JP2006022229A - Inkjet recording aqueous ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording water dispersion containing water and a coloring agent, and an inkjet recording aqueous ink which contains the inkjet recording water dispersion and can exhibit a high printing density. <P>SOLUTION: The inkjet recording water dispersion is a water dispersion of a water insoluble vinyl polymer containing 5-30 wt.% structural units derived from a macromer and having an acid value of 20-70 (KOH mg/g) which comprises a coloring agent, and the viscosity (20°C) of the above water dispersion having a solid content concentration of 30 wt.% is 5 to 10 times the viscosity (20°C) of the above water dispersion having a solid content concentration of 10 wt.%. The inkjet recording aqueous ink comprises the water dispersion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

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. This method is remarkably widespread because it has many advantages that full color is easy and inexpensive, plain paper can be used as a recording member, and there is no contact with the substrate. Among them, in recent years, those using pigment-based ink as a colorant have become mainstream from the viewpoint of weather resistance and water resistance of printed matter (see, for example, Patent Documents 1 to 3).
Furthermore, in recent years, the mainstream is to set the surface tension of the ink in a low region of about 30 mN / m in order to cope with high-speed printing. However, when a pigment is used as a colorant in such a low surface tension ink, there is a problem that the printing density is lowered.

Japanese Unexamined Patent Publication No. 03-056573 Japanese Patent Laid-Open No. 03-160069 International Publication No. 00/39226 Pamphlet

  An object of the present invention is to provide an aqueous dispersion for ink jet recording containing water and a colorant, and an aqueous ink for ink jet recording that contains the aqueous dispersion for ink recording and can express a high print density.

  The present invention relates to an aqueous dispersion of water-insoluble vinyl polymer particles containing a coloring agent, containing 5 to 30% by weight of a structural unit derived from macromer (B) and having an acid value of 20 to 70 (KOHmg / g). Ink jet recording in which the viscosity (20 ° C.) of the aqueous dispersion having a solid content concentration of 30% by weight is 5 to 10 times the viscosity (20 ° C.) of the solid dispersion concentration of 10% by weight. And an aqueous ink for ink jet recording containing the aqueous dispersion.

  When the aqueous dispersion composed of the water-insoluble vinyl polymer of the present invention is used for an aqueous ink for inkjet recording, it becomes an excellent ink capable of expressing a high print density in printing on plain paper.

The present invention uses the water-insoluble vinyl polymer particles having a specific amount of a structural unit derived from a bulky macromer and a low acid value, so that the water-insoluble vinyl polymer particles in the aqueous dispersion (and / or the water-based ink) It has been found that the cohesiveness can be controlled.
That is, as the solvent in the water dispersion (and / or water-based ink) discharged from the inkjet nozzle evaporates, the viscosity increases according to the cohesiveness of the water-insoluble vinyl polymer particles. In the present invention, the viscosity (20 ° C.) of the solid content concentration of the aqueous dispersion (and / or the water-based ink) is 30% by weight (20 ° C.). 20 to 10 times, preferably 5 to 8 times that of the water-insoluble vinyl polymer containing the colorant is controlled to prevent penetration into the paper and printed. This makes it possible to increase the print density.
If the viscosity at a solid content concentration of 30% by weight (20 ° C.) is too high compared to the viscosity at a solid content concentration of 10% by weight (20 ° C.), water-insoluble vinyl polymer particles containing a colorant remain on the paper surface. The water-insoluble vinyl polymer particles having strong cohesiveness often have a problem in dispersion stability. If the viscosity at a solid content concentration of 30% by weight (20 ° C.) is too low compared to the viscosity at a solid content concentration of 10% by weight (20 ° C.), the water-insoluble vinyl polymer particles containing the colorant will be deep inside the paper. The print density is reduced.
Here, solid content concentration can be calculated | required with the following formula | equation.
Solid content = [(A−B) / A] × 100
A is the weight of the water dispersion of water-insoluble vinyl polymer particles, and B is the water dispersion of water-insoluble vinyl polymer particles maintained at 100 ° C. for 8 hours under a reduced pressure of −0.8 MPa (atmospheric pressure is 0 MPa). It means the weight of components that can sometimes volatilize.
Moreover, a viscosity is measured in the method mentioned later. The unit is mPa · s.
Each configuration will be described below.

