JP2016204515A - Aqueous pigment dispersion and inkjet recording ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous pigment dispersion for providing an inkjet recording aqueous ink which can be applied to a printer carrying a high resolution inkjet head, has reduced coarse particles and is excellent in discharge stability and to provide an inkjet recording aqueous ink using the same.SOLUTION: There is provided an aqueous pigment dispersion which comprises a block polymer P having a hydrophilic polymer block having an anionic group and a hydrophobic polymer block having an aromatic ring or a heterocyclic ring, a pigment, water and a water-miscible organic solvent D, wherein the water-miscible organic solvent D satisfies the following conditions: (1) the boiling point is 150°C or more and (2) a block polymer P solution having a solid content concentration of 24 mass% dissolved in a mixed solvent obtained by mixing triethylene glycol and the water-miscible organic solvent D at a mixing ratio of 14:5 has a peak derived from the hydrophilic polymer block by 1H-NMR measurement at 30°C.SELECTED DRAWING: None

Description

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

Pigment compositions that use pigments as coloring materials make use of the excellent light resistance of pigments, whether it is indoors or outdoors, in the paint field for automobiles and building materials, offset inks, gravure inks, flexo inks, silk screen inks Are used in various applications such as the printing ink field or the water-based ink field for inkjet recording.
Among these, water-based ink using water as a main solvent has an excellent feature that the risk of fire and the like like solvent ink can be further reduced, and water-based ink is mainly used for ink jet recording. ing.

The pigment is insoluble in water and is used as an aqueous pigment dispersion dispersed in an aqueous medium. For this reason, a technique for stably dispersing a pigment in an aqueous medium has been conventionally studied.
For example, in the presence of an organic solvent such as a ketone solvent or an alcohol solvent, a synthetic resin having a specific acid value, a base, and a colorant are mixed well using a stirrer or a dispersion device to dissolve or disperse the colorant. And a method of dispersing small droplets of a self-water dispersible resin solution containing a colorant in an aqueous medium by mixing the colored resin solution and the aqueous medium, For example, refer to paragraph 0024 of Patent Document 1 and paragraph 0025 of Patent Document 2), a method of using a block polymer compound having a hydrophobic segment and a hydrophilic segment including a hydrophobic unit and a hydrophilic unit as a pigment dispersant (for example, Patent Reference 3), an AB block polymer, A is styrene, B is acrylic acid, A has a degree of polymerization of about 5 to about 50, and B has a degree of polymerization of about 70 to about 80. A method of using an (An-Bm) block polymer as a pigment dispersant (see, for example, Patent Document 4), or a method of preparing an inkjet ink in which an acrylic block polymer is used and a pigment is dispersed with a 2-roll milling device Is known (see Patent Document 5).

On the other hand, one of the problems of the aqueous pigment dispersion is to reduce coarse particles that are considered to occur during dispersion. Coarse particles are particles that have a very large particle size compared to the average particle size of the resulting aqueous pigment dispersion, such as undispersed pigments, broken or agglomerated pigments during dispersion, or pigments It is presumed that the polymer used as a dispersant is agglomerated.
The coarse particles hinder the formation of a uniform coating film surface during coating or printing, while causing the nozzles of the inkjet head to be clogged in the method of printing by ejecting ink from the nozzles like the water-based ink for inkjet recording. In particular, along with the recent increase in resolution of ink jet printers, the density of ink jet head nozzles and the finer droplets, that is, the diameter of nozzles for ejecting ink and the higher integration have been advanced (for example, see Patent Document 6). ). As the nozzle diameter becomes smaller, the size of allowable foreign matter also becomes smaller, resulting in increased nozzle clogging. In other words, the ink that could be applied to a conventional inkjet printer is a newly developed high-resolution inkjet head. There arises a problem that the printer cannot be used.
Furthermore, the ink for an ink jet printer needs to maintain its performance for a long period of time in order to be stably ejected and printed, including the period until its use after its manufacture and the period during its use. In the case of the system ink, the finely dispersed pigment is aggregated over time, or sedimentation of the aggregate of the pigment occurs, which causes a problem that stable printing cannot be performed.

  The methods described in Patent Documents 1 to 5 are excellent methods for producing water-based inks for inkjet recording, but have not yet been studied to provide inks that are compatible with recent finer nozzle diameters and higher integration. There is room for.

Japanese Patent Laid-Open No. 08-183920 JP 2007-238949 A JP 2008-195769 A Japanese Patent Laid-Open No. 10-7955 Japanese Patent Laid-Open No. 6-157554 JP2013-993A

  An object of the present invention is to provide an aqueous pigment dispersion that can be applied to a printer equipped with a high-resolution inkjet head and gives a water-based ink for inkjet recording with reduced coarse particles and excellent long-term storage stability, and the use thereof Another object of the present invention is to provide a water-based ink for inkjet recording.

  As a method for maximizing the dispersibility of a block polymer including the hydrophobic polymer block and the hydrophilic polymer block described in Patent Document 3 and Patent Document 4, the present inventors have used a specific water-miscible organic solvent. It was found that by dispersing the pigment in the presence, the block polymer is effectively adsorbed on the crushed pigment, preventing re-aggregation of the pigment, reducing coarse particles, and obtaining long-term dispersion stability of the pigment. .

That is, the present invention contains a block polymer P having a hydrophilic polymer block having an anionic group and a hydrophobic polymer block having an aromatic ring or a heterocyclic ring, a pigment, water, and a water-miscible organic solvent D. The water-miscible organic solvent D provides an aqueous pigment dispersion that satisfies the following conditions.
(1) The boiling point is 150 ° C. or higher.
(2) Block polymer P solution having a solid content of 24% by mass dissolved in a mixed solvent of triethylene glycol and water-miscible organic solvent D in a mixing ratio of 14: 5 is a hydrophobic polymer block by 1H-NMR measurement at 30 ° C. It has a peak derived from it.

The present invention also provides a production method for obtaining the above-described aqueous pigment dispersion,
Step 1 of obtaining a colored kneaded product by kneading a block polymer P solution in which the block polymer P is previously dissolved in a water-soluble organic solvent having a boiling point of 100 ° C. or higher, a pigment, and a water-miscible organic solvent D;
Provided is a method for producing an aqueous pigment dispersion in which Step 2 in which water is added to the colored kneaded product in Step 1 to dilute in this order is provided.

  The present invention also provides a water-based ink for ink jet recording using the water-based pigment dispersion described above.

  According to the present invention, it is possible to obtain an aqueous pigment dispersion with reduced coarse particles and excellent long-term storage stability, and an aqueous ink for ink jet recording using the same.

(Block polymer P)
The block polymer P used as a pigment dispersant in the present invention is preferably a polymer comprising a hydrophobic polymer block C and a hydrophilic polymer block B and having a number average molecular weight in the range of 1000 to 6000.
The “hydrophobic polymer block C” is a polymer block having a nonpolar group such as a group having an aromatic ring or a group having a heterocyclic ring, and “hydrophilic polymer block B” is, for example, an anionic group or It is a polymer block having a polar group such as a cationic group.

The block polymer P used in the present invention is a polymer having a molecular structure in the form of a CB block in which one end of the polymer block C and one end of the polymer block B are connected directly or via a bonding group by a covalent bond ( In the present invention, this is called a “block polymer”). Moreover, it is preferable that it is a vinyl polymer from the freedom degree of design.
The polymer block C is not particularly limited as long as it is hydrophobic, and may be a homopolymer or a copolymer. Similarly, the polymer block B is not particularly limited as long as it is hydrophilic, and may be a homopolymer or a copolymer. For example, the polymer block C is preferably a hydrophobic polymer block having an aromatic ring or a heterocyclic ring, and the polymer block B is preferably a hydrophilic polymer block having an anionic group neutralized with a basic compound.

  The number average molecular weight of the block polymer P used in the present invention is 1000 to 6000, more preferably 1300 to 5000, and most preferably 1500 to 4500.

  In the present invention, the number average molecular weight is a value in terms of polystyrene measured by GPC (gel permeation chromatography), specifically a value measured under the following conditions.

(Measurement method of number average molecular weight (Mn))
It measured by the gel permeation chromatography (GPC) method on the following conditions.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (THF solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

  Since the polymer block C of the block polymer P is hydrophobic, it is easily adsorbed by the pigment in an aqueous medium, and also has a role of balancing an appropriate solubility. Specifically, for example, an alkyl group such as a butyl group such as a methyl group, an ethyl group, an isobutyl group or a t-butyl group, a cycloalkyl group such as a cyclohexyl group, an aromatic group such as a phenyl group, a biphenyl group, or a naphthyl group. And a polymer block having a repeating unit of a compound having a hydrophobic group such as. When the block polymer P is a vinyl polymer, examples of the compound constituting the polymer block C include a methyl group, an ethyl group, an alkyl group such as a butyl group such as an isobutyl group and a t-butyl group, and a cyclohexyl group such as a cyclohexyl group. A vinyl monomer having a hydrophobic group such as an aromatic group such as an alkyl group, a phenyl group, a biphenyl group or a naphthyl group is preferred.

  As the vinyl monomer constituting the polymer block C, specifically, as the (meth) acrylate monomer, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl ( (Meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxy Propyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, methacrylonitrile, 2-trimethylsiloxyethyl (meth) acrylate, glycidyl (meth) acrylate, p-tolyl (meth) acrylate, sorbyl Meth) acrylate, etc. (meth) acrylate monomers. In the present invention, (meth) acrylic acid represents a general term for acrylic acid and methacrylic acid, and (meth) acrylate represents a general term for acrylate and methacrylate.

