JP6511935B2 - Method of producing aqueous pigment dispersion and aqueous ink for inkjet recording - Google Patents

Description

  The present invention relates to a method for producing an aqueous pigment dispersion, and to an aqueous ink for inkjet recording using the aqueous pigment dispersion obtained by the production method.

A pigment composition using a pigment as a coloring material makes use of the excellent light resistance of the pigment, regardless of the indoor and outdoor paint field for automobiles and building materials, offset ink, gravure ink, flexographic ink, silk screen ink Etc. or in the field of aqueous ink for inkjet recording.
Among them, aqueous ink using water as a main solvent has an excellent feature that it can further reduce the risk of fire and the like like solvent ink, and particularly, aqueous ink becomes mainstream for ink jet recording. ing.

The pigments are used as aqueous pigment dispersions which are water insoluble and dispersed in an aqueous medium. From this point of view, methods for stably dispersing the pigment in an aqueous medium have been conventionally studied.
For example, in the presence of an organic solvent such as a ketone-based solvent or an alcohol-based solvent, a synthetic resin having a specific acid value, a base and a colorant are well mixed using a stirrer or a dispersing device to dissolve or disperse the colorant. And dispersing the droplets of the self-water-dispersible resin solution containing the coloring agent in the aqueous medium by mixing the colored resin solution with the aqueous medium after For example, refer to paragraph 0024 of patent document 1 and paragraph 0025 of patent document 2), a block polymer compound having a hydrophobic segment and a hydrophilic segment containing a hydrophobic unit and a hydrophilic unit, and a pigment such as tetrahydrofuran (THF) or the like A method of obtaining an aqueous pigment dispersion by dispersing in an organic solvent followed by water phase inversion and distilling off THF to obtain an aqueous pigment dispersion (see, for example, Patent Document 3 and Examples), AB block poly (A-styrene), B is acrylic acid, the polymerization degree of A is about 5 to about 50, and the polymerization degree of B is about 70 to about 800 (An-Bm) block polymer as a pigment dispersant There is known a method of using and adding and dispersing a pigment in a solution of the block polymer in water (see, for example, Patent Document 4 and Examples).

On the other hand, one of the problems of the aqueous pigment dispersion is to reduce coarse particles which are considered to occur during dispersion. Coarse particles are particles whose particle diameter is very large compared to the average particle diameter of the obtained aqueous pigment dispersion, and are non-dispersed pigments, broken or aggregated pigments during dispersion, or pigments It is presumed that the polymer used as the dispersant is aggregated.
The coarse particles inhibit the formation of a uniform coated film surface during coating and printing, and cause clogging of the nozzle of the ink jet head in the method of discharging ink from a nozzle and printing like an aqueous ink for ink jet recording. In particular, with the increase in resolution of ink jet printers in recent years, the density of nozzles of ink jet heads and the miniaturization of droplets, that is, the miniaturization of nozzle diameter for discharging ink, and high integration are progressing (see, for example, Patent Document 5) ). As miniaturization of the nozzle diameter progresses, the size of an acceptable foreign object also decreases, and clogging of the nozzle increases, that is, the ink which has been applied to the conventional ink jet printer is a newly developed high resolution ink jet head. There is a problem that the printer can not be used.

  The method described in Patent Document 1 is an excellent method as a method for producing an aqueous ink for ink jet recording, but there is still room for investigation to provide an ink compatible with the recent miniaturization and high integration of the nozzle diameter. is there.

Unexamined-Japanese-Patent No. 08-183920 JP 2007-238949 A JP, 2008-195769, A JP 10-7955 A JP, 2013-993, A JP, 2013-139524, A

  An object of the present invention is an aqueous pigment dispersion which can be applied to a printer equipped with a high resolution inkjet head, provides an aqueous ink for inkjet recording with reduced coarse particles and excellent dispersion stability, and an inkjet using the same An object of the present invention is to provide an aqueous recording ink.

The present inventors solved the above problems by using a block polymer as a solution in which the block polymer is dissolved in a specific water-soluble organic solvent in advance when using the block polymer as a pigment dispersant in a kneading method.
As disclosed in Patent Document 3 and Patent Document 4, a block polymer containing a polymer block A which is hydrophobic and a polymer block B which is hydrophilic is an excellent pigment dispersant. The present inventor selects the kneading method as a dispersion method as a method not disclosed in Patent Document 3 and Patent Document 4, and dissolves the block polymer in a water-soluble organic solvent such as polyhydric alcohol having a boiling point of 100 ° C. or more in advance. By using the prepared block polymer P solution as a pigment dispersant and controlling the amount of water in the initial stage of kneading, coarse particles are reduced, and an aqueous pigment dispersion which gives an aqueous ink for inkjet recording excellent in dispersion stability can be obtained. I found out.

  That is, the present invention is a method for producing an aqueous pigment dispersion containing a block polymer P, a water-soluble organic solvent, a pigment, and water, and the water-soluble organic compound having a boiling point of 100 ° C. or more in advance. An aqueous pigment dispersion in which a step 1 of kneading a block polymer P solution dissolved in a solvent and a pigment to obtain a colored kneaded product, and a step 2 of adding water to the colored kneaded product of the step 1 to dilute are performed in this order Provide a manufacturing method.

  According to the present invention, it is possible to obtain a pigment dispersion having reduced coarse particles and excellent ejection stability, and an aqueous ink for inkjet recording using the same.

(Block polymer P)
The block polymer P used as a pigment dispersant in the present invention is preferably a block polymer comprising a polymer block A which is hydrophobic and a polymer block B which is hydrophilic, and a polymer having a number average molecular weight in the range of 1000 to 6000 preferable.
The “hydrophobic polymer block A” is, for example, a polymer block having a nonpolar group such as a linear or cyclic alkyl group or an aromatic group, and the “hydrophilic polymer block B” is, for example, an anionic group Or 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 an AB block molecular structure in which one end of the polymer block A and one end of the polymer block B are covalently linked directly or via a linking group (( In the present invention, this is referred to as "block polymer". Moreover, it is preferable that it is a vinyl polymer from the freedom degree of design.
The polymer block A 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 A is preferably a hydrophobic polymer block having an aromatic ring or a heterocycle, and the polymer block B is preferably a hydrophilic polymer block having an anionic group neutralized by a basic compound.

  The number average molecular weight of the block polymer P used in the present invention is 1000 to 6000, 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), and specifically, it is a value measured under the following conditions.

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

Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were used in series connection.
"TSKgel G5000" (7.8 mm ID × 30 cm) × 1 "TSK gel G 4000" (7.8 mm ID × 30 cm) × 1 "TSK gel G 3000" (7.8 mm ID × 30 cm) × 1 This "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 volume: 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)
Tosoh Corporation "TSKgel standard polystyrene A-500"
Tosoh Corporation "TSKgel standard polystyrene A-1000"
Tosoh Corporation "TSKgel standard polystyrene A-2500"
Tosoh Corporation "TSKgel standard polystyrene A-5000"
Tosoh Corporation "TSKgel standard polystyrene F-1"
Tosoh Corporation "TSKgel standard polystyrene F-2"
Tosoh Corporation "TSKgel standard polystyrene F-4"
Tosoh Corporation "TSKgel standard polystyrene F-10"
Tosoh Corporation "TSKgel standard polystyrene F-20"
Tosoh Corporation "TSKgel standard polystyrene F-40"
Tosoh Corporation "TSKgel standard polystyrene F-80"
Tosoh Corporation "TSKgel standard polystyrene F-128"
Tosoh Corporation "TSKgel standard polystyrene F-288"
Tosoh Corporation "TSKgel standard polystyrene F-550"

  The polymer block A of the block polymer P is easily adsorbed to the pigment in an aqueous medium because of its hydrophobicity, and also has a role of balancing a suitable solubility. Specifically, for example, alkyl groups such as methyl group, ethyl group, butyl group such as isobutyl group and t-butyl group, cycloalkyl groups such as cyclohexyl group, aromatic groups such as phenyl group, biphenyl group and naphthyl group And a polymer block having a repeating unit of a compound having a hydrophobic group. When the block polymer P is a vinyl polymer, examples of the compound constituting the polymer block A include alkyl groups such as methyl group, ethyl group, butyl group such as isobutyl group and t-butyl group, and cyclo groups such as cyclohexyl group It is preferable that it is a vinyl monomer which has hydrophobic groups, such as aromatic groups, such as an alkyl group, a phenyl group, a biphenyl group, and a naphthyl group.

