JP2010144095A - Method for producing aqueous dispersion for inkjet recording - Google Patents

Abstract

The present invention provides a method for producing an aqueous dispersion for ink jet recording that exhibits a high print density corresponding to high-speed printing, an aqueous dispersion for ink jet recording, and an aqueous ink.
A step (I) of mixing a colorant dispersion and a water-insoluble polymer emulsion containing an organic solvent, and a step of dispersing the resulting mixture to obtain a dispersion in which a water-insoluble polymer is adhered to the colorant (II). ), A method for producing an aqueous dispersion for inkjet recording, which comprises the step (III) of removing an organic solvent from the obtained dispersion, an aqueous dispersion obtained by the production method, and an inkjet recording water containing the aqueous dispersion. System ink.
[Selection figure] None

Description

  The present invention relates to a method for producing an aqueous dispersion for inkjet recording, 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 and adhering ink droplets directly from a very fine nozzle to a recording member. 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 object to be printed. Among these, pigment-based inks have become mainstream from the viewpoint of light resistance and water resistance of printed matter, and are preferably used in home inkjet printers. In recent years, the range of use of inkjet printers has expanded from home use to office use and commercial printing use, and high speed has become a technology trend. As a method for realizing high speed, a method of increasing the printing speed by reducing the number of printings by increasing the volume of ink droplets or improving the printing head (serial head to line head) is adopted.
The problems of high-speed printing and the issues to be overcome are that it cannot be printed twice or three times as in the past, so that sufficient dispersion stability and ejection stability are ensured so as not to cause deterioration in printing quality such as blurring or missing. In addition, it is necessary to prevent the coloring agent from penetrating into the inside of the paper when the colorant is highly colored so that a high printing density is expressed by one printing, especially when printing on plain paper.

As a method for improving the dispersion stability and storage stability of an aqueous pigment dispersion, a method using two types of polymer dispersants has been proposed.
For example, in Patent Document 1, in a method for producing an ink for inkjet recording containing a pigment, a water-soluble resin dispersant, a resin emulsion, a saccharide, and an aqueous dispersion medium, various additives are added after the pigment is dispersed in the dispersion medium. Is added to make ink, and a method of adjusting the particle diameter of the pigment particles by passing through a plurality of fine orifices is disclosed.
Patent Document 2 discloses an aqueous pigment dispersion containing at least a pigment and two or more types of anionic group-containing organic polymer compounds having different weight average molecular weights. Patent Document 3 discloses a specific Tg, A method of dispersing a pigment in water using two types of organic polymer compounds having an acid value and a weight average molecular weight is disclosed.
Patent Document 4 discloses an ink-jet ink composition containing a medium solution containing a water-insoluble hydrosol polymer in a pigment dispersion.
According to Patent Documents 1 to 4, although the dispersion stability is improved to some extent, it is not suitable for plain paper in high-speed printing, and it is difficult to obtain a high printing density.
In Patent Document 5, a pre-dispersion is prepared by mixing an emulsified composition (A) containing a water-insoluble polymer, an organic solvent, a neutralizing agent and water and a pigment (B), and then a media-type disperser is prepared. Disclosed is a method for producing an aqueous pigment dispersion which is continuously dispersed and separated using a homogenizer, and further dispersed using a homogenizer. However, when a water-insoluble polymer is used, atomization and dispersion become difficult, and the printing density required for high-speed printing is not sufficiently satisfactory.

JP-A-8-209045 JP 2000-160093 A Japanese Patent No. 3829098 Japanese Patent No. 3069543 Japanese Patent No. 3981396

  An object of the present invention is to provide a method for producing an aqueous dispersion for inkjet recording that exhibits a high printing density corresponding to high-speed printing, an aqueous dispersion for inkjet recording, and an aqueous ink.

The present invention has found that by mixing a colorant dispersion with a water-insoluble polymer emulsion and carrying out a dispersion treatment, a high printing density can be achieved even when printing on plain paper at high speed.
That is, the present invention provides the following [1] to [3].
[1] A method for producing an aqueous dispersion for inkjet recording, comprising the following steps (I) to (III).
Step (I): Step of mixing a colorant dispersion and a water-insoluble polymer emulsion containing an organic solvent Step (II): The mixture obtained in Step (I) was dispersed and the water-insoluble polymer adhered to the colorant. Step of obtaining dispersion Step (III): Step of removing organic solvent from dispersion obtained in Step (II) [2] An aqueous dispersion for ink jet recording obtained by the production method of [1] above.
[3] A water-based ink for ink-jet recording containing the water dispersion of [2].

  ADVANTAGE OF THE INVENTION According to this invention, the aqueous dispersion for inkjet recording which expresses the high printing density corresponding to high-speed printing can be manufactured efficiently.

The method for producing an aqueous dispersion for inkjet recording of the present invention comprises the following steps (I) to (III).
Step (I): Step of mixing a colorant dispersion and a water-insoluble polymer emulsion containing an organic solvent Step (II): The mixture obtained in Step (I) was dispersed and the water-insoluble polymer adhered to the colorant. Step of obtaining dispersion Step (III): Step of removing organic solvent from dispersion obtained in step (II) Hereinafter, each component, each step and the like used in the present invention will be described.

(Colorant dispersion)
The colorant dispersion is preferably a dispersion containing at least a colorant, a water-soluble polymer, and water, and is preferably a colorant dispersion in which these components are dispersed using a media-type disperser or the like. It is more preferable that the pigment dispersion is dispersed using a type disperser or the like.
<Colorant>
Examples of the colorant include pigments and hydrophobic dyes from the viewpoint of water resistance, and among them, it is preferable to use a pigment in order to express high weather resistance, which has recently been strongly demanded. 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 C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed. Moreover, solid solution pigments, such as a quinacridone solid solution pigment, can also be used.
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.

The hydrophobic dye is not particularly limited as long as it can be emulsified by a water-soluble polymer or contained in a water-soluble polymer. The hydrophobic dye is dissolved in an amount of 2 g / L or more, preferably 20 to 500 g / L (25 ° C.) with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer from the viewpoint of efficiently containing the dye in the polymer. What to do is desirable.
Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable. Examples of the oil-soluble dye include C.I. I. Solvent Black, C.I. I. Solvent Yellow, C.I. I. Solvent Red, C.I. I. Solvent Violet, C.I. I. Solvent Blue, C.I. I. Solvent Green, and C.I. I. One or more types of products selected from the group consisting of Solvent Orange are listed, which are commercially available from Orient Chemical Co., Ltd., BASF Corp. and others.
The above colorants can be used alone or in admixture of two or more at any ratio.

<Water-soluble polymer>
The water-soluble polymer used in the colorant dispersion is used for atomizing the colorant and improving the dispersion stability.
In the present invention, the water-soluble polymer means a polymer having a dissolution amount exceeding 10 g, preferably 20 g or more, more preferably 30 g or more when dissolved in 100 g of water at 25 ° C. When the water-soluble polymer has a salt-forming group, the above-mentioned dissolution amount refers to the dissolution amount when the salt-forming group of the water-soluble polymer is neutralized 100% with acetic acid or sodium hydroxide depending on the type. The degree of neutralization can be determined by the method described below. Examples of water-soluble polymers include water-soluble vinyl polymers, water-soluble ester polymers, water-soluble urethane polymers, and the like. Among these, water-soluble vinyl polymers are preferred. As the water-soluble vinyl polymer, a water-soluble vinyl polymer obtained by copolymerizing a monomer mixture containing (a) component: a salt-forming group-containing monomer and (b) component: a monomer represented by the following formula (1) is preferable. .
^{_{CH 2 = C (R 1)}} -R 2 (1)
(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ² represents an aromatic ring-containing hydrocarbon group having 6 to 22 carbon atoms.)
This water-soluble vinyl polymer has a structural unit derived from the component (a) and a structural unit derived from the component (b).