  Further, as monomers having an aromatic ring such as styrene monomers and monomers having a heterocyclic ring such as vinylpyridine monomers, styrene, p-tert-butyldimethylsiloxystyrene, o-methylstyrene, p-methylstyrene, p -Tert-butylstyrene, p-tert-butoxystyrene, m-tert-butoxystyrene, p-tert- (1-ethoxymethyl) styrene, m-chlorostyrene, p-chlorostyrene, p-fluorostyrene, α-methyl Examples thereof include styrene monomers such as styrene and p-methyl-α-methylstyrene, vinylpyridine monomers such as 2-vinylpyridine and 4-vinylpyridine, and monomers such as vinylnaphthalene and vinylanthracene.

  These monomers can be used alone or in admixture of two or more. In particular, it includes a polymer block C of a homopolymer or copolymer obtained by homopolymerization or copolymerization of a monomer having an aromatic ring such as a styrene monomer or a monomer having a heterocycle such as a vinylpyridine monomer.

  Further, the polymer block B of the block polymer P exhibits moderate solubility in an aqueous medium because it is hydrophilic. It also has the role of imparting dispersion stability in water when it becomes a pigment dispersion. Examples of such hydrophilic polymer block B include anionic groups such as carboxyl groups, sulfonic acid groups or phosphoric acid groups, cationic groups such as amino groups, nonionic groups such as polyoxyalkylene groups and hydroxyl groups, and the like. And a polymer block having a repeating unit of a monomer residue having a hydrophilic group.

  When the block polymer P is a vinyl polymer, specific examples of the monomer having a hydrophilic group include styrene sulfonic acid, 4- (methacryloyloxy) butyl sulfonic acid, methallyl sulfonic acid, Examples include vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and salts thereof. Examples of the phosphoric acid group-containing monomer include 2- (methacryloyloxy) ethyl phosphate and salts thereof. Examples of the group-containing monomer include methacrylic acid, acrylic acid, vinyl benzoic acid, vinyl acetic acid, maleic anhydride, maleic acid, maleic ester, fumaric ester, crotonic acid, itaconic acid, fumaric acid, citraconic anhydride, mono-2- (Methacryloyloxy) ethylphthale Mono- (methacryloyloxy) ethyl succinate, mono 2- (acryloyloxy) ethyl succinate, and salts thereof. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acetate. Examples include acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and 4-hydroxybutyl acrylate. Examples of the polyalkylene oxide-containing monomer include polyethylene glycol methacrylate and polyethylene glycol acrylate. Examples of amino group-containing monomers include dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, and diethyl Aminoethyl acrylate, etc. Examples of the quaternary ammonium salt-containing monomer, [(2-methacryloyloxy) ethyl] trimethylammonium chloride, [(2-acryloyloxy) ethyl] trimethylammonium chloride and the like.

  Among them, a carboxyl group is preferable because of its preparation and availability of monomer varieties. Two carboxyl groups may be acid anhydride groups obtained by dehydration condensation within a molecule or between molecules. These monomers can be used alone or in admixture of two or more.

  The polymer block B may be a copolymer of the vinyl monomer having the hydrophilic group and another vinyl monomer. As a vinyl monomer that can be used by copolymerizing with a vinyl monomer having a hydrophilic group, a (meth) acrylate monomer is preferable in view of the copolymerizability with the vinyl monomer having a hydrophilic group. ) Acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) ) Acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate (lauryl (meth) acrylate), tridecyl (meth) acrylate, pentadecyl (meth) acrylate, hex Alkyl (meth) acrylates such as decyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (stearyl (meth) acrylate), nonadecyl (meth) acrylate, icosanyl (meth) acrylate; benzyl (meth) acrylate, etc. And phenylalkylene (meth) acrylates; alkoxyalkyl (meth) acrylates such as ethoxyethyl (meth) acrylate and the like.

Further, when the block polymer P is obtained by the living anionic polymerization method described later, the polymer block B is obtained by homopolymerizing or otherwise polymerizing (meth) acrylate having a protective group that can be regenerated into an anionic group by performing the deprotection. In the homopolymer or copolymer obtained by copolymerization with the above monomer, a polymer block in which a part or all of the protective group reproducible to the anionic group is regenerated to the anionic group is obtained. This is because, in the living anion polymerization method, when the monomer used has a group having an active proton such as an anionic group, the active terminal of the living anion polymerization polymer immediately reacts with the group having the active proton and deactivates. , No polymer is obtained. In living anionic polymerization, it is difficult to polymerize a monomer having a group having an active proton as it is. Therefore, a group having an active proton is obtained by polymerizing the group having an active proton in a protected state and then deprotecting the protecting group. Is preferably reproduced.
For this reason, when the block polymer P is obtained by a living anion polymerization method, the polymer block B is a monomer containing a (meth) acrylate having a protective group that can be regenerated into an anionic group by deprotection. It is preferable to use it. By using the monomer, the above-described inhibition of polymerization can be prevented during polymerization. An anionic group protected by a protecting group can be regenerated into an anionic group by deprotection after obtaining a block polymer.

  For example, when the anionic group is a carboxyl group, the carboxyl group can be regenerated by esterifying the carboxyl group and deprotecting it by hydrolysis or the like as a subsequent step. In this case, the protecting group that can be converted into a carboxyl group is preferably a group having an ester bond, such as a primary alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, or an n-butoxycarbonyl group. Secondary alkoxycarbonyl groups such as isopropoxycarbonyl group and sec-butoxycarbonyl group; tertiary alkoxycarbonyl groups such as t-butoxycarbonyl group; phenylalkoxycarbonyl groups such as benzyloxycarbonyl group; ethoxyethylcarbonyl group and the like; And the like.

  When the anionic group is a carboxyl group, usable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec -Butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate (lauryl (meth) ) Acrylate), tridecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (stearyl (meth) Acrylate), nonadecyl (meth) acrylate, icosanyl (meth) acrylate and other alkyl (meth) acrylates; benzyl (meth) acrylate and other phenylalkylene (meth) acrylates; ethoxyethyl (meth) acrylate and other alkoxyalkyl (meth) acrylates Etc. These (meth) acrylates (c1) can be used alone or in combination of two or more. Of these (meth) acrylates (c1), t-butyl (meth) acrylate and benzyl (meth) acrylate are preferred because the conversion reaction to a carboxyl group is easy. In view of industrial availability, t-butyl (meth) acrylate is more preferable.

((Solubility parameter of polymer block C and polymer block B)
The polymer block C and the polymer block B preferably have a numerical difference in solubility parameter. The relationship between the solubility parameters is preferably such that (solubility parameter of polymer block C) / (solubility parameter of polymer block B) is in the range of 0.29 to 0.73.
Here, the solubility parameter (Sp value) is a value obtained by multiplying the Sp value (Sp (Ui)) of the monomer unit (structural unit) constituting the polymer by the number of moles.
In the present invention, a monomer unit constituting the polymer block C, for example, a methyl group, an ethyl group, an alkyl group such as a butyl group such as an isobutyl group or a t-butyl group, a cycloalkyl group such as a cyclohexyl group, a phenyl group, or a biphenyl The value obtained by multiplying the Sp value of a monomer having a hydrophobic group such as an aromatic group such as a group or naphthyl group by the number of moles is the “solubility parameter of the polymer block C”, and the monomer unit constituting the polymer block B, for example, The number of moles in the Sp value of a monomer having a hydrophilic group such as an anionic group such as a carboxyl group, a sulfonic acid group or a phosphoric acid group, a cationic group such as an amino group, a nonionic group such as a polyoxyalkylene group or a hydroxyl group The value obtained by multiplying by is the “solubility parameter of polymer block B”.

  The Sp value (Ui) can be obtained by the Fedors formula (F) described in “polymer Engineering and Science. Vol. 14, 147 (1974)”.

In the formula (F), E _coh represents the cohesive energy density (J / mol), and V represents the molar molecular volume (cm ³ / mol).
Table 1 shows “SP values of representative monomer units (Sp (Ui)) calculated from“ SP value basics / applications and calculation methods, p67, Table 13, Hideki Yamamoto, Inc., Information Organization (2005) ”. ) "

(Method for producing block polymer P)
The block polymer P is a block polymer in which the polymer block C and the polymer block B are connected by a single bond or a linking group, and is preferably a linear polymer. The block polymer P preferably has one each of the polymer block C and the polymer block B, that is, the block polymer P is “polymer block C- (single bond or linking group) -polymer block B”. It is shown with a structure like

As a method for producing a vinyl polymer having a desired number average molecular weight in the present invention, polymerization methods such as radical polymerization, cationic polymerization, and anion polymerization can be used, and among them, a viewpoint of producing a block polymer having a controlled structure. Therefore, it is preferable to produce by using “living polymerization” such as living radical polymerization, living cationic polymerization, and living anion polymerization.
Among them, the block polymer P is preferably a vinyl polymer produced using a (meth) acrylate monomer as one of the raw materials, and as a method for producing such a vinyl polymer, living radical polymerization or living anion polymerization is preferred. .

(Block polymer P produced by living radical polymerization)
Living radical polymerization is a method using a transition metal catalyst or a RAFT agent which is an organic sulfur compound such as a dithiocarboxylic acid ester serving as a chain transfer agent ("RAFT" is a reversible addition-fragmentation chain transfer). And the like are known. In the present invention, it is preferable to reduce impurities that can cause coarse particles as much as possible. From this viewpoint, a method using a RAFT agent that does not leave metal is preferable.

RAFT polymerization uses a polymerization initiator and a reversible addition-fragmentation chain transfer agent (hereinafter referred to as RAFT agent). This polymerization is superior to other living radical polymerizations in terms of (1) applicable to various monomers and (2) applicable to a wide range of reaction conditions. The RAFT agent used to obtain the acrylic resin of the present invention is not limited to the following examples, but includes O-ethyl-S- (1-phenylethyl) dithiocarbonate, O-ethyl-S- (2-propoxyethyl). ) Dithiocarbonates, dithiocarbonates such as O-ethyl-S- (1-cyano-1-methylethyl) dithiocarbonate, cyanoethyl dithiopropionate, benzyl dithiopropionate, benzyl dithiobenzoate, acetoxyethyl dithiobenzoate, etc. Dithioesters, dithiocarbamates such as S-benzyl-N, N-dimethyldithiocarbamate, benzyl-1-pyrrolecarbodithioate, trithiols such as dibenzyltrithiocarbonate, S-cyanomethyl-S-dodecyltrithiocarbonate Examples include carbonates It is.
The RAFT agent to be used is preferably selected in accordance with the reactivity of the monomer. In particular, dithiocarbamates and dithiocarbonates are suitable for the polymerization of acrylic esters, and for the polymerization of methacrylates. Is preferably a dithioester. The RAFT agent is preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the total amount of monomers used. If it is less than 0.01 parts by mass, the molecular weight distribution is not sufficiently narrow, and if it exceeds 10 parts by mass, the average molecular weight tends to be low.

