JP2012001675A - Aqueous dispersion for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous dispersion for inkjet recording excellent in redispersibility, and an aqueous ink for inkjet recording superior in fixing property to a recording paper.SOLUTION: (1) This aqueous dispersion for inkjet recording includes crosslinked polymer particles obtained by crosslinking polymer particles containing colorant using a crosslinking agent, wherein the polymer which constitutes the polymer particles containing the colorant has a polymer (A) that includes: a constitutional unit derived from a salt-forming group-containing monomer (a); a constitutional unit derived from polypropylene glycol mono(meth)acrylate (b); and a constitutional unit derived from a specific nonionic monomer (c), in which the difference between a solubility parameter (SP value) of the monomer (b) and that of monomer (c) is 0.5-2.0. (2) The aqueous ink for the inkjet recording contains the aqueous dispersion.

Description

  The present invention relates to an aqueous dispersion for inkjet recording and an aqueous ink containing the same.

The ink jet recording method is a recording method in which characters and images are obtained by ejecting and adhering ink droplets directly from a very fine nozzle to a recording member. This method is remarkably widespread because it has many advantages that full color is easy and inexpensive, plain paper can be used as a recording member, and there is no contact with the object to be printed. Among these, pigment-based inks have become mainstream from the viewpoint of light resistance and water resistance of printed matter, and are preferably used in home inkjet printers.
In recent years, the range of use of ink jet printers has expanded from home use to office use and commercial printing use, and high speed has become a technology trend. As a method for realizing high speed, a method of increasing the printing speed by reducing the number of printings by increasing the volume of ink droplets or improving the print head is employed.
The problem with high-speed printing is that, since conventional printing cannot be performed twice or three times, sufficient dispersion stability and ejection stability are imparted so as not to cause deterioration in printing quality such as blurring or missing. There is a demand for an ink that can develop a high color density so that a high print density can be obtained by one-time printing, and can suppress penetration into the paper, particularly when printed on plain paper.

Various proposals have been made for improving the dispersion stability and storage stability of pigment-based aqueous dispersions for inkjet recording and aqueous inks.
For example, in Patent Documents 1 and 2, an aqueous ink containing an aqueous dispersion of polymer particles of a water-insoluble vinyl polymer containing a colorant, wherein the vinyl polymer is a specific polyalkylene glycol mono (meth) acrylate, An aqueous ink which is a vinyl polymer obtained by polymerizing a monomer composition containing a salt-forming group-containing monomer and a monomer copolymerizable therewith is disclosed.
Patent Document 3 discloses an aqueous dispersion for ink jet recording containing crosslinked polymer particles containing an organic pigment and a pigment derivative having a polar group.
Patent Document 4 discloses a water-based ink containing crosslinked polymer particles containing a colorant, the water content being 60% by weight or less, and an anionic property neutralized with a base per 1 g of the crosslinked polymer. An aqueous ink for ink-jet recording having a base amount of 0.5 mmol / g or more is disclosed.
However, the aqueous dispersions and aqueous inks of Patent Documents 1 to 4 are not sufficiently satisfactory in redispersibility and fixability to recording paper. Here, redispersibility refers to the property that, in the ink jet recording method, ink that has adhered to and dried around the nozzle holes that eject ink droplets is re-dissolved or re-dispersed in the ink. If the redispersibility is poor, coarse particles are generated in the ink, causing a problem that the discharge property is deteriorated.

JP 20042662 A JP 2004-75988 A JP 2008-156465 A International Publication No. 2009/025287

  An object of the present invention is to provide an aqueous dispersion for ink jet recording excellent in redispersibility and an aqueous ink for ink jet recording excellent in fixability to recording paper.

The present inventors colored cross-linked polymer particles obtained by cross-linking polymers containing structural units derived from two or more specific nonionic monomers having a difference in solubility parameter (SP value) of 0.5 to 2.0. It has been found that the redispersibility of the aqueous dispersion can be improved and the fixing property of the aqueous ink to the recording paper can be improved by including an agent.
That is, the present invention provides the following [1] and [2].
[1] An aqueous dispersion of crosslinked polymer particles obtained by crosslinking polymer particles containing a colorant with a crosslinking agent, wherein the polymer constituting the polymer particles containing the colorant is a salt-forming group-containing monomer (a ) Derived structural units, polypropylene glycol mono (meth) acrylate (b) derived structural units represented by the following formula (1), and monomers represented by the following formulas (2) to (4). A polymer (A) comprising a constituent unit derived from at least a nonionic monomer (c) and having a difference in solubility parameter (SP value) between the monomers (b) and (c) of 0.5 to 2.0. An aqueous dispersion for ink jet recording, comprising:

（式中、Ｒ¹は水素原子又はメチル基を示し、ｍは２〜２０の数を示す。）

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and m represents a number of 2 to 20.)

（式中、Ｒ¹は前記と同じであり、Ｒ²は水素原子、又は炭素数１〜２０のアルキル基又は炭素数１〜９のアルキル基を有するフェニル基を示し、ｎは２〜３０の数を示す。）

(In the formula, R ¹ is the same as above, R ² represents a hydrogen atom, a phenyl group having a C 1-20 alkyl group or a C 1-9 alkyl group, and n is 2-30. Indicates the number.)

（式中、Ｒ¹は前記と同じであり、Ｒ³は炭素数１〜２０のアルキル基又は炭素数１〜９のアルキル基を有するフェニル基を示し、ｐは２〜３０の数を示す。）

(In the formula, R ¹ is the same as defined above, R ³ represents a phenyl group having an alkyl group or an alkyl group having 1 to 9 carbon atoms having 1 to 20 carbon atoms, p is the number of 2 to 30. )

（式中、Ｒ¹及びＲ²は前記と同じであり、ｑ及びrはそれぞれ１〜３０の数を示す。オキシエチレン基及びオキシプロピレン基はブロック付加又はランダム付加している。）
〔２〕前記〔１〕の水系分散体を含有するインクジェット記録用水系インク。

(In the formula, R ¹ and R ² are the same as described above, and q and r each represent a number of 1 to 30. The oxyethylene group and the oxypropylene group are block-added or randomly added.)
[2] An aqueous ink for ink-jet recording containing the aqueous dispersion of [1].

  According to the present invention, the aqueous dispersion for inkjet recording excellent in storage stability and redispersibility, and the ink viscosity is low, excellent in storage stability, excellent in high print density and ejection reliability corresponding to high-speed printing, It is possible to provide an aqueous ink for ink-jet recording having little change in light absorption characteristics and excellent fixability to recording paper.

The aqueous dispersion for inkjet recording of the present invention is an aqueous dispersion of crosslinked polymer particles obtained by crosslinking polymer particles containing a colorant with a crosslinking agent, and the polymer is derived from the salt-forming group-containing monomer (a). 1 or more types selected from the structural units derived from polypropylene glycol mono (meth) acrylate (b) represented by the following formula (1) and monomers represented by the following formulas (2) to (4) A nonionic monomer (c) -derived structural unit, and a polymer (A) having a solubility parameter (SP value) difference of 0.5 to 2.0 between the monomers (b) and (c). In addition, the aqueous ink for inkjet recording of the present invention is characterized by containing the aqueous dispersion.
Conventionally, the knowledge for creating a sufficient compatibility state by mixing a colorant and a polymer has not been known. In the present invention, the polymer that disperses the colorant has a solubility parameter (SP value) difference of 0.5 to 2.0, that is, derived from two or more specific nonionic monomers having moderately different compatibility. By using a polymer containing a structural unit, the wettability and adsorptivity between the colorant and the polymer can be optimized, the adhesion of the polymer to the colorant can be improved, and the colorant can be stably dispersed. It is considered that an aqueous dispersion excellent in dispersibility and an aqueous ink excellent in fixability to recording paper can be obtained. Further, the aqueous dispersion has excellent storage stability, and the aqueous ink has excellent effects such as storage stability, high print density, ejection reliability, and little change in light absorption characteristics.
Hereafter, each component etc. which are used for this invention are demonstrated.

<Colorant>
Examples of the colorant used in the present invention include pigments and hydrophobic dyes from the viewpoint of improving the water resistance of water-based inks. Among them, pigments are used in order to develop high weather resistance, which has recently been strongly demanded. Is preferred. The pigment may be either an organic pigment or an inorganic pigment. If necessary, extender pigments can be used in combination.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed. Moreover, solid solution pigments, such as a quinacridone solid solution pigment, can also be used.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Of these, carbon black is preferred particularly for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of extender pigments include silica, calcium carbonate, and talc.

The hydrophobic dye is not particularly limited as long as it can be emulsified by a water-soluble polymer or contained in a water-soluble polymer. The hydrophobic dye is dissolved in an amount of 2 g / L or more, preferably 20 to 500 g / L (25 ° C.) with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer from the viewpoint of efficiently containing the dye in the polymer. What to do is desirable.
Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable from the viewpoint of improving the fixability to recording paper. Examples of the oil-soluble dye include C.I. I. Solvent Black, C.I. I. Solvent Yellow, C.I. I. Solvent Red, C.I. I. Solvent Violet, C.I. I. Solvent Blue, C.I. I. Solvent Green, and C.I. I. One or more types of products selected from the group consisting of Solvent Orange are listed, which are commercially available from Orient Chemical Co., Ltd., BASF Corp. and others.
The above colorants can be used alone or in admixture of two or more at any ratio. Examples of yellow colorants include C.I. I. An azo pigment such as CI Pigment Yellow 74 can be used.

