JP7223537B2 - Pigment-containing resin composition - Google Patents

Description

The present invention relates to a pigment-containing resin composition, a method for producing the same, an inkjet recording ink containing the pigment-containing resin composition, and a method for producing the ink.

Inkjet printing is printing in which ink droplets are directly ejected from extremely fine nozzles onto a printing medium and adhered to record characters and images. This method has the advantages of low power consumption and non-contact with the print medium, and has become very popular in recent years. Among them, the drop-on-demand method, in which ink droplets are ejected only when recording is required, has become mainstream.
Furthermore, in recent years, water-based inks have become mainstream as inks that are less burdensome to the environment. Pigments are widely used as colorants to impart weather resistance and water resistance to printed matter. When a pigment is used as a colorant for a water-based ink, the ink is prepared by adding a water-based pigment dispersion (hereinafter also referred to as an "aqueous pigment dispersion") in which the pigment is finely dispersed in a water-based medium and a water-soluble organic solvent as a moisturizing agent. However, since the water-based pigment dispersion contains a large amount of water and has high water activity, there is a problem of deterioration due to the generation of microorganisms such as fungi. Attempts have been made to solve this problem by adding a fungicide to the water-based pigment dispersion and by heat-treating the water-based pigment dispersion. However, in general, bactericides are irritating to humans, and when water-based pigment dispersions are used in inks, the bactericides are brought into the ink, which can cause skin troubles when the final user comes into direct contact. have a nature. Moreover, the heat treatment of the water-based pigment dispersion is costly, and there is a concern that the components in the water-based pigment dispersion may deteriorate. It may occur.

Therefore, in order to overcome the problem of microorganisms, a method of reducing the water content in the water-based pigment dispersion is known.
For example, in Patent Document 1, as a production method for obtaining an aqueous pigment dispersion that does not develop coarse particles even after a heating and cooling test and has good long-term storage stability, a pigment and a resin having an anionic group are disclosed. and a neutralizing agent that neutralizes the anionic group, slurried in water or a liquid medium containing water as a main component, and then spray-dried or freeze-dried to obtain a composite pigment; A method for producing a pigment kneaded product is described, which comprises kneading a mixture containing the obtained composite pigment, a water-soluble organic solvent, and a resin having an anionic group.
Patent Document 2 describes a pigment formulation containing a pigment and/or carbon black and a polymer and/or a surfactant and produced from an aqueous dispersion by freeze-drying as a pigment formulation having redispersibility and the like. It is
Patent Document 3 describes a photocurable liquid ink containing a colorant and a curable liquid that is cured by light, and describes that the colored resin particles used in the ink are obtained by freeze-drying.

JP 2014-58591 A Japanese Patent Application Laid-Open No. 2001-152072 JP 2011-178948 A

Drop-on-demand ink jet heads, which have become mainstream in recent years, usually have a nozzle diameter of about 20 μm, and extremely large coarse particles cause poor ejection of ink even if the content thereof is small. Therefore, it is required to reduce the number of coarse particles having a particle size of about 1 μm to 5 μm. In the techniques of Patent Documents 1 to 3, the dispersibility of the pigment is not sufficient even if the aqueous pigment dispersion is prepared, and a large number of coarse particles may be contained. is desired.
The present invention provides a pigment-containing resin composition that is free from deterioration due to the generation of microorganisms, has excellent pigment dispersibility and contains few coarse particles when used in an aqueous pigment dispersion, a method for producing the same, and an ink. An object of the present invention is to provide an ink for inkjet recording with excellent ejection properties and a method for producing the ink.

The present inventors have proposed a pigment-containing resin composition containing a pigment and a resin, the resin having anionic groups, at least a portion of the anionic groups being neutralized with a basic compound. And if it has a crosslinked structure, even if the content of volatile substances in the pigment-containing resin composition is 1% by mass or less, when the pigment-containing resin composition is used in an aqueous pigment dispersion, It was found that the dispersibility of the pigment is excellent and the number of coarse particles can be reduced.

That is, the present invention provides the following [1] to [4].
[1] A pigment-containing resin composition containing a pigment and a resin (A), which satisfies conditions 1 to 4 below.
Condition 1: The resin (A) has an anionic group, at least part of the anionic group is neutralized with the basic compound (b), and has a crosslinked structure.
Condition 2: The content of volatile substances in the pigment-containing resin composition is 1% by mass or less.
Condition 3: A water dispersion (α) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 2 × 10 ^-4 % by mass, measured by dynamic light scattering method. The average particle size obtained by cumulant method analysis is 150 nm or less.
Condition 4: The content of the pigment in the aqueous dispersion (β) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 0.25% by mass, as measured by the number counting method. The number of particles having a particle size of 0.5 μm or more is 1.00×10 ⁹ or less per 1 ml of an aqueous dispersion having a solid content of 20% by mass of the resin composition.
[2] An inkjet recording ink containing the pigment-containing resin composition described in [1] above.
[3] A method for producing a pigment-containing resin composition according to [1] above, including the following Step I and Step II.
Step I: Water, a pigment, a resin (a) having an anionic group, a basic compound (b) that neutralizes the anionic group, and two or more crosslinkable functional groups that react with the anionic group. A step of mixing and dispersing the cross-linking agent (c) having to obtain an aqueous pigment dispersion (D) Step II: The aqueous pigment dispersion (D) obtained in Step I is dried to reduce the content of volatile substances Step of obtaining a pigment-containing resin composition of 1% by mass or less Here, the water-based pigment dispersion (D) contains the pigment and the resin (A), and the cumulant method analysis measured by the dynamic light scattering method is 150 nm or less.
[4] The method for producing an inkjet recording ink according to [2] above, which includes the following steps I to III.
Step I: Water, a pigment, a resin (a) having an anionic group, a basic compound (b) that neutralizes the anionic group, and two or more crosslinkable functional groups that react with the anionic group. A step of mixing and dispersing the cross-linking agent (c) having to obtain an aqueous pigment dispersion (D) Step II: The aqueous pigment dispersion (D) obtained in Step I is dried to reduce the content of volatile substances Step of obtaining a pigment-containing resin composition of 1% by mass or less Step III: Step of mixing the pigment-containing resin composition obtained in Step II with a liquid compound to obtain an inkjet recording ink Here, a water-based pigment dispersion (D) contains a pigment and resin (A), and has an average particle size of 150 nm or less as determined by cumulant method analysis measured by a dynamic light scattering method.

According to the present invention, there is no risk of deterioration due to the generation of microorganisms, and when used in an aqueous pigment dispersion, a pigment-containing resin composition that has excellent pigment dispersibility and has few coarse particles, and a method for producing the same, and It is possible to provide an ink for inkjet recording which is excellent in ink jettability and a method for producing the ink.

[Pigment-Containing Resin Composition]
The pigment-containing resin composition of the present invention (hereinafter also referred to as "pigment-containing resin composition") is a pigment-containing resin composition containing a pigment and a resin (A), and satisfies the following conditions 1 to 4. .
Condition 1: The resin (A) has an anionic group, at least part of the anionic group is neutralized with the basic compound (b), and has a crosslinked structure.
Condition 2: The content of volatile substances in the pigment-containing resin composition is 1% by mass or less.
Condition 3: A water dispersion (α) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 2 × 10 ^-4 % by mass, measured by dynamic light scattering method. The average particle size obtained by cumulant method analysis is 150 nm or less.
Condition 4: The content of the pigment in the aqueous dispersion (β) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 0.25% by mass, as measured by the number counting method. The number of particles having a particle size of 0.5 μm or more is 1.00×10 ⁹ or less per 1 ml of an aqueous dispersion having a solid content of 20% by mass of the resin composition.
In the present invention, the term "volatile substance" means a substance that volatilizes at normal temperature and normal pressure, specifically a substance that has a vapor pressure or sublimation pressure of greater than 1 kPa at 25°C and contains water.

The pigment-containing resin composition of the present invention has no risk of deterioration due to the generation of microorganisms, and when used in an aqueous pigment dispersion, has excellent pigment dispersibility and contains few coarse particles. When used in an ink for inkjet recording, the ink has an effect of being excellent in ejection properties. The reason is presumed as follows.
First, when the content of volatile substances in the pigment-containing resin composition satisfies the numerical range of Condition 2, the generation of microorganisms due to inclusion of water is suppressed, and deterioration can be prevented. In addition, when the resin contained in the pigment-containing resin composition satisfies the above condition 1, the dispersibility of the pigment is improved due to the structural stability of the pigment particles due to the electrostatic repulsion due to the anionic group of the resin and the crosslinked structure. It is thought that Furthermore, it is believed that the dispersibility of the pigment is improved when the average particle diameter of the aqueous dispersion obtained by dispersing the pigment-containing resin composition in water to a predetermined concentration satisfies the numerical range of Condition 3 above. Furthermore, in the water dispersion obtained by dispersing the pigment-containing resin composition in water to a predetermined concentration, the number of particles having a particle size of 0.5 μm or more is within the numerical range of the condition 4, so that the number of coarse particles is small. It is thought that a water-based pigment dispersion can be obtained, and the ink jettability is also 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 preferable as the pigment used in the 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.
Specific examples of preferred organic pigments include C.I. I. Pigment Yellow, C.I. I. Pigment Red, C.I. I. pigment orange, C.I. I. pigment violet, C.I. I. pigment blue, and C.I. I. One or more types of each product number selected from Pigment Green.
Examples of extender pigments include silica, calcium carbonate, and talc.
A pigment can be used individually by 1 type or in mixture of 2 or more types.

