JP6984813B2 - Water-based ink for inkjet recording - Google Patents

Description

The present invention relates to a water-based ink for inkjet recording.

The inkjet recording method is a recording method in which ink droplets are directly ejected from a very fine nozzle onto a recording medium and adhered to obtain characters or images. This method has many advantages such as easy full-color printing, low cost, plain paper as a recording medium, and non-contact with the object to be printed, so it is suitable for consumer printing for general consumers. In recent years, it has begun to be applied to the fields of commercial printing and industrial printing.

However, in the inkjet recording method, due to the structure in which the ink passes through a fine ejection nozzle, for example, if even a very small amount of impurities are present in the pigment, problems such as blockage of the ejection nozzle are likely to occur. As a method for removing this trace amount of impurities, a method such as a centrifugation method, a filtration method, or an ion exchange method is known. Various raw materials used for producing water-based ink for inkjet recording are generally purified and used by a known method before mixing them.
For example, a crystallization method is known as a method for removing impurities contained in dyes and pigments.

Patent Document 1 describes a high-quality water-soluble phthalocyanine compound, substituted phthalocyanine, substituted 1,3-, for the purpose of reducing the content of an inorganic compound as an impurity without using an ion exchange treatment device or the like. Disclosed is a method for producing a water-soluble phthalocyanine compound, in which one or more compounds selected from diiminoisoindoline and the like are reacted with a specific metal derivative, and a hydrophilic organic solvent is allowed to act on the reaction mixture to crystallize the reaction mixture. There is.
Patent Document 2 describes a pigment, a dispersant having an acid value higher than that of an amine value, a polymerizable compound, and light, for the purpose of obtaining an ultraviolet curable inkjet ink that can be ejected stably and with high landing accuracy and has excellent storage stability. Disclosed is an ultraviolet curable inkjet ink containing a polymerization initiator, in which cationic impurities, metal impurities and the like are individually removed by a method such as crystallization, and the total amount of impurities is 500 ppm or less.
Patent Document 3 describes 0. Disclosed is an inkjet recording solution containing a reversibly adsorbed solution of 02 g / g or more and in which a nonionic surfactant and an anionic surfactant coexist.

Japanese Unexamined Patent Publication No. 2005-75778 Japanese Unexamined Patent Publication No. 2005-200560 Japanese Unexamined Patent Publication No. 2004-27204

The above-mentioned Patent Documents 1 and 2 purify raw materials individually, and a simple method capable of removing impurities in one step at the time of producing a water-based ink is not known.
Further, in Patent Document 3, after removing organic impurities by crystallization or the like prior to the use of a dye, the ink is mixed with a pigment, water or the like and subjected to ultrasonic dispersion treatment to obtain a water-based ink. Since the treatment is performed, an adverse effect on the performance of the water-based ink is unavoidable.
An object of the present invention is to provide a water-based ink for inkjet recording having excellent ejection properties and a method for producing the water-based ink.

In the water-based ink for inkjet recording, the present inventors measured the liquid medium portion of the ink with a high performance liquid chromatograph equipped with an ultraviolet / visible detector having an absorption wavelength of 400 nm. I. Pigment Yellow 74 with respect to the peak area (A ₇₄ ) of C.I. I. It was found that when the ratio of the total area of peaks ( _AE74 ) other than Pigment Yellow 74 was 1.4 or less, there was little nozzle chipping in the inkjet recorded material.
That is, the present invention provides the following [1].
[1] C.I. I. Pigment Yellow 74, a polymer dispersant, an organic solvent, and water are dispersed and treated. I. A water-based ink for inkjet recording containing Pigment Yellow 74.
C.I. measured by the method using the liquid chromatograph below. I. Pigment Yellow 74 with respect to the peak area (A ₇₄ ) of C.I. I. A water-based ink for inkjet recording, wherein the ratio (A _E74 / A _{74 ) of the total area (A E74} ) of peaks other than Pigment Yellow 74 is 1.4 or less.
(Measurement method by liquid chromatograph)
Add ion-exchanged water to 4 g of water-based ink to make 200 g, add 2 g of an acetonitrile 2 mol addition of 2,7-dimethyl-4-octin-4,5-diol, stir for 24 hours, and then collect 2 g of it. And centrifuge, add 1.3 g of diethyl ether to recover the diethyl ether phase, volatilize the diethyl ether, add 1.0 g of acetonitrile to prepare a sample, and perform high performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, using an ODS column, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: Measure under the condition of 400 nm.

According to the present invention, it is possible to provide a water-based ink for inkjet recording having excellent ejection properties and a method for producing the water-based ink.

It is a figure which shows the measurement result by the liquid chromatograph of Example 1. It is a figure which shows the measurement result by the liquid chromatograph of Example 2. It is a figure which shows the measurement result by the liquid chromatograph of the comparative example 3. It is a figure which shows the measurement result by the liquid chromatograph of the comparative example 1. FIG. It is a figure which shows the measurement result by the liquid chromatograph of the comparative example 2.

[Aqueous ink for inkjet recording]
The water-based ink for inkjet recording of the present invention is C.I. I. An inkjet recording water-based ink containing Pigment Yellow 74 (hereinafter, also referred to as “PY74” or simply “pigment”), with respect to the peak area (A ₇₄ ) of PY74 measured by the method using the liquid chromatograph below. A water-based ink for inkjet recording in which the ratio (A _E74 / A ₇₄ ) of the total area (A _{E74) of peaks other than PY74 is 1.4 or less.}
(Measurement method by liquid chromatograph)
Add ion-exchanged water to 4 g of water-based ink to make 200 g, add 2 g of an acetonitrile 2 mol addition of 2,7-dimethyl-4-octin-4,5-diol, stir for 24 hours, and then collect 2 g of it. And centrifuge, add 1.3 g of diethyl ether to recover the diethyl ether phase, volatilize the diethyl ether, add 1.0 g of acetonitrile to prepare a sample, and perform high performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, using an ODS column, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: Measure under the condition of 400 nm.

<Measurement by liquid chromatograph>
In the present invention, the measuring method by the liquid chromatograph is as described above.
PY74 absorbs ultraviolet light and visible light in the range of 350 nm to 500 nm to make human vision recognize yellow. Here, the ultraviolet / visible detector is a device that irradiates a sample with ultraviolet rays, visible rays, or near infrared rays and measures the absorbance thereof to clarify the presence of a substance, and uses an ultraviolet / visible light detector. When analyzing PY74, the wavelength of the detector is set to 400 nm.
Analysis by high performance liquid chromatograph reveals ghost peaks derived from electrical noise, dissolved gas in the sample, etc., but these ghost peaks are identified by a known method and are not included in peaks other than the peak corresponding to PY74. .. Under the measurement conditions according to the present invention, when the time for injecting the sample is 0 minutes, the ghost peak is detected in the vicinity of the holding time of 2.5 minutes. Therefore, in the measurement method using the liquid chromatograph according to the present invention, the time when the sample is injected is set to 0 minutes, and the peak detected from the retention time of 2.7 minutes to 10.0 minutes is targeted. The peak of PY74 is detected around 7.4 minutes.
Since the peak detected by the measuring method according to the present invention has absorption in the vicinity of 400 nm, it is presumed that it has a chemical structure similar to that of PY74, but it is difficult to identify the structure.