(CI Pigment Yellow 74)
C. I. Examples of the pigment yellow 74 (hereinafter, also referred to as “PY74 (A)”) include an acetoacetyl allylide monoazo pigment. Its chemical name is 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) -3-oxobutanamide and has a structure represented by the following formula (5). A compound.
PY74 (A) is available from manufacturers such as DIC Corporation, Dainichi Seika Kogyo Co., Ltd., Sanyo Dye Co., Ltd., Toyo Ink Manufacturing Co., Ltd.

(Other azo pigments (B))
In the present invention, in order to refine PY74 (A) and improve storage stability, an azo pigment (B) represented by the following formula (6) (hereinafter also referred to as “azo pigment derivative”) is used in combination. It is preferable.

In formula (6), R ^{4 and} R ⁵ each independently represents an aryl group optionally having a substituent selected from a methoxy group and a nitro group, and at least one of R ^{4 and} R ⁵ is a sulfone group. Has an acid group. Among these, the azo pigment represented by the following formula (7) is preferable from the viewpoint of improving the printing density of the water-based ink.

In formula (7), R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms or an aminoalkyl group which may have a substituent, and R ⁸ represents a single bond. Represents a methylene group or an ethylene group.
The azo pigment represented by the formula (7) has a structure in which a sulfonamide group (—SO ₂ NR ⁶ R ⁷ ) and a sulfonic acid group (—R ⁸ —SO ₃ H) are substituted.

Among the sulfonamide groups (—SO ₂ NR ⁶ R ⁷ ), as an amine residue represented by —NR ⁶ R ⁷ , the printing density and storage stability are improved, and water-based inks when used as an ink are reduced. From the viewpoint of increasing viscosity and suppressing changes in light absorption characteristics, —NH (CH ₂ ) _k NR ⁹ R ¹⁰ is preferable.
Among these, N-alkyl (C1-3) -3-aminopropyl group and N, N-dialkyl (from the viewpoint of reducing the viscosity of the water-based ink when the ink is used and suppressing the change in light absorption characteristics) A C1-C3) -3-aminopropyl group is preferable.
Examples of the sulfonic acid group (—R ⁸ —SO ₃ H) include a sulfonic acid group (—SO ₃ H), a methylene sulfonic acid group (—CH ₂ —SO ₃ H), and an ethylene sulfonic acid group (—CH ₂ CH ₂ —). SO ₃ H) but may be mentioned, sulfonic acid group (-SO ₃ H) is more preferable. When R ⁸ is a single bond, it means that a sulfonic acid group (—SO ₃ H) is directly bonded to the benzene ring.

  In the present invention, for example, as a yellow colorant, a pigment mixture of PY74 (A) and an azo pigment derivative, particularly a pigment mixture of PY74 (A) and an azo pigment derivative represented by the above formula (7) is used. From the viewpoint of improving the printing density of the water-based ink, it is more preferable.

<Polymer>
The water-based dispersion and water-based ink of the present invention include, as a polymer, a structural unit derived from a salt-forming group-containing monomer (a) and a polypropylene glycol mono (meth) acrylate (b) represented by the formula (1). Unit and a constituent unit derived from one or more nonionic monomers (c) selected from the monomers represented by the formulas (2) to (4), and solubility parameters of the monomers (b) and (c) The polymer (A) containing the structural unit derived from 2 or more types of nonionic monomers whose difference of (SP value) is 0.5-2.0 is included.
In the water-based dispersion and water-based ink of the present invention, the polymer (A) containing two or more kinds of nonionic monomers (b) and (c) derived structural units is water from the viewpoint of both storage stability and redispersibility. It is preferably an insoluble polymer (y), preferably containing a water-insoluble polymer (y) alone, or preferably containing both the water-insoluble polymer (y) and the water-soluble polymer (x). From the viewpoint of improving the atomization of the dispersion and the water-based ink and improving the printing density, it is preferable to contain the water-insoluble polymer (y) alone.
Here, the “water-insoluble polymer (y)” and the “water-soluble polymer (x)” mean that when the polymer has a salt-forming group, the salt-forming group of the polymer is converted into acetic acid or hydroxylated according to the type of the polymer. When 100 g of pure water at 25 ° C. is added to 10 g of 100% neutralized with sodium and sufficiently stirred, the polymer is “water-soluble polymer (x)” in the present invention. In the case of using a commercially available polymer, or in the case of a polymer neutralized with a neutralizing agent other than acetic acid or sodium hydroxide at the time of synthesis, acetic acid or sodium hydroxide is used when the polymer does not have a degree of neutralization of 100%. In addition, the solubility is judged as 100% neutralization.
When the solubility test is performed and the polymer has a portion that does not dissolve at a neutralization degree of 100%, since pure water hardly penetrates into the polymer, the following procedure (specifically, the method of the example) Thus, the water-insoluble polymer (y) and the water-soluble polymer (x) can be separated.
That is, a polymer is dissolved in an organic solvent such as methyl ethyl ketone in advance, 100% neutralized product is dropped into pure water, and the aqueous dispersion having a concentration of 10% by weight is removed by centrifugation. The polymer separated and precipitated by “1” is defined as “water-insoluble polymer (y)”, and the dissolved polymer as “water-soluble polymer (x)”. However, the weight% of each of the “water-insoluble polymer (y)” and “water-soluble polymer (x)” in the polymer is rounded off to the first decimal place.

(Water-insoluble polymer (y))
In the present invention, the water-insoluble polymer (y) is used from the viewpoint of atomizing the pigment mixture, improving the dispersibility, mainly improving the storage stability of the aqueous dispersion, and increasing the printing density of the aqueous ink. It is preferable. The water-insoluble polymer (y) is preferably a vinyl polymer obtained by addition polymerization of a vinyl monomer or a urethane polymer having a urethane bond, and is represented by the salt-forming group-containing monomer (a) and the formula (1). A nonionic monomer (b) and at least one nonionic monomer (c) selected from the monomers represented by the formulas (2) to (4), and solubility parameters of the monomers (b) and (c) A vinyl polymer obtained by copolymerizing a monomer mixture containing two or more nonionic monomers having a difference in (SP value) of 0.5 to 2.0 (hereinafter also simply referred to as “monomer mixture”) is more preferable.
This water-insoluble vinyl polymer is a polymer (A) having structural units derived from the components (a) to (c).

[Salt-forming group-containing monomer (a)]
The salt-forming group-containing monomer (a) (hereinafter also referred to as “component (a)”) is used from the viewpoint of enhancing the dispersibility of the resulting polymer particles.
Examples of the salt-forming group-containing monomer (a) include cationic monomers and anionic monomers, with anionic monomers being preferred.
Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group, and among them, a carboxy group is preferable.

Representative examples of the cationic monomer include amine-containing monomers and ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.
Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, and the like. It is done.
In the present specification, “(meth) acrylate” refers to acrylate and / or methacrylate.
Among the anionic monomers, a carboxylic acid monomer is preferable and acrylic acid and methacrylic acid are more preferable from the viewpoint of improving the dispersibility of the polymer particles.

[Polypropylene glycol mono (meth) acrylate (b) represented by formula (1)]
As the polypropylene glycol mono (meth) acrylate (b) (hereinafter also referred to as “component (b)”), a monomer represented by the following formula (1) is used from the viewpoint of improving the redispersibility of the resulting polymer particles.

In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and the average added mole number m is 2 to 20, preferably 2 to 18.
Specific examples of the commercially available component (b) include Blemmer PP-500 (manufactured by NOF Corporation) (R ¹ is a methyl group, m is an added mole number 9, SP value: 9.57), 800 ( R ¹ is a methyl group, the added mole number m is 12, SP value: 9.37), 1000 (R ¹ is a methyl group, added mole number m is 5, SP value: 10.13), and the like.

[Nonionic monomer (c)]
The nonionic monomer (c) (hereinafter also referred to as “component (c)”) is used from the viewpoint of enhancing the adsorptivity of the resulting polymer particles to the colorant.
As the nonionic monomer (c), one or more monomers selected from monomers (c-1) to (c-3) represented by the following formulas (2) to (4) are used.
One or more nonionic monomers selected from the nonionic monomer (b) represented by the formula (1) and the monomers (c-1) to (c-3) represented by the formulas (2) to (4) The difference in solubility parameter (SP value) from (c) is 0.5 to 2.0, preferably 0.5 to 1.5, and more preferably 0.7 to 1.5. In the present invention, when the nonionic monomer (c) includes a plurality of nonionic monomers selected from the above (c-1) to (c-3), any one type of nonionic monomer (c) is used. The difference in solubility parameter (SP value) with the nonionic monomer (b) may be 0.5 to 2.0, but preferably the difference with all nonionic monomers (c) is 0.5 to 2.0. 2.0 is preferable.
Here, the solubility parameter (SP value) is defined by the square root of the ratio between the cohesive energy density and the molecular volume, as shown by the following formula.
SP value ((cal / cm ³ ) ^1/2 ) = (ΔE / ΔV) ^1/2
In the above formula, ΔE represents the cohesive energy density, and ΔV represents the molecular volume. The value can be calculated by the method of Fedors (“Coating Fundamental Chemistry” by Yuji Harasaki, Tsuji Shoten, p. 54, (1986)). In the present invention, the solubility parameter of the nonionic monomer (SP (Value) can be calculated from the chemical structural formula of the homopolymer based on the above literature. Moreover, SP value in the case of having two or more nonionic monomer units is calculated | required as a weighted average of SP value of each monomer unit.
When the difference in solubility parameter (SP value) is less than 0.5, the polymer hardly adheres to the surface of the colorant, becomes a polymer emulsion, increases the ink viscosity, and deteriorates the stability.
On the other hand, if the difference in solubility parameter (SP value) exceeds 2.0, an aqueous dispersion containing a high concentration of the colorant cannot be stably maintained, and is likely to aggregate due to the interaction between the colorants. Is non-uniform, the state of adhesion of the polymer to the colorant becomes insufficient, and it becomes difficult to obtain polymer particles containing a uniform colorant with good dispersion stability.
The solubility parameter (SP value) of the polypropylene glycol mono (meth) acrylate (b) is preferably 9.11 to 11.37, more preferably 9.15 to 10.77, still more preferably 9. 20 to 10.50. The solubility parameter (SP value) of the nonionic monomer (c) is preferably 8.57 to 12.11, more preferably 8.57 to 10.37, and still more preferably 8.70 to 10.37. It is.

