JP2005036203A - Water-based ink for inkjet recording - Google Patents

Abstract

（式中、Ｒ_１は水素原子又は低級アルキル基、Ｒ_２は炭素数2〜18のアルキレン基又は水素原子がフェニル基で置換された炭素数２〜４のアルキレン基、ｎは２〜29の数、Ｒ_３は炭素数8〜30の直鎖又は分岐鎖のアルキル基を示す。）
で表されるモノマー、
（Ｂ）塩生成基含有モノマー、並びに
（Ｃ）疎水性モノマーを含有するモノマー混合物を重合させてなる水不溶性ビニルポリマーである、インクジェット記録用水分散体及び水系インク。
【選択図】 なしPROBLEM TO BE SOLVED: To provide a water-based ink for ink-jet recording having a high printing density and excellent storage stability.
An aqueous dispersion of water-insoluble vinyl polymer particles containing a colorant, comprising:
The water-insoluble vinyl polymer is represented by (A) general formula (I):
[Chemical 1]

Wherein R ₁ is a hydrogen atom or a lower alkyl group, R ₂ is an alkylene group having 2 to 18 carbon atoms or an alkylene group having 2 to 4 carbon atoms in which a hydrogen atom is substituted with a phenyl group, and n is 2 to 29. The number R ₃ represents a linear or branched alkyl group having 8 to 30 carbon atoms.)
A monomer represented by
An aqueous dispersion for inkjet recording and an aqueous ink, which are water-insoluble vinyl polymers obtained by polymerizing a monomer mixture containing (B) a salt-forming group-containing monomer and (C) a hydrophobic monomer.
[Selection figure] None

Description

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

  The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. According to this method, not only has the advantage that the device to be used is low noise and good operability, but also has the advantage that colorization is easy and plain paper can be used as a recording member. Widely used. In recent years, pigments or hydrophobic dye-based inks have been developed or used for inks used in inkjet printers in order to improve water resistance and light resistance.

  However, there is a problem that the pigment or the hydrophobic dye ink hardly remains on the surface of plain paper and the printing density is lowered. Further, when the content of the pigment or the hydrophobic dye is increased in the ink formulation in order to improve the printing density, there is a problem that the ink viscosity is increased and the ink dischargeability and storage stability are lowered.

In the pigment ink, in order to improve printing quality and printing density, a polymer containing a polyethylene glycol (meth) acrylate monomer and an α, β-ethylenically unsaturated carboxylic acid is added (Patent Document 1), dispersibility, In order to improve the storage stability, it has been proposed to add a polymer dispersant comprising a polyethylene glycol (meth) acrylate monomer or a poly (trimethylene glycol) (meth) acrylate monomer (Patent Document 2).
Patent Document 3 discloses a water-based ink for ink jet recording containing a vinyl polymer obtained by polymerizing a monomer mixture containing a monomer having a polyoxyalkylene chain and a pigment.

However, a polymer obtained by copolymerizing a terminal hydroxyl group (—OH) with a (meth) acrylate monomer containing an oxyethylene group or a hydrophilic monomer as a hydrophilic monomer has a high hydrophilicity, and thus easily penetrates into plain paper. In addition to the problem that the printing density is lowered, the ink viscosity is increased by the terminal hydroxyl group, so that it is difficult to ensure a stable ejection property.
JP-A-6-306317 JP 2000-144031 A WO00 / 39226

  In the present invention, by combining the monomer of the general formula (I), which is one of the constituent requirements, with other specific monomers, a high printing density can be obtained on plain paper, and further, storage stability, dispersion stability, and It is an object of the present invention to provide an aqueous dispersion for ink jet recording and an aqueous ink that have good scratch resistance and can reduce viscosity.

The present invention provides a water dispersion for ink jet recording containing a water dispersion of water-insoluble vinyl polymer particles containing a colorant as a means for solving the problem,
The water-insoluble vinyl polymer is represented by (A) general formula (I):

Wherein R ₁ is a hydrogen atom or a lower alkyl group, R ₂ is an alkylene group having 2 to 18 carbon atoms or an alkylene group having 2 to 4 carbon atoms in which a hydrogen atom is substituted with a phenyl group, and n is 2 to 30 The number R ₃ represents a linear or branched alkyl group having 8 to 30 carbon atoms.)
A monomer represented by
An aqueous dispersion for inkjet recording, which is a water-insoluble vinyl polymer obtained by polymerizing a monomer mixture containing (B) a salt-forming group-containing monomer and (C) a hydrophobic monomer, and an aqueous system for inkjet recording containing the aqueous dispersion Provide ink.

