JP2023149304A - Water-based pigment dispersion and water-based pigment ink for inkjet recording - Google Patents

Abstract

To provide an ink that can be dispersed by a simple process and has high storage stability.SOLUTION: A water-based ink includes a dispersion liquid (DS) including a pigment, a water-insoluble resin, an organic solvent (B) with a boiling point of lower than 120°C and a ClogP value of 1.0-5.0, and water. The content of the organic solvent (B) is more than 250 ppm and 5000 ppm or less.SELECTED DRAWING: None

Description

The purpose of the present invention is to provide a method for producing an aqueous pigment dispersion with excellent storage stability and an aqueous inkjet recording ink.

The recording method using an inkjet printer, which is one of the representative methods among various color recording methods, generates small droplets of ink and attaches them to various recording materials (paper, film, fabric, etc.) to record. It is something. This method has been rapidly expanding as a commercial printing method in recent years because the recording head and the recording material do not come into direct contact with each other, so it is quiet and generates little noise, and it is also easy to downsize and increase speed.
In recent years, pigment inks have been used in place of dye inks for water-based inks in order to improve light resistance, water resistance, and the like. Furthermore, as the movement to expand the range of media that can be applied to aqueous inkjet media with lower environmental impact is accelerating, low surface tension solvents are increasingly being added to inks to accommodate media that are difficult to wet. A low surface tension solvent destabilizes the dispersion state of the pigment dispersion, which causes aggregation, sedimentation, and viscosity increase in storage stability evaluation. Against this background, pigment inks are required to have higher storage stability in addition to conventional performances such as gloss, scratch resistance, and stable ejection properties. A method for producing pigment-based ink is, for example, by kneading and dispersing a resin that has been neutralized with a basic substance and a pigment, adding an acid to this to precipitate the resin on the surface of the pigment, and then neutralizing it again with a basic substance. A production method has been proposed in which the pigment is maintained in a fine state and redispersed in an aqueous medium. (Patent Document 1). However, this method requires complicated steps such as kneading with pigment and re-neutralization, and the cleaning work is also complicated. In addition, as a method for obtaining a pigment dispersion with higher dispersion and stability, a method has been reported in which pigments are encapsulated and encapsulated with a polymer having a crosslinked structure (Patent Document 2, Patent Document 3), but the method involves a crosslinking reaction, In the polymerization reaction, the pigment encapsulation process is complicated and operations are complicated, such as requiring high-temperature and high-pressure equipment. In addition, storage stability evaluation is not sufficient.

Japanese Patent Application Publication No. 9-31360 Japanese Patent Application Publication No. 11-140343 Japanese Patent Application Publication No. 2002-338859

The present invention was made in view of the current situation, and an object of the present invention is to provide an ink that can be dispersed by a simple process and has high storage stability.

As a result of extensive research to solve the above problems, the present inventors have discovered that pigments, water-insoluble resins, and organic solvents that have a boiling point of less than 120°C and a ClogP value of 1.0 to 5.0 (B) and a dispersion liquid (DS) containing water and having a content of the organic solvent (B) of more than 250 ppm and less than 5000 ppm. The present invention has been completed.

That is, the present invention relates to the following 1) to 7).
1)
A pigment, a water-insoluble resin, an organic solvent (B) having a boiling point of less than 120°C and a ClogP value of 1.0 to 5.0, and water, the content of the organic solvent (B) being: A water-based ink containing a dispersion (DS) of more than 250 ppm and less than 5000 ppm.
2)
The water-based ink according to 1), wherein the organic solvent (B) contains at least one selected from the group consisting of hexane, heptane, cyclohexane, and 3-methylpentane.
3)
The water-based ink according to 1) or 2), wherein the pigment contains carbon black.
4)
The water-based ink according to any one of 1) to 3), wherein the water-insoluble resin is a block polymer.
5)
The above-mentioned water-insoluble resin, an organic solvent (A) having a solubility in 100 parts by weight of water of 5 to 40 parts by mass at 20°C, the above-mentioned boiling point being less than 120°C, and a ClogP value of 1.0 to 5.0; An emulsion composition preparation step of preparing an emulsion composition containing a certain organic solvent (B), a neutralizing agent, and water;
a dispersion treatment step of dispersing a mixture of the emulsion composition and the pigment;
a step of distilling off part or all of the organic solvent (A) and the organic solvent (B) from the mixture after the dispersion treatment;
A method for producing a dispersion containing.
6)
The dispersion according to 5), wherein in the emulsion composition preparation step, the total amount b of the organic solvent (B) and the total amount p of the pigment satisfy the relationship 0.03≦b/p≦0.7. manufacturing method.
7)
The method for producing a dispersion according to 5) or 6), wherein the organic solvent (A) contains methyl ethyl ketone.

ADVANTAGE OF THE INVENTION According to the present invention, it was possible to provide an aqueous ink composition for inkjet printing that has high storage stability over a long period of time.

In this specification, "C.I." means "color index." In addition, in this specification, including Examples and the like, "%", "part", and "amount" are all expressed on a mass basis unless otherwise specified.
Further, in this specification, the terms "alkylene", "propylene", and "alkyl" are used to include both straight chain and branched chain structures, unless otherwise specified. In addition, if the value of mass % is written as a value with a decimal point, the value up to the second decimal place is valid, the value in the second decimal place is rounded off, and the value is written up to the first decimal place. .