  In the living radical polymerization method, the polymerization method is not particularly limited, and a conventional method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization can be adopted, but solution polymerization is particularly preferable. When performing solution polymerization, the solvent is not particularly limited. For example, aromatic hydrocarbons such as benzene, toluene and xylene; alicyclic hydrocarbons such as cyclohexane; aliphatic hydrocarbons such as n-hexane and n-octane; ketones such as acetone, methyl ethyl ketone and cyclohexanone; Ethers such as tetrahydrofuran and dioxane; esters such as ethyl acetate and butyl acetate; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxides such as dimethyl sulfoxide; alcohols such as methanol and ethanol Polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate can be used.

  In the living radical polymerization, the first polymer block is polymerized in the presence of the RAFT agent, and then a monomer that is a raw material for the second polymer block is charged and polymerized. In the living radical polymerization, after the hydrophobic polymer block C is polymerized as an example of the first polymer block, the hydrophilic polymer block B may be polymerized as an example of the second polymer block, and vice versa. There is no limitation.

(Block polymer P produced by living anionic polymerization)
The living anionic polymerization method is based on the anionization (initiation reaction) of a polymerizable unsaturated monomer using an alkyl metal reagent, alkali metal or alkaline earth metal as a reaction initiator, and the growth terminal is deactivated. This refers to a reaction in which only an initiation reaction and a growth reaction proceed by preventing the termination reaction and the chain transfer reaction in which the active site moves to another substance in the system. That is, the growth end is always active, and the initiation reaction rate is sufficiently faster than the growth reaction rate, which is a reaction in which the growth reaction further proceeds by adding a new polymerizable unsaturated monomer in the system. This makes it easy to obtain polymer chains with uniform molecular weight.

Specific examples of the polymerization initiator used for anionic polymerization include organic lithium such as n-butyllithium, sec-butyllithium, and t-butyllithium, alkylenedilithium such as 1,4-dilithiobutane, and phenyl. Lithium, stilbene lithium, lithium naphthalene, sodium naphthalene, potassium naphthalene, n-butylmagnesium, n-hexylmagnesium, ethoxycalcium, calcium stearate, t-butoxystrontium, ethoxybarium, isopropoxybarium, ethyl mercaptobarium, t-butoxybarium Phenoxybarium, diethylaminobarium, barium stearate and the like. Of these, organolithium is preferable.
Examples of the organic lithium initiator include methyl lithium, ethyl lithium, propyl lithium, butyl lithium (n-butyl lithium, sec-butyl lithium, iso-butyl lithium, tert-butyl lithium, etc.), pentyl lithium, hexyl lithium, methoxymethyl Alkyl lithium such as lithium and ethoxymethyl lithium; phenylalkylene lithium such as benzyl lithium, α-methylstyryl lithium, 1,1-diphenyl-3-methylpentyl lithium, 1,1-diphenylhexyl lithium, phenylethyl lithium; vinyl Alkenyl lithium such as lithium, allyl lithium, propenyl lithium, butenyl lithium; alkynyl lithium such as ethynyl lithium, butynyl lithium, pentynyl lithium, hexynyl lithium Aryllithium such as phenyllithium and naphthyllithium; heterocyclic lithium such as 2-thienyllithium, 4-pyridyllithium and 2-quinolyllithium; alkyllithiummagnesium such as tri (n-butyl) magnesiumlithium and trimethylmagnesiumlithium Examples include complexes.

In living anionic polymerization, when a (meth) acrylate monomer is directly polymerized to the active end of a highly nucleophilic styrenic polymer, polymerization may not be possible due to nucleophilic attack on the carbonyl carbon. For this reason, when superposing | polymerizing a (meth) acrylate monomer, using a reaction regulator, superposing | polymerizing after adjusting nucleophilicity is performed. Specific examples of the reaction modifier include diphenylethylene, α-methylstyrene, p-methyl-α-methylstyrene, and the like.
When a reaction modifier is used, the block polymer P in the present invention is a polymer having a molecular structure in the form of a CB block in which the polymer block C and the polymer block B are connected by a reaction modifier. For example, the structure is as follows.

（１）

(1)

In formula (1), A ¹ represents an organolithium initiator residue, A ² represents a polymer block of a monomer having an aromatic ring or a heterocyclic ring, A ³ represents a polymer block containing an anionic group, and n is 1 represents an integer of 1 to 5, and B represents an aromatic group or an alkyl group.

In the general formula (1), A ¹ represents an organic lithium initiator residues. Specific examples of the organic lithium initiator include methyl lithium, ethyl lithium, propyl lithium, butyl lithium (n-butyl lithium, sec-butyl lithium, iso-butyl lithium, tert-butyl lithium, etc.), pentyl lithium, hexyl lithium, Alkyllithium such as methoxymethyllithium and ethoxymethyllithium; phenylalkylenelithium such as benzyllithium, α-methylstyryllithium, 1,1-diphenyl-3-methylpentyllithium, 1,1-diphenylhexyllithium and phenylethyllithium Alkenyl lithium such as vinyl lithium, allyl lithium, propenyl lithium, butenyl lithium; ethynyl lithium, butynyl lithium, pentynyl lithium, hexynyl lithium, etc. Alkylithium such as phenyllithium and naphthyllithium; Heterocyclic lithium such as 2-thienyllithium, 4-pyridyllithium and 2-quinolyllithium; Alkyl such as tri (n-butyl) magnesiumlithium and trimethylmagnesiumlithium Examples include lithium magnesium complex.
In the organic lithium initiator, the bond between the organic group and lithium is cleaved to generate an active terminal on the organic group side, and polymerization is started therefrom. Therefore, an organic group derived from organolithium is bonded to the polymer terminal obtained. In the present invention, an organic group derived from organolithium bonded to the polymer terminal is referred to as an organolithium initiator residue. For example, in the case of a polymer using methyl lithium as an initiator, the organic lithium initiator acid group is a methyl group, and in the case of a polymer using butyl lithium as an initiator, the organic lithium initiator acid group is a butyl group.

In the general formula (1), A ² represents a polymer block C having a hydrophobic group. A ² is preferably a group that is highly adsorbed to the pigment when it comes into contact with the pigment, in addition to the purpose of balancing moderate solubility as described above. From this viewpoint, A ² is an aromatic ring or a heterocyclic ring. It is preferably a polymer block of a monomer having
Specifically, the polymer block of a monomer having an aromatic ring or a heterocycle refers to homopolymerization or copolymerization of a monomer having an aromatic ring such as a styrene monomer or a monomer having a heterocycle such as a vinylpyridine monomer. It is a polymer block of the homopolymer or copolymer obtained in this way.
Examples of the monomer having an aromatic ring include styrene, p-tert-butyldimethylsiloxystyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, p-tert-butoxystyrene, m-tert-butoxystyrene, Styrene monomers such as p-tert- (1-ethoxymethyl) styrene, m-chlorostyrene, p-chlorostyrene, p-fluorostyrene, α-methylstyrene, p-methyl-α-methylstyrene, and vinylnaphthalene And vinyl anthracene.
Examples of the monomer having a heterocyclic ring include vinylpyridine monomers such as 2-vinylpyridine and 4-vinylpyridine.
These monomers can be used alone or in admixture of two or more.

In the general formula (1), A ³ represents a polymer block B containing an anionic group. A ³ is another object to provide a described above moderate solubility, there is a purpose of imparting dispersion stability in water when a pigment dispersion.
Examples of the anionic group in A ³ include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Among them, a carboxyl group is preferable because of its preparation and availability of monomer varieties. Two carboxyl groups may be acid anhydride groups obtained by dehydration condensation within a molecule or between molecules.

Method for introducing anionic groups of the A ³ is not particularly limited, for example, have a renewable protecting group an anionic group a (meth) acrylate is homopolymerized or copolymerized with other monomers by deprotection In the obtained homopolymer or copolymer, a part or all of the protective group that can be regenerated to the anionic group may be regenerated to an anionic group, and when the anionic group is a carboxyl group, (meth) acrylic It may be a homopolymer or a copolymer obtained by homopolymerization or copolymerization with other monomers.

There are the following methods for regenerating the ester bond of a protecting group that can be regenerated to the anionic group into an anionic group by a deprotection reaction such as hydrolysis.
The hydrolysis reaction of the ester bond proceeds under acidic conditions or basic conditions, but the conditions are slightly different depending on the group having an ester bond. For example, when the group having an ester bond is a primary alkoxycarbonyl group such as a methoxycarbonyl group or a secondary alkoxycarbonyl group such as an isopropoxycarbonyl group, a carboxyl group is obtained by hydrolysis under basic conditions. be able to. In this case, examples of the basic compound to be subjected to basic conditions include metal hydroxides such as sodium hydroxide and potassium hydroxide.

  Further, when the group having an ester bond is a tertiary alkoxycarbonyl group such as a t-butoxycarbonyl group, a carboxyl group can be obtained by hydrolysis under acidic conditions. In this case, examples of acidic compounds to be used under acidic conditions include mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; Breasted acids such as trifluoroacetic acid; Lewis acids such as trimethylsilyl triflate. The reaction conditions for hydrolysis under acidic conditions of the t-butoxycarbonyl group are disclosed in, for example, “The Chemical Society of Japan, 5th edition, Experimental Chemistry Course 16 Synthesis of Organic Compounds IV”.