In the measuring method according to the present invention, from the viewpoint of transferring organic impurities existing in the water-based ink to the organic solvent phase and suppressing the mass change in the measuring process, the measurement method is carried out in a state of containing a poorly water-soluble organic solvent. As the poorly water-soluble organic solvent, a 2 mol adduct of ethylene oxide of 2,7-dimethyl-4-octyne-4,5-diol is used.
When the above-mentioned poorly water-soluble organic solvent is used, the polymer dispersant or the surfactant may be preferentially transferred to the poorly water-soluble organic solvent, which may adversely affect the measurement. To prevent this, 4 g of the water-based ink is diluted with water to 200 g before adding the poorly water-soluble organic solvent.
Further, before the start of measurement, the solid portion made of PY74, a polymer dispersant or the like and the liquid portion are separated by centrifugation. The intensity of centrifugation is preferably 10,000 G hours or more, preferably 100,000 G hours or more, and 1 million G hours or less, preferably 500,000 G hours or less, from the viewpoint of efficient measurement. ..
Further, from the viewpoint of suppressing the decomposition of the analysis target and improving the accuracy, the measurement is carried out after adding a water-insoluble and volatile organic solvent and then volatilizing the organic solvent under normal temperature and pressure.
Diethyl ether is used as the poorly water-soluble and volatile organic compound.

According to the present invention, it is possible to provide a water-based ink for inkjet recording having excellent ejection properties. The reason is not always clear, but it can be considered as follows.
In the commercially available PY74 used for the water-based ink for inkjet recording, various organic compounds produced as by-products during the production thereof are generally mixed as impurities. Examples of the by-produced organic compound include a diazo compound produced as a by-product during the diazo coupling reaction during the production of PY74, a compound undergoing a nucleophilic reaction with the diazo compound, and the like. More specifically, in a method of diazotizing 4-nitro-o-anisidine to cause a coupling reaction with acetacetic acid-o-anisidine, 2-[(2-methoxy-4-nitrophenyl) azo] -N- ( 2-Methoxyphenyl) Organic compounds such as ethaneamide are by-produced as impurities. Examples of other impurities include pigment derivatives added when preparing PY74. If the water-based ink contains a large amount of impurities caused by the production of such a pigment, it is considered that the impurities cause various problems such as ejection defects during inkjet recording. By using the index of the amount of impurities due to the peak detected by the measurement method using the liquid chromatograph according to the present invention, it is possible to obtain an inkjet water-based ink having excellent ejection properties.

Here, impurities (organic compounds) other than PY74 are separated and removed by high-pressure dispersion treatment or the like in the presence of an organic solvent, and the amount of the organic compound other than PY74, which is an impurity, is a specific ratio when the amount of PY74 is used as a reference. When the following, it is considered that the water-based ink has excellent ejection properties. More specifically, the ratio (A _E74 / A ₇₄ ) of the total area of peaks other than PY74 (A _{E74 ) to the peak area (A 74} ) of PY 74 measured by the method using a liquid chromatograph is 1.4 or less. At this time, it is considered that the water-based ink has excellent ejection properties.
The ratio of the peak area _(A E74 _/ A ₇₄₎ is to solve the defect of internal clogging of inkjet ejection nozzles, from the viewpoint of improving the discharge property, preferably 1.3 or less, more preferably 1.2 or less, It is more preferably 1.1 or less, and is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.4 or more, from the viewpoint of maintaining vivid color and suppressing blemishes. Even more preferably, it is 0.6 or more.
As a means for reducing the peak area ratio (A _E74 / A ₇₄ ), a method of selecting a lot of PY74 having a small amount of impurities other than PY74, and a method of separating and removing impurities other than PY74 by high-pressure dispersion treatment in the presence of an organic solvent. And so on.

<C. I. Pigment Yellow 74>
PY74 used in the present invention is a kind of monoazo pigment and is a name listed in the color index. Similarly, CI11741 is assigned to the color index number set by the color index.
PY74 is a compound represented by the following formula (I).

In formula (I), the wavy line indicates that the geometric isomers of the adjacent double bonds are one or more selected from the E-form and the Z-form. The compound represented by the formula (I) is preferably 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) -3-oxobutaneamide.

(Manufacturing method of PY74)
Examples of the method for producing PY74 include a production method (A) in which 4-nitro-o-anisidine is diazotized and coupled with acetoacetic acid-o-anisidide.
Impurities such as 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) ethaneamide are by-produced in this coupling reaction.
The production method (A) preferably has the following steps (1) to (3).
Step (1): Obtaining product A by diazotization reaction of 4-nitro-o-anisidine Step (2): Acetate acetate-o-anisidide, sodium hydroxide and water are mixed, and then acetic acid is added. Then, sodium acetate is further added to obtain the product B. Step (3): The product A obtained in the above step (1) and the product B obtained in the step (2) are mixed. The process of performing the coupling reaction

The diazotization reaction in the step (1) can be carried out, for example, by reacting 4-nitro-o-anisidine with nitrite or a salt thereof under acidic conditions.
In the step (2), the amount of by-products can be adjusted to some extent by adjusting the amounts of acetic acid and sodium acetate used, but it is difficult to sufficiently reduce the amount of by-products.
The step (3) is a step of mixing the product A obtained in the step (1) and the product B obtained in the step (2) and performing a coupling reaction, but the step (2) is preferable. The product A obtained in step (1) is added to the product B obtained in step (1).
The temperature of the coupling reaction is preferably 0 ° C. or higher, preferably 25 ° C. or lower, more preferably 20 ° C. or lower, still more preferably 15 ° C. or lower, still more preferably 10 ° C. or lower.
After the coupling reaction in the step (3), post-treatment such as adjusting the crystal, particle shape, particle diameter, etc. of the product to a desired range can be performed, if necessary.

In the present invention, PY74 is preferably dispersed in an aqueous medium using a polymer dispersant from the viewpoint of improving storage stability and blendability in ink. Here, examples of the polymer dispersant include a water-soluble polymer or a water-insoluble polymer, and PY74 is in the form of (i) PY74 dispersed with a water-soluble polymer, (ii) water-insoluble polymer particles containing PY74, and the like. Used. Among these, from the viewpoint of scratch resistance, it is preferable to use (ii) in the form of water-insoluble polymer particles containing PY74 (hereinafter, also referred to as “pigment-containing polymer particles”).
The "water-based medium" means a medium in which water accounts for the largest proportion of the medium in which the pigment is dispersed.

(I) PY74 dispersed with a water-soluble polymer
The PY74 dispersed with a water-soluble polymer is an aqueous dispersion in which PY74 is dispersed with a water-soluble polymer such as a copolymer having a carboxyl group containing acrylic acid or methacrylic acid. Examples of commercially available water-soluble polymers used include JONCRYL67, JONCRYL678, JONCRYL683, JONCRYL60J (all manufactured by BASF Japan Ltd.) and the like.
The PY74 dispersed with the water-soluble polymer is a water system containing PY74 dispersed by adding PY74 to an aqueous medium in which the water-soluble polymer is dissolved and applying shear stress with, for example, a kneader, a high-pressure homogenizer, a media-type disperser, or the like. It is preferably used as a dispersion.

(Ii) Water-insoluble polymer particles containing PY74 The form of the water-insoluble polymer particles (pigment-containing polymer particles) containing PY74 is not particularly limited, and the particles may be formed by at least PY74 and the water-insoluble polymer. For example, a particle form in which PY74 is encapsulated in the water-insoluble polymer, a particle form in which PY74 is uniformly dispersed in the water-insoluble polymer, a particle form in which PY74 is exposed on the surface of the water-insoluble polymer particles, and these. Also included is the form of the mixture.

