JP2021020143A - Polymer dispersant, colorant dispersion liquid, and ink composition - Google Patents

Abstract

To provide a polymer dispersant that can improve the dispersion stability of the colorant in a colorant dispersion liquid and suppress the gelation of the colorant dispersion liquid.SOLUTION: A polymer dispersant according to the present invention has a hydrophobic block and a hydrophilic block. The hydrophilic block includes a structural unit derived from a first hydrophilic monomer and a structural unit derived from a second hydrophilic monomer. The structural unit derived from the first hydrophilic monomer and the structural unit derived from the second hydrophilic monomer are arranged at random.SELECTED DRAWING: None

Description

The present invention relates to a polymer dispersant, a color material dispersion, and an ink composition.

Color material dispersion is an important process in the production of paints and inks. The quality of color material dispersion depends on the optical properties such as gloss, coloring power, and hiding power of the product, the rheological properties such as viscosity, fluidity, leveling property, and flow property, and the time such as sedimentation, aggregation, and generation of lumps. Affects stability, etc.

Therefore, a technique of coating a coloring material contained in a paint or an ink with a polymer dispersant has been proposed. For example, Patent Document 1 describes a pigment dispersion liquid in which a pigment is dispersed in a block copolymer having a hydrophobic block segment, a nonionic hydrophilic segment, and an ionic hydrophilic segment, and an ink ink obtained by using the pigment dispersion liquid. Recording inks are disclosed.

JP-A-2010-222405

However, while the block copolymer described in Patent Document 1 can obtain stable dispersion, it forms a strong inclusion structure that takes in water, so that the ink tends to gel easily.

One aspect of the polymer dispersant according to the present invention is
A polymer dispersant having a hydrophobic block and a hydrophilic block.
The hydrophilic block contains a structural unit derived from a first hydrophilic monomer and a structural unit derived from a second hydrophilic monomer, and a structural unit derived from the first hydrophilic monomer and the second hydrophilic monomer. Structural units derived from the hydrophilic monomers of the above are randomly arranged.

In one aspect of the polymer dispersant,
The first hydrophilic monomer may be an ionic monomer, and the second hydrophilic monomer may be a nonionic monomer.

In any of the above polymer dispersants,
The ionic monomer may be an unsaturated carboxylic acid.

In any of the above polymer dispersants,
The ionic monomer may be (meth) acrylic acid.

In any of the above polymer dispersants,
The nonionic monomer may be a monomer represented by the following general formula (1).

（式（１）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^２はメチル基、オキシエチレン基が２以上連結しているポリオキシエチレンアルキルエーテル基またはヒドロキシアルキル基を表す。）

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a polyoxyethylene alkyl ether group or a hydroxyalkyl group in which two or more methyl groups and oxyethylene groups are linked.)

In any of the above polymer dispersants,
The nonionic monomer may be at least one selected from the group consisting of ethoxyethoxyethyl (meth) acrylate and methyl (meth) acrylate.

In any of the above polymer dispersants,
The hydrophobic block may have a structural unit derived from a hydrophobic monomer represented by the following general formula (2).

（式（２）中、Ｒ^３は水素原子またはメチル基を表し、Ｘは、分岐していてもよい炭素数２以上のアルキルエステル基、置換もしくは非置換の、アリール基、ピリジル基またはアリールオキシエチルエステル基を表す。）

In formula (2), R ³ represents a hydrogen atom or a methyl group, and X is a branched alkyl ester group having 2 or more carbon atoms, a substituted or unsubstituted aryl group, a pyridyl group or an aryloxy. Represents an ethyl ester group.)

In any of the above polymer dispersants,
At least the hydrophobic monomer is selected from the group consisting of styrene, butyl (meth) acrylate, -2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, and vinylpyridine. It may be one kind.

In any of the above polymer dispersants,
The number average molecular weight (Mn) measured by gel permeation chromatography may be 8,000 to 20,000.

One aspect of the color material dispersion liquid according to the present invention is
It contains a coloring material, an aqueous medium, and a polymer dispersant of any of the above embodiments.

One aspect of the ink composition according to the present invention is
Contains the colorant dispersion of the above aspect.

An embodiment of the present invention will be described below. The embodiments described below describe examples of the present invention. The present invention is not limited to the following embodiments, and includes various modifications implemented without changing the gist of the present invention. It should be noted that not all of the configurations described below are essential configurations of the present invention.

In the present specification, "(meth) acrylic" means each of acrylic and methacrylic, and "(meth) acrylate" means each of acrylate and methacrylate.

