JP7137211B2 - Aqueous pigment dispersion - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-based pigment dispersion and a method for producing the water-based pigment dispersion.

In the field of commercial printing and industrial printing such as label printing used for product packaging printing and advertisements, PET (polyethylene terephthalate), PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), NY (nylon), etc. 2. Description of the Related Art Solvent-based inks, UV curable inks, etc. have conventionally been used for printing on resin printing media. On the other hand, from the viewpoints of environmental load reduction, energy saving, safety, etc., as printing methods using water-based inks, ink jet recording methods, flexographic printing methods, and gravure printing methods are required.
In addition, from the viewpoint of weather resistance and water resistance of printed matter, water-based inks using pigments as colorants have become mainstream. However, since the resin print medium is non-absorbent and the water-based ink does not permeate the inside of the print medium, the pigment particles contained in the water-based ink remain on the surface of the print medium. Therefore, conventional water-based inks are insufficient in adhesion to the printing medium and scratch resistance, and various attempts have been made to improve these problems.

For example, in Patent Document 1, for the purpose of obtaining a colored film having both light resistance and abrasion resistance and obtaining an aqueous pigment dispersion having excellent storage stability, a pigment and a (meth)acrylic ester are disclosed. An aqueous pigment dispersion containing a resin and a polyurethane resin, wherein the resin component contains a large amount of a (meth)acrylic acid ester resin as a non-volatile matter, and the polyurethane resin has an average dispersed particle diameter within a specific range. Dispersions and the like are disclosed.
In Patent Document 2, for the purpose of providing an aqueous pigment dispersion composition exhibiting excellent dispersibility and the like, and an aqueous ink composition in which the resulting coating film exhibits excellent image density and the like and exhibits excellent gloss, Disclosed are specific aqueous polyurethane dispersion resins, pigment aqueous dispersion compositions comprising pigments and dispersants, and the like.
In Patent Document 3, for the purpose of providing a pigment dispersion or the like having excellent glossiness and storage stability of an ink composition, a pigment, an aqueous medium, a hydrophobic monomer and a hydrophilic monomer are co-prepared. It contains at least a polymer resin, a urethane resin, and a cross-linking agent, and the effective solid content weight ratio of the amount of the cross-linking agent added (amount of cross-linking agent/(copolymer resin of hydrophobic monomer and hydrophilic monomer and urethane resin and the total amount)) is within a specific range.
Patent Document 4 describes water-based inks that have excellent adhesion and glossiness to recording media made of resin such as PET, PVC, PP, and NY, and also have excellent blocking resistance during storage of recording media after printing. It contains polyester resin particles and modified polyolefin resin particles, the resin constituting the polyester resin particles contains an amorphous polyester having a glass transition temperature within a specific range, and the mass ratio of the polyester resin particles to the modified polyolefin resin particles is specified. Water-based inks are disclosed that range from .

JP-A-2004-131586 Japanese Patent Application Laid-Open No. 2013-53200 JP 2005-48016 A JP 2016-222896 A

Here, as in the technique of Patent Document 4, a method of blending a polymer emulsion as a fixing agent into the ink is known as a technique for improving adhesion. However, it has been found that when water-based inks containing a large amount of polymer emulsion are used for non-water-absorbent printing media, the storage stability and print density of the ink tend to decrease.
With the technique disclosed in Patent Document 1, although the adhesion to non-water-absorbing printing media is improved to some extent, high print density cannot be ensured. Although the technique of Patent Document 2 improves the print density when printed on plain paper, it does not satisfy both the adhesion to non-water-absorbing printing media and the print density. In the technique of Patent Document 3, the storage stability of the ink composition is improved, but the adhesion to non-water-absorbing printing media and the printing density are not sufficient. As described above, the demands for improved storage stability, excellent adhesion to non-water-absorbing printing media, and high print density, which have been increasing in recent years, have not yet been met.
The present invention provides a water-based pigment dispersion that has excellent storage stability and, when used in water-based ink, maintains excellent adhesion to a non-water-absorbent printing medium while maintaining high print density, and the production of the water-based pigment dispersion. The object is to provide a method.

Addition of a polymer emulsion to improve the adhesion of the water-based ink can strengthen the adhesion between the pigment particles or between the pigment particles and the printing medium. On the other hand, the storage stability decreases, and after the ink droplets contact the print medium, phase separation occurs between the dispersant of the pigment and the polymer of the emulsion, resulting in local aggregation of the pigment particles. , the smoothness of the coating film surface is lowered, causing a decrease in print density.
Therefore, the present inventors have found that pigment particles can maintain excellent storage stability and, on the other hand, do not locally agglomerate in an environment where the ink vehicle dries on the surface of the printing medium, such as during printing. Aiming to obtain a performance that can firmly maintain the adhesive force between the ink and the print medium, the above problems can be solved by dispersing the pigment with a polymer dispersant containing two different resins.

That is, the present invention relates to the following [1] and [2].
[1] An aqueous pigment dispersion in which a pigment is dispersed in an aqueous medium with a polymer dispersant,
A water-based pigment dispersion, wherein the polymer dispersant contains a (meth)acrylic resin (A) and a polyester resin (B).
[2] A method for producing an aqueous pigment dispersion, comprising steps 1 and 2 below.
Step 1: Process of obtaining a dispersion by dispersing a pigment mixture containing a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin (B) Step 2: Obtained in Step 1 Step of cross-linking the dispersion with a cross-linking agent (C)

According to the present invention, a water-based pigment dispersion having excellent storage stability and having high print density while maintaining excellent adhesion to a non-water-absorbent printing medium by using it in water-based ink, and the water-based pigment dispersion. can provide a manufacturing method of

[Aqueous Pigment Dispersion]
The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion in which a pigment is dispersed in an aqueous medium using a polymer dispersant, the polymer dispersant comprising a (meth)acrylic resin (A) and a polyester resin (B). and
The term "aqueous medium" means a medium in which water accounts for the largest proportion of the medium in which the pigment is dispersed.
The water-based pigment dispersion of the present invention has excellent storage stability and can give good printed matter having excellent adhesion and high print density. It can be suitably used as a water-based pigment dispersion for ink-jet inks, and is particularly preferably used as a water-based pigment dispersion for inkjet inks.

The water-based pigment dispersion of the present invention has excellent storage stability, and when used in water-based inks, both adhesion to non-water-absorbent printing media and print density can be improved. Although the reason is not clear, it is considered as follows.
In the water-based pigment dispersion of the present invention, it is presumed that the pigment is dispersed in the water-based medium while the polymer dispersant is adsorbed or immobilized on the surface of the pigment. By containing the (meth)acrylic resin and the polyester resin in the polymer dispersant, the (meth)acrylic resin stably disperses the pigment in the aqueous medium, and the polyester resin is suitable for non-water-absorbent printing media. It is considered that the adhesion can be improved. Furthermore, the pigment is dispersed with a polymer dispersant containing a (meth)acrylic resin and a polyester resin, and the two types of resins are adsorbed or immobilized on the surface of the pigment. It is presumed that the phase separation of the resin hardly occurs, the surface becomes a smooth coating film, and the printing density is improved.

<Pigment>
Pigments used in the present invention may be either inorganic pigments or organic pigments, and lake pigments and fluorescent pigments may also be used. In addition, if necessary, they can be used in combination with an extender pigment.
Specific examples of inorganic pigments include metal oxides such as carbon black, titanium oxide, iron oxide, red iron oxide and chromium oxide, and pearl luster pigments. Carbon black is particularly preferred for black ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, channel black and the like.
Specific examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; Examples include polycyclic pigments such as linone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments.
The hue is not particularly limited, and achromatic pigments such as white, black and gray; and chromatic pigments such as yellow, magenta, cyan, blue, red, orange and green can be used.
Examples of extender pigments include silica, calcium carbonate, and talc.
The pigments may be used alone or in combination of two or more.

In the present invention, the pigment is a pigment dispersed with a polymer dispersant in an aqueous pigment dispersion, or a polymer dispersant containing a pigment, that is, a polymer particle containing a pigment (hereinafter simply referred to as "pigment-containing polymer particles"). (also called).
The pigment is preferably contained as pigment-containing polymer particles from the viewpoint of storage stability of the aqueous pigment dispersion, adhesion and print density.

<Polymer Dispersant>
The polymer dispersant used in the present invention contains (meth)acrylic resin (A) and polyester resin (B).
The mass ratio of the polyester resin (B) to the (meth)acrylic resin (A) in the water-based pigment dispersion [polyester resin (B)/(meth)acrylic resin (A)] is preferably 0.15 or more, More preferably 0.5 or more, still more preferably 1 or more, still more preferably 1.5 or more, still more preferably 2 or more, and preferably 15 or less, more preferably 10 or less, still more preferably 7 or less , and more preferably 5 or less.
The presence of the polymer dispersant in the aqueous pigment dispersion includes a form in which the polymer dispersant is adsorbed on the pigment, a pigment encapsulation (capsule) form in which the polymer dispersant contains the pigment, and a form in which the polymer dispersant is contained in the pigment. is not adsorbed. From the viewpoint of the dispersion stability of the pigment, in the present invention, the form in which the pigment is contained in the polymer dispersant, that is, the form of pigment-containing polymer particles is preferable, and the pigment-encapsulated state in which the pigment is contained in the polymer dispersant is more preferable.

[(Meth) acrylic resin (A)]
From the viewpoint of dispersion stability of the pigment, the (meth)acrylic resin (A) used in the present invention preferably has an acid group, and at least a portion of the acid group is neutralized with a neutralizing agent. preferably. It is believed that this increases the charge repulsive force that develops after neutralization, suppresses aggregation of the pigment particles in the aqueous pigment dispersion, suppresses thickening, and improves storage stability.
Examples of the acid group include a carboxy group (--COOM ¹ ), a sulfonic _acid group (--SO ₃ M ¹ ), a phosphate group (--OPO ₃ M ¹² ), and the like. or dissociated ionic forms thereof (-COO ^- , -SO ₃ ^- , -OPO ₃ ^2- , -OPO ₃ ^- M ¹ ). In the above chemical formula, M ¹ represents a hydrogen atom, alkali metal, ammonium or organic ammonium. Among these, a carboxy group (--COOM ¹ ) is preferred from the viewpoint of the storage stability of the water-based pigment dispersion, the adhesion and the print density.