(Water-insoluble polymer: polymer dispersant)
The water-insoluble polymer constituting the pigment-containing polymer particles preferably has a function as a dispersant for dispersing PY74 in an aqueous medium and maintaining stable dispersion, and a function as a fixing agent for a recording medium.
By "water insoluble" in this water insoluble polymer is meant that the aqueous dispersion of the water insoluble polymer is not transparent. Even if the water dispersion of the water-insoluble polymer looks transparent visually, it is judged to be water-insoluble if the Tyndall phenomenon is observed by observation with laser light or normal light. In addition, when the polymer is ionic, the judgment of "water insoluble" is that the anionic group of the polymer is 100% neutralized with sodium hydroxide in the case of an anionic polymer, and the cation of the polymer in the case of a cationic polymer. The sex group is 100% neutralized with hydrochloric acid.
The water-insoluble polymer used in the present invention is preferably a polymer having a salt-forming group (anionic group or cationic group) in the polymer chain from the viewpoint of improving dispersibility. Examples of the salt-forming group include anionic groups such as a carboxy group, a sulfonic acid group and a phosphoric acid group, and cationic groups such as an amino group and an ammonium group.
The polymer dispersant, which is a water-insoluble polymer, preferably has a salt-forming group, and at least one part of the salt-forming group is neutralized with a basic compound.

Examples of the water-insoluble polymer include polyester, polyurethane, vinyl-based polymer and the like. Further, a commercially available dispersion of water-insoluble polymer particles can also be used.
As the commercially available dispersion of water-insoluble polymer particles, a dispersion of particles composed of an acrylic resin, a urethane resin, a styrene-butadiene resin, a styrene-acrylic resin, or a vinyl chloride resin is preferable. Specific examples thereof include Neocryl A1127 (manufactured by DSM NeoResins, anionic self-crosslinked water-based acrylic resin), acrylic resin such as JONCRYL390 (manufactured by BASF Japan Co., Ltd.), WBR-2018, WBR-2000U (manufactured by Taisei Fine Chemical Co., Ltd.). Urethane resin such as SR-100, SR-102 (above, manufactured by Nippon A & L Co., Ltd.), styrene-butadiene resin such as JONCRYL7100, JONCRYL734, JONCRYL538 (above, manufactured by BASF Japan Co., Ltd.), and Examples thereof include vinyl chloride-based resins such as Vinibran 701 (manufactured by Nissin Chemical Industry Co., Ltd.).
The water-insoluble polymer is preferably a water-insoluble vinyl polymer obtained by addition polymerization of one or more vinyl monomers selected from a vinyl compound, a vinylidene compound, and a vinylene compound from the viewpoint of improving the storage stability of the ink.

The water-insoluble vinyl polymer includes (a) a structural unit derived from an ionic monomer (hereinafter, also referred to as “(a) component”) and (b) a constituent unit derived from (b) a macromonomer (hereinafter, also referred to as “(b) component”). A vinyl-based polymer containing a unit is preferable, and a structural unit derived from (c) a hydrophobic monomer (hereinafter, also referred to as “(c) component”) and (d) a nonionic monomer (hereinafter, also referred to as “(d) component”) are preferable. ) Is preferably contained at least one selected from the constituent units derived from).
The water-insoluble polymer is obtained by, for example, addition polymerization of (a) an ionic monomer, (b) a macromonomer, and if necessary, (c) a hydrophobic monomer and (d) a nonionic monomer by a known method. be able to.

<(A) Ionic monomer>
(A) The ionic monomer can be used as a monomer component from the viewpoint of improving the storage stability of the water-based ink.
Examples of the (a) ionic monomer include an anionic monomer and a cationic monomer, but an anionic monomer is preferable from the viewpoint of storage stability and ejection property of the water-based ink. Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, a phosphoric acid monomer and the like, and a carboxylic acid monomer having a carboxy group is preferable.
Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2-methacryloyloxymethylsuccinic acid and the like, and one selected from acrylic acid and methacrylic acid. The above is more preferable, and methacrylic acid is further preferable.

<(B) Macromonomer>
(B) The macromonomer is a compound having a polymerizable functional group at one end and having a number average molecular weight of 500 or more and 100,000 or less, and is preferably used from the viewpoint of improving the storage stability of the water-based ink. As the polymerizable functional group present at one end, an acryloyloxy group or a methacryloyloxy group is preferable, and a methacryloyloxy group is more preferable.
(B) The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured by a gel permeation chromatography method using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent, using polystyrene as a standard substance.
As the macromonomer, the aromatic group-containing monomer-based macromonomer and the silicone-based macromonomer are preferable, and the aromatic group-containing monomer-based macromonomer is more preferable, from the viewpoint of improving the storage stability of the water-based ink.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomer described in (c) Hydrophobic Monomer described later, preferably styrene and benzyl (meth) acrylate, and styrene. Is more preferable.
Specific examples of the styrene-based macromonomer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of the silicone-based macromonomer include organopolysiloxane having a polymerizable functional group at one end.

<(C) Hydrophobic monomer>
For the water-insoluble polymer, it is preferable to use (c) a hydrophobic monomer as a monomer component from the viewpoint of improving the storage stability of the water-based ink. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
The alkyl (meth) acrylic acid ester preferably has an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms, and is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, or propyl (meth). Acrylate, butyl (meth) acrylate, amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) Acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, isoamyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, isododecyl (meth) acrylate, isostearyl (meth) ) Acrylate and the like can be mentioned.
In addition, "(meth) acrylate" means one or more kinds selected from acrylate and methacrylate. "(Meta)" in the following is also synonymous.

As the aromatic group-containing monomer, a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a heteroatom, is preferable, and a styrene-based monomer and an aromatic group-containing (meth) acrylate are preferable. Is more preferable.
As the styrene-based monomer, styrene, 2-methylstyrene, vinyltoluene, and divinylbenzene are preferable, and styrene and 2-methylstyrene are more preferable.
Further, as the aromatic group-containing (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like are preferable, and benzyl (meth) acrylate is more preferable.
(C) As the hydrophobic monomer, two or more of the above-mentioned monomers may be used, or a styrene-based monomer and an aromatic group-containing (meth) acrylic acid ester may be used in combination.

<(D) Nonionic monomer>
For the water-insoluble polymer, it is preferable to use (d) a nonionic monomer (component (d)) as a monomer component from the viewpoint of improving the storage stability of the water-based ink.
As the component (d), 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polypropylene glycol (n = 2 to 30, n indicates the average number of moles of oxyalkylene group added; the same applies hereinafter). Polyalkylene glycol (meth) acrylates such as (meth) acrylate, polyethylene glycol (n = 2-30) (meth) acrylate, methoxypolyethylene glycol (n = 1-30) (meth) acrylate, polyethylene glycol methacrylate 2-ethylhexyl ether. Examples thereof include alkoxypolyalkylene glycol (meth) acrylates such as, phenoxy (ethylene glycol / propylene glycol copolymerization) (n = 1 to 30, ethylene glycol: n = 1 to 29) (meth) acrylates and the like. Among these, polypropylene glycol (n = 2 to 30) (meth) acrylate and polyethylene glycol (n = 2 to 6) methacrylate 2-ethylhexyl ether are more preferable.