  Furthermore, as a method for converting a t-butoxycarbonyl group into a carboxyl group, a method using a cation exchange resin in place of the above-mentioned acid may be mentioned. As said cation exchange resin, resin which has acid groups, such as a carboxyl group (-COOH) and a sulfo group (-SO3H), is mentioned in the side chain of a polymer chain, for example. Among these, a strong cation exchange resin having a sulfo group on the side chain of the resin is preferable because the reaction can proceed rapidly. Examples of commercially available cation exchange resins that can be used in the present invention include strongly acidic cation exchange resin “Amberlite” manufactured by Organo Corporation. Since the amount of the cation exchange resin used can be effectively hydrolyzed, the range of 5 to 200 parts by mass is preferable with respect to 100 parts by mass of the polymer represented by the general formula (1), and 10 to 100 parts by mass. The range of is more preferable.

  Further, when the group having an ester bond is a phenylalkoxycarbonyl group such as a benzyloxycarbonyl group, it can be converted to a carboxyl group by performing a hydrogenation reduction reaction. At this time, as the reaction conditions, the phenylalkoxycarbonyl group can be quantitatively regenerated into a carboxyl group by performing the reaction using hydrogen gas as a reducing agent at room temperature in the presence of a palladium catalyst such as palladium acetate.

As described above, since the reaction conditions during the conversion of the type of group to the carboxyl group are different with, for example, t- butyl as a raw material of A ³ (meth) acrylate and n- butyl (meth) acrylate with an ester bond The polymer obtained by copolymerization has a t-butoxycarbonyl group and an n-butoxycarbonyl group. Here, since the n-butoxycarbonyl group does not hydrolyze under acidic conditions where the t-butoxycarbonyl group is hydrolyzed, only the t-butoxycarbonyl group can be selectively hydrolyzed and deprotected to the carboxyl group. It becomes. Therefore, it is possible to the acid value of the adjustment of the hydrophilic block (A ³⁾ by appropriately selecting a monomer containing a (meth) acrylate having a renewable protecting group an anionic group which is a raw material monomer of A ^3.

In the case where the A ³ is a homopolymer or copolymer obtained by homopolymerizing (meth) acrylic acid or copolymerizing with other monomers, the (meth) acrylic acid or (meth) acrylate used is specifically (meth) Acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, iso-propyl (meth) acrylate, allyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate , Sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-amyl (meth) acrylate, iso-amyl (meth) acrylate, n-hexyl (meth) acrylate, (meth) acryl N-octyl acid, 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n- (meth) acrylate Tridecyl, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, (meth) Dicyclopentadienyl acrylate, adamantyl (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate , Dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, pentafluoropropyl (meth) acrylate, (meth) acrylic acid Octafluoropentyl, (me ) Acrylate pentadecafluorooctyl, (meth) acrylic acid heptadecafluorodecyl, N, N-dimethyl (meth) acrylamide, (meth) acryloyl morpholine, (meth) acrylonitrile,

Polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, polyethylene glycol-polypropylene glycol (meth) acrylate, polyethylene glycol-polybutylene glycol (meth) acrylate, polypropylene glycol-polybutylene glycol (meth) acrylate, methoxypolyethylene glycol ( (Meth) acrylate, ethoxypolyethyleneglycol (meth) acrylate, butoxypolyethyleneglycol (meth) acrylate, octoxypolyethyleneglycol (meth) acrylate, lauroxypolyethyleneglycol (meth) acrylate, stearoxypolyethyleneglycol (meth) acrylate, phenoxypolyethyleneglycol (Meta) acryle DOO, methoxy polypropylene glycol (meth) acrylate, octoxypolyethylene glycol - containing polyalkylene oxide groups such as polypropylene glycol (meth) acrylate (meth) acrylate and the like. These monomers can be used alone or in admixture of two or more.
Of the above monomers, (meth) acrylates having an aliphatic group are preferred.

In general formula (1), B represents an aromatic group or an alkyl group having 1 to 10 carbon atoms. N represents an integer of 1 to 5.
As described above, in the living anion polymerization method, when a (meth) acrylate monomer is directly polymerized to the active end of a highly nucleophilic styrenic polymer, polymerization may not be possible due to nucleophilic attack on the carbonyl carbon. is there. For this reason, when superposing | polymerizing a (meth) acrylate monomer to said A < ¹ > -A < ² >, after using a reaction modifier and adjusting nucleophilicity, superposing | polymerizing a (meth) acrylate monomer is performed. B in the general formula (1) is a group derived from the reaction modifier. Specific examples of the reaction modifier include diphenylethylene, α-methylstyrene, p-methyl-α-methylstyrene, and the like.
Thus, the block polymer P obtained by the living anion polymerization method has a CB block shape in which one end of the polymer block C and one end of the polymer block B are connected via a bonding group derived from a reaction modifier. It becomes a block polymer having a molecular structure.

(Molar ratio C: B of polymer block C to polymer block B)
In the block polymer P, it is advantageous in terms of stability of the obtained aqueous pigment dispersion that the polymer block C and the polymer block B are clearly separated. The molar ratio C: B between the polymer block C and the polymer block B is preferably in the range of 100: 10 to 100: 500. When the ratio of B is less than 10 with respect to 100 of C, it tends to be inferior in pigment dispersion stability and ejection stability during inkjet ejection. On the other hand, when the ratio of B exceeds 500 with respect to 100 of C, the hydrophilicity of the polymer becomes too high, and when the recording medium is paper or the like, it easily penetrates into the inside and the color developability deteriorates. The ratio is preferably C: B = 100: 10 to 100: 450.

The number of monomers having an aromatic ring or a heterocyclic ring constituting the polymer block C is preferably in the range of 5 to 40, more preferably in the range of 6 to 30, and most preferably in the range of 7 to 25. The number of anionic groups constituting the polymer block B is preferably in the range of 3-20, more preferably in the range of 4-17, and most preferably in the range of 5-15.
When the molar ratio C: B of the polymer block C to the polymer block B is represented by the molar ratio of the number of moles having an aromatic ring or heterocyclic ring constituting the polymer block C and the number of moles of an anionic group constituting B Is preferably 100: 7.5 to 100: 400.

(Acid value of block polymer P)
The acid value of the block polymer P is preferably 40 to 400 mgKOH / g, more preferably 40 to 300 mgKOH / g, and most preferably 40 to 190 mgKOH / g. When the acid value is less than 40 mgKOH / g, there is a possibility that the dispersion stability of the pigment and the ejection stability at the time of inkjet ejection are not sufficient. On the other hand, when the acid value exceeds 400 mgKOH / g, the hydrophilicity of the polymer increases, and the color developability decreases because it easily penetrates into the recording medium. If the acid value exceeds 190 mgKOH / g, the water resistance of the resulting ink may be affected depending on the case.

  In addition, the acid value of the polymer in this invention was measured based on JIS test method K0070-1992. Specifically, 0.5 g of a sample was dissolved in a THF solvent and titrated with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

(Neutralization rate of block polymer P)
The neutralization rate of the block polymer P used in the present invention was determined by the following equation.

(Neutralizer, basic compound)
As the basic compound for neutralizing the anionic group of the block polymer P, any known and conventional compounds can be used, for example, inorganic basic substances such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Alternatively, organic basic compounds such as ammonia, triethylamine, and alkanolamine can be used.

(Solubility of block polymer P in water)
The block polymer P used in the present invention has a water solubility of 0.2 g / 100 ml or less, and forms fine particles in water when the neutralization rate of the anionic group by the basic compound is 100%. It is preferable to do.

(Solubility in water)
In the present invention, the solubility of the block polymer P in water is defined as follows. That is, 0.5 g of a polymer whose particle size is adjusted in the range of 250 μm to 90 μm using a sieve having openings of 250 μm and 90 μm is sealed in a bag processed with a 400 mesh wire net, immersed in 50 ml of water, and at a temperature of 25 ° C. For 24 hours. After soaking for 24 hours, drying was performed by performing drying for 2 hours in a dryer set at 110 ° C. with a 400-mesh wire mesh enclosing the polymer. The change in the weight of the 400 mesh wire mesh encapsulating the polymer before and after water immersion was measured, and the solubility was calculated according to the following equation.

  In particular, the solubility in water is preferably 0.03 g / 100 ml, more preferably 0.01 g / 100 ml or less.

  When the neutralization rate of the anionic group with the basic compound is 100%, the average particle size when forming fine particles in water is preferably 350 nm or less, and more preferably 400 nm or less.

(Fine particles)
Further, in the present invention, whether or not to form fine particles in water when the neutralization rate of the anionic group with the basic compound was set to 100% was determined as follows.
(1) The acid value of the polymer is previously measured by an acid value measuring method based on JIS test method K 0070-1992. Specifically, 0.5 g of a polymer is dissolved in a tetrahydrofuran (hereinafter sometimes referred to as THF) solvent, and titrated with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator to obtain an acid value.
(2) After adding 1 g of polymer to 50 ml of water, 0.1 mol / L potassium hydroxide aqueous solution that only neutralizes the obtained acid value is added to make 100% neutralization.
(3) 100% neutralized liquid was irradiated with ultrasonic waves in an ultrasonic cleaner (SND Ultrasonic Cleaner US-102, 38 kHz self-excited transmission) at a temperature of 25 ° C. for 2 hours. Leave for 24 hours at room temperature.
After standing for 24 hours, a sample solution obtained by sampling a liquid at a depth of 2 cm from the liquid surface was used as a dynamic light scattering particle size distribution measuring device (dynamic light scattering particle size measuring device “Microtrack” manufactured by Nikkiso Co., Ltd. Using a particle size distribution meter UPA-ST150 "), it is confirmed whether or not fine particles are present by determining whether or not light scattering information by fine particle formation can be obtained.