The (meth)acrylic resin (A) has an acid value of preferably 50 mgKOH/g or more, more preferably 70 mgKOH/g or more, and preferably 300 mgKOH/g or less, more preferably 270 mgKOH/g or less, and even more preferably is 250 mgKOH/g or less. When the acid value is within the above range, the amount of acid groups and their neutralized acid groups is sufficient to ensure the dispersion stability of the pigment. It is also preferable from the viewpoint of the balance between the affinity between the polymer dispersant and the aqueous medium and the interaction between the polymer dispersant and the pigment.
The acid value of the (meth)acrylic resin (A) can be calculated from the mass ratio of the constituent monomers. It can also be obtained by a method of dissolving or swelling the (meth)acrylic resin (A) in an appropriate organic solvent (eg, methyl ethyl ketone (MEK)) and titrating.

The (meth)acrylic resin (A) used in the present invention comprises (a-1) a carboxy group-containing monomer (hereinafter also referred to as "(a-1) component") and (a-2) a hydrophobic monomer ( A vinyl-based polymer obtained by copolymerizing a monomer mixture A (hereinafter also simply referred to as "monomer mixture A") containing (hereinafter also referred to as "(a-2) component") is preferable. The vinyl polymer has a structural unit derived from component (a-1) and a structural unit derived from component (a-2). The vinyl-based polymer further contains (a-3) a structural unit derived from a macromonomer (hereinafter also referred to as "(a-3) component") and/or (a-4) a nonionic monomer (hereinafter referred to as "(a- 4) may contain structural units derived from (also referred to as "component").

[(a-1) Carboxy Group-Containing Monomer]
(a-1) The carboxy group-containing monomer is preferably used as a monomer component of the (meth)acrylic resin (A) from the viewpoint of improving the dispersion stability of the pigment. A carboxylic acid monomer is used as the carboxyl group-containing monomer (a-1).
Examples of the carboxylic acid monomer include (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2-methacryloyloxymethylsuccinic acid and the like, preferably (meth)acrylic acid. .
As used herein, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid.

[(a-2) Hydrophobic Monomer]
(a-2) The hydrophobic monomer is used as a monomer component of the (meth)acrylic resin (A) from the viewpoint of improving the adsorption of the polymer dispersant to the pigment and improving the dispersion stability of the pigment. is preferred.
As used herein, the term "hydrophobic" means that the amount dissolved in 100 g of deionized water at 25° C. until the monomer is saturated is less than 10 g. (a-2) The dissolved amount of the hydrophobic monomer is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of adsorption of the polymer dispersant to the pigment.
(a-2) The hydrophobic monomer is preferably at least one selected from (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols and aromatic group-containing monomers.
As used herein, "(meth)acrylate" is at least one selected from acrylate and methacrylate.

The (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 1 to 22 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylates having a linear alkyl group such as stearyl (meth)acrylate; isopropyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylates having a branched chain alkyl group such as isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate; alicyclic alkyl such as cyclohexyl (meth)acrylate group-containing (meth)acrylates, and the like. Among these, those having an alkyl group having 1 to 10 carbon atoms are more preferable, and those having an alkyl group having 1 to 8 carbon atoms are more preferable.

The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 or more and 22 or less carbon atoms, which may have a substituent containing a hetero atom. Acrylates are more preferred. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
Styrene-based monomers are preferably styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene and divinylbenzene, more preferably styrene and α-methylstyrene.
As the aromatic group-containing (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate and the like are preferable, and benzyl (meth)acrylate is more preferable.
As the hydrophobic monomer (a-2), two or more of the above monomers may be used, or a styrene-based monomer and an aromatic group-containing (meth)acrylate may be used in combination.

[(a-3) macromonomer]
(a-3) The macromonomer is a compound having a polymerizable functional group at one end and a number average molecular weight of 500 or more and 100,000 or less. It can be used as a monomer component of A). The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, more preferably a methacryloyloxy group.
(a-3) The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured by gel permeation chromatography using chloroform containing 1 mmol/L of dodecyldimethylamine as a solvent, using polystyrene as a standard substance.
From the viewpoint of the dispersion stability of the pigment, the (a-3) macromonomer is preferably an aromatic group-containing monomer-based macromonomer or a silicone-based macromonomer, more preferably an aromatic group-containing monomer-based macromonomer.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomers described in (a-2) Hydrophobic monomer, preferably styrene and benzyl (meth)acrylate, Styrene is more preferred.
Specific examples of commercially available styrenic macromonomers include AS-6(S), AN-6(S), HS-6(S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of silicone-based macromonomers include organopolysiloxanes having a polymerizable functional group at one end.

[(a-4) nonionic monomer]
(a-4) The nonionic monomer can be used as a monomer component of the (meth)acrylic resin (A) from the viewpoint of the dispersion stability of the pigment.
(a-4) Nonionic monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; polypropylene glycol (n = 2 to 30, n is oxypropylene Shows the average number of added moles of the group.N below indicates the average number of added moles of the oxyalkylene group.) Polyalkylene glycols such as (meth)acrylate, polyethylene glycol (n = 2 to 30) (meth)acrylate ( meth) acrylate; alkoxypolyalkylene glycol (meth) acrylate such as methoxypolyethylene glycol (n = 1 to 30) (meth) acrylate; phenoxy (ethylene glycol/propylene glycol copolymerization) (n = 1 to 30, ethylene Glycol: n=1 to 29) (meth)acrylate and the like. Among these, polypropylene glycol (n = 2 to 30) (meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymerization) (meth) acrylate is preferable, and polypropylene glycol (n = 2 to 30) (meth) acrylate is preferable. more preferred.
Specific examples of the commercially available component (a-4) include NK Ester M-20G, 40G, 90G, 230G, etc. of Shin-Nakamura Chemical Co., Ltd., and Brenmer PE-90 of NOF Corporation. , 200, 350, etc., PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50PEP-300, 50POEP-800B, 43PAPE -600B and the like.

Each of the components (a-1) to (a-4) can be used alone or in combination of two or more.
As described above, the (meth)acrylic resin (A) used in the present invention contains one or more (a-1) carboxy groups selected from acrylic acid and methacrylic acid, from the viewpoint of improving the dispersion stability of the pigment. Containing a structural unit derived from a contained monomer and one or more (a-2) hydrophobic monomer-derived structural units selected from (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol and aromatic group-containing monomers It may be a vinyl polymer containing (a-3) a structural unit derived from a macromonomer and (a-4) a structural unit derived from a nonionic monomer.

(Content of each component in monomer mixture A or content of each structural unit in (meth)acrylic resin (A))
Contents of (a-1) and (a-2) components in monomer mixture A (contents as unneutralized amounts; the same shall apply hereinafter) or (meth) at the time of production of (meth)acrylic resin (A) From the viewpoint of improving the dispersion stability of the pigment, the contents of the structural units derived from the components (a-1) and (a-2) in the acrylic resin (A) are as follows.
The content of component (a-1) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and preferably 75% by mass or less, more preferably 60% by mass. % or less, more preferably 50 mass % or less.
The content of component (a-2) is preferably 25% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass. % or less, more preferably 75 mass % or less.

Further components (a-1) to (a-4) during the production of (meth)acrylic resin (A) when containing structural units derived from components (a-3) and/or (a-4) The content in the monomer mixture A or the content of structural units derived from components (a-1) to (a-4) in the (meth)acrylic resin (A) improves the dispersion stability of the pigment. From the point of view, it is as follows.
The content of component (a-1) is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and preferably 30% by mass or less, more preferably 28% by mass. % or less, more preferably 25 mass % or less.
The content of component (a-2) is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and preferably 65% by mass or less, more preferably 60% by mass. % or less, more preferably 55 mass % or less.
When component (a-3) is contained, the content of component (a-3) is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 8% by mass or more, and preferably is 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less.
When component (a-4) is contained, the content of component (a-4) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably is 40% by mass or less, more preferably 35% by mass or less, and still more preferably 30% by mass or less.

The mass ratio of [(a-1) component/(a-2) component] is preferably 0.1 or more, more preferably 0.15 or more, still more preferably 0.25 or more, and preferably 3 Below, more preferably 2 or less, still more preferably 1 or less, and even more preferably 0.5 or less.
Further, when the (a-3) component is contained, the mass ratio of [(a-1) component / [(a-2) component + (a-3) component]] is preferably 0.03 or more, more preferably 0.05 or more, more preferably 0.1 or more, and preferably 1 or less, more preferably 0.8 or less, still more preferably 0.6 or less, and even more preferably 0.5 or less .

(Production of (meth)acrylic resin (A))
The (meth)acrylic resin (A) is produced by copolymerizing the monomer mixture A by a known polymerization method such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferred.
Solvents used in the solution polymerization method are not particularly limited, but polar organic solvents are preferred. If the polar organic solvent has water miscibility, it can be used by mixing with water. Examples of polar organic solvents include aliphatic alcohols having 1 to 3 carbon atoms, ketones having 3 to 5 carbon atoms, ethers, and esters such as ethyl acetate. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these with water is preferable, and methyl ethyl ketone or a mixed solvent of it and water is preferable.
A polymerization initiator and a polymerization chain transfer agent can be used in the polymerization.
Examples of polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile), t-butyl peroxyoctoate, benzoyl peroxide, and the like. A known radical polymerization initiator such as an organic peroxide of 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 1 mol of the monomer mixture A.
As the polymerization chain transfer agent, known chain transfer agents such as mercaptans such as octylmercaptan and 2-mercaptoethanol, and thiuram disulfides can be used.
Moreover, there is no restriction on the chain mode of the polymerization monomers, and any polymerization mode such as random, block, or graft may be used.