As the salt-forming group-containing monomer as component (a), an anionic monomer is preferable.
Examples of the anionic monomer 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.
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) -itaconate, and the like. .
Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acrylic acid. And leuoxyethyl phosphate.
Among the above anionic monomers, an unsaturated carboxylic acid monomer is preferable, and acrylic acid or methacrylic acid is more preferable from the viewpoints of ink viscosity, dischargeability, and the like.

As the monomer represented by the formula (1) as the component (b), R ¹ is preferably a hydrogen atom or a methyl group, and styrene, vinylnaphthalene, α-methylstyrene, vinyltoluene, ethyl from the viewpoint of printing density and the like. One or more selected from vinylbenzene, 4-vinylbiphenyl and 1,1-diphenylethylene are preferred. Among these, from the viewpoint of printing density, storage stability, and the like, a styrene monomer that is at least one selected from the group consisting of styrene, α-methylstyrene, and vinyltoluene is more preferable.

In the water-soluble vinyl polymer, the component (a) is preferably 5 to 80% by weight, more preferably 10 to 70% by weight, and the component (b) is preferably 15 to 85% by weight, more preferably 25 to 25% by weight. 75% by weight.
From the viewpoint of dispersibility, the water-soluble polymer preferably has a weight average molecular weight of 1000 to 30,000, more preferably 2,000 to 20,000, and an acid value of preferably 100 to 300 KOHmg / g, more preferably. Is 150-250 KOHmg / g. In addition, the weight average molecular weight of a water-soluble polymer can be measured by the method as described in an Example.
Examples of commercially available water-soluble polymers include JONCRL (registered trademark) 57J, 60J, 61J, 63J, 70J, PD-96J, and 501J of BASF Japan. These commercially available polymers are neutralized, and a neutralizing agent may be added separately as necessary.

<Manufacture of colorant dispersion>
There are no particular restrictions on the method for producing the colorant dispersion, but the water-soluble polymer is dissolved in water, and if necessary, a neutralizing agent, an organic solvent, a surfactant and the like are added and mixed, and then a colorant such as a pigment. It is preferable to perform preliminary mixing and dispersion by adding.
The dispersion medium of the colorant dispersion is water or an aqueous solvent, and an organic solvent that is dissolved or mixed in water may be appropriately added from the viewpoint of improving the dispersibility of the colorant or adjusting the viscosity. Examples of the organic solvent include alcohol solvents, ketone solvents, and the like, such as methanol, ethanol, 1-butanol, 2-butanol, acetone, methyl ethyl ketone, and the like.
An organic solvent can be used individually or in mixture of 2 or more types. In addition, an appropriate amount of a surfactant or the like may be added to the colorant dispersion from the viewpoint of further improving dispersibility.
In order to make the average particle diameter of the colorant dispersion a desired size, it is preferable to perform this dispersion treatment subsequently. The average particle size of the colorant dispersion is not particularly limited, but the average particle size at the time of dispersion is preferably 150 nm or less, more preferably 100 nm or less, and still more preferably 80 nm or less, from the viewpoint of ink color development and printing density. It is.

Stirrers used for pre-mixing and dispersion, such as paddle blades, turbine blades, anchor blades, and other commonly used stirrers, Ultra Dispers (Asada Steel Corporation, trade name), Ebara Milder Examples thereof include high-speed agitation type dispersion devices such as [Ebara Manufacturing Co., Ltd., trade name] and TK homomixer [Special Kika Kogyo Co., Ltd., trade name].
Examples of the disperser used in the present dispersion treatment include a roll mill, a media mill, a kneader, an extruder, an ultrasonic homogenizer, and a high-pressure homogenizer. Among these, a high-pressure homogenizer and a media mill with high atomization performance are listed. preferable. Among them, media mills (media type) compatible with micro media such as Ultra Apex Mill [Koto Kogyo Co., Ltd., trade name], Picomill [Asada Steel Co., Ltd., trade name], Star Mill (Ashizawa Finetech Co., Ltd., trade name) It is more preferable to use a dispersing machine.

Examples of the material of the media particles used in the media-type disperser include high-hardness metals such as steel and chrome alloys, high-hardness ceramics such as alumina, zirconia, zircon, and titania, and polymers such as glass, ultra high molecular weight polyethylene, and nylon. Materials and the like.
Ceramic media with a relatively high specific gravity among them due to the high shearing force, impact force, and crushing force required to atomize the colorant dispersion, and ease of separation of the colorant dispersion and media particles. Particles are preferable, and zirconia, titania and the like are more preferable from the viewpoint of wear resistance.
As the particle size (diameter) of the media particles used in the media-type disperser, a desired size can be used. However, the colorant is atomized, the dispersion time is shortened, and the media particles and the colorant dispersion are separated. In view of the above, the particle diameter of the media particles is preferably 0.01 to 0.25 mm, and more preferably 0.03 to 0.20 mm.

The peripheral speed of the tip of the agitator disk (rotor) of the media type dispersing machine is not particularly limited, but is preferably 4 m / s or more, and more preferably 6 m / s or more. If it is 4 m / s or more, the mixing and dispersing state in the dispersion chamber can be kept good, and the centrifugal force necessary to separate the media particles and the dispersion-treated product can be obtained.
The apparent filling rate of the media particles in the dispersion chamber of the media type dispersing machine is preferably in the range of 50 to 100% by volume based on the space in the dispersion chamber. When the amount is 50% by volume or less, the effects of pulverization, shearing, and collision with the media are reduced, and the effect of dispersing and atomizing the colorant is reduced.

As an operation for dispersing the colorant, the above-mentioned circulation type or continuous type media type disperser, media particles, media particle size, rotor peripheral speed, media particle filling rate, etc. are appropriately selected, set and dispersed. However, from the viewpoint of obtaining a desired degree of dispersion and preventing overdispersion, the energy required for the dispersion is 0.01 to 2.0 as a net integrated power per 1 kg of the colorant dispersion. It is preferable to perform dispersion so as to be in the range of [kwh / kg]. The net accumulated power means the net power [kw] multiplied by the processing time [h]. Here, the net power means the power obtained by subtracting the idling power from the actual load power to the disperser, and the idling power means the power without the media particles and the dispersion medium. Further, as another method for obtaining the net integrated power, a method of obtaining the total amount of heat given to the colorant dispersion and the amount of heat gradually heated by the cooling water as dispersion energy may be used.
Dispersion energy is given when the media-type disperser is passed through. From the viewpoint of preventing changes in the particle size and viscosity of the colorant dispersion due to heat generation, and preventing clogging and leakage of media particles. The treatment flow rate must be controlled within an appropriate range, and the flow rate is adjusted so that the average residence time per pass in the dispersion chamber is in the range of 30 seconds to 10 minutes, depending on the capacity and size of the disperser. It is preferable to do. Further, the total average residence time obtained by multiplying the average residence time by the number of passes is preferably in the range of 2 minutes to 100 minutes. The average residence time here means a value obtained by dividing the spatial volume [L] excluding the volume of media particles in the dispersion chamber by the processing flow rate [L / h].
The colorant dispersion preferably has a non-volatile component ratio of 5 to 50% by weight, more preferably 8 to 40% by weight, from the viewpoint of productivity and operability. The “nonvolatile component ratio” of the colorant dispersion is a value calculated based on the following calculation formula (1).
Non-volatile component ratio (% by weight) = [(total weight of water-soluble polymer, colorant, neutralizing agent and surfactant added if necessary) / (weight of colorant dispersion)] × 100 (1)

