatic macromers, and still more preferably one or more selected from styrene and benzyl (meth) acrylate. The method for producing an aqueous dispersion for ink-jet recording according to any one of <9> to <18>, wherein the macromer has a structural unit that further comprises a structural unit derived from styrene.

<20> The water dispersion for ink-jet recording according to any one of the above <9> to <19>, wherein the water-insoluble anionic polymer is preferably a vinyl-based polymer further having (d) a nonionic monomer-derived structural unit. Manufacturing method.

<21> (d) The nonionic monomer is preferably a compound represented by the general formula (1), more preferably 2-hydroxyethyl (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth). The above <20>, which is one or more selected from acrylate and phenoxy polyethylene glycol polypropylene glycol (meth) acrylate, more preferably one or more selected from polypropylene glycol (meth) acrylate and phenoxy polyethylene glycol polypropylene glycol (meth) acrylate. The manufacturing method of the aqueous dispersion for inkjet recording as described in any one of.

<22> The weight average molecular weight of the water-insoluble anionic polymer is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, preferably 500,000 or less, more preferably 400,000 or less, More preferably, it is 300,000 or less, More preferably, it is 200,000 or less, The manufacturing method of the water dispersion for inkjet recording in any one of said <1>-<21>.

<23> The neutralization degree of the water-insoluble polymer before the crosslinking treatment in the step (3) is preferably 10 mol% or more, more preferably 20 mol% or more, still more preferably 30 mol% or more, preferably 90 mol. % Or less, more preferably 80 mol% or less, and still more preferably 70 mol% or less, The method for producing an aqueous dispersion for inkjet recording according to any one of <1> to <22> above.

<24> The content of the polyhydric alcohol (B) in the mixture of the step (1) is preferably 2% by mass or less, more preferably 0.5% by mass or less, and further preferably 0% by mass. The manufacturing method of the aqueous dispersion for inkjet recording in any one of 1>-<23>.

<25> The content of the polyhydric alcohol (B) in the dispersion (1) used in the step (2) is preferably 2% by mass or less, more preferably 0.5% by mass or less, and further preferably 0% by mass. The method for producing an aqueous dispersion for inkjet recording according to any one of <1> to <24>.

<26> A method for producing an inkjet recording ink, comprising the following step (4).
Step (4): A step of further mixing at least one selected from water and an organic solvent (D) with the aqueous dispersion for inkjet recording obtained by the method according to any one of <1> to <25> above.

<27> The ink for inkjet recording according to the above <26>, wherein the organic solvent (D) is preferably at least one selected from polyhydric alcohols, polyhydric alcohol alkyl ethers, and nitrogen-containing heterocyclic compounds. Method.

In the following production examples, examples and comparative examples, evaluation of polymers and inks was performed by the following methods.
(1) Measurement of polymer weight average molecular weight Gel permeation chromatography (hereinafter also referred to as “GPC”) method was used. As an eluent, an N, N-dimethylformamide (hereinafter also referred to as “DMF”) solution having a phosphoric acid concentration of 60 mmol / L and a lithium bromide concentration of 50 mmol / L was used. The sample was diluted with DMF to obtain a solution having a solid content of 0.3% by mass, and 500 μL of the solution was added to GPC [apparatus: “HLC-8220GPC” manufactured by Tosoh Corporation, column: “TSK-GEL, α- M ”× 2, column temperature: 40 ° C., flow rate: 1 mL / min]. As a standard substance, monodisperse polystyrene (manufactured by Tosoh Corporation: weight average molecular weights 842,000, 5 million, 964,000; manufactured by Nishio Kogyo Co., Ltd .: weight average molecular weights 900,000, 30,000, 40,000) is used. It was.