(Water-insoluble vinyl polymer)
The water-insoluble vinyl polymer used in the present invention has an acid value of 20 to 70 (KOHmg / g) from the viewpoint of enhancing cohesiveness while maintaining the dispersibility of the water-insoluble vinyl polymer particles in the water dispersion. It is a water-insoluble vinyl polymer (hereinafter simply referred to as a water-insoluble polymer) containing 5 to 30% by weight of a structural unit derived from the macromer (B). The acid value is more preferably 40 to 70 (KOHmg / g) from the viewpoint of enhancing dispersibility. The acid value can be calculated from the constituent unit of the water-insoluble polymer. Alternatively, it can also be determined by a method in which it is dissolved in a suitable solvent (for example, methyl ethyl ketone) and titrated.
The water-insoluble polymer used in the present invention preferably further contains a structural unit derived from the hydrophobic monomer (C) and / or a structural unit derived from the nonionic monomer (D). That is, the water-insoluble polymer of the present invention is obtained by copolymerization of a monomer mixture containing an anionic monomer (A) and a macromer (B), and further, a hydrophobic monomer (C) is added to the monomer mixture. And / or those obtained by copolymerizing monomer mixtures containing nonionic monomers (D) (hereinafter collectively referred to as “monomer mixtures”).

Examples of the anionic monomer (A) include one or more selected from the group consisting of 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 (A), from the viewpoints of dispersion stability and ejection stability, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable.

Examples of the macromer (B) include a monomer (B) having a polymerizable functional group at one end and preferably having a number average molecular weight of 500 to 500,000, more preferably 1,000 to 10,000.
Specific examples of the macromer (B) include a styrenic macromer having a polymerizable functional group at one end, a silicone macromer having a polymerizable functional group at one end, and a macromer having a polymerizable functional group at one end, C1-C4 acrylic (meth) acrylate macromer (methyl methacrylate macromer having a polymerizable functional group at one end, butyl acrylate macromer having a polymerizable functional group at one end, polymerizable functional group at one end And isobutyl methacrylate-based macromers). Among these macromers (B), a styrenic macromer having a polymerizable functional group at one end is preferable from the viewpoint of sufficiently containing a pigment in the obtained water-insoluble polymer.

  Examples of the styrenic macromer having a polymerizable functional group at one end include a styrene homopolymer having a polymerizable functional group at one end and a copolymer of styrene and another monomer having a polymerizable functional group at one end. Can be mentioned.

In a copolymer of styrene and another monomer having a polymerizable functional group at one end, examples of the other monomer include (1) acrylonitrile and (2) an ester moiety having an alkyl group having 1 to 18 carbon atoms. A certain (meth) acrylic acid ester which may have a hydroxy group, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate , 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, (iso) octyl (meth) acryl , (Iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, etc. and (3) having an aromatic hydrocarbon group having 6 to 22 carbon atoms other than styrene Vinyl monomers are preferable, for example, α-methylstyrene, vinylnaphthalene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, 1,1-diphenylethylene, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy Examples include -3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and 2-acryloyloxyethyl phthalic acid. These can be used alone or in admixture of two or more.
In the present specification, “(iso or tertiary)” and “(iso)” are the case where a branched structure represented by “iso” or “tertiary” is present or not present (normal). Both are shown. Further, “(meth) acryl” means “acryl” or “methacryl”.

In addition, the content of styrene in the styrenic macromer having a polymerizable functional group at one end is preferably 60% by weight or more from the viewpoint of sufficiently containing the pigment in the obtained water-insoluble polymer. Preferably it is 70 weight% or more.
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.
Examples of commercially available styrenic macromers include trade names of Toa Gosei Co., Ltd., AS-6, AS-6S, AN-6, AN-6S, HS-6, HS-6S, and the like.

Among the silicone macromers having a polymerizable functional group at one end, the silicone macromer represented by the general formula (I) is preferable from the viewpoint of preventing scorching of the head of the ink jet printer.
X (Y) _q Si (R ³ ) _3-r (Z) _r (I)
(Wherein X is a polymerizable unsaturated group, Y is a divalent linking group, R ³ is independently a hydrogen atom, a lower alkyl group, an aryl group or an alkoxy group, and Z is a number average molecular weight of 500 or more. A monovalent siloxane polymer residue, q is 0 or 1, and r is an integer of 1 to 3).
The number average molecular weight of the macromer (B) is measured using polystyrene as a standard substance by gel permeation chromatography using 1 mmol / L chloroform containing dodecyldimethylamine as a solvent.