Further, from the viewpoint of preventing clogging or leakage of the media particles, the colorant dispersion preferably has a viscosity at the time of dispersion of 100 mPa · s or less, more preferably 50 mPa · s or less, and even more preferably 20 mPa · s or less. It is. Examples of the method for adjusting the viscosity include adjustment of the mass ratio of the organic solvent / water in addition to the adjustment of the non-volatile component ratio. In the latter case, the mass ratio of organic solvent / water is preferably 0 to 0.5.
As each component ratio in the colorant dispersion, the colorant is preferably 5 to 50% by weight, more preferably 7.5 to 40% by weight, and the water-soluble polymer (solid content) is preferably 0.1 to 10 wt%, more preferably 0.2 to 5 wt%, water is preferably 10 to 90 wt%, more preferably 20 to 85 wt%, and the organic solvent is preferably 0 -50% by weight, more preferably 5-30% by weight.
The amount of the water-soluble polymer in the non-volatile component is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight.
Dispersion treatment with a media type disperser is generally performed under cooling, and the temperature of the colorant dispersion is preferably 50 ° C. or less, and 40 ° C. or less from the viewpoint of thermal stability and prevention of thickening and aggregation. More preferred.

The colorant such as a pigment is atomized by the above method for producing a colorant dispersion, and the specific surface area becomes very large. As a result, the color developability and absorbance can be improved. For example, when using a yellow pigment as a colorant and comparing the case where it is dispersed with a water-soluble polymer and the case where it is dispersed with a water-insoluble polymer, the average particle size of the water-soluble polymer can be reduced by about 40-50 nm, and the absorption wavelength The intensity at 432 nm can also be increased by about 10 to 20%.
However, when a colorant dispersion dispersed using a water-soluble polymer is printed on plain paper as it is, penetration into the paper occurs and the colorant remaining on the paper surface is reduced. As a result, the print density becomes low and the desired performance cannot be satisfied.
Therefore, in the present invention, the previously prepared water-insoluble polymer emulsion is added to the colorant dispersion for dispersion treatment, so that the water-insoluble polymer is adhered to the surface of the colorant or a part of the surface of the colorant. Or by adhering the colorant dispersions to each other, the clogging effect on the paper surface and the hydrophobic cohesiveness are enhanced, the penetration of the colorant into the paper is suppressed, and the print density is considered to increase. .

(Water-insoluble polymer emulsion)
The water-insoluble polymer emulsion is preferably an emulsion composition containing a water-insoluble polymer having a salt-forming group, an organic solvent having a solubility in water at 20 ° C. of 5 to 40% by weight, a neutralizing agent and water.

<Water-insoluble polymer>
The water-insoluble polymer is a water-insoluble graft polymer from the viewpoint of improving printing density, dispersion stability, ejection stability, etc., and the main chain is composed of at least the structural unit derived from the component (a) and the component (b). It is a polymer chain containing a structural unit derived from, and the side chain is preferably a polymer chain containing a structural unit derived from at least component (d): a hydrophobic monomer.
In the present invention, it is considered that excellent dispersion stability and storage stability can be expressed when the main chain contains the structural unit derived from the component (a) and the structural unit derived from the component (b). .
Here, “water-insoluble” means that when a neutralized product of the target polymer is dissolved in 100 g of water at a temperature of 25 ° C., the dissolved amount is 10 g or less, preferably 5 g or less, more preferably 1 g or less. That means. The dissolution amount is the dissolution amount when 100% neutralized with sodium hydroxide or acetic acid according to the type of salt-forming group of the water-insoluble polymer. Such a water-insoluble polymer exhibits suitable adhesion and adsorption properties to the colorant.

In the main chain, the structural unit derived from component (a) is preferably obtained by polymerizing a salt-forming group-containing monomer. After polymer polymerization, a salt-forming group (anionic group, cationic group, etc.) is added to the polymer chain. ) May be introduced.
Specific examples and preferred examples of the salt-forming group-containing monomer are the same as described above, and acrylic acid or methacrylic acid is preferable.
Specific examples and preferred examples of the monomer represented by formula (1) as the component (b) are the same as those described above, and one or more selected from styrene, α-methylstyrene and vinyltoluene are preferable.
In the main chain, from the viewpoint of improving dispersion stability, storage stability, printing density, etc., (c-1) component: monomer represented by the following formula (2), (c-2) component: carbon number A (meth) acrylate monomer having 1 to 22 alkyl groups, (c-3) component: a structural unit derived from a nonionic (meth) acrylate monomer may be contained.
CH ₂ = CR ³ COOR ⁴ (2)
(In the formula, R ^{3 represents} a hydrogen atom or a methyl group, and R ⁴ is an arylalkyl group having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, and 6 to 22 carbon atoms. , Preferably an aryl group having 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms.)

Specifically, as component (c-1), benzyl (meth) acrylate, phenyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthalyl acrylate, 2-naphthalyl (Meth) acrylate, phthalimidomethyl (meth) acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acrylic And leuoxyethyl phthalate. Of these, benzyl (meth) acrylate is preferred.
Specific examples of the component (c-2) include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, and 2-ethylhexyl. (Meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, behenyl (meth) acrylate, etc. It can be obtained by polymerization.
In the present specification, “(iso or tertiary)” and “(iso)” are the case where the branched structure represented by “iso” or “tertiary” is present or absent, that is, “ Both “normal” are shown.

As the component (c-3), a nonionic (meth) acrylate monomer represented by the following formula (3) is preferable.
^{_{CH 2 = C (R 5)}} COO (R 6 O) n R 7 (3)
(In the formula, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ⁶ represents an alkylene group having 2 to 18 carbon atoms, n represents an average number of added moles, 1 to 30 and R ⁷ represents hydrogen. (A phenyl group which may have an atom, an alkyl group having 1 to 18 carbon atoms, or an alkyl group having 1 to 8 carbon atoms is preferred.)
In formula (3), from the viewpoint of polymerizability and the like, R ⁵ is preferably a hydrogen atom, a methyl group or the like, and R ⁶ is an ethylene group having 2 to 4 carbon atoms, a trimethylene group, a propane-1,2-diyl group, A tetramethylene group or the like is preferable. R ⁵ is preferably an ethylene group from the viewpoint of developing high glossiness of the printed matter, and is preferably a trimethylene group, a propane-1,2-diyl group, or a tetramethylene group from the viewpoint of developing a high printing density. . n is preferably a number from 2 to 25, more preferably a number from 4 to 23, from the viewpoint of printing density, storage stability, and the like. At least two of the n (R ⁶ O) s may be the same or different, and if different, either block addition or random addition may be used.
R ⁷ is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, from the viewpoints of high printing density, good storage stability, and the like. Moreover, the phenyl group which may have a C1-C8 alkyl group is preferable.
Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, hexyl group, octyl group, and 2-ethylhexyl group.