  In the water-based ink for ink jet recording of the present invention, “water-based” means that water accounts for the largest proportion in the solvent contained in the ink, and may be 100% water, which satisfies the above requirements. If it is a thing, the mixture of water and 1 type, or 2 or more types of organic solvent is also contained.

  The water-based ink for ink-jet recording of the present invention can obtain a high printing density on plain paper, further has good storage stability, dispersion stability, and scratch resistance, and can reduce viscosity.

  The aqueous dispersion for inkjet recording and the aqueous ink of the present invention contain an aqueous dispersion of water-insoluble vinyl polymer particles containing a colorant.

  The water-insoluble vinyl polymer particles containing a colorant are not particularly limited as long as the particles are formed of at least a colorant and a water-insoluble vinyl polymer. In which particles are encapsulated, particles in which a colorant is uniformly dispersed in a water-insoluble vinyl polymer, particles in which a colorant is encapsulated in a water-insoluble vinyl polymer, but a part of the colorant is exposed on the particle surface The form etc. are included.

<Colorant>
As the colorant, pigments and hydrophobic dyes are preferable from the viewpoint of water resistance. The pigment may be either an organic pigment or an inorganic pigment. If necessary, extender pigments can be used in combination. Examples of extender pigments include silica, calcium carbonate, and talc.

  Examples of the organic pigment include azo pigments, disazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.

  Specific examples of preferred organic pigments include CI Pigment Yellow 13, 17, 74, 83, 97, 109, 110, 120, 128, 139, 151, 154, 155, 174, 180 CI Pigment Red 48, 57: 1, 122, 146, 176, 184, 185, 188, 202, CI Pigment Violet 19, 23, CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16,60, CI Pigment Green 7, 36 etc.

  Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, metal chloride, and the like. Among these, carbon black is preferable. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

  The hydrophobic dye is not particularly limited as long as it can be contained in the polymer particles. Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable. The solubility of the hydrophobic dye is preferably 2 g / L or more with respect to the organic solvent used for dissolving the hydrophobic dye during the production of the aqueous dispersion, from the viewpoint of efficiently containing it in the polymer particles. g / L is more preferred.

  The oil-soluble dye is not particularly limited, but from the viewpoint of hydrophobicity, for example, CI Solvent Black 3, 7, 27, 29, 34, 45, and CI Solvent Yellow 14, 16, 29, 56, 82,83: 1; CI Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73; CI Solvent Violet 3; CI Solvent Blue 2, 4, 11, 44, 64, 70; CI solvent green 3, 7; CI solvent orange 2, etc. In addition, a dye obtained by solubilizing a water-soluble dye may be used.

  Among these, CI solvent yellow 29 and 30 as yellow, CI solvent blue 70 as cyan, CI solvent red 18 and 49 as magenta, CI solvent black 3, 7 and black dye of nigrosine as black are preferable. .

  Commercially available oil-soluble dyes include Nubian Black PC-0850, Oil Black HBB, Oil Black 860, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, OilRed 5B, Oil Scarlet 308, Vali Fast Blue 2606, Oil Blue BOS (above, product name, manufactured by Orient Chemical Co., Ltd.), Neopen Yellow 075, Neopen Mazenta SE1378, Neopen Blue 807, Neopen Blue FF4012, Neopen Cyan FF4238 (above, product name, manufactured by BASF) and the like.

<Water-insoluble vinyl polymer>
The water-insoluble vinyl polymer includes (A) a monomer represented by the general formula (I) [monomer (A)], (B) a basic group-containing monomer [monomer (B)], (C) a hydrophobic monomer [monomer ( It is obtained by polymerizing a monomer mixture containing C)]. These monomers may be mixed with the required amount of each monomer, if necessary, and other than the monomers (A), (B), and (C) within the scope of solving the problems of the present invention. These monomers can also be used.

  The monomer (A) is represented by the general formula (I). By using the monomer (A), there is an advantage that a water-based ink having a high printing density and excellent storage stability can be obtained. This is considered to be because the terminal alkyl group of the monomer (A) is likely to remain on the paper surface. As a result, excellent dispersion stability can be imparted to the water-based ink.