[Nonionic monomer (c-1)]
The nonionic monomer (c-1) (hereinafter also referred to as “component (c-1)”) is represented by the following formula (2).

In formula (2), R1 is the same as described above, R2 represents a hydrogen atom, a phenyl group having a C1-20 alkyl group or a C1-9 alkyl group, and n is 2-30. Indicates a number. In addition, R1 in Formula (2) is a hydrogen atom or a methyl group independently of polypropylene glycol mono (meth) acrylate (b).
R2 is preferably a phenyl group having an alkyl group having 1 to 20 carbon atoms or an alkyl group having 1 to 9 carbon atoms, more preferably 1 carbon atom, from the viewpoint of improving the dispersibility of the aqueous dispersion and the aqueous ink. A phenyl group having an alkyl group of -18 or an alkyl group having 1 to 2 carbon atoms. The average added mole number n is preferably 2-18.
Preferred examples of the component (c-1) include methoxypolyethylene glycol (n = 2 to 16) mono (meth) acrylate, octoxypolyethylene glycol (n = 2 to 16) mono (meth) acrylate, lauroxypolyethylene glycol ( n = 2-16) mono (meth) acrylate, stearoxy polyethylene glycol (n = 2-16) mono (meth) acrylate, phenoxy polyethylene glycol (n = 2-16) mono (meth) acrylate, and the like.

As a specific example of commercially available (c-1) component, NOF's Blemmer PME-100 (R ¹ is methyl group, R ² is methyl group, addition mole number n is 2, SP value: 9.55), 200 (R ¹ is a methyl group, R ² is a methyl group, addition mole number n is 4, SP value: 9.49), 400 (R ¹ is a methyl group, R ² is a methyl group, Added mole number n is 9, SP value: 9.44), PLE-200 (R ¹ is methyl group, R ² is lauryl group, added mole number n is 4, SP value: 9.10), PSE-200 ( R ¹ is a methyl group, R ² is a stearyl group, addition mole number n is 4, SP value: 9.00), 400 (R ¹ is a methyl group, R ² is a stearyl group, addition mole number n is 9, SP Value: 9.10), NK ester M-20G of Shin-Nakamura Chemical Co., Ltd. (R ¹ is a methyl group, R ² is a methyl group, and the added mole number n is 2, SP value: 9.55), 40G (R ¹ is methyl group, R ² is methyl group, addition mole number n is 4, SP value: 9.49), 60 G (R ¹ is methyl group, R ² is a methyl group, addition mole number n is 6, SP value: 9.46), 90G (R ¹ is methyl group, R ² is methyl group, addition mole number n is 9, SP value: 9.44), NK ester EH-4E (R ¹ is methyl group, R ² is 2-ethylhexyl group, addition mole number n is 4, SP value: 9.13), 8E (R ¹ is methyl group, R ² is 2-ethylhexyl) Group, addition mole number n is 8, SP value: 9.20), NK ester PHG-2G (R ¹ is methyl group, R ² is phenyl group, addition mole number n is 2, SP value: 10.33), the 3G (R ¹ is methyl, R ² is a phenyl group, addition molar number n is 3, SP value: 10.19), the 6G (R ¹ is methyl, R ² is Fe Group, addition molar number n is 6, SP value: 9.94), and the like.

[Nonionic monomer (c-2)]
The nonionic monomer (c-2) (hereinafter also referred to as “component (c-2)”) is represented by the following formula (3).

In formula (3), is the same as above, R ³ represents a phenyl group having an alkyl group having 1 to 20 carbon atoms or an alkyl group having 1 to 9 carbon atoms, and p represents a number from 2 to 30.
R ³ is preferably a phenyl group having an alkyl group having 1 to 20 carbon atoms or an alkyl group having 1 to 9 carbon atoms, more preferably a carbon number, from the viewpoint of improving the dispersibility of the aqueous dispersion and the aqueous ink. A phenyl group having 1 to 18 alkyl groups or an alkyl group having 1 to 2 carbon atoms. The average added mole number p is preferably 2-18.
Preferred examples of the component (c-2) include methoxypolypropylene glycol (n = 2-16) mono (meth) acrylate, octoxypolypropylene glycol (n = 2-16) mono (meth) acrylate, phenoxypolypropylene glycol (p = 2 to 16) Mono (meth) acrylate and the like.
Specific examples of the commercially available component (c-2) include Blemmer PAP-350 manufactured by NOF Corporation (R ¹ is a methyl group, R ³ is a phenyl group, the average added mole number p is 6, SP value) : 9.33), NK ester EH-4P from Shin-Nakamura Chemical Co., Ltd. (R1 is methyl group, R3 is 2-ethylhexyl group, added mole number p is 4, SP value: 8.80), Hitachi Chemical Co., Ltd. FA-P200M (R ¹ is a methyl group, R ³ is a methyl group, the added mole number p is 4, SP value: 8.57), and the like.

[Nonionic monomer (c-3)]
The nonionic monomer (c-3) (hereinafter also referred to as “(c-3) component”) is represented by the following formula (4).

In formula (4), R ¹ and R ² are the same as described above, and q and r each represent a number of 1 to 30. The oxyethylene group and the oxypropylene group are added in blocks or randomly.
A preferable range of R2 in the formula (4) is the same as described above from the viewpoint of improving the dispersibility of the aqueous dispersion and the aqueous ink, and the average added mole numbers q and r are preferably 1 to 18 respectively. Preferably each is 1-12.
Preferred examples of the component (c-3) include methoxypoly (ethylene glycol (q = 1 to 10) / propylene glycol (r = 1 to 10)) mono (meth) acrylate, octoxypoly (ethylene glycol (q = 1 to 10). ) · Propylene glycol (r = 1 to 10)) mono (meth) acrylate, phenoxypoly (ethylene glycol (q = 1 to 10) · Propylene glycol (r = 1 to 10)) mono (meth) acrylate, poly (ethylene) Glycol (q = 1-10) / propylene glycol (r = 1-10)) mono (meth) acrylate and the like.
Specific examples of commercially, available to (c-3) component, Blemmer 43 PMEP-650 (R ¹ is a methyl group NOF CORPORATION, R2 is a methyl group, addition molar number q is 6, addition molar number r 6, SP value: 9.06), BLEMMER 43PAPE-600B (R ¹ is a methyl group, R2 is a phenyl group, addition molar number q is 6, addition molar number r is 6, SP value: 9.34), BLEMMER 50POEP-800B (R ¹ is a methyl group, R2 is 2-ethylhexyl group, addition molar number q is 8, addition molar number r is 6, SP value: 9.19), Blenmer 10PEP-550B (R ¹ is a methyl group, R2 is a hydroxyl group, addition mole number q is 1, addition mole number r is 8, SP value: 9.65), BLEMMER 50PEP-300 (R ¹ is a methyl group, R2 is a hydroxyl group, addition mole number q is 4, addition mole) Number r is 3, SP value: 10. 23), Blenmer 70PEP-350B (R ¹ is a methyl group, R2 is a hydroxyl group, addition molar number q is 5, addition molar number r is 2, SP value: 10.37), Blenmer 75PEP-450B (R ¹ is a methyl group , R2 is a hydroxyl group, the added mole number q is 8, the added mole number r is 2, SP value: 10.14).

[Hydrophobic monomer (d)]
The monomer mixture preferably contains a hydrophobic monomer (d) (hereinafter, also referred to as “component (d)”) from the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink.
The hydrophobic monomer (d) is used from the viewpoint of increasing the affinity of the polymer for the colorant. Examples of hydrophobic monomers include alkyl (meth) acrylates, aromatic group-containing monomers, and the like, and aromatic group-containing monomers are preferred from the viewpoint of increasing affinity with the colorant and enhancing dispersibility and storage stability.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates.
Examples of the aromatic group-containing monomer include styrene monomers and aromatic group-containing (meth) acrylates. As the styrene monomer, styrene and 2-methylstyrene are preferable from the viewpoint of obtaining a high printing density of the water-based ink. As the aromatic group-containing (meth) acrylate, benzyl (meth) acrylate and phenoxyethyl (meth) acrylate are preferable. preferable.
Among the components (d), styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable from the viewpoint of increasing the affinity of the polymer for the colorant.