(Condition 1)
<Resin (A)>
In the pigment-containing resin composition of the present invention, the resin (A) has an anionic group, at least part of the anionic group is neutralized with the basic compound (b), and has a crosslinked structure. (Condition 1) is satisfied.
The resin (A) has a function as a pigment dispersant that exhibits a pigment dispersing action when the pigment-containing resin composition is used in an aqueous pigment dispersion or an ink, and a function as a fixing agent for printing media.
The anionic groups in the resin (A) are carboxy groups (--COOM), sulfonic acid groups (--SO ₃ M), phosphoric acid groups (--OPO ₃ M ₂ ), etc., which are dissociated to release hydrogen ions. groups exhibiting anionicity due to the presence of ions, or their dissociated ionic forms (-COO ^- , -SO ₃ ^- , -OPO ₃ ^2- , -OPO ₃ ^- M). In the above chemical formula, M represents a hydrogen atom, alkali metal, ammonium or organic ammonium. Among these, a carboxy group (--COOM) and its dissociated ionic form (--COO--) are preferred from the viewpoints of ease of introduction of an anionic group into the polymer skeleton and availability of monomers.

At least part of the anionic groups of the resin (A) are neutralized with the basic compound (b). Neutralization is performed by adding a basic compound (b) that reacts with an anionic group (hereinafter also referred to as "basic compound (b)").
Examples of the basic compound (b) include alkali metal compounds; organic amine compounds, and nitrogen-containing compounds such as ammonia. Among them, a strong base is preferable, and an alkali metal compound is more preferable, from the viewpoint of sufficiently expressing the electrostatic repulsive force due to neutralization and improving the dispersion stability of the pigment. That is, the counter ion of the neutralized anionic group of resin (A) is preferably an alkali metal cation.
Specific examples of alkali metals include lithium, sodium, potassium, rubidium and cesium. Among them, sodium and potassium are preferable, and sodium is more preferable, from the viewpoint of availability and expression of strong electrostatic repulsion by neutralization.
The alkali metal compound used as the basic compound (b) is preferably an alkali metal hydroxide, and the alkali metal hydroxide can be used in the form of an aqueous solution from the viewpoint of sufficiently and uniformly promoting neutralization. preferable. The concentration of the aqueous alkali metal hydroxide 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, more preferably 25% by mass. % or less.

Neutralization of the anionic groups of the resin (A) is preferably carried out so that the pH is 7 or more and 11 or less.
The equivalent amount of the basic compound (b) used is determined from the viewpoint of improving the dispersibility of the pigment and reducing the number of coarse particles, as well as the water resistance, storage stability, ejection property, and fixability of the ink containing the pigment-containing resin composition. etc., preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, still more preferably 18 mol% or more, and preferably 120 mol% or less, more preferably is 100 mol % or less, more preferably 50 mol % or less, still more preferably 30 mol % or less.
Here, the use equivalent of the basic compound (b) can be determined by the following formula from the acid value and mass of the resin (A) before neutralization (hereinafter also referred to as "resin (A')"). When the use equivalent of the basic compound (b) is 100 mol% or less, it is synonymous with the degree of neutralization, and in the following formula, when the use equivalent of the basic compound (b) exceeds 100 mol%, the basic compound It means that (b) is in excess with respect to the anionic groups of resin (A'), and the degree of neutralization of resin (A) at this time is regarded as 100 mol %.
Use equivalent (mol%) of basic compound (b) = [{added mass (g) of basic compound (b) / equivalent of basic compound (b)} / [{acid value of resin (A') ( mgKOH/g)×mass of resin (A′) (g)}/(56×1,000)]]×100

The resin (A) is preferably water-insoluble from the viewpoint of improving the dispersibility of the pigment, reducing the number of coarse particles, and improving the ejection property of the ink.
The term "water-insoluble" as used herein means that an aqueous dispersion obtained by dispersing the resin (A) in water to a concentration of 2×10 ⁻⁴ mass % does not become transparent. In the present invention, even if the aqueous dispersion looks transparent to the naked eye, it is judged to be water-insoluble when the Tyndall phenomenon is observed by observation with a laser beam or ordinary light.

Examples of the resin (A) include condensation resins such as polyester resins and polyurethane resins; and vinyl resins obtained by addition polymerization of vinyl monomers (vinyl compounds, vinylidene compounds, vinylene compounds). Among them, vinyl-based resins are preferable from the viewpoint of improving the dispersibility of the pigment, reducing the number of coarse particles, and improving the ejection property of the ink.

The resin (A) preferably comprises (a1) an anionic group-containing monomer (hereinafter also referred to as "(a1) component")-derived structural unit and (a2) a hydrophobic monomer (hereinafter referred to as "(a2) component" It is a vinyl-based resin containing structural units derived from The vinyl-based resin is a resin comprising raw material monomers (hereinafter also referred to as "raw material monomers") containing (a1) anionic group-containing monomer and (a2) hydrophobic monomer, and further having a crosslinked structure.

[(a1) anionic group-containing monomer]
(a1) The anionic group-containing monomer improves the dispersion stability of the pigment in an aqueous dispersion obtained using the pigment-containing resin composition or in an ink containing the pigment-containing resin composition due to its electrostatic repulsion. used from the point of view. Examples of the anionic group in the component (a1) include those mentioned above.
(a1) The anionic group-containing monomer is preferably a carboxy group-containing monomer from the viewpoint of availability and acidity. Examples of the carboxy group-containing monomer include carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, and 2-methacryloyloxymethylsuccinic acid. Among them, one or more selected from acrylic acid and methacrylic acid are preferable. .

[(a2) Hydrophobic Monomer]
(a2) The hydrophobic monomer improves the dispersion stability of the pigment in the aqueous dispersion obtained by using the pigment-containing resin composition or in the ink containing the pigment-containing resin composition due to its adsorptive power to the surface of the pigment. used from the point of view.
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. The amount of the (a2) hydrophobic monomer dissolved in 100 g of ion-exchanged water at 25° C. is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of the dispersion stability of the pigment.
(a2) Hydrophobic monomers include alkyl (meth)acrylates; aromatic group-containing monomers such as aryl (meth)acrylates, alkylaryl (meth)acrylates, and styrene-based monomers; and two or more alkylene oxide units having 3 or more carbon atoms. Polyalkylene glycol (meth)acrylate containing 30 or less, and the like.
In addition, "(meth)acrylate" means one or more selected from acrylate and methacrylate. "(meta)" below has the same meaning. Moreover, the molecular weight of the aromatic group-containing monomer is preferably less than 500.

The alkyl (meth)acrylate preferably has an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 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.

The aryl (meth)acrylate preferably has an aryl group with 6 or more and 14 or less carbon atoms, preferably 6 or more and 10 or less carbon atoms. Examples include phenyl (meth)acrylate, 1-naphthyl (meth)acrylate, and 2-naphthyl (meth)acrylate.
As the alkylaryl (meth)acrylate, one having an alkylaryl group having 7 or more and 15 or less carbon atoms, preferably 7 or more and 8 or less carbon atoms is preferable. For example, benzyl (meth)acrylate, phenylethyl (meth)acrylate and the like are preferable, and benzyl (meth)acrylate is more preferable.
Styrene-based monomers are preferably styrene, α-methylstyrene, vinyltoluene, and divinylbenzene, and more preferably styrene and α-methylstyrene.

In addition, (a2) the hydrophobic monomer may have a functional group having a heteroatom. Examples of the functional group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenoxy group, and the like. It means those bound to any position of the system monomer. For example, in the case of alkyl (meth)acrylates, 2-ethoxyethyl acrylate having an ethoxy group bonded to the 2-position of the ethyl group of ethyl acrylate, 2-butoxyethyl acrylate having a butoxy group bonded to the 2-position of the ethyl group of ethyl acrylate, Examples thereof include 2-phenoxyethyl acrylate in which a phenoxy group is bonded to the 2-position of the ethyl group of ethyl acrylate.
In the case of aryl (meth)acrylates, 4-ethylphenyl acrylate in which an ethyl group is bonded to the 4-position of the phenyl group of phenyl acrylate, and the like can be mentioned.
In the case of alkylaryl (meth)acrylates, 4-ethylphenylmethyl acrylate in which an ethyl group is bonded to the 4-position of the phenyl group of benzyl acrylate, and the like can be mentioned.

The polyalkylene glycol (meth)acrylate containing 1 to 30 alkylene oxide units having 3 or more carbon atoms improves the adsorptive power of the resin (A) to the surface of the pigment, and when the ink contains an organic solvent, From the viewpoint of improving the dispersion stability of the pigment due to the affinity with the organic solvent, polypropylene glycol (n = 2 to 30, n represents the number of repeating units of the alkylene oxide. The same applies hereinafter.) (meta) Acrylate, octoxy (ethylene oxide-propylene oxide copolymerization) (n = 1 to 30, number of propylene oxide repeating units therein = 1 to 29) (meth) acrylate, phenoxy (ethylene oxide-propylene oxide copolymerization) (n = 1 to 30, the number of repeating units of propylene oxide therein = 1 to 29) (meth)acrylates, and the like. Among them, polypropylene glycol (n=2 to 30) (meth)acrylate is preferred.
Commercially available polyalkylene glycol (meth)acrylates used as component (a2) include Blenmer PP-500, 800, 1000, 50PEP-300, 50POEP-800B, and 43PAPE-600B (above, NOF Co., Ltd.), etc.
(a2) Hydrophobic monomers may be the above monomers alone or in combination of two or more.