(Particle size of fine particles)
If the particle size of the fine particles obtained from the block polymer P used in the present invention is too large, the block polymer P may not be stable in water. Therefore, the particle size of the block polymer P is preferably not so large, preferably in the range of 5 to 1,000 nm, more preferably in the range of 7 to 700 nm, and most preferably in the range of 10 to 500 nm.
In addition, the narrow particle size distribution tends to be more excellent in dispersibility, but this does not hinder the implementation when the particle size distribution is wide.
As for the particle size and particle size distribution, the dynamic light scattering type particle size distribution measuring device (dynamic light scattering type particle size measuring device “Microtrac particle size distribution meter UPA-ST150 manufactured by Nikkiso Co., Ltd. )).
The agglomeration property of the polymer block C, which is the hydrophobic property of the block polymer P, can be judged by the solubility in water and the formation of fine particles when the anionic group of the block polymer P is neutralized 100% with a basic compound. As the block polymer P in the present invention, those having a water solubility of 0.2 g / ml or less and exhibiting a cohesive force to the extent that fine particles are formed in water are preferable. A block polymer having a high solubility in water, or a block polymer in which fine particles are not formed has low hydrophobicity and weak adsorption to hydrophobic particles such as pigments, and generally a good dispersion cannot be obtained or the initial stage of dispersion Even if a good dispersed particle size is obtained, the particle size tends to increase or agglomerate and settle with time.

(Pigment)
The pigment used in the present invention is not particularly limited, and organic pigments or inorganic pigments usually used in water-based inks for water-based inkjet recording can be used. Either untreated pigment or treated pigment can be applied.

  Specifically, known inorganic pigments and organic pigments can be used. Examples of the inorganic pigment include iron oxide, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like.

  For example, the pigments used in the black ink include carbon black, No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 2200B, no. 900, no. 960, no. 980, no. 33, no. 40, No, 45, No. 45L, no. 52, HCF88, MA7, MA8, MA100, etc. are Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc. manufactured by Columbia, Regal 400R, Regal 330R, Regal 660R, Mull 660R, Mull 660R Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. are Degussa's Color Black FW1, FW2, FW2V, FW18, FW200, S170, U, S150, S35, P , V, 1400U, Special Bla k 6, the 5, 4, 4A, NIPEX150, NIPEX160, NIPEX170, NIPEX180 and the like.

  Specific examples of pigments used for yellow ink include C.I. I. Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like.

  Specific examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, 269, etc. C. I. Pigment violet 19 and the like.

  Specific examples of pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66, and the like.

  Specific examples of pigments used in white inks include silicas such as alkaline earth metal sulfates, carbonates, finely divided silicic acids, synthetic silicates, calcium silicates, alumina, alumina hydrates, Examples thereof include titanium oxide, zinc oxide, talc, and clay. The inorganic white pigment may be surface-treated by various surface treatment methods.

(water)
Water used in the present invention is a dispersion medium for the pigment dispersion finally obtained. As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. Moreover, water may be used independently and the mixed solvent which consists of water and a water-soluble solvent may be sufficient. Examples of the water-soluble solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2-methoxyethanol, Alcohols such as tetrahydrofuran; ethers such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane; dimethylformamide, N-methylpyrrolidone, and the polyhydric alcohols described above as preferred water-soluble organic solvents. These water-soluble organic solvents can be used alone or in combination.

(Water-miscible organic solvent D)
The present invention is characterized by containing the block polymer P, a pigment, water, and a water-miscible organic solvent D that satisfies the following conditions.
(1) The boiling point is 150 ° C. or higher.
(2) Block polymer P solution having a solid content of 24% by mass dissolved in a mixed solvent of triethylene glycol and water-miscible organic solvent D in a mixing ratio of 14: 5 is a hydrophobic polymer block by 1H-NMR measurement at 30 ° C. It has a peak derived from it.

The water-miscible organic solvent D satisfying (1) and (2) is presumed to play a role of relaxing the cohesion force of the block polymer P in the present invention in water to some extent during kneading.
As described above, the block polymer P used in the present invention has a water solubility of 0.2 g / ml or less and a cohesive force that forms fine particles in water. It is expected that a good dispersion can be obtained with strong adsorption to the conductive particles. On the other hand, dispersion, especially kneading dispersion may not be easy because of its strong hydrophobicity, but by using a water-miscible organic solvent D satisfying (1) and (2), coarse particles can be reduced and pigments Long-term dispersion stability can be obtained. The reason is not clear, but it is presumed that the block polymer is effectively adsorbed on the crushed pigment to prevent re-aggregation of the pigment.

(Peak derived from hydrophobic block part by 1H-NMR measurement of (2))
The measuring method of (2) is as follows.
A 0.5 ml sample of a block polymer P solution having a solid content concentration of 24% by mass dissolved in a mixed solvent having a mixing ratio of triethylene glycol and water-miscible organic solvent D of 14: 5 was placed in an NMR sample tube, and DMSO- A capillary sealed with d6 is added and set in NMR JNM-LA300 manufactured by JEOL Ltd., and 1H-NMR is measured. The measurement was performed at a flip angle of 45 °, a repetition time of 7 seconds, and the number of integrations of 16 times, and the set temperatures were 30 ° C., 50 ° C., 70 ° C., 90 ° C., and 110 ° C.

The peak derived from the hydrophobic polymer block C, that is, the peak area at the chemical shift corresponding to the hydrophobic polymer block C is measured, and the area ratio (%) to the theoretical value is obtained.
The chemical shift corresponding to the hydrophobic polymer block C is a chemical shift corresponding to the aromatic ring or the heterocyclic ring that the hydrophobic polymer block C has. Here, “having a peak derived from the hydrophobic polymer block C” means that the area ratio of the peak area of the signal to the theoretical value is 5% or more.
Chemical shifts corresponding to aromatic or heterocyclic rings appear at approximately 5-9 ppm.

  Further, the solid content concentration 24 mass% block polymer P solution itself dissolved in a mixed solvent of triethylene glycol and water-miscible organic solvent D for measuring 1H-NMR in a mixing ratio of 14: 5, for example, a water-miscible organic solvent to be used. When D itself has any peak in the vicinity of the chemical shift of the hydrophobic polymer block C, the area ratio obtained by subtracting the peak area derived from the water-miscible organic solvent D from the peak area of the obtained signal is 5 % Or more, it can be determined that it has a peak derived from the hydrophobic polymer block C.

  Triethylene glycol used for measuring 1H-NMR does not have a peak derived from the hydrophobic polymer block C at 30 ° C. This indicates that at 30 ° C., hydrophobic groups such as aromatic rings do not move actively in triethylene glycol, that is, the degree of aggregation of the polymer in solution is high. The hydrophobic polymer block C containing an aromatic ring or a heterocyclic ring has a cohesive force stronger than that of a hydrophobic group such as an alkyl group, and cannot be weakened by a glycol such as triethylene glycol. It is presumed that the adsorption to etc. is not sufficient.

  Table 2 shows a mixing ratio of 14: 5 using a block polymer P solution having a solid content concentration of 24% by mass using only triethylene glycol as a solvent and n-methyl-pyrrolidone as triethylene glycol and a water-miscible organic solvent D. The solution of the block polymer P-1 dissolved in the mixed solvent and the measurement result of each 1H-NMR are shown. The block polymer P used here was the styrene-acrylic acid block polymer P-1 used in Example 1 described later.

  From Table 2, the measurement result of 1H-NMR of the block polymer P solution having a solid content concentration of 24 mass% using only triethylene glycol as a solvent shows that the peak derived from the hydrophobic polymer block, that is, the aromatic ring of styrene, appears at 5 to 9 ppm. It can be seen that it does not appear at 30 ° C. but appears at around 90 ° C. That is, in the case of the styrene-acrylic acid block polymer P-1 used in Example 1, in triethylene glycol, the aggregation degree of the block polymer P at room temperature is high, the aggregation degree of the block polymer P is lowered, and the efficiency to the pigment is reduced. It can be estimated that good adsorption can be expected near 90 ° C.

  On the other hand, in the measurement result of 1H-NMR of the solution of the block polymer P dissolved in a mixed solvent having a mixing ratio of 14: 5 using n-methyl-pyrrolidone as the triethylene glycol and the water-miscible organic solvent D, it is 5 to 9 ppm. Since the peak derived from the aromatic ring of styrene appears at 30 ° C., the aggregation degree of the block polymer P is lowered even at room temperature in this system, and efficient adsorption to the pigment can be expected. That is, the presence of an appropriate amount of the water-miscible organic solvent that can be found in the present invention weakens the cohesive force of the hydrophobic polymer block C having a strong cohesive force such as an aromatic ring or a heterocyclic ring, thereby producing a hydrophobic pigment or the like. It is presumed that the adsorption and coating are sufficiently promoted and the performance of the block polymer can be fully exhibited.

  Specific examples of the water-miscible organic solvent D include 3-methoxybutanol, n-methyl-pyrrolidone, diethylene glycol monobutyl ether and the like. These water-miscible organic solvents D can be used alone or in combination of two or more.

The water-miscible organic solvent D and a water-soluble organic solvent other than the water-miscible organic solvent D (hereinafter sometimes referred to as water-miscible organic solvent E) may be used in combination.
Examples of the water-miscible organic solvent E include glycols such as triethylene glycol and propylene glycol. The method of finding the water-miscible organic solvent D can be applied to find the water-miscible organic solvent E. it can. Also, when using the obtained aqueous pigment dispersion as a raw material for ink jet recording ink, it has a boiling point of 100 so that it does not affect ink characteristics and is preferably applied as an ink drying inhibitor. It is preferable to have at least ° C.
The said water-miscible organic solvent E can be used 1 type or in mixture of 2 or more types.