Preferred polymerization conditions vary depending on the type of polymerization initiator, monomer, solvent, etc. used, but usually the polymerization temperature is preferably 30° C. or higher, more preferably 50° C. or higher, and preferably 95° C. or lower. It is more preferably 80° C. or lower. The polymerization time is preferably 1 hour or more, more preferably 2 hours or more, and preferably 20 hours or less, more preferably 10 hours or less. 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 can be isolated from the reaction solution by known methods such as reprecipitation and solvent distillation. The obtained polymer can be purified by removing unreacted monomers and the like by reprecipitation, membrane separation, chromatography, extraction, or the like.

The number average molecular weight of the (meth)acrylic resin (A) used in the present invention is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 8,000 or more, and preferably 100 ,000 or less, more preferably 80,000 or less, and even more preferably 60,000 or less. When the number average molecular weight of the (meth)acrylic resin (A) is within the above range, the adsorptive power to the pigment is sufficient and dispersion stability can be exhibited.
The number average molecular weight can be measured by the method described in Examples.

[Polyester resin (B)]
The polyester resin (B) used in the present invention contains an alcohol component-derived structural unit and a carboxylic acid component-derived structural unit, and can be obtained by polycondensing the alcohol component and the carboxylic acid component.

(alcohol component)
The alcohol component, which is a raw material monomer of the polyester resin (B), preferably contains an aromatic diol from the viewpoint of pigment dispersibility and adhesion to a printing medium. As the aromatic diol, an alkylene oxide adduct of bisphenol A is preferred. The alkylene oxide adduct of bisphenol A means the entire structure obtained by adding an oxyalkylene group to 2,2-bis(4-hydroxyphenyl)propane.
Specifically, the alkylene oxide adduct of bisphenol A is preferably a compound represented by the following general formula (I).

In general formula (I), both OR ¹ and R ² O are oxyalkylene groups, preferably each independently an oxyalkylene group having 1 to 4 carbon atoms, more preferably an oxyethylene group or oxypropylene is the base.
x and y correspond to the number of moles of alkylene oxide added. Furthermore, from the viewpoint of reactivity with the carboxylic acid component, the average value of the sum of x and y is preferably 2 or more, and is preferably 7 or less, more preferably 5 or less, and still more preferably 3 or less. .
Moreover, the x number of OR ¹ and the y number of R ² O may be the same or different, but from the viewpoint of adhesion to the print medium, they are preferably the same. The alkylene oxide adducts of bisphenol A may be used alone or in combination of two or more. The alkylene oxide adduct of bisphenol A is preferably a propylene oxide adduct of bisphenol A and an ethylene oxide adduct of bisphenol A, more preferably a propylene oxide adduct of bisphenol A.
The content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol%, from the viewpoint of pigment dispersibility and adhesion to a printing medium. It is mol % or more, and its upper limit is preferably 100 mol % or less.

In addition to the alkylene oxide adduct of bisphenol A, the alcohol component, which is the raw material monomer of the polyester resin (B), may contain the following other alcohol components. For example, ethylene glycol, propylene glycol (1,2-propanediol), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or their alkylene (2 to 4 carbon atoms) oxide adduct (average addition number of moles is 1 or more and 16 or less).
The other alcohol components may be used alone or in combination of two or more.

(Carboxylic acid component)
Carboxylic acid components, which are raw material monomers of the polyester resin (B), include carboxylic acids, anhydrides of these acids, and alkyl (having 1 or more and 3 or less carbon atoms) esters thereof.
As the carboxylic acid component, an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, and a polyvalent carboxylic acid having a valence of 3 or more are preferable. from the viewpoint of, aromatic dicarboxylic acids and aliphatic dicarboxylic acids are more preferred, and aliphatic dicarboxylic acids are even more preferred.
As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.
The aliphatic dicarboxylic acids include unsaturated aliphatic dicarboxylic acids and saturated aliphatic dicarboxylic acids, with unsaturated aliphatic dicarboxylic acids being preferred. Preferred unsaturated aliphatic dicarboxylic acids are fumaric acid and maleic acid, more preferred are fumaric acid, and preferred saturated aliphatic dicarboxylic acids are adipic acid and succinic acid.
Cyclohexanedicarboxylic acid, decalinedicarboxylic acid, and tetrahydrophthalic acid are preferred as alicyclic dicarboxylic acids, and trimellitic acid and pyromellitic acid are preferred as trivalent or higher polyvalent carboxylic acids.
The carboxylic acid component can be used alone or in combination of two or more.

(Production of polyester resin (B))
The polyester resin (B) can be obtained by appropriately combining the alcohol component and the carboxylic acid component and subjecting them to polycondensation. For example, it can be produced by polycondensing the alcohol component and the carboxylic acid component in an inert gas atmosphere at a temperature of 130° C. or higher and 250° C. or lower using an esterification catalyst as necessary. .
Examples of the esterification catalyst include metal compounds such as tin catalysts, titanium catalysts, antimony trioxide, zinc acetate and germanium dioxide. A tin catalyst is preferable from the viewpoint of the reaction efficiency of the esterification reaction in the synthesis of polyester. Preferred tin catalysts include dibutyltin oxide, tin (II) di(2-ethylhexane)ate, salts thereof, and the like. If necessary, an esterification co-catalyst such as 3,4,5-trihydroxybenzoic acid (gallic acid) may be used.
Radical polymerization inhibitors such as 4-tert-butylcatechol and hydroquinone may also be used in combination.

The softening point of the polyester resin (B) is preferably 80° C. or higher, more preferably 85° C. or higher, still more preferably 90° C. or higher, and preferably 170° C. or lower, from the viewpoint of adhesion to the print medium. It is more preferably 145° C. or lower, still more preferably 125° C. or lower.
The glass transition temperature (Tg) of the polyester resin (B) is preferably 50° C. or higher, more preferably 55° C. or higher, and preferably 95° C. or lower, more preferably 95° C. or lower, from the viewpoint of adhesion to the print medium. It is 90° C. or lower, more preferably 85° C. or lower, and even more preferably 80° C. or lower.
The polyester resin (B) preferably has acid groups. The acid value of the polyester resin (B) is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, still more preferably 15 mgKOH/g or more, from the viewpoint of adhesion to a printing medium. It is 40 mgKOH/g or less, more preferably 37 mgKOH/g or less, still more preferably 35 mgKOH/g or less.
Any desired softening point, glass transition temperature, and acid value can be obtained by appropriately adjusting the type of monomers used, the compounding ratio, the polycondensation temperature, and the reaction time.

<Crosslinking agent (C)>
In the present invention, at least the (meth)acrylic resin (A) is preferably crosslinked with a crosslinking agent (C) from the viewpoints of storage stability of the aqueous pigment dispersion, adhesion and print density.
The cross-linking agent (C) used in the present invention has the viewpoint of efficiently reacting with the (meth)acrylic resin (A) in a medium mainly containing water, the storage stability of the aqueous pigment dispersion, and the adhesion and printing. From the viewpoint of concentration, the water solubility (mass ratio) of the cross-linking agent (C) is preferably 50% or less, more preferably 40% or less, and still more preferably 35% or less. Here, the water solubility % (mass ratio) refers to the dissolution rate (%) when 10 parts by mass of the cross-linking agent (C) is dissolved in 90 parts by mass of water at room temperature of 25°C.

When the (meth)acrylic resin (A) has an acid group, the crosslinkable functional group of the crosslinker (C) is preferably an epoxy group. The cross-linking agent (C) is preferably a compound having two or more epoxy groups in the molecule, more preferably a compound having a glycidyl ether group, and still more preferably a polyhydric alcohol having a hydrocarbon group having 3 to 8 carbon atoms. is a polyglycidyl ether compound.
The molecular weight of the cross-linking agent (C) is preferably 120 or more, more preferably 150 or more, still more preferably 200 or more, and preferably 2000, from the viewpoint of easiness of reaction and storage stability of the aqueous pigment dispersion. Below, more preferably 1500 or less, and still more preferably 1000 or less.
The epoxy equivalent of the cross-linking agent (C) is preferably 90 or more, more preferably 100 or more, still more preferably 110 or more, and preferably 300 or less, more preferably 200 or less, still more preferably 150 or less.
The number of epoxy groups in the cross-linking agent (C) is 2 or more per molecule, and preferably 6 or less per molecule, from the viewpoint of efficiently reacting with acid groups to enhance the storage stability of the aqueous pigment dispersion. , more preferably 4 or less, still more preferably 3 or less, from the viewpoint of market availability.

Specific examples of the cross-linking agent (C) include polypropylene glycol diglycidyl ether (water solubility: 31%), glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether (water solubility: 27%), and sorbitol polyglycidyl. Polyglycidyl ether such as ether, pentaerythritol polyglycidyl ether (water content 0%), resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether, etc. are mentioned. Among these, one or more selected from trimethylolpropane polyglycidyl ether and pentaerythritol polyglycidyl ether is preferable.

The degree of crosslinking [the number of molar equivalents of the crosslinkable functional group of the crosslinking agent (C)/the number of molar equivalents of the acid group of the (meth)acrylic resin (A)] determines the storage stability of the water-based pigment dispersion, as well as the adhesion and From the viewpoint of print density, it is preferably 0.12 or more, more preferably 0.16 or more, still more preferably 0.2 or more, and preferably 0.65 or less, more preferably 0.5 or less, and still more preferably is 0.4 or less, more preferably 0.3 or less.
The degree of cross-linking in the present invention is an apparent degree of cross-linking calculated from the equivalent weight of the acid value of the (meth)acrylic resin (A) and the cross-linking functional group of the cross-linking agent (C).
When the polyester resin (B) has an acid group, a crosslinked structure is also formed between the acid group of the polyester resin (B) and the crosslinking agent (C). From the viewpoint of controlling the storage stability of the aqueous pigment dispersion and improving the adhesion and print density, the crosslinkability of the crosslinker (C) with respect to the number of molar equivalents of the acid group of the (meth)acrylic resin (A) The ratio of molar equivalents of functional groups is used as an index of the degree of cross-linking.
In the present invention, from the viewpoint of the storage stability of the water-based pigment dispersion, and the adhesion and print density, the (meth)acrylic resin (A) is neutralized with a neutralizing agent described later. ) is partially neutralized to disperse the pigment, and further a part of the acid groups of the (meth)acrylic resin (A) is crosslinked with a crosslinking agent (C). It is preferably an aqueous pigment dispersion in which a pigment is dispersed in an aqueous medium with a structured and crosslinked polymer dispersant (hereinafter also referred to as "crosslinked polymer dispersant").