The water-based ink contains a pigment, a water-insoluble resin, an organic solvent (B) having a boiling point of less than 120°C and a ClogP value of 1.0 to 5.0, and water, and the organic solvent (B) The dispersion liquid (DS) has a content of more than 250 ppm and less than 5000 ppm. Note that water-based ink may be abbreviated as ink in this specification.

[Dispersion liquid (DS)]
The ink contains the dispersion liquid (DS).

[Pigment]
Examples of the pigments include inorganic pigments, organic pigments, and extender pigments. These pigments can be used alone or in combination of two or more. Examples of inorganic pigments include carbon black, titanium oxide, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides. The pigment preferably contains carbon black, and more preferably consists of carbon black.
The above-mentioned carbon black is not particularly limited, but preferably has a BET specific surface area of 100 m ² /g or more, more preferably 150 m ² /g or more from the viewpoint of color development on plain paper and coated paper, and particularly preferably It is 180 m ² /g or more. Specific examples of the carbon black include thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. More specifically, Raven 2000, Raven 2350ULTRA, Raven 2500ULTRA, Raven 2800ULTRA, Raven 2900ULTRA, Raven 3000ULTRA, Raven 3500, Raven 5000ULTRA (all manufactured by Columbia Carbon), Monarch 700, Raven 880, Raven 900, Raven 1. 000, 1300 (manufactured by Cabot), Printex 75, 80, 85, 95, L6, Color Black S160S, S170, FW18, FW182, FW1, FW2, FW171, FW200, Examples include FW285, Special Black 5, 6, HIBLACK 50L, 600L, 890, 930L, 970LB, NIPex 90, 160IQ, 170IQ, 180IQ (manufactured by Orion Engineered Carbons), etc. .

The DBP oil absorption amount of the carbon black is not particularly limited, but it is preferably 40 to 150 mL/100 g, more preferably 70 mL/100 g or more from the viewpoint of color development on plain paper, and particularly preferably It is 90 or more. The above-mentioned DBP oil absorption amount indicates the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black in units of cm ³ , and the value can be obtained by measuring, for example, referring to JIS K 6221.

Examples of the organic pigment include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthoraquinone, and quinophthalone. Specific examples of organic pigments include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, Yellow such as 139, 150, 151, 154, 180, 185, 193, 199, 202, 213; C.I. I. Pigment Red 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, Red such as 254, 255, 257, 260, 264, 272; C.I. I. Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.; C.I. I. Pigment Violet 19, 23, 29, 37, 38, 50, etc.; C.I. I. Pigment Orange 13, 16, 68, 69, 71, 73, etc.; C.I. I. Pigment Green 7, 36, 54, etc.; C.I. I. Examples include pigments of various black colors such as Pigment Black 1 and the like.

Examples of the extender pigment include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. It is preferable that extender pigments are used in combination with other pigments.

[Water-insoluble resin]
The dispersion liquid (DS) contains a water-insoluble resin. The water-insoluble resin refers to a polymer whose dissolved amount is 10 g or less when the polymer is dried at 70° C. for 24 hours and dissolved in 100 g of water at 25° C. Moreover, it is preferable that the amount dissolved is 5 g or less, and more preferably 1 g or less.
Examples of the water-insoluble resin include styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; acrylic acid and its derivatives; maleic acid and its derivatives; itacon At least two monomers (preferably, Examples include copolymers, at least one of which is a hydrophilic monomer. Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, and (meth)acrylic acid ester-(meth)acrylic acid ester copolymer. Examples include acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleic acid copolymer.
Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic ester copolymer, (meth)acrylic ester-(meth)acrylic acid copolymer, polyethylene Glycol (meth)acrylate-(meth)acrylic acid copolymers are preferred; styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, (meth)acrylics Acid ester-(meth)acrylic acid copolymers are more preferred; (meth)acrylic ester-(meth)acrylic acid copolymers are even more preferred; methacrylic ester-methacrylic acid copolymers are particularly preferred.
In this specification, the term "(meth)acrylic" is used to include both "acrylic" and "methacrylic". The same applies to "(meth)acrylate" and the like.
Examples of the type of copolymer include block copolymers, random copolymers, graft copolymers, and/or salts thereof, and block copolymers are preferred. In addition, in this specification, a block copolymer may be described as a block polymer.
Water-insoluble resins can be synthesized or commercially available. Specific examples of commercially available products include styrene-acrylic copolymers such as Joncryl 62, 67, 68, 678, 611, 687, 690, and 819, all manufactured by Johnson Polymer; Movinyl S-100A ( Modified vinyl acetate copolymer manufactured by Hoechst Synthesis Co., Ltd.); Jurimer AT-210 (polyacrylic acid ester copolymer manufactured by Nippon Pure Chemical Industries, Ltd.), and the like.
As the copolymer obtained by synthesis, AB block polymer disclosed in International Publication No. 2013/115071 Gazette is preferably mentioned.

The weight average molecular weight of the water-insoluble resin is less than 50,000, preferably from 3,000 to less than 50,000, from the viewpoint of improving the storage stability and ejectability of the aqueous pigment dispersion and the durability of printed matter after printing. , more preferably 7,000 or more and less than 25,000. Further, the acid value of the resin as the dispersant is preferably 50 to 300 KOHmg/g, more preferably 60 to 275 KOHmg/g, particularly preferably 70 to 250 KOHmg/g.