(2) Measurement of solid content 10 g of dry anhydrous sodium sulfate and a glass rod were placed in a petri dish, and the mass of the petri dish + glass rod + dry anhydrous sodium sulfate: a (g) was measured. A sample 1 g was weighed here (sample weight: b (g)), mixed with a glass rod, and dried at 105 ° C. for 2 hours. After cooling this to room temperature in a desiccator, the mass after drying: c (g) was measured, and the solid content was calculated from the following formula.
Solid content (mass%) = {[(mass after drying c (g)) − (petlet + glass rod + mass of dry anhydrous sodium sulfate a (g))] / (mass of sample b (g))} × 100

(3) Measurement of ink viscosity Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), using a standard rotor (1 ° 34 ′ × R24), a measurement temperature of 20 ° C., a measurement time of 1 minute, and a rotation speed of 20 to Of 100 rpm, the measurement was performed under the condition of the maximum number of rotations allowed by the apparatus with the ink.

(4) Measurement of average particle diameter Using a laser particle analysis system “ELS-8000” manufactured by Otsuka Electronics Co., Ltd., cumulant analysis (temperature: 25 ° C., angle between incident light and detector: 90 °, integration count: 100 times) , And refractive index of dispersion solvent: 1.333). The sample was measured by adjusting the concentration to about 5 × 10 ⁻³ mass% with ion-exchanged water.

(5) Measurement of viscosity of dry ink 100 g of the prepared ink was put in a glass container, and water in the ink was volatilized until the ink mass became 75 g, thereby drying the ink. The viscosity of the dried ink was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), using a standard rotor (1 ° 34 ′ × R24), a measurement temperature of 20 ° C., a measurement time of 1 minute, and a rotational speed of 0. The measurement was performed under the condition of the maximum number of revolutions allowed by the apparatus with the ink among 5 to 100 rpm.

(6) Evaluation of redispersibility of ink 5 g of ink was put into a glass petri dish whose mass was measured in advance, and left in a thermostat at 60 ° C. for 2 weeks. The petri dish was taken out from the thermostat and returned to room temperature (25 ° C.), and then the mass of the dried petri dish was measured to calculate the mass a of the dried ink. The dry ink was in a paste form due to volatilization of water.
Next, 5 g of new ink having the same composition was added to the petri dish containing the dried ink, and left at room temperature (25 ° C.) for 30 minutes. The petri dish was tilted for 20 seconds and the ink was allowed to flow out, and then the mass of the petri dish was measured, and the mass b of the ink remaining in the petri dish without flowing out was measured.
The redispersion rate of the ink was calculated from the following formula. The closer the redispersion rate is to 100%, the better the ink redispersibility.
Redispersion rate (%) = [1− (mass of ink remaining in petri dish b) / (mass of dried ink a)] × 100

(7) Evaluation of Nozzle Returnability A printing apparatus (“One Pass Jet” manufactured by Tritec Co., Ltd.) equipped with an inkjet head (“KJ4B-HD06MHG-STDV” manufactured by Kyocera Corporation) was obtained in Examples and Comparative Examples. Filled with ink, resolution: normal, output value: binary, multi-value: Bayer teaser, output size: small, head voltage: 26 V, frequency: 20 kHz, head temperature: 20 ° C., A4 photographic paper as recording medium (Epson's “Chrispia”) Using a single sheet, while moving the recording medium at 50 m / min, an amount of ink corresponding to 11 pL per pixel was ejected onto a 3 cm × 3 cm area, and evenly onto the photographic paper The inside of the nozzle was cleaned by forming an image. After leaving the nozzle surface in a non-capped state at room temperature (25 ° C.) for 30 minutes, the same printing as described above was performed twice. The dots of the obtained printed matter were observed with a microscope and evaluated according to the following criteria.
○: Discharge of all nozzles was confirmed in the first printing.
(Triangle | delta): The discharge of all the nozzles was confirmed by the 2nd printing.
X: No-discharge nozzle was confirmed in the second printing.