  Specific examples of the vinyl monomer constituting the polymer block A include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isobutyl (meth) acrylate, and t-butyl (meth) acrylate monomer as a (meth) acrylate monomer. Meta) crylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, hydroxyethyl (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 is a generic name of acrylic acid and methacrylic acid, and (meth) acrylate is a generic name of acrylate and methacrylate.

  Further, as a monomer having an aromatic ring such as a styrene-based monomer or a monomer having a heterocycle such as a vinylpyridine-based monomer, 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-based monomers such as styrene and p-methyl-α-methylstyrene, vinylpyridine-based monomers such as 2-vinylpyridine and 4-vinylpyridine, and monomers such as vinylnaphthalene and vinyl anthracene.

  These monomers can be used alone or in combination of two or more. Among them, a polymer block A of a homopolymer or a copolymer obtained by homopolymerizing or copolymerizing a monomer having an aromatic ring such as a styrene-based monomer or a monomer having a heterocycle such as a vinylpyridine-based monomer is preferable.

  In addition, the polymer block B of the block polymer P exhibits appropriate solubility in an aqueous medium because of its hydrophilicity. It also has the role of imparting dispersion stability in water when it becomes a pigment dispersion. As such a hydrophilic polymer block B, for example, 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 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 monomers having a hydrophilic group include styrene sulfonic acid, 4- (methacryloyloxy) butyl sulfonic acid and methallyl sulfonic acid as sulfonic acid group-containing monomers. Examples thereof include vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and salts thereof, and examples of phosphoric acid group-containing monomers include 2- (methacryloyloxy) ethyl phosphate and salts thereof, and the like. Examples of the group-containing monomer include methacrylic acid, acrylic acid, vinylbenzoic acid, vinylacetic acid, maleic acid, maleic acid, maleic acid ester, fumaric acid ester, crotonic acid, itaconic acid, fumaric acid, citraconic acid anhydride, mono 2- (Methacryloyloxy) ethyl phthale And mono 2- (methacryloyloxy) ethyl succinate, mono 2- (acryloyloxy) ethyl succinate, and salts thereof, and the like, and examples of hydroxyl group-containing monomers include 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate. Crylates, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate and the like are listed, and as the polyalkylene oxide-containing monomer, polyethylene glycol methacrylate, polyethylene glycol acrylate and the like are listed. And amino group-containing monomers such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, 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 in view of its preparation and availability of monomer varieties. In addition, two carboxyl groups may form an acid anhydride group which is dehydrated and condensed in a molecule or between molecules. These monomers can be used alone or in combination of two or more.

  Also, the polymer block B may be a copolymer of the vinyl monomer having the hydrophilic group and another vinyl monomer. As a vinyl monomer which can be copolymerized with a vinyl monomer having a hydrophilic group and used, a (meth) acrylate monomer is preferable in view of the copolymerizability with a vinyl monomer having a hydrophilic group, specifically methyl (meth (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, 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 And phenylalkylene (meth) acrylates; alkoxyalkyl (meth) acrylates such as ethoxyethyl (meth) acrylate.

Furthermore, when obtaining said block polymer P by the below-mentioned living anion polymerization method, said polymer block B homopolymerizes the (meth) acrylate which has a protective group which can be reproduced | regenerated to anionic group by performing said deprotection. In the homopolymer or copolymer obtained by copolymerizing with the monomer of the present invention, a polymer block in which some or all of the renewable protecting groups of the anionic groups are regenerated into anionic groups is obtained. This is because in the living anion polymerization method, when the monomer used is a monomer having a group having an active proton such as an anionic group, the active end of the living anion polymerization polymer immediately reacts with the group having the active proton to deactivate it. , A polymer can not be obtained. In living anionic polymerization, it is difficult to directly polymerize a monomer having a group having an active proton, so polymerization is performed in a state in which the group having an active proton is protected, and then the protective group is deprotected to a group having an active proton It is preferable to play
For this reason, when the block polymer P is obtained by living anionic polymerization, the polymer block B is a monomer containing a (meth) acrylate having a protective group which can be regenerated to an anionic group by deprotection. It is preferred to use. By using the monomer, the above-mentioned inhibition of the polymerization can be prevented during the polymerization. Further, the anionic group protected by the protecting group can be regenerated to an anionic group by deprotecting after obtaining the block polymer P.

  For example, when the anionic group is a carboxyl group, the carboxyl group can be regenerated by esterifying the carboxyl group and deprotecting by hydrolysis or the like as a subsequent step. In this case, as a protective group which can be converted to a carboxyl group, a group having an ester bond is preferable, and for example, a primary alkoxycarbonyl group such as methoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group, n-butoxycarbonyl group and the like Secondary alkoxycarbonyl groups such as isopropoxycarbonyl group, sec-butoxycarbonyl group; tertiary alkoxycarbonyl groups such as t-butoxycarbonyl group; phenylalkoxycarbonyl groups such as benzyloxycarbonyl group; ethoxyethyl carbonyl group etc. 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 ) Acrylates), tridecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (stearyl (meth) acrylate) Acrylate), alkyl (meth) acrylates such as nonadecyl (meth) acrylate and icosanyl (meth) acrylate; phenyl alkylene (meth) acrylates such as benzyl (meth) acrylate; alkoxyalkyl (meth) acrylates such as ethoxyethyl (meth) acrylate Etc. These (meth) acrylates (c1) can be used alone or in combination of two or more. Further, among these (meth) acrylates (c1), t-butyl (meth) acrylate and benzyl (meth) acrylate are preferable because they are easy to convert to a carboxyl group. Moreover, in consideration of industrial availability, t-butyl (meth) acrylate is more preferable.

((Solubility parameter of polymer block A and polymer block B)
Further, it is preferable that the polymer block A and the polymer block B have a numerical difference in solubility parameter. The relationship of solubility parameter is preferably such that (solubility parameter of polymer block A) / (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 (constituting unit) constituting the polymer by the number of moles.
In the present invention, monomer units constituting the polymer block A, for example, alkyl groups such as methyl group, ethyl group, butyl group such as isobutyl group and t-butyl group, cycloalkyl groups such as cyclohexyl group, phenyl group, biphenyl "Solubility parameter of polymer block A" is a value obtained by multiplying the Sp value of a monomer having a hydrophobic group such as a group or an aromatic group such as a naphthyl group by the number of moles, and a monomer unit constituting the polymer block B, for example, The Sp value of the 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, or a nonionic group such as a polyoxyalkylene group or a hydroxyl group The value obtained by multiplying is the “solubility parameter of polymer block B”.

  Sp value (Ui) can be calculated | required by Numerical formula (F) of the Fedors described in "polymer Engineering and Science. Vol. 14, 147 (1974)."

In the formula (F), _Ecoh represents cohesive energy density (J / mol) and V represents molar molecular volume (cm ³ / mol).
Table 1 shows the “Sp values (Sp (Ui) of representative monomer units) calculated from“ SP values Basic / application and calculation method, p67, Table 13, Hideki Yamamoto, Inc. Information Technology Co., Ltd. (2005) ”. Show.

(Method of producing block polymer P)
The block polymer P is a block polymer in which the polymer block A and the polymer block B are linked by a single bond or a linking group, and is preferably a linear polymer. Further, in the block polymer P, it is preferable that the polymer block A and the polymer block B have one each, that is, the block polymer P is "polymer block A-(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 number average molecular weight desired in the present invention, radical polymerization, cationic polymerization, anionic polymerization and the like can be used, and from the viewpoint of producing a block polymer having a controlled structure, living It is preferable to manufacture by using "living polymerization", such as radical polymerization, living cationic polymerization, and living anion polymerization.
Among them, the block polymer P is preferably a vinyl polymer produced by using (meth) acrylate monomer as one of the raw materials, and living radical polymerization or living anionic polymerization is preferable as a method for producing such a vinyl polymer .
The polymerization method is not particularly limited, and conventional methods such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization can be employed, with solution polymerization being particularly preferred.

(Block polymer P produced by living radical polymerization)
Living radical polymerization can be carried out using a transition metal catalyst or a RAFT agent that is an organic sulfur compound such as dithiocarboxylic acid ester as a chain transfer agent ("RAFT" is reversible addition-fragmentation chain transfer: Reversible Addition-fragmentation Chain transfer And the like are known. In the present invention, it is preferable to reduce impurities that may cause coarse particles as much as possible, and from this viewpoint, a method using a RAFT agent free of metal is preferable.