In the general formula (I), R ₁ is a hydrogen atom or a lower alkyl group, but a hydrogen atom or a methyl group is preferable from the viewpoint of polymerizability.

In the general formula (I), R ₂ is an alkylene group having 2 to 18 carbon atoms or an alkylene group having 2 to 4 carbon atoms in which a hydrogen atom is substituted with a phenyl group. And a butylene group are preferred.

n is the average number of added moles and is a number of 2 to 30, but from the viewpoint of printing density and storage stability, a number of 2 to 25 is preferable, a number of 2 to 15 is more preferable, and a number of 2 to 10 is preferable. Numbers are particularly preferred. The n R _{2 s} may be the same or different, and when they are different, either block addition or random addition may be used.

R ₃ is a linear or branched alkyl group having 8 to 30 carbon atoms, preferably an alkyl group having 8 to 22 carbon atoms from the viewpoint of high printing density and good storage stability, and has 8 to 18 carbon atoms. An alkyl group is more preferable, and an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl (lauryl) group, a tetradodecyl (myristyl) group, a hexadecyl (cetyl) group, and an octadecyl (stearyl) group are particularly preferable.

  Monomers (A) include octoxypolyethylene glycol mono (meth) acrylate, octoxypoly (ethylene glycol / propylene glycol) mono (meth) acrylate, octoxypoly (ethylene glycol / butylene glycol) mono (meth) acrylate, lauroxypolyethylene glycol ( And (meth) acrylate, lauroxy poly (ethylene glycol / propylene glycol) mono (meth) acrylate, stearoxy polyethylene glycol mono (meth) acrylate, stearoxy poly (ethylene glycol / propylene glycol) mono (meth) acrylate, and the like. These can be used alone or in admixture of two or more.

  The monomer (A) is obtained by a method in which an aliphatic alcohol terminal (—OH) is polymerized with an alkylene oxide and the polymerized terminal group (—OH) is etherified. Specific examples of the commercially available monomer (A) include Light Acrylate EA-C manufactured by Kyoeisha Chemical Co., Ltd., 50POEP-800B, PLE200, PSE-400 manufactured by Nippon Oil & Fats Co., Ltd.

  The content of the monomer (A) in the monomer mixture used for polymerizing the water-insoluble vinyl polymer is 1 to 45% by mass, preferably 2 to 35% by mass, and more preferably 2 from the viewpoint of printing density and ink viscosity. -30 mass%.

  As the monomer (B), an anionic monomer and a cationic monomer are preferable. Anionic monomers and cationic monomers can be used alone or in admixture of two or more.

  Examples of the anionic monomer include one or more selected from an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

  Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. These can be used alone or in admixture of two or more.

  Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. . These can be used alone or in admixture of two or more.

  Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate. These can be used alone or in admixture of two or more.

  Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoint of printing density and storage stability.

  Examples of the cationic monomer include one or more selected from unsaturated tertiary amine-containing vinyl monomers and unsaturated ammonium salt-containing vinyl monomers.

  Examples of unsaturated tertiary amine-containing monomers include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethyl. Examples include aminopropyl (meth) acrylamide, N, N-dimethylarylamine, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine, and the like. These can be used alone or in admixture of two or more.

  Examples of the unsaturated ammonium salt-containing monomer include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, N, N-dimethylaminopropyl (meth) acrylate quaternary product. And the like. These can be used alone or in admixture of two or more.

  Among the cationic monomers, N, N-dimethylaminoethyl (meth) acrylate, NN-dimethylaminopropyl (meth) acrylamide and vinyl pyrrolidone are preferable.

  The content of the monomer (B) in the monomer mixture used for polymerizing the water-insoluble vinyl polymer is 2 to 50% by mass, preferably 4 to 40% by mass, more preferably from the viewpoint of printing density and storage stability. 5 to 35% by mass.

  As the monomer (C), (C-1) general formula (II):

Wherein R ₄ is a hydrogen atom or a lower alkyl group, R ₅ is an alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, an alkylaryl group or an arylalkyl group, or a ring having 3 to 22 carbon atoms. Represents a hydrocarbon group.)
A monomer having an alkyl group, an aryl group or a cyclic hydrocarbon group represented by:
(C-2) General formula (III):

(In the formula, R ₆ represents a hydrogen atom or a lower alkyl group, and R ₇ represents an aromatic hydrocarbon group having 6 to 22 carbon atoms.)
One or more monomers selected from aromatic ring-containing monomers represented by (C-3) macromers and the like. These can be used alone or in admixture of two or more. The monomer (C) preferably contains at least one selected from (C-2) an aromatic ring-containing monomer and (C-3) a macromer from the viewpoint of printing density and scratch resistance. The lower alkyl group for R ₄ and R ₆ is preferably a methyl group.