(Method for producing aqueous pigment dispersion)
In the present invention, the aqueous pigment dispersion refers to an aqueous pigment dispersion in which a pigment before being converted into an ink is dispersed at a high concentration in water as a dispersion medium.
The pigment concentration of the aqueous pigment dispersion is usually adjusted to be 10 to 50% by mass. When using this to make ink, depending on the desired ink application and physical properties, water or additives are added as appropriate, and the pigment concentration is simply diluted to 0.1 to 20% by mass. Ink can be obtained.

In the present invention, the pigment is preferably dispersed in advance in a mixture of the block polymer P and the water-miscible organic solvent D before being dispersed in water as a dispersion medium.
That is, in the state where the water-miscible organic solvent D is present, the block polymer P, the basic compound and the pigment are mixed well using a stirrer or a dispersing device, and the pigment and the block polymer P are dispersed in water by itself. Thereafter, the dispersion and water are mixed to obtain an aqueous pigment dispersion.
At this time, the water-miscible organic solvent D may be used alone, but it is more preferable that the water-miscible organic solvent E is contained.

In the present invention, the blending amount of each raw material is not particularly limited, but it is preferable to blend using the following blending ratio as a guide.
For example, the block polymer P is preferably blended in an amount of 5 to 200 parts by mass, and more preferably 5 to 100 parts by mass with respect to 100 parts by mass of the pigment.
Further, the total amount of the water-miscible organic solvent D and the water-miscible organic solvent E is preferably 20 to 200 parts by mass, more preferably 30 to 200 parts by mass with respect to 100 parts by mass of the pigment. The ratio is 100/0 to 2/98.
Further, as described above, the basic compound is preferably used so that the neutralization rate of the block polymer P is 20% to 200%, and is used so that the neutralization rate is 80% to 150%. It is still preferred. The neutralization rate at this time is calculated by the following formula as described above.

  A step of mixing the block polymer P, the basic compound and the pigment in a state where the water-miscible organic solvent D is present, using a stirrer or a dispersing device, and performing self-water dispersion of the pigment and the block polymer P ( In the following step 1), it is preferable that the block polymer P and the water-miscible organic solvent D are mixed in advance and the block polymer P is dissolved in the water-miscible organic solvent D. Similarly, when the water-miscible organic solvent E is used, it is preferably mixed with the block polymer P or the water-miscible organic solvent D at this stage. The neutralization of the block polymer P with a basic compound may be performed at this stage, or may be performed in the process 1 described later or the process 2 diluted with water thereafter. The basic compound used may be 100% pure, but it is preferable to use an aqueous solution because of the possibility of heat generation. Further, although it is possible to contain a slight amount of water as long as the effect of the present invention is not impaired, the presence of a large amount of water in the initial pigment dispersion may reduce the pigment dispersion efficiency of the block polymer P. It is preferable to keep it in a small amount because there is a possibility that only a block polymer P is formed.

(Step 1 Step of obtaining a dispersion with pigment)
The dispersion method in Step 1 is not particularly limited and may be a known dispersion method. For example, media mill dispersion method using media such as paint shaker, bead mill, sand mill, ball mill, etc., medialess dispersion method using ultrasonic homogenizer, high pressure homogenizer, nanomizer, optimizer, etc., roll mill, Henschel mixer, pressure kneader And kneading and dispersing methods that give a strong shearing force, such as intensive mixers, Banbury mixers, and planetary mixers. Among these, the kneading dispersion method is a method of refining pigment particles by applying a strong shearing force to a mixture having a high solid content containing a pigment with a kneader, and an aqueous pigment dispersion having a high pigment concentration can be obtained. This method is preferable because it is an effective method for reducing coarse particles.

When performing step 1 by the kneading dispersion method, the block polymer P dissolved in the water-miscible organic solvent D and the pigment are charged into a kneader and kneaded. At this time, the order in which the raw materials are charged is not particularly limited, and the entire amount may be charged simultaneously, and kneading may be started, or a small amount of each may be charged. The amount of each raw material charged can be within the above-mentioned range.
In order to give a strong shearing force, which is a merit of the kneading dispersion method, to the mixture, it is preferable to knead the mixture at a high solid content ratio, and a higher shearing force can be applied to the mixture.

In order to apply a higher shearing force, the solid content ratio including the pigment and the block polymer P is preferably 30% by mass or more, and more preferably 40% by mass or more.
Moreover, in order to make the pigment concentration of the obtained aqueous pigment dispersion high, it is preferable to increase the amount of pigment in the mixture as much as possible. For example, it is preferable to set it as 30 mass% or more with respect to the said mixture whole quantity, and it is still more preferable that it is 35 mass% or more.
Further, the content ratio of the pigment and the block polymer P is not particularly limited, but is usually carried out in a mass ratio of 10 / 0.5 to 10/20, more preferably 10 / 0.5 to 10/10.

  Further, the content ratio of the water-soluble organic solvent D or the water-soluble organic solvent E and the block polymer P is not particularly limited, but is preferably 30/10 or more, and is preferably 30/10 to 90/10. Most preferably used in a range.

(Process 2 water dispersion)
An aqueous pigment dispersion containing the pigment and the block polymer P is obtained by mixing water with the dispersion obtained in the step 1 (hereinafter referred to as step 2).
The dispersion may be added to water, but it is preferable to add an aqueous medium to the dispersion because an aqueous pigment dispersion having a uniform particle diameter can be obtained.
The method of mixing water is not particularly limited, but water may be added and mixed at once, or may be added and mixed in small portions. Usually, it is dispersed using a disperser.
As the disperser used in Step 3, a known one can be used. For example, in the case of using a medium, a paint shaker, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disperse mat, an SC mill, Examples include spike mills and agitator mills. Examples of media that do not use media include ultrasonic homogenizers, nanomizers, resolvers, dispersers, and high-speed impeller dispersers. The concentration may be adjusted with a water-soluble solvent as necessary after dispersion.
Depending on the type of the disperser used, before carrying out water dispersion with the disperser, if necessary, water-miscible organic solvents D and E are further added to the dispersion, mixed, diluted, and then dispersed. It is preferable to adjust to a viscosity suitable for processing by a machine (hereinafter, this viscosity-adjusted product may be referred to as a viscosity-adjusted product). For example, when a sand mill is used, it is preferable to perform dispersion by driving the sand mill after diluting to a solid content concentration of 10 to 40 mass% and adjusting the viscosity to several tens to several hundred centipoise.
Moreover, after performing the water dispersion of the process 2, you may insert a centrifugation and a filtration process as needed.

In the present application, in Step 2, an aqueous pigment dispersion using water as a medium is formed by phase inversion emulsification or a similar mechanism.
By passing through step (1) and step (2) in this order in this order, an aqueous pigment dispersion with reduced coarse particles can be obtained.
In addition, it is presumed that the aqueous pigment dispersion obtained in this way is stabilized by inclusion or partial adsorption of the pigment in the block polymer P.

(Water-based ink for inkjet recording)
The aqueous pigment dispersion of the present invention is diluted to a desired concentration, and is used in the paint field for automobiles and building materials, in the printing ink field such as offset ink, gravure ink, flexo ink, silk screen ink, or water-based ink for inkjet recording. It can be used for various applications such as fields. Especially, since coarse particles are reduced, it can be particularly preferably used as a water-based ink for ink jet recording.
When the aqueous pigment dispersion of the present invention is applied to an aqueous ink for inkjet recording, water, a binder resin, and the like are further added to obtain desired physical properties, and a wetting agent (drying inhibitor), a penetrating agent as necessary. Or by adding other additives.
After the ink adjustment, a centrifugal separation or filtration process may be added.

(Wetting agent)
The wetting agent is added for the purpose of preventing the ink from drying. The content of the wetting agent in the ink for the purpose of preventing drying is preferably 3 to 50% by mass.
The wetting agent used in the present invention is not particularly limited, but a wetting agent that is miscible with water and can prevent clogging of the head of an inkjet printer is preferable. For example: glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butane Diol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol, sulfolane; lactones such as γ-butyrolactone; N- (2-hydroxyethyl) pyrrolidone, etc. Lactams; and glycerin and its derivatives. Among them, the inclusion of propylene glycol and 1,3-butanediol is safe and has excellent effects in ink drying properties and ejection performance.

(Penetration agent)
The penetrant is added for the purpose of improving the permeability to a recording medium and adjusting the dot diameter on the recording medium.
Examples of the penetrant include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether.
The penetrant content in the ink is preferably 0.01 to 10% by mass.

(Surfactant)
The surfactant is added to adjust ink properties such as surface tension. The surfactant that can be added for this purpose is not particularly limited, and examples include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Of these, anionic surfactants and nonionic surfactants are preferred.

  Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfate salts and sulfonates of the above, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. Specific examples include dodecylbenzene sulfonate, isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfate. , And the like salts.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkyl alkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, Polyethylene glycol polypropylene glycol block copolymer, etc. Among them, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid Preference is given to alkylolamide, acetylene glycol, oxyethylene adducts of acetylene glycol and polyethylene glycol polypropylene glycol block copolymers. Among these, those having an HLB in the range of 7 to 20 are preferable because of excellent dissolution stability.

  Other surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers. Biosurfactants such as spicrispolic acid, rhamnolipid, lysolecithin and the like can also be used.

  These surfactants can be used alone or in combination of two or more. When the surfactant is added, the addition amount is preferably in the range of 0.001 to 2% by mass, more preferably 0.001 to 1.5% by mass, and more preferably 0.01 to 1.5% by mass with respect to the total mass of the ink. More preferably, it is in the range of 1% by mass. When the addition amount of the surfactant is less than 0.001% by mass, the effect of adding the surfactant tends to be not obtained, and when it exceeds 2% by mass, problems such as blurring of the image are likely to occur. .

Moreover, antiseptic | preservative, a viscosity modifier, a pH adjuster, a chelating agent, a plasticizer, antioxidant, an ultraviolet absorber etc. can be added as needed.
In addition, the water-soluble organic solvent Q used in the step 1 includes one that functions as a wetting agent or a penetrating agent, for example. When the water-soluble organic solvent Q having such a function is used in the step 1, it is preferably added while adjusting the amount.