1. 1. Polymer dispersant The polymer dispersant according to an embodiment of the present invention has a hydrophobic block and a hydrophilic block, and the hydrophilic block includes a structural unit derived from a first hydrophilic monomer and a structural unit. A structural unit derived from the second hydrophilic monomer is included, and a structural unit derived from the first hydrophilic monomer and a structural unit derived from the second hydrophilic monomer are randomly arranged.

Some conventional polymer dispersants have a hydrophobic block and a hydrophilic block. When the hydrophilic part of the polymer dispersant is a hydrophilic block, the structural units derived from the hydrophilic monomer are concentrated in the hydrophilic block, so that the polymer has a localized part. A phase-separated structure is likely to be formed in the color material dispersion liquid containing such a polymer dispersant, and the polymer dispersant forms a strong intermolecular interaction while taking in water, so that it gels. Tend. In particular, when such a polymer dispersant is dissolved or dispersed in an alkaline aqueous solution, it easily gels.

On the other hand, in the hydrophilic block of the polymer dispersant according to the present embodiment, structural units derived from the first hydrophilic monomer and structural units derived from the second hydrophilic monomer are randomly arranged. .. As a result, in the color material dispersion liquid containing such a polymer dispersant, the polymer dispersant can weaken the intermolecular interaction while maintaining the interaction with water, so that gelation occurs. Can be suppressed.

Further, the polymer dispersant according to the present embodiment has a hydrophobic block and a hydrophilic block, so that the coloring material can be stably dispersed in the aqueous medium.

Hereinafter, the structure, synthesis method, molecular weight, and use of the polymer dispersant according to the present embodiment will be described.

1.1. Structure 1.1.1. Hydrophilic block The hydrophilic block is a part having a low affinity for a coloring material and has an excellent affinity for an aqueous medium. The hydrophilic block contains a structural unit derived from the first hydrophilic monomer and a structural unit derived from the second hydrophilic monomer, and the structural unit derived from the first hydrophilic monomer and the second hydrophilic monomer. Structural units derived from hydrophilic monomers are randomly arranged.

The first hydrophilic monomer is preferably an ionic monomer. Further, the second hydrophilic monomer is preferably a nonionic monomer. Since the first hydrophilic monomer is an ionic monomer and the second hydrophilic monomer is a non-ionic monomer, one polymer dispersant has both ionic and non-ionic properties. You will be able to do it. As a result, the stabilization of the color material dispersion liquid is likely to be improved, and the sedimentation of the color material can be effectively suppressed.

The ionic monomer is not particularly limited, but is preferably an unsaturated carboxylic acid. Specific examples of the unsaturated carboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, etc., and the dispersibility of the coloring material is improved and the structural unit is introduced into the polymer dispersant. From the viewpoint of ease, (meth) acrylic acid is particularly preferable. These ionic monomers may be used alone or in combination of two or more.

The lower limit of the proportion of the structural unit derived from the ionic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 5 mol%, more preferably 8 mol%, and particularly preferably 10 mol. %. The upper limit of the proportion of the structural unit derived from the ionic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 40 mol%, more preferably 35 mol%, and particularly preferably 30 mol. %. When the ratio of the constituent units derived from the ionic monomer is within the above range, the intermolecular interaction can be weakened while maintaining the interaction with water, so that the effect of suppressing gelation is improved.

It is considered that the nonionic monomer has a function of providing a strong three-dimensional repulsive force between the color material particles and suppressing aggregation between the color material particles. The nonionic monomer is not particularly limited, but is preferably a monomer represented by the following general formula (1).

（式（１）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^２はメチル基、オキシエチレン基が２以上連結しているポリオキシエチレンアルキルエーテル基またはヒドロキシアルキル基を表す。）

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a polyoxyethylene alkyl ether group or a hydroxyalkyl group in which two or more methyl groups and oxyethylene groups are linked.)

Examples of the monomer represented by the general formula (1) include methyl (meth) acrylate, 2-ethoxyethoxymethyl (meth) acrylate, 2-ethoxyethoxyethyl (meth) acrylate, and methoxypolyethylene glycol (meth). ) Acrylate, ethoxypolyethylene glycol (meth) acrylate, 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate And so on. Among these, at least one selected from the group consisting of ethoxyethoxyethyl (meth) acrylate and methyl (meth) acrylate is preferable. These nonionic monomers may be used alone or in combination of two or more.