  As the monomer having an alkyl group (C-1), methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) Amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, Examples include (meth) acrylates in which an ester moiety such as behenyl (meth) acrylate is an alkyl group having 1 to 22 carbon atoms. These can be used in combination of two or more.

  In addition, said (iso or tertiary) and (iso) mean both the case where these groups exist, and the case where it is not so, and when these groups do not exist, it shows normal. (Meth) acrylate means both methacrylate and acrylate. The same applies to the following.

  Examples of the monomer (C-1) having an aryl group include benzyl (meth) acrylate and phenoxyethyl (meth) acrylate. These can be used alone or in admixture of two or more.

  The monomer having a cyclic hydrocarbon group (C-1) is a monocyclic, bicyclic, or tricyclic or higher polycyclic (meth) acrylate having 3 or more carbon atoms. Specifically, as monocyclic (meth) acrylate having 3 or more carbon atoms, cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) Examples include acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate, and examples of bicyclic (meth) acrylate include isobornyl (meth) acrylate, norbornyl (meth) acrylate, and the like. Examples of the tricyclic (meth) acrylate include adamantyl (meth) acrylate. Among these, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate are preferable from the viewpoint of storage stability. These can be used in combination of two or more.

  The aromatic ring-containing monomer (C-2) was selected from styrene, vinylnaphthalene, α-methylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, and 1,1-diphenylethylene from the viewpoint of water resistance. One or more are preferred. Among these, one or more selected from styrene, α-methylstyrene, vinyltoluene, and vinylnaphthalene are more preferable from the viewpoint of print density and scratch resistance.

  The macromer (C-3) includes a macromer having a polymerizable functional group at one end and preferably having a number average molecular weight of 400 to 500,000, more preferably 600 to 12,000.

  Specific examples of the macromer include a styrene macromer having a polymerizable functional group at one end, a silicone macromer having a polymerizable functional group at one end, a methyl methacrylate macromer having a polymerizable functional group at one end, Examples thereof include a styrene / acrylonitrile macromer having a polymerizable functional group, a butyl acrylate macromer having a polymerizable functional group at one end, and an isobutyl methacrylate macromer having a polymerizable functional group at one end. In these, since formation of the water-insoluble vinyl polymer particle containing a coloring agent is easy, the styrenic macromer which has a polymerizable functional group in one terminal is preferable.

  Examples of the styrenic macromer having a polymerizable functional group at one end include styrene homopolymers having a polymerizable functional group at one end, and copolymers of styrene having a polymerizable functional group at one end and other monomers. Can be mentioned.

  Among the styrenic macromers having a polymerizable functional group at one end, a styrenic macromer having an acryloyloxy group or a methacryloyloxy group as a polymerizable functional group at one end is preferable from the viewpoint of dispersibility.

  Examples of commercially available styrenic macromers include AS-6 (S), AN-6 (S), HS-6 (S) manufactured by Toa Gosei Co., Ltd., and the like.

  The number average molecular weight of the macromer is measured using polystyrene as a standard substance by gel chromatography using 1 mmol / L dodecyldimethylamine-containing chloroform as a solvent.

  The content of the monomer (C) in the monomer mixture used for polymerizing the water-insoluble vinyl polymer is 10 to 88% by mass, preferably 20 to 85% by mass, more preferably from the viewpoint of storage stability and water resistance. 25 to 80% by mass.

  When the aromatic ring-containing monomer (C-2) is used as the monomer (C), the content of the aromatic ring-containing monomer in the monomer (C) is that in the monomer mixture used for polymerizing the water-insoluble vinyl polymer. The content of the aromatic ring-containing monomer is preferably 0.1 to 70% by mass, more preferably 1 to 60% by mass, and still more preferably 1 to 50% by mass, from the viewpoint of scratch resistance and ink viscosity.

  When the macromer of (C-3) is used as the monomer (C), the content of the macromer in the monomer (C) is preferably 0.1 to 40% by mass, more preferably from the viewpoint of water resistance and scratch resistance. Is 1 to 30% by mass, more preferably 1 to 20% by mass.