In RAFT polymerization, a polymerization initiator and a reversible addition cleavage type chain transfer agent (hereinafter referred to as RAFT agent) are used. This polymerization is superior in productivity as compared to other living radical polymerizations in that (1) application to various monomers and (2) application 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 O-ethyl-S- (1-phenylethyl) dithiocarbonate, O-ethyl-S- (2-propoxyethyl) Dithiocarbonates such as dithiocarbonate, 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-pyrrole carbodioate, etc., trithiols such as dibenzyl trithiocarbonate, S-cyanomethyl-S-dodecyl trithiocarbonate, etc. Carbonates etc 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 acid esters, and for the polymerization of methacrylic acid esters. Are preferably dithioesters. The RAFT agent is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.05 to 3 parts by mass, with respect to 100 parts by mass of the total amount of monomers used. When the amount is less than 0.01 parts by mass, the molecular weight distribution does not narrow sufficiently, and when the amount is more than 10 parts by mass, the average molecular weight tends to be low.

  When solution polymerization is carried out by living radical 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 And polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate;

  In living radical polymerization, after the first polymer block is polymerized in the presence of a RAFT agent, monomers serving as a raw material of the second polymer block are charged and polymerized. In living radical polymerization, after polymerizing the hydrophobic polymer block A 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)
When solution polymerization is performed by living anion polymerization, examples of the solvent include hydrocarbon solvents such as pentane, hexane, octane, cyclohexane, benzene, toluene, xylene, decalin, tetralin, and derivatives thereof; diethyl ether, tetrahydrofuran ( And ether solvents such as THF), 1,4-dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diglyme and the like. These organic solvents can be used alone or in combination of two or more.

  The living anionic polymerization method is based on the anionization (initiation reaction) of a polymerizable unsaturated monomer using an alkyl metal reagent, an alkali metal or an alkaline earth metal as a reaction initiator, and deactivation of the growth terminal. A termination reaction and a reaction in which only the initiation reaction and the growth reaction proceed by stopping the progress of the chain transfer reaction where the active site is transferred to other substances in the system. That is, the growth end is always active, and by adding a polymerizable unsaturated monomer newly into the system, the growth reaction proceeds further. The initiation reaction rate is made sufficiently faster than the growth reaction rate. This makes it easier to obtain polymer chains of uniform molecular weight.

Specific examples of the polymerization initiator used in the anionic polymerization include organolithiums such as n-butyllithium, sec-butyllithium and t-butyllithium, alkylene dilithiums such as 1,4-dilithiobutane, and phenyl. Lithium, stilbene lithium, lithium naphthalene, sodium naphthalene, potassium naphthalene, n-butyl magnesium, n-hexyl magnesium, ethoxy calcium, calcium stearate, t-butoxy strontium, ethoxy barium, isopropoxy barium, ethyl mercapto barium, t-butoxy barium And phenoxybarium, diethylaminobarium, barium stearate and the like. Among them, organic lithium is preferable.
As the organic lithium initiator, methyllithium, ethyllithium, propyllithium, butyllithium (n-butyllithium, sec-butyllithium, iso-butyllithium, tert-butyllithium etc.), pentyllithium, hexyllithium, methoxymethyl Alkyl lithium such as lithium and ethoxy methyl lithium; benzyl lithium, α-methyl styryl lithium, 1,1-diphenyl-3-methyl pentyl lithium, 1,1-diphenyl hexyl lithium, phenyl alkylene lithium such as phenylethyl lithium; vinyl Alkenyllithiums such as lithium, allyllithium, propenyllithium and butenyllithium; alkynes such as ethynyllithium, butynyllithium, pentynyllithium and hexynyllithium Aryllithium such as phenyllithium and naphthyllithium; heterocyclic lithium such as 2-thienyllithium, 4-pyridyllithium and 2-quinolyllithium; alkyllithium magnesium such as tri (n-butyl) magnesiumlithium and trimethylmagnesiumlithium And the like.

In living anionic polymerization, when it is attempted to directly polymerize a (meth) acrylate monomer to the active end of a strongly nucleophilic styrenic polymer, it may not be possible to polymerize due to nucleophilic attack on carbonyl carbon. For this reason, when polymerizing a (meth) acrylate monomer, using a reaction control agent and polymerizing after adjusting a nucleophilic property is performed. Specific examples of the reaction modifier include diphenylethylene, α-methylstyrene, p-methyl-α-methylstyrene and the like.
When a reaction control agent is used, the block polymer P in the present invention is a polymer having an AB block molecular structure in which the polymer block A and the polymer block B are linked by a reaction control agent. 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 heterocycle, A ³ represents a polymer block containing an anionic group, and n represents B represents an aromatic group or an alkyl group.

In general formula (1), A ¹ represents an organolithium initiator residue. Specific examples of organic lithium initiators include methyllithium, ethyllithium, propyllithium, butyllithium (n-butyllithium, sec-butyllithium, iso-butyllithium, tert-butyllithium etc.), pentyllithium, hexyllithium, Alkyl lithiums such as methoxymethyllithium and ethoxymethyllithium; phenyllithiums such as benzyllithium, α-methylstyryllithium, 1,1-diphenyl-3-methylpentyllithium, 1,1-diphenylhexyllithium and phenylethyllithium Alkenyllithium such as vinyllithium, allyllithium, propenyllithium and butenyllithium; ethynyllithium, butynyllithium, pentynyllithium, hexynyllithium and the like Alkyllithium; Aryllithium 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 Lithium magnesium complex etc. are mentioned.
In the organic lithium initiator, the bond between the organic group and lithium is cleaved to form an active end on the organic group side, from which polymerization is initiated. Therefore, an organic group derived from organolithium is bonded to the end of the resulting polymer. In the present invention, the 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 methyllithium as an initiator, the organolithium initiator acid group is a methyl group, and in the case of a polymer using butyllithium as an initiator, the organolithium initiator acid group is a butyl group.

In the general formula (1), A ² represents a polymer block A having a hydrophobic group. A ² is preferably a group having high adsorption to the pigment when in contact with the pigment, in addition to the purpose of balancing the appropriate solubility as described above, and from that viewpoint, A ² is an aromatic ring or a heterocyclic ring It is preferable that it is a polymer block of a monomer having
Specifically, the polymer block of a monomer having an aromatic ring or a heterocycle is obtained by homopolymerizing or copolymerizing a monomer having an aromatic ring such as a styrene-based monomer or a monomer having a heterocycle such as a vinylpyridine-based monomer. It is a polymer block of homopolymer or copolymer obtained by
As a monomer having an aromatic ring, styrene, p-tert-butyldimethylsiloxystyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, p-tert-butoxystyrene, m-tert-butoxystyrene, Styrene-based monomers such as p-tert- (1-ethoxymethyl) styrene, m-chlorostyrene, p-chlorostyrene, p-fluorostyrene, α-methylstyrene, p-methyl-α-methylstyrene, and vinyl naphthalene And vinyl anthracene.
Moreover, as a monomer which has a heterocyclic ring, vinyl pyridine type monomers, such as 2-vinylpyridine and 4-vinylpyridine, are mention | raise | lifted.
These monomers can be used alone or in combination of two or more.

In the general formula (1), A ³ represents a polymer block B comprising 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.
Anionic group in A ³ is, for example, a carboxyl group, a sulfonic acid group or phosphoric acid group, and the like. Among them, a carboxyl group is preferable in view of its preparation and availability of monomer varieties. In addition, two carboxyl groups may form an acid anhydride group which is dehydrated and condensed in 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, some or all of the renewable protecting groups for 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 copolymer obtained by homopolymerizing or copolymerizing an acid with another monomer.

The following method is available as a method for regenerating an ester bond of a protective group which can be regenerated to an anionic group to an anionic group by a deprotection reaction such as hydrolysis.
The hydrolysis reaction of an ester bond proceeds under both acidic and basic conditions, but the conditions are slightly different depending on the group having an ester bond. For example, in the case where 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. Under the present circumstances, as a basic compound made into basic conditions, metal hydroxides, such as sodium hydroxide and potassium hydroxide, etc. are mentioned, for example.