  Examples of the hydrophobic monomer (C) include alkyl (meth) acrylates and aromatic ring-containing monomers. These can be used alone or in admixture of two or more. Of these, those containing at least one selected from the group consisting of aromatic ring-containing monomers and macromers are preferred from the viewpoints of printing density, water resistance and scratch resistance.

  Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, etc. (Meth) acrylic acid ester which has the C1-C22 alkyl group of these is mentioned, These can be used individually or in mixture of 2 or more types, respectively.

  As an aromatic ring-containing monomer, from the viewpoint of water resistance, styrene, vinyl naphthalene, α-methyl styrene, vinyl toluene, ethyl vinyl benzene, 4-vinyl biphenyl, 1,1-diphenyl ethylene, benzyl (meth) acrylate, phenoxyethyl Selected from the group consisting of (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acryloyloxyethyl phthalate and neopentyl glycol acrylate benzoate One or more of these are preferred. Among these, a vinyl monomer having an aromatic hydrocarbon group having 6 to 22 carbon atoms is preferable, and at least one selected from the group consisting of styrene, α-methylstyrene, vinyl toluene, and vinyl naphthalene is water resistance and resistance. More preferable from the viewpoint of abrasion.

By using the nonionic monomer (D), when the water-based ink containing the water-dispersible material composed of the obtained water-insoluble polymer particles is used, the printed image has excellent gloss, low viscosity, and excellent discharge properties. There is an advantage that you can.
As the nonionic monomer (D), those represented by the following general formula (II) are preferable.
CH ₂ = CR ¹ COO (AO) _p R ² (II)
(In the formula, AO represents an oxyalkylene unit having 2 to 4 carbon atoms (provided that p oxyalkylene units may be the same or different. When the oxyalkylene units are different, block bonds, random bonds and alternating R ¹ represents a hydrogen atom or a methyl group, p represents an average number of added moles, 1 to 50, R ² represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. A phenyl group optionally substituted with an alkyl group of ˜9).
A monomer having an oxyethylene unit, an oxypropylene unit, or an oxytetramethylene unit as an oxyalkylene unit is preferred. p is preferably 2 to 25.
Specific examples of the nonionic monomer (D) include hydroxyethyl methacrylate, methoxypolyethylene glycol mono (meth) acrylate; polyethylene glycol mono (meth) acrylate; methoxypolypropylene glycol mono (meth) acrylate; polypropylene glycol mono (meth) acrylate; And ethylene glycol / propylene glycol (meth) acrylate; poly (ethylene glycol / propylene glycol) mono (meth) acrylate; octoxypolyethylene glycol / polypropylene glycol mono (meth) acrylate, and the like. These can be used alone or in admixture of two or more.

  The content of the anionic monomer (A) in the monomer mixture, that is, the content of the structural unit derived from the anionic monomer (A) in the water-insoluble polymer is determined by the dispersion stability of the resulting dispersion and the water-insoluble content containing the colorant. From the viewpoint of increasing the viscosity at a solid content concentration of 30% by weight of the aqueous dispersion of the polymer to 5 times or more of the viscosity at a solid content concentration of 10% by weight of the aqueous dispersion and increasing the print density, 3 to 12% by weight is preferable. 5 to 10% by weight is more preferable. By setting the content of the structural unit derived from the anionic monomer (A) within this range, the aggregation property of the water-insoluble vinyl polymer particles can be adjusted within a preferable range.

  The content of the macromer (B) in the monomer mixture, that is, the content of the structural unit derived from the macromer (B) in the water-insoluble polymer is at a solid content concentration of 30% by weight of the aqueous dispersion of the water-insoluble polymer containing the colorant. The viscosity is preferably 5 to 35% by weight, more preferably 10 to 30% by weight from the viewpoint of increasing the printing density by making the viscosity 5 times or more of the viscosity at a solid content concentration of 10% by weight of the aqueous dispersion. By setting the content of the structural unit derived from the macromer (B) within this range, the cohesiveness between the water-insoluble vinyl polymer particles can be adjusted within a preferable range.

The content of the hydrophobic monomer (C) in the monomer mixture, that is, the content of the structural unit derived from the hydrophobic monomer (C) in the water-insoluble polymer is 58 to 92% by weight from the viewpoint of printing density and dispersion stability. Is preferable, and 60 to 85% by weight is more preferable.
The content of the nonionic monomer (D) in the monomer mixture, that is, the content of the structural unit derived from the nonionic monomer (D) in the water-insoluble polymer is preferably 3 to 15% by weight from the viewpoint of ejection stability. 5 to 10% by weight is more preferable.
The weight ratio [(A) / [(B) + (C)]] of the anionic monomer (A), the macromer (B) and the hydrophobic monomer (C) in the monomer mixture is from the viewpoint of dispersion stability. 2/98 to 20/80 are preferable, and 3/97 to 10/90 are more preferable.