[(a3) macromonomer]
(a3) 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. may be used as a monomer component constituting the resin (A) from the viewpoint of improving the dispersion stability of the pigment in the ink containing The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, more preferably a methacryloyloxy group.
(a3) 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.
(a3) Macromonomers are preferably aromatic group-containing monomer-based macromonomers and silicone-based macromonomers from the viewpoint of improving the dispersion stability of the pigment in the aqueous dispersion and ink obtained using the pigment-containing resin composition. , aromatic group-containing monomer-based macromonomers are more preferable.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomers mentioned in (a2) the hydrophobic monomer described above, preferably styrene and benzyl (meth)acrylate, and styrene is more preferred.
Specific examples of styrene-based 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.

[(a4) nonionic monomer]
(a4) The nonionic monomer may be used from the viewpoint of improving the affinity for water in the aqueous dispersion obtained using the pigment-containing resin composition and improving the dispersion stability of the pigment.
(a4) nonionic monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; polyethylene glycol (n = 2 to 30) (meth)acrylate; methoxy Alkoxypolyethylene glycol (meth)acrylates such as polyethylene glycol (n=1 to 30) (meth)acrylates and the like can be mentioned.
(a4) Commercially available polyethylene glycol (meth)acrylates used as nonionic monomers include BLEMMER PE-90, PE-200, PE-350, PME-100, PME-200, PME-400, PME- 1000 (above, NOF Corporation) and the like.

In the present invention, resin (A) has a crosslinked structure. Thereby, the structural stability of the pigment particles is improved, the dispersibility of the pigment is improved, and the number of coarse particles can be reduced. In addition, when the pigment-containing resin composition is used as an ink for inkjet recording, the ejection property of the ink is improved.
In the present invention, the “crosslinked structure” means a structure in which two or more polymer chains are covalently bonded. From the viewpoint of improving the dispersibility of the pigment and reducing the number of coarse particles, the resin (A) preferably contains a three-dimensional network structure in which polymer chains are crosslinked. The resin (A) does not dissolve in a solvent that dissolves the resin before cross-linking, but takes a swollen state.

The crosslinked structure in the present invention is formed by any method. For example, in the production of the resin (A), a method of forming a crosslinked structure by polymerizing a monomer having two or more polymerizable functional groups in combination with a raw material monomer that forms a linear polymer skeleton. (i); A method of forming a crosslinked structure by generating a branched structure from the main chain by raising the polymerization conditions to a high temperature using only raw material monomers that form a linear polymer skeleton (ii); A method of forming a crosslinked structure by generating a branched structure from the main chain by using a compound having hydrogen abstraction ability such as a peroxide, using only raw material monomers that form the polymer skeleton (iii); and a resin having a crosslinkable functional group, and a crosslinker having two or more crosslinkable functional groups that react with the functional groups in the resin to form a crosslinked structure ( iv) and the like. Among them, it is preferable to form a crosslinked structure by the method (iv).
The resin (A) having a crosslinked structure formed by the method (iv) is preferably a resin (a) having an anionic group (hereinafter also referred to as "resin (a)") and a crosslinkable resin that reacts with the anionic group. A crosslinked structure is preferably formed by a crosslinking agent (c) having two or more functional groups (hereinafter also referred to as "crosslinking agent (c)").

When obtaining a resin (A) having a crosslinked structure by the method (iv), the resin (a) is preferably composed of one or more (a1) anionic group-containing monomers selected from acrylic acid and methacrylic acid. An acrylic resin containing units and structural units derived from one or more (a2) hydrophobic monomers selected from alkyl (meth)acrylate monomers and aromatic group-containing monomers, more preferably acrylic acid and methacrylic acid A styrene-acrylic resin containing a structural unit derived from one or more selected from and a structural unit derived from a styrene monomer. That is, the resin (A) is preferably an acrylic resin, more preferably a styrene-acrylic resin containing a structural unit derived from one or more selected from acrylic acid and methacrylic acid and a structural unit derived from a styrene monomer. Resin.

(Content of each component or structural unit in raw material monomer)
Contents of the components (a1) and (a2) in the raw material monomers (contents as unneutralized amounts; the same shall apply hereinafter) at the time of production of the resin (A), (a1) and ( From the viewpoint of improving the dispersion stability of the pigment in the aqueous dispersion obtained using the pigment-containing resin composition or the ink containing the pigment-containing resin composition, the content of the structural unit derived from component a2) is determined as follows. It is as follows.
The content of component (a1) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and is preferably less than 75% by mass, more preferably less than 60% by mass. , and more preferably less than 55% by mass.
The content of component (a2) is preferably 25% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, and is preferably less than 90% by mass, more preferably less than 80% by mass. , and more preferably less than 75% by mass.

(Resin (a) having an anionic group)
Examples of the anionic group of the resin (a) include those similar to those of the resin (A) described above. A carboxy group (--COOM) and its dissociated ionic form (--COO--) are preferred.
Here, M is as described above.
Examples of raw material monomers constituting the resin (a) include those similar to the raw material monomers constituting the resin (A) described above.
Resin (a) is preferably water-insoluble after cross-linking. Resin (a) may be synthesized or commercially available.
Commercial products of the resin (a) include polyacrylic acids such as Aron AC-10SL (manufactured by Toagosei Co., Ltd., trade name); 819 (manufactured by BASF Japan Ltd., trade name) and other styrene-acrylic resins.

When the resin (a) is obtained by synthesis, the raw material monomers constituting the resin (A) are copolymerized by known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Manufactured by 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); A known radical polymerization initiator such as an organic peroxide can be used. The amount of the radical polymerization initiator is preferably 0.001 mol or more and 5 mol or less, more preferably 0.01 mol or more and 2 mol or less per 1 mol of raw material monomer.
As the polymerization chain transfer agent, mercaptans such as octylmercaptan and 2-mercaptoethanol; known chain transfer agents such as 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 acid value of the resin (a) is preferably 200 mgKOH/g or more, more preferably 220 mgKOH/g or more, and preferably 320 mgKOH/g or less, more preferably 300 mgKOH/g or less, still more preferably 270 mgKOH/g or less. is. When the acid value is within the above range, the amount of the anionic group that exhibits electrostatic repulsion is sufficient, and the dispersion stability of the pigment is ensured.
The acid value of resin (a) can be calculated from the mass ratio of constituent monomers. It can also be determined by a method of dissolving or swelling a polymer in a suitable organic solvent (eg, MEK) and titrating.

The weight average molecular weight of resin (a) is preferably 2,000 or more, more preferably 5,000 or more, and preferably 20,000 or less, more preferably 18,000 or less. When the weight-average molecular weight of the resin (a) is within the above range, the adsorptive power to the pigment is sufficient and dispersion stability can be exhibited.
The weight average molecular weight can be measured by the method described in Examples.

(Crosslinking agent (c))
The cross-linking agent (c) has two or more cross-linkable functional groups that react with the anionic groups of the resin (a).
Examples of the cross-linking agent (c) include polyfunctional carbodiimide compounds, polyfunctional oxazoline compounds, polyfunctional isocyanate compounds, and polyfunctional epoxy compounds. Among them, polyfunctional carbodiimide compounds and polyfunctional epoxy compounds are preferred, and polyfunctional epoxy compounds are more preferred.

The polyfunctional epoxy compound used in the present invention is a compound having two or more epoxy groups in its molecule. The number of epoxy groups in the polyfunctional epoxy compound is preferably 2 or more and 6 or less per molecule from the viewpoint of efficiently reacting with the anionic groups to improve the dispersion stability of the pigment and the ejection property of the ink. From the viewpoint of compatibility of sex, 2 or more and 4 or less per molecule is more preferable.
The polyfunctional epoxy compound is preferably a compound having two or more glycidyl ether groups in the molecule, more preferably a hydrocarbon having 3 or more and 8 or less carbon atoms, from the viewpoint of pigment dispersion stability and ink ejection property. It is a polyglycidyl ether compound of a polyhydric alcohol having a group.
The water solubility of the polyfunctional epoxy compound is preferably 50% by mass or less, more preferably 40% by mass or less, from the viewpoint of efficiently reacting with the anionic groups of the resin (a) in an aqueous medium containing water as a main component. More preferably, it is 35% by mass or less. Here, the water solubility refers to the dissolution rate (% by mass) when 10 parts by mass of a polyfunctional epoxy compound is dissolved in 90 parts by mass of water at room temperature of 25°C. The water solubility is specifically measured by the method described in Examples.

The molecular weight of the polyfunctional epoxy compound is preferably 120 or more, more preferably 150 or more, still more preferably 200 or more, and preferably 2, from the viewpoints of easiness of reaction, dispersion stability of the pigment, and ejection property of the ink. ,000 or less, more preferably 1,500 or less, and still more preferably 1,000 or less.
The epoxy equivalent of the polyfunctional epoxy compound 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.