  When the group having an ester bond is a tertiary alkoxycarbonyl group such as t-butoxycarbonyl group, a carboxyl group can be obtained by hydrolysis under acidic conditions. Under the present circumstances, as an acidic compound made into acidic conditions, mineral acids, such as hydrochloric acid, a sulfuric acid, and a phosphoric acid; Brested acids, such as trifluoroacetic acid; Lewis acids, such as trimethyl silyl triflate etc. are mentioned, for example. The reaction conditions for hydrolysis under the acidic condition of t-butoxycarbonyl group are disclosed, for example, in “The Chemical Society of Japan, 5th Edition, Experimental Chemistry Lecture 16 Synthesis of Organic Compounds IV”.

  Furthermore, as a method of converting a t-butoxycarbonyl group into a carboxyl group, a method using a cation exchange resin in place of the above-mentioned acid may also be mentioned. As said cation exchange resin, resin which has acidic radicals, such as a carboxyl group (-COOH) and a sulfo group (-SO3H), is mentioned to the side chain of a polymer chain, for example. Among these, a cation exchange resin exhibiting strong acidity having a sulfo group in the side chain of the resin is preferable because it can accelerate the reaction. As a commercial item of the cation exchange resin which can be used by this invention, the strong acidic cation exchange resin "Amberlite" etc. by Organo Ltd. are mentioned, for example. The amount of the cation exchange resin used is preferably in the range of 5 to 200 parts by mass, and 10 to 100 parts by mass, with respect to 100 parts by mass of the polymer represented by the general formula (1), because it can be effectively hydrolyzed. Is more preferable.

  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. Under the present circumstances, as reaction conditions, a phenyl alkoxy carbonyl group can be quantitatively regenerated to a carboxyl group by performing reaction using hydrogen gas as a reducing agent in presence of palladium catalysts, such as palladium acetate, at room temperature.

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 will have t-butoxycarbonyl group and n-butoxycarbonyl group. Here, since the n-butoxycarbonyl group is not hydrolyzed under the acidic conditions where the t-butoxycarbonyl group is hydrolyzed, only the t-butoxycarbonyl group can be selectively hydrolyzed to be 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.

When the above A ³ is a homopolymer or copolymer obtained by homopolymerizing or copolymerizing (meth) acrylic acid with other monomers, specifically (meth) acrylic acid or (meth) acrylate to be used is (meth) Acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, iso-propyl (meth) acrylate, allyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate , (Meth) acrylic acid sec-butyl, (meth) acrylic acid tert-butyl, (meth) acrylic acid n-amyl, (meth) acrylic acid iso-amyl, (meth) acrylic acid n-hexyl, (meth) acrylic Acid n-octyl, 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n- (meth) acrylate Tridecyl, n-stearyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate , (Meth) acrylic acid tricyclodecanyl, (meth) acrylic acid dicyclopentadienyl, (meth) acrylic acid adamantyl, (meth) acrylic acid glycidyl, (meth) acrylic acid tetrahydrofurfuryl, (meth) acrylic acid 2-methoxyethyl, 2-ethoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, (Meth) acrylic acid pentafluoro Ropyr, octafluoropentyl (meth) acrylate, pentadecafluorooctyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, 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, methoxy polyethylene glycol ( Meta) acrylate, ethoxy polyethylene glycol (meth) acrylate, butoxy polyethylene glycol (meth) acrylate, octoxy polyethylene glycol (meth) acrylate, lauroxy polyethylene glycol (meth) acrylate, stearoxy polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (Meta) Acrile 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 combination of two or more.

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 anionic polymerization method, when it is attempted to directly polymerize the (meth) acrylate monomer to the active end of the strongly nucleophilic styrenic polymer, there are cases where polymerization can not be performed due to nucleophilic attack on the carbonyl carbon. is there. Therefore, the in performing the polymerization of the A ¹ -A ² (meth) acrylate monomers using reactive modifiers, after adjusting the nucleophilic, it is performed to polymerize the (meth) acrylate monomer. B in the general formula (1) is a group derived from the reaction control agent. 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 anionic polymerization method is in the form of an A-B block in which one end of the polymer block A and one end of the polymer block B are linked via a linking group derived from a reaction modifier. It becomes a block polymer having a molecular structure.

(Mole ratio A: B of polymer block A and polymer block B)
In addition, in the block polymer P, when the polymer block A and the polymer block B are clearly separated, it is advantageous in the stability of the obtained aqueous pigment dispersion. The molar ratio A: B of the polymer block A to 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 A, the dispersion stability of the pigment and the discharge stability at the time of ink jet discharge tend to be inferior. On the other hand, when the ratio of B exceeds 500 with respect to 100 of A, the hydrophilicity of the polymer becomes too high, and when the recording medium is paper or the like, it easily penetrates into it, and the coloring property is lowered. Among others, the ratio is preferably A: B = 100: 10 to 100: 450.

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

(Acid number of block polymer P)
The acid value of the block polymer P is preferably 40 to 400 mg KOH / g, more preferably 40 to 300 mg KOH / g, and most preferably 40 to 190 mg KOH / g. If the acid value is less than 40 mg KOH / g, the dispersion stability of the pigment and the discharge stability at the time of ink jet discharge may not be sufficient. On the other hand, when the acid value is more than 400 mg KOH / g, the hydrophilicity of the polymer is increased and the polymer easily penetrates into the recording medium, so that the color developing property is lowered. If the acid value exceeds 190 mg KOH / g, the water resistance of the resulting ink may be affected in some cases.

  In addition, the acid value of the polymer in this invention was measured based on JIS test method K 0070-1992. Specifically, it was determined by dissolving 0.5 g of a sample in THF solvent and titrating with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

(Neutralization rate of block polymer P)
The neutralization ratio of 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 commonly used compounds can be used. For example, inorganic basic substances such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide Organic basic compounds such as ammonia, triethylamine, and alkanolamines can be used.

(Solubility of block polymer P in water)
The block polymer P used in the present invention has a solubility in water of 0.1 g / 100 ml or less, and forms fine particles in water when the neutralization ratio 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 block polymer P in water is defined as follows. That is, 0.5 g of a polymer whose particle diameter is adjusted to 250 μm to 90 μm using a sieve with openings of 250 μm and 90 μm is sealed in a bag made of 400 mesh wire mesh, dipped in 50 ml of water, and at 25 ° C. The mixture was gently stirred for 24 hours. After immersion for 24 hours, the polymer-encapsulated 400 mesh wire mesh was dried by drying for 2 hours in a dryer set at 110 ° C. The change in weight before and after immersion in water of a 400 mesh wire mesh enclosing a polymer was measured, and the solubility was calculated by the following equation.

  The solubility in water is preferably 0.03 g / 100 ml, and more preferably 0.01 g / 100 ml or less.

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

(Particles)
Further, in the present invention, it was judged as follows whether or not to form fine particles in water when the neutralization ratio of the anionic group by the basic compound was 100%.
(1) The acid value of the polymer is measured in advance by the acid value measurement method based on JIS test method K 0070-1992. Specifically, 0.5 g of the polymer is dissolved in a solvent of tetrahydrofuran (hereinafter sometimes referred to as THF), 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 a polymer to 50 ml of water, an aqueous solution of 0.1 mol / L potassium hydroxide only for neutralizing 100% of the obtained acid value is added to obtain 100% neutralization.
(3) The 100% neutralized solution was irradiated with ultrasonic waves in an ultrasonic cleaner (SSN Corporation ultrasonic cleaner US-102, 38 kHz self-excited transmission) for 2 hours at a temperature of 25 ° C. Leave for 24 hours at room temperature.
Dynamic light scattering type particle size distribution measuring device (dynamic light scattering type particle size measuring device “Microtrack” manufactured by Nikkiso Co., Ltd. after leaving for 24 hours, sampling the liquid in the deep part of 2 cm from the liquid surface The particle size distribution meter UPA-ST150 ") is used to confirm whether or not the particles are present by determining whether light scattering information can be obtained by the particle formation.

(Particle size of 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.
The narrower the particle size distribution of the fine particles, the better the dispersibility, but the wider particle size distribution does not prevent the implementation.
As for the particle size and particle size distribution, a dynamic light scattering particle size distribution measuring device (a dynamic light scattering particle size measuring device “Microtrac particle size distribution analyzer UPA-ST150 manufactured by Nikkiso Co., Ltd. It measured using ").

(Water-soluble organic solvent)
The water-soluble organic solvent used in the present invention may be any water-soluble organic solvent having a boiling point of 100 ° C. or higher and capable of dissolving the block polymer P. When used as a raw material for an ink jet recording ink, a water-soluble organic solvent which does not affect the ink properties and is preferably applied as an anti-drying agent for the ink is preferable, and has high boiling point, low volatility and high surface tension. And polyhydric alcohols such as glycols such as diethylene glycol and triethylene glycol are particularly preferable. Glycols are generally contained in the ink composition in many cases, and there is no problem if they remain in the final product.
(Hereinafter, a water-soluble organic solvent having a boiling point of 100 ° C. or more used in the present invention may be referred to as a water-soluble organic solvent Q.)