Production Example 1 (Production of water-insoluble anionic polymer A)
In a reaction vessel, 200 g of MEK, 0.3 g of a polymerization chain transfer agent (2-mercaptoethanol), and 200 g of a monomer mixture having a mass ratio shown in Table 1 are mixed and thoroughly replaced with nitrogen gas. Obtained.
In a dropping funnel, 1800 g of a monomer mixture having a mass ratio shown in Table 1, 0.27 g of the polymerization chain transfer agent, 600 g of MEK, and 12 g of a radical polymerization initiator [2,2′-azobis (2,4-dimethylvaleronitrile)] Were mixed and sufficiently replaced with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was increased to 65 ° C. while stirring, and the mixed solution in the dropping funnel was dropped therein in 3 hours. After completion of the dropwise addition, the mixture was stirred at 65 ° C. for 2 hours, a solution of 3 g of the radical polymerization initiator dissolved in 50 g of MEK was added, and the mixture was further stirred at 65 ° C. for 2 hours and at 70 ° C. for 2 hours. MEK was added so that the solid content of the solution in the reaction vessel was 50% by mass, and the mixture was further stirred for 30 minutes to obtain a 50% by mass solution of water-insoluble anionic polymer A. The obtained polymer A had a weight average molecular weight of 150,000.

The details of the monomers shown in Table 1 are as follows.
Styrene macromer: “AS-6 (S)” manufactured by Toa Gosei Co., Ltd. (number average molecular weight: 6,000, polymerizable functional group: methacryloyloxy group)
PP-800 (polypropylene glycol monomethacrylate): “Blenmer PP-800” manufactured by NOF Corporation (average propylene oxide addition mole number = 12, terminal: hydroxy group)
43PAPE-600B (polyethylene glycol polypropylene glycol monomethacrylate): “Blenmer 43PAPE-600B” manufactured by NOF Corporation (average added mole number of ethylene oxide = 6, average added mole number of propylene oxide = 6, terminal: phenyl group)

Example 1
(Manufacture of water dispersion 1 for inkjet recording)
<Step (1)>
In a stainless steel pail-type container (inner diameter 35 cm) having a jacket on the outer periphery, 1714 g of a 50 mass% solution of the water-insoluble anionic polymer A obtained in Production Example 1 and 1313 g of MEK as an organic solvent (A) And put. Thereafter, cooling water at 0 to 10 ° C. was circulated in the jacket, and the mixture was stirred at 1400 rpm with a disper blade (“TK homodisper 40 type” manufactured by PRIMIX Corporation, diameter: 0.11 m). A sodium hydroxide aqueous solution (160 g) (an amount corresponding to a polymer neutralization degree of 61 mol%) and ion-exchanged water (8285 g) were added, and the mixture was further stirred at 2000 rpm for 15 minutes. Next, 2000 g of “Chromofine Red PR 122” manufactured by DIC was added as a pigment, and the temperature of the mixture in the container was kept at 15 ° C., followed by stirring at 2600 rpm for 7 hours. The obtained mixture was subjected to dispersion treatment for 15 passes at a mixture temperature of 15 ° C. and a pressure of 150 MPa using a “microfluidizer” manufactured by Microfluidics to obtain a dispersion (1). The solid content was 21.4% by mass.
<Step (2)>
Ion-exchanged water (5442 g) was added to 13472 g of the dispersion (1) obtained in the step (1), the solid content was adjusted to 15.2% by mass, and a stirred tank thin film evaporator (manufactured by Kansai Chemical Machinery Manufacturing Co., Ltd.). “Wall Wetter”, container: 45 L). The temperature of the evaporator was set at 54 ° C., the mixture was stirred at 200 rpm, and MEK was removed under a reduced pressure of 10 kPa to obtain an aqueous dispersion (2). The solid content was 25.0% by mass.
<Step (3)>
An epoxy crosslinking agent (manufactured by Nagase ChemteX Corp., trimethylolpropane polyglycidyl ether “Denacol EX321”, epoxy equivalent 129) as a crosslinking agent (C) with respect to 11534 g of the aqueous dispersion (2) obtained in the step (2). 55 g (amount corresponding to a crosslinking rate of 38 mol%), 1216 g of glycerin and 659 g of ion-exchanged water as the polyhydric alcohol (B) were added and mixed, and the resulting dispersion (3) was heated at 90 ° C. The crosslinking treatment was performed by stirring for 5 hours. After cooling to 25 ° C., the mixture was filtered with a filter having a pore diameter of 3 μm to obtain an inkjet recording water dispersion 1 having a solid content of 21.8% by mass and a glycerin content of 9.0% by mass.