Specific examples of polyfunctional epoxy compounds include polypropylene glycol diglycidyl ether (water solubility 31% by mass), glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether (water solubility 27% by mass), sorbitol poly Examples include polyglycidyl ethers such as glycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Among these, trimethylolpropane polyglycidyl ether is preferred.

(Mass ratio in pigment-containing resin composition [pigment/resin (A)])
In the pigment-containing resin composition, the mass ratio of the pigment to the resin (A) [pigment/resin (A)] is from the viewpoint of improving the dispersibility of the pigment, reducing the number of coarse particles, and improving the ejection property of the ink. , preferably 60/40 or more, more preferably 65/35 or more, still more preferably 70/30 or more, and preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80/20 It is below.
In the present invention, the mass of the resin (A) used for calculating the mass ratio of the pigment to the resin (A) does not include the mass of the element or compound derived from the basic compound (b).

(Condition 2)
In the pigment-containing resin composition of the present invention, the content of volatile substances in the pigment-containing resin composition is 1% by mass or less (Condition 2). When the content of volatile substances is 1% by mass or less, the generation of microorganisms is suppressed and deterioration can be prevented. From this point of view, the content of volatile substances is preferably 0.8% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less.
The content of volatile substances is measured by the method described in Examples.

(Condition 3)
Aqueous dispersion (α) obtained by dispersing a pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 2 × 10 ^-4 mass%, cumulant method analysis measured by dynamic light scattering method (hereinafter also referred to as "average particle size of the aqueous dispersion (α)") determined in (Condition 3) is 150 nm or less. When the average particle diameter of the water dispersion (α) is 150 nm or less, the average particle diameter obtained by the cumulant method analysis measured by the dynamic light scattering method is also used in the ink for inkjet recording containing the pigment-containing resin composition. becomes 150 nm or less, and the ejection property of the ink is improved. From this point of view, the average particle size of the aqueous dispersion (α) is preferably 140 nm or less, more preferably 130 nm or less, and even more preferably 120 nm or less.
The average particle size of the aqueous dispersion (α) is measured by the method described in Examples.

(Condition 4)
The solid of the pigment-containing resin composition measured by the number counting method of the aqueous dispersion (β) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 0.25% by mass. The number of particles with a particle size of 0.5 μm or more (hereinafter also referred to as “the number of particles with a particle size of 0.5 μm or more in the aqueous dispersion (β)”) converted per 1 ml of a 20% by mass aqueous dispersion is It is 1.00×10 ⁹ or less (Condition 4). As a result, when used in an aqueous pigment dispersion, a pigment-containing resin composition having excellent pigment dispersibility and containing few coarse particles is obtained. Excellent dischargeability. From this point of view, the number of particles having a particle size of 0.5 μm or more in the aqueous dispersion (β) is preferably 5.00×10 ⁸ or less, more preferably 3.00×10 ⁸ or less, and still more preferably 2.0×10 8 or less. 00×10 ⁸ or less.
The number of particles having a particle size of 0.5 μm or more in the aqueous dispersion (β) is measured by the method described in Examples.

The solid of the pigment-containing resin composition measured by the number counting method of the aqueous dispersion (β) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 0.25% by mass. The number of particles with a particle size of 1 μm or more (hereinafter simply “the number of particles with a particle size of 1 μm or more in the aqueous dispersion (β)”) is preferably 1.00× 10 ⁷ or less, more preferably 5.00×10 ⁶ or less, still more preferably 3.00×10 ⁶ or less.

[Method for producing pigment-containing resin composition]
The pigment-containing resin composition of the present invention contains a pigment and a resin (A), and an aqueous pigment dispersion (D) in which the pigment is dispersed in an aqueous medium with the resin (A) (hereinafter referred to as "aqueous pigment dispersion (D) It is preferable to manufacture by a method of volatilizing and removing volatile substances from (also referred to as "). Methods for obtaining the aqueous pigment dispersion (D) include a method of dispersing the pigment in the resin (A), and a method of dispersing the pigment in the resin (a) having an anionic group without a crosslinked structure and then forming a crosslinked structure. and the like. Among them, from the viewpoint of production efficiency, the method including the following step I and step II is more preferable. Here, the "aqueous medium" means a liquid medium containing water as a main component.

Step I: Water, a pigment, a resin (a) having an anionic group, a basic compound (b) that neutralizes the anionic group, and two or more crosslinkable functional groups that react with the anionic group. A step of mixing and dispersing the cross-linking agent (c) having and obtaining an aqueous pigment dispersion (D) Step II: Drying the aqueous pigment dispersion (D) obtained in Step I to reduce the volatile substance content to 1 A step of obtaining a pigment-containing resin composition having a mass% or less

(Process I)
Step I is a step of mixing and dispersing water, a pigment, a resin (a), a basic compound (b), and a cross-linking agent (c) to obtain an aqueous pigment dispersion (D). In step I, the mixing order of each component is not particularly limited, but from the viewpoint of the dispersion stability of the pigment, after dispersing the pigment in the resin (a), the crosslinking agent (c) is added to form a crosslinked structure. method is preferred. Any known method can be used as a method for dispersing the pigment using the resin (a). Among them, it is preferable to include the following steps I-1 and I-2.
Step I-1: Step of dispersing a pigment mixture containing a pigment, a resin (a), an organic solvent, a basic compound (b) and water to obtain a pigment dispersion (d) Step I-2: Step I-1 A step of adding a cross-linking agent (c) to the pigment dispersion (d) obtained in , and cross-linking to obtain an aqueous pigment dispersion (D)

[Step I-1]
In step I-1, first, the resin (a) is mixed with an organic solvent, then a basic compound (b), water, a pigment, and, if necessary, a surfactant or the like are added and mixed to obtain a pigment mixture. A method of obtaining a pigment dispersion liquid (d) by subjecting the mixture to dispersion treatment after obtaining is preferred.
The organic solvent used in step I-1 is not particularly limited, but aliphatic alcohols having 1 to 3 carbon atoms, ketones, ethers, esters, etc. are preferable, and wettability to pigments and dissolution of resin (a) From the viewpoint of improving the properties and adsorption of the resin (a) to the pigment, ketones having 4 to 8 carbon atoms are more preferable, methyl ethyl ketone and methyl isobutyl ketone are more preferable, and methyl ethyl ketone is even more preferable.
When the resin (a) is produced by a solution polymerization method, from the viewpoint of productivity, the organic solvent used in the polymerization reaction may be used as an organic solvent solution of the resin (a) in step I-1 without removing it. good. From the viewpoint of productivity, the solid content concentration of the organic solvent solution of the resin (a) is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 50% by mass or less, 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 improving the dispersibility of the pigment, reducing the number of coarse particles, and improving the ejection property and productivity of the ink.
The content of the pigment in the pigment mixture is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 12.5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass. % by mass or less, more preferably 20% by mass or less.
The content of the resin (a) in the pigment mixture is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass or more, and preferably 8% by mass or less, more preferably It is 7% by mass or less, more preferably 6% 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 35% by mass or less, more preferably 30% by mass. % or less, more preferably 25 mass % or less.
The water content in the pigment mixture is preferably 40% by mass or more, more preferably 45% by mass or more, still more preferably 50% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass. 75% by mass or less, more preferably 75% by mass or less.

In the pigment mixture, the mass ratio of the pigment to the resin (a) [pigment/resin (a)] is determined from the viewpoint of improving the dispersibility of the pigment, reducing the number of coarse particles, and improving the stability of the ink. preferably 60/40 or more, more preferably 65/35 or more, still more preferably 70/30 or more, and preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80/20 or less be.

(Distributed processing)
In step I-1, the dispersion treatment applies shear stress to the pigment mixture from the viewpoint of adjusting the particle size and shape of the pigment, and from the viewpoint of firmly adsorbing the resin (a) on the pigment surface and improving the dispersibility of the pigment. to obtain a pigment dispersion (d). There is no particular limitation on the method of applying shear stress to the pigment mixture. Although it is possible to reduce the average particle size of the pigment dispersion (d) to a desired particle size using only one dispersing method, preferably the pigment mixture is predispersed and then shear stress is further applied. It is preferable to carry out the main dispersion and control the average particle size of the pigment dispersion (d) to a desired particle size.
The temperature in the pre-dispersion of step I-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 for pre-dispersion in step I-1 is preferably 0.5 hours or longer, more preferably 0.8 hours or longer, and preferably 30 hours or shorter, more preferably 10 hours or shorter, and even more preferably 5 hours or shorter. less than an hour.
When pre-dispersing the pigment mixture, generally used mixing and stirring devices such as anchor blades and disper blades can be used, but among them, high-speed stirring and mixing devices are preferred.

Examples of means for imparting shear stress for the main dispersion include kneaders such as roll mills and kneaders, medialess dispersers such as high-pressure homogenizers such as Microfluidizer (manufactured by Microfluidic), and media dispersers such as paint shakers and bead mills. is mentioned. A plurality of these devices can also be combined. Among these, a media dispersing machine is preferable from the viewpoint of miniaturizing the pigment.
Examples of commercially available media dispersers include Ultra Apex Mill (manufactured by Hiroshima Metal & Machinery Co., Ltd.) and Pico Mill (manufactured by Asada Iron Works Co., Ltd.).