[Macromer (e)]
The monomer mixture preferably further contains macromer (e) (hereinafter also referred to as “component (e)”).
The macromer (e) is a compound having a polymerizable functional group at one end and a number average molecular weight of 500 to 100,000, and is used from the viewpoint of increasing the affinity of the polymer for the colorant.
The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, more preferably a methacryloyloxy group, from the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink. The number average molecular weight is 500 to 100,000, preferably 1,000 to 10,000. The number average molecular weight is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent.
As the macromer (e), an aromatic group-containing macromer and a silicone-based macromer are preferable from the viewpoint of increasing the affinity of the polymer to the colorant, and an aromatic group-containing macromer is more preferable. Among the aromatic group-containing macromers, Styrenic macromers and aromatic group-containing (meth) acrylate macromers are preferred.
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. In the case of a copolymer, the content of the styrenic monomer is preferably 50% by weight or more, and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the colorant. Other monomers to be copolymerized include aromatic group-containing (meth) acrylates or acrylonitrile. Examples of the styrenic monomer include styrene and 2-methylstyrene.
Specific examples of the styrenic macromer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.), and the like.

Examples of the aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. In the case of a copolymer, the content of the aromatic group-containing (meth) acrylate is preferably 50% by weight or more and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the pigment mixture. The aromatic group-containing (meth) acrylate is a (meth) acrylate having an arylalkyl group having 7 to 12 carbon atoms or an aryl group, which may have a substituent containing a hetero atom, such as benzyl (meth). Examples include acrylate and phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate is preferred. Examples of other monomers to be copolymerized include styrene monomers and acrylonitrile.
The macromer may be a silicone macromer, and examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.
The macromer (e) in the water-insoluble polymer (y) is more preferably a styrenic macromer from the viewpoint of increasing the affinity with the water-soluble polymer (x) described later.

The content of the structural unit derived from the components (a) to (e) in the water-insoluble polymer (y) is as follows.
The content of the structural unit derived from the component (a) is preferably 4 to 40% by weight, more preferably 5 to 30% by weight, more preferably 7 to 30% by weight, from the viewpoint of enhancing the dispersibility of the polymer particles. More preferably, it is 7-25 weight%.
The content of the structural unit derived from the component (b) is preferably 2 to 30% by weight, more preferably 5 to 25% by weight, from the viewpoint of increasing the affinity of the polymer for the colorant.
The content of the structural unit derived from the component (c) is preferably 2 to 30% by weight, more preferably 5 to 25% by weight from the viewpoint of increasing the affinity of the polymer for the colorant.
The content of the structural unit derived from the component (d) is preferably 60% by weight or less, more preferably 10 to 50% by weight, from the viewpoint of increasing the affinity of the polymer for the colorant.
The content of the structural unit derived from the component (e) is preferably 25% by weight or less, more preferably 5 to 20% by weight, from the viewpoint of increasing the affinity of the polymer colorant.
Moreover, 50-200 are preferable and, as for the acid value in case (a) component is an anionic monomer, 50-160 are more preferable.
The total content of the structural units derived from the component (a), the component (b), and the component (c) is preferably from the viewpoint of increasing the dispersibility of the polymer particles and increasing the affinity of the polymer to the colorant. 20 to 80% by weight, more preferably 25 to 70% by weight, still more preferably 30 to 65% by weight.
The weight ratio (b / c) between the structural unit derived from the component (b) and the structural unit derived from the component (c) is an aqueous dispersion excellent in redispersibility and an aqueous system excellent in fixability to recording paper. From the viewpoint of obtaining ink, 0.3 to 3 is preferable, 0.5 to 2 is more preferable, 0.5 to 1.5 is more preferable, and 0.7 to 1.3 is still more preferable.
The weight average molecular weight of the water-insoluble polymer (y) is preferably 20,000 to 400,000, more preferably 30,000 to 300,000, more preferably 50,000 to 200,000, from the viewpoint of improving the storage stability of the aqueous dispersion and aqueous ink. Is more preferable. In addition, the weight average molecular weight of this polymer can be measured by the method as described in an Example.

(Water-soluble polymer (x))
In the present invention, from the viewpoint of atomizing the colorant, improving dispersibility, mainly reducing the viscosity of the ink, and suppressing the change in the light absorption characteristics of the colorant, the polymer particles constituting the polymer particles containing the colorant As a preferred embodiment, the water-insoluble polymer (x) is used in combination with the water-insoluble polymer (y). The water-soluble polymer (x) is preferably a vinyl polymer obtained by addition polymerization of a vinyl monomer or a urethane polymer having a urethane bond, and a salt-forming group-containing monomer (a) (same as the component (a) above) And a vinyl polymer obtained by copolymerizing a monomer mixture (same as the above “monomer mixture”) containing a hydrophobic monomer (e) (same as the component (d) above).

[Salt-forming group-containing monomer (a)]
Specific examples and preferred examples of the salt-forming group-containing monomer (a) in the water-soluble polymer (x) are the same as described above. Among them, a carboxylic acid monomer is preferable from the viewpoint of improving the dispersibility of the polymer particles, acrylic acid and methacrylic acid are more preferable, and acrylic acid is more preferable from the viewpoint of improving solubility in water.

[Hydrophobic monomer (d)]
Specific examples and preferred examples of the hydrophobic monomer (d) in the water-soluble polymer (x) are the same as described above. Among them, styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable from the viewpoint of increasing the affinity of the polymer for the pigment mixture.
Further, as described above, from the viewpoint of increasing the affinity with the water-insoluble polymer (y), the component (d) in the water-insoluble polymer (y) and the water-soluble polymer (x) is preferably the same.

The water-soluble polymer (x) is preferably 5 to 80% by weight, more preferably 10 to 60% by weight of the structural unit derived from the component (a) from the viewpoint of the storage stability of the aqueous dispersion and the aqueous ink. Preferably, it contains 15 to 40% by weight, and the constituent unit derived from the component (e) is preferably 15 to 95% by weight, more preferably 25 to 90% by weight, still more preferably 50 to 80% by weight, e) As the structural unit derived from the component, a structural unit derived from a styrene monomer is preferable, and the structural unit derived from the styrene monomer is preferably 50 to 90% by weight in all monomers of the water-soluble polymer (x). Preferably it contains 50 to 80% by weight.
The water-soluble polymer (x) has a weight average molecular weight of preferably 1000 to 300,000, more preferably 10,000 to 200,000, from the viewpoint of improving the dispersibility of the colorant. In addition, the weight average molecular weight of this polymer can be measured by the method as described in an Example.
The acid value when component (a) is an anionic monomer is preferably 150 to 300 KOHmg / g, more preferably 170 to 250 KOHmg / g.
Examples of commercially available water-soluble polymers (x) include BASF Japan's Jonkrill (registered trademark) 57J, 60J, 61J, 63J, 70J, PD-96J, and 501J. . These commercially available polymers are neutralized, and a neutralizing agent may be added separately as necessary.

[Production of polymer constituting polymer particles containing colorant]
The water-insoluble polymer (y) and the water-soluble polymer (x) (hereinafter collectively referred to as “polymer”) used in the present invention are bulk polymerization, solution polymerization, suspension polymerization, emulsification. It is produced by copolymerizing the monomer mixture by a known polymerization method such as a polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is preferably a polar organic solvent. When the polar organic solvent is miscible with water, it can be used by mixing with water. As the polar organic solvent, for example, aliphatic alcohols having 1 to 3 carbon atoms; ketones having 3 to 8 carbon atoms; esters such as ethyl acetate; or a mixed solvent of one or more of these with water.
In the polymerization, a known radical polymerization initiator such as an azo compound or an organic peroxide can be used. The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide may be further added.
Although the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, solvent, etc. used, it cannot be generally stated, but usually the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C. The polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the polymer produced by a known method can be isolated. Further, the obtained polymer can be purified by removing the unreacted monomer and the like by re-precipitation by membrane separation, chromatographic method, extraction method or the like.

The polymer used in the present invention is preferably used after neutralizing the salt-forming group derived from the salt-forming group-containing monomer (a) with a neutralizing agent. When the salt-forming group is an anionic group, examples of the neutralizing agent include bases such as sodium hydroxide, potassium hydroxide and various amines.
The degree of neutralization of the salt-forming groups of the polymer is preferably 10 to 300%, more preferably 20 to 200%, from the viewpoint of improving the dispersion stability of the polymer particles (A) in the ink. More preferably, ˜150%.
Here, the degree of neutralization (%) when the salt-forming group is an anionic group can be obtained by the following formula.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
The acid value can be calculated by calculation from the structural unit of the polymer, or can be determined by a method in which the polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

[Polymer particles containing colorant and crosslinked polymer particles containing colorant]
In the water-based dispersion and water-based ink of the present invention, a colorant is dispersed with a polymer. From the viewpoint of improving storage stability, “polymer particles containing a colorant” containing a colorant in a polymer are included. It contains crosslinked polymer particles obtained by crosslinking.
Polymer particles containing a colorant (hereinafter also simply referred to as “polymer particles (A)”) are prepared by dispersing the colorant with the water-insoluble polymer (y) alone or with the water-insoluble polymer (y) and the water-soluble polymer (x). It can be obtained by processing.
Crosslinking polymer particles containing the resulting colorant by using the water-insoluble polymer (y) alone or in combination with the water-soluble polymer (x) and the water-insoluble polymer (y) as a dispersant for the colorant. As a result, it is possible to obtain an aqueous dispersion for ink jet recording and an aqueous ink that have high printing density and excellent storage stability even when the solid content concentration is high. Further, when the water-insoluble polymer (y) and the water-soluble polymer (x) are used in combination, the viscosity of the ink can be further reduced, the change in the light absorption characteristics of the colorant (particularly the pigment) is suppressed, and the storage stability is improved. be able to. This is because the water-insoluble polymer (y) adheres to the surface of the colorant and the colorant can be finely dispersed, and the water-insoluble polymer particles containing the colorant are stabilized by the water-soluble polymer (x). This is probably because of this.