The water-insoluble resin described above can be used either in a state mixed with a pigment; or in a state in which part or all of the surface of the pigment is coated with a resin as a dispersant. Moreover, both of these states can also be used together.

The water-insoluble resin has salt-forming groups. The salt-forming group refers to a carboxy group, a hydroxyl group, a sulfo group, a phosphoric acid group, and an amino group. The salt-forming group can be introduced into the water-insoluble resin by polymerizing a monomer mixture containing the salt-forming group-containing monomer.

[Organic solvent B]
The above-mentioned organic solvent B refers to a solvent having a boiling point of less than 120° C. and a ClogP value of 1.0 to 5.0. The organic solvent B is not particularly limited as long as it has a boiling point of less than 120°C and a ClogP value of 1.0 to 5.0, and aromatic hydrocarbon solvents that satisfy the conditions, Examples include aliphatic hydrocarbon solvents, halogenated aliphatic hydrocarbon solvents, and the like. Examples of the aromatic hydrocarbon solvent include o-xylene, toluene, and benzene. Examples of the aliphatic hydrocarbon solvent include heptane, hexane, 3-methylpentane, and cyclohexane. Examples of the halogenated aliphatic hydrocarbon solvent include chloroform, dichloromethane, and the like. The above organic solvent B can be used alone or in combination of two or more. As the organic solvent B, hexane, heptane, 3-methylpentane, and cyclohexane are preferable, and hexane is more preferable in consideration of safety and operability when distilling off the solvent in post-treatment.

The ClogP value of the organic solvent B is preferably 2.0 to 4.0 from the viewpoint of dispersion stability. Note that the ClogP value of organic solvent B is calculated using ChemBioDrawUltra 13.0 (manufactured by CambridgeSoft).

The content of the organic solvent B contained in the dispersant (DS) is 500 ppm or more and 5000 ppm or less, preferably in the range of 251 to 5000 ppm, more preferably in the range of 255 to 4000 ppm, and odor From the viewpoint of safety and safety, it is even more preferable that the content be 260 to 3000 ppm or less. By controlling the content of the organic solvent B contained in the dispersant (DS) to 500 ppm or more and 5000 ppm or less, it becomes possible to improve the storage stability of the dispersant (DS).

[water]
The dispersion liquid (DS) contains water. As water, water with a low content of impurities such as metal ions, ie, ion-exchanged water, distilled water, etc., is preferable. Such water can be prepared by known methods.

A known method can be used to prepare the dispersion liquid (DS). One example is the phase inversion emulsification method. That is, a resin as a dispersant is dissolved in an organic solvent such as methyl ethyl ketone, and an aqueous solution of a neutralizing agent, which will be described later, is added to prepare an emulsion. A pigment is added to the obtained emulsion and a dispersion process is performed. By distilling off the organic solvent and a portion of the water under reduced pressure from the liquid thus obtained, the desired dispersion liquid can be obtained.

The above emulsion can be prepared by mixing each component in any order, but it is possible to dissolve or disperse the water-insoluble resin in organic solvent A described below and then mix it with water and a neutralizing agent. , is preferable because a uniform emulsified composition can be obtained. Furthermore, since organic solvent B has low solubility in water, adding organic solvent B after preparing an emulsion by adding organic solvent A, a water-insoluble resin, and a neutralizing agent prevents precipitation of the water-insoluble resin. This is preferable because it can be suppressed.

Further, the dispersion treatment can be performed using, for example, a sand mill (bead mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, or the like. For example, when using a sand mill, beads with a particle diameter of about 0.01 mm to 1 mm can be used, and the dispersion process can be performed by appropriately setting the filling rate of the beads.
The dispersion obtained as described above can be subjected to operations such as filtration and/or centrifugation. By this operation, the particle diameters of the particles contained in the dispersion can be made uniform.
If foaming occurs during the preparation of the dispersion, a very small amount of a known antifoaming agent such as silicone-based or acetylene glycol-based antifoaming agents can be added.
Methods for preparing dispersions other than those mentioned above include acid precipitation method, interfacial polymerization method, in-situ polymerization method, in-liquid hardening film method, coacervation (phase separation) method, in-liquid drying method, melt dispersion cooling method, Examples include air suspension coating method and spray drying method. Among these, the phase inversion emulsification method, acid precipitation method, and interfacial polymerization method are preferred.

The average particle size (D50) of the pigment in the dispersion is usually 300 nm or less, preferably 30 to 280 nm, more preferably 40 to 270 nm, even more preferably 50 to 250 nm.
Similarly, D90 is usually 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less. The lower limit is preferably 100 nm or more.
Similarly, D10 is usually 10 nm or more, preferably 20 nm or more, more preferably 30 nm or more, and the upper limit is 100 nm or less. Particle size can be measured using laser light scattering.

[Neutralizer]
It is preferable that some or all of the salt-forming groups possessed by the water-insoluble resin are neutralized with a neutralizing agent. As a neutralizing agent, an acid or a base can be used depending on the type of salt-forming group. Examples of acids include inorganic salts such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid, and polyethylene glycolic acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, and potassium hydroxide. Although there is no particular limitation on the degree of neutralization, it is preferable to adjust the dispersion liquid (DS) so that the liquid property is neutral, for example, the pH is 4.5 to 10.