When a media dispersing machine is used, the material of dispersed media particles is preferably ceramics such as zirconia and titania; polymer materials such as polyethylene and nylon; and metals. The diameter of the dispersion media particles is selected from the viewpoint of adjusting the particle size and shape of the pigment while suppressing excessive damage to the pigment particles, and the resin (a) is strongly adsorbed on the pigment surface to improve the dispersibility of the pigment. From the viewpoint of improvement, it is preferably 0.1 mm or less, more preferably 0.07 mm or less, and preferably 0.01 mm or more, more preferably 0.03 mm or more.
From the viewpoint of production efficiency, the rotation speed of the media dispersing machine is preferably 1,000 rpm or more, more preferably 2,000 rpm or more, and preferably 5,000 rpm or less, more preferably 3,000 rpm or less.
Either a circulation system or a continuous system can be used for the media dispersing machine, but the circulation system is preferable from the viewpoint of production efficiency.
The temperature of this dispersion in step I-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 of the main dispersion in step I-1 is preferably 0.5 hours or longer, more preferably 0.8 hours or longer, and preferably 30 hours or shorter, more preferably 10 hours or shorter, and even more preferably 5 hours or shorter. less than an hour.

The pigment dispersion (d) obtained in step I-1 is preferably obtained by further removing the organic solvent from the dispersion after the dispersion treatment. A well-known method can be used as a method of removing an organic solvent. The organic solvent in the resulting pigment dispersion (d) 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 dispersed material can be heated and stirred before distilling off the organic solvent.
Here, the pigment dispersion (d) is preferably an aqueous dispersion of pigment-containing resin (a) particles in which particles are formed from at least the pigment and the resin (a). The form of the pigment-containing resin (a) particles includes, for example, a particle form in which the pigment is encapsulated in the resin (a), a particle form in which the pigment is uniformly dispersed in the resin (a), and a particle surface of the resin (a). Included are particle forms with exposed pigments, etc., and mixtures thereof.

[Step I-2]
Step I-2 is a step of adding a cross-linking agent (c) to the pigment dispersion (d) obtained in step I-1 and performing a cross-linking treatment to obtain an aqueous pigment dispersion (D).
In the present invention, the viewpoint of enhancing the stability of the pigment in the aqueous dispersion obtained using the pigment-containing resin composition or the ink containing the pigment-containing resin composition, and the use of the pigment-containing resin composition as an ink for inkjet recording. When used, the cross-linking agent (c) used in step 1-2 is preferably a polyfunctional epoxy compound, as described above, from the viewpoint of improving the ejection property of the ink. As a result, part of the anionic groups of the resin (a) having anionic groups reacts with the polyfunctional epoxy compound to form a crosslinked structure.

(crosslinking treatment)
The temperature of the cross-linking treatment is preferably 50° C. or higher, more preferably 70° C. or higher, and preferably 95° C. or lower, more preferably 90° C. or lower, from the viewpoints of completion of the reaction and economy.
The time for the cross-linking treatment is preferably 0.5 hours or longer, more preferably 1 hour or longer, and preferably 10 hours or shorter, more preferably 5 hours or shorter, from the viewpoints of completion of the reaction and economy.
The degree of crosslinking of the resin (A) is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, and preferably 80 mol% or less, more preferably 70 mol% or less. , more preferably 60 mol % or less. The degree of crosslinking is obtained by dividing the number of moles of crosslinkable functional groups in the crosslinker (c) by the number of moles of anionic groups in the resin (a) that can react with the crosslinker (c).

The cross-linking treatment is preferably carried out in a range from 5 mass % to 50 mass % of the solid content concentration of the pigment dispersion (d). When it is 5% by mass or more, the production efficiency is improved, and when it is 50% by mass or less, aggregation of the pigment can be suppressed. From this point of view, the solid content concentration of the pigment dispersion (d) is preferably 10% or more, more preferably 15% or more, and more preferably 40% or less, still more preferably 30%. It is preferable to carry out within the following range.
Moreover, the cross-linking treatment is preferably carried out in a range in which the content of the volatile organic solvent in the dispersion medium of the pigment dispersion (d) is 5% by mass or less. Thereby, aggregation of the pigment can be suppressed. From this point of view, the content of the volatile organic solvent in the dispersion medium of the pigment dispersion (d) is preferably 1% by mass or less, more preferably 0.1% by mass or less. It is preferable to use 100% by mass of water as a dispersion medium.

In the water-based pigment dispersion (D) obtained in step I, the pigment is dispersed by the resin (A) in a water-based medium containing water as a main component.
Here, the form of the water-based pigment dispersion (D) is not particularly limited, and particles are preferably formed from at least the pigment and the resin (A). Examples include a particle form in which the pigment is encapsulated in the resin (A), a particle form in which the pigment is uniformly dispersed in the resin (A), and a particle form in which the pigment is exposed on the particle surface of the resin (A). , including mixtures thereof.

(Average particle size of aqueous pigment dispersion (D))
The average particle size of the water-based pigment dispersion (D) is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 70 nm or more, and preferably 150 nm or less, from the viewpoint of improving ink ejection properties. It is preferably 140 nm or less, more preferably 130 nm or less, and even more preferably 120 nm or less.
The average particle size of the water-based pigment dispersion (D) is a cumulant measured by a dynamic light scattering method by diluting the water-based pigment dispersion (D) with water so that the solid content concentration is 2 × 10 ^-4 % by mass. It means the average grain size obtained by the method analysis. Specifically, it is measured by the method described in Examples.

(Process II)
Step II is a step of drying the aqueous pigment dispersion (D) obtained in Step I to obtain a pigment-containing resin composition having a volatile substance content of 1% by mass or less.
The water-based pigment dispersion (D) obtained in step I contains water and volatile substances such as an organic solvent used as necessary. Therefore, in step II, the volatile substances contained in the aqueous pigment dispersion (D) are removed to obtain a solid pigment-containing resin composition having a volatile substance content of 1% by mass or less. The drying treatment is performed until the content of volatile substances in the pigment-containing resin composition is preferably 0.8% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less. preferably.
The content of volatile substances in the pigment-containing resin composition is measured by the method described in Examples.

Drying treatments include, for example, freeze drying, spray drying, hot air drying, blow drying, vacuum or reduced pressure drying, far-infrared heat drying, dehumidified air drying, and the like. Any commercially available device can be used for the drying treatment. Among these, freeze-drying or spray-drying is preferable from the viewpoint of the dispersion stability of the pigment and the ejection property of the ink, and from the viewpoint of suppressing thermal deterioration of the pigment and resin (A), and from the viewpoint of suppressing aggregation of the pigment. , lyophilization is preferred.
For spray drying, for example, the water-based pigment dispersion (D) is preferably sprayed in a spray drying apparatus and dried at an inlet temperature of 200° C. or lower and an outlet temperature of 110° C. or lower.
Freeze-drying is preferably performed by pre-freezing the water-based pigment dispersion (D), followed by primary drying and secondary drying.
Preliminary freezing is preferably rapid freezing at a temperature of -40°C or higher and -20°C or lower under normal pressure. Then, primary drying is performed to sublimate the ice in the pre-frozen material preferably under a vacuum of 0.1 Pa or more and 100 Pa or less at a temperature of −20° C. or more and −5° C. or less, and then a vacuum of 0.1 Pa or more and 100 Pa or less. It is preferable to perform secondary drying by raising the temperature to 20° C. or higher and 40° C. or lower.
Step II may further include a step of pulverizing the colored solid obtained after drying.

(Average particle size ratio [aqueous dispersion (α) / aqueous pigment dispersion (D)])
Ratio of the average particle size of the water dispersion (α) obtained by dispersing the pigment-containing resin composition in water to the average particle size of the water-based pigment dispersion (D) (hereinafter referred to as “average particle size ratio [aqueous dispersion (α) /water-based pigment dispersion (D)]”) is preferably 2 or less. The average particle size ratio [aqueous dispersion (α)/aqueous pigment dispersion (D)] is an index of redispersibility. Ejectability can be improved. From this point of view, the average particle size ratio [aqueous dispersion (α)/aqueous pigment dispersion (D)] is more preferably 1.5 or less, still more preferably 1.3 or less, and even more preferably 1.1 or less. is.

The pigment-containing resin composition of the present invention has excellent dispersibility of the pigment and a reduced number of coarse particles, so that it is possible to obtain good printed matter, and it is used for flexographic printing ink, gravure printing ink, inkjet recording ink, etc. It can be suitably used for printing ink. In addition, it is particularly preferred for use as an ink for inkjet recording, since it has excellent ink ejection properties in inkjet recording.
Various additives such as surfactants, wetting agents, penetrants, viscosity modifiers, antifoaming agents, antifungal agents, anticorrosive agents, and ultraviolet absorbers may be added to the printing ink as necessary. can be done.
When the pigment-containing resin composition of the present invention is used as a printing ink, it is preferably produced by adding and mixing a liquid compound to the pigment-containing resin composition. Specific examples of liquid compounds include water, organic solvents, surfactants, disinfectants, and the like.

[Ink for inkjet recording]
The ink for inkjet recording of the present invention (hereinafter also referred to as "ink for inkjet recording") contains the pigment-containing resin composition.
The content of the pigment in the inkjet recording ink is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 2.5% by mass or more, from the viewpoint of improving the printing density of the ink, and From the viewpoint of suppressing thickening of the ink during volatilization of the liquid medium and improving the storage stability and ejection properties of the ink, 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. be.
In the ink for inkjet recording, the mass ratio of the pigment to the resin (A) [pigment/resin (A)] is preferably 60/40 or more, more preferably 65, from the viewpoint of improving the storage stability and ejection properties of the ink. /35 or more, more preferably 70/30 or more, and preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80/20 or less.