The weight average molecular weight of the water-insoluble polymer is preferably from 3,000 to 1,000,000, and more preferably from 5,000 to 500,000, from the viewpoints of dispersion stability of the colorant, water resistance, and dischargeability.
The weight average molecular weight of the water-insoluble polymer is measured using polystyrene as a standard substance by gel chromatography using 1 mmol / L dodecyldimethylamine-containing chloroform as a solvent.

The water-insoluble polymer is produced by copolymerizing monomers 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, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these and water is preferable.

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 An azo compound such as' -azobis (2-methylbutyronitrile), 1,1'-azobis (1-cyclohexanecarbonitrile) is preferred. Moreover, organic peroxides, such as t-butyl peroxy octoate, di-t-butyl peroxide, dibenzoyl oxide, can also be used.
The amount of the radical 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, mercaptoethanol; thiuram disulfides; hydrocarbons; unsaturated cyclic hydrocarbon compounds. An unsaturated heterocyclic compound may be used, and these may be used alone or in admixture of two or more.

Since the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, and solvent used, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced water-insoluble polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained water-insoluble polymer can be purified by repeating reprecipitation or removing unreacted monomers by membrane separation, chromatographic method, extraction method or the like.

The water-insoluble polymer used in the present invention is a water-insoluble polymer at 25 ° C. after neutralizing its salt-forming group with sodium hydroxide or acetic acid according to the type of the salt-forming group. The amount dissolved in 100 g of water is preferably 10 g or less, more preferably 5 g or less, and even more preferably 1 g or less from the viewpoint of reducing the viscosity of the water-based ink.
The water-insoluble polymer used in the present invention is used by neutralizing the salt-forming group derived from the anionic monomer (A) with a neutralizing agent described later. The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.
Here, the neutralization degree can be obtained by the following equation.
[Weight of neutralizer (g) / equivalent of neutralizer] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)] × 100

(Colorant)
The colorant may be either a hydrophobic dye or a pigment. Moreover, both can be mixed and used by arbitrary ratios. Among them, it is preferable to use a pigment for the development of high weather resistance, which has been in strong demand in recent years.
The pigment may be either an organic pigment or an inorganic pigment. If necessary, extender pigments can be used in combination.

  Examples of the organic pigment include azo pigments, diazo 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; and the like.

Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Of these, carbon black is preferred particularly for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of extender pigments include silica, calcium carbonate, and talc.

  As the dye, a hydrophobic dye is preferable because it can be contained in a water-insoluble polymer. Examples of hydrophobic dyes include oily dyes and disperse dyes. The solubility of the hydrophobic dye in the organic solvent is 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 incorporating the dye into the water-insoluble polymer. Is preferable, and 20-500 g / L (25 degreeC) is more preferable.

Although it does not specifically limit as oil-based dye, For example, CI solvent black 3, 7, 27, 29, 34, 45; 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.
Commercially available oily dyes include, for example, Nubian Black PC-0850, Oil Black HBB, Oil Black 860, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scarlet 308, Vali Fast Blue 2606 , Oil Blue BOS [above, Orient Chemical Co., Ltd., trade name], Neopen Yellow 075, Neopen Mazenta SE1378, Neopen Blue808, Neopen Blue 807, Neopen Blue FF4012, Neopen Cyan FF4238 (above, BASF Corporation, trade name) .

  The disperse dye is not particularly limited, but preferred examples include CI Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 204, 224, 237; CI Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119, 163 CI Disperse Red 54, 60, 72, 73, 86, 88, 91, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177, 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, CI Disperse Violet 33; CI Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225, 257, 266, 267, 287, 354, 358, 365, 368; CI Disperse Green 6: 1, 9; 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 and 7 as black, and nigrosine black dye are preferable. .

The content of the colorant in the aqueous dispersion and the water-based ink of the present invention is preferably 1 to 20% by weight, and more preferably 2 to 10% by weight from the viewpoint of increasing the print density.
Regarding the amount ratio of the water-insoluble polymer and the colorant used in the present invention, the viscosity at a solid content concentration of 30% by weight of the water dispersion of the water-insoluble polymer containing the colorant is the viscosity at the solid content concentration of 10% by weight. From the viewpoint of increasing the printing density while increasing the printing density by 5 times or more, 20 to 1,000 parts by weight of the colorant is preferable with respect to 100 parts by weight of the solid content of the water-insoluble polymer. Of these, 400 to 900 parts by weight are more preferable, and 500 to 800 parts by weight are even more preferable.