In the water-based pigment dispersion of the present invention, both the (meth)acrylic resin (A) and the polyester resin (B) contain acid groups from the viewpoint of the storage stability of the water-based pigment dispersion and the adhesion and print density. It is preferable to have In this case, it is more preferable that some of the acid groups of the (meth)acrylic resin (A) and the polyester resin (B) are crosslinked with the crosslinking agent (C). As a result, part of the acid groups of each of the (meth)acrylic resin (A) and the polyester resin (B) constituting the polymer dispersant are crosslinked with the crosslinking agent (C), and the (meth)acrylic resin (A ) Between chains, between polyester resin (B) chains, and between (meth)acrylic resin (A) chains and polyester resin (B) chains are crosslinked via a crosslinking agent (C) to form a crosslinked structure. It is believed that the dispersion stability of the pigment by the polymer dispersant is improved, and the storage stability, adhesion and print density are improved.
In the water-based pigment dispersion of the present invention, the polymer dispersant has three or more branched structures represented by the following formula (1) as a crosslinked structure from the viewpoints of storage stability, adhesion and print density of the water-based pigment dispersion. It is preferred to have

（式（１）中、Ｘは下記式（２）又は（３）で表される基を示し、Ａは、Ｘで表される基又はエチル基を示す。）

(In formula (1), X represents a group represented by the following formula (2) or (3), and A represents a group represented by X or an ethyl group.)

（式（２）中、Ｐは（メタ）アクリル系樹脂（Ａ）の分子鎖又はポリエステル樹脂（Ｂ）の分子鎖を示し、＊は式（１）中の第４級炭素原子との結合部位を示す。）

(In the formula (2), P represents the molecular chain of the (meth)acrylic resin (A) or the molecular chain of the polyester resin (B), * is the bonding site with the quaternary carbon atom in the formula (1) indicates.)

（式（３）中、Ｐ及び＊は前記と同様である。）

(In formula (3), P and * are the same as above.)

The mass ratio of the pigment in the total solid content of the aqueous pigment dispersion [pigment/(total solid content of the aqueous pigment dispersion)] is the storage stability of the aqueous pigment dispersion, and the adhesion, print density and productivity. Therefore, it is preferably 0.25 or more, more preferably 0.3 or more, still more preferably 0.35 or more, and preferably 0.85 or less, more preferably 0.75 or less, still more preferably 0.65 Below, more preferably 0.55 or less.
The mass ratio of the pigment to the total amount of the pigment and (meth)acrylic resin (A) in the aqueous pigment dispersion [pigment/[pigment + (meth)acrylic resin (A)]] is the From the viewpoint of storage stability, adhesion, print density and productivity, it is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, and preferably 0.95 or less. , more preferably 0.9 or less, and still more preferably 0.85 or less.

[Method for producing aqueous pigment dispersion]
The water-based pigment dispersion of the present invention can be prepared by a method of dispersing a mixture containing a pigment, a (meth)acrylic resin (A), and a polyester resin (B), or a method of dispersing a mixture containing a pigment and a (meth)acrylic resin ( It can be produced by a method in which either one of A) and polyester resin (B) is dispersed, and then the other is added.
The (meth)acrylic resin (A) and the polyester resin (B) may each be used as a dispersion in which polymer particles are dispersed in an aqueous medium, and may contain a dispersant such as a surfactant as necessary. may be The dispersion may be appropriately synthesized or may be a commercially available product.
Commercially available dispersions of (meth)acrylic resin (A) include, for example, “Joncryl 390”, “Joncryl 7100”, “Joncryl 734”, “Joncryl 538” (manufactured by BASF Japan Ltd.) , trade name) and vinyl chloride-acrylic resin dispersions such as "Vinyblan 701" (manufactured by Nissin Chemical Industry Co., Ltd., trade name).
Commercially available dispersions of the polyester resin (B) include, for example, "Elitel KA-5034", "Elitel KA-5071S", "Elitel KZA-1734", "Elitel KZA-6034", "Elitel KZA-1449", "Elitel KZA-0134" and "Elitel KZA-3556" (manufactured by Unitika Ltd., trade names).

When the (meth)acrylic resin (A) has an acid group, the water-based pigment dispersion of the present invention is prepared by a method having the following step 1 from the viewpoint of storage stability, adhesion, print density and productivity. , is preferably produced efficiently.
Step 1: A step of dispersing a pigment mixture containing a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin (B) to obtain a dispersion.

(Step 1)
From the viewpoint of storage stability, adhesion and print density, the aqueous pigment dispersion of the present invention is preferably produced by a method having the following steps 1-1 and 1-2 before step 1.
Step 1-1: A step of dispersing a pigment in a (meth)acrylic resin (A) having an acid group to obtain a preliminary dispersion Step 1-2: A polyester resin is added to the preliminary dispersion obtained in Step 1-1 A step of adding the emulsion of (B) to obtain a pigment mixture containing a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin (B)

[Step 1-1]
In step 1-1, first, a (meth)acrylic resin (A) having an acid group is dissolved in an organic solvent, and then a pigment, water, and, if necessary, a neutralizer, a surfactant, etc. are obtained. A preferred method is to obtain an oil-in-water type dispersion by adding to and mixing with the obtained organic solvent solution. The order of addition to the organic solvent solution of the (meth)acrylic resin (A) is not particularly limited, but it is preferable to add water, the neutralizer, and the pigment in this order.
The organic solvent for dissolving the (meth)acrylic resin (A) is not limited, but aliphatic alcohols having 1 to 3 carbon atoms, ketones, ethers, esters, etc. are preferable, and wettability to pigments, ( From the viewpoint of improving the solubility of the meth)acrylic resin (A) and the adsorption of the (meth)acrylic resin (A) to the pigment, ketones having 4 to 8 carbon atoms are more preferable, such as methyl ethyl ketone and methyl isobutyl. More preferred are ketones, and even more preferred is methyl ethyl ketone. When the (meth)acrylic resin (A) is synthesized by a solution polymerization method, the solvent used in the polymerization may be used as it is.

(neutralization)
Part of the acid groups of the (meth)acrylic resin (A) should be neutralized with a neutralizing agent from the viewpoint of the storage stability of the aqueous pigment dispersion, as well as the adhesion, print density and productivity. is preferred. When neutralizing, it is preferable to neutralize so that the pH becomes 7 or more and 11 or less.
Examples of neutralizing agents include alkali metal hydroxides and ammonia. Alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide, with sodium hydroxide and potassium hydroxide being preferred. The neutralizing agent is preferably an alkali metal hydroxide from the viewpoint of the storage stability of the water-based pigment dispersion, the adhesion and the print density. Also, the (meth)acrylic resin (A) may be neutralized in advance.
The neutralizing agent is preferably used as an aqueous neutralizing agent solution from the viewpoint of promoting neutralization sufficiently and uniformly. From the same viewpoint as above, the concentration of the neutralizing agent aqueous solution is preferably 3% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 50% by mass or less. Preferably, it is 25% by mass or less.
The use equivalent of the neutralizing agent is preferably 10 mol % or more, more preferably 30 mol % or more, and still more preferably 50 mol % or more, from the viewpoints of the storage stability of the aqueous pigment dispersion, the adhesion and the print density. Also, it is preferably 80 mol % or less, more preferably 75 mol % or less.
Here, the use equivalent of the neutralizing agent can be determined by the following formula. When the use equivalent of the neutralizing agent is 100 mol% or less, it is synonymous with the degree of neutralization. It means that it is excessive with respect to the acid groups of the resin (A), and the degree of neutralization of the (meth)acrylic resin (A) at this time is regarded as 100 mol %.
Use equivalent of neutralizing agent (mol%) = [{neutralizing agent added mass (g) / equivalent of neutralizing agent} / [{acid value of (meth)acrylic resin (A) (mgKOH / g) × Mass (g) of (meth)acrylic resin (A)}/(56×1,000)]]×100

(Content of each component in preliminary dispersion)
The content of each component in the preliminary dispersion is as follows from the viewpoint of storage stability of the aqueous pigment dispersion, adhesion, print density and productivity.
The content of the pigment in the preliminary dispersion in step 1-1 is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and preferably 45% by mass or less, It is more preferably 40% by mass or less, still more preferably 35% by mass or less.
The content of the (meth)acrylic resin (A) in the preliminary dispersion in step 1-1 is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and , preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.
The content of the organic solvent in the preliminary dispersion in step 1-1 is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, and preferably 30% by mass or less. , more preferably 25% by mass or less, and still more preferably 20% by mass or less.
The content of water in the preliminary dispersion in step 1-1 is preferably 35% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, and preferably 80% by mass or less, More preferably 70 mass % or less, still more preferably 60 mass % or less.

The mass ratio of the pigment to the total amount of the pigment and (meth)acrylic resin (A) in the preliminary dispersion [pigment/[pigment + (meth)acrylic resin (A)]] is the storage of the aqueous pigment dispersion. From the viewpoints of stability, adhesion, print density and productivity, it is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, and preferably 0.95 or less. It is more preferably 0.9 or less, still more preferably 0.85 or less.

In step 1-1, there is no particular limitation on the method of dispersing the predispersion, and generally used mixing and stirring devices such as anchor blades and disper blades can be used. Among them, a high-speed stirring mixer is preferable.
The temperature of the dispersion treatment in step 1-1 is preferably 0° C. or higher, and preferably 40° C. or lower, more preferably 30° C. or lower, and even more preferably 25° C. or lower.
The dispersion time in step 1-1 is preferably 0.5 hours or longer, and preferably 30 hours or shorter, more preferably 10 hours or shorter, even more preferably 5 hours or shorter, and even more preferably 3 hours or shorter.