Specific examples of the commercially available component (d) include NK ester M-20G, 40G, 90G, 230G, EH-4E, etc. (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), Blemmer PE-90. , 200, 350, etc., PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50PEP-300, 50POEP-800B, 43PAPE -600B etc. (manufactured by NOF CORPORATION) can be mentioned. Among these, NK ester EH-4E (polyethylene glycol [n = 4] methacrylate 2-ethylhexyl ether) is preferable, especially from the viewpoint of print density. The above components (a) to (d) may be used alone or in combination of two. The above can be mixed and used.

(Content of each component or constituent unit in monomer mixture or water-insoluble polymer)
Derived from the content of the above components (a) to (d) in the monomer mixture (content as an unneutralized amount) or the components (a) to (d) in the water-insoluble polymer at the time of producing the water-insoluble polymer. The content of the structural unit is as follows from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the aqueous ink.
The content of the component (a) is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less. , More preferably 25% by mass or less.
The content of the component (b) is preferably 3% by mass or more, more preferably 4% by mass or more, further preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. , More preferably 20% by mass or less.
When the component (c) is contained, the content of the component (c) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 60% by mass. Below, it is more preferably 55% by mass or less, still more preferably 50% by mass or less.
When the component (d) is contained, the content of the component (d) is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and preferably 50% by mass or more. Below, it is more preferably 45% by mass or less, still more preferably 40% by mass or less.
The mass ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.10 or more. Then, it is preferably 1.0 or less, more preferably 0.80 or less, and further preferably 0.60 or less.

(Manufacturing of water-insoluble polymer)
The water-insoluble polymer is produced by copolymerizing the monomer mixture by a known polymerization method such as a massive polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Of these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferable. If the polar organic solvent is miscible with water, it can be mixed with water and used. Examples of the polar organic solvent include fatty alcohols having 1 to 3 carbon atoms, ketones having 3 to 5 carbon atoms, ethers, esters and the like. Among these, aliphatic alcohols, ketones, or a mixed solvent of these with water is preferable, and methyl ethyl ketone or a mixed solvent of these with water is preferable.
At the time of polymerization, a polymerization initiator or a polymerization chain transfer agent can be used.
Examples of the polymerization initiator include azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile), t-butylperoxyoctate, benzoyl peroxide and the like. Examples thereof include known radical polymerization initiators such as organic peroxides of the above, and examples of the polymerization chain transfer agent include known chain transfer agents such as octyl mercaptan, mercaptans such as 2-mercaptoethanol, and thiuram disulfides.
Further, the mode of chaining the polymerization monomers is not limited, and any polymerization mode such as random, block, and graft may be used.

Preferred polymerization conditions vary depending on the type of polymerization initiator, monomer, solvent and the like used, but usually the polymerization temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher, and preferably 95 ° C. or lower. More than 80 ° C. The polymerization time is preferably 1 hour or longer, more preferably 2 hours or longer, and preferably 20 hours or shorter, more preferably 10 hours or shorter. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation and solvent distillation.
The weight average molecular weight of the water-insoluble polymer is preferably 6,000 or more, more preferably 8,000 or more, still more preferably 10,000 or more, and from the viewpoint of adsorptivity to the pigment and dispersion stability. It is preferably 200,000 or less, more preferably 100,000 or less, and more preferably 80,000 or less.
The weight average molecular weight can be measured by the method described in Examples.

[Manufacturing of pigment-containing polymer particles]
The water-insoluble polymer particles containing PY74 (pigment-containing polymer particles) can be efficiently produced by the method having the following steps I and II as an aqueous dispersion.
Step I: A mixture containing a water-insoluble polymer, an organic solvent, PY74, and water (hereinafter, also referred to as "pigment mixture") is subjected to high-pressure dispersion treatment at a pressure of 60 MPa or more, and then held at 30 ° C. or less for 15 hours or more. Step II: Water dispersion of water-insoluble polymer particles containing PY74 by removing the organic solvent from the dispersion obtained in Step I (hereinafter, "pigment water dispersion"). The process of obtaining (also called "body")

(Step I)
In step I, first, the water-insoluble polymer is dissolved in an organic solvent, then PY74, water, and if necessary, a neutralizing agent, a surfactant, etc. are added to the obtained organic solvent solution and mixed, and then mixed in water. A method for obtaining an oil-type dispersion is preferable. The order of adding the water-insoluble polymer to the organic solvent solution is not limited, but it is preferable to add water, the neutralizing agent, and PY74 in this order.
The organic solvent that dissolves the water-insoluble polymer is not limited, but aliphatic alcohols having 1 to 4 carbon atoms, ketones having 3 to 8 carbon atoms, ethers such as ethyl ether, propyl ether, butyl ether, and tetrahydrofuran, methyl acetate, etc. Examples thereof include esters such as ethyl acetate. Among these, ketones having 4 to 6 carbon atoms are more preferable, and methyl ethyl ketone and methyl isobutyl ketone are more preferable from the viewpoint of wettability to PY74, solubility of water-insoluble polymer, and adsorptivity of water-insoluble polymer to PY74. Preferably, methyl ethyl ketone is even more preferred. When the water-insoluble polymer is synthesized by the solution polymerization method, the solvent used in the polymerization may be used as it is.

(Neutralization)
When neutralizing at least a part of the salt-forming group of the water-insoluble polymer, for example, the carboxy group, the pH is preferably 7 or more and 11 or less.
As the neutralizing agent, an alkali metal hydroxide is used from the viewpoint of storage stability and ejection property of the obtained water-based ink. As the alkali metal hydroxide, sodium hydroxide and potassium hydroxide are preferable. Further, the water-insoluble polymer may be neutralized in advance.
The neutralizing agent is preferably used as an aqueous solution of the neutralizing agent from the viewpoint of sufficiently and uniformly promoting neutralization. From the above viewpoint, the concentration of the neutralizing agent aqueous solution is preferably 3% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 30% by mass or less, preferably 25% by mass or less. More preferred.
The degree of neutralization of the carboxy group of the water-insoluble polymer is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, from the viewpoint of storage stability and ejection property of the obtained water-based ink. Also, it is preferably 300 mol% or less, more preferably 200 mol% or less, still more preferably 150 mol% or less.
Here, the degree of neutralization is a value obtained by dividing the molar equivalent number of the alkali metal hydroxide by the molar equivalent number of the carboxy group of the water-insoluble polymer. Originally, the degree of neutralization does not exceed 100 mol%, but in the present invention, since it is calculated from the amount of the neutralizing agent used, it exceeds 100 mol% when the neutralizing agent is excessively used.

(Dispersion treatment of pigment mixture)
In step I, the pigment mixture is dispersed to obtain a dispersion of pigment-containing polymer particles. There are no particular restrictions on the dispersion method for obtaining the dispersion. Although the average particle size of the PY74 particles can be atomized to a desired particle size by the main dispersion alone, preferably, after the pigment mixture is pre-dispersed, a strong shear stress is further applied to perform the main dispersion. It is preferable to control the average particle size of the PY74 particles to a desired particle size.
The temperature in the pre-dispersion of step I is preferably 0 ° C. or higher, preferably 40 ° C. or lower, more preferably 30 ° C. or lower, still more preferably 25 ° C. or lower, and the dispersion time is preferably 0.5 hours. The above is more preferably 0.8 hours or more, and preferably 30 hours or less, more preferably 10 hours or less, still more preferably 5 hours or less.
When the pigment mixture is pre-dispersed, a commonly used mixing / stirring device such as an anchor blade or a dispenser blade can be used, but a high-speed stirring / mixing device is particularly preferable.