[Organic solvent A]
Examples of the organic solvent A include organic solvents other than the organic solvent B that have a solubility in 100 parts by weight of water of 5 to 40 parts by weight at 20°C, and have a solubility of 10 to 30 parts by weight at 20°C. Parts by weight are preferred.

Examples of the organic solvent A include alcohol solvents, ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, halogenated aliphatic hydrocarbon solvents, etc. . For example, alcoholic solvents include 1-butanol, 2-butanol, and the like. Examples of ketone solvents include methyl ethyl ketone. Examples of ester solvents include ethyl acetate. Examples of the ether solvent include diethyl ether. These organic solvents can be used alone or in combination of two or more. Among the organic solvents A, methyl ethyl ketone is preferable in consideration of its safety and operability when removing the solvent in post-treatment.

The ink may contain other additives in addition to the dispersant (DS). Note that the above ink is preferably prepared by preparing the above dispersion (DS) containing a pigment and a water-insoluble resin, and then mixing it with other components.

Examples of the other components include a binder resin, a water-soluble organic solvent, a surfactant, an antifungal agent, an antibacterial agent, a pH adjuster, an antirust agent, an antifoaming agent, and the like. These may be used alone or in combination of two or more.

[Binder resin]
The binder resin preferably includes one or more selected from polymers and waxes.
Examples of the polymer include urethane-based, polyester, acrylic-based, vinyl acetate-based, vinyl chloride-based, styrene-acrylic-based, acrylic-silicon-based, and styrene-butadiene-based polymers, or emulsions containing the same. Among these, preferred are urethane-based, acrylic-based, and styrene-butadiene-based polymers, and acrylic-based polymers are more preferred.
The polymer can be synthesized or purchased commercially. When synthesizing a polymer, for example, polymers disclosed in International Publication No. 2015/147192 Gazette and the like are preferred.
Commercially available products include, for example, Superflex 126, 130, 150, 170, 210, 420, 470, 820, 830, 890 (urethane resin emulsion manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW- 178, HW-163, HW-171, AP-20, AP-30, WLS-201, WLS-210 (urethane resin emulsion manufactured by DIC Corporation); 0569, 0850Z, 2108 (styrene resin manufactured by JSR Corporation) butadiene resin emulsion); AE980, AE981A, AE982, AE986B, AE104 (acrylic resin emulsion manufactured by Etec Co., Ltd.), NeoCryl A-1105, A-1125, A-1127 (acrylic resin emulsion manufactured by Kusumoto Chemical Co., Ltd.) etc.

The wax is preferably a wax emulsion, more preferably an aqueous wax emulsion. As the wax, natural wax and synthetic wax can be used.
Natural waxes include petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montan wax; vegetable-based waxes such as carnauba wax and candelia wax; and animal and plant-based waxes such as beeswax and lanolin. Examples include emulsions in which wax is dispersed in an aqueous medium.

Examples of synthetic waxes include polyalkylene waxes (preferably polyC2-C4 alkylene waxes), oxidized polyalkylene waxes (preferably oxidized polyC2-C4 alkylene waxes), and paraffin waxes. Among the above waxes, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred, and oxidized polyethylene wax is more preferred.
Further, the average particle size of the wax is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

Commercially available wax emulsions include, for example, CERAFLOUR 925, 929, 950, 991; AQUACER 498, 515, 526, 531, 537, 539, 552, 1547; AQUAMAT 208, 263, 272; MINERPOL manufactured by BYK Chemie Japan; 221 etc.; Mitsui Hywax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505 etc. manufactured by Mitsui Chemicals; KUE-100, 11 manufactured by Sanyo Chemical Co., Ltd., HYTEC E-6500 manufactured by Toho Chemical Co., Ltd. , 9015, 6400, etc.

The total content of the binder resin with respect to the total mass of the ink is 0.6% to 6.0% from the viewpoint of the fixing property of the ink to paper, the ejection property of the ink, and the storage stability of the ink. is preferable, and more preferably 1.0% to 5%.

[Water-soluble organic solvent]
Water-soluble organic solvents are not particularly limited, but include, for example, C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, or tertiary-butanol; N,N-dimethylformamide or N,N- Carboxylic acid amides such as dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone or N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexane Cyclic ureas such as hydropyrimid-2-one; ketones, keto alcohols or carbonates such as acetone, 2-methyl-2-hydroxypentan-4-one and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol , diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably mono-, oligo- or polyalkylene glycols or thioglycols having C2-C6 alkylene units, such as polypropylene glycol, thiodiglycol or dithiodiglycol (molecular weight 400, 800, 1540 or more); C3-C9 polyols (triols) such as 1,2,6-triol and trimethylolpropane; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, prolene glycol monobutyl ether, dipropylene glycol monomethyl ether, etc. Glycol ethers (preferably selected from the group consisting of C3-C10 mono-, di- or triethylene glycol ethers and C4-C13 mono-, di- or tripropylene glycol ethers); 1,2-pentanediol, 1 , 5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 2,4-diethyl-1, C5-C9 alkanediols such as 5-pentanediol; γ-butyrolactone or dimethyl sulfoxide; and the like.

[Surfactant]
Examples of the surfactant include anionic, nonionic, silicone-based, and fluorine-based surfactants. Among these, silicon-based and fluorine-based surfactants are preferred, and silicon-based surfactants are more preferred from the viewpoint of safety to living organisms and the environment.