[Step 1-2]
In step 1-2, an emulsion of a polyester resin (B) is added to the preliminary dispersion obtained in step 1-1 to obtain a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin. (B) is a step of obtaining a pigment mixture containing (B).
The polyester resin (B) emulsion is obtained by dispersing polyester resin (B) particles in an aqueous medium. A dispersing agent such as a surfactant may be included if desired. The emulsion of the polyester resin (B) improves adhesion to the printing medium and also acts as a fixing emulsion for obtaining printed matter with high print density.

The emulsion of the polyester resin (B) can be prepared by adding the polyester resin (B) to an aqueous medium and performing a dispersion treatment using a disperser or the like, or by gradually adding the aqueous medium to the polyester resin (B) and subjecting it to phase inversion emulsification. etc. Among them, the method using phase inversion emulsification is preferable from the viewpoint of improving the adhesion to the printing medium and obtaining a printed matter with high print density. Examples of the phase inversion emulsification method include the method described in JP-A-2016-222896. First, the polyester resin (B) is dissolved in an organic solvent, and then an aqueous medium is added to the solution to effect phase inversion. and then removing the organic solvent is preferred.

The content of the polyester resin (B) particles in the emulsion of the polyester resin (B) determines the dispersion stability of the emulsion of the polyester resin (B), storage stability of the aqueous pigment dispersion, adhesion, printing density and productivity. From the viewpoint of, preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass % by mass or less.

(Content of each component in the pigment mixture)
The content of each component in the pigment mixture is as follows from the viewpoint of storage stability of the aqueous pigment dispersion, adhesion, print density and productivity.
The content of the pigment in the pigment mixture is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass. 15% by mass or less, more preferably 15% by mass or less.
The content of the (meth)acrylic resin (A) in the pigment mixture is preferably 1% by mass or more, more preferably 1.5% by mass or more, still more preferably 2% by mass or more, and preferably 20% by mass or more. % by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.
The content of the polyester resin (B) in the pigment mixture is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably is 20% by mass or less, more preferably 15% by mass or less.
The content of the organic solvent in the pigment mixture is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass. % or less, more preferably 20 mass % or less.
The water content in the pigment mixture is preferably 35% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass. 70% by mass or less, more preferably 70% by mass or less.
The mass ratio of the polyester resin (B) to the (meth)acrylic resin (A) in the pigment mixture [polyester resin (B)/(meth)acrylic resin (A)] is preferably 0.15 or more, more preferably is 0.5 or more, more preferably 1 or more, even more preferably 1.5 or more, still more preferably 2 or more, and preferably 15 or less, more preferably 10 or less, still more preferably 7 or less, and more More preferably, it is 5 or less.

The dispersion treatment of the pigment mixture is preferably carried out by applying a shearing stress to control the average particle size of the pigment particles to a desired particle size.
Examples of means for imparting shear stress include kneaders such as roll mills and kneaders, high-pressure homogenizers such as Microfluidizer (manufactured by Microfluidic), media-type dispersers such as paint shakers and bead mills. Commercially available media-type dispersers include Ultra Apex Mill (manufactured by Kotobuki Kogyo Co., Ltd.) and Pico Mill (manufactured by Asada Iron Works Co., Ltd.). A plurality of these devices can also be combined. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment.
When dispersion treatment is performed using a high-pressure homogenizer, the pigment can be controlled to have a desired particle size by controlling the treatment pressure and the number of passes.
The treatment pressure is preferably 60 MPa or higher, more preferably 100 MPa or higher, still more preferably 150 MPa or higher, and preferably 300 MPa or lower, more preferably 250 MPa or lower, from the viewpoint of productivity and economy.
The number of passes is preferably 3 or more, more preferably 7 or more, and is preferably 30 or less, more preferably 20 or less.

In Step 1, it is preferable to obtain an aqueous pigment dispersion by further removing the organic solvent from the dispersion by a known method. The organic solvent in the resulting aqueous pigment dispersion is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. The amount of residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.
In addition, if necessary, the dispersion can be heated and stirred before distilling off the organic solvent.

(Step 2)
From the viewpoint of storage stability, adhesion and print density, the water-based pigment dispersion of the present invention preferably has the following step 2 in addition to step 1.
Step 2: Step of cross-linking the dispersion obtained in Step 1 using a cross-linking agent (C) From Step 2, an aqueous pigment dispersion in which the pigment is dispersed in an aqueous medium with a cross-linked polymer dispersant is obtained.
In the present invention, in step 1, some of the acid groups of the (meth)acrylic resin (A) are neutralized to disperse the pigment to obtain a dispersion, and in step 2, the (meth) ) A water-based pigment dispersion in which a part of the acid groups of the acrylic resin (A) is reacted with the cross-linking agent (C) to form a cross-linked structure, and the pigment is dispersed in the water-based medium with a cross-linked polymer dispersant. is preferred.
Furthermore, as described above, when both the (meth)acrylic resin (A) and the polyester resin (B) have an acid group, the (meth)acrylic resin (A) and the polyester resin ( A portion of each acid group of B) is crosslinked with a crosslinking agent (C) to form (meth)acrylic resin (A) interchains, polyester resin (B) interchains and (meth)acrylic resin (A) chains and the polyester resin (B) chain are crosslinked with the crosslinking agent (C) to form a crosslinked structure.

(Crosslinking reaction)
In step 2, the dispersion obtained in step 1 and the cross-linking agent (C) are preferably mixed and subjected to a cross-linking treatment.
The amount of the cross-linking agent (C) used in step 2 is the ratio of the number of molar equivalents of the crosslinkable functional group of the cross-linking agent (C) to the number of molar equivalents of the acid group of the (meth)acrylic resin (A), and the water-based pigment From the viewpoints of storage stability of the dispersion, adhesion and print density, it is preferably 0.12 or more, more preferably 0.16 or more, still more preferably 0.2 or more, and preferably 0.65 or less. , more preferably 0.5 or less, still more preferably 0.4 or less, and even more preferably 0.3 or less.

The time for the cross-linking treatment is preferably 0.5 hours or longer, more preferably 1 hour or longer, still more preferably 1.5 hours or longer, and even more preferably 3 hours or longer, from the viewpoint of completion of the cross-linking reaction and economy. , and preferably 12 hours or less, more preferably 10 hours or less, even more preferably 8 hours or less, and even more preferably 5 hours or less.
The temperature of the cross-linking treatment is preferably 40° C. or higher, more preferably 50° C. or higher, still more preferably 60° C. or higher, still more preferably 70° C. or higher, and preferably 95° C. or lower, from the same viewpoint as described above. , more preferably 90° C. or less.

The water-based pigment dispersion of the present invention may contain 1% by mass or more and 10% by mass or less of glycerin, triethylene glycol, or the like as a moisturizing agent to prevent drying, and may contain additives such as antifungal agents. may The additive may be added when the pigment is dispersed, or may be added after the pigment is dispersed or after the crosslinking reaction.

The aqueous pigment dispersion of the present invention preferably comprises pigment-containing polymer particles dispersed in an aqueous medium containing water as the main medium. Here, the form of the pigment-containing polymer particles is not particularly limited as long as the particles are formed from at least the pigment and the polymer. That is, it is sufficient that particles are formed from at least the pigment, the (meth)acrylic resin (A), and the polyester resin (B). For example, it includes a particle form in which the pigment is encapsulated in the polymer, a particle form in which the pigment is uniformly dispersed in the polymer, a particle form in which the pigment is exposed on the particle surface of the polymer, and a mixture thereof.
Furthermore, the resulting aqueous pigment dispersion takes the form of pigment-containing polymer particles and the polyester resin (B) dispersed in an aqueous medium, that is, the pigment-free resin (B) particles. may be

The non-volatile component concentration (solid content concentration) of the water-based pigment dispersion of the present invention is preferably 10% by mass or more, more preferably 10% by mass or more, from the viewpoint of improving the dispersion stability of the dispersion and facilitating the preparation of the water-based ink. is 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less.
The solid content concentration of the water-based pigment dispersion is measured by the method described in Examples.
The average particle diameter of the pigment-containing polymer particles in the water-based pigment dispersion is to reduce coarse particles, and from the viewpoint of storage stability, adhesion and print density, and when used as a water-based pigment dispersion for inkjet recording, water-based ink From the viewpoint of improving the ejection stability, it is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 70 nm or more, and preferably 200 nm or less, more preferably 160 nm or less, and still more preferably 150 nm or less.
The average particle size of the aqueous pigment dispersion, preferably the average particle size of the pigment-containing polymer particles, is measured by the method described in Examples.
The average particle diameter of the pigment-containing polymer particles in the water-based ink is the same as the average particle diameter in the water-based pigment dispersion. is the same as

[Water-based ink]
The water-based pigment dispersion of the present invention is preferably used by being contained in water-based ink (hereinafter also referred to as "water-based ink" or "ink"). This makes it possible to improve the storage stability of the water-based ink, as well as the adhesion to non-water-absorbing printing media and the print density. The water-based pigment dispersion of the present invention can be used as a water-based ink as it is, but from the viewpoint of improving the storage stability, adhesion and print density of the water-based ink, it is preferable to further contain an organic solvent. The organic solvent preferably contains one or more organic solvents having a boiling point of 90° C. or higher. The weighted average boiling point of the organic solvent is preferably 150° C. or higher, more preferably 180° C. or higher, and is preferably 240° C. or lower, more preferably 220° C. or lower, and still more preferably 200° C. or lower.
Examples of the organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Among these, one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers are preferred, and selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane and diethylene glycol diethyl ether. One or more are more preferred, and propylene glycol is even more preferred.

From the viewpoint of improving adhesion and printing density, the water-based ink may further contain an aqueous dispersion of polymer particles containing no pigment. Aqueous dispersions of polymer particles that do not contain pigments can function as fixing aids. It is considered that the polymer dispersant used in the water-based pigment dispersion of the present invention has two different resins adsorbed or immobilized on the pigment. Therefore, even when the water-based ink further contains polymer particles that do not contain pigment, a smooth coating film is obtained on the printing medium due to the affinity between the polymer particles and the polymer dispersant, and the pigment particles locally aggregate. Therefore, it is possible to improve the adhesion without lowering the print density.