(Water dispersion of water-insoluble polymer particles containing colorant and water-based ink)
The aqueous dispersion of the present invention is preferably obtained by the following steps (1) and (2) because the acid value of the water-insoluble polymer used is low.
Step (1): A mixture containing a water-insoluble polymer, an organic solvent, a neutralizing agent, a colorant, and, if necessary, water is dispersed, and then water is added to add O (oil phase) / W (aqueous phase). Process)
Step (2): A step of removing the organic solvent.

In step (1), first, the water-insoluble polymer is dissolved in an organic solvent, and then a colorant, a neutralizing agent, and, if necessary, water, a surfactant and the like are added to the organic solvent and mixed. In the mixture, the colorant is preferably 5 to 50% by weight, the organic solvent is preferably 20 to 70% by weight, the water-insoluble polymer is preferably 2 to 40% by weight, and the water is 0.1 to 10% by weight. Is preferred. There is no particular limitation on the degree of neutralization. Usually, it is preferable that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5 to 10.
Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents, and those having a solubility in water of 20% by weight or less at 20 ° C. are preferable.

Examples of the alcohol solvent include n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like.
Examples of ketone solvents include methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone.
Examples of ether solvents include dibutyl ether and dioxane. Of these solvents, methyl ethyl ketone is preferred.

As the neutralizing agent, an acid or a base can be used depending on the kind of the salt-forming group in the water-insoluble polymer. Examples of the neutralizing agent include a volatile neutralizing agent and a non-volatile neutralizing agent.
Examples of the volatile neutralizing agent include acids such as hydrochloric acid, acetic acid and propionic acid, and bases such as ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine and trimethylamine.
Nonvolatile neutralizing agents include acids such as phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, gluconic acid, and glyceric acid, and bases such as sodium hydroxide and potassium hydroxide.

The method for dispersing the mixture in the step (1) is not particularly limited. A kneader such as a roll mill, a bead mill, a kneader or an extruder, a high-pressure homogenizer [Izumi Food Machinery Co., Ltd., trade name], a microfluidizer [Microfluidics, trade name] And a chamber type high-pressure homogenizer such as an open kneader such as a two-roll or three-roll is preferable in that a higher dispersion force can be expressed.
Next, after the dispersion treatment, water is added to make the system O (oil phase) / W (water phase) to obtain a uniform oil-in-water dispersion. The added water is preferably 50 to 300 parts by weight with respect to 100 parts by weight of the mixture.
In the step (2), an aqueous dispersion of water-insoluble polymer particles containing a colorant is obtained by distilling the organic solvent from the obtained dispersion to form an aqueous system. The organic solvent contained in the aqueous dispersion can be removed by a general method such as distillation under reduced pressure. The organic solvent in the water dispersion of the obtained water-insoluble polymer is substantially removed, and the amount of the organic solvent is 0.1% by weight or less, preferably 0.01% by weight or less.
The aqueous dispersion of water-insoluble polymer particles containing a colorant is a dispersion in which a solid content of a water-insoluble polymer containing a colorant is dispersed in water as a main solvent. Here, the form of the water-insoluble polymer particles containing the colorant is not particularly limited as long as the particles are formed of at least the colorant and the water-insoluble polymer. For example, a particle form in which a colorant is encapsulated in a water-insoluble polymer, a particle form in which a colorant is uniformly dispersed in a water-insoluble polymer, a particle form in which a colorant is exposed on the particle surface of the water-insoluble polymer, and the like are included.