Examples of means for applying the shear stress of this dispersion include a kneader such as a roll mill and a kneader, a high-pressure homogenizer such as a microfluidic (manufactured by Microfluidic) and an ultimateizer (manufactured by Sugino Machine Limited), a paint shaker, and a bead mill. A media type disperser can be mentioned. Examples of commercially available media-type dispersers include Ultra Apex Mill (manufactured by Kotobuki Kogyo Co., Ltd.) and Pico Mill (manufactured by Asada Iron Works Co., Ltd.). A plurality of these devices can be combined. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of PY74. In this case, the PY74 can be controlled to have a desired particle size by controlling the processing pressure and the number of passes.
From the viewpoint of productivity and economy, the treatment pressure is preferably 60 MPa or more, more preferably 100 MPa or more, further preferably 130 MPa or more, and preferably 200 MPa or less, more preferably 180 MPa or less.
The number of passes is preferably 3 or more, more preferably 10 or more, preferably 30 or less, and more preferably 25 or less.

In the present invention, a mixture containing a water-insoluble polymer, an organic solvent, PY74, and water is mixed at 30 ° C. or lower from the start of the first high-pressure dispersion treatment of Step I to before the removal of the organic solvent in Step II described later. Hold for more than an hour.
When the peak component other than PY74 is extracted into the organic solvent by holding it for 15 hours or more in the presence of an organic solvent, for example, the peak component other than PY74 is removed by an operation such as further filtering the solid content. Conceivable.
Further, in the present invention, the holding time at 30 ° C. or lower after the high-pressure dispersion treatment is the time held at 30 ° C. or lower from the start of the first high-pressure dispersion treatment in step I to before the removal of the organic solvent in step II. To sum. The holding time may be collectively set after the high pressure dispersion is completed, or the holding operation may be set multiple times during the plurality of high pressure dispersions.
The holding temperature is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, and preferably 25 ° C. or lower, from the viewpoint of removing peak components other than PY74.
The holding time is preferably 20 hours or more from the viewpoint of removing peak components other than PY74, and is preferably 180 hours or less, more preferably 100 hours from the viewpoint of brightening the color and suppressing stains. It is as follows.
When holding, it is preferable to stir from the viewpoint of removing peak components other than PY74. The rotation speed of stirring is preferably 12 rotations / minute or more, and preferably 120 rotations / minute or less.

(Step II)
In step II, an aqueous dispersion of pigment-containing polymer particles (pigment aqueous dispersion) can be obtained by removing the organic solvent from the dispersion obtained in step I. It is preferable that the organic solvent in the obtained aqueous pigment dispersion is substantially removed.
Examples of the method for removing the organic solvent include a method of distilling off the organic solvent under reduced pressure conditions, a method of filtering a solid content and redispersing it in water, and the like.
In the pigment aqueous dispersion obtained by distilling off the organic solvent, it is preferable to further filter the solid content and redisperse it in water from the viewpoint of removing peak components other than PY74 from the pigment aqueous dispersion.

The concentration of the non-volatile component (solid content concentration) of the obtained aqueous pigment dispersion is preferably 10% by mass or more from the viewpoint of improving the dispersion stability of the aqueous pigment dispersion and facilitating the preparation of the water-based ink. It is preferably 15% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less.
The solid content concentration of the aqueous pigment dispersion is measured by the method described in Examples.
The average particle size of the pigment-containing polymer particles in the pigment aqueous dispersion is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 70 nm or more, from the viewpoint of reducing coarse particles and improving the ejection stability of the water-based ink. It is preferably 200 nm or less, more preferably 160 nm or less, and further preferably 150 nm or less.
The average particle size of the pigment-containing polymer particles is measured by the method described in Examples.
Further, the average particle size of the pigment-containing polymer particles in the water-based ink preferably does not cause swelling or shrinkage of the particles or aggregation between the particles, and more preferably the same as the average particle size in the pigment aqueous dispersion. .. The preferred aspect of the average particle size of the pigment-containing polymer particles in the water-based ink is the same as the preferred aspect of the average particle size in the pigment aqueous dispersion.
In the present invention, from the viewpoint of improving the water resistance, storage stability, ejection property, etc. of the obtained water-based ink, a part of the salt-forming group of the water-insoluble polymer constituting the pigment-containing polymer particles is a water-insoluble polyfunctional epoxy compound. It is also preferable to react with a cross-linking agent such as the above to cross-link the surface layer portion of the pigment-containing polymer particles to form a cross-linked structure.

[Manufacturing method of water-based ink for inkjet recording]
The aqueous dispersion (pigment aqueous dispersion) of the water-insoluble polymer particles containing PY74 obtained by the method having the above steps I and II can be used as it is as a water-based ink. It is preferable to produce a water-based ink by the method used.
Step III: A step of blending one or more selected from water and a water-soluble organic solvent into the aqueous dispersion obtained in Step II. In the method for producing a water-based ink of the present invention, the concentration of the water-based ink is adjusted and ejected. From the viewpoint of improving the properties, it is preferable to add at least water.

(Water-soluble organic solvent)
The "water solubility" of a water-soluble organic solvent means the property of being able to mix with water in any proportion.
As the water-soluble organic solvent, it is preferable to use one having a boiling point of 100 ° C. or higher and 270 ° C. or lower, and when a plurality of organic solvents having different boiling points are used, the weighted average value of the boiling points of each organic solvent is 100 ° C. or higher and 270 ° C. It is more preferable to use it in the range of ° C. or lower.
The weighted average value of the boiling points of the water-soluble organic solvent is more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher, and even more preferably 260 ° C. or lower, still more preferably 260 ° C. or lower, from the viewpoint of improving the discharge property. It is 255 ° C. or lower.
Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds and the like.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol having a molecular weight of 200 to 600, propylene glycol, dipropylene glycol, polypropylene glycol having a molecular weight of 300 to 1200, 1,2-propanediol, 1,3-propanediol, and 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol , 1,6-Hexanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, trimethylpropane, Petriol and the like can be mentioned.
Among these, 1,2-hexanediol (boiling point 224 ° C.), trimethylolpropane (boiling point 160 ° C.), and polyethylene glycol having a molecular weight of 200 to 600 (boiling point 250 ° C.) are used from the viewpoint of reducing the amount of impurities and improving the ejection property. ° C.) and one or more selected from diethylene glycol (boiling point 244 ° C.) are preferred.
Further, a water-soluble organic solvent having a boiling point of more than 270 ° C, such as pentaerythritol (boiling point 276 ° C), triethylene glycol (boiling point 287 ° C), tripropylene glycol (boiling point 273 ° C), glycerin (boiling point 290 ° C), has a boiling point. It can be used in combination with a compound below 260 ° C.

Examples of the polyhydric alcohol alkyl ether include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, and triethylene glycol monoisobutyl ether. Examples thereof include tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monobutyl ether. Further, triethylene glycol monobutyl ether (boiling point 276 ° C.) or the like can be used in combination with a water-soluble organic solvent having a boiling point of less than 270 ° C. Among these, polyethylene glycol monoalkyl ether such as diethylene glycol monoisopropyl ether is preferable from the viewpoint of reducing the amount of impurities and improving the discharge property.
Among these, one or more compounds selected from polyhydric alcohols and polyhydric alcohol alkyl ethers are preferable, and the combined use of one or more polyhydric alcohols and one or more polyhydric alcohol alkyl ethers is more preferable.