The weight ratio of the colorant to the water-insoluble polymer (y) [colorant / water-insoluble polymer (y)] is preferably 1-20, more preferably 1-10, from the viewpoint of achieving both print density and storage stability. 2-6 are more preferable.
The weight ratio of the colorant to the water-soluble polymer (x) [colorant / water-soluble polymer (x)] is preferably 10 to 25 from the viewpoint of reducing the viscosity of the water-based ink and suppressing the change in light absorption characteristics, and 14 to 23 Is more preferable, and 14 to 20 is still more preferable.
The weight ratio of the colorant to the total amount [(y) + (x)] of the water-insoluble polymer (y) and the water-soluble polymer (x) used for dispersion [colorant / [(y) + (x)]] In addition to the compatibility between the print density and storage stability, 50/50 to 95/5 is preferable, and 60/40 to 95/5 is more preferable, from the viewpoint of reducing the viscosity of the water-based ink and suppressing the change in light absorption characteristics. 70/30 to 95/5 is more preferable.
The weight ratio of the water-soluble polymer (x) to the water-insoluble polymer (y) [(x) / (y)] reduces the viscosity of the ink and changes the light absorption characteristics in addition to the compatibility between the print density and storage stability. From the viewpoint of suppressing, 0 to 0.5, preferably 0 to 0.4, and more preferably 0 to 0.3.
The polymer particles (A) can be produced as an aqueous dispersion by the method having the steps (1), (2), or the steps (I), (II) described in the method 1 or 2 for producing an aqueous dispersion described later. Efficient and preferred.

The aqueous dispersion and aqueous ink of the present invention contain a crosslinked polymer obtained by crosslinking the polymer (A). From the same viewpoint, the water-insoluble polymer (y) or the water-soluble polymer (x) and water are used. It is preferable that the insoluble polymer (y) includes a crosslinked polymer obtained by crosslinking treatment.
The crosslinking rate (mol%) of the crosslinked polymer is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%. The crosslinking rate is determined by the method described later. Can do.
The crosslinked polymer particles are efficiently and preferably produced as an aqueous dispersion by the method having the step (3) or the step (III) described in the method for producing an aqueous ink described later.

[Method 1 of producing aqueous dispersion for inkjet recording]
In the present invention, when a water-insoluble polymer (y) is used as the polymer, according to the method having the following steps (1) to (3), the water-insoluble polymer (y) includes a crosslinked polymer obtained by crosslinking treatment. An aqueous dispersion for inkjet recording containing crosslinked polymer particles can be produced efficiently.
Step (1): Water-insoluble polymer (y) particles containing a colorant by dispersing a mixture containing a water-insoluble polymer (y), an organic solvent, a colorant, water, and, if necessary, a neutralizer. Step (2): Step of removing the organic solvent from the dispersion obtained in step (1) to obtain an aqueous dispersion of water-insoluble polymer (y) particles containing a colorant (3): Step of obtaining a water-based dispersion of crosslinked polymer particles containing a colorant by crosslinking the polymer of the water-insoluble polymer (y) particles containing the colorant obtained in the step (2) with a crosslinking agent. The water-based ink for ink-jet recording of the invention can be obtained by adding additives such as a wetting agent usually used for water-based ink to the dispersion obtained in the steps (1) to (3) as necessary. .

Process (1)
In the step (1), first, the water-insoluble polymer (y) is dissolved in an organic solvent, and then a colorant, water, and, if necessary, a neutralizing agent, a surfactant and the like are added to the obtained organic solvent solution. In addition, a method of mixing to obtain an oil-in-water dispersion is preferred. Although there is no restriction | limiting in the order added to the organic solvent solution of a water-insoluble polymer (y), It is preferable to add in order of a neutralizing agent, water, and a coloring agent.
In the mixture, the colorant is preferably from 3 to 50% by weight, more preferably from 5 to 40% by weight, and the organic solvent is from 3 to 40% from the viewpoint of achieving both the storage stability of the aqueous dispersion and the aqueous ink and high printing density. 70 wt% is preferable, 5 to 50 wt% is more preferable, the water-insoluble polymer (y) is preferably 0.3 to 40 wt%, more preferably 0.5 to 20 wt%, and water is 10 to 85 wt%. % By weight is preferable, and 20 to 85% by weight is more preferable.
The weight ratio of the amount of the colorant to the amount of the water-insoluble polymer (y) [colorant / water-insoluble polymer (y)] is preferably as described above.

When the polymer has a salt-forming group, it is preferable to use a neutralizing agent. There is no particular limitation on the degree of neutralization when neutralizing with a neutralizer. Usually, the liquid dispersion of the finally obtained aqueous dispersion is preferably neutral, for example, pH is 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the polymer. Examples of the neutralizing agent include those described above. Further, the polymer may be neutralized in advance.
Examples of the organic solvent include alcohol solvents such as ethanol, isopropanol and isobutanol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. Preferably, the amount dissolved in 100 g of water is 20 g or more, preferably 5 g or more, more preferably 10 g or more, more specifically preferably 5 to 80 g, more preferably 10 to 50 g, and methyl ethyl ketone. And methyl isobutyl ketone is more preferred.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (1). The average particle size of the water-insoluble polymer (y) particles containing the colorant can be atomized until the desired particle size is obtained by this dispersion alone, but preferably after pre-dispersion, a shear stress is further applied. It is preferable to carry out this dispersion and control the average particle size of the water-insoluble polymer (y) particles containing the colorant to a desired particle size. The temperature in the system in the dispersion in the step (1) is preferably 0 to 40 ° C, more preferably 5 to 30 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 1 to 25 hours.
When pre-dispersing the mixture, commonly used mixing and stirring devices such as anchor blades and disper blades, such as Ultra Disper, Desperm (Asada Tekko Co., Ltd., trade name), Milder (Ebara Manufacturing Co., Ltd.) High-speed agitation and mixing devices such as TK Homomixer, TK Pipeline Mixer, TK Homojetter, TK Homomic Line Flow, and Fillmix (hereinafter, Primix Co., Ltd., trade name) are preferred.
Examples of means for applying the shear stress of this dispersion include, for example, a kneader such as a roll mill, a kneader, and an extruder, a high pressure homogenizer represented by a high pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), and a microfluidizer (Microfluidics). Company name, Nanomizer (Yoshida Kikai Kogyo Co., Ltd., trade name), chamber type high-pressure homogenizers such as Optimizer, Starburst (Sugino Machine Co., Ltd., trade name), paint shakers, bead mills, etc. Is mentioned. Commercially available media-type dispersers include Ultra Apex Mill (manufactured by Kotobuki Kogyo Co., Ltd., trade name), Picomill (manufactured by Asada Tekko Co., Ltd., trade name), Dino Mill (manufactured by Shinmaru Enterprises Co., Ltd., trade name), etc. Is mentioned.

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

Process (3)
In step (3), the water-insoluble polymer (y) particle-containing polymer containing the colorant obtained in step (2) is crosslinked with a crosslinking agent to obtain an aqueous dispersion of crosslinked polymer particles containing the colorant. It is a process. Step (3) is performed from the viewpoint of reducing the viscosity of the water-based ink and improving the print density.
Here, the crosslinking agent is preferably a compound having a functional group that reacts with the salt-forming group of the polymer from the viewpoint of achieving both the redispersibility and storage stability of the aqueous dispersion and aqueous ink to be obtained. A compound having 2 or more, preferably 2 to 6 in the molecule is more preferable.
From the viewpoint of efficiently crosslinking the surface of the polymer, the amount of the crosslinking agent when dissolved in 100 g of water at 25 ° C. is preferably 50 g or less, more preferably 40 g or less, and even more preferably 30 g or less. The molecular weight of the crosslinking agent is preferably 120 to 2000, more preferably 150 to 1500, and still more preferably 150 to 1000 from the viewpoint of reducing the viscosity of the water-based ink and increasing the printing density.

(Crosslinking agent)
Preferable examples of the crosslinking agent include the following (a) to (c).
(A) Compound having two or more epoxy groups in the molecule: for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether Polyglycidyl ethers such as trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether.
(B) Compounds having two or more oxazoline groups in the molecule: for example, bisoxazoline compounds such as 2,2′-bis (2-oxazoline), 1,3-phenylenebisoxazoline, 1,3-benzobisoxazoline, A compound having a terminal oxazoline group obtained by reacting the compound with a polybasic carboxylic acid.
(C) Compound having two or more isocyanate groups in the molecule: for example, organic polyisocyanate or isocyanate group-terminated prepolymer.
Among these, (a) a compound having two or more epoxy groups in the molecule is preferable, and ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are particularly preferable.