The aqueous dispersion of water-insoluble polymer particles may be used as an aqueous ink as it is, but a wetting agent, a penetrating agent, a dispersing agent, a viscosity modifier, an antifoaming agent, an antifungal agent, an anti-foaming agent ordinarily used in an aqueous ink for inkjet recording. A rusting agent or the like may be added.
In the obtained water dispersion and water-based ink, the average particle diameter of the water-insoluble polymer particles containing the colorant is preferably 0.01 to 0.5 μm from the viewpoint of preventing clogging of the nozzle of the printer and dispersion stability. More preferably, it is 0.03-0.3 micrometer, Most preferably, it is 0.05-0.2 micrometer. The average particle diameter can be measured with a laser particle analysis system ELS-8000 manufactured by Otsuka Electronics Co., Ltd.
In addition, the content (solid content) of the water-insoluble polymer particles containing the colorant in the aqueous dispersion and the water-based ink is usually preferably 0.5 to 30% by weight from the viewpoint of printing density and ejection stability. More preferably, it is desirable to adjust to 1 to 15% by weight.
The water content in the aqueous dispersion and the water-based ink is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.
The preferred surface tension of the aqueous dispersion and aqueous ink of the present invention is 40 to 70 mN / m, more preferably 45 to 65 mN / m as the aqueous dispersion, and 28 to 50 mN / m as the aqueous ink. More preferably, it is 30-45 mN / m.
The viscosity (20 ° C.) of 10% by weight of the aqueous dispersion of the present invention is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a preferable viscosity when used as an aqueous ink.
In addition, the viscosity (20 ° C.) of the water-based ink of the present invention is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s in order to maintain good ejection properties.

Synthesis example 1
In the reaction vessel, 10 parts by weight of methyl ethyl ketone, 0.03 part by weight of 2-mercaptoethanol (chain transfer agent), 3 parts by weight of styrene macromonomer (St macromer) solution, 8.1 parts by weight of styrene monomer (St), polypropylene glycol 2 parts by weight of monomethacrylate (PPGMA) and 1.0 part by weight of methacrylic acid (MAA) were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution. Meanwhile, 0.27 parts by weight of 2-mercaptoethanol (chain transfer agent), 27 parts by weight of styrene macromonomer (St macromer) solution, 53.4 parts by weight of styrene monomer (St), polypropylene glycol monomethacrylate (PPGMA) ) 10 parts by weight, 9 parts by weight of methacrylic acid (MAA), 50 parts by weight of methyl ethyl ketone and 1.2 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) (polymerization initiator) are mixed. Nitrogen gas substitution was performed sufficiently to obtain a mixed solution.
While stirring the mixed solution in the reaction vessel under a nitrogen atmosphere, the temperature was raised to 75 ° C., and the mixed solution in the dropping funnel was gradually dropped over 3 hours.
The monomer composition is shown in Table 1.

After 2 hours from the end of dropping, a solution prepared by dissolving 0.3 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) in 5 parts by weight of methyl ethyl ketone was added, and further at 75 ° C. for 2 hours, further 2 2,2′-Azobis (2,4-dimethylvaleronitrile) in an amount of 0.3 parts by weight dissolved in 5 parts by weight of methyl ethyl ketone was added and aged at 80 ° C. for 1 hour.
The obtained water-insoluble polymer (1) was measured for weight average molecular weight by gel permeation chromatography using polystyrene as a standard substance and chloroform containing 1 mmol / L dodecyldimethylamine as a solvent. As a result, the weight average molecular weight was 35,000, and the acid value was 65 mgKOH / g.
The details of the compounds used above are as follows.
(1) Methyl ethyl ketone and 2-mercaptoethanol: Wako Pure Chemical Industries, Ltd. Reagent Grade 1 (2) 2,2′-azobis (2,4-dimethylvaleronitrile): Wako Pure Chemical Industries, Ltd. V-65
(3) Styrene macromer solution: Toa Gosei Co., Ltd., trade name: AS-6S (styrene macromonomer), solid content 50% by weight, number average molecular weight: 6,000
(4) Polypropylene glycol monomethacrylate: Aldrich Japan Co., Ltd. Reagent (Number average molecular weight: 375)
(5) Styrene monomer: Wako Pure Chemical Industries, Ltd. reagent special grade

Synthesis example 2
As the amount charged into the reaction vessel, 6 parts by weight instead of 3 parts by weight of the styrene macromonomer solution, 2 parts by weight of 2-hydroxyethyl methacrylate (HEMA) instead of 2 parts by weight of polypropylene glycol monomethacrylate, and as the preparation to the dropping funnel 54 parts by weight instead of 27 parts by weight of styrene macromonomer solution, 41.4 parts by weight instead of 53.4 parts by weight of styrene monomer, 10 parts by weight of 2-hydroxyethyl methacrylate (HEMA) instead of 10 parts by weight of polypropylene glycol monomethacrylate A water-insoluble polymer (2) was obtained in the same manner as in Synthesis Example 1, except that 6 parts by weight instead of 9 parts by weight of methacrylic acid was used. The weight average molecular weight measured by the same procedure as in Synthesis Example 1 was 45,000, and the acid value was 46 mgKOH / g.
The monomer composition is shown in Table 2.