Examples of anionic surfactants include alkyl sulfocarboxylate, α-olefin sulfonate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether sulfate, N-acylamino acid or its salt, N-acylmethyl taurate, Alkyl sulfate polyoxyalkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, alkyl type phosphate ester, alkylaryl sulfone Examples include acid salts, diethyl sulfosuccinate, diethylhexyl sulfosuccinate, dioctyl sulfosuccinate, and the like.

Examples of nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene diphenyl ether. Ethers such as styrenated phenyl ethers (e.g. Emulgen A-60, A-90, A-500 manufactured by Kao Corporation); polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan mono Ester systems such as stearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate; 2,4,7,9-tetramethyl-5-decyne-4,7-diol , 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, and other acetylene glycol (alcohol) systems; polyglycol ether systems, and the like. These commercially available products include, for example, Surfynol 104, 104PG50, 82, 420, 440, 465, 485, Olfin STG, manufactured by Nissin Chemical Co., Ltd.; Emulgen A-60, A-90, A- manufactured by Kao Corporation. 500 etc. are mentioned.

Examples of the silicone surfactant include polyether-modified siloxane, polyether-modified polydimethylsiloxane, and the like. Examples include Dynor 960, 980 manufactured by Air Products; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, SAG010 manufactured by Nissin Chemical Co., Ltd.; and BYK Additives & Instruments. Made by BYK -345, 347, 348, 349, 3455, LP-X23288, LP-X23289, LP-X23347; TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, 2 manufactured by Evonic Tego Chemie 80 etc. were listed It will be done.

Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and perfluoroalkyl ether groups in side chains. Examples include polyoxyalkylene ether polymer compounds.

[Mildewproofing agent]
Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and its salts. .

[Preservative]
Examples of preservatives include organic sulfur-based, organic nitrogen-sulfur-based, organic halogen-based, haloarylsulfone-based, iodopropargyl-based, haloalkylthio-based, nitrile-based, pyridine-based, 8-oxyquinoline-based, and benzothiazole-based. , isothiazoline type, dithiol type, pyridine oxide type, nitropropane type, organotin type, phenol type, quaternary ammonium salt type, triazine type, thiazine type, anilide type, adamantane type, dithiocarbamate type, brominated indanone type, benzyl Examples include bromoacetate-based or inorganic salt-based compounds.
Specific examples of organic halogen compounds include sodium pentachlorophenol.
Specific examples of pyridine oxide compounds include sodium 2-pyridinethiol-1-oxide.
Examples of isothiazoline compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5 -Chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, 2-methyl-4-isothiazolin-3-one calcium chloride, etc. Can be mentioned.
Specific examples of other preservatives and fungicides include anhydrous sodium acetate, sodium sorbate, or sodium benzoate, manufactured by Lonza, trade names Proxel GXL (S), Proxel LV, Proxel XL-2 (S), and the like.

[pH adjuster]
Specific examples of pH adjusters include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonium hydroxide); water); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate, etc. Can be mentioned.

[anti-rust]
Specific examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like.

[Defoaming agent]
Examples of antifoaming agents include silicone-based, silica mineral oil-based, olefin-based, acetylene-based, and the like. Examples of commercially available antifoaming agents include Surfynol DF37, DF58, DF110D, DF220, MD-20, and Olefin SK-14, all manufactured by Shin-Etsu Chemical Co., Ltd.

The total amount of the pigment relative to the total amount of the ink is usually 1 to 20%, preferably 1.5 to 10%, and more preferably 2 to 8%. Here, in the specification and claims of the present application, "%" and "part" are expressed on a mass basis unless otherwise specified.
Further, the average particle size of the pigment is usually 50 nm to 250 nm, preferably 60 nm to 200 nm. In the specification and claims of the present application, the average particle size refers to the particle size at 50% of the integrated value in the particle size distribution determined by laser diffraction/scattering method.

The content of the organic solvent B contained in the ink described below containing the dispersion liquid (DS) is preferably 30 ppm or more and 3500 ppm or less, and from the viewpoint of odor and safety, it is preferably 50 ppm or more and 1500 ppm or less. More preferred.

The above-mentioned water-insoluble resin, an organic solvent (A) having a solubility in 100 parts by weight of water of 5 to 40 parts by mass at 20°C, the above-mentioned boiling point being less than 120°C, and a ClogP value of 1.0 to 5.0; An emulsion composition preparation step of preparing an emulsion composition containing a certain organic solvent (B), a neutralizing agent, and water;
a dispersion treatment step of dispersing a mixture of the emulsion composition and the pigment;
The present invention also includes a method for producing a dispersion liquid, which includes a step of distilling off part or all of the organic solvent (A) and the organic solvent (B) from the mixture after the dispersion treatment.

In the emulsion composition preparation step, when the total amount b of the organic solvent (B) and the total amount p of the pigment are b/p, from the viewpoint of improving storage stability, b/p is 0.03≦b/ It is preferable to satisfy the relationship p≦0.7, and more preferably to satisfy the relationship 0.04≦b/p≦0.6. Furthermore, if we consider the improvement of the dissolution stability of the water-insoluble resin, the ease of creating an emulsion, and the operability when distilling off the solvent in post-processing, we believe that 0.06≦b/p≦0.5 It is particularly preferable that the following relationship is satisfied.