  The amount of pigment in the water-based ink for inkjet recording is preferably 0.1 to 20% by mass in order to obtain a sufficient image density and to ensure dispersion stability of the pigment in the ink.

(recoding media)
The recording medium of the water-based ink for inkjet recording is not particularly limited, and is an absorbent recording medium such as copy paper (PPC paper) generally used in a copying machine, a recording medium having an ink absorbing layer, There may be a non-water-absorbing recording medium that does not have absorptivity, a hard-absorbing recording medium that has a low water-absorbing property, and the like. The water-based ink for ink-jet recording of the present invention is also characterized by good color developability particularly when recording on a recording medium having an absorption layer, a non-water-absorbing recording medium, or a hardly-absorbing recording medium.

  Examples of the absorbent recording medium include plain paper, fabric, cardboard, wood, and the like. Further, examples of the recording medium having an absorption layer include inkjet dedicated paper, and specific examples thereof include, for example, Pictrico Pro Photo Paper from Pictorico Co., Ltd.

  Examples of non-water-absorbing recording media that do not have ink absorbency include those used for food packaging materials and the like, and known plastic films can be used. Specific examples include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polyamide films such as nylon, polystyrene films, polyvinyl alcohol films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, A polylactic acid film etc. are mentioned. In particular, a polyester film, a polyolefin film, and a polyamide film are preferable, and polyethylene terephthalate, polypropylene, and nylon are more preferable. Moreover, the above-mentioned film coated with polyvinylidene chloride or the like for imparting a barrier property may be used, and if necessary, a film in which a deposited layer of a metal oxide such as aluminum or a metal oxide such as silica or alumina is used in combination. May be.

The plastic film may be an unstretched film, but may be stretched in a uniaxial or biaxial direction. Further, the surface of the film may be untreated, but those subjected to various treatments for improving adhesive properties such as corona discharge treatment, ozone treatment, low temperature plasma treatment, flame treatment, glow discharge treatment and the like are preferable.
The film thickness of the plastic film is appropriately changed according to the use. For example, in the case of a flexible packaging application, the film thickness is 10 μm to 100 μm as having flexibility, durability, and curl resistance. Preferably there is. More preferably, it is 10 micrometers-30 micrometers. Specific examples thereof include Pyrene (registered trademark) manufactured by Toyobo Co., Ltd.

  Art paper such as printing paper, coated paper, lightweight coated paper, finely coated paper, and the like can be used as a recording medium having low ink water absorption and poor absorbability. These hardly absorbent recording media are those in which a coating layer is provided by applying a coating material on the surface of high-quality paper, neutral paper, etc. that are generally not surface-treated mainly composed of cellulose. Oji Paper Co., Ltd. “OK Everlight Coat” manufactured by Nippon Paper Industries Co., Ltd., “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., “OK Coat L” manufactured by Oji Paper Co., Ltd., and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. , Etc. Lightweight coated paper (A3), Oji Paper Co., Ltd. “OK Top Coat +” and Nippon Paper Industries Co., Ltd. “Aurora Coat” coated paper (A2, B2), Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Mitsubishi and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd., and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example, unless the summary is exceeded. In the following examples, “parts” and “%” are based on mass unless otherwise specified.

(Synthesis example of block polymer P)
(Synthesis Example 1)
BuLi as a polymerization initiator and St as a first monomer were introduced into the T-shaped micromixer M1 in FIG. 1 from the tube reactors P1 and P2 in FIG. 1, and a living anion polymerization was performed to form a polymer.
Next, the obtained polymer is moved to the T-shaped micromixer M2 in FIG. 1 through the tube reactor R1 in FIG. 1, and the growth regulator of the polymer is introduced into the reaction regulator (3) introduced from the tube reactor P3 in FIG. Trapped with α-methylstyrene (α-MeSt)).
Next, t-BMA as a second monomer is introduced into the T-shaped micromixer M3 from the tube reactor P4 shown in FIG. 1, and the polymer moved through the tube reactor R2 in FIG. Reaction was performed. Thereafter, the reaction was quenched with methanol to produce a block polymer (PA-1).

  At this time, the reaction temperature was set to 24 ° C. by burying the entire microreactor in a thermostat. The monomer and reaction modifier to be introduced into the microreactor are dissolved in THF, and BuLi is a commercially available 2.6M hexane solution diluted with hexane. Depending on the dilution concentration and introduction rate, the block polymer (PA-1) The molar ratio was adjusted as follows.

Mol ratio polymerization initiator of block polymer (PA-1) / first monomer / reaction modifier / second monomer = 1.0 / 10.7 / 2.7 / 8.1

  The obtained block polymer (PA-1) is hydrolyzed by treating with a cation exchange resin, the reaction solution is distilled off under reduced pressure, and the resulting solid is pulverized to give a block polymer (P-1). ) Was obtained.

(Synthesis Example 2)
200 g of propylene glycol monomethyl ether acetate (hereinafter abbreviated as PGMEA) as a solvent, 16.9 g of St as a solvent, and 2-cyanopropan-2-yl N-methyl- as a RAFT agent in 500 mL of eggplant-type Schlene containing a stir bar After adding 16 mmol of N- (pyridin-4-yl) carbamodithioate, nitrogen was bubbled into the solution in the flask at 200 mL / min for 1 minute while bubbling in the liquid. Next, the flask was placed on an 80 ° C. hot water bath, and the temperature inside the flask was raised to 80 ° C. 10 minutes after reaching 80 ° C., a solution consisting of 20 g of PGMEA and 4 mmol of a polymerization initiator 2,2′-azobisisobutyronitrile (AIBN) was fed all at once into the flask and then stirred for 5 hours while maintaining the temperature. The reaction solution was cooled to room temperature to stop the reaction. Next, 5.61 g of styrene and 8.1 g of acrylic acid were blown into the flask, and again placed on a 80 ° C. hot water bath, and the temperature inside the flask was raised to 80 ° C.
Ten minutes after reaching 80 ° C., a solution consisting of 20 g of PGMEA and polymerization initiator AIBN 4 mmo was fed all at once into the flask, then stirred for 7 hours while maintaining the temperature, and the reaction solution was cooled to room temperature to stop the reaction. The block polymer (P-2) was obtained.
When the molecular weight was measured by GPC, the number average molecular weight was 2059, the weight average molecular weight was 2875, and the degree of dispersion (Mw / Mn) was 1.25. Moreover, it was 160 when the acid value was measured.

(Method for measuring physical properties of block polymer P)
The physical property value of each obtained block polymer P was measured as follows.

(Measurement method of number average molecular weight (Mn) and weight average molecular weight (Mw))
It measured by the gel permeation chromatography (GPC) method on the following conditions.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (THF solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

(Measurement method of acid value)
It measured based on JIS test method K0070-1992. It was determined by dissolving 0.5 g of a sample in a THF solvent and titrating with 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

(Measurement method of water solubility)
A polymer having a particle size of 250 μm to 90 μm using a sieve having an opening of 250 μm and a mesh size of 90 μm is sealed in a bag processed with a 400 mesh wire net, immersed in 50 ml of water, and 24 ° C. at a temperature of 25 ° C. Stir gently for a period of time. After soaking for 24 hours, drying was performed by performing drying for 2 hours in a dryer set at 110 ° C. with a 400-mesh wire mesh enclosing the polymer. The change in the weight of the 400 mesh wire mesh encapsulating the polymer before and after water immersion was measured, and the solubility was calculated according to the following equation.

(Judgment method of fine particle formation in water and measurement method of average particle size (nm)))
(1) The acid value of the polymer is determined according to the acid value measurement method.
(2) After adding 1 g of polymer to 50 ml of water, 0.1 mol / L potassium hydroxide aqueous solution that only neutralizes the acid value of the polymer obtained in (1) above is added to 100% neutralization. And
(3) 100% neutralized liquid is dispersed by irradiating with ultrasonic waves in an ultrasonic cleaner (SND Ultrasonic Cleaner US-102, 38 kHz self-excited transmission) at a temperature of 25 ° C. for 2 hours. And let stand at room temperature for 24 hours.
After leaving for 24 hours, sample liquid sampled at a depth of 2 centimeters from the liquid surface was measured using a dynamic light scattering particle size measuring device “Microtrac particle size distribution analyzer UPA-ST150” manufactured by Nikkiso Co., Ltd. It was confirmed whether or not fine particles were present by determining whether light scattering information due to formation could be obtained.
At the same time, the average particle size was measured.

(Measurement method of surface tension)
A sample solution similar to the sample solution obtained by the method for determining the formation of fine particles in water was measured using a Wilhelmi surface tension meter.

  The raw materials, reaction conditions, and physical property values of the block polymers P-1 and P-2 obtained in the synthesis examples are shown in the table.

In Table 3 to Table 4,
BuLi represents normal butyl lithium;
St represents styrene,
AA represents acrylic acid,
DPE represents 1,1-diphenylethylene,
αMeSt represents α-methylstyrene,
tBMA represents methacrylic acid tert-butyl ester;
nBMA represents methacrylic acid n-butyl ester.

(Example of 1H-NMR measurement of water-miscible organic solvent D)
The powder of the block polymer P-1 of the synthesis example and triethylene glycol were mixed to prepare a dispersion of P-1 having a polymer concentration of 30 wt%. 0.3 g of solvent (1) triethylene glycol in 1.2 g of P-1 dispersion (abbreviated as TEG in Table 5)
(2) Propylene glycol (abbreviated PPG in Table 5)
(3) 3-methoxybutanol (abbreviation 3MB in Table 5)
(4) n-methyl-pyrrolidone (abbreviated NMP in Table 5)
(5) Diethylene glycol monobutyl ether (abbreviated as DEGMBE in Table 5)
Each was added and stirred well to obtain a measurement sample.
Each sample was taken in an NMR sample tube, a capillary sealed with DMSO-d6 was added, and 1H-NMR was measured by NMR JNM-LA300 manufactured by JEOL Ltd.