Synthesis example 3
The amount charged into the reaction vessel is 1.4 parts by weight instead of 8.1 parts by weight of styrene monomer, 5 parts by weight instead of 1.0 part by weight of methacrylic acid, and 53.4 parts by weight of styrene monomer as the addition to the dropping funnel. A water-insoluble polymer (3) was obtained in the same manner as in Synthesis Example 1, except that 32.1 parts by weight was used instead of 9 parts and 33 parts by weight was used instead of 9 parts by weight of methacrylic acid. The weight average molecular weight measured by the same procedure as in Synthesis Example 1 was 68,000, and the acid value was 247 mgKOH / g. The monomer composition is shown in Table 3.

Synthesis example 4
The amount charged into the reaction vessel was 8 parts by weight instead of 6 parts by weight of the styrene macromonomer solution, 7.1 parts by weight instead of 8.1 parts by weight of the styrene monomer, and 54 parts by weight of styrene macromonomer solution was charged into the dropping funnel. A water-insoluble polymer (2) was obtained in the same manner as in Synthesis Example 2, except that 72 parts by weight instead of 4 parts by weight and 32.4 parts by weight instead of 41.4 parts by weight of the styrene monomer were used. The weight average molecular weight measured by the same procedure as in Synthesis Example 1 was 54,000, and the acid value was 44 mgKOH / g. The monomer composition is shown in Table 4.

Production Example 1
5 parts by weight (solid content) of the water-insoluble polymer (1) obtained in Synthesis Example 1 is dissolved in 25 parts by weight of methyl ethyl ketone, and a neutralizing agent (sodium hydroxide aqueous solution with a concentration of 5 mol / L Wako Pure Chemical Industries, Ltd.) 1.2 parts by weight (for volume analysis) was added, and 29 parts by weight of carbon black monarch 880 (Cabot Corporation) was further added as a water-insoluble colorant. Using three rolls [trade name: NR-84A, manufactured by Noritake Co., Ltd.], kneaded 20 times while appropriately adding ion-exchanged water. The solid content of the obtained paste was adjusted to 15% by weight, and further dispersed for 30 minutes using a microfluidizer (Microfluidics).
The resulting mixture was kept at 70 ° C. under reduced pressure using a rotary evaporator to remove methyl ethyl ketone and further remove a part of water to obtain an aqueous dispersion 1 in which the water-insoluble colorant is carbon black. Obtained. The average particle size of the obtained water dispersion was 120 nm.
In addition, the average particle diameter was measured using ELS-8000 of Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. In addition, uniform microparticles (average particle size: 204 nm) manufactured by Seradyn were used as a standard substance.

Production Example 2
In Production Example 1, the water-insoluble polymer (2) obtained in Synthesis Example 2 was used in place of the water-insoluble polymer (1) obtained in Synthesis Example 1, and 1.3 wt. An aqueous dispersion 2 (solid content 20% by weight) was obtained in the same manner as in Production Example 1, except that 0.9 parts by weight of the same was used instead of parts. The average particle size was 135 nm.

Production Example 3
In Production Example 1, the water-insoluble polymer (3) obtained in Synthesis Example 3 was used in place of the water-insoluble polymer (1) obtained in Synthesis Example 1, and 1.3 wt. An aqueous dispersion 3 (solid content 20% by weight) was obtained in the same manner as in Production Example 1, except that 2.1 parts by weight of the same was used instead of parts. The average particle size was 110 nm.

Production Example 4
In Production Example 2, an aqueous dispersion 4 was prepared in the same manner as in Production Example 2 except that the water-insoluble polymer (4) obtained in Synthesis Example 4 was used instead of the water-insoluble polymer (2) obtained in Synthesis Example 2. (20 wt% solid content) was obtained. The average particle size was 172 nm.

Example 1
11.8 parts by weight of the aqueous dispersion 1 obtained in Production Example 1 (solid content 20% by weight), 10 parts by weight of glycerin (reagent special grade of Wako Pure Chemical Industries, Ltd.), triethylene glycol monobutyl ether (reagent of Wako Pure Chemical Industries, Ltd.) Special grade) 7 parts by weight and 1 part by weight of Surfinol 465 (Air Products Co., Ltd.) were mixed, and ion exchange water was added to make a total of 50 parts by weight. Coarse particles are removed by filtration with a 25 mL needleless syringe (Terumo Corporation) equipped with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, Fuji Photo Film Co., Ltd.). Ink 1 was obtained.