An ink set containing two or more of the above inks is also included in the present invention. Further, an ink set including the above ink and another ink other than the above ink is also included in the present invention.
The above-mentioned other ink is not particularly limited as long as it has a different structure from the above-mentioned ink, but it is preferable that the other ink has a different hue from the above-mentioned ink.

When the above ink is used as an inkjet ink, an ink containing a small amount of inorganic impurities such as metal cation chloride (eg, sodium chloride) and sulfate (eg, sodium sulfate) is preferable. Such inorganic impurities are often contained in commercially available carbon black. A guideline for the content of inorganic impurities is approximately 1% or less based on the total amount of carbon black, and the ideal lower limit is below the detection limit of an analytical instrument, that is, 0%.
As a method for obtaining carbon black with few inorganic impurities, for example, a method using a reverse osmosis membrane; solid carbon black is suspended and stirred in a mixed solvent of C1-C4 alcohol such as methanol and water, and colored bodies are separated by filtration. Examples of desalting treatments include a method of drying and a method of exchanging and adsorbing inorganic impurities with an ion exchange resin;
Furthermore, when the above ink is used as an inkjet ink, it is preferable to microfiltrate the ink. When carrying out precision filtration, a membrane filter and/or glass filter paper can be used. The pore size of the filter used for precision filtration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

The above ink can be used in various printing fields. For example, it is suitable for applications such as writing, printing, information printing, and textile printing. In particular, it is preferable to use it for inkjet printing.

The present invention also includes printing media printed using the above ink or the above ink set, an ink media set of the above ink or the above ink set, and a printing medium, and a method for improving print density using the above ink or the above ink set. included.

The inkjet printing method is a method of printing by ejecting droplets of the ink according to a print signal and making them adhere to a print medium. There are no particular restrictions on the ink nozzles of the inkjet printer that eject ink, and they can be appropriately selected depending on the purpose.
The inkjet printing method improves image quality by ejecting a large number of inks with a low carbon black content in a small volume; Examples include a method of improving image quality using ink; and a method of improving the fixability of carbon black to print media by using a colorless transparent ink and an ink containing carbon black in combination. The above ink can also be used as an ink containing carbon black in these methods.

As the inkjet printing method, a known method can be used. Examples include a charge control method, a drop-on-demand method (also referred to as a pressure pulse method), an acoustic inkjet method, a thermal inkjet method, and the like.

The recording medium is not particularly limited as long as it is a substance that can be colored by the ink. Examples of the recording media include paper, film, fibers and cloth (cellulose, nylon, wool, etc.), leather, base materials for color filters, and the like.
These recording media can be roughly divided into those that have an ink-receiving layer and those that do not.

Examples of recording media having an ink-receiving layer include those having an ink-receiving layer provided on a base material such as paper, synthetic paper, or film. The ink-receiving layer can be formed, for example, by impregnating or coating the base material with a cationic polymer; or by using inorganic fine particles such as porous silica, alumina sol, or special ceramics together with a hydrophilic polymer such as polyvinyl alcohol or polyvinylpyrrolidone. It is provided by a method of coating the material surface.
Such recording media are usually called inkjet paper, inkjet film, glossy paper, or the like. Examples of typical commercially available products include: Professional Photo Paper, Super Photo Paper, Glossy Gold, and Matte Photo Paper manufactured by Canon Inc.; Product name of Seiko Epson Corporation: Photo Paper Crispia (high gloss) , photo paper (glossy), photo matte paper; trade name: Advanced Photo Paper (glossy), manufactured by Japan Hewlett-Packard Co., Ltd.; trade name: Gasai Photo Finish Pro, manufactured by Fuji Film Co., Ltd.; and the like.

Examples of recording media without an ink-receiving layer include various types of paper such as coated paper and art paper used in gravure printing, offset printing, etc.; cast coated paper used in label printing; and the like.

When printing on a print medium using the above inkjet printing method, for example, a container containing the above ink (referred to as an ink tank or the like) is loaded into a predetermined position of an inkjet printer, and printing is performed on the print medium using the above printing method.
The above inkjet printing method allows full color printing as an ink set of a plurality of inks selected from the above color inks. At that time, containers containing ink of each color are loaded into predetermined positions of the inkjet printer in the same manner as above, and printing is performed on print media using the printing method described above.

Only one type of all the above-mentioned components can be used. Moreover, it is also possible to select a plurality and a plurality of types as necessary and use them together.
Regarding all the contents described above, combinations of preferable items are more preferable, and combinations of more preferable items are still more preferable. The same applies to combinations of preferred and more preferred, combinations of more preferred and even more preferred, and the like.

The ink of the present invention has excellent viscosity stability, storage stability such as inhibition of coagulation and sedimentation, redispersibility, various scratch resistance, color development, and saturation, and images recorded with the ink of the present invention have excellent water resistance. , excellent in various fastness properties such as light resistance, heat resistance, and resistance to oxidizing gases (for example, ozone gas). Further, there is little coating unevenness during image formation, and the image forming property is also excellent.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples. In addition, all operations such as each synthesis reaction were performed under stirring unless otherwise specified.
In the examples, when it was necessary to quantify the pigment solid content in the dispersion, it was determined by the dry weight method using MS-70 manufactured by A & D Co., Ltd. The pigment solid content is a converted value obtained by calculating only the pigment solid content from the total amount of solid content.