Polymers constituting the pigment-free polymer particles include condensation polymers such as polyolefin resins, polyurethane resins and polyester resins; acrylic resins, styrene resins, styrene-acrylic resins, butadiene resins, and styrene-butadiene resins. , vinyl chloride resins, vinyl acetate resins and acrylic silicone resins.
The pigment-free aqueous dispersion of polymer particles may be appropriately synthesized or commercially available. When an aqueous dispersion of polyester resin particles containing no pigment is used, an emulsion of the polyester resin (B) described above may be used.
Examples of commercially available dispersions of polyolefin resin particles that do not contain pigments include 150S, 250S, 350S, 351S, 353S, 359S, AE-202 and AE of Auroren (registered trademark) series manufactured by Nippon Paper Industries Co., Ltd. -301, Superchron (registered trademark) series, 822, 892L, 930, 842LM, 851L, 3228S, 3221S, 2319S; Toyobo Co., Ltd., Hardren (registered trademark) series, CY-9122P, CY-9124P, HM -21P, M-28P, F-2P, F-6P, CY-1132, NZ-1004; SB-1200, SE-1200, SB-1010, etc. of the Arrow Base (registered trademark) series manufactured by Unitika Ltd. mentioned.
Commercially available pigment-free polyurethane resin particle dispersions include "NeoRez R-9603" (manufactured by DSM Coating Resins, trade name), "WBR-2018" and "WBR-2000U" (manufactured by Taisei Fine Chemicals Co., Ltd.). product name) and the like.
Commercially available pigment-free vinyl polymer particle dispersions include, for example, "Neocryl A-1127" (manufactured by DSM Coating Resins, trade name, anionic self-crosslinking aqueous acrylic resin), "Joncryl 390", Acrylics such as “Joncryl 7100”, “Joncryl 7600”, “Joncryl 537J”, “Joncryl PDX-7164”, “Joncryl 538J”, “Joncryl 780” (manufactured by BASF Japan Co., Ltd., trade name) Resins, styrene-butadiene resins such as "SR-100" and "SR102" (manufactured by Nippon A&L Co., Ltd., product names), and "Vinyblan 700" and "Vinyblan 701" (manufactured by Nissin Chemical Industry Co., Ltd., products name) and other vinyl chloride resins.
The amount of the aqueous dispersion of polymer particles containing no pigment in the water-based ink is preferably 10% by mass or less, more preferably 10% by mass or less, as a solid content, from the viewpoints of storage stability, adhesion and print density of the water-based ink. is 7% by mass or less, more preferably 5% by mass or less.

Water-based inks may optionally contain various additives commonly used in water-based inks, such as humectants, humectants, penetrants, surfactants, viscosity modifiers, antifoaming agents, preservatives, antifungal agents, and antirust agents. Additives may be added, and filtration treatment using a filter or the like may be performed.
The content of each component of the water-based ink and the physical properties of the ink are as follows.

(Pigment content)
The content of the pigment in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more, from the viewpoint of print density. From the viewpoint of lowering and improving storage stability, the content is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 7% by mass or less.
(Total content of pigment and polymer dispersant)
From the viewpoint of adhesion, the total content of the pigment and polymer dispersant in the water-based ink is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and even more preferably 7% by mass. It is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 12% by mass or less from the viewpoint of lowering the ink viscosity during solvent volatilization and improving storage stability. be.
(Content of organic solvent)
The content of the organic solvent in the water-based ink is preferably 3% by mass or more, more preferably 5% by mass or more, and still more preferably 7% by mass or more, from the viewpoints of storage stability, adhesion, and print density of the water-based ink. and is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.
(Water content)
The water content in the water-based ink is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more, from the viewpoints of the storage stability of the water-based ink and the adhesion and print density. Yes, and preferably 90% by mass or less, more preferably 85% by mass or less.

The mass ratio of the pigment in the total solid content of the water-based ink [pigment/(total solid content of the water-based ink)] is preferably 0.25 or more from the viewpoint of the storage stability of the water-based ink, as well as the adhesion and print density. More preferably 0.3 or more, still more preferably 0.35 or more, still more preferably 0.4 or more, and preferably 0.75 or less, more preferably 0.7 or less, still more preferably 0.6 Below, more preferably 0.5 or less.

(Physical properties of water-based ink)
From the viewpoint of storage stability, the viscosity of the water-based ink at 32° C. is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, still more preferably 5 mPa·s or more, and preferably 12 mPa·s or less. It is more preferably 9 mPa·s or less, still more preferably 7 mPa·s or less.
The viscosity of water-based ink can be measured using an E-type viscometer.
From the viewpoint of storage stability, the pH of the water-based ink at 20° C. is preferably 7.0 or higher, more preferably 7.2 or higher, and even more preferably 7.5 or higher. Also, from the viewpoint of member resistance and skin irritation, the pH is preferably 11 or less, more preferably 10 or less, and even more preferably 9.5 or less.
The pH of water-based ink at 20° C. can be measured by a conventional method.

Water-based inks can be suitably used as flexographic printing inks, gravure printing inks, or inkjet inks, and are particularly preferably used as inkjet inks. An image or the like can be recorded by loading a known inkjet recording apparatus and ejecting ink droplets onto a printing medium.
There are thermal type and piezo type ink jet recording apparatuses, and the water-based ink containing the water-based pigment dispersion of the present invention is more preferably used as a water-based ink for piezo type ink jet recording.
Usable print media include highly water-absorbing plain paper, low water-absorbing coated paper, and non-water-absorbing resin film. Examples of coated paper include general-purpose glossy paper, multicolor foam gloss paper, and the like. The resin film is preferably at least one selected from polyester film, polyvinyl chloride film, polypropylene film and polyethylene film. A corona-treated substrate may be used for the resin film.
Examples of commonly available resin films include Lumirror T60 (manufactured by Toray Industries, Inc., polyester), PVC80BP (manufactured by Lintec Corporation, vinyl chloride), DGS-210WH (manufactured by Roland DG Co., Ltd., vinyl chloride), and transparent. PVC RE-137 (manufactured by Mimaki Engineering Co., Ltd., vinyl chloride), Cainus KEE70CA (manufactured by Lintec Corporation, polyethylene), YUPO SG90 PAT1 (manufactured by Lintec Corporation, polypropylene), FOR, FOA (both manufactured by Futamura Chemical Co., Ltd., Polypropylene), Bonyl RX (manufactured by Kohjin Film & Chemicals Co., Ltd., nylon), Emblem ONBC (manufactured by Unitika Ltd., nylon), and the like.

In the following Preparation Examples, Examples and Comparative Examples, "parts" and "%" are "mass parts" and "mass%" unless otherwise specified.
Various physical properties of the dispersions obtained in Preparation Examples, Examples and Comparative Examples were measured and evaluated by the following methods.

(1) Measurement of number average molecular weight of (meth)acrylic resin (A) A solution obtained by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol/L and 50 mmol/L, respectively, was prepared. As an eluent, a gel permeation chromatography method [Tosoh Corporation GPC device (HLC-8320GPC), Tosoh Corporation columns (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn SuperAW-H), flow rate: 0.5 mL / min ], monodisperse polystyrene kits with known molecular weights [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F -4, A-5000, A-500), manufactured by Tosoh Corporation].
A sample to be measured was obtained by mixing 0.1 g of (meth)acrylic resin (A) with 10 mL of the eluent in a glass vial, stirring with a magnetic stirrer at 25° C. for 10 hours, and filtering through a syringe filter (DISMIC-13HP PTFE 0 .2 μm, manufactured by Advantech) and used.

(2) Measurement of average particle size of water-based pigment dispersion diameter. The measurement conditions were a temperature of 25° C., an angle between the incident light and the detector of 90°, and 100 integration times, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5×10 ^-3 %.

(3) Measurement of Solid Content Concentration 10.0 g of sodium sulfate that has been made constant in a desiccator is weighed into a 30 ml polypropylene container (φ = 40 mm, height = 30 mm), and about 1.0 g of a sample is added thereto. After mixing, the mixture was accurately weighed, maintained at 105° C. for 2 hours to remove volatiles, left in a desiccator for 15 minutes, and weighed. The mass of the sample after removing the volatile matter was defined as the solid content, and the mass of the added sample was divided to obtain the solid content concentration.

<Preparation of (meth)acrylic resin (A)>
Preparation Example 1-1
Methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent) 30 parts, styrene (manufactured by Wako Pure Chemical Industries, Ltd., reagent) 100 parts, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6S, number average molecular weight : 6,000, solid content concentration 50%) 60 parts (30 parts as solid content), polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name: Blemmer PP-800, propylene oxide average added mole number 13, terminal: 40 parts of hydroxyl group) were mixed to prepare a monomer mixed solution. 20 parts of methyl ethyl ketone (MEK), 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the monomer mixture were added and mixed in a reaction vessel, and the mixture was sufficiently replaced with nitrogen gas.
On the other hand, in the dropping funnel, the remainder of the monomer mixture (90% of the monomer mixture), 0.27 parts of the polymerization chain transfer agent, 60 parts of MEK, and an azo radical polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., Product name: V-65, 2,2′-azobis(2,4-dimethylvaleronitrile)) 2.2 parts mixed solution was added, and under a nitrogen atmosphere, while stirring the monomer mixed solution in the reaction vessel, 65 C., and the mixture in the dropping funnel was added dropwise over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution of 0.3 parts of the polymerization initiator dissolved in 5 parts of MEK was added, and further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours to obtain a (meth)acrylic resin. A solution of (A-1) (acid value: 98 mgKOH/g, number average molecular weight: 50,000) was obtained.