Example 2
11.8 parts by weight of the aqueous dispersion 2 (solid content 20% by weight) obtained in Production Example 2 instead of 11.8 parts by weight of the aqueous dispersion 1 (solid content 20% by weight) obtained in Production Example 1 Ink jet recording ink 2 of the present invention was obtained in the same manner as Example 1 except that was used.

Comparative Example 1
Instead of 11.8 parts by weight of the aqueous dispersion 1 (solid content 20% by weight) obtained in Production Example 1, 11.8 parts by weight of the water dispersion 3 (solid content 20% by weight) obtained in Production Example 3 Comparative ink 1 was obtained in the same manner as in Example 1 except that

Comparative Example 2
11.8 parts by weight of the water dispersion 4 (solid content 20% by weight) obtained in Production Example 4 instead of 11.8 parts by weight of the water dispersion 1 (solid content 20% by weight) obtained in Production Example 1 Comparative ink 2 was obtained in the same manner as in Example 1 except that was used.

  The viscosities of the water-based inks for inkjet recording obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were all 2 to 5 mPa · s.

The performance of an aqueous dispersion of a water-insoluble colorant and the performance of an ink for ink jet recording prepared using the same were evaluated based on the following methods.
(1) Viscosity For measurement of the viscosity, 1 ml each of samples prepared by adjusting the solid content of the water dispersion of the water-insoluble colorant to 10% by weight and 30% by weight was used.
A sample having a solid content of 10% by weight was prepared to a solid content of 10% by weight by appropriately adding ion exchange water to the water dispersion prepared in Production Examples 1 to 4. The sample with a solid content of 30% by weight was obtained by maintaining the water dispersion prepared in Production Examples 1 to 4 at 100 ° C. under a reduced pressure of −0.8 MPa (atmospheric pressure = 0 MPa) and distilling off volatile components. Exchange water was appropriately added to prepare a solid content of 30% by weight.
The viscosity is measured with an E-type viscometer RE80L manufactured by Toki Sangyo. This measuring machine was adjusted so that the viscosity of 1 ml of 35% by weight glycerin aqueous solution was 3.060 mPa · s.
In addition, constant temperature water was circulated through the sample holding portion of the measuring machine and held at 20 ° C. In addition, after setting the sample, a retention time of 1 minute was set before starting the measurement, so that the measurement could be started after the sample reached the set temperature.

(2) Print density The ink for inkjet recording obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was solid-printed on commercially available plain paper (XEROX 4024) with an inkjet printer (Seiko Epson Corporation, model number EM930C). The print density was measured with a Macbeth reflection densitometer after standing at 25 ° C. for 1 hour.

(3) Evaluation standard print density is 1.2 or more.
1.1 or higher ○ Suitable for practical use
1.0 or more △ Practical minimum level
1.0 or less × difficult to use in practical use

(4) Evaluation results

Claims (6)

  An aqueous dispersion of water-insoluble vinyl polymer particles containing a colorant, containing 5 to 30% by weight of a structural unit derived from macromer (B) and having an acid value of 20 to 70 (KOHmg / g), An aqueous dispersion for ink-jet recording, wherein the viscosity of the aqueous dispersion having a solid content concentration of 30% by weight (20 ° C.) is 5 to 10 times the viscosity of the aqueous dispersion having a solid content concentration of 10% by weight (20 ° C.).   The water dispersion for inkjet recording according to claim 1, wherein the water dispersion has a solid content concentration of 10% by weight (20 ° C) of 2 to 6 mPa · s.   The water-insoluble vinyl polymer is a vinyl polymer containing 3 to 12% by weight of a structural unit derived from an anionic monomer (A) and 5 to 35% by weight of a structural unit derived from a macromer (B). An aqueous dispersion for inkjet recording.   The water-insoluble vinyl polymer contains 3 to 12% by weight of the structural unit derived from the anionic monomer (A), 5 to 35% by weight of the structural unit derived from the macromer (B), and the structural unit derived from the hydrophobic monomer (C) and / or Or the water dispersion for inkjet recording of Claim 1 or 2 which is a vinyl polymer containing the structural unit derived from a nonionic monomer (D).   The aqueous dispersion for inkjet recording according to any one of claims 1 to 4, wherein the macromer (B) is a styrene macromer. An aqueous ink for ink-jet recording containing the water dispersion according to any one of claims 1 to 5.