  Preferred water-soluble organic solvents Q include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, etc .; butanediol, pentanediol, hexanediol, and the like Diols such as diols; Glycol esters such as propylene glycol laurate; diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono Propyl ether, Glycol ethers such as propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, cellosolve including triethylene glycol monobutyl ether; sulfolane; lactones such as γ-butyrolactone; Lactams such as-(2-hydroxyethyl) pyrrolidone, 2-hydroxy pyrrolidone, N-methyl pyrrolidone; glycerin, ethylene oxide adduct of glycerin, alkylene oxide adduct of glycerin such as propylene oxide adduct of glycerin, etc. Other various solvents known as organic solvents can be mentioned. These water-soluble organic solvents can be used alone or in combination of two or more.

(Pigment)
The pigment used in the present invention is not particularly limited, and organic pigments or inorganic pigments generally used in aqueous inks for aqueous inkjet recording can be used. Moreover, either an untreated pigment or a 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 (CI pigment black 7) produced by a known method such as a contact method, a furnace method and a thermal method. Also, as organic pigments, azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments and the like), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines Pigments, thioindigo pigments, isoindolinone pigments, quinofurarone pigments and the like), dye chelates (for example, basic dye type chelates, acid dye type chelates and the like), nitro pigments, nitroso pigments, aniline black and the like can be used.

  If the said pigment is illustrated according to a color, for example, as a pigment used for black ink, the carbon black made from No. 2300, no. 2200 B, no. 900, no. 960, no. 980, no. 33, no. 40, No, 45, No. 45 L, no. 52, HCF88, MA7, MA8, MA100, etc., manufactured by Columbia Inc. Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700 etc., Cabot Corp. Regal 400R, Regal 330 R, Regal 660 R, Mogul L, Mogul 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 etc. are Degussa's Color Black FW1, FW2, FW2 V, FW18, FW200, S150, S150, S170, Printex 35, U , The same V, the same 1400U, Special Bla k 6, the 5, 4, 4A, NIPEX150, NIPEX160, NIPEX170, NIPEX180 and the like.

  Moreover, as a specific example of the pigment used for yellow ink, 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, 151, 151 154, 155, 174, 180, 185 and the like.

  In addition, specific examples of the pigment used for the 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.

  In addition, as specific examples of the pigment used for the cyan ink, C.I. I. Pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66 and the like.

  Further, specific examples of the pigment used in the white ink include sulfates of alkaline earth metals, carbonates, finely divided silicic acid, synthetic silicates, silicas such as calcium silicate, alumina, alumina hydrate, Titanium oxide, zinc oxide, talc, clay and the like can be mentioned. Moreover, the said inorganic white pigment may be surface-treated by various surface treatment methods.

(water)
Water used in the present invention is a dispersion medium of the finally obtained pigment. As water, pure water such as ion exchange water, ultrafiltered water, reverse osmosis water, distilled water or ultrapure water can be used.

(Method of producing aqueous pigment dispersion)
The method for producing an aqueous pigment dispersion according to the present invention comprises the steps 1 and 2 of kneading a block polymer P solution prepared by dissolving the block polymer P in a water-soluble organic solvent having a boiling point of 100 ° C. or more and a pigment to obtain a colored mixture. It is characterized in that the step 2 of adding and diluting water to the colored mixture in the step 1 is carried out in this order.

In the present invention, the aqueous pigment dispersion refers to an aqueous pigment dispersion in which the pigment before being inked is dispersed at a high concentration in water as a dispersion medium.
The pigment concentration of the aqueous pigment dispersion is usually adjusted to 10 to 50% by mass. When making an ink using this, according to the desired ink use and physical properties, it is necessary to add water or an additive appropriately, and only dilute it so that the pigment concentration will be 0.1 to 20 mass%. , Ink can be obtained.

There is no particular limitation on a method for obtaining 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, an apparatus for uniformly mixing and dispersing uniformly, for example, using a commonly used stirring apparatus The mixture of the block polymer P and the water-soluble organic solvent Q may be dispersed by stirring and dissolved. At that time, by stirring while heating, a more uniform solution can be obtained.
A uniform block polymer solution can also be obtained by solution-polymerizing the block polymer P and then substituting the polymerization solvent for the water-soluble organic solvent Q.

The concentration of the block polymer P solution was obtained by diluting the concentration of the solid content during kneading, the amount of the pigment described later to be incorporated into the finally obtained aqueous pigment dispersion, or the obtained aqueous pigment dispersion It is not particularly limited as long as it is determined in consideration of the balance of the amount of water-soluble organic solvent such as the wetting agent to be blended in the aqueous ink for ink jet recording, but includes 10 to 40% by mass. 15 to 35% by mass is more preferable because it can be produced.
On the other hand, the viscosity of the block polymer P solution is preferably 100 to 50,000 mPa · s, and more preferably 200 to 30,000 mPa · s.

(Step 1 Step of Obtaining Dispersion with Pigment)
The dispersion method of the step (1) is preferably a kneading method. The kneading method is a method of refining pigment particles by applying a strong shearing force to a mixture containing a pigment and a high solid concentration with a kneader, and an aqueous pigment dispersion having a high pigment concentration can be obtained, and It is an effective method to reduce coarse particles. As a kneader used for the kneading method, a roll mill, a Henschel mixer, a pressure kneader, an intensive mixer, a Banbury mixer, a planetary mixer, etc. can be used. On the other hand, the block polymer P solution used in the present invention can be used with no problem even in media mill dispersion methods etc. using media such as paint shaker, bead mill, sand mill, ball mill etc. other than kneader.

  There are no particular limitations on the order in which the block polymer P solution and the pigment are charged, and either one may be charged in turn or the entire amount may be simultaneously charged to start kneading, or each may be charged in small amounts. In order to give the mixture a strong shear force, which is an advantage of the kneading and dispersing method, it is preferable to knead the mixture in a state of high solid content ratio, and a higher shear force can be applied to the mixture.

In order to apply a higher shearing force, the solid content ratio containing the pigment and the block polymer P is preferably 30% by mass or more, and more preferably 40% by mass or more.
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, the content is preferably 30% by mass or more, more preferably 35% by mass or more, based on the total amount of the mixture.
Also, the content ratio of the pigment to the block polymer P is not particularly limited, but usually it is often performed in the range of 10 / 0.5 to 10/20 by mass ratio, and more preferably 10 / 0.5. It is 10/10.
The content ratio of the water-soluble organic solvent Q and the block polymer P is not particularly limited, but is preferably 30/10 or more, and most preferably in the range of 30/10 to 90/10. preferable.

  In the step 1, it is preferable to keep the amount of water as small as possible in order to promote adsorption of the block polymer P to the pigment and to obtain good dispersion characteristics. Even when water is added in step 2 described later, the amount of water is preferably 50% by mass or less, and more preferably 40% by mass or less based on the solid content of the block polymer.

  In the step 1, it is more preferable to knead the mixture at a temperature of 50 ° C. or more and less than 110 ° C., more preferably 60 ° C. or more and less than 100 ° C. When the temperature is less than 50 ° C., the particle size of the obtained aqueous pigment dispersion tends to be large, and the number of coarse particles tends to increase. On the other hand, at 110 ° C. or higher, the water used and the water-soluble organic solvent Q may evaporate, and while the state of the kneaded material changes, the block polymer is easily desorbed from the pigment and the dispersion tends to be unstable. Coarse particles may increase.

(Step 2 water dispersion)
An aqueous pigment dispersion containing a pigment and a block polymer P is obtained by the step of adding and diluting water to the kneaded product obtained in the step 1 (hereinafter referred to as step (2)).
The kneaded material may be added to water, but conversely, it is preferable to add water to the kneaded material in that 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 one time, or may be added in small portions and mixed. Also, dispersion is usually performed using a dispersing machine.
The disperser used in step 2 may be a known disperser, for example, a paint shaker, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, and the like using media. Examples include spike mills and agitator mills. Moreover, as a thing which does not use media, an ultrasonic homogenizer, a nanomizer, a dissolver, a disperser, a high speed impeller disperser etc. are mentioned. After the dispersion, the concentration may be adjusted with a water-soluble solvent as needed.