The amount of the crosslinking agent used is a weight ratio of the crosslinking agent used and the polymer constituting the polymer particle (A) from the viewpoint of reducing the viscosity of the polymer particles (A) in the ink [crosslinking agent / polymer. ] Is preferably 5/100 to 25/100, more preferably 7/100 to 25/100, more preferably 10/100 to 25/100, and still more preferably 16/100 to 20/100.
In addition, the amount of the crosslinking agent to be used is, as the number of moles of the reactive group of the crosslinking agent, from the viewpoint of achieving both the storage stability and the redispersibility of the aqueous dispersion and the aqueous ink with respect to 1 g of the polymer. It is preferably an amount that reacts with 05 to 10 mmol, more preferably 0.1 to 5 mmol, and even more preferably an amount that reacts with 0.1 to 2 mmol.
The conditions during the crosslinking reaction are preferably 60 to 95 ° C. and 0.5 to 7 hours.
The cross-linked polymer in the aqueous dispersion of cross-linked polymer particles obtained in the step (3) preferably contains 0.5 mmol or more of neutralized salt-forming groups (preferably carboxy groups) per 1 g of the cross-linked polymer. Such a crosslinked polymer is considered to contribute to the stability of the crosslinked polymer particles containing the colorant by dissociating in the aqueous dispersion and charge repulsion between the salt-forming groups.
Here, the crosslinking rate (mol%) of the crosslinked polymer obtained from the following calculation formula (3) is preferably 10 to 90 mol% from the viewpoint of achieving both storage stability and redispersibility of the aqueous dispersion and the aqueous ink. More preferably, it is 20-80 mol%, More preferably, it is 30-70 mol%. The crosslinking rate can be determined by calculation from the amount of the crosslinking agent used and the number of moles of the reactive group, the amount of polymer used and the number of moles of the reactive group of the polymer that can react with the reactive group of the crosslinking agent.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent / number of moles of reactive group capable of reacting with crosslinking agent of polymer] × 100 (3)
In the calculation formula (3), “the number of moles of the reactive group of the crosslinking agent” is obtained by multiplying the number of moles of the crosslinking agent to be used by the number of reactive groups in one molecule of the crosslinking agent.
The crosslinking of the polymer can also be performed by mixing a dispersion of polymer particles containing the colorant obtained in step (1) and a crosslinking agent. In this case, the aqueous dispersion of the crosslinked polymer particles containing the colorant is carried out in the same manner as in the step (2) by removing the organic solvent from the aqueous dispersion of the crosslinked polymer particles obtained in the crosslinking step. You can get a body.

[Method 2 for producing aqueous dispersion for inkjet recording]
In the present invention, when the water-soluble polymer (x) and the water-insoluble polymer (y) are used as the polymers, according to the method having the following steps (I) to (III), the aqueous dispersion for inkjet recording is efficiently used. Can be manufactured.
Step (I): A step of dispersing a colorant with a water-soluble polymer (x) and water to obtain an aqueous dispersion Step (II): A water-insoluble polymer (y) is added to the aqueous dispersion obtained in Step (I). Step of adding and further dispersing to obtain a dispersion containing polymer particles (A) containing a colorant Step (III): The dispersion obtained in step (II), or removing the solvent from the dispersion Step of performing crosslinking treatment on the obtained aqueous dispersion The aqueous ink for ink jet recording of the present invention is usually used in the dispersion obtained in the steps (I) to (III) as required. It can be obtained by adding an additive such as a wetting agent.

Process (I)
Step (I) is a step of dispersing the colorant with the water-soluble polymer (x) to obtain an aqueous dispersion. First, the water-soluble polymer (x), the colorant, water, and neutralization as necessary. A method of mixing an agent, a surfactant and the like to obtain a mixture and dispersing the mixture with a disperser is preferable.
In the mixture, the colorant is preferably from 3 to 50% by weight, more preferably from 5 to 40% by weight, and the organic solvent is from 3 to 40% from the viewpoint of achieving both the storage stability of the aqueous dispersion and the aqueous ink and high printing density. 70 wt% is preferable, 5 to 50 wt% is more preferable, the water-insoluble polymer (y) is preferably 0.3 to 40 wt%, more preferably 0.5 to 20 wt%, and water is 10 to 85 wt%. % By weight is preferable, and 20 to 85% by weight is more preferable.
The preferred weight ratio between the water-soluble polymer (x) and the colorant is as described above.
When neutralizing using a neutralizing agent, it is preferable to neutralize so that the finally obtained aqueous dispersion has a pH of 7-11. Examples of the neutralizing agent include bases such as sodium hydroxide, potassium hydroxide, and various amines. Further, the water-soluble polymer (x) may be neutralized in advance.
Examples of the organic solvent are the same as described above.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (I). The average particle size of the colorant particles can be atomized only by this dispersion until the desired particle size is obtained. From the viewpoint of improving the storage stability of the aqueous dispersion and aqueous ink, preferably after preliminary dispersion. Further, it is preferable to control the average particle size of the colorant particles so as to have a desired particle size by further applying a shear stress. 5-50 degreeC is preferable, as for the temperature in dispersion | distribution of process (I), 5-35 degreeC is more preferable, 1-30 hours is preferable and dispersion time is more preferable 1-25 hours.
When the mixture is predispersed, the high-speed stirring and mixing apparatus used in the production method 1 can be used.
As a means for giving the shear stress of this dispersion, the same means as used in the production method 1 can be mentioned.

Process (II)
Step (II) is a step of adding a water-insoluble polymer (y) to the aqueous dispersion obtained in step (I) and further dispersing to obtain a dispersion containing polymer particles (A) containing a colorant. Prepare and disperse a mixture containing the aqueous dispersion obtained in step (I), the water-insoluble polymer (y), an organic solvent, water, and, if necessary, a neutralizing agent and a surfactant. A method is preferred, and it is preferred to use a dispersion of a water-insoluble polymer (y) containing a water-insoluble polymer (y), an organic solvent and water.
In the mixture, the colorant is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, and the organic solvent is 3% from the viewpoint of achieving both the storage stability of the aqueous dispersion and the aqueous ink and high printing density. -70 wt% is preferable, 5-50 wt% is more preferable, the water-insoluble polymer (y) is preferably 0.3-40 wt%, more preferably 0.5-20 wt%, 85 weight% is preferable and 20 to 85 weight% is more preferable.
A preferred weight ratio between the water-insoluble polymer (y) and the colorant is as described above.
When neutralizing using a neutralizing agent, it is preferable to neutralize so that the finally obtained aqueous dispersion has a pH of 7-11. Further, the anionic polymer may be neutralized in advance.
Specific examples and preferred examples of the organic solvent are the same as the organic solvent used in Production Method 1.

The method for dispersing the mixture in the step (II) is not particularly limited as in the step (I), and the average particle size of the polymer particles can be atomized until the desired particle size is obtained only by this dispersion, After the preliminary dispersion, the main dispersion may be performed by applying a shear stress. The temperature in the system in the dispersion of the step (II) is preferably 5 to 50 ° C, more preferably 5 to 35 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 2 to 25 hours.
When preliminarily dispersing the mixture, the above-described mixing and stirring device or the like is preferably used.
Examples of means for imparting the shear stress of this dispersion include the kneader, the high-pressure homogenizer, and the media-type disperser. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle diameter of the polymer particles (A) and stabilizing the dispersion.

(Solvent removal step)
In the water-based ink production method, as an optional step, after step (II), the organic solvent is distilled off from the dispersion containing the polymer particles (A) obtained in step (II) by a known method. Thus, an aqueous dispersion of polymer particles (A) can be obtained. This step may be performed after step (II).
The organic solvent in the aqueous dispersion of the obtained polymer particles (A) is preferably substantially removed, but may remain as long as the purpose of the present invention is not impaired, and the crosslinking step is performed later. In such a case, it may be additionally removed after cross-linking if necessary. The amount of the residual organic solvent in the finally obtained polymer particle (A) aqueous dispersion is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
If necessary, the dispersion can be heated and stirred before the organic solvent is distilled off.
The obtained aqueous dispersion of polymer particles (A) is one in which the solid content of the polymer is dispersed in water as a main medium. Here, the form of the polymer particles (A) is not particularly limited as long as the particles are formed of at least a colorant and a polymer. For example, a particle form in which a colorant is included in the polymer, a particle form in which a colorant is uniformly dispersed in the polymer, a particle form in which a colorant is exposed on the polymer particle surface, and the like are included.

Process (III)
Step (III) is a step of subjecting the dispersion containing the polymer particles (A) obtained in step (II) or the aqueous dispersion obtained by removing the solvent from the dispersion to a crosslinking treatment. When the dispersion containing the polymer particles (A) obtained in the step (II) or the dispersion obtained in the step (II) contains a solvent, the dispersion is obtained by removing the solvent from the dispersion. By adding a crosslinking agent to the aqueous dispersion of polymer particles (A), an aqueous dispersion containing crosslinked polymer particles obtained by crosslinking the water-insoluble polymer (y) and the water-soluble polymer (x) can be obtained. Step (III) is performed from the viewpoint of reducing the viscosity of the water-based ink and improving the printing density.
When the polymer is crosslinked by mixing the dispersion of the polymer particles (A) containing the colorant obtained in the step (II) and the crosslinking agent, the crosslinking polymer particles obtained in the crosslinking step An aqueous dispersion can also be obtained by performing the step of removing the organic solvent from the dispersion in the same manner as the solvent removal step.
Here, specific examples and preferred examples of the crosslinking agent include the same ones as described above.
The amount of the crosslinking agent used, the amount of neutralized salt-forming groups (preferably carboxy groups) per gram of the crosslinked polymer, and the crosslinking rate (mol%) of the crosslinked polymer are the same as described above.