  The weight average molecular weight of the water-insoluble vinyl polymer (measured by the method described in the production example described later) is preferably 3,000 to 300,000, more preferably 5,000 to 200,000, from the viewpoints of printing density and ejection stability.

  The water-insoluble vinyl polymer is produced by polymerizing the monomers (A), (B), and (C) by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. . Among these polymerization methods, the solution polymerization method is preferable.

  The solvent used in the solution polymerization method is preferably a polar organic solvent. When the polar organic solvent is miscible with water, it can be used by mixing with water.

  Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, or a mixed solution of these with water is preferable. If necessary, toluene may be used.

  In the polymerization, a radical polymerization initiator can be used. As radical polymerization initiators, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2,2 Azo compounds such as' -azobis (2-methylbutyronitrile) and 1,1'-azobis (1-cyclohexanecarbonitrile) are preferred. Moreover, organic peroxides, such as t-butyl peroxy octoate, di-t-butyl peroxide, dibenzoyl oxide, can also be used.

  The amount of the polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.

  In the polymerization, a polymerization chain transfer agent may be further added. Specific examples of the polymerization chain transfer agent include mercaptans such as octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan and 2-mercaptoethanol; xanthogen disulfides such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide. ; Thiuram disulfides such as tetramethylthiuram disulfide and tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; hydrocarbons such as pentaphenylethane; acrolein, methacrolein, allyl alcohol, 2- Ethylhexyl thioglycolate, terbinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer, 9,10-dihydroanthracene, 1,4-di And unsaturated cyclic hydrocarbon compounds such as hydronaphthalene, indene and 1,4-cyclohexadiene; and unsaturated heterocyclic compounds such as 2,5-dihydrofuran. These polymerization chain transfer agents can be used alone or in admixture of two or more.

  Since the polymerization conditions of the monomer vary depending on the radical polymerization initiator, the monomer, the type of the solvent, and the like, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 85 ° C, and the polymerization time is preferably 2 to 24 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas.

  After completion of the polymerization reaction, the produced water-insoluble vinyl polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. The obtained water-insoluble vinyl polymer can be purified by repeating reprecipitation or removing unreacted monomers by membrane separation, chromatographic methods, extraction methods, and the like.

<Aqueous dispersion of water-insoluble vinyl polymer particles containing colorant and water-based ink>
An aqueous dispersion of water-insoluble vinyl polymer particles containing a hydrophobic dye as a colorant can be produced by a known emulsification method. For example, a water-insoluble vinyl polymer and a hydrophobic dye are dissolved in an organic solvent, a neutralizing agent and water are added as necessary to ionize salt-forming groups in the water-insoluble vinyl polymer, and then a dispersing machine is used as necessary. Or it can disperse | distribute using an ultrasonic emulsifier and can obtain by distilling off the organic solvent and carrying out phase inversion to an aqueous system.

  As a method for obtaining an aqueous dispersion of water-insoluble vinyl polymer particles containing a pigment as a colorant, a water-insoluble vinyl polymer is dissolved in an organic solvent, and a pigment, water, a neutralizing agent and, if necessary, a surfactant are added. In addition, after kneading, a method of diluting with water as necessary and distilling off the organic solvent to make an aqueous system is preferable.

  The amount of the colorant is preferably 20 to 1200 parts by weight, more preferably 50 to 900 parts by weight, and more preferably 50 to 900 parts by weight with respect to 100 parts by weight of the water-insoluble vinyl polymer, from the viewpoint of printing density and ease of inclusion in the polymer particles. Preferably it is 65-600 mass parts.

  As the organic solvent, alcohol solvents, ketone solvents and ether solvents are preferable, and hydrophilic organic solvents among these are more preferable.

  Examples of the alcohol solvent include isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like.

  Among these solvents, acetone, methyl ethyl ketone, and methyl isobutyl ketone are preferable, and toluene may be used in combination as necessary.

  As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, and glyceric acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like.

  There is no particular limitation on the degree of neutralization. Usually, it is preferable that the obtained aqueous dispersion has neutral liquidity, for example, pH of 4 to 10.

  Depending on the type of salt group, the solubility of water-insoluble vinyl polymer in water at 25 ° C after neutralizing the salt-forming group with sodium hydroxide or acetic acid to 100% 10 mass% or less is preferable from a viewpoint, 5 mass% or less is more preferable, and it is still more preferable that it is 1 mass% or less.