The ink for inkjet recording may be water-based ink or non-water-based ink.
Moreover, the ink for inkjet recording can also be used as a curable ink that is cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam by containing a polymerizable compound as a liquid compound.
From the viewpoint of improving storage stability and ejection properties of the ink, the ink for inkjet recording preferably contains water, and is more preferably a water-based ink. The term "aqueous ink" as used herein means that the mass ratio of water in the ink is the highest among liquid media.
The water content in the ink for inkjet recording is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, and is preferably 70% by mass or less, more preferably 65% by mass. % by mass or less, more preferably 60% by mass or less.

The presence of the pigment and the resin (A) in the ink for inkjet recording includes a state in which the resin (A) is adsorbed to the pigment, a state in which the resin (A) contains the pigment, and a state in which the pigment is encapsulated (capsule). There are forms in which the resin (A) does not adsorb the pigment, and one type selected from these forms may be used alone, or two or more types may be mixed.

From the viewpoint of suppressing evaporation of the ink medium and improving the storage stability and ejection properties of the ink, the ink for inkjet recording preferably contains a water-soluble organic solvent (B) in addition to water as a liquid medium. .
The water-soluble organic solvent (B) preferably contains one or more organic solvents having a boiling point of 90° C. or higher.
The weighted average boiling point of the water-soluble organic solvent (B) contained in the ink is preferably 150° C. or higher, more preferably 180° C. or higher, and is preferably 250° C. or lower, more preferably 240° C. or lower. It is more preferably 220° C. or lower, still more preferably 200° C. or lower.
Examples of the water-soluble organic solvent (B) 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 preferable, and ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, diethylene glycol monobutyl ether, and diethylene glycol diethyl. More preferably, one or more selected from ethers, more preferably one or more selected from propylene glycol, diethylene glycol monobutyl ether, glycerin, triethylene glycol, and trimethylolpropane.
The content of the water-soluble organic solvent (B) in the ink for inkjet recording is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably, from the viewpoint of improving storage stability and ejection properties of the ink. It is 30% by mass or more, and preferably 50% by mass or less, more preferably 47% by mass or less, and even more preferably 43% by mass or less.

The ink for inkjet recording preferably contains a surfactant (C) from the viewpoint of improving the wetting and spreading properties of the ink on the printing medium. Surfactants (C) include nonionic surfactants, anionic surfactants, amphoteric surfactants, silicone surfactants, fluorine surfactants, and the like. Among them, nonionic surfactants are preferred.
Nonionic surfactants include polyoxyalkylene alkyl ether surfactants, acetylene glycol surfactants, polyhydric alcohol surfactants, fatty acid alkanolamides, silicone surfactants, and fluorine surfactants. mentioned. Among these, one or more selected from polyoxyalkylene alkyl ether surfactants, acetylene glycol surfactants, and silicone surfactants are preferred, and silicone surfactants are more preferred.
The content of the surfactant (C) in the ink for inkjet recording is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of improving the wetting and spreading properties of the ink on the printing medium. It is more preferably 0.3% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[Method for producing ink for inkjet recording]
The inkjet recording ink is preferably produced by a method including Step III below in addition to Step I and Step II described above.
Step III: A step of mixing the pigment-containing resin composition obtained in Step II with a liquid compound to obtain an ink jet recording ink. Surfactants (C), bactericides and the like can be mentioned, preferably water, more preferably water and a water-soluble organic solvent (B). The liquid compounds may be used singly or in combination of two or more.
Any known method can be used as the mixing method in step III.
The mixing temperature is preferably 5°C or higher, more preferably 10°C or higher, and preferably 40°C or lower.
When the surfactant, disinfectant, or moisturizing agent is solid, it is preferable to dissolve it in water or the like to make it into a liquid state before mixing it with the pigment-containing resin composition.

The average particle size of the ink for inkjet recording is preferably 150 nm or less. When the average particle diameter is 150 nm or less, the number of coarse particles of about 300 nm can be reduced, and the ejection property of the ink can be improved. From this point of view, the average particle size of the ink is more preferably 140 nm or less, and even more preferably 130 nm or less. The average particle size of the ink is obtained by diluting the ink for inkjet recording with water so that the solid content concentration is 2 × 10 ^-4 mass%, and the average particle size obtained by the cumulant method analysis measured by the dynamic light scattering method. is. Specifically, it can be measured by the same method as for the average particle size of the water-based pigment dispersion (D) described in the Examples.

In the ink for inkjet recording, the ink for inkjet recording is diluted with water so that the solid content concentration is 0.25% by mass, and the particles per 1 mL are converted to the actual state of the ink measured by the number counting method. The number of particles with a diameter of 0.5 μm or more is preferably 5.00×10 ⁷ or less, more preferably 3.00×10 ⁷ or less, from the viewpoint of improving ink ejection properties.

(Physical properties of ink for inkjet recording)
The viscosity of the ink for inkjet recording at 32° C. is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, and still more preferably 5 mPa·s or more, from the viewpoint of improving the storage stability and ejection properties of the ink. And it is preferably 12 mPa·s or less, more preferably 9 mPa·s or less, and still more preferably 7 mPa·s or less. The viscosity is measured by the method described in Examples.
The pH of the ink for inkjet recording is preferably 7 or higher, more preferably 7.2 or higher, and still more preferably 7.5 or higher, from the viewpoint of improving storage stability and ejection properties of the ink. From the viewpoint of member resistance and skin irritation, it is preferably 11 or less, more preferably 10 or less, and even more preferably 9.5 or less. The pH is measured by the method described in Examples.

[Inkjet recording method]
The ink for inkjet recording can be loaded into a known inkjet recording apparatus and ejected as ink droplets onto a print medium to record an image or the like.
There are thermal type and piezo type ink jet recording apparatuses, and it is more preferable to use the ink for piezo type ink jet recording.
Usable print media include highly absorbent plain paper, low absorbent coated paper, and resin film. Examples of coated paper include general-purpose glossy paper, multicolor foam gloss paper, and the like. Examples of resin films include polyester films, polyvinyl chloride films, polypropylene films, and polyethylene films.

In the following examples and comparative examples, "parts" and "%" are "mass parts" and "mass%" unless otherwise specified.

(1) Measurement of weight average molecular weight of resin (a) A gel was prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol/L and 50 mmol/L, respectively, as an eluent. Permeation chromatography [Tosoh Corporation GPC device (HLC-8320GPC), Tosoh Corporation columns (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H), flow rate: 0.5 mL / min], standard 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 resin (a) with 10 mL of the eluent in a glass vial, stirring with a magnetic stirrer at 25° C. for 10 hours, filtering through a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantech Co., Ltd.). (manufactured by the company) was used.

(2) Measurement of average particle size of water-based pigment dispersion (D) Using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.), the particle size is measured by a dynamic light scattering method, and a cumulant method. Calculated by analysis. 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. For the measurement sample, the water-based pigment dispersion (D) was weighed into a screw tube (No. 5 manufactured by Maruem Co., Ltd.), water was added so that the solid content concentration was 2×10 ⁻⁴ %, and a magnetic stirrer was used. The mixture was used after being stirred at 25°C for 1 hour.

(3) Measurement of solid content concentration Using an infrared moisture meter "FD-230" (manufactured by Ketsuto Kagaku Kenkyusho Co., Ltd.), 5 g of the measurement sample is dried at 150 ° C., measurement mode 96 (monitoring time 2.5 minutes / fluctuation After drying under the condition of width 0.05%), the water content (%) of the measurement sample was measured, and the solid content concentration was calculated by the following formula.
Solid content concentration (%) = 100 - (moisture content (%) of measurement sample)

(4) Measurement of Volatile Substance Content 10.0 g of the pigment-containing resin composition was weighed into a glass petri dish having a diameter of 10 mm, and the mass was measured. After that, it was left at 40° C. for 12 hours, and the mass was measured again. The content of volatile substances was obtained by dividing the difference in mass before and after standing by the sample mass before standing.

(5) Measurement of water solubility of polyfunctional epoxy compound 90 parts by mass of ion-exchanged water and 10 parts by mass of a polyfunctional epoxy compound were added to a glass tube (25 mmφ x 250 mmh) at room temperature of 25°C, and the glass tube was heated to 25°C. It was allowed to stand for 1 hour in a constant temperature bath adjusted to . Then, the glass tube was vigorously shaken for 1 minute and then allowed to stand again in the constant temperature bath for 10 minutes. Next, the undissolved matter was weighed and the water content (% by mass) was calculated.

(6) Measurement of ink viscosity E-type viscometer (manufactured by Toki Sangyo Co., Ltd., model number: TV-25, using standard cone rotor 1 ° 34' × R24, rotation speed 50 rpm) The viscosity of the ink at 32 ° C. It was measured.

(7) Measurement of pH of ink Using a desktop pH meter “F-71” (manufactured by Horiba, Ltd.) using a pH electrode “6337-10D” (manufactured by Horiba, Ltd.), the pH of ink at 20 ° C. pH was measured.