(Manufacture of ink 1)
100 g of water dispersion 1 for inkjet recording, 7.7 g of glycerin, 20.6 g of propylene glycol, 13.1 g of 2-pyrrolidone, 0.9 g of “Orphine E1010” manufactured by Nissin Chemical Industry Co., Ltd., 2- 1.9 g of butyl-2-ethyl-1,3-propanediol, 13.1 g of triethylene glycol monobutyl ether, and 30 g of ion-exchanged water were added and mixed. The obtained mixed liquid was filtered through a filter (acetyl cellulose membrane manufactured by Fuji Film Co., Ltd., pore size: 1.2 μm) to prepare ink 1 having a pigment concentration of 8.0% by mass.

Example 2
(Production of water dispersion 2 for inkjet recording)
In the same manner as in Example 1 except that the amount of glycerin added was changed to 676 g and the amount of ion-exchanged water added to 1200 g in the step (3) of Example 1, the solid content was 21.8% by mass and glycerin contained An aqueous dispersion 2 for inkjet recording having an amount of 5.0% by mass was obtained.
(Manufacture of ink 2)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 2 for ink jet recording, the addition amount of glycerin was changed to 11.9 g, and the addition amount of ion exchange water was changed to 26.0 g. Ink 2 was prepared in the same manner as in the production.

Example 3
(Production of water dispersion 3 for inkjet recording)
In the same manner as in Example 1 except that the amount of glycerin added was changed to 270 g and the amount of ion-exchanged water added to 1605 g in the step (3) of Example 1, the solid content was 21.8% by mass and glycerin contained An aqueous dispersion 3 for inkjet recording having an amount of 2.0% by mass was obtained.
(Manufacture of ink 3)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 3 for ink jet recording, the addition amount of glycerin was changed to 14.9 g, and the addition amount of ion exchange water was changed to 23.0 g. Ink 3 was prepared in the same manner as in the production.

Example 4
(Manufacture of water dispersion 4 for inkjet recording)
In the step (3) of Example 1, the solid content was 21.8% by mass and the glycerin content was 9 in the same manner as in Example 1 except that glycerin was changed to propylene glycol as the polyhydric alcohol (B). An aqueous dispersion 4 for inkjet recording of 0.0 mass% was obtained.
(Manufacture of ink 4)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 4 for ink jet recording, the addition amount of glycerin was changed to 16.9 g, and the addition amount of ion exchange water was changed to 11.6 g. Ink 4 was prepared in the same manner as in the production.

Example 5
(Production of water dispersion 5 for inkjet recording)
Ink jet recording having a solid content of 21.8% by mass and a propylene glycol content of 5.0% by mass in the same manner as in Example 2 except that glycerin was changed to propylene glycol in step (3) of Example 2. An aqueous dispersion 5 was obtained.
(Manufacture of ink 5)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 5 for ink jet recording, the addition amount of glycerin was changed to 16.9 g, and the addition amount of ion exchange water was changed to 15.6 g. Ink 5 was prepared in the same manner as in the production.

Example 6
(Production of water dispersion 6 for inkjet recording)
Ink jet recording having a solid content of 21.8% by mass and a propylene glycol content of 2.0% by mass in the same manner as in Example 3 except that glycerin was changed to propylene glycol in step (3) of Example 3. An aqueous dispersion 6 was obtained.
(Manufacture of ink 6)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 6 for ink jet recording, the addition amount of glycerin was changed to 16.9 g, and the addition amount of ion exchange water was changed to 18.6 g. Ink 6 was prepared in the same manner as in the production.

Comparative Example 1
(Production of water dispersion 7 for inkjet recording)
Ink-jet recording water having a solid content of 21.8% by mass in the same manner as in Example 1 except that glycerin was not used and the amount of ion-exchanged water was changed to 1870 g in Step (3) of Example 1. Dispersion 7 was obtained.
(Manufacture of ink 7)
In the production of the ink 1, the ink dispersion 1 of the ink 1 was changed except that the water dispersion 1 for ink jet recording was changed to the water dispersion 7 for ink jet recording, the addition amount of glycerin was changed to 16.9 g, and the addition amount of ion exchange water was changed to 21.1 g. Ink 7 was prepared in the same manner as in the manufacture.