In the method for producing a water-based ink for inkjet recording of the present invention, if necessary, a surfactant that adjusts surface tension and a penetrant that controls wet spread and permeability to a printing medium, which are usually used for water-based inks. , Add various additives such as moisturizing agent, wetting agent, dispersant, viscosity modifier, defoaming agent, preservative, antifungal agent, rust preventive, etc. to suppress the drying of ink, and further filter treatment with a filter etc. It can be carried out.
The content and physical characteristics of each component of the water-based ink obtained by the production method of the present invention are as follows.

(Content of PY74 (pigment))
The content of the pigment in the water-based ink is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 2.5% by mass or more, from the viewpoint of improving the print density of the water-based ink. be. Further, from the viewpoint of lowering the ink viscosity at the time of solvent volatilization and improving ejection stability and storage stability, it is preferably 15.0% by mass or less, more preferably 10.0% by mass or less, and further preferably 7.0% by mass. % Or less.
(Total content of pigment and water-insoluble polymer)
The total content of the pigment and the water-insoluble polymer in the water-based ink is preferably 2.0% by mass or more, more preferably 2.5% by mass or more, still more preferably 3.0% by mass or more, still more preferably 3. 5.5% by mass or more, preferably 17.0% by mass or less, more preferably 12.0% by mass or less, still more preferably 10.0% by mass or less, still more preferably 8.0% by mass or less. Even more preferably, it is 6.0% by mass or less.
(Contents of water-soluble organic solvent)
The content of the water-soluble organic solvent in the water-based ink is preferably 5% by mass or more, more preferably 10% by mass, from the viewpoint of reducing the content of the organic compound which is an impurity and from the viewpoint of storage stability of the ink composition. % Or more, more preferably 15% by mass or more, and from the viewpoint of the print density of the ink composition, it is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less.
(Water content)
The content of water in the water-based ink is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 65% by mass or more, and the ink composition, from the viewpoint of storage stability of the ink composition. From the viewpoint of the print density of the object, it is preferably 99% by mass or less, more preferably 90% by mass or less, and further preferably 80% by mass or less.

(Aqueous ink physical characteristics)
The viscosity of the water-based ink at 32 ° C. is preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, still more preferably 5.0 mPa · s, from the viewpoint of improving the storage stability of the ink. It is s or more, preferably 12 mPa · s or less, more preferably 9.0 mPa · s or less, and further preferably 7.0 mPa · s or less.
The pH of the water-based ink is preferably 7.0 or more, more preferably 8.0 or more, still more preferably 8.5 or more, from the viewpoint of improving the storage stability of the ink. Further, from the viewpoint of member resistance and skin irritation, the pH is preferably 11.0 or less, more preferably 10.0 or less, and further preferably 9.5 or less.

With respect to the above-described embodiment, the present invention further discloses the following water-based ink for inkjet recording and a method for producing the water-based ink for inkjet recording.
<1> C. I. A water-based ink for inkjet recording containing Pigment Yellow 74, which was measured by the following liquid chromatograph method. I. Pigment Yellow 74 with respect to the peak area (A ₇₄ ) of C.I. I. A water-based ink for inkjet recording, wherein the ratio (A _E74 / A _{74 ) of the total area (A E74} ) of peaks other than Pigment Yellow 74 is 1.4 or less.
(Measurement method by liquid chromatograph)
Add ion-exchanged water to 4 g of water-based ink to make 200 g, add 2 g of an acetonitrile 2 mol addition of 2,7-dimethyl-4-octin-4,5-diol, stir for 24 hours, and then collect 2 g of it. And centrifuge, add 1.3 g of diethyl ether to recover the diethyl ether phase, volatilize the diethyl ether, add 1.0 g of acetonitrile to prepare a sample, and perform high performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, using an ODS column, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: Measure under the condition of 400 nm.

<2> The ratio of the peak area _(A E74 _/ A ₇₄₎ is preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.4 or more, even more preferably be 0.6 or higher The water-based ink according to <1> above, preferably 1.3 or less, more preferably 1.2 or less, still more preferably 1.1 or less.
<3> C. I. The water-based ink according to <1> or <2> above, wherein Pigment Yellow 74 is obtained by a method of diazotizing 4-nitro-o-anisidine and causing a coupling reaction with acetoacetic acid-o-anisidine.
<4> C.I. I. The water-based ink according to any one of <1> to <3> above, wherein Pigment Yellow 74 is dispersed in an aqueous medium with a polymer dispersant.
<5> C. I. Pigment Yellow 74 is C.I. I. The water-based ink according to any one of <1> to <4> above, which is used in the form of water-insoluble polymer particles containing Pigment Yellow 74.
<6> The water-based ink according to <5> above, wherein the water-insoluble polymer is a polymer having a salt-forming group in the polymer chain.
<7> Any of the above <5> or <6>, wherein the water-insoluble polymer is a water-insoluble vinyl-based polymer obtained by addition polymerization of one or more vinyl monomers selected from a vinyl compound, a vinylidene compound, and a vinylene compound. Water-based ink described in Crab.
<8> The water-insoluble vinyl-based polymer is preferably a vinyl-based polymer containing (a) a structural unit derived from an ionic monomer and (b) a structural unit derived from a macromonomer, and more preferably (c) hydrophobic. The water-based ink according to any one of <5> to <7> above, which is a vinyl-based polymer containing at least one selected from a structural unit derived from a sex monomer and (d) a structural unit derived from a nonionic monomer.

<9> The content of the structural unit derived from (a) the ionic monomer in the water-insoluble polymer is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and The water-based ink according to any one of <5> to <8> above, preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less.
<10> The content of the structural unit derived from (b) the macromonomer in the water-insoluble polymer is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and preferably. Is 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, according to any one of <5> to <9> above.
<11> When the water-insoluble polymer contains (c) a structural unit derived from a hydrophobic monomer, the content of (c) the structural unit derived from the hydrophobic monomer is preferably 10% by mass or more, more preferably 20% by mass. Any of the above <5> to <10>, which is more preferably 30% by mass or more, preferably 60% by mass or less, more preferably 55% by mass or less, still more preferably 50% by mass or less. The water-based ink described in.
<12> When the water-insoluble polymer contains (d) a structural unit derived from a nonionic monomer, the content of (d) the structural unit derived from the nonionic monomer is preferably 10% by mass or more, more preferably 15% by mass. Any of the above <5> to <11>, which is more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less. The water-based ink described in.
<13> The mass ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.10 or more. The water-based ink according to any one of <8> to <12> above, preferably 1.0 or less, more preferably 0.80 or less, still more preferably 0.60 or less.
<14> The weight average molecular weight of the water-insoluble polymer is preferably 6,000 or more, more preferably 8,000 or more, still more preferably 10,000 or more, and preferably 200,000 or less, more preferably 100. The water-based ink according to any one of <5> to <13> above, which is 000 or less, more preferably 80,000 or less.
<15> C.I. in water-based ink. I. The content of Pigment Yellow 74 is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 2.5% by mass or more, and preferably 15.0% by mass or less. The water-based ink according to any one of <1> to <14> above, more preferably 10.0% by mass or less, still more preferably 7.0% by mass or less.
<16> C.I. in the water-based ink. I. The total content of Pigment Yellow 74 and the water-insoluble polymer is preferably 2.0% by mass or more, more preferably 2.5% by mass or more, still more preferably 3.0% by mass or more, still more preferably 3.5. It is 17.0% by mass or less, preferably 17.0% by mass or less, more preferably 12.0% by mass or less, still more preferably 10.0% by mass or less, still more preferably 8.0% by mass or less, still more. The water-based ink according to any one of <5> to <15> above, preferably 6.0% by mass or less.