Specific examples of the nonionic monomer represented by the formula (3) include hydroxyethyl methacrylate, methoxy polyethylene glycol mono (meth) acrylate; polyethylene glycol mono (meth) acrylate; methoxypolypropylene glycol mono (meth) acrylate; polypropylene glycol Mono (meth) acrylate; Ethylene glycol / propylene glycol (meth) acrylate; Poly (ethylene glycol / propylene glycol) mono (meth) acrylate; Octoxy polyethylene glycol / polypropylene glycol mono (meth) acrylate; Phenoxy polyethylene glycol polypropylene glycol monomethacrylate Etc. These can be used alone or in combination of two or more.
Specific examples of the above commercially available monomers include Shin-Nakamura Chemical Co., Ltd. polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G, Nippon Oil & Fats Co., Ltd. Blemmer series, PE -90, 200, 350, PME-100, 200, 400, 1000, PP-500, PP-800, 1000, AP-150, 400, 550, 800, 50 PEP-300 , 50POEP-800B, 43PAPE-600B, and the like.

In the main chain, the weight ratio of the structural unit derived from the component (a) (calculated as an unneutralized amount; the same applies hereinafter) and the structural unit derived from the component (b) [content of the structural unit derived from the component (a) / ( b) Content of constituent unit derived from component] is preferably 1/1 to 1/10, and preferably 1 / 1.5 to 1/5 from the viewpoint of improving printing density, scratch resistance, and the like. It is more preferable.
In the water-insoluble polymer used in the present invention, the content of the structural units derived from the components (a) to (c) in the main chain is as follows.
From the viewpoint of improving the dispersibility of the water-insoluble polymer, the content of the structural unit derived from the component (a) is preferably 5 to 40% by weight, more preferably 10 to 35% by weight, and 15 to 30% by weight. Particularly preferred.
The content of the structural unit derived from the component (b) is preferably 10 to 80% by weight, more preferably 15 to 75% by weight, and particularly preferably 20 to 70% by weight from the viewpoint of improving the printing density, scratch resistance and the like. preferable.
The content of the structural unit derived from the component (c-1) is preferably 0 to 30% by weight, and more preferably 0 to 15% by weight from the viewpoint of improving dispersion stability. The content of the structural unit derived from the component (c-2) is preferably 0 to 30% by weight, more preferably 0 to 15% by weight, from the viewpoint of improving the printing density, marker resistance and the like. In addition, the content of the structural unit derived from the component (c-3) is preferably 0 to 40% by weight, and more preferably 0 to 30% by weight from the viewpoint of improving dispersion stability, printing density, and the like.

The water-insoluble polymer used in the present invention contains a structural unit derived from the hydrophobic monomer (d) component in the side chain from the viewpoint of adhering the water-insoluble polymer to the colorant and improving the printing density.
In the side chain, the content of the structural unit derived from the component (d) is preferably 60% by weight or more, more preferably 70% by weight or more from the viewpoint of adsorbing the water-insoluble polymer to the colorant and improving the printing density. 90% by weight or more is particularly preferable.
As the hydrophobic monomer (d) component, a styrene macromer is preferable. A side chain containing a structural unit derived from a styrenic macromer can be obtained by copolymerizing a styrenic macromer having a polymerizable functional group at one end.
Examples of the styrenic macromer include a styrene homopolymer having a polymerizable functional group at one end, or a copolymer of styrene and another monomer having a polymerizable functional group at one end, and having at one end. As the polymerizable functional group, an acryloyloxy group or a methacryloyloxy group is preferable. Examples of other monomers copolymerized with styrene include (meth) acrylic acid esters, aromatic ring-containing (meth) acrylates, acrylonitrile and the like.
The number average molecular weight of the styrenic macromer is preferably 1,000 to 10,000, more preferably 2,000 to 8,000, from the viewpoint of keeping the viscosity low while increasing the copolymerization ratio in order to enhance the storage stability. preferable.
The number average molecular weight of the styrenic macromer can be measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.
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.

In the water-insoluble polymer used in the present invention, the weight ratio between the main chain containing the structural unit derived from the component (a) and the main chain containing the structural unit derived from the component (b) and the side chain containing the structural unit derived from the component (d) [ The main chain / side chain] is preferably 1/1 to 20/1, more preferably 3/2 to 15/1, in order to improve printing density, gloss, scratch resistance, and the like. 1 to 10/1 is more preferable. (The polymerizable functional group is calculated as contained in the side chain. The same applies hereinafter)
The water-insoluble polymer used in the present invention can be obtained by copolymerizing a monomer mixture containing the component (a), the component (b), and the component (d). Further, those obtained by copolymerizing the monomer mixture with a monomer mixture containing component monomer (c) (hereinafter collectively referred to as “monomer mixture”) are preferred.
The contents of the components (a) to (d) in the monomer mixture, or the contents of the structural units derived from the components (a) to (d) present in the main chain or side chain in the water-insoluble polymer are as follows. It is.
The content of the component (a) (content as an unneutralized amount; the same applies hereinafter) or the content of the structural unit derived from the component (a) present in the main chain in the water-insoluble polymer From the viewpoint of improving the dispersion stability and gloss of printed matter, the content is preferably 3 to 30% by weight, more preferably 5 to 27% by weight, and still more preferably 10 to 25% by weight.
The content of the component (b) or the content of the structural unit derived from the component (b) present in the main chain in the water-insoluble polymer is 10 to 10 from the viewpoint of improving the print density, scratch resistance, etc. of the printed matter. 80 weight% is preferable, 15-70 weight% is more preferable, and 20-60 weight% is still more preferable.
The content of the component (c) or the content of the structural unit derived from the component (c) is preferably 0 to 40% by weight, and 0 to 30% by weight from the viewpoint of printing density, dispersion stability, marker resistance and the like. More preferred.
The content of the component (d) or the content of the structural unit derived from the component (e) present in the side chain in the water-insoluble polymer is 5 to 50% by weight from the viewpoint of improving the print density of the printed matter. Preferably, 5 to 40% by weight is more preferable, and 5 to 35% by weight is particularly preferable.
Weight ratio of [(a) component content / (d) component content] in the monomer mixture, or [(a) component-derived constituent unit content / (d) component in the water-insoluble polymer] From the viewpoints of dispersion stability, print density, and the like, the weight ratio of the content of the derived structural unit] is preferably 1/2 to 3/1, and more preferably 1/1 to 2.5 / 1.

The water-insoluble polymer used in the present invention is preferably used by neutralizing a salt-forming group derived from a salt-forming group-containing monomer with a neutralizing agent described later. The neutralizing agent can be neutralized with an acid or base depending on the type of salt-forming group in the water-insoluble polymer, and hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycol Acids such as acid, gluconic acid and glyceric acid, and bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, trimethylamine and triethanolamine can be used.
The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 30 to 100%. Moreover, when neutralizing excessively at the time of pre-emulsification, the neutralization degree can also be adjusted by using the neutralizing agent which can be removed by a concentration process.
The degree of neutralization can be obtained by the following calculation formula (2) when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100 (2)
When the salt-forming group is a cationic group, the degree of neutralization can be determined by the following calculation formula (3).
[[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]] × 100 (3)
The acid value and amine value can be calculated from the structural unit of the water-insoluble polymer, but can also be determined by a method of titrating after dissolving the polymer in an appropriate solvent (for example, methyl ethyl ketone).
From the viewpoint of dispersion stability, the acid value of the polymer is preferably 30 (KOHmg / g) or more, and more preferably 40 (KOHmg / g) or more. Further, from the viewpoint of developing a high printing density, it is preferably 200 (KOHmg / g) or less, and more preferably 150 (KOHmg / g) or less.