Preparation Example 1-2
60 parts of acrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent), 130 parts of styrene (manufactured by Wako Pure Chemical Industries, Ltd.), and 10 parts of α-methylstyrene (manufactured by Wako Pure Chemical Industries, Ltd., reagent) are mixed to obtain a monomer. A mixture was prepared. 20 parts of MEK, 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the above-mentioned monomer mixture were added and mixed in a reaction vessel, and nitrogen gas was sufficiently replaced.
On the other hand, in the dropping funnel, the remainder of the monomer mixture (90% of the monomer mixture), 0.27 parts of the polymerization chain transfer agent, 60 parts of MEK and 2.2 parts of an azo radical polymerization initiator (V-65) The mixed solution was added, and thereafter the same procedure as in Preparation Example 1-1 was performed to obtain a solution of (meth)acrylic resin (A-2) (acid value: 234 mgKOH/g, number average molecular weight: 11,000).

<Preparation of polyester resin (B) emulsion>
Preparation Example 2-1
The inside of a 10 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a flow-down condenser and a nitrogen inlet tube was replaced with nitrogen, and polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl ) 3,534 g of propane, 1,173 g of terephthalic acid, and 10 g of dibutyltin oxide were added, and the temperature was raised to 230°C with stirring under a nitrogen atmosphere. held for time. Then, after cooling to 210° C. and returning to atmospheric pressure, 293 g of fumaric acid and 2.5 g of 4-tert-butylcatechol were added, and after holding at 210° C. for 5 hours, the pressure in the flask was further lowered. The pressure was maintained at 3 kPa for 4 hours to obtain a polyester resin (B-1).
The obtained polyester resin (B-1) had a softening point of 104° C., a glass transition temperature of 63° C., and an acid value of 20 mgKOH/g.
200 g of polyester resin (B-1) was placed in a 1 L four-necked flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer "Three One Motor BL300" (manufactured by Shinto Kagaku Co., Ltd.) and a thermocouple, and heated to 30 ° C. was mixed with 200 g of methyl ethyl ketone to dissolve the resin. Next, 37.1 g of a 5% by mass sodium hydroxide aqueous solution was added and stirred for 30 minutes to obtain an organic solvent-based slurry. 600 g of deionized water was added dropwise at 30° C. with stirring at a rate of 20 mL/min. Then, after the temperature was raised to 60° C., methyl ethyl ketone was distilled off while the pressure was gradually reduced from 80 kPa to 30 kPa, and a part of water was further distilled off. After cooling to 25° C., the mixture was filtered through a 150-mesh wire mesh and adjusted to a solid concentration of 30% with deionized water to obtain an emulsion of polyester resin (B-1).

<Production of water-based pigment dispersion>
Example 1
(Step 1-1)
35 parts of (meth)acrylic resin (A-1) obtained by drying the polymer solution obtained in Preparation Example 1-1 under reduced pressure was mixed with 40 parts of MEK, and further 5N aqueous sodium hydroxide solution (sodium hydroxide solid 16.9%, Wako Pure Chemical Industries, Ltd., for volumetric titration) is added, and the (meth)acrylic resin (A-1) is added so that the equivalent of the neutralizing agent is 70 mol%. calmed down Next, 180 parts of ion-exchanged water is added, 100 parts of carbon black pigment (C.I. Pigment Black 7, manufactured by Cabot Specialty Chemicals, trade name "Monarch 717") is added therein, and disper (Asada Iron Works Co., Ltd.) is added. A pre-dispersion (1) was obtained by stirring at 20° C. for 60 minutes under the condition of rotating the disper blade at 7,000 rpm.
(Step 1-2)
For the preliminary dispersion (1) obtained in step 1-1, 375 parts of the polyester resin (B-1) emulsion (solid content: 30%) (effective solid content: 112.5 parts), 40 parts of MEK, 400 parts of ion-exchanged water (W1) was added to obtain a pigment mixture.
(Step 1)
The pigment mixture obtained in step 1-2 was subjected to dispersion treatment using a microfluidizer (manufactured by Microfluidics, trade name) at a pressure of 200 MPa for 10 passes to obtain a dispersion.
After adding 200 parts of ion-exchanged water (W2) to the obtained dispersion and stirring, MEK was removed at 60° C. under reduced pressure, a part of the water was removed, and a filter with a pore size of 5 μm (acetylcellulose membrane, Outer diameter: 2.5 cm, Fuji Film Co., Ltd.) was attached to a 25 mL needleless syringe (manufactured by Terumo Corporation) to remove coarse particles, resulting in a water-based pigment dispersion with a solid content concentration of 25%. body (d-1) was obtained. The average particle size was 98 nm.

Example 2
(Step 2)
100 parts of the aqueous pigment dispersion (d-1) obtained in Example 1 was placed in a glass bottle with a screw cap, and trimethylolpropane polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol") was added as a cross-linking agent (C). EX-321L", 0.19 parts of epoxy equivalent 129) was added, and the mixture was sealed and heated at 70° C. for 5 hours while stirring with a stirrer. After that, the mixture was cooled to room temperature and filtered through a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a 5 μm pore size filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation) to obtain a solid. An aqueous pigment dispersion (D-2) having a concentration of 25% was obtained.

Example 3
Except for changing the polyester resin (B-1) emulsion in step 1-2 of Example 1 to 208 parts (effective solid content 62.4 parts), MEK to 30 parts, and ion-exchanged water (W1) to 340 parts. , to obtain an aqueous pigment dispersion (d-3) in the same manner as in Example 1. Next, except that the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to water-based pigment dispersion (d-3), and the amount of Denacol EX-321L added was changed to 0.24 parts. A water-based pigment dispersion (D-3) was obtained in the same manner as in Example 2.

Example 4
47 parts of the (meth)acrylic resin (A-1) in step 1-1 of Example 1, 14 parts of 5N aqueous sodium hydroxide solution, and 190 parts of ion-exchanged water were changed to 190 parts, and step 1- of Example 1 Example 2 was the same as in Example 1, except that the polyester resin (B-1) emulsion in 2 was changed to 167 parts (effective solid content: 50.1 parts), MEK to 35 parts, and ion-exchanged water (W1) to 350 parts. A water-based pigment dispersion (d-4) was obtained by the procedure. Next, the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to the water-based pigment dispersion (d-4), and the addition amount of Denacol EX-321L was changed to 0.32 parts. A water-based pigment dispersion (D-4) was obtained in the same manner as in Example 2.

Example 5
Example 1 except that the polyester resin (B-1) emulsion in step 1-2 of Example 1 was changed to 104 parts (effective solid content 31.2 parts) and the ion-exchanged water (W1) was changed to 300 parts. A water-based pigment dispersion (d-5) was obtained in the same manner. Next, except that the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to water-based pigment dispersion (d-5), and the amount of Denacol EX-321L added was changed to 0.29 parts. A water-based pigment dispersion (D-5) was obtained in the same manner as in Example 2.

Example 6
The (meth)acrylic resin (A-1) in step 1-1 of Example 1 was changed to 18 parts, 5 parts of 5N aqueous sodium hydroxide solution, and 160 parts of ion-exchanged water, and step 1- of Example 1 Example 2 was the same as in Example 1, except that the polyester resin (B-1) emulsion in 2 was changed to 81 parts (effective solid content: 24.3 parts), MEK was changed to 30 parts, and ion-exchanged water (W1) was changed to 260 parts. A water-based pigment dispersion (d-6) was obtained by the procedure. Next, the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to the water-based pigment dispersion (d-6), and the addition amount of Denacol EX-321L was changed to 0.17 parts. A water-based pigment dispersion (D-6) was obtained in the same manner as in Example 2.

Example 7
The (meth)acrylic resin (A-1) in step 1-1 of Example 1 was changed to 18 parts, and the polyester resin (B-1) emulsion in step 1-2 was changed to 21 parts (effective solid content 6.0 parts). 3 parts) and ion-exchanged water (W1) was changed to 230 parts, to obtain a pigment aqueous dispersion (d-7) in the same manner as in Example 1. Next, except that the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to water-based pigment dispersion (d-7), and the amount of Denacol EX-321L added was changed to 0.19 parts. A water-based pigment dispersion (D-7) was obtained in the same manner as in Example 2.

Example 8
(Meth)acrylic resin (A-1) in Step 1-1 of Example 1 was obtained by drying the polymer solution obtained in Preparation Example 1-2 under reduced pressure (Meth)acrylic resin (A-2) ), 5N sodium hydroxide aqueous solution was changed to 14 parts, 194 parts of the polyester resin (B-1) emulsion in step 1-2 (effective solid content 58.2 parts), 30 parts of MEK, ion-exchanged water An aqueous pigment dispersion (d-8) was obtained in the same manner as in Example 1, except that (W1) was changed to 340 parts. Next, except that the water-based pigment dispersion (d-1) in step 2 of Example 2 was changed to water-based pigment dispersion (d-8), and the amount of Denacol EX-321L added was changed to 0.59 parts. A water-based pigment dispersion (D-8) was obtained in the same manner as in Example 2.