<17> The method for producing a water-based ink for inkjet recording according to any one of <1> to <16>, which comprises the following steps I to III.
Step I: Water-insoluble polymer, organic solvent, C.I. I. Pigment Yellow 74 and a mixture containing water were subjected to high-pressure dispersion treatment at a pressure of 60 MPa or more, and then held at 30 ° C. or lower for 15 hours or more to obtain C.I. I. Step II: Obtaining a Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step II: The organic solvent was removed from the dispersion obtained in Step I to obtain C.I. I. Step III: Step III: A step of blending one or more selected from water and a water-soluble organic solvent into the aqueous dispersion obtained in Step II to obtain an aqueous dispersion of water-insoluble polymer particles containing Pigment Yellow 74 <18> The pressure of the high-pressure dispersion treatment in the step I is preferably 60 MPa or more, more preferably 100 MPa or more, further preferably 130 MPa or more, and preferably 200 MPa or less, more preferably 180 MPa or less, according to the above <17>. How to make water-based ink.
<19> The production of the water-based ink according to <17> or <18> above, wherein the holding temperature in step I is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, and preferably 25 ° C. or lower. Method.
<20> The aqueous solution according to any one of <17> to <19>, wherein the holding time in the step I is preferably 20 hours or more, preferably 180 hours or less, and more preferably 100 hours or less. Ink manufacturing method.
<21> The method for producing a water-based ink according to any one of <17> to <20> above, wherein the water-soluble organic solvent used in Step III has a boiling point of 100 ° C. or higher and 270 ° C. or lower.
<22> The water-soluble organic solvent is preferably one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers, more preferably one or more polyhydric alcohols and one or more polyhydric alcohol alkyl ethers. The method for producing a water-based ink according to any one of <17> to <21>.
<23> The content of the water-soluble organic solvent in the water-based ink is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 40% by mass or less. The method for producing a water-based ink according to any one of <17> to <22> above, more preferably 30% by mass or less, still more preferably 25% by mass or less.

In the following production examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The weight average molecular weight of the polymer was measured by the following method.
(1) Method for measuring weight average molecular weight of polymer Gel chromatography method using N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as an eluent as a solvent [manufactured by Toso Co., Ltd.] Measurement was performed using a GPC apparatus (HLC-8120GPC), a column manufactured by Toso Co., Ltd. (TSK-GEL, α-M × 2), a flow rate of 1 mL / min], and a monodisperse polystyrene having a known molecular weight as a standard substance.
(2) Measurement of average particle size of pigment-containing polymer particles Cumulant analysis was performed using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions were a temperature of 25 ° C., an angle of 90 ° between the incident light and the detector, and 100 times of integration, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. It was diluted with water so that the measured concentration was 5 × 10 ^-3 % by mass (in terms of solid content concentration).
(3) Measurement of solid content concentration of pigment aqueous dispersion 1 g of aqueous dispersion of polymer particles containing pigment and 10 g of sodium sulfate (Glauber's salt) are uniformly mixed and spread evenly ^{on an evaporative dish (10.5 cm 2).} Then, the mixture was dried under reduced pressure at 105 ° C. for 2 hours at −0.07 MPa, the weight of the dried aqueous dispersion was measured, and the solid content concentration (% by mass) was determined by the following formula.
Solid content concentration (%) = (mass of aqueous dispersion after drying / mass of aqueous dispersion before drying) × 100

Production Example 1 (Production of Polymer Dispersant)
In the reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of the polymerization chain transfer agent (2-mercaptoethanol), and 10% of a total of 200 parts of each monomer shown in Table 1 are put and mixed, and nitrogen gas substitution is sufficiently performed. , A mixed solution was obtained.
On the other hand, the remaining 90% of the monomers shown in Table 1 was charged in the dropping funnel, and 0.27 parts of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2'-azobis (2,4-dimethyl). Valeronitrile), manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-65) 1.2 parts were added and mixed, and the mixture was sufficiently substituted with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. After 2 hours have passed at 65 ° C. from the end of the dropping, a solution prepared by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone is further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours, and the weight average molecular weight is 62. A 000 polymer solution was obtained. The results are shown in Table 1.

The details of the compounds shown in Table 1 are as follows.
(B) Styrene macromer: manufactured by Toagosei Co., Ltd., trade name: AS-6 (S), number average molecular weight: 6000, polymerizable functional group: methylenedioxy group, solid content concentration 50%
(D) Polyethylene glycol monomethacrylate 2-ethylhexyl ether: manufactured by Shin-Nakamura Chemical Industry Co., Ltd., trade name: NK ester EH-4E, average number of moles of ethylene oxide added = 4, terminal: 2-ethylhexyl group.

Example 1 (Manufacturing of water-based ink (1))
(1) Production of Aqueous Ink (1) 25 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 50 parts of methyl ethyl ketone, and a neutralizing agent (5N sodium hydroxide solution, 5N sodium hydroxide solution, 6.7 parts (for volumetric analysis) manufactured by Wako Pure Chemical Industries, Ltd. and 250 parts of ion-exchanged water were added to neutralize the salt-forming groups (neutralization degree 75 mol%), and C.I. I. Pigment Yellow 74 (manufactured by Clariant, trade name: HANSA BRILL. YELLOW 5GXW) 75 parts added, and TK Robomix (trade name) + TK homodisper 2.5 type manufactured by Primix Corporation as pre-dispersion, rotation speed 8000 Dispersed at / min for 60 minutes. The obtained dispersion was used as the main dispersion and subjected to 10-pass dispersion treatment with a microfluidics (manufactured by Microfluidics, trade name) at a pressure of 150 MPa.
While this dispersion was repeated for 10 passes, the dispersion was held at 20 ° C. for 0.5 hours with stirring using a magnetic stirrer (rotational speed 60 rpm). After the main dispersion, the dispersion was further maintained at 20 ° C. while stirring using a magnetic stirrer (rotation speed 60 rpm). The total time of holding at 20 ° C. or lower was 48 hours.
250 parts of ion-exchanged water was added to the obtained dispersion, methyl ethyl ketone was removed under reduced pressure at 60 ° C., a part of water was further removed, and the mixture was concentrated to a solid content concentration of 25% to obtain a pigment-containing polymer. An aqueous pigment dispersion in the form of particles was obtained.
Using a cooling centrifuge "himacCR22G" manufactured by Hitachi Koki Co., Ltd. and a rotor (R12A, radius 15.1 cm), 300 g of the obtained pigment aqueous dispersion was placed in a 500PA bottle of the centrifuge tube manufactured by Hitachi Koki Co., Ltd. and rotated 12000 times. A centrifugal acceleration of 24300 G was applied at / min, and the mixture was held in this state for 6 minutes.
A needleless syringe with a capacity of 25 mL (manufactured by Terumo Co., Ltd.) equipped with a surface filtration type filter (acetyl cellulose film, outer diameter: 2.5 cm, manufactured by Sartorius) with a nominal filtration accuracy of 5 μm for the supernatant liquid separated and separated by centrifugation. After filtering the solid content with, the solid content was appropriately diluted with ion-exchanged water to adjust the solid content concentration to 20%, and an aqueous dispersion (1) of water-insoluble polymer particles containing PY74 was obtained. The average particle size of the pigment-containing polymer particles in the aqueous dispersion (1) was 121 nm.
This aqueous dispersion (1) can be used as it is as a water-based ink for analysis (1).