  The average particle diameter of the water-insoluble vinyl polymer particles containing the colorant in the aqueous dispersion and the water-based ink of the present invention is preferably 0.01 to 0.50 μm, more preferably from the viewpoint of prevention of nozzle clogging and storage stability. Is 0.02 to 0.30 μm, more preferably 0.04 to 0.20 μm. The average particle diameter corresponds to the “average particle diameter before storage” shown in the Examples, and is measured by the method shown in the Examples.

  The amount (solid content) of the polymer particles containing the colorant in the aqueous dispersion for inkjet recording and the aqueous ink is usually 0.5 to 30% by mass, more preferably 0.5 to 30% by mass in the aqueous ink, from the viewpoint of printing density and storage stability. Is preferably adjusted to 1 to 20% by mass, more preferably 1 to 15% by mass.

  The aqueous dispersion for ink-jet recording of the present invention contains additives such as a water-soluble organic solvent, a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, a chelating agent, and a surfactant, if necessary, and an aqueous ink. It can be.

  When the water-based ink for ink jet recording of the present invention contains a water-soluble organic solvent, there is an advantage that it is excellent in drying resistance and anti-freezing.

  As the water-soluble organic solvent, it is sufficient that the solubility in water at 25 ° C. is 1% by mass or more. Ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, N-methyl-2-pyrrolidone Nitrogen-containing compounds such as 1,3-dimethylimidazolidinone can be used. These can be used alone or in admixture of two or more. Among these, diethylene glycol, glycerin and 2-pyrrolidone are preferable.

  The amount of the water-soluble organic solvent in the water-based ink is preferably 0.1 to 50% by mass, more preferably 0.1 to 30% by mass.

  Wetting agents include polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, alkyl diols having 4 to 8 carbon atoms, polyethylene glycol, glycerin, polyglycerin, diethylene glycol diethyl ether, diethylene glycerin mono n-butyl ether And nitrogen-containing compounds such as ethers, acetates thereof, N-methyl-2-pyrrolidone and 1,3-dimethylimidazolidinone. The amount of the wetting agent in the water-based ink is preferably 0.1 to 30% by mass, more preferably 0.1 to 20% by mass.

  As the dispersant, anionic, nonionic, cationic, or amphoteric dispersants can be used.

  In the water dispersion for inkjet recording and the water-based ink of the present invention, the content of water is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass.

  Since the water-based ink for ink-jet recording of the present invention has high hydrophobicity of the terminal group of the monomer (A) used in the production of the water-insoluble vinyl polymer, the penetration into paper having a hydrophilic surface is suppressed. Can be effectively left on the paper surface, and a high print density can be obtained.

Production Examples 1 to 5 and Comparative Production Example 1
In a reaction vessel, 20 parts by mass of methyl ethyl ketone, 0.03 part by mass of a polymerization chain transfer agent (2-mercaptoethanol), and 10% by mass of each monomer (shown in parts by mass) shown in Table 1 are added and mixed. Nitrogen gas replacement was sufficiently performed to obtain a mixed solution.

  On the other hand, the remaining 90% by mass of each monomer (indicated by mass) shown in Table 1 was charged into a dropping funnel, then 0.27 parts by mass of a polymerization chain transfer agent (2-mercaptoethanol), 60 parts by mass of methyl ethyl ketone, and 1.2 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) was added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.

  Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 75 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the liquid temperature of the mixed solution is maintained at 75 ° C. for 2 hours, and then a solution in which 0.3 part by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) is dissolved in 5 parts by mass of methyl ethyl ketone is mixed. In addition to the solution, it was further aged at 75 ° C. for 2 hours and at 85 ° C. for 2 hours to obtain a polymer solution.

  A portion of the resulting polymer solution was isolated by drying at 105 ° C. under reduced pressure for 2 hours and removing the solvent. The weight average molecular weight was measured by gel permeation chromatography using polystyrene as a standard substance and 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide-containing dimethylformamide as a solvent.