The lower limit of the proportion of the structural unit derived from the nonionic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 5 mol%, more preferably 8 mol%, and particularly preferably 8 mol%. It is 10 mol%. The upper limit of the proportion of the structural unit derived from the ionic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 40 mol%, more preferably 35 mol%, and particularly preferably 30 mol. %. When the ratio of the constituent units derived from the nonionic monomer is within the above range, the intermolecular interaction can be weakened while maintaining the interaction with water, so that the effect of suppressing gelation is improved. , Aggregation between coloring material particles can also be suppressed.

1.1.2. Hydrophobic block A hydrophobic block is a site that shows an affinity for coloring materials. Hydrophobic blocks contain structural units derived from hydrophobic monomers.

Such a hydrophobic monomer is not particularly limited, but is preferably a monomer represented by the following general formula (2).

（式（２）中、Ｒ^３は水素原子またはメチル基を表し、Ｘは、分岐していてもよい炭素数２以上のアルキルエステル基、置換もしくは非置換の、アリール基、ピリジル基またはアリールオキシエチルエステル基を表す。）

In formula (2), R ³ represents a hydrogen atom or a methyl group, and X is a branched alkyl ester group having 2 or more carbon atoms, a substituted or unsubstituted aryl group, a pyridyl group or an aryloxy. Represents an ethyl ester group.)

Specific examples of the compound represented by the general formula (2) include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and the like. (Meta) acrylic acid esters such as isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate; aryloxy such as phenoxyethyl (meth) acrylate Ethyl ester group; styrene-based monomers such as styrene, α-methylstyrene, p-methylstyrene; vinylpyridine and the like can be mentioned. Among these, at least one selected from the group consisting of styrene, butyl (meth) acrylate, -2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, and vinylpyridine. Is preferable. These hydrophobic monomers may be used alone or in combination of two or more.

The lower limit of the proportion of the structural unit derived from the hydrophobic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 30 mol%, more preferably 35 mol%, and particularly preferably 40 mol. %. The upper limit of the proportion of the structural unit derived from the ionic monomer in all the structural units constituting the polymer dispersant according to the present embodiment is preferably 80 mol%, more preferably 70 mol%, and particularly preferably 65 mol. %. When the proportion of the structural unit derived from the nonionic monomer is within the above range, the stabilization of the color material dispersion liquid is likely to be improved, and the sedimentation of the color material can be effectively suppressed.

1.2. Synthesis Method The polymer dispersant according to the present embodiment is composed of a hydrophobic segment formed by polymerizing a hydrophobic monomer, and a random polymerization of a first hydrophilic monomer and a second hydrophilic monomer. It can be synthesized by binding to a hydrophilic segment.

The method for synthesizing the block copolymer is not particularly limited, and various methods can be used, but it is preferable to synthesize the block copolymer by the living radical polymerization method.

In the block copolymer obtained by the living radical polymerization method, the hydrophobic segment and the hydrophilic segment are clearly classified as compared with the ordinary block copolymer, and the characteristics of each segment are easily exhibited.

As a result, the adhesiveness of the obtained polymer dispersant to the coloring material and the affinity to the water-based medium can be made more excellent, and the color material can be dispersed in the water-based medium. The dispersion stability and the storage stability of the dispersion liquid containing the coloring material can be made more excellent.

Hereinafter, a method for synthesizing a polymer dispersant according to the present embodiment using butyl acrylate as a hydrophobic monomer, acrylic acid as a first hydrophilic monomer, and ethoxyethoxyethyl acrylate as a second hydrophilic monomer. explain.

First, butyl acrylate is polymerized by RAFT polymerization in the presence of a RAFT agent, a radical initiator and a solvent. RAFT polymerization is one of the controlled living radical polymerization methods, and can synthesize a polymer having a narrow molecular weight distribution.

Examples of the RAFT agent include 2-(((carboxymethyl) sulfanylthiocarbonyl) sulfanyl) propanoic acid, 2-(((dodecylthio) carbonothio oil) thio) propanoic acid, 3-((((1-carboxyethyl)). ) Thio) Carbonothio oil) Thio) Proanoic acid, 4-cyano-4-(((Dodecylthio) Carbonoti oil) Thio) Pentanoic acid, Bis (Dodecylsulfanylthiocarbonyl) disulfide, Cyanmethyl (3,5-dimethyl-1H -Pyrazole) -carbodithioate, dibenzyltrithiocarbonate, methyl-4-cyano-4- (dodecylthiocarbonothio oilthio) pentanate and the like can be used.