Comparative Example 2
(Production of water dispersion 8 for inkjet recording)
<Step (1)>
In a stainless steel pail container (inner diameter 35 cm) having a jacket on the outer periphery, 1714 g of a 50 mass% solution of the water-insoluble anionic polymer A obtained in Production Example 1, and 1313 g of MEK as an organic solvent (A) Put. Thereafter, 160 g of 5N aqueous sodium hydroxide solution (amount corresponding to the degree of neutralization of the polymer of 61 mol%), ions were circulated while cooling water at 0 to 10 ° C. was circulated in the jacket and stirred at 1400 rpm with the disper blade. 7607 g of exchange water and 676 g of glycerin which is a polyhydric alcohol (B) were added, and the mixture was further stirred at 2000 rpm for 15 minutes. Next, 2000 g of “Chromofine Red PR 122” manufactured by DIC was added as a pigment, and the temperature of the mixture in the container was kept at 15 ° C., followed by stirring at 2600 rpm for 7 hours. The obtained mixture was subjected to dispersion treatment for 15 passes at a mixture temperature of 15 ° C. and a pressure of 150 MPa using a “microfluidizer” manufactured by Microfluidics to obtain a dispersion (1 ′). The solid content was 21.4% by mass.
<Step (2)>
Ion-exchanged water 5442 g was added to 13470 g of the dispersion (1 ′) obtained in the step (1), the solid content was adjusted to 15.2% by mass, and a stirred tank thin film evaporator (Kansai Chemical Machinery Manufacturing Co., Ltd.). "Wall Wetter", container: 45 L). The temperature of the evaporator was set at 54 ° C., the mixture was stirred at 200 rpm, and MEK was removed under a reduced pressure of 10 kPa to obtain a dispersion (2 ′). The solid content was 25.0% by mass.
<Step (3)>
An epoxy crosslinking agent (manufactured by Nagase ChemteX Corp., trimethylolpropane polyglycidyl ether “Denacol EX321”, epoxy equivalent 129) as a crosslinking agent (C) with respect to 11532 g of the dispersion (2 ′) obtained in the step (2). ) Was added and mixed with 1873 g of ion-exchanged water, and the resulting dispersion (3 ′) was stirred at 90 ° C. for 5 hours for crosslinking. . After cooling to 25 ° C., the mixture was filtered with a filter having a pore diameter of 3 μm to obtain an inkjet recording water dispersion 8 having a solid content of 21.8% by mass.

(Manufacture of ink 8)
Ink 2 was prepared in the same manner as in the manufacture of Ink 2 except that the inkjet recording water dispersion 2 was changed to the inkjet recording water dispersion 8 in the manufacture of Ink 2.

Comparative Example 3
(Production of water dispersion 9 for inkjet recording)
A water dispersion for inkjet recording having a solid content of 21.8% by mass, in the same manner as in Comparative Example 2, except that in step (1) of Comparative Example 2, glycerin, which is a polyhydric alcohol (B), was changed to propylene glycol. 9 was obtained.
(Manufacture of ink 9)
Ink 9 was prepared in the same manner as in the manufacture of ink 5 except that the aqueous dispersion 5 for inkjet recording was changed to the aqueous dispersion 9 for inkjet recording in the manufacture of ink 5.