<Production of water-insoluble polymer>
The water-insoluble polymer used in the present invention is produced by copolymerizing a monomer mixture 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.
Although the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, solvent, etc. to be used and cannot be determined unconditionally, the polymerization temperature is usually preferably 30 to 100 ° C., more preferably 50 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 weight average molecular weight of the water-insoluble polymer thus obtained is preferably 90,000 to 400,000 from the viewpoint of dispersion stability of the colorant, water resistance, dischargeability, etc., and 120,000 to 350,000. More preferably, it is 000.
In addition, the weight average molecular weight of a water-insoluble polymer can be measured by the method as described in the Example mentioned later.

<Organic solvent>
The organic solvent used in the water-insoluble polymer emulsion is used to appropriately dissolve the water-insoluble polymer (part). As an organic solvent, the thing whose solubility with respect to water in 20 degreeC is 5-40 weight% (5-40g with respect to 100g of water) is preferable, and the thing of 5-30 weight% is more preferable. Examples of these organic solvents include alcohol solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, halogenated hydrocarbon solvents, and the like.
Examples of the alcohol solvent include 1-butanol and 2-butanol, and examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, and acetone. Examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene and the like. Examples of the aliphatic hydrocarbon solvent include pentane, hexane and heptane. Examples of the halogenated hydrocarbon solvent include chloroform, Examples include carbon dichloride, carbon tetrachloride, and ethylene chloride. Among these, ketone solvents, particularly methyl ethyl ketone and methyl isobutyl ketone are preferable from the viewpoint of safety and operability when removing the solvent in the post-treatment.
These organic solvents can be used individually or in mixture of 2 or more types.

<Preparation of water-insoluble polymer emulsion>
As a method for preparing a water-insoluble polymer emulsion, firstly dissolve a water-insoluble polymer in an organic solvent, then add a neutralizing agent and water in this order, and add a surfactant or the like as required to obtain a desired average particle size. Stir and mix until it becomes an oil-in-water emulsion (emulsion) with If it is difficult to emulsify, mechanical force such as a high-speed stirrer or a disperser may be applied as necessary, and the average particle size is preferably adjusted to be in the range of 0.01 to 2 μm. .
As an emulsification preparation method, a phase inversion method or a normal phase method can be used. In that case, first prepare a mixed solution of water and neutralizing agent, and drop a mixed solution of water-insoluble polymer and organic solvent into it, or drop a mixture of water-insoluble polymer, organic solvent and neutralizing agent into water. And the like. The temperature during emulsification is preferably 40 ° C. or lower, more preferably 30 ° C. or lower, from the viewpoints of particle size and viscosity stability.
As each component ratio in the emulsion, the organic solvent is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, and the water-insoluble polymer (solid content) is preferably 2 to 40% by weight, More preferably, it is 3 to 30% by weight, and water is preferably 50 to 90% by weight, more preferably 55 to 85% by weight.
Moreover, a neutralizing agent can be suitably adjusted and added so that the liquid property of the water dispersion finally obtained may be neutral, for example, pH may be 4.5-10. When the salt-forming group of the water-insoluble polymer is anionic, it is preferably adjusted to a pH such as 7-10.

[Method for producing aqueous dispersion for inkjet recording]
Process (I)
Step (I) is a step of mixing the colorant dispersion and the water-insoluble polymer emulsion.
There is no particular limitation on the method for mixing the colorant dispersion and the water-insoluble polymer emulsion, and any method can be used as long as it can be uniformly mixed. For example, mixing can be performed using a general stirring blade such as a paddle blade, a turbine blade, or an anchor blade.
There is no restriction | limiting also about a preparation order, A water-insoluble polymer emulsion may be added to a colorant dispersion, and a colorant dispersion may be added to a water-insoluble polymer emulsion.
For each component ratio, the colorant dispersion is preferably 70 to 95% by weight, more preferably 75 to 90% by weight, and the water-insoluble polymer emulsion is preferably 5 to 30% by weight, more preferably 10 to 25% by weight. %.

Process (II)
Step (II) is a step of dispersing the mixture obtained in step (I) to obtain a dispersion in which a water-insoluble polymer is further adhered to a colorant adsorbed with a water-soluble polymer.
Examples of the disperser that can be used as the dispersion method of the mixture in the step (II) include a high-speed stirring type disperser, a roll mill, a media mill, a kneader, an extruder, an ultrasonic homogenizer, a high-pressure homogenizer, and the like. Among them, a high-pressure homogenizer that applies a very strong collision / shearing force is preferable from the viewpoint of allowing the water-insoluble polymer to adhere to the colorant dispersion and simultaneously suppressing agglomeration between the colorant dispersions. A chamber type high-pressure disperser such as a company, a product name] and an optimizer [Sugino Machine Co., Ltd., a product name] is preferably used.
The pressure during the high-pressure homogenizer treatment is preferably 100 MPa or more, and more preferably 150 MPa or more. From the same point of view, the number of processing passes is at least 1 pass or more, preferably 3 passes or more, more preferably 5 passes or more.
Since the temperature of the dispersion rises near 20 to 50 ° C. before and after the dispersion treatment, the temperature before the dispersion treatment is preferably at least 20 ° C. or less, and immediately after the dispersion, the temperature is adjusted to 20 ° C. or less by cooling. It is good. Specifically, a spiral heat exchanger or a plate heat exchanger having a necessary heat transfer area at the outlet of the high-pressure disperser is installed to carry out slow heating.
As for the operation method, two tanks and a high-pressure disperser are installed from the viewpoint that the total number of dispersions can pass through the high-pressure dispersion chamber the desired number of times without causing a distribution of the number of passes as with the media type disperser. Examples of preferable driving operations include a catch ball method, or a method in which the dispersion liquid passed through one pass is returned to the original tank again and the same pass operation is repeated.

The proportion of each component in the mixture is preferably 5 to 30% by weight of the colorant, more preferably 7.5 to 25% by weight, and preferably 1 to 10% by weight of the organic solvent brought from the water-insoluble polymer emulsion. More preferably, it is 2 to 8% by weight, water is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and the water-soluble polymer and the water-insoluble polymer (total solid content) are preferably 0.8. 5 to 20% by weight, more preferably 1.0 to 10% by weight.
Further, the weight ratio of the water-soluble polymer to the water-insoluble polymer (water-soluble polymer / water-insoluble polymer) in the mixture is preferably 1/5 to 2/1, and more preferably 1/4 to 1/1. When the weight ratio exceeds 2/1, the colorant easily penetrates into the paper and it is difficult to develop a high print density, and when it is less than 1/5, it is difficult to disperse and atomize the colorant dispersion. .
The nonvolatile component ratio of the mixture is preferably 3 to 40% by weight and more preferably 5 to 30% by weight from the viewpoint of productivity and operability.
The “nonvolatile component ratio” of the mixture is a value calculated based on the following calculation formula (4).
Nonvolatile component ratio (% by weight) = [(total weight of solid content in colorant dispersion and solid content in water-insoluble polymer emulsion) / (total weight of colorant dispersion and water-insoluble polymer emulsion)] × 100 ( 4)
The dispersion particle size of the above mixture is preferably 30 nm to 300 nm, more preferably 50 nm to 200 nm as the average particle size from the viewpoint of dispersion stability as an aqueous dispersion and ink and printing density on plain paper. Distributed processing. The average particle size is measured by the method described in the examples.
During the dispersion treatment, when the water-insoluble polymer hardly adheres to the colorant dispersion or when the dispersion stability is improved, the dispersion composition and the solid content concentration may be changed stepwise. Specifically, the dispersion is initially carried out with a composition having a high solvent ratio, and then water is added to lower the ratio of (organic solvent / water). The dispersion is first carried out at a high solid content, and then water is added. And the like, and the like, and the like.