Depending on the type of the dispersing machine used, a water-soluble organic solvent Q is further added to the dispersion, if necessary, mixed, diluted, and treated with the dispersing machine before carrying out water dispersion with the dispersing machine. It is preferable to adjust the viscosity to a suitable value (hereinafter, this viscosity-adjusted product may be referred to as a viscosity-adjusted product). For example, when using a sand mill, it is preferable to perform dispersion by driving the sand mill after dilution to a solid content concentration of 10 to 40% by mass and adjusting to a viscosity of several tens to several hundreds of 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, according to the step 2, an aqueous pigment dispersion using water as a medium is formed by phase inversion emulsification or a similar mechanism thereof. By passing through the step (1) and the step (2) of the present application in this order, it is possible to obtain an aqueous pigment dispersion in which coarse particles are reduced.
In the aqueous pigment dispersion thus obtained, it is presumed that the pigment is stabilized by being contained or partially adsorbed in the block polymer P.

The block polymer P in the aqueous pigment dispersion obtained by the production method of the present invention preferably has an anionic group neutralized. The timing of the neutralization is not particularly limited, and may be neutralized with the basic compound when forming a block polymer P solution in which the block polymer P is dissolved in a water-soluble organic solvent having a boiling point of 100 ° C. or more in advance. In the step (1), the basic compound may be charged and neutralized simultaneously with the block polymer P solution and the pigment and may be neutralized while adding the basic compound simultaneously with water in the step (2). Also, neutralization may be appropriately incorporated into a plurality of steps.
At this time, the basic compound may be 100% pure, but it is preferable to use an aqueous solution because of the possibility of heat generation and the like.
On the other hand, as described above, it is preferable to minimize the amount of water as much as possible particularly in step 1. Therefore, when using an aqueous solution of a basic compound as a neutralizing agent, it is preferable to add in consideration of the amount of water. When neutralization is performed in step 1, it is preferable not to add other than water used for the aqueous solution of the basic compound.

In the present invention, the blending amounts of the respective raw materials are not particularly limited, but it is preferable to perform blending with the following blending ratio as a standard.
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.
Moreover, it is preferable to mix | blend 20-200 mass parts with respect to 100 mass parts of pigments, and, as for the water-soluble organic solvent Q, More preferably, it is 30-200 mass parts.
The basic compound is preferably used so that the neutralization ratio of the block polymer P is 20% to 200%, and more preferably 80% to 150%. . The neutralization rate at this time is calculated by the following equation as described above.

(Water-based ink for inkjet recording)
The aqueous pigment dispersion obtained by the present invention is diluted to a desired concentration to be used in the paint field for automobiles and building materials, printing ink fields such as offset ink, gravure ink, flexographic ink, silk screen ink, or for inkjet recording. It can be used in various applications such as aqueous ink field. Among them, since coarse particles are reduced, it can be particularly preferably used as an aqueous ink for inkjet recording.
When the aqueous pigment dispersion obtained in the present invention is applied to an aqueous ink for inkjet recording, water, a binder resin and the like are further added to obtain a desired physical property, if necessary, a wetting agent (drying inhibitor), It is prepared by adding a penetrant or other additives.
After adjustment of the ink, centrifugation or filtration 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 preventing drying is preferably 3 to 50% by mass.
The wetting agent to be used in the present invention is not particularly limited, but it is preferable to be one which is miscible with water and capable of preventing the clogging of the head of the ink jet printer. 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 Diols, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol, sulfolane; lactones such as γ-butyrolactone; N- (2-hydroxyethyl) pyrrolidone and the like And lactams; glycerin and derivatives thereof. Among them, it is safe to include propylene glycol and 1,3-butanediol, and effects excellent in ink drying property and ejection performance can be seen.

(Penetrant)
The penetrant is added for the purpose of improving the permeability to the 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 content of the penetrant 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 which can be added for this purpose is not particularly limited, and various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and the like can be mentioned. Among them, anionic surfactants and nonionic surfactants are preferred.

  As the anionic surfactant, for example, alkyl benzene sulfonate, alkyl phenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfuric acid ester salt of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether Sulfuric acid esters and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. As specific examples of these, dodecylbenzene sulfonate, isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfone , And the like salts.

  As a nonionic surfactant, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerine fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkylalkanolamide, 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 Alkylolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, polyethylene glycol polypropylene glycol block copolymer are preferred. Among them, those having an HLB in the range of 7 to 20 are preferable because of their excellent solubility stability.

  Other surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluoroalkyl surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates and oxyethylene perfluoroalkyl ethers And biosurfactants such as spicolisporic acid, rhamnolipid and lysolecithin can also be used.

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

If necessary, preservatives, viscosity modifiers, pH adjusters, chelating agents, plasticizers, antioxidants, UV absorbers and the like can be added.
The water-soluble organic solvent Q used in the step 1 includes, for example, one that functions as a wetting agent or a penetrant. When the water-soluble organic solvent Q having such a function is used in the step 1, it is preferable to add it while adjusting the amount.

  The amount of pigment occupied in the aqueous ink for inkjet recording is preferably 0.1 to 20% by mass in order to secure the necessity of obtaining a sufficient image density and the dispersion stability of the pigment in the ink.

(recoding media)
The recording medium of the aqueous ink for ink jet recording is not particularly limited, and an absorptive recording medium such as copy paper (PPC paper) generally used in a copying machine, a recording medium having an ink absorption layer, an ink There may be a non-water-absorptive recording medium having no absorbability, a poorly water-absorptive recording medium having a low water-absorptivity of ink, and the like. The aqueous ink for ink jet recording of the present invention is also characterized in that the color developability is good when recorded on a recording medium having an absorbing layer, a non-water absorbing recording medium, and a non-absorbent recording medium.

  Examples of the absorptive recording medium include, for example, plain paper, cloth, cardboard, wood and the like. Further, as an example of a recording medium having an absorption layer, paper for inkjet use, etc. may be mentioned. As a specific example of this, for example, pictrico pro photo paper etc. made by Pictorico Co., Ltd. may be mentioned.

  As an example of the non-water-absorptive recording medium having no ink absorbency, for example, those used for packaging materials for food can be used, and known plastic films can be used. Specific examples thereof include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polyamide-based films such as nylon, polystyrene film, polyvinyl alcohol film, polyvinyl chloride film, polycarbonate film, polyacrylonitrile film, Polylactic acid film etc. are mentioned. In particular, polyester films, polyolefin films and polyamide-based films are preferable, and polyethylene terephthalate, polypropylene and nylon are more preferable. The film may be the above-mentioned film coated with polyvinylidene chloride or the like for imparting a barrier property, or, if necessary, a film laminated with a deposited layer of a metal such as aluminum or a metal oxide such as silica or alumina. May be

The plastic film may be an unstretched film, or may be uniaxially or biaxially stretched. Furthermore, although the surface of the film may be untreated, those subjected to various treatments such as corona discharge treatment, ozone treatment, low temperature plasma treatment, flame treatment, glow discharge treatment, etc. for improving adhesiveness are preferable.
The film thickness of the plastic film is appropriately changed according to the application, but for example, in the case of a soft packaging application, the film thickness is 10 μm to 100 μm as having flexibility, durability, and curl resistance. Is preferred. More preferably, it is 10 micrometers-30 micrometers. As this specific example, Pylen (registered trademark) of Toyobo Co., Ltd. and the like can be mentioned.

  As a recording medium having low water absorbency and low absorbency of ink, art paper such as printing paper, coated paper, lightweight coated paper, finely coated paper, etc. can be used. These low absorbency recording media are obtained by applying a coating material to the surface of cellulose-based generally non-surface-treated high-quality paper, neutral paper, etc. and providing a coating layer, and Oji Paper Co., Ltd. Fine coated paper such as OK Everlight Coat manufactured by Nippon Paper Industries Co., Ltd. and Aurora S manufactured by Nippon Paper Industries Co., Ltd. OK Coat L manufactured by Oji Paper Co., Ltd. Aurora L manufactured by Nippon Paper Industries Co., Ltd. Etc., “OK Top Coat +” manufactured by Oji Paper Co., Ltd., and “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd. (A2, B2), Oji Paper Co., Ltd. Art paper (A1), such as "OK Kinto +" manufactured by Mitsubishi Paper Industries Co., Ltd. and "Tokubishi Art" manufactured by Mitsubishi Paper Industries, Ltd., etc. may be mentioned.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by the following examples as long as the gist thereof is not exceeded. In the following examples, "parts" and "%" are based on mass unless otherwise noted.