Comparative Example 4
(Production of water dispersion 10 for inkjet recording)
<Step (1)>
Dispersion (1) was obtained in the same manner as in <Step (1)> described in Example 1.
<Step (2)>
To the dispersion (1) 13472 g obtained in the step (1), 4766 g of ion-exchanged water and 676 g of glycerin, which is a polyhydric alcohol (B), are added, and the solid content is adjusted to 15.2% by mass. It was thrown into the type | formula evaporator ("Wall Wetter" by Kansai Chemical Machinery Manufacturing Co., Ltd., container: 45L). The temperature of the evaporator was set at 54 ° C., the mixture was stirred at 200 rpm, and MEK was removed under a reduced pressure of 10 kPa to obtain a dispersion (2 ″). The solid content was 25.0% by mass.
<Step (3)>
Epoxy crosslinking agent (manufactured by Nagase ChemteX Corporation, trimethylolpropane polyglycidyl ether “Denacol EX321”, epoxy equivalent to 11534 g of the dispersion (2 ″) obtained in the step (2). 129) (the amount corresponding to a crosslinking rate of 38 mol%) and 1873 g of ion-exchanged water were added and mixed, and the resulting dispersion (3 ″) was stirred at 90 ° C. for 5 hours for crosslinking treatment. went. After cooling to 25 ° C., the mixture was filtered with a filter having a pore diameter of 3 μm to obtain an inkjet recording water dispersion 10 having a solid content of 21.8% by mass.

(Manufacture of ink 10)
Ink 10 was prepared in the same manner as in the manufacture of Ink 2, except that the inkjet recording water dispersion 2 was changed to the inkjet recording water dispersion 10 in the manufacture of Ink 2.

Comparative Example 5
(Manufacture of water dispersion 11 for inkjet recording)
In Comparative Example 4, an inkjet recording water dispersion 11 having a solid content of 21.8% by mass was obtained in the same manner as in Comparative Example 4 except that glycerin in Step (2) was changed to propylene glycol.
(Manufacture of ink 11)
Ink 5 was produced in the same manner as ink 5 except that ink-jet recording water dispersion 5 was changed to ink-jet recording water dispersion 11 in the production of ink 5.

  The evaluation was performed using the obtained ink. The results are shown in Table 2.

  Inks 1 to 6 produced using the aqueous dispersions of Examples 1 to 6 obtained by the method of the present invention were comparative examples using the aqueous dispersion 7 produced without using the polyhydric alcohol (B). In comparison with the inks 8 to 11 of Comparative Examples 2 to 5 using the water dispersion prepared by mixing the polyhydric alcohol (B) in the stage before the end of the ink 7 of Step 1 and Step (2), It can be seen that an increase in the viscosity of the dry ink due to moisture volatilization is suppressed and the redispersibility is improved. In addition, the inks 1 to 6 of the examples are superior in nozzle returnability as compared with the inks 7 to 11 of the comparative example.

  According to the present invention, there is provided a method for producing an aqueous dispersion for ink jet recording, which can suppress an increase in viscosity of a dry ink when blended in an ink and can provide an ink having excellent nozzle returnability due to good redispersibility. can do.

Claims (6)

The manufacturing method of the aqueous dispersion for inkjet recording which has following process (1)-(3).
Step (1): Step of obtaining a dispersion (1) by dispersing a mixture containing an organic solvent (A), a pigment, a water-insoluble anionic polymer, and water Step (2): Organic from the dispersion (1) Step of removing solvent (A) to obtain aqueous dispersion (2) Step (3): Mixing aqueous dispersion (2), polyhydric alcohol (B) having 2 to 6 carbon atoms and crosslinking agent (C) Cross-linking the water-insoluble anionic polymer in the resulting dispersion (3) to obtain an aqueous dispersion for inkjet recording   The method for producing an aqueous dispersion for inkjet recording according to claim 1, wherein the organic solvent (A) is at least one selected from ketones, alcohols, ethers and esters having 4 to 8 carbon atoms.   The manufacturing method of the water dispersion for inkjet recording of Claim 1 or 2 whose content of the said polyhydric alcohol (B) in a dispersion (3) is 1 mass% or more and 10 mass% or less.   The manufacturing method of the water dispersion for inkjet recording in any one of Claims 1-3 whose said polyhydric alcohol (B) is 1 or more types chosen from C2-C4 diol and glycerol.   The water dispersion for inkjet recording according to any one of claims 1 to 4, wherein an amount of the crosslinking agent (C) used is 0.3 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the water-insoluble anionic polymer. Body manufacturing method. The manufacturing method of the ink for inkjet recording which has the following process (4).
Step (4): A step of further mixing at least one selected from water and an organic solvent (D) into the aqueous dispersion for inkjet recording obtained by the method according to any one of claims 1 to 5.