<Production of Pigment-Containing Resin Composition>
Example 1-1
(Process I)
(Step I-1)
In a glass container, 25 parts of a styrene-acrylic copolymer (trade name: JONCRYL 690, weight average molecular weight: 16,500, acid value: 240 mgKOH/g, manufactured by BASF) is added as a resin (a) to methyl ethyl ketone ( Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (hereinafter also referred to as "MEK") 78.6 parts, and further 5N aqueous sodium hydroxide solution (sodium hydroxide solid content 16.9%) as a basic compound (b) , FUJIFILM Wako Pure Chemical Industries, Ltd., for volumetric titration) was added and neutralized so that the ratio of the number of moles of sodium hydroxide to the number of moles of the anionic groups in the resin (a) was 20%. (neutralization degree 20 mol%). Further, 400 parts of ion-exchanged water was added, and 75 parts of black pigment (carbon black, trade name: MONARCH 717, manufactured by Cabot) was added thereinto to obtain a pigment mixture.
The obtained pigment mixture was pre-dispersed by stirring for 60 minutes at 20° C. using a disper (trade name: Ultra Disper, manufactured by Asada Iron Works Co., Ltd.) under the condition of rotating the disper blade at 7,000 rpm. Using an Ultra Apex Mill (model: UAM-05, manufactured by Hiroshima Metal & Machinery Co., Ltd.) filled with zirconia beads with a bead diameter of 0.05 mm (trade name: YTZ Ball, Nikkato Co., Ltd.) at a filling rate of 85% Main dispersion was carried out for 1 hour at a rotation speed of 2,350 rpm. At this time, the temperature in the cylindrical container (vessel) was adjusted to 10°C or higher and 15°C or lower. Then, using a rotary evaporator, remove MEK at 60 ° C. under reduced pressure, further remove some water to measure the solid content, add ion-exchanged water to adjust to 20%, pigment dispersion ( d1) was obtained.
(Step I-2)
100 parts (solid content: 20%) of the resulting pigment dispersion (d1) was placed in a glass bottle with a screw cap, and trimethylolpropane polyglycidyl ether (trade name: Denacol EX-321, epoxy equivalent) was added as a cross-linking agent (c). : 140, water content 27% by mass, manufactured by Nagase ChemteX Co., Ltd.) (hereinafter also referred to as "EX-321") was added and tightly stoppered, and heated at 70 ° C. for 5 hours while stirring with a magnetic stirrer. . Next, the mixture was cooled to room temperature, filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation), and deionized water. was added to adjust the solid content concentration to 20% to obtain a water-based pigment dispersion (D1).

(Process II)
Aqueous pigment dispersion (D1) obtained in step I in a dry chamber (model: DRC-1000, manufactured by Tokyo Rikaki Co., Ltd.) connected to a freeze dryer (model: FDU-2110, manufactured by Tokyo Rikaki Co., Ltd.) 100 g was added, pre-frozen (normal pressure, −25° C., 1 hour), primary drying (5 Pa, −10° C., 9 hours), secondary drying (5 Pa, 25° C., 5 hours), and freeze-drying. . The resulting colored solid was pulverized to obtain a pigment-containing resin composition 1.

Example 1-2
In Example 1-1, instead of 75 parts of the black pigment, 75 parts of a cyan pigment (PB15:3, trade name: CFB6338JC, manufactured by Dainichi Seika Kogyo Co., Ltd.) was used in the same procedure to prepare an aqueous pigment dispersion (D2). A pigment-containing resin composition 2 was obtained in the same manner except that

Example 1-3
In Example 1-1, instead of 75 parts of black pigment, 75 parts of magenta pigment (PR122, trade name: CFR6114JC, manufactured by Dainichi Seika Kogyo Co., Ltd.) was used in the same manner to obtain a water-based pigment dispersion (D3). A pigment-containing resin composition 3 was obtained in the same manner except that

Examples 1-4
In Example 1-1, instead of 75 parts of black pigment, 75 parts of yellow pigment (PY74, trade name: FY7414, manufactured by Sanyo Color Co., Ltd.) was used in the same procedure to obtain an aqueous pigment dispersion (D4). obtained a pigment-containing resin composition 4 in the same manner.

Examples 1-5
In step 1 of Example 1-1, in place of 75 parts of black pigment, 75 parts of blue pigment (PB60, trade name: Paliogen Blue L6482, manufactured by BASF)) was used in the same procedure to prepare an aqueous pigment dispersion (D5). A pigment-containing resin composition 5 was obtained in the same manner except that

Comparative Example 1-1
After obtaining a pigment dispersion (d1) by performing the same operation as in step I-1 of Example 1-1, the aqueous pigment dispersion (D1 ) was replaced with the pigment dispersion (d1) to obtain a pigment-containing resin composition C1.

Comparative Example 1-2
In the process I of Example 1-1, zirconia beads with a bead diameter of 0.3 mm (trade name: YTZ balls, manufactured by Nikkato Co., Ltd.) were used instead of the zirconia beads with a bead diameter of 0.05 mm, and a water-based pigment was prepared in the same manner. Pigment-containing resin composition C2 was obtained in the same manner as above, except that dispersion (DC2) was obtained.

Comparative Example 1-3
In step I of Example 1-2, a water-based pigment was prepared in the same manner using zirconia beads with a bead diameter of 0.3 mm (trade name: YTZ balls, manufactured by Nikkato Co., Ltd.) instead of the zirconia beads with a bead diameter of 0.05 mm. Pigment-containing resin composition C3 was obtained in the same manner as above, except that water dispersion (DC3) was obtained.

Comparative Example 1-4
(Step I')
(Step I'-1)
25 parts of a styrene-acrylic copolymer (trade name: JONCRYL 690, weight-average molecular weight: 16,500, acid value: 240 mgKOH/g, manufactured by BASF) as a resin (a) in a glass container was added to MEK78. 6 parts, and further add 5.1 parts of 5N sodium hydroxide aqueous solution (sodium hydroxide solid content 16.9%, manufactured by Wako Pure Chemical Industries, Ltd., for volumetric titration) as a basic compound (b), resin Neutralization was carried out so that the ratio of the number of moles of sodium hydroxide to the number of moles of the anionic groups in (a) was 20% (degree of neutralization: 20 mol%). Further, 400 parts of ion-exchanged water was added, and 75 parts of black pigment (carbon black, trade name: MONARCH 717, manufactured by Cabot Corporation) was added thereinto to obtain a pigment mixture.
The resulting pigment mixture was stirred using a disper (trade name: Ultra Disper, manufactured by Asada Iron Works Co., Ltd.) at 20° C. for 60 minutes under the condition of rotating the disper blade at 7,000 rpm, and then using a rotary evaporator. , Under reduced pressure, MEK was completely removed at 60 ° C., a part of water was removed, the solid content was measured, ion-exchanged water was added to adjust to 20%, and a pigment dispersion (dC4) was obtained. .
Take 100 parts (solid content: 20%) of the obtained pigment dispersion (dC4) in a glass bottle with a screw cap, add 0.96 parts of EX-321 as a cross-linking agent (c), seal the bottle, and stir with a magnetic stirrer. The mixture was heated at 70° C. for 5 hours. After 5 hours, the mixture was cooled to room temperature and filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) fitted with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation), An aqueous pigment dispersion (DC4) having a solid concentration of 20% was obtained.

(Process II)
Pigment-containing resin composition C4 was obtained by using aqueous pigment dispersion (DC4) in place of aqueous pigment dispersion (D1) in step II of Example 1-1.

Comparative Example 1-5
In Comparative Example 1-4, instead of 75 parts of black pigment, 75 parts of cyan pigment (PB15:3, trade name: CFB6338JC, manufactured by Dainichiseika Kogyo Co., Ltd.) was used in the same procedure to prepare an aqueous pigment dispersion (DC5). A pigment-containing resin composition C5 was obtained in the same manner except that

(Measurement of average particle size of aqueous dispersion (α) by dynamic light scattering method)
Each pigment-containing resin composition obtained in Examples and Comparative Examples and water were weighed into a screw tube (model number: No. 5, manufactured by Maruem Co., Ltd.) so that the solid content concentration was 2×10 ⁻⁴ %. and stirred at 25° C. for 1 hour using a magnetic stirrer to obtain each aqueous dispersion (α). Using the obtained aqueous dispersion (α), a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.) is used to measure the particle size by a dynamic light scattering method and perform a cumulant method analysis. , the average particle size was calculated. 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 average particle size of the aqueous dispersion (α) tends to decrease as the dispersibility of the pigment is improved. In addition, the closer to 1 the ratio of the average particle size of the aqueous dispersion (α) to the average particle size of the aqueous pigment dispersion (D) [aqueous dispersion (α)/aqueous pigment dispersion (D)], the more Excellent dispersibility. Table 1 shows the results.

(Measurement of the number of particles with a particle size of 0.5 μm or more or 1 μm or more by a number counting method)
Each pigment-containing resin composition obtained in Examples and Comparative Examples and water were weighed into a screw tube (model number: No. 5, manufactured by Maruem Co., Ltd.) so that the solid content concentration was 0.25%, Stirred at 25° C. for 1 hour using a magnetic stirrer to obtain each aqueous dispersion (β). The obtained aqueous dispersion (β) was injected into "Accusizer 780APS System" (manufactured by PSS Japan Co., Ltd.) using a 5 mL syringe, and the number of particles was measured at a measurement temperature of 25°C.
The number of particles was calculated as the number of particles having a diameter of 0.5 μm or more and the number of particles having a diameter of 1.0 μm or more per 1 ml of an aqueous dispersion having a solid content of 20% of the pigment-containing resin composition. The smaller the value of these particle numbers, the fewer the coarse particles and the more excellent the jettability of the ink for inkjet recording. Table 1 shows the results.