Process (III)
Step (III) is a step of removing the organic solvent from the dispersion obtained in step (II).
By the step (III), an aqueous dispersion in which a water-soluble polymer and a water-insoluble polymer are attached to the colorant surface or a part of the surface can be obtained. The removal of the organic solvent can be performed by a general method such as vacuum distillation.
The organic solvent in the obtained aqueous dispersion is substantially removed, and the amount of the remaining organic solvent is 0.1% by weight or less, preferably 0.01% by weight or less. Further, the content of the water-soluble polymer and the water-insoluble polymer in the water dispersion is 1 to 10% by weight and 5 to 30%, respectively, with respect to 100% by weight of the colorant from the viewpoint of the stability of the water dispersion and the printing density. It is preferably in the range of wt%. Further, from the same viewpoint, the content of the colorant is preferably 10 to 50% by weight, and more preferably 15 to 40% by weight.

An aqueous dispersion obtained by the method having the steps (I) to (III) includes an aqueous dispersion in which particles having a water-soluble polymer and a water-insoluble polymer attached to a colorant are dispersed in water as a main medium. It has become. This water dispersion has a large specific surface area of the colorant because the colorant is atomized, and a water-insoluble polymer adheres to the colorant, so that the ink containing this water dispersion is placed inside the paper after printing. It is considered that the printing density is increased because it hardly penetrates and remains on the paper surface.
Here, the form of the particles of the aqueous dispersion is not particularly limited, as long as the particles are formed of at least a colorant, a water-soluble polymer, and a water-insoluble polymer. For example, a particle form in which a colorant with a water-soluble polymer attached to a water-insoluble polymer is encapsulated, a particle form in which a colorant with a water-soluble polymer attached to a water-insoluble polymer is uniformly dispersed, or a water-soluble polymer on the particle surface of the water-insoluble polymer. The form of the particle | grains which the coloring agent with which the adhesive polymer adhered adsorb | sucked are included.
From the above viewpoint, the water dispersion obtained by the method of the present invention has a polymer adsorption rate (%) of preferably from 50 to 100%, more preferably from 60 to 98, and even more preferably 70. ~ 95%. The adsorption rate of this polymer can be measured by the measurement method described in the examples.
After the steps (I) to (III), centrifugation or filter filtration may be performed to remove coarse particles, and an operation for further improving the dispersion stability and discharge stability may be performed.

  The aqueous dispersion of the present invention can be used as a water-based ink as it is. However, in a high-speed printer, dispersion stability and ejection stability in continuous printing are particularly important as the ink, so that stability is improved. Therefore, it is preferable to crosslink the water-soluble polymer and / or water-insoluble polymer particles using a crosslinking agent.

<Crosslinking agent>
As the crosslinking agent, a compound having two or more reactive functional groups in the molecule is preferable in order to appropriately crosslink the polymer. The number of the reactive functional groups is preferably 2 to 6 from the viewpoint of controlling the molecular weight and improving storage stability. Preferred examples of the reactive functional group include one or more selected from the group consisting of a hydroxyl group, an epoxy group, an aldehyde group, an amino group, a carboxy group, an oxazoline group, and an isocyanate group.
The crosslinking agent used in the present invention is preferably 50 g or less, more preferably 40 g or less, when dissolved in 100 g of water at 25 ° C. from the viewpoint of efficiently crosslinking the surface of the polymer, particularly the water-insoluble polymer. More preferably, it is 30 g or less. The molecular weight is preferably 120 to 2000, more preferably 150 to 1500, and still more preferably 150 to 1000, from the viewpoint of easy reaction and storage stability of the aqueous dispersion.

Preferable examples of the crosslinking agent include the following (a) to (c).
(A) Compound having two or more epoxy groups in the molecule: for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether Polyglycidyl ethers such as trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether.
(B) Compounds having two or more oxazoline groups in the molecule: for example, bisoxazoline compounds such as 2,2′-bis (2-oxazoline), 1,3-phenylenebisoxazoline, 1,3-benzobisoxazoline, A compound having a terminal oxazoline group obtained by reacting the compound with a polybasic carboxylic acid.
(C) Compound having two or more isocyanate groups in the molecule: for example, organic polyisocyanate or isocyanate group-terminated prepolymer.
Among these, (a) a compound having two or more epoxy groups in the molecule is preferable, and ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are particularly preferable.

The amount of the crosslinking agent used is preferably 0.3 / 100 to 50/100, more preferably 1/100 to 40/100 in terms of the weight ratio of [crosslinking agent / polymer], from the viewpoint of storage stability of the aqueous dispersion. 2/100 to 30/100 is more preferable, and 5/100 to 25/100 is particularly preferable.
The amount of the crosslinking agent used is preferably an amount that reacts with 0.1-20 / mmol / g of the anionic group of the polymer in terms of the amount of anionic group per 1 g of the polymer. The amount reacting with 15 / mmol / g is more preferable, and the amount reacting with 1-10 mmol / g is more preferable.
The crosslinked polymer preferably contains 0.5 mmol / g or more of an anionic group (particularly preferably a carboxy group) neutralized with a base per 1 g of the crosslinked polymer. Such a crosslinked polymer is considered to contribute to the stability of anionic crosslinked polymer particles containing a colorant by dissociating in an aqueous dispersion and charge repulsion between anions.
Here, the crosslinking rate (mol%) of the crosslinked polymer obtained from the following calculation formula (5) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, and still more preferably 30 to 60 mol%. . The crosslinking rate can be determined by calculation from the amount of the crosslinking agent used and the number of moles of the reactive group, the amount of polymer used and the number of moles of the reactive group of the polymer that can react with the reactive group of the crosslinking agent.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent / number of moles of reactive group capable of reacting with crosslinking agent of polymer] × 100 (5)
In the calculation formula (5), “the number of moles of the reactive group of the crosslinking agent” is a value obtained by dividing the weight of the crosslinking agent used by the equivalent of the reactive group. That is, the number of moles of the crosslinking agent used is multiplied by the number of reactive groups in one molecule of the crosslinking agent.

[Water dispersion for inkjet recording]
The aqueous dispersion for ink jet recording of the present invention is obtained by the above production method, and may be used as a water-based ink having water as a main medium as it is.
The content of each component in the aqueous dispersion of the present invention is as follows.
The content of the colorant is preferably 1 to 25% by weight, more preferably 2 to 20% by weight, still more preferably 4 to 15% by weight, and particularly preferably 4 to 8% by weight from the viewpoint of increasing the print density. The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The preferred surface tension (20 ° C.) of the aqueous dispersion of the present invention is 30 to 70 mN / m, more preferably 35 to 65 mN / m, and the viscosity (20 ° C.) of 20% by weight (solid content) of the aqueous dispersion. Is preferably 1 to 12 mPa · s, more preferably 1 to 9 mPa · s, more preferably 2 to 6 mPa · s, and still more preferably 2 to 5 mPa · s.