[Preparation Example 1] Preparation of water-insoluble resin C.
A block copolymer (water-insoluble resin C) of Synthesis Example 3 was prepared by repeating Synthesis Example 3 of International Publication No. 2013/115071. The obtained block copolymer had an acid value of 105 mgKOH/g and an Mw of 25,000.
[Example 1]
4.8 parts of the water-insoluble resin C obtained in Preparation Example 1 was dissolved in 15 parts of methyl ethyl ketone, and a solution of 0.35 parts of sodium hydroxide dissolved in 50 parts of ion-exchanged water was added thereto. After adding 4.0 parts of hexane (normal hexane, manufactured by Junsei Kagaku Co., Ltd.), the mixture was stirred for 30 minutes to form an emulsion. NEROX600 (16 parts, manufactured by Orion Engineered Carbons) was added to the obtained emulsion, and dispersion beads were added, followed by dispersion treatment using a sand grinder at 1500 rpm for 15 hours to obtain a liquid. . To the obtained liquid, 120 parts of ion-exchanged water was added and the dispersion beads were separated by filtration to obtain a filtrate. From the obtained filtrate, methyl ethyl ketone, hexane, and a portion of water were distilled off under reduced pressure using an evaporator at a bath temperature of 55°C so that the pigment solid content was 12%, thereby obtaining Dispersion 1. The hexane content in Dispersion 1 was 610 ppm.
To the dispersion 1 obtained above, 1,2-hexanediol (5 parts), 1,2-propanediol (15 parts), BYK-349 (0.5 part, manufactured by BYK), texanol (1. 0 parts), AQUACER515 (1.0 parts, manufactured by BYK: solid content 35%), triethanolamine (0.3 parts), Proxel GXL (s) (0.05 parts, manufactured by Lonza), and water. The ink of Example 1 was obtained by stirring the liquid to make a total of 100 parts for 1 hour and filtering it with a 3 μm membrane filter (product number A300A047A, manufactured by Advantech). The pigment content in the ink was 5.0%.
[Example 2]
A dispersion liquid 2 having a pigment content of 12% was obtained in the same manner as in Example 1 except that NEROX605 (manufactured by Orion Engineered Carbons) was used instead of NEROX600. The hexane content in Dispersion 2 was 590 ppm. Further, an ink of Example 2 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 2.
[Example 3]
A dispersion liquid 3 having a pigment content of 12% was obtained in the same manner as in Example 1 except that #45L (manufactured by Mitsubishi Chemical Corporation) was used instead of NEROX600. The hexane content in Dispersion 3 was 420 ppm. Further, an ink of Example 3 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 3.
[Example 4]
A dispersion liquid 4 having a pigment content of 12% was obtained in the same manner as in Example 1 except that MA600 (manufactured by Mitsubishi Chemical Corporation) was used instead of NEROX600. The hexane content in Dispersion 4 was 850 ppm. Further, an ink of Example 4 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 4.
[Example 5]
A dispersion liquid 5 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600. The hexane content in Dispersion 5 was 1800 ppm. Further, an ink of Example 5 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 5.
[Example 6]
A dispersion liquid 6 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and heptane was used instead of hexane. The heptane content in Dispersion 6 was 1700 ppm. Further, an ink of Example 6 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 6.
[Example 7]
Dispersion 7 with a pigment content of 12% was prepared in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and 3-methylpentane was used instead of hexane. Obtained. The 3-methylpentane content in Dispersion 7 was 580 ppm. Further, an ink of Example 7 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 7.
[Example 8]
A dispersion liquid 8 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and cyclohexane was used instead of hexane. The cyclohexane content in Dispersion 8 was 1600 ppm. Further, an ink of Example 8 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 8.
[Example 9]
A dispersion liquid 9 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and toluene was used instead of hexane.
The toluene content in Dispersion 9 was 4100 ppm. Further, an ink of Example 9 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 9.
[Example 10]
A dispersion liquid 10 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and chloroform was used instead of hexane. The chloroform content in Dispersion 10 was 340 ppm. Further, an ink of Example 10 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 10.
[Example 11]
A dispersion liquid 11 having a pigment content of 12% was obtained in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and dichloromethane was used instead of hexane. The dichloromethane content in Dispersion 11 was 260 ppm. Further, an ink of Example 11 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 11.
[Example 12]
4.8 parts of Joncryl 819 (manufactured by Johnson Polymer Co., Ltd.: Mw 14500, acid value 75) (water-insoluble resin D) was dissolved in 15 parts of methyl ethyl ketone, and 0.26 parts of sodium hydroxide was added to 50 parts of ion-exchanged water. After adding a solution dissolved in , and further adding 4.0 parts of hexane, the mixture was stirred for 30 minutes to obtain an emulsion. Printex 80 (16 parts, manufactured by Orion Engineered Carbons) was added to the obtained emulsion, and dispersion beads were added, followed by dispersion treatment using a sand grinder at 1500 rpm for 15 hours to obtain a liquid. 120 parts of ion-exchanged water was added to the resulting solution, and the dispersion beads were separated by filtration to obtain a filtrate. Methyl ethyl ketone, hexane, and a portion of water were distilled off under reduced pressure from the obtained filtrate using an evaporator to obtain a dispersion liquid 12 having a pigment solid content of 12%. The hexane content in Dispersion 12 was 430 ppm. Further, an ink of Example 12 was obtained in the same manner as in Example 1 except that Dispersion 1 was changed to Dispersion 12.