(Example of synthesis of block polymer P)
Synthesis Example 1
1. n-Butyllithium (BuLi) as a polymerization initiator and styrene (St) as a first monomer are introduced from the tube reactors P1 and P2 in FIG. 1 into the T-shaped micromixer M1 in FIG. The polymer was allowed to form.
Next, the obtained polymer is transferred to the T-shaped micro mixer M2 in FIG. 1 through the tube reactor R1 in FIG. 1, and the growth end of the polymer is introduced from the tube reactor P3 in FIG. Trapped with 1,1-diphenylethylene (DPE)).
Then, the polymer obtained by introducing methacrylic acid tert-butyl ester (t-BMA) as a second monomer from the tube reactor P4 shown in FIG. 1 into the T-shaped micromixer M3 and moving it through the tube reactor R2 in FIG. And a continuous living anionic polymerization reaction. The reaction was then quenched with methanol to produce a block polymer (PA-1).

  At this time, the reaction temperature was set to 24 ° C. by immersing the entire microreactor in a constant temperature bath. In addition, the monomers and reaction modifiers introduced into the microreactor are dissolved in tetrahydrofuran (THF), and BuLi is a commercially available 2.6 M hexane solution diluted with hexane, and the block polymer (PA- The molar ratio of 1) was adjusted as follows.

Molar ratio of block polymer (PA-1) polymerization initiator / first monomer / reaction regulator / second monomer = 1.0 / 13.5 / 1.0 / 7.5

  The obtained block polymer (PA-1) was treated with a cation exchange resin to hydrolyze the t-butoxycarbonyl group of the t-BMA block to regenerate a carboxyl group. The reaction solution was distilled off under reduced pressure, and the obtained solid was pulverized to obtain a powder of polymer (P-1) as block polymer P.

  The number average molecular weight, acid value, solubility in water, presence or absence of fine particles at a neutralization ratio of 100%, average particle diameter (nm) and surface tension (mN / m) of the obtained block polymer P are described in the table below. It was shown to.

(Composition examples 2 to 6)
Polymers (P-2), (P-6), (P-7), (P-9), (P-9) and (P-12) were prepared by adjusting the kind of monomer and the introduction amount in the same manner as in Synthesis Example 1. Manufactured.

Synthesis Example 7
BuLi as a polymerization initiator and St as a first monomer were introduced from the tube reactors P1 and P2 in FIG. 1 into the T-shaped micromixer M1 in FIG. 1, and living anionic polymerization was performed to form a polymer.
Next, the obtained polymer is transferred to the T-shaped micro mixer M2 in FIG. 1 through the tube reactor R1 in FIG. 1, and the growth end of the polymer is introduced from the tube reactor P3 in FIG. Trapped by α-methylstyrene (α-MeSt)).
Then, t-BMA as a second monomer is introduced from the tube reactor P4 shown in FIG. 1 into the T-shaped micro mixer M3, and the polymer transferred through the tube reactor R2 in FIG. 1 and continuous living anionic polymerization The reaction was done. The reaction was then quenched with methanol to produce a block polymer (PA-13).

  At this time, the reaction temperature was set to 24 ° C. by immersing the entire microreactor in a constant temperature bath. In addition, the monomers and reaction modifiers introduced into the microreactor are dissolved with THF, and BuLi dilutes a commercially available 2.6 M hexane solution with hexane, and the dilution concentration and introduction rate of the block polymer (PA-13) The molar ratio was adjusted as follows.

Mol ratio of block polymer (PA-13) Polymerization initiator / first monomer / reaction regulator / second monomer = 1.0 / 12.0 / 1.3 / 8.1

  The block polymer (PA-13) obtained is hydrolyzed by treatment with a cation exchange resin, the reaction solution is distilled off under reduced pressure, and the obtained solid is pulverized to obtain a polymer (P-13). Of the powder.

Synthesis Example 8
In the same manner as in Synthesis Example 7, the type of monomer, the introduction amount, and the like were adjusted to produce a polymer (P-14).

Comparative Synthesis Example 1 Synthesis Example of Polymer (PH-1) for Comparative Example
(Method of adjusting random polymer)
One hundred parts of methyl ethyl ketone were charged into a reaction container having a stirrer, a dropping device, and a refluxing device, and the inside of the reaction container was purged with nitrogen while stirring. After keeping the inside of the reaction vessel in a nitrogen atmosphere and heating it to reflux state of methyl ethyl ketone, from a dropping device, 74 parts of St, 11 parts of acrylic acid, 15 parts of methacrylic acid and a polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd./"V- 75 ") 8 parts of the mixture was dropped over 2 hours. The temperature of the reaction system was maintained at 80 ° C. during the dropping.
After completion of the addition, the reaction was continued at the same temperature for another 25 hours. In the middle of the reaction, a polymerization initiator was appropriately added while confirming the consumption of the raw materials. After completion of the reaction, methyl ethyl ketone was distilled off under reduced pressure, and the obtained solid was pulverized to obtain a powder of polymer (PH-1).
The number average molecular weight of the polymer (PH-1) was 5,255, the weight average molecular weight was 9,000, and the acid value was 185 mg KOH / g.

(Method of measuring physical property value of polymer)
The physical property values of the obtained polymers were measured as follows.

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

Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were used in series connection.
"TSKgel G5000" (7.8 mm ID × 30 cm) × 1 "TSK gel G 4000" (7.8 mm ID × 30 cm) × 1 "TSK gel G 3000" (7.8 mm ID × 30 cm) × 1 This "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 volume: 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)
Tosoh Corporation "TSKgel standard polystyrene A-500"
Tosoh Corporation "TSKgel standard polystyrene A-1000"
Tosoh Corporation "TSKgel standard polystyrene A-2500"
Tosoh Corporation "TSKgel standard polystyrene A-5000"
Tosoh Corporation "TSKgel standard polystyrene F-1"
Tosoh Corporation "TSKgel standard polystyrene F-2"
Tosoh Corporation "TSKgel standard polystyrene F-4"
Tosoh Corporation "TSKgel standard polystyrene F-10"
Tosoh Corporation "TSKgel standard polystyrene F-20"
Tosoh Corporation "TSKgel standard polystyrene F-40"
Tosoh Corporation "TSKgel standard polystyrene F-80"
Tosoh Corporation "TSKgel standard polystyrene F-128"
Tosoh Corporation "TSKgel standard polystyrene F-288"
Tosoh Corporation "TSKgel standard polystyrene F-550"

(Method of measuring acid number)
It measured based on JIS test method K 0070-1992. 0.5 g of a sample was dissolved in THF solvent, and it was determined by titration with 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

(Method of measuring solubility in water)
0.5 g of polymer whose particle size is adjusted to 250 μm to 90 μm using a sieve with openings of 250 μm and 90 μm is sealed in a bag processed with 400 mesh wire mesh, immersed in 50 ml of water, and at a temperature of 25 ° C. 24 Stir gently for an hour. After immersion for 24 hours, the polymer-encapsulated 400 mesh wire mesh was dried by drying for 2 hours in a dryer set at 110 ° C. The change in weight before and after immersion in water of a 400 mesh wire mesh enclosing a polymer was measured, and the solubility was calculated by the following equation.

(Method of judging formation of fine particles in water and measuring method of average particle diameter (nm))
(1) The acid value of the polymer is determined according to the method for measuring the acid value.
(2) To 50 ml of water, after adding 1 g of a polymer, add a 0.1 mol / L aqueous potassium hydroxide solution that only neutralizes 100% of the acid value of the polymer obtained in (1) above, and neutralize 100%. I assume.
(3) 100% neutralized solution is dispersed at a temperature of 25 ° C. for 2 hours in an ultrasonic cleaner (SSN Corporation ultrasonic cleaner US-102, 38 kHz self-excited transmission) and dispersion Allow to stand at room temperature for 24 hours.
After leaving for 24 hours, use the dynamic light scattering particle sizer “Microtrack particle size distribution analyzer UPA-ST150” manufactured by Nikkiso Co., Ltd. Whether or not the fine particles were present was confirmed by determining whether light scattering information due to formation could be obtained.
At the same time, the average particle size was measured.

(Method of measuring surface tension)
The same sample solution as the sample solution obtained by the method for determining the formation of fine particles in water was taken as a value measured using a Wilhelmy surface tension meter.