[Water-based ink for inkjet recording]
The water-based ink for ink-jet recording of the present invention contains the above-mentioned aqueous dispersion. Here, “water-based” means that water occupies the largest proportion in the medium contained in the water-based ink, and the medium may be only water, and water and one or more organic solvents. And a mixed solvent. To this water-based ink, wetting agents, penetrants, dispersants, viscosity modifiers, antifoaming agents, antifungal agents, rust preventive agents and the like that are usually used in water-based inks can be added.
The content of each component in the aqueous ink of the present invention is as follows.
The content of the colorant is preferably 3 to 30% by weight, more preferably 4 to 20% by weight, still more preferably 4 to 15% by weight, and particularly preferably 4 to 8% from the viewpoints of print density and storage stability. It is weight. The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The preferred surface tension (20 ° C.) of the aqueous ink of the present invention is 23 to 50 mN / m, more preferably 23 to 45 mN / m, still more preferably 25 to 40 mN / m, and the viscosity (20 ° C.) of the aqueous ink is In order to maintain good ejection reliability, it is preferably 2 to 20 mPa · s, more preferably 2.5 to 16 mPa · s, and further preferably 2.5 to 12 mPa · s.

Further, the average particle diameter as the water-based ink is preferably 30 nm to 300 nm, more preferably 50 nm to 200 nm, from the viewpoints of high-speed printer suitability and printing performance.
The water content in the water-based ink is 60% by weight or less, preferably 20 to 60% by weight, more preferably 30 to 60% by weight, still more preferably 30 to 57% by weight, from the viewpoint of curling suppression. -55 wt% is particularly preferred.
The content of the hydrophilic organic solvent in the water-based ink is preferably 10% by weight or more, more preferably 10 to 35% by weight, from the viewpoint of suppressing curling and maintaining storage stability while suppressing an increase in viscosity. More preferably, it is 15 to 35% by weight.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is particularly suitable for a piezo ink jet printer.

  In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. The weight average molecular weight of the polymer, the average particle diameter of the dispersion, the viscosity of the aqueous dispersion, the polymer adsorption rate of the aqueous dispersion, the printing density of the ink, and the storage stability of the ink are measured or evaluated by the following methods. It was.

(1) Weight average molecular weight of polymer Gel chromatography using N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent [GPC apparatus (HLC- 8120GPC), a column manufactured by Tosoh Corporation (TSK-GEL, α-M × 2), flow rate: 1 mL / min], using polystyrene as a standard substance.
(2) Average particle size of water dispersion The particle size was measured using a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and the number of integrations of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measurement concentration was about 5 × 10 ⁻³ wt%, and Uniform Microparticles (average particle size: 204 nm) manufactured by Seradyn was used as a standard substance.
(3) Viscosity of aqueous dispersion The viscosity of the dispersion (solid content: 30% by weight) was measured with a standard rotor (1 ° 34) using an E-type viscometer [manufactured by Toki Sangyo Co., Ltd., model number: RE80 type]. ′ × R24) was used and the measurement temperature was 20 ° C.

(4) Polymer Adsorption Rate of Water Dispersion An aqueous dispersion having a solid content concentration of 30% was diluted to 20% with ion-exchanged water, and 9 g was charged into a centrifuge tube 11PA tube (manufactured by Hitachi Koki Co., Ltd.). Next, it set to centrifuge CR22G (rotor RPR18-3, Hitachi Koki Co., Ltd. product), and centrifuged for 5 hours at 18000 r / min. The supernatant of the treatment liquid after the centrifugal separation was collected, and the polymer adsorption rate for the colorant was determined from the solid content concentration. In addition, since there is a trace amount of pigment in the supernatant of centrifugation, the amount of pigment in the supernatant is measured by taking a calibration curve (pigment concentration and absorbance) in advance and measuring the absorbance of the supernatant. Corrections were made when calculating the polymer amount.
Polymer adsorption rate = (total polymer amount−solid content in centrifuge supernatant (after correction)) / total polymer amount

(5) Print density of ink Using a printer manufactured by Seiko Epson Corporation (model number: EM-930C, piezo method), water-based inks described in the examples are commercially available high-quality plain paper (Xerox Corporation, trade name: XEROX 4200). , US letter size, horizontal 216 mm x vertical 279 mm) (printing condition = paper type: plain paper, mode setting: fine, printing speed: 6 sheets / min), left at 25 ° C for 24 hours, and print density A total of 5 points at the center and four corners of the printed matter (5.1 cm × 8.0 cm) were measured with a Macbeth densitometer (product of Gretag Macbeth, product number: Spectroeye), and the average value was obtained and evaluated according to the following criteria. .
〔Evaluation criteria〕
○: 1.05 or more Δ: 1.04 ×: 1.03 or less

(6) Ink storage stability The screw tube was filled with ink, sealed, and stored in a thermostat at 70 ° C. for 1 week. The average particle diameter and ink viscosity before and after storage were measured by the above (2) and (3), and the values of the average particle diameter change rate (%) and viscosity change rate (%) were determined by the following formulas, and the ink storage stability Sexuality was evaluated. The storage stability is better when the value is closer to 100%.
Change rate of average particle diameter (%) = [[average particle diameter after storage (nm) −average particle diameter before storage (nm)] / [initial average particle diameter (nm)]] × 100
Viscosity change rate (%) = [[viscosity after storage] / [viscosity before storage]] × 100
〔Evaluation criteria〕
○: Both the average particle size change rate (%) and the viscosity change rate (%) are both less than 110%. X: Both the average particle size change rate (%) and the viscosity change rate (%) are both 110% or more.

Production Examples 1 and 2 (Production of water-insoluble polymer)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.05 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of 200 parts of each monomer shown in Table 1 were mixed and mixed, and nitrogen gas substitution was performed sufficiently. A mixed solution was obtained.
On the other hand, the remaining 90% of the monomer shown in Table 1 was charged into a dropping funnel, and 0.45 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone, and a radical polymerization initiator (2,2′-azobis (2,4- Dimethylvaleronitrile)) 1.2 parts were added and mixed, and the gas was sufficiently replaced with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution in which 0.3 part of the radical polymerization initiator was dissolved in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours, and further 115 parts of methyl ethyl ketone. The mixture was stirred for 30 minutes to obtain a polymer solution. The results are shown in Table 1.