[Aqueous dispersion for inkjet recording]
The aqueous dispersion for inkjet recording of the present invention is obtained by the above production method, and may be used as it is as an aqueous ink using water as a main medium.
The content of each component in the aqueous dispersion of the present invention is as follows.
The content of the colorant is preferably 1 to 35% by weight, more preferably 7 to 30% by weight, and still more preferably 10 to 28% by weight, from the viewpoint of increasing the printing density of the water-based ink. The aqueous dispersion of the present invention has a special effect that it has excellent storage stability even if the content of the crosslinked polymer particles containing the colorant is high. In the aqueous dispersion of the present invention, the content of the crosslinked polymer particles containing a colorant is preferably 1 to 35% by weight, more preferably 7 to 7%, from the viewpoint of improving storage stability and from the viewpoint of blending the aqueous ink. 30% by weight, more preferably 10 to 28% by weight.
The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight.

[Water-based ink for inkjet recording]
The aqueous ink for inkjet recording of the present invention is characterized by containing the above-mentioned aqueous dispersion. Here, “water-based” means that water occupies the largest proportion in the medium contained in the water-based ink, and the medium may be only water, and water and one or more organic solvents. And a mixed solvent. To this water-based ink, wetting agents, penetrants, dispersants, viscosity modifiers, antifoaming agents, antifungal agents, rust preventive agents and the like that are usually used in water-based inks can be added.
The content of each component in the aqueous ink of the present invention is as follows.
The content of the colorant is preferably 1 to 30% by weight, more preferably 4 to 20% by weight, more preferably 4 to 15% by weight, and still more preferably 4 from the viewpoint of achieving both printing density and storage stability. ~ 12% by weight. The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.

Further, the average particle size as the water-based ink is preferably 30 nm to 300 nm, more preferably 50 nm to 200 nm, from the viewpoints of high-speed printer suitability and printing performance.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is particularly suitable for a piezo ink jet printer.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
In addition, the weight average molecular weight of the polymer obtained by the manufacture example, the Example, and the comparative example, the average particle diameter, various physical properties of the aqueous dispersion and the aqueous ink were measured and evaluated by the following methods.

(1) Measurement of polymer weight average molecular weight Gel chromatography method using a N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent [GPC apparatus manufactured by Tosoh Corporation ( HLC-8120GPC), a column manufactured by Tosoh Corporation (TSK-GEL, α-M × 2), flow rate: 1 mL / min], using polystyrene as a standard substance.
(2) Measurement of average particle diameter It measured using the laser particle analysis system "ELS-8000" (cumulant analysis) of Otsuka Electronics Co., Ltd. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and the number of integrations of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ wt%.

(3) Measurement of Viscosity of Aqueous Dispersion and Aqueous Ink Viscosity was measured at 20 ° C. using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80L).
(Evaluation criteria)
A: Ink viscosity is less than 11 mPa · s B: Ink viscosity is from 11 mPa · s to less than 13 mPa · s C: Ink viscosity is 13 mPa · s or more (Crosslinked) An aqueous dispersion of polymer particles and an aqueous ink were filled and sealed, and stored in a thermostat at 70 ° C. for 1 week. Viscosity before and after storage was measured according to the above (3), and was determined as a value of viscosity change rate (%) (the value closer to 100% is better storage stability) by the following formula, and evaluated according to the following criteria: .
Viscosity change rate (%) = 100-[[viscosity after storage] / [viscosity before storage]] × 100
(Evaluation criteria)
A: Viscosity change rate is within ± 10% B: Viscosity change rate exceeds ± 10%, within ± 15% C: Viscosity change rate exceeds ± 15% (5) Evaluation of redispersibility Glass One aqueous dispersion (20 μL) is dropped on a petri dish and dried in a thermostatic bath (drying conditions: 40 ° C., normal pressure, 12 h). After standing at room temperature for about 30 minutes, add 2 ml of the re-dispersibility test liquid (ink blending composition excluding the dispersion) to the dry ink on the glass plate, soak for 10.0 minutes, and shake with a shaker (shaking). And under the following criteria: 100 rpm, room temperature, 5.0 min).
(Evaluation criteria)
A: Aqueous dispersion fixed substance is redispersed B: Aqueous dispersion fixed substance is partially redispersed C: Aqueous dispersion fixed substance is not redispersed, but the redispersibility test liquid is dyed yellow D: Aqueous dispersion Fixed matter does not redisperse at all

(6) Evaluation of change in light absorption characteristics (3) Aqueous ink used for storage stability was diluted 10,000 times with water, and the absorption spectrum of the diluted solution was measured with a spectrophotometer (manufactured by Hitachi, Ltd., model number: U -3010) was measured over a range of absorption wavelengths from 370 to 800 nm. The amount of change with respect to the maximum absorption wavelength of the absorption spectrum before storage at 70 ° C. for one week was calculated and evaluated according to the following criteria.
(Evaluation criteria)
A: Change in maximum absorption wavelength is 1 nm or less B: Change in maximum absorption wavelength exceeds 1 nm to 3 nm or less C: Change in maximum absorption wavelength exceeds 3 nm

(7) Evaluation of ejection reliability Plain paper “4024” (Fuji Xerox Co., Ltd.) at 23 ° C. and 50% relative humidity using a commercially available Seiko Epson inkjet printer (product number: EM-930C, piezo method). 100) 2000 characters / sheet, and a test document including characters, solid images and ruled lines are printed, and (i) sharp and clear characters, (ii) uniform solid images, and (iii) ) Three items of ruled lines without twist were evaluated and evaluated according to the following criteria.
(Evaluation criteria)
A: All three items are satisfied (no problem)
B: All three items are almost satisfied (no problem in actual use)
C: Not satisfied with more than one item (problems in actual use)
(8) Measurement of Print Density Using the printer, print a solid image on the same plain paper “4024” as in (7) above, leave it for one day, and then use an optical densitometer SpectroEye (manufactured by Gretag Macbeth) Were measured and the average value was determined.
(9) Evaluation of Fixability Using the printer, a solid image having a size of 20 mm × 20 mm is printed on the same plain paper “4024” as in the above (7). With the back side of plain paper “P” (Fuji Xerox Co., Ltd.) overlaid, and with a load of 490 g (load area 43 mm × 30 mm) applied from above, the solid image surface is moved to measure the dirt on the overlaid paper did. Evaluation was performed according to the following criteria.
(Evaluation criteria)
A: The printed matter cannot be removed and the surroundings are not stained.
B: Almost no printed matter can be taken and the surroundings are not stained.
C: Almost no printed matter can be taken out and the surrounding area is slightly stained, but there is no practical problem.
D: The printed matter is rubbed off, the surroundings are very dirty, and the fingers are considerably dirty.

Production Examples 1 to 7 (Production of water-insoluble polymer)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.05 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of 200 parts of each monomer shown in Table 1 were mixed and mixed, and nitrogen gas substitution was performed sufficiently. A mixed solution was obtained.
On the other hand, the remaining 90% of the monomer shown in Table 1 was charged into the dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone, and a radical polymerization initiator (2,2′-azobis (2,4- Dimethylvaleronitrile)) 1.2 parts were added and mixed, and the gas was sufficiently replaced with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C. from the end of the dropwise addition, a solution in which 0.3 part of the radical polymerization initiator was dissolved in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours. A polymer solution (polymer solid content 40%) was obtained (Table 1). The solubility parameter (SP value) was calculated from the chemical structural formula of the homopolymer based on [“Basic Chemistry of Coating” by Yuji Harasaki, Tsuji Shoten, p. 54, (1986)].

Production Example 8 (Production of pigment mixture of PY74 and azo pigment derivative (A))
(1) 168 parts (1 mol) of 2-methoxy-4-nitroaniline was dissolved in a solution consisting of 2000 parts of water and 260 parts of 35% hydrochloric acid, and 1000 parts of ice was added thereto and cooled to 0 ° C. Water 20
A solution composed of 0 part and 70 parts of sodium nitrite was added and stirred at 3 ° C. or lower for 60 minutes to obtain a diazo component.
(2) On the other hand, 200 parts (0.966 mol) of 2-methoxyacetoacetanilide and 7.9 parts (0.019 mol) of a compound represented by the following formula (8) were added to 5000 parts of water and 10 parts of sodium hydroxide. Was dissolved in a solution consisting of To this, 200 parts of 80% acetic acid was added little by little to obtain a suspension, which was a coupler component.

(3) To the coupler component obtained in (2) above, the diazo component obtained in (1) above was added over 60 minutes. The coupling reaction during this period was kept at about 20 ° C. The obtained pigment mixture slurry was heated to 90 ° C. and held for 30 minutes, then filtered, washed with water, pressed, dried at 90 ° C. for 15 hours, and represented by 500 parts of Pigment Yellow 74, which is a monoazo pigment, and the following formula (9): A pigment mixture with the azo pigment derivative (A) was obtained. This pigment mixture was pulverized to obtain a pigment mixture powder.

Production Example 9 (Production of pigment mixture of PY74 and azo pigment derivative (B))
In a mixed solution of 960 g of water and 327 g (3.139 mol) of 35% hydrochloric acid, 162.6 g (1.07 mol) of 3-nitro-4-toluidine and a monoazo yellow organic pigment represented by the following formula (10) 17.01 g (0.03 mol) was added and dispersed by stirring. About 700 g of ice was added to this dispersion, and after cooling, a solution in which 87 g (1.27 mol) of sodium nitrite was dissolved in 130 g of water was added and stirred for 1 hour while maintaining at 10 ° C. or lower. After the nitrous acid had disappeared, filtration was performed to obtain a diazotized liquid.