(2) Analysis of water-based ink (1) 4 g of the water-based ink (1) obtained in the above (1) was taken into a screw tube No. 7 (capacity 50 ml) manufactured by Maruemu Corporation, and ion-exchanged water was added to make 200 g. To this, 2 g of an ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfinol 420, water-insoluble) was added, and the temperature was room temperature (23 ° C.). ) For 24 hours, collect 2 g of it, put it in a centrifugal settling tube (part No. S404332A) manufactured by Hitachi Koki Co., Ltd., and use the company's ultra-high-speed centrifuge, CS120FNX, and the company's rotor S110AT. It was centrifuged at 110,000 rpm for 28 minutes.
After the centrifugation is completed, 1.3 g of diethyl ether (manufactured by Wako Pure Chemical Industries, Ltd., reagent) is added to the centrifugal sedimentation tube, the diethyl ether phase is recovered, nitrogen gas is blown into the diethyl ether, and then acetonitrile is volatilized. (Made by Wako Pure Chemical Industries, Ltd., for HPLC) Add 1.0 g to prepare a sample, and use an ultra-high-speed single quadrupole mass spectrometer (Co., Ltd.) compatible with high-performance liquid chromatographs equipped with an ultraviolet / visible detector. As a result of analysis by LCMS-2020) manufactured by Shimadzu Corporation, four peaks were detected at 3.0 minutes, 4.1 minutes, 4.9 minutes, and 7.4 minutes.
The results are shown in FIG. The 2.5-minute peak in FIG. 1 is a ghost peak.
(Analysis conditions for high performance liquid chromatograph)
-Column: ODS (chemically bonded porous spherical silica gel surface-modified with octadecylsilyl group) Showa Denko KK, Shodex C18M 4E (4.6 mm x 250 mm, 5 μm)
-Column temperature: 40 ° C
-Eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio)
-Flow rate: 1.00 ml / min
-Detection wavelength: 400 nm

On the other hand, C.I. I. Pigment Yellow 74 (manufactured by Clariant, trade name: HANSA BRILL. YELLOW 5GXW) was added to acetonitrile and stirred at room temperature (23 ° C) for 24 hours, and filtered through a 0.2 μm PTFE membrane filter. As a result of analysis by high performance liquid chromatograph, a peak was detected at 7.4 minutes. This is C.I. I. Pigment Yellow 74 shows that it has a peak at the position of 7.4 minutes under this condition.
PY74 than 3.1 minutes, 4.1 minutes, and the total area of the three peaks of 5.0 min _{(A E74),} and 7.4 minutes of the peak area of PY74 _{(A 74),} of those peak areas The ratios (A _E74 / A ₇₄ ) are shown in Table 2.

Examples 2 and 3 and Comparative Examples 1 and 2 (manufacturing of water-based analytical inks (2) to (5))
In Example 1, the water-based inks for analysis (2) to the same as in Example 1 except that the holding time after the main dispersion by the microfluidizer was changed and the total holding time was changed as shown in Table 2. (5) was obtained. The results are shown in Table 2.

<Evaluation of water-based ink for inkjet recording>
7 parts of glycerin, 7 parts of triethylene glycol, and 5 parts of trimethylolpropane are mixed with 25 parts of the water-based inks obtained in Examples 1 to 3 and Comparative Examples 1 and 2 (the weighted average value of the boiling point of the water-soluble organic solvent is , 254.7 ° C), and further added 10 mol of ethylene oxide of acetylenol E100 (manufactured by Kawaken Fine Chemicals Co., Ltd., nonionic surfactant, 2,4,7,9-tetramethyl-5-decine-4,7-diol). Product) A 25 mL capacity syringe equipped with a surface filtration type filter (made of acetyl cellulose, outer diameter: 2.5 cm, manufactured by Sartorius), which is a mixture of 0.5 part and 55.5 parts of ion-exchanged water and has a nominal filtration accuracy of 5 μm. The water-based inks for evaluation (1) to (5) were obtained by filtration with.
Using the obtained water-based ink, the ejection property was evaluated by the following method. The results are shown in Table 2.
(Evaluation of dischargeability)
Using a commercially available inkjet printer (manufactured by Seiko Epson Corporation, product name: EM930C, piezo method), print 10 sheets of water-based ink on plain paper (manufactured by Xerox Co., Ltd., product name: 4200) in "fast mode". The printing state of the 10th sheet was observed, and the number of streaks (the number of nozzles not ejected normally) was recorded.
The smaller the number of streaks (the number of chipped nozzles), the better the ejection performance is without the occurrence of the non-ejection phenomenon due to a defect such as nozzle blockage.

From the comparison between Examples 1 to 2 and Comparative Examples 1 and 2 in Table 2, the water-based inks obtained in Examples 1 to 3 were compared to the water-based inks obtained in Comparative Examples 1 and 2 in the inkjet recorded material. It can be seen that there is no nozzle chipping and the ejection performance is excellent.

Claims (5)

C. I. Pigment Yellow 74, a polymer dispersant, an organic solvent, and water are started by a high-pressure homogenizer or a media-type disperser, held at 30 ° C. or lower for 15 hours or more , and then the organic solvent is removed . I. A water-based ink for inkjet recording containing Pigment Yellow 74.
C.I. measured by the method using the liquid chromatograph below. I. Pigment Yellow 74 with respect to the peak area (A ₇₄ ) of C.I. I. A water-based ink for inkjet recording, wherein the ratio (A _E74 / A _{74 ) of the total area (A E74} ) of peaks other than Pigment Yellow 74 is 1.4 or less.
(Measurement method by liquid chromatograph)
Add ion-exchanged water to 4 g of water-based ink to make 200 g, add 2 g of an acetonitrile 2 mol addition of 2,7-dimethyl-4-octin-4,5-diol, stir for 24 hours, and then collect 2 g of it. And centrifuge, add 1.3 g of diethyl ether to recover the diethyl ether phase, volatilize the diethyl ether, add 1.0 g of acetonitrile to prepare a sample, and perform high performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, using an ODS column, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: Measure under the condition of 400 nm. The ratio of the peak area _(A E74 _/ A ₇₄₎ is 0.1 to 1.2, water-based inkjet recording ink according to claim 1. The water-based ink for inkjet recording according to claim 1 or 2, wherein the organic solvent is at least one selected from an aliphatic alcohol having 1 to 4 carbon atoms and a ketone having 3 to 8 carbon atoms. The water-based ink for inkjet recording according to any one of claims 1 to 3, wherein the dispersion treatment is a high-pressure dispersion treatment of 60 MPa or more by a high-pressure homogenizer. The water-based ink for inkjet recording according to any one of claims 1 to 4, wherein the polymer dispersant is a water-insoluble polymer containing a structural unit derived from benzyl (meth) acrylate.

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