The details of the compounds shown in Table 1 are as follows.
(C) 43PAPE-600B
Phenoxy polyethylene glycol polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name: BLEMMER 43PAPE-600B, ethylene oxide average added mole number = 6, propylene oxide average added mole number = 6, terminal: phenyl group)
(C) PP-800
Polypropylene glycol monomethacrylate (Nippon Yushi Co., Ltd., trade name: BLEMMER PP-800, propylene oxide average added mole number = 13, terminal: hydroxyl group)
・ (D) AS-6S
Styrene macromer (manufactured by Toa Gosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group)

Example 1
(1) Preparation of Pigment Dispersion 1029 g of ion-exchanged water and 222 g of methyl ethyl ketone were added to 37 g of a 30.5% aqueous solution of a water-soluble polymer (Johncrill 61J: BASF Japan Ltd., weight average molecular weight 2000) to obtain a polymer aqueous solution.
To the obtained aqueous polymer solution, 214 g of PY74 (CI Pigment Yellow 74, Dainichi Seika Kogyo Co., Ltd., trade name: FY615) was added as a yellow pigment, and mixed at 20 ° C. for 1 hour using a disper blade. A preliminary dispersion (15% non-volatile component ratio calculated based on the above formulas (1) and (A)) was obtained (step (I) preliminary dispersion).
Using 1500 g of the obtained preliminary dispersion, Ultra Apex Mill: Model UAM-05 (Koto Kogyo Co., Ltd., Media Disperser, trade name), using zirconia beads having a particle size of 0.05 mm as media particles 1 hour (total average residence time in the mill: 7.5 minutes) under the conditions of a bead filling rate of 85% by volume, a stirring blade peripheral speed of 8 m / s, and a circulation flow rate of 200 cc / min. A dispersion was obtained (step (I) (a)).
(2) Preparation of water-insoluble polymer emulsion To 105 g of the polymer solution obtained in Production Example 1, 14.7 g of 5N aqueous sodium hydroxide solution, 12.6 g of 25% aqueous ammonia solution and 154 g of ion-exchanged water were added and mixed with a stirrer to obtain a polymer emulsion. Was prepared (step (I) (b)).
Next, while mixing the pigment dispersion obtained in (1) above with a stirrer, the prepared polymer emulsion was added, and the mixture (non-volatile component ratio calculated based on the calculation formula (4) 15%) (Step (I) (c)) was obtained.
(3) Dispersion treatment of pigment dispersion / water-insoluble polymer emulsion mixture The mixture obtained in (2) above was subjected to 5 passes at a pressure of 150 MPa using a microfluidizer (Microfluidics, high-pressure homogenizer, trade name). A dispersion was obtained by a continuous method to obtain a dispersion (step (II)).
(4) Removal of organic solvent The dispersion obtained in (3) above was subjected to removal of methyl ethyl ketone using a hot water heating medium under reduced pressure (step (III)), and a part of water was further removed to remove 5 μm. Filtering with a 25 mL needleless syringe (made by Terumo Corporation) with a filter (acetylcellulose membrane, outer diameter: 2.5 cm, made by Fuji Film Co., Ltd.) to remove coarse particles, solid content concentration 30 % Aqueous dispersion was obtained.
(5) Preparation of water-based ink To 62.5 parts of the obtained water dispersion, 10 parts of water, 26.2 parts of triethylene glycol monobutyl ether, 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 0.3 parts (Avisia Co., Ltd.) was mixed so that the water content was 60%.
The obtained liquid mixture was similarly filtered with the said 5 micrometer filter and a syringe without a needle | hook, and the water-based ink was obtained by removing a coarse particle. The results are shown in Table 2.

Example 2
In step (I) (a), the polymer aqueous solution was changed to 43.5 g, ion-exchanged water 1025 g, and methyl ethyl ketone 222 g. In step (I) (b), the polymer solution was 99.4 g, 5N aqueous sodium hydroxide solution. The same operation as in Example 1 was performed, except that 13.8 g, 25% aqueous ammonia solution was changed to 11.9 g, and ion-exchanged water was changed to 145 g. The results are shown in Table 2.
Example 3
In step (I) (a), the polymer aqueous solution was changed to 56.6 g, ion-exchanged water 1016 g, and methyl ethyl ketone 222 g. In step (I) (b), the polymer solution was 86.3 g, 5N aqueous sodium hydroxide solution. The same operation as in Example 1 was performed, except that 12.0 g, 25% aqueous ammonia solution was changed to 10.3 g, and ion-exchanged water was changed to 126 g. The results are shown in Table 2.

Example 4
In step (I) (b), the polymer solution obtained in Production Example 1 was changed to the polymer obtained in Production Example 2, and the amount of 5N sodium hydroxide aqueous solution used was 11.9 g, 25% aqueous ammonia solution. The same operation as in Example 1 was performed except that the amount used was changed to 10.2 g. The results are shown in Table 2.
Example 5
In Step (I) (a), the same operation as in Example 1 was performed except that the bead mill dispersion residence time was changed to 13 minutes. The results are shown in Table 2.

Comparative Example 1
In the step (I) (a), the polymer aqueous solution was changed to 147.5 g, the ion exchange water was changed to 1028 g, the methyl ethyl ketone was changed to 144.2 g and the yellow pigment was changed to 180 g, and the steps (I), (b) and (c) were omitted. Except that, the same operation as in Example 1 was performed. The results are shown in Table 2.
Comparative Example 2
In step (I) (a), the polymer solution obtained in Production Example 1 was used instead of the polymer aqueous solution, the amount was 112.3 g, methyl ethyl ketone was 100.9 g, and 5N sodium hydroxide aqueous solution was 15.6 g. 13.5 g of 25% aqueous ammonia solution, 1099 g of ion-exchanged water, 180 g of yellow pigment were added, and the same operations as in Example 1 were performed except that steps (I), (b), and (c) were omitted. It was. The results are shown in Table 2.

Comparative Example 3
Except that the emulsion obtained in Step (I) (b) was not prepared in the step (I) (b), and the polymer solution obtained in Production Example 1 was added to the dispersion obtained in Step (I) (a) as a polymer MEK solution. The same operation as in Example 1 was performed. As a result, the dispersion was aggregated and gelled, and the intended ink was not obtained.
Comparative Example 4
Steps (I) and (b) were not performed, and the same operation as in Example 1 was performed except that all raw materials were added from the beginning. The results are shown in Table 2.
Comparative Example 5
The same operation as in Example 1 was performed except that the step (II) was omitted. The results are shown in Table 2.
Comparative Example 6
The same operation as in Example 1 was performed except that the organic solvent was removed from the polymer emulsion obtained in the steps (I) and (b), and ion-exchanged water was added in the removed amount. The results are shown in Table 2.

  From Table 2, it can be seen that the water-based inks of Examples 1 to 5 are excellent in print density and storage stability. On the other hand, the water-based inks of Comparative Examples 1, 2, and 6 have a low print density. In Comparative Examples 3 and 5, the ink is agglomerated and gelated. In Comparative Examples 1, 4, and 6, the ink storage stability is poor. The intended ink was not obtained.

Claims (7)

The manufacturing method of the aqueous dispersion for inkjet recording which has the following process (I)-(III).
Step (I): Step of mixing a colorant dispersion and a water-insoluble polymer emulsion containing an organic solvent Step (II): The mixture obtained in Step (I) was dispersed and the water-insoluble polymer adhered to the colorant. Step of obtaining dispersion Step (III): Step of removing the organic solvent from the dispersion obtained in Step (II)   The method for producing an aqueous dispersion for inkjet recording according to claim 1, wherein the colorant dispersion is a dispersion containing at least a colorant, a water-soluble polymer and water.   The manufacturing method of the water dispersion for inkjet recording of Claim 1 or 2 whose colorant dispersion is a pigment dispersion disperse | distributed using the media-type disperser.   The water-insoluble polymer emulsion is an emulsion composition comprising a water-insoluble polymer having a salt-forming group, an organic solvent having a solubility in water at 20 ° C of 5 to 40% by weight, a neutralizing agent and water. 4. A method for producing an aqueous dispersion for ink jet recording according to any one of 3 above.   The manufacturing method of the water dispersion for inkjet recording in any one of Claims 2-4 whose weight ratio of (water-soluble polymer / water-insoluble polymer) is 2/1-1/5.   An aqueous dispersion for ink jet recording obtained by the production method according to claim 1.   A water-based ink for ink-jet recording, comprising the water dispersion according to claim 6.