  On the other hand, after dissolving 96 g (0.706 mol) of sodium acetate in 5300 g of water, 200.9 g (1.13 mol) of acetoacetylanilide was added and dispersed, and then 90 g of 80% acetic acid (1.199 mol). Was dropped to pH 6 and the temperature was adjusted to 25 ° C. to obtain a coupler solution. To this coupler liquid, the above diazotization liquid was dropped in 120 minutes to carry out a coupling reaction. Next, the temperature was raised to 90 ° C. and heat-treated for 30 minutes, followed by filtration and washing with water to remove by-product salts and the like, followed by drying at 80 ° C. with a dryer. The dried pigment was pulverized to give a yellow azo pigment derivative (B) represented by the following formula (11) and C.I. I. A pigment mixture with CI Pigment Yellow 74 was obtained.

Example 1
(1) Preparation of pigment dispersion Water-soluble polymer (John Krill 61J: manufactured by BASF Japan Ltd., weight average molecular weight 16000) 30.5% aqueous solution 41.9 parts, ion-exchanged water 1042.6 parts and methyl ethyl ketone 134.0 parts Was added to obtain an aqueous polymer solution.
13.2 parts of a 25% aqueous ammonia solution and 200.0 parts of the pigment mixture obtained in Pigment Production Example 8 as a yellow pigment were added to the resulting aqueous polymer solution, and mixed at 20 ° C. for 1 hour using a disper blade. A preliminary dispersion was obtained (step (I) preliminary dispersion).
Using 1432 parts of the resulting preliminary dispersion, Ultra Apex Mill: Model UAM-05 (Koto Kogyo Co., Ltd., Media Disperser, trade name), using zirconia beads having a particle size of 0.05 mm as media particles 1 hour under the conditions of a bead filling rate of 85% by volume, a stirring blade peripheral speed of 8 m / s, and a circulation flow rate of 200 cc / min (total average residence time in the mill: 7.5 minutes) A pigment dispersion was obtained (step (I) (a)).
(2) Preparation of water-insoluble polymer emulsion To 110.1 parts of the polymer solution obtained in Production Example 1, 15.3 parts of 5N sodium hydroxide aqueous solution, 11.4 parts of methyl ethyl ketone and 149.5 parts of ion-exchanged water were added. To prepare a polymer emulsion (step (I) (b)).
Next, the prepared polymer emulsion was added while mixing the pigment dispersion obtained in the above (1) with a stirrer to obtain a mixture (step (I) (c)).
(3) Dispersion treatment of pigment dispersion / water-insoluble polymer emulsion mixture The mixture obtained in (2) above was subjected to 15 passes at a pressure of 150 MPa using a microfluidizer (Microfluidics, high-pressure homogenizer, trade name). A dispersion was obtained by a continuous method to obtain a dispersion (step (II)).
(4) Removal of organic solvent The dispersion obtained in (3) above was subjected to removal of methyl ethyl ketone using a hot water heating medium under reduced pressure (step (III)), and a part of water was further removed to remove 5 μm. Solid content concentration 32 by filtering with a 25 mL needleless syringe (made by Terumo Corporation) attached with a filter (acetylcellulose membrane, outer diameter: 2.5 cm, made by Fuji Film Co., Ltd.) and removing coarse particles. % Aqueous dispersion was obtained.
(5) Preparation of aqueous dispersion of crosslinked polymer particles containing pigment mixture (step IV)
To 100 parts of the aqueous dispersion obtained in (4) above, a crosslinking agent (trimethylolpropane polyglycidyl ether, trade name: Denacol EX321L, epoxy equivalent 129, 100 parts by weight of water so that the crosslinking rate is 54 mol%) About 27 parts (25 ° C. dissolved), manufactured by Nagase ChemteX Corporation) (1.32 parts) and water (37.5 parts) were added, and the mixture was stirred at 90 ° C. for 1.5 hours in a sealed state. After stirring, the mixture is cooled, filtered using a 5.0 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Co., Ltd.), and a crosslinked polymer containing a pigment mixture having a solid content concentration of 24% An aqueous dispersion 1 of particles was obtained.
(6) Production of water-based ink 55.7 parts of an aqueous dispersion of crosslinked polymer particles containing the pigment mixture obtained above, 10.0 parts of glycerin, 2- {2- (2-butoxyethoxy) ethoxy} ethanol 5 1.0 part, 2.0 parts of 1,2-hexanediol, 0.5 part of acetylene glycol EO adduct (n = 10) and 26.8 parts of ion-exchanged water were mixed, and the resulting liquid mixture was 1.2 μm. A water-based ink 1 was obtained by filtering with a membrane filter (trade name: Minisart, manufactured by Sartorius).
The ink composition is shown in Table 2, and the results are shown in Table 3.

Example 2
In Example 1, the crosslinking agent containing the pigment mixture was used in the same manner as in Example 1 except that the crosslinking agent in Step IV was changed to 0.49 parts (crosslinking rate: 20 mol%) and water was changed to 34.9 parts. An aqueous dispersion 2 of polymer particles and an aqueous ink 2 were obtained.
Example 3
In Example 1, except that the water-soluble polymer in Step I was changed to 31.9 parts of water-insoluble polymer and 1052.6 parts of ion-exchanged water, the crosslinked polymer particles containing the pigment mixture were changed in the same manner as in Example 1. An aqueous dispersion was obtained. Further, in Example 1, the crosslinking agent containing the pigment mixture was changed in the same manner as in Example 1 except that the crosslinking agent in Step IV was changed to 1.20 parts (crosslinking rate: 20 mol%) and water was changed to 37.1 parts. An aqueous dispersion 3 of polymer particles and an aqueous ink 3 were obtained.
Examples 4-6
Aqueous dispersion of crosslinked polymer particles containing a pigment mixture in Example 1 except that the water-insoluble polymer in Step I (b) (Production Example 1) was changed to Production Examples 2 to 4, respectively. Body 4-6 and aqueous inks 4-6 were obtained.
Example 7
A crosslinked polymer containing the pigment mixture in the same manner as in Example 1 except that the pigment mixture in Example 1 was replaced with the pigment mixture obtained in Production Example 9 instead of the pigment mixture obtained in Production Example 8. An aqueous dispersion 7 of particles and an aqueous ink 7 were obtained.

Comparative Examples 1-3
Aqueous dispersion of crosslinked polymer particles containing a pigment mixture in the same manner as in Example 1 except that the water-insoluble polymer (Production Example 1) in Step I (b) was changed to Production Examples 5 to 7 in Example 1. Body 8-10 and aqueous ink 8-10 were obtained.
Comparative Example 4
In Example 1, the pigment mixture is contained in the same manner as in Production Example 1 except that the crosslinking agent in Step IV is changed to 0.0 part (crosslinking rate is 0 mol%) and ion-exchanged water is 33.3 parts. An aqueous dispersion 11 of crosslinked polymer particles and an aqueous ink 11 were obtained.
Comparative Example 5
In Example 7, the pigment mixture is contained in the same manner as in Example 7 except that the crosslinking agent in Step IV is changed to 0.0 part (crosslinking rate is 0 mol%) and ion-exchanged water is 33.3 parts. An aqueous dispersion 12 of polymer particles and an aqueous ink 12 were obtained.

  From Table 3, the aqueous dispersions of Examples 1 to 6 are excellent in storage stability and redispersibility, and the aqueous inks of Examples 1 to 6 have low ink viscosity, little change in light absorption characteristics, and storage stability. It can be seen that the ink has excellent properties, ejection reliability, print density, and fixability to recording paper. On the other hand, it can be seen that the water-based dispersions and water-based inks of Comparative Examples 1 to 4 are significantly inferior in the above characteristics as compared with the water-based dispersions and water-based inks of Examples 1 to 6.

Claims (6)

An aqueous dispersion of crosslinked polymer particles obtained by crosslinking polymer particles containing a colorant with a crosslinking agent, wherein the polymer constituting the polymer particles containing the colorant is derived from the salt-forming group-containing monomer (a). One or more selected from structural units, structural units derived from polypropylene glycol mono (meth) acrylate (b) represented by the following formula (1), and monomers represented by the following formulas (2) to (4) A nonionic monomer (c) -derived structural unit, and a polymer (A) having a solubility parameter (SP value) difference of 0.5 to 2.0 between the monomers (b) and (c). Aqueous dispersion for recording.

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and m represents a number of 2 to 20.)

(In the formula, R ¹ is the same as above, R ² represents a hydrogen atom, a phenyl group having a C 1-20 alkyl group or a C 1-9 alkyl group, and n is 2-30. Indicates the number.)

(In the formula, R ¹ is the same as defined above, R ³ represents a phenyl group having an alkyl group or an alkyl group having 1 to 9 carbon atoms having 1 to 20 carbon atoms, p is the number of 2 to 30. )

(In the formula, R ¹ and R ² are the same as described above, and q and r each represent a number of 1 to 30. The oxyethylene group and the oxypropylene group are block-added or randomly added.)   The aqueous dispersion for inkjet recording according to claim 1, wherein the polymer (A) comprises a water-insoluble polymer (y).   The aqueous dispersion for inkjet recording according to claim 2, wherein the water-insoluble polymer (y) contains a structural unit derived from the aromatic group-containing macromer (e).   The inkjet recording according to any one of claims 1 to 3, wherein the amount of the crosslinking agent used is 5/100 to 25/100 in a weight ratio of [polymer constituting the polymer particles containing the crosslinking agent / coloring agent]. Aqueous dispersion.   The colorant is C.I. I. The aqueous dispersion for ink-jet recording according to any one of claims 1 to 4, which is an azo pigment containing CI Pigment Yellow 74.   A water-based ink for ink-jet recording comprising the water-based dispersion according to any one of claims 1 to 5.