In addition, each notation in Table 1 is as follows.
CB: Black pigment (carbon black, trade name: MONARCH 717, manufactured by Cabot)
PB15:3: Cyan pigment (PB15:3, trade name: CFB6338JC, manufactured by Dainichiseika Kogyo Co., Ltd.)
PR122: Magenta pigment (PR122, trade name: CFR6114JC, manufactured by Dainichiseika Kogyo Co., Ltd.)
PY74: Yellow pigment (PY74, trade name: FY7414, manufactured by Sanyo Color Co., Ltd.)
PB60: Blue pigment (PB60, trade name: Paliogen Blue L6482, manufactured by BASF)
*1: The number of particles of 0.5 μm or more, converted per 1 ml of an aqueous dispersion having a solid content of 20% of the pigment-containing resin composition *2: Converted per 1 ml of an aqueous dispersion having a solid content of 20% of the pigment-containing resin composition The number of particles of 1.0 μm or more

From Table 1, it can be seen that the pigment-containing resin compositions of Examples are superior to those of Comparative Examples in terms of pigment dispersibility and the number of coarse particles is reduced.

(Breeding of microorganisms)
After each pigment-containing resin composition obtained in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5 was stored at 40° C. for 1 month, the pigment-containing resin was examined for the presence or absence of growth of microorganisms. The appearance of the composition was visually confirmed, and the presence or absence of odor was further confirmed.
Although the pigment-containing resin compositions obtained in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5 do not contain a disinfectant component, the It was confirmed that there was no change in appearance and no abnormal odor even after months of storage.

<Production of inkjet recording ink>
Example 2-1
(Process III)
8.3 g of the pigment-containing resin composition 1 obtained in Example 1-1, 35.0 g of propylene glycol (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., reagent) as a water-soluble organic solvent (B) and diethylene glycol monobutyl ether (Fuji Film Wako Pure Chemical Industries, Ltd., reagent) 5.0 g, silicone surfactant (trade name: KF6011, Shin-Etsu Chemical Co., Ltd., polyether-modified silicone) 0.50 g, and ion-exchanged water 51.2 g After adding to a glass container and stirring with a magnetic stirrer for 1 hour, a 25 mL needleless syringe (manufactured by Terumo Corporation) fitted with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation). to obtain Inkjet recording ink I1.

Examples 2-2 to 2-5 and Comparative Examples 2-1 to 2-5
In Example 2-1, instead of the pigment-containing resin composition 1 obtained in Example 1-1, pigment-containing resin compositions 2 to 5 obtained in Examples 1-2 to 1-5 and Comparative Example 1 Inkjet recording inks I2 to I5 and IC1 to IC5 were obtained in the same manner as in Example 2-1, except that the pigment-containing resin compositions C1 to C5 obtained in -1 to 1-5 were used.

<Evaluation of inkjet recording ink>
(Ejectability)
In an environment with a temperature of 25 ± 1 ° C. and a relative humidity of 50 ± 5%, an inkjet printer (manufactured by Ricoh Co., Ltd., model number: SG-2010L, piezo system) was charged with the ink for inkjet recording obtained in Examples and Comparative Examples. , solid printing of 10 cm×10 cm was performed on plain paper. Next, while the printer was still filled with ink, it was left unprotected for 30 minutes without protecting the ink jet nozzle surface, and then the same printing was performed to visually check for chipping in the printed area and to compare the image quality with that before leaving. Ejectability was evaluated according to the evaluation criteria of Table 2 shows the results.
〔Evaluation criteria〕
3: No chipping of the printed portion was observed, and no deterioration in image quality was observed.
2: Although chipping of the printed portion is observed, deterioration of image quality is not confirmed and can be used practically.
1: Missing printed portion is observed, image quality is remarkably deteriorated, and practically unusable.

(Redispersibility)
10 μL of each ink jet recording ink obtained in Examples and Comparative Examples is dropped onto a slide glass using a micropipette and left in an environment of 60° C. and 40% RH for 24 hours to evaporate and dry the ink. A solid was obtained.
Separately, 35.0 g of propylene glycol, 5.0 g of diethylene glycol monobutyl ether, 0.50 g of a silicone surfactant (KF6011), and 51.2 g of ion-exchanged water were added to a glass container and stirred with a magnetic stirrer for 1 hour to redisperse. An ink vehicle was prepared for characterization.
200 μL of the ink vehicle was dropped onto the solid matter on the slide glass obtained above, and the redispersibility of the solid matter was visually observed and evaluated according to the following evaluation criteria. Table 2 shows the results.
〔Evaluation criteria〕
3: Solids were uniformly redispersed.
2: Solid matter was redispersed, but there was a residue.
1: Solids were not redispersed.

From Table 2, it can be seen that the ink jet recording inks of Examples are superior in jettability to those of Comparative Examples. In addition, the inkjet recording inks of Examples are excellent in redispersibility as compared with those of Comparative Examples, so that even when the ink is solidified, it can be quickly redispersed by the ink vehicle.

INDUSTRIAL APPLICABILITY The pigment-containing resin composition of the present invention is free from deterioration due to the generation of microorganisms, has excellent pigment dispersibility, and contains few coarse particles. , and can be suitably used for printing inks such as inkjet recording inks. In addition, it can be used particularly as an ink for inkjet recording because of its excellent ejection property of ink in inkjet recording.

Claims (9)

A pigment-containing resin composition containing a pigment and a resin (A), which satisfies the following conditions 1 to 4 and is used for an ink for inkjet recording.
Condition 1: The resin (A) is a resin (a) having an anionic group with an acid value of 220 mgKOH/g or more and 320 mgKOH/g or less, and a cross-linking agent having two or more cross-linkable functional groups that react with the anionic group. A resin having a crosslinked structure formed by (c) and (c), and at least part of the anionic groups of the resin are neutralized with an alkali metal compound as the basic compound (b).
Condition 2: The pigment-containing resin composition is a solid in which the content of volatile substances in the pigment-containing resin composition is 1% by mass or less.
Here, a "volatile substance" is a substance having a vapor pressure or sublimation pressure of more than 1 kPa at 25°C, and includes water.
Condition 3: A water dispersion (α) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 2 × 10 ^-4 % by mass, measured by dynamic light scattering method. The average particle size obtained by cumulant method analysis is 150 nm or less.
Condition 4: The content of the pigment in the aqueous dispersion (β) obtained by dispersing the pigment-containing resin composition in water so that the concentration of the pigment-containing resin composition is 0.25% by mass, as measured by the number counting method. The number of particles having a particle size of 0.5 μm or more is 1.00×10 ⁹ or less per 1 ml of an aqueous dispersion having a solid content of 20% by mass of the resin composition. 2. The pigment-containing resin composition according to claim 1, wherein the resin (A) is a styrene-acrylic resin. 3. The pigment-containing resin composition according to claim 1, wherein the mass ratio of the pigment to the resin (A) [pigment/resin (A)] is 60/40 or more and 90/10 or less. 4. The pigment-containing resin composition according to any one of claims 1 to 3, wherein the cross-linking agent (c) is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group having 3 to 8 carbon atoms . A method for producing a pigment-containing resin composition according to any one of claims 1 to 4, comprising the following Step I and Step II.
Step I: Water, a pigment, a resin (a) having an anionic group, a basic compound (b) that neutralizes the anionic group, and two or more crosslinkable functional groups that react with the anionic group. A step of mixing and dispersing the cross-linking agent (c) having and obtaining an aqueous pigment dispersion (D) Step II: Drying the aqueous pigment dispersion (D) obtained in Step I to reduce the volatile substance content to 1 Step of obtaining a pigment-containing resin composition that is a solid of mass% or less Here, the aqueous pigment dispersion (D) contains the pigment and the resin (A), and is measured by a cumulant method by a dynamic light scattering method The average particle diameter determined by analysis is 150 nm or less. 6. The method for producing a pigment-containing resin composition according to claim 5 , wherein the drying treatment in step II is freeze-drying . A method for producing an ink jet recording ink , comprising the pigment-containing resin composition according to any one of claims 1 to 4, and comprising the following steps I to III.
Step I: Water, a pigment, a resin (a) having an anionic group, a basic compound (b) that neutralizes the anionic group, and two or more crosslinkable functional groups that react with the anionic group. A step of mixing and dispersing the cross-linking agent (c) having and obtaining an aqueous pigment dispersion (D) Step II: Drying the aqueous pigment dispersion (D) obtained in Step I to reduce the volatile substance content to 1 Step of obtaining a pigment-containing resin composition that is solid at mass % or less Step III: Step of mixing the pigment-containing resin composition obtained in Step II with a liquid compound to obtain an inkjet recording ink Here, a water-based pigment dispersion The body (D) contains the pigment and the resin (A), and has an average particle size of 150 nm or less as determined by the cumulant method analysis in the dynamic light scattering method . 8. The method for producing an ink jet recording ink according to claim 7, wherein the drying treatment in step II is freeze-drying. 9. The method for producing an ink jet recording ink according to claim 7, wherein the liquid compound is water and a water-soluble organic solvent (B).