The details of each compound shown in Table 1 are as follows:
Ethoxy polyethylene glycol monomethacrylate: In general formula (I), n is 9, _{R 1} and _{R 2} is a methyl group, octoxypolyethylene glycol monomethacrylate: In general formula (I), n is 6, _{R 1} is a methyl group , R ₂ is 2-ethylhexyl group, octoxypolyethylene glycol, polypropylene glycol monomethacrylate: in general formula (I), n is 6 (average added mole number of polyethylene glycol is 4, average added mole number of polypropylene glycol is 2) A monomer in which R ₁ is a methyl group, R ₂ is a 2-ethylhexyl group, and an oxyethylene group and an oxyethylenepropylene group are randomly added: Lauroxypolyethylene glycol monomethacrylate: In the general formula (I), n is 4, R ₁ is a methyl group, R ₂ is a dodecyl group Tealoxy polyethylene glycol monomethacrylate: a monomer in which n is 9, R ₁ is a methyl group, and R ₂ is an octadecyl group in general formula (I): Polyethylene glycol monomethacrylate: in general formula (I), n is 15, R ₁ is a methyl group, R ₂ is a hydrogen atom / methacrylic acid: manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: GE-110 (MAA)
-2-ethylhexyl methacrylate: manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester EH
・ Styrene monomer: Nippon Steel Chemical Co., Ltd., trade name: Styrene monomer ・ Styrene macromer: Toa Gosei Co., Ltd., trade name: AS-6S (styrene macromer), number average molecular weight: 6000

Examples 1-4 and Comparative Examples 1-2
5 parts by mass of the polymer obtained by drying the polymer solutions obtained in Production Examples 1 to 4 and Comparative Production Examples 1 and 2 under reduced pressure were dissolved in 45 parts by mass of methyl ethyl ketone, and a neutralizer (5N-hydroxylation) was dissolved therein. A predetermined amount of aqueous sodium solution was added to neutralize the salt-forming groups, and 20 parts by mass of carbon black [CI Pigment Black 7, manufactured by Cabot Corp.] was added and dispersed with a high-pressure homogenizer (uniform valve type).

  To the obtained kneaded product, 120 parts by mass of ion-exchanged water was added and stirred, and then methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed, whereby a pigment having a solid content concentration of 20% by mass was obtained. An aqueous dispersion of contained vinyl polymer particles was obtained.

  40 parts by mass of an aqueous dispersion of the obtained pigment-containing vinyl polymer particles, 15 parts by mass of glycerin, 5 parts by mass of 2- {2- (2-butoxyethoxy) ethoxy} ethanol, 2,4,7,9-tetramethyl- EO adduct of 5-decine-4,7-diol (n = 10) 0.5 part by mass and 59.5 parts by mass of ion-exchanged water were mixed, and the resulting mixture was filtered with a 5 μm filter [acetylcellulose membrane, outer diameter: 2.5 The mixture was filtered with a 25 mL needleless syringe (manufactured by Terumo Co., Ltd.) equipped with cm, manufactured by Fuji Photo Film Co., Ltd. to remove coarse particles, and water-based inks having the compositions shown in Table 2 were obtained.

  Next, physical properties of the obtained water-based ink were evaluated based on the following methods. The results are shown in Table 2.

(1) Ink viscosity Using a RE80L viscometer (rotor 1) manufactured by Toki Sangyo Co., Ltd., a viscosity of 100 r / min was measured at 20 ° C. and evaluated based on the following evaluation criteria.

〔Evaluation criteria〕
○: The ink viscosity is less than 3.5 mPa · s.
Δ: The ink viscosity is 3.5 mPa · s or more and less than 4.5 mPa · s.
X: The ink viscosity is 4.5 mPa · s or more and less than 7.0 mPa · s.

(2) Storage stability Using the viscometer, the dispersion stability is calculated from the viscosity before storage and the viscosity measured after 14 days at 70 ° C .: storage stability (%) = ([viscosity after storage] / [ Viscosity before storage]) × 100
And evaluated based on the following evaluation criteria.

〔Evaluation criteria〕
○: Within 100 ± 10%.
Δ: More than 100 ± 10 to less than 20%.
X: 100 ± 20% or more.

(3) Print density Using a commercially available Epson inkjet printer (model number: EM900C), print solid on the following five copy papers (plain paper) and leave at 25 ° C for 24 hours. The average value was obtained by measuring with a meter (manufactured by Macbeth, product number: RD914).

Plain paper: 1. Canon PB paper (obtained in East Japan), 2. Canon PB paper (obtained in West Japan), 3. XEROX 4200, 4. Canon Office, 5. Canon Brilliant White
When printing on plain paper, printed matter with a high print density can be obtained when the print density is 1.35 or more, particularly 1.40 or more.