The physical properties of the various carbon blacks used in Examples 1 to 12 above are listed in Table 1 below.

[Comparative Examples 1 to 5]
Each dispersion having a pigment content of 12% was obtained in the same manner as in Examples 1 to 5 except that the amount of hexane added was 0 parts. Each of the obtained dispersions was subjected to the same ink-forming operation as in Example 1 to obtain each ink of Comparative Examples 1 to 5 having a pigment content of 5.0%.
[Comparative example 6]
A dispersion having a pigment content of 12% was obtained in the same manner as in Example 2, except that the amount of hexane added was 0 parts. The resulting dispersion was subjected to the same ink-forming operation as in Example 1 to obtain an ink of Comparative Example 6 with a pigment content of 5.0%.
[Comparative Example 7]
A dispersion with a pigment content of 12% was prepared in the same manner as in Example 1 except that Printex 80 (manufactured by Orion Engineered Carbons) was used instead of NEROX 600 and 1,2-hexanediol was used instead of hexane. I got it. The resulting dispersion was subjected to the same ink-forming operation as in Example 1 to obtain an ink of Comparative Example 7 with a pigment content of 5.0%.

(Measurement of amount of organic solvent B in dispersion)
Quantitative analysis was performed using gas chromatography. A column "HP-FFAP (length 50 m, inner diameter 0.32 mm, film thickness 0.5 μm)" manufactured by Agilent was used in a gas chromatography analyzer "Agilent 7890B" manufactured by Agilent. The organic solvent B was quantified in terms of butyl acetate as an internal standard substance. Specifically, 300 mg of the sample was weighed into a sample bottle, butyl acetate (equivalent to about 0.05 wt%) and 1 mL of ethanol were added as internal standard substances, and after applying ultrasound for 20 minutes, it was measured under gas chromatography measurement conditions. The content of the solvent component was calculated from the obtained area value using a factor determined in advance. The conditions during the measurement were an injection port temperature of 270° C., a carrier gas of helium, a column linear velocity of 1.0 mL/min, and a split ratio of 50. Further, the column oven temperature was maintained at 50°C for 2 minutes, then raised to 150°C at a rate of 10°C per minute, and maintained at 150°C for 5 minutes. Moreover, the detector temperature was 250°C.

(Measurement of viscosity)
To measure the viscosity, an E-type viscometer TV-35L (manufactured by Toki Sangyo Co., Ltd.) was used.

[Storage stability test]
Regarding the viscosity immediately after ink preparation and after storage at 60° C. for 7 days, the rate of change in the measured value immediately after preparation of the ink and after storage for 7 days was calculated using the following formula.
The smaller the deviation between the measured values immediately after ink preparation and after 7 days of storage, the better the stability, indicating excellent storage stability.
Viscosity change rate = (measured value after 7 days storage - measured value immediately after preparation) / (measured value immediately after preparation) x 100%
Note that the hyphen in Table 3 indicates that the organic solvent (B) or a solvent other than the organic solvent (B) is not contained. Furthermore, the hyphen in "Residual amount of solvent B in dispersion (ppm)" in Comparative Example 7 indicates that no measurement was performed. Furthermore, in Table 3, the type of organic solvent B used in each example is indicated by "○".

(Storage stability evaluation)
A: Viscosity change rate is within ±4% B: Viscosity change rate is over ±4% and within 7% C: Viscosity change rate is over ±7% and within ±10% D: Viscosity change rate is ±10% exceed

It can be seen that the inks of Examples clearly have better storage stability than the inks of Comparative Examples 1 to 7. In particular, it can be seen that a water-based ink with high storage stability can be obtained even in the case of Example 5 in which carbon with high cohesiveness and relatively large specific surface area is used.

The aqueous dispersion of the present invention can be suitably used in aqueous inks for inkjet recording.

Claims (7)

A pigment, a water-insoluble resin, an organic solvent (B) having a boiling point of less than 120°C and a ClogP value of 1.0 to 5.0, and water, the content of the organic solvent (B) being: A water-based ink containing a dispersion (DS) of more than 250 ppm and less than 5000 ppm. The water-based ink according to claim 1, wherein the organic solvent (B) contains at least one selected from the group consisting of hexane, heptane, cyclohexane, and 3-methylpentane. The water-based ink according to claim 1 or 2, wherein the pigment contains carbon black. The water-based ink according to any one of claims 1 to 3, wherein the water-insoluble resin is a block polymer. The above-mentioned water-insoluble resin, an organic solvent (A) having a solubility in 100 parts by weight of water of 5 to 40 parts by mass at 20°C, the above-mentioned boiling point being less than 120°C, and a ClogP value of 1.0 to 5.0; An emulsion composition preparation step of preparing an emulsion composition containing a certain organic solvent (B), a neutralizing agent, and water;
a dispersion treatment step of dispersing a mixture of the emulsion composition and the pigment;
a step of distilling off part or all of the organic solvent (A) and the organic solvent (B) from the mixture after the dispersion treatment;
A method for producing a dispersion containing. The dispersion according to claim 5, wherein the total amount b of the organic solvent (B) and the total amount p of the pigment in the emulsion composition preparation step satisfy the relationship of 0.03≦b/p≦0.7. Method of manufacturing liquid. The method for producing a dispersion according to claim 5 or 6, wherein the organic solvent (A) contains methyl ethyl ketone.