  The raw material of the polymer obtained by the said synthesis example, reaction conditions, and physical-property value are shown in the table | surface.

In Tables 2 and 3,
BuLi represents normal butyl lithium,
St represents styrene,
DPE stands for 1,1-diphenylethylene,
αMeSt represents α-methylstyrene,
tBMA represents methacrylic acid tert-butyl ester,
nBMA represents methacrylic acid n-butyl ester.

(Example: Method of producing aqueous pigment dispersion)
The composition of Example 1 will be described as an example.
150 parts of triethylene glycol (boiling point 285 ° C.) was added to 30 parts of the crushed block polymer P-1 and stirred while heating at 70 ° C. with a water bath using a homomixer to dissolve the block polymer P-1 . Next, 12.8 parts of a 34% KOH aqueous solution as a basic compound was added so as to have a 100% neutralization ratio, to obtain a neutralized block polymer P-1 solution. The solid content concentration of the polymer P-1 at this time is 17.1%.
The total amount of the neutralized block polymer P-1 solution obtained above was charged into a 1.0 L intensive mixer (Nippon Eirich Co., Ltd.), and C.I. I. 150 parts of C.I. Pigment Red 122 was charged, and Step 1 was carried out for 60 minutes of kneading at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s to obtain a colored kneaded product.
Subsequently, in step 2, 657.2 parts of ion-exchanged water was gradually added to dilute the kneaded material in the intensive mixer container while continuing the stirring, and diluted to obtain an aqueous pigment dispersion having a pigment concentration of 15.0%.

  The aqueous pigment dispersions of Examples 2 to 13 were obtained in the same manner except that the amount of triethylene glycol, the pigment and the like were as described in Tables 5 and 6.

(Comparative example 1)
150 parts of isopropyl alcohol (boiling point 82.4 ° C.) was added to 30 parts of the crushed block polymer P-1 and stirred using a homomixer to dissolve the block polymer P-1. Next, 12.8 parts of a 34% KOH aqueous solution as a basic compound was added so as to have a 100% neutralization ratio, to obtain a neutralized block polymer P-1 solution. The solid content concentration of the polymer P-1 at this time is 17.1%.
The total amount of the neutralized block polymer P-1 solution obtained above was charged into a 1.0 L intensive mixer (Nippon Eirich Co., Ltd.), and C.I. I. 150 parts of C.I. Pigment Red 122 was charged, and Step 1 was carried out for 60 minutes of kneading at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s to obtain a colored kneaded product.
Subsequently, in step 2, 657.2 parts of ion-exchanged water was gradually added to dilute the kneaded material in the intensive mixer container while continuing the stirring, and diluted to obtain an aqueous pigment dispersion having a pigment concentration of 15.0%.

(Comparative example 2)
30 parts of crushed block polymer P-1, 150 parts of triethylene glycol (boiling point 285 ° C), 16.3 parts of an aqueous solution of 1.34 parts of a 34% KOH aqueous solution as a basic compound to a 100% neutralization ratio (1.0 L Charged to Nippon Eirich Co., Ltd.), and used C.I. I. 150 parts of C.I. Pigment Red 122 was charged, and Step 1 was carried out for 60 minutes of kneading at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s to obtain a colored kneaded product.
Subsequently, in step 2, while the stirring was continued, 653.7 parts of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container to dilute, and an aqueous pigment dispersion having a pigment concentration of 15.0% was obtained.

(Comparative example 3)
An aqueous pigment dispersion having a pigment concentration of 15.0% was obtained in the same manner as in Example 1 except that the polymer for comparison (PH-1) was used instead of the crushed block polymer P-1.

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

<Volume average particle size>
The produced aqueous pigment dispersion was diluted 5000 times, and measurement was performed using Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.). The measured value was an average of three measurements.
Judgment criteria (cyan pigment, yellow pigment)
○: volume average particle size is less than 100 nm
Δ: volume average particle size is 100 nm to less than 120 nm
X: volume average particle size is 120 nm or more
Judgment criteria (magenta pigment)
○: volume average particle size is less than 120 nm
Δ: volume average particle size is 120 nm to less than 140 nm
X: volume average particle diameter is 140 nm or more
Judgment criteria (black pigment)
○: volume average particle size is less than 90 nm
Δ: volume average particle size is 90 nm to less than 110 nm
X: volume average particle size is 110 nm or more

<Coarse particle number>
The prepared aqueous pigment dispersion was diluted 250 times, and measured with Accusizer 780 APS (manufactured by International Business). The number of coarse particles was converted to the number of particles per 1 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
○: Coarse particle number 50 × 10 ⁸ particles / ml or less
:: 50 to 100 × 10 ⁸ particles / ml of coarse particles of 0.5 μm or more
X: The number of coarse particles 100 × 10 ⁸ / ml or more of 0.5 um or more

<Dischargeability and color development>
In order to measure the ejection characteristics of the inkjet and the print density of the printed matter, the following aqueous ink for inkjet recording for evaluation was produced using the produced aqueous pigment dispersion.
The aqueous pigment dispersion was adjusted in accordance with the pigment concentration of the produced aqueous pigment dispersion in the following formulation in which the total amount is 100 parts so that the final pigment concentration is 5% by mass.
About 5 parts of an aqueous pigment dispersion (as a pigment component)
Triethylene glycol monobutyl ether 8 parts 2-pyrrolidone 8 parts Glycerin 3 parts Surfynol 440 (manufactured by Air Products Japan) 0.5 part Pure water remaining amount

Each of the produced aqueous inks for inkjet recording was tested using an inkjet printer (EM-930C manufactured by EPSON). After filling the cartridge with ink, the nozzle check pattern was printed. Furthermore, after printing with a print density setting of 100% in the area of 340 cm 2 of one A4 sheet on Pictrico Pro Photo Paper (manufactured by Pictorico) and OK Top Coat + (manufactured by Oji Paper Co., Ltd.) The nozzle check test pattern was printed again, the state of the nozzle before and after the test was compared, and it was checked whether the nozzle chipping increased or not, to evaluate the ejection property.
Judgment criteria
○: Nozzle missing number zero
:: Nozzle chipping increase less than 10%
X: Nozzle chipping increase 10% or more

In the table, the abbreviations are as follows.
PR122: C.I. I. Pigment red 122
PB 15: 3: C.I. I. Pigment blue 15: 3
PY 74: C.I. I. Pigment yellow 74
PB7: C.I. I. Pigment black 7
KOH: aqueous potassium hydroxide solution TEG: triethylene glycol PG: propylene glycol HD: hexanediol IPA: isopropyl alcohol pure water: ion exchanged water

As a result, as shown in Examples 1 to 12, all of the aqueous pigment dispersions obtained by the present invention have a small volume average particle diameter, a small number of coarse particles, and an ink having excellent dischargeability can be obtained. The
On the other hand, Comparative Example 1 is an example in which block polymer P is dissolved in a water-soluble organic solvent at 100 ° C. or less, and Comparative Example 2 is an example in which block polymer P is used without dissolving in a water-soluble organic solvent at 100 ° C. or less. Comparative Example 3 is an example in which a random polymer was used instead of the block polymer P, but in any case, the result was inferior in both the dispersibility, the number of coarse particles, and the ejection property.

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

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

Claims (4)

A method for producing an aqueous pigment dispersion comprising a block polymer P represented by the general formula (1) having a polymer block of a styrenic monomer, a water-soluble organic solvent, a pigment, and water,
A block polymer P solution in which the block polymer P is dissolved in a water-soluble organic solvent having a boiling point of 100 ° C. or higher and a pigment are kneaded to obtain a colored kneaded product, and water is added to the colored kneaded product of the process 1 perform step 2 dilution in this order state, and are less than 50 wt% water is relative to the block polymer P in the step 1, the anionic groups of the block polymer P after the step 2 medium with a basic compound A method of producing an aqueous pigment dispersion characterized by being mixed.

(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 heterocycle, A ³ represents a polymer block containing an anionic group, n Represents an integer of 1 to 5 and B represents an aromatic group or an alkyl group.) The water-soluble organic solvent having a boiling point of 100 ° C. or more is at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, butanediol, pentanediol and hexanediol. The method for producing an aqueous pigment dispersion according to claim 1, which is one polyhydric alcohol. Method for producing an aqueous pigment dispersion according to claim 1 or 2 wherein the colorant is an organic pigment. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 3 , wherein a solid content ratio containing the pigment and the block polymer P is 40% by mass or more.

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