(4) Scratch resistance Using the printer, solid printing was performed on commercially available copy paper, dried at 25 ° C. for 24 hours, and then the print surface was rubbed strongly with fingers. The degree of printing was evaluated based on the following evaluation criteria.

〔Evaluation criteria〕
○: Printing is hardly taken and the surroundings are not stained.
Δ: The print is slightly scraped, the surroundings are slightly stained, and the fingers are also slightly stained.
X: The printing is scraped off considerably, the surroundings are considerably dirty, and the fingers are also considerably dirty.

(5) Average particle size and dispersion stability Using an Otsuka Electronics Co., Ltd., laser particle analysis system ELS-8000 (cumulant method), the average particle size of the polymer particles containing the colorant contained in the ink (hereinafter referred to as “the particle size”) , “Average particle diameter before storage”). The ink was placed in a sealed container and stored in a constant temperature bath at 60 ° C. for one month, and then the average particle size (hereinafter referred to as “average particle size after storage”) was measured by the same method. As an indicator of dispersion stability, dispersion stability is expressed by the following formula:
Dispersion stability (%) = ([average particle diameter after storage] / [average particle diameter before storage]) × 100
And evaluated based on the following evaluation criteria.

〔Evaluation criteria〕
○: The dispersion stability is 90% or more and less than 110%.
Δ: The dispersion stability is 70% or more and less than 90%, or 110% or more and less than 130%.
X: Dispersion stability is less than 70% or 130% or more.

From the results shown in Table 2, it was found that each of the water-based inks obtained in each example had a high printing density, and was excellent in storage stability, dispersion stability, and scratch resistance. . Comparative Example 1 had a low printing density and poor storage stability.

Claims (8)

An aqueous dispersion of water-insoluble vinyl polymer particles containing a colorant,
The water-insoluble vinyl polymer is represented by (A) general formula (I):

Wherein R ₁ is a hydrogen atom or a lower alkyl group, R ₂ is an alkylene group having 2 to 18 carbon atoms or an alkylene group having 2 to 4 carbon atoms in which a hydrogen atom is substituted with a phenyl group, and n is 2 to 30 The number R ₃ represents a linear or branched alkyl group having 8 to 30 carbon atoms.)
A monomer represented by
An aqueous dispersion for inkjet recording, which is a water-insoluble vinyl polymer obtained by polymerizing a monomer mixture containing (B) a salt-forming group-containing monomer and (C) a hydrophobic monomer.   In the monomer mixture, (A) the monomer represented by the general formula (I) is 1 to 45% by mass, (B) the salt-forming group-containing monomer is 2 to 50% by mass, and (C) the hydrophobic monomer is The aqueous dispersion for inkjet recording according to claim 1, which is 10 to 88% by mass. (C) the hydrophobic monomer is (C-1) general formula (II):

Wherein R ₄ is a hydrogen atom or a lower alkyl group, R ₅ is an alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, an alkylaryl group or an arylalkyl group, or a ring having 3 to 22 carbon atoms. Represents a hydrocarbon group.)
A monomer having an alkyl group, an aryl group or a cyclic hydrocarbon group represented by:
(C-2) General formula (III):

(In the formula, R ₆ represents a hydrogen atom or a lower alkyl group, and R ₇ represents an aromatic hydrocarbon group having 6 to 22 carbon atoms.)
The aqueous dispersion for ink-jet recording according to claim 1 or 2, comprising at least one monomer selected from the group consisting of: (C-3) a macromer.   The aqueous dispersion for inkjet recording according to claim 3, wherein the aromatic ring-containing monomer of the general formula (III) is at least one selected from styrene, α-methylstyrene, vinyltoluene, and vinylnaphthalene.   The aqueous dispersion for inkjet recording according to claim 3 or 4, wherein the macromer has a polymerizable functional group at one end and has a number average molecular weight of 400 to 50,000.   The water dispersion for ink jet recording according to any one of claims 1 to 5, wherein the water-insoluble vinyl polymer has a weight average molecular weight of 3,000 to 300,000.   The aqueous dispersion for inkjet recording according to any one of claims 1 to 6, wherein the colorant is a pigment or a hydrophobic dye. An aqueous ink for inkjet recording, comprising the aqueous dispersion for inkjet recording according to any one of claims 1 to 7.