The radical initiator is not particularly limited, and is an azo compound such as azobisisobutyronitrile and 1,1'-azobis (cyclohexanecarbonitrile); di-tert-butylperoxide, tert-butylhydroperoxide, benzoyl peroxide. , Methylethylketone Peroxide and other peroxides; In addition to dihalogen, triethylborane, diethylzinc and the like, hydrogen peroxide and iron (II) salt, persulfate and sodium hydrogen sulfite and other oxidizing and reducing agents are combined. Can also be used.

Then, using the obtained polymer as a macro RAFT agent, acrylic acid, ethoxyethoxyethyl acrylate, a radical initiator, and a solvent were further added for polymerization, and the resulting polymer was obtained from a random copolymer of acrylic acid and ethoxyethoxyethyl acrylate. A block copolymer having a hydrophilic block and a hydrophobic block made of a polymer of butyl acrylate can be obtained. As the radical initiator, those exemplified above can be used.

1.3. Number Average Molecular Weight and Dispersion Ratio The lower limit of the number average molecular weight (Mn) of the polymer dispersant according to the present embodiment is preferably 8,000, more preferably 9,000, and particularly preferably 10,000. is there. The upper limit of the number average molecular weight (Mn) of the polymer dispersant according to the present embodiment is preferably 20,000, more preferably 18,000, and particularly preferably 16,000. When the number average molecular weight (Mn) of the polymer dispersant is within the above range, the dispersion stability of the color material and the storage stability of the dispersion liquid containing the color material when the color material is dispersed in an aqueous medium are improved. It can be made better. Further, when the polymer dispersant according to the present embodiment is used in an ink composition described later, the ejection stability by the inkjet method can be further improved. The number average molecular weight (Mn) of the polymer dispersant refers to the polystyrene-equivalent number average molecular weight measured by gel permeation chromatography (GPC).

Further, the weight average molecular weight (Mw) / number average molecular weight (Mn), so-called dispersion ratio, of the polymer dispersant according to the present embodiment is preferably 1.1 to 2.0, and 1.1 to 1. It is preferably 8 and more preferably 1.1 to 1.5. Generally, the value of the dispersion ratio is considered to mean the spread of the molecular weight distribution, and the closer this value is to 1, the narrower the molecular weight distribution is. Since the polymer dispersant according to the present embodiment has a spread of molecular weight distribution within the above range, the dispersion stability of the color material and the dispersion liquid containing the color material when the color material is dispersed in an aqueous medium The storage stability of the product can be improved.

1.4. Applications The polymer dispersant according to the present embodiment can be used as a dispersant for dispersing solid particles such as inorganic particles and organic particles in an aqueous medium. The inorganic particles are not particularly limited, and examples thereof include inorganic oxide particles such as silica, titania, and alumina. Examples of the organic particles include coloring materials such as pigments and dyes, as well as organic particles having a hydrophobic surface. Among these, since gelation due to the addition of a polymer dispersant can be suppressed, it is particularly preferable to use it as a dispersant for coloring materials such as pigments and dyes used in aqueous inkjet inks.

2. 2. Color Material Dispersion Liquid Next, the color material dispersion liquid according to the embodiment of the present invention will be described.

The color material dispersion liquid according to the present embodiment contains a color material, an aqueous medium, and the above-mentioned polymer dispersant. Since the color material dispersion liquid according to the present embodiment contains the above-mentioned polymer dispersant, it is excellent in dispersion stability and storage stability of the color material, and can suppress gelation.

In the present specification, the color material dispersion liquid refers to a liquid in which the color material is dispersed in a dispersion medium, and is a concept including, for example, an undiluted solution of ink used for producing an ink composition described later.

<Color material>
Examples of the coloring material include various pigments and various disperse dyes. Such a coloring material is generally highly hydrophobic, and when the above-mentioned polymer dispersant is applied, it has excellent adhesion to the hydrophobic segment of the polymer dispersant. Therefore, the above-mentioned effects are exhibited.

Examples of the pigment include black pigments such as carbon black; I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60, C.I. I. Cyan pigments such as Bat Blue 4, 60; C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, C.I. I. Magenta pigments such as Pigment Violet 19; C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 150, 151, Yellow pigments such as 154, 155, 180, 185; C.I. I. Pigment Orange 36, 43 and other orange pigments; C.I. I. Examples thereof include green pigments such as Pigment Green 7 and 36.

Examples of the disperse dye include C.I. I. Disperse Yellow 3, 7, 8, 23, 39, 51