Measurement conditions: Flip angle 45 °, repetition time 7 seconds, integration number 16 times Measurement set temperature: 30 ° C, 50 ° C, 70 ° C, 90 ° C, 110 ° C

  The signal derived from the aromatic ring of the block polymer P-1 appears at a chemical shift of 5 to 8 ppm. Table 5 shows the peak area taken and the area ratio (%) to the theoretical value determined.

(Example Production method of aqueous pigment dispersion)
(Reference Example 1)
Triethylene glycol is added to and stirred in the pulverized block polymer P-1, and 100 parts of the block polymer P-1 solution made into a 30% triethylene glycol solution (30 parts as P-1), 80 parts of triethylene glycol, base As a functional compound, 13.1 parts of a 34% KOH aqueous solution was charged into a 1.0 L intensive mixer (Nippon Eirich Co., Ltd.) so as to achieve a 100% neutralization rate of the block polymer P-1, and the rotor peripheral speed was 2.94 m / s. The mixture was mixed for 30 minutes at a pan peripheral speed of 1 m / s.
Subsequently, 150 parts of a magenta pigment FASTOGEN SUPER MAGENTA RY (manufactured by DIC Corporation) was charged, and kneading was performed at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s for 60 minutes. Subsequently, 657.21 parts of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container while stirring was continued to obtain an aqueous pigment dispersion having a pigment concentration of 17.6%.
Based on the physical property values of the aqueous pigment dispersion of Reference Example 1, Examples 1 to 3 were evaluated in comparison with the physical property values.

Example 1
Triethylene glycol was added to the pulverized block polymer P-1 and stirred, and 100 parts of the block polymer P-1 solution made into a 30% triethylene glycol solution (30 parts as P-1), 18 parts of 3-methoxybutanol, Charge 62 parts of triethylene glycol and 34% KOH aqueous solution as a basic compound to a 1.0-liter intensive mixer (Nippon Eirich Co., Ltd.) so as to achieve a 100% neutralization rate of the block polymer P-1. Mixing was performed at a peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s for 30 minutes.
Subsequently, 150 parts of a magenta pigment FASTOGEN SUPER MAGENTA RY (manufactured by DIC Corporation) was charged, and kneading was performed at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s for 60 minutes. Subsequently, 657.21 parts of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container while stirring was continued to obtain an aqueous pigment dispersion having a pigment concentration of 17.6%.

(Example 2)
An aqueous pigment dispersion having a pigment concentration of 17.6% was obtained in the same manner as in Example 1 except that 3-methoxybutanol was changed to n-methyl-pyrrolidone in Example 1.

Example 3
An aqueous pigment dispersion having a pigment concentration of 17.6% was obtained in the same manner as in Example 1 except that the block polymer P-1 was changed to the block polymer P-2.

(Reference Example 2)
Triethylene glycol is added to the pulverized block polymer P-1 and stirred, and 100 parts of the block polymer P-1 solution made into a 30% triethylene glycol solution (30 parts as P-1), 50 parts of triethylene glycol, base As a functional compound, 13.1 parts of a 34% KOH aqueous solution so as to achieve a 100% neutralization rate, Fast Yellow 7413 (manufactured by Sanyo Dye: Pigment Yellow 74) as a yellow pigment, 150 parts of 1.0 L intensive mixer (Nippon Eirich Corporation) Step 1 of mixing at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s for 30 minutes was performed. The mixing was performed while paying attention to the kneaded material temperature and adjusting the rotor peripheral speed and pan peripheral speed so as not to exceed 100 ° C. Subsequently, 687.21 parts of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container while stirring, to obtain an aqueous pigment dispersion having a pigment concentration of 15.0%.
Based on the physical property values of the aqueous pigment dispersion of Reference Example 2, Examples 4 to 6 were evaluated in comparison with this.

Example 4
Triethylene glycol was added to and stirred in the pulverized block polymer P-1, and 100 parts of the block polymer P-1 solution made into a 30% triethylene glycol solution (30 parts as P-1), 15 parts of 3-methoxybutanol, Triethylene glycol 35 parts, basic compound 34% KOH aqueous solution 13.1 parts to 100% neutralization rate, yellow pigment Fast Yellow 7413 (Sanyo Dye: Pigment Yellow 74) 150 parts 1.0L Step 1 was performed in which the mixture was charged into an intensive mixer (Nippon Eirich Co., Ltd.) and mixed at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s for 30 minutes. The mixing was performed while paying attention to the kneaded material temperature and adjusting the rotor peripheral speed and pan peripheral speed so as not to exceed 100 ° C. Subsequently, 687.21 parts of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container while stirring, to obtain an aqueous pigment dispersion having a pigment concentration of 15.0%.

(Example 5)
In Example 4, an aqueous pigment having a pigment concentration of 15.0% was prepared in the same manner as in Example 4 except that 10 parts of diethylene glycol monobutyl ether and 35 parts of triethylene glycol were changed to 40 parts instead of 15 parts of 3-methoxybutanol. A dispersion was obtained.

(Example 6)
In Example 4, except having changed block polymer P-1 into block polymer P-2, it implemented similarly to Example 4 and obtained the aqueous pigment dispersion of 15.0% of pigment concentration.

(Evaluation method)
The obtained aqueous pigment dispersion was evaluated by measuring the following items.

<Volume average particle diameter>
The prepared aqueous pigment dispersion was diluted 5000 times and measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.). The measured value was an average value measured three times.

<Number of coarse particles>
The prepared aqueous pigment dispersion was diluted 250 times and measured with Accusizer 780APS (manufactured by International Business). The number of coarse particles was converted to the number of particles per ml of the aqueous pigment dispersion before dilution. The unit of (× 10 ⁸ particles / ml) is used for the number of particles in the table.
Judgment criteria
A: The number of coarse particles of 0.5 um or more is less than 10 × 10 ⁸ particles / ml
○: Number of coarse particles of 0.5 μm or more 10 to 50 × 10 ⁸ or less / ml
Δ: Number of coarse particles of 0.5 μm or more 50 to 100 × 10 ⁸ or less / ml
×: Number of coarse particles of 0.5 um or more 100 × 10 ⁸ particles / ml or more

<Ink storage stability>
In order to measure the storage stability of the inkjet ink, the following aqueous inkjet recording ink for evaluation was prepared using the prepared aqueous pigment dispersion.
The aqueous pigment dispersion was adjusted according to the pigment concentration of the prepared aqueous pigment dispersion in the following formulation of 100 parts in total so that the final pigment concentration would be 3% by mass.
About 3 parts aqueous pigment dispersion (as pigment)
Triethylene glycol monobutyl ether 10 parts 2-pyrrolidone 10 parts Glycerin 5 parts Surfinol 440 (manufactured by Air Products Japan) 0.5 part Pure water remaining

Each of the prepared water-based inks for inkjet recording was stored at 70 ° C. for 4 weeks, and the storage stability of the ink was evaluated by comparing the volume average particle diameters before and after storage.
Judgment criteria
○: Change rate of volume average particle diameter is less than ± 10%
Δ: Change rate of volume average particle diameter is ± 10% or more and less than 20%
X: Change rate of volume average particle diameter is ± 20% or more

In the table, abbreviations are as follows.
M-1: Magenta pigment (FASTOGEN SUPER MAGENTA RY: manufactured by DIC)
Y-1: Yellow pigment (Fast Yellow 7413: Sanyo dye)
KOH: potassium hydroxide aqueous solution TEG: triethylene glycol 3Me-BuOH: 3-methoxybutanol NMP: n-methyl-pyrrolidone DEGGMBE: diethylene glycol monobutyl ether pure water: ion-exchanged water

  From this result, the water-miscible organic solvent D was added to the aqueous pigment dispersions obtained in Examples 1 to 6 in which 3-methoxybutanol and n-methyl-pyrrolidone were added and dispersed as the water-miscible organic solvent D. Compared with Reference Examples 1 and 2 in which the pigment was dispersed without any dispersion, the volume average particle diameter of the dispersed pigment is small, the number of coarse particles is small, the pigment dispersibility is excellent, and the storage stability of the adjusted ink is remarkably high. It was excellent.

It is a schematic diagram of the microreactor used by this invention.

1: T-shaped micromixer M1
2: T-shaped micromixer M2
3: T-shaped micromixer M3
4: Tube reactor R1
5: Tube reactor R2
6: Tube reactor R3
7: Tube reactor P1 for pre-cooling
8: Tube reactor P2 for pre-cooling
9: Tube reactor P3 for pre-cooling
10: Tube reactor P4 for pre-cooling

Claims (4)

A block polymer P having a hydrophilic polymer block having an anionic group and a hydrophobic polymer block having an aromatic ring or a heterocyclic ring; a pigment; water; and a water-miscible organic solvent D. An aqueous pigment dispersion characterized in that the organic solvent D satisfies the following conditions.
(1) The boiling point is 150 ° C. or higher.
(2) Block polymer P solution having a solid content of 24% by mass dissolved in a mixed solvent of triethylene glycol and water-miscible organic solvent D in a mixing ratio of 14: 5 is a hydrophobic polymer block by 1H-NMR measurement at 30 ° C. It has a peak derived from it. The aqueous pigment dispersion according to claim 1, wherein the water-miscible organic solvent D and a water-soluble organic solvent other than the water-miscible organic solvent D are used in combination. A method for producing the aqueous pigment dispersion according to claim 1 or 2,
Step 1 of obtaining a colored kneaded product by kneading a block polymer P solution in which the block polymer P is previously dissolved in a water-soluble organic solvent having a boiling point of 100 ° C. or higher, a pigment, and a water-miscible organic solvent D;
A method for producing an aqueous pigment dispersion, wherein Step 2 in which water is added to the colored kneaded product in Step 1 to dilute is performed in this order. A water-based ink for ink-jet recording, wherein the water-based pigment dispersion according to claim 1 is used.

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