Comparative example 1
(Step 1'-1)
303 parts of the polyester resin (B-1) emulsion was mixed with 20 parts of MEK and 30 parts of ion-exchanged water, and carbon black pigment (C.I. Pigment Black 7, manufactured by Cabot Specialty Chemicals, trade name "Monarch 717”) was added, and using a disper (manufactured by Asada Iron Works Co., Ltd., trade name “Ultra Disper”), the dispersion was stirred for 60 minutes at 20 ° C. under the conditions of rotating the disper blade at 7,000 rpm, and the preliminary dispersion ( 1') was obtained.
(Step 1'-2)
300 parts of ion-exchanged water (W1) was added to the preliminary dispersion (1') obtained in step 1'-1 to obtain a pigment mixture.
(Step 1')
The pigment mixture obtained in step 1'-2 was subjected to 10 pass dispersion treatment with a microfluidizer (manufactured by Microfluidics, trade name) at a pressure of 200 MPa. was not able to obtain a dispersion of

Comparative example 2
(Step 1'-1)
95 parts of (meth)acrylic resin (A-1) obtained by drying the polymer solution obtained in Preparation Example 1-1 under reduced pressure was mixed with 75 parts of MEK, and further 5N aqueous sodium hydroxide solution (sodium hydroxide solid 27 parts of 16.9% by weight (volumetric titration product manufactured by Wako Pure Chemical Industries, Ltd.) was added, and neutralization was carried out so that the use equivalent of the neutralizing agent was 70 mol %. Furthermore, 200 parts of ion-exchanged water is added, 100 parts of carbon black pigment (C.I. Pigment Black 7, manufactured by Cabot Specialty Chemicals, trade name "Monarch 717") is added, and disper (manufactured by Asada Iron Works Co., Ltd.) is added. , trade name "Ultra Disper"), and stirred at 20°C for 60 minutes under the condition of rotating the disper blade at 7,000 rpm to obtain a preliminary dispersion (2').
(Step 1'-2)
270 parts of ion-exchanged water (W1) was added to the preliminary dispersion (2') obtained in step 1'-1 to obtain a pigment mixture.
(Step 1')
The pigment mixture obtained in step 1′-2 was subjected to 10 passes of dispersion treatment with a Microfluidizer (manufactured by Microfluidics, trade name) at a pressure of 200 MPa to obtain a dispersion.
After adding 180 parts of ion-exchanged water (W2) to the resulting dispersion and stirring, MEK was removed at 60° C. under reduced pressure, a portion of the water was removed, and a filter with a pore size of 5 μm (acetylcellulose membrane, Outer diameter: 2.5 cm, Fuji Film Co., Ltd.) was attached to a 25 mL needleless syringe (manufactured by Terumo Corporation) to remove coarse particles, resulting in a water-based pigment dispersion with a solid content concentration of 25%. body (d-C2) was obtained.
(Step 2')
100 parts of the resulting water-based pigment dispersion (d-C2) was placed in a glass bottle with a screw cap, and trimethylolpropane polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-321L") was added as a cross-linking agent (C). and 0.67 parts of epoxy equivalent 129) were added, and the mixture was sealed and heated at 70° C. for 5 hours while stirring with a stirrer. After that, the temperature is lowered to room temperature, and filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a filter with a pore size of 5 μm (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation). A pigment dispersion (D-C2) was obtained.

Comparative example 3
41 parts of (meth)acrylic resin (A-1) in step 1'-1 of Comparative Example 2, 21 parts of MEK, 12 parts of 5N aqueous sodium hydroxide solution, and 200 parts of ion-exchanged water except that , to obtain a water-based pigment dispersion (d-C3) in the same manner as in Comparative Example 2. Next, the water-based pigment dispersion (d-C2) in step 2' of Comparative Example 2 was changed to the water-based pigment dispersion (d-C3), except that the amount of Denacol EX-321L added was changed to 0.39 parts. , to obtain a water-based pigment dispersion (D-C3) in the same manner as in Comparative Example 2.

<Evaluation Test of Aqueous Pigment Dispersion>
Test 1 (Evaluation of storage stability)
Each of the water-based pigment dispersions obtained in Examples and Comparative Examples was filled in a screw tube, sealed, and stored in a constant temperature room set at 70° C. for 7 days. The average particle size before and after storage was measured by the method of (2) above, and the average particle size increase rate was calculated from the following formula. The results are shown in Tables 1 and 2. The smaller the average particle size increase rate, the smaller the aggregate amount of the pigment particles and the better the storage stability.
Average particle size increase rate (%) = [(average particle size of aqueous pigment dispersion after storage - average particle size of aqueous pigment dispersion before storage) / average particle size of aqueous pigment dispersion before storage] x 100

<Evaluation test of water-based ink>
(Preparation of water-based inks 1 to 10 and C2 to C4)
Using each of the water-based pigment dispersions obtained in Examples and Comparative Examples, the pigment concentration in the entire water-based ink was 4%, propylene glycol was 10%, and a polyether-modified silicone activator (PEG-11 methyl ether dimethicone, trade name "KF6011", manufactured by Shin-Etsu Chemical Co., Ltd.) to 1%, add ion-exchanged water, weigh so that the total amount becomes 100%, stir with a magnetic stirrer to mix well, and obtain The resulting mixed solution was similarly filtered with the 5 μm filter and the needleless syringe to remove coarse particles, thereby obtaining a water-based ink.
In Examples 9 and 10 and Comparative Example 4, the aqueous pigment dispersion shown in Table 2 was used, and an emulsion of polyester resin (B-1) was added as an aqueous dispersion of polymer particles containing no pigment during ink preparation. did.
Using the water-based inks 1 to 10 and C2 to C4 obtained, Tests 2 and 3 below were performed and evaluated. Results are shown in Tables 1 and 2.
The ink composition shown in Tables 1 and 2 indicates the amount (%) of each component when the total amount of the ink is 100%. Moreover, each notation in Tables 1 and 2 is as follows.
*1: Shows the mass ratio [polyester resin (B)/(meth)acrylic resin (A)] of polyester resin (B) to (meth)acrylic resin (A) in the water-based pigment dispersion.
*2: Indicates the mass ratio [pigment/(pigment+(meth)acrylic resin (A))] of the pigment to the total amount of the pigment and (meth)acrylic resin (A) in the aqueous pigment dispersion.
*3: Shows the mass ratio of the pigment in the total solid content of the aqueous pigment dispersion [pigment/(total solid content of the aqueous pigment dispersion)].
*4: Average particle size increase rate (%) of water-based pigment dispersion

Test 2 (evaluation of print density)
Bar coater no. 4 (manufactured by AS ONE) was applied to a polyester film (manufactured by Toray Industries, Inc., trade name “Lumirror T60”, thickness 75 μm) and heated at 60° C. for 10 minutes. Then, after standing at 25° C. for 24 hours, a total of 5 points at the center and four corners of the resulting printed matter (5.1 cm×8.0 cm) were measured using a Macbeth densitometer (manufactured by Gretag Macbeth, product number: Spectroeye). and calculated the average value. The higher the value, the better the print density.

Test 3 (evaluation of adhesion)
A cellophane tape (tape width 18 mm × 4 cm, manufactured by Nichiban Co., Ltd.) was attached to the coating film of the printed matter obtained by the evaluation of the print density, and after standing for 1 minute, the tape was placed perpendicular to the coating film. From the state of the coating film after being pulled and peeled off, the peeled area of the coating film was visually confirmed, and when the entire coating film surface was completely peeled off, the peeled area was defined as 100%, and evaluation was made according to the following evaluation criteria. A score of 2 or more according to the following evaluation criteria indicates excellent adhesion.
(Evaluation criteria)
4: There was no peeling of the coating film.
3: The peeling area of the coating film was less than 20%.
2: The peeling area of the coating film was 20% or more and less than 40%.
1: The peeling area of the coating film was 40% or more.

As shown in Tables 1 and 2, in Examples 1 to 10, the polymer dispersant contains (meth)acrylic resin (A) and polyester resin (B), so the storage stability is excellent and excellent. It can be seen that both good adhesion and high print density are achieved.
On the other hand, Comparative Example 1 did not contain the (meth)acrylic resin (A) as the polymer dispersant, so the pigment could not be dispersed. Comparative Examples 2 and 3 do not contain the polyester resin (B) as the polymer dispersant, so the adhesiveness is poor. In Comparative Example 4, the polyester resin (B) was not included as the polymer dispersant, and a polyester resin emulsion was added during ink preparation. It can be seen that the compatibility of

According to the present invention, a water-based pigment dispersion having excellent storage stability and having high print density while maintaining excellent adhesion to a non-water-absorbent printing medium by using it in water-based ink, and the water-based pigment dispersion. can provide a manufacturing method of

Claims (12)

A method for producing an aqueous pigment dispersion, comprising the following steps 1 and 2.
Step 1: A step of applying a shear stress to a pigment mixture containing a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin (B) to obtain a dispersion by dispersing. : A step of cross-linking the dispersion obtained in step 1 using a cross-linking agent (C) The amount of the cross-linking agent (C) used in step 2 is a ratio of the number of molar equivalents of the crosslinkable functional groups of the (meth)acrylic resin (A) to the number of molar equivalents of the acid groups of the (meth)acrylic resin (A), which is 0.00. The method for producing a water-based pigment dispersion according to claim 1 , wherein the ratio is 12 or more and 0.65 or less. The mass ratio of polyester resin (B) to (meth)acrylic resin (A) in the pigment mixture in step 1 [polyester resin (B)/(meth)acrylic resin (A)] is 0.15 or more and 15 or less. A method for producing an aqueous pigment dispersion according to claim 1 or 2 . 4. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 3, wherein the means for applying shear stress is to use a high-pressure homogenizer. 5. The method for producing a water-based pigment dispersion according to claim 4, wherein the treatment pressure when performing the dispersion treatment using a high-pressure homogenizer is 60 MPa or more and 300 MPa or less. 6. The method for producing a water-based pigment dispersion according to claim 4, wherein the number of passes is 3 or more and 30 or less when performing the dispersion treatment using a high-pressure homogenizer. 7. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 6, further comprising the following steps 1-1 and 1-2 before step 1.
Step 1-1: A step of dispersing a pigment in a (meth)acrylic resin (A) having an acid group to obtain a preliminary dispersion.
Step 1-2: An emulsion of a polyester resin (B) is added to the preliminary dispersion obtained in step 1-1 to obtain a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin ( B) obtaining a pigment mixture comprising The method for producing an aqueous pigment dispersion according to any one of claims 1 to 7, wherein both the (meth)acrylic resin (A) and the polyester resin (B) have an acid group. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 8, wherein the cross-linking agent (C) is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group with 3 to 8 carbon atoms. The mass ratio of the pigment in the total solid content of the water-based pigment dispersion [pigment/(total solid content of the water-based pigment dispersion)] is 0.25 or more and 0.85 or less, according to any one of claims 1 to 9 A method for producing an aqueous pigment dispersion. The mass ratio of the pigment to the total amount of the pigment and the (meth)acrylic resin (A) in the water-based pigment dispersion [pigment/(pigment+(meth)acrylic resin (A))] is 0.3 or more and 0.3. 95 or less, the method for producing a water-based pigment dispersion according to any one of claims 1 to 10. A method for producing a water-based ink, comprising mixing the water-based pigment dispersion according to any one of claims 1 to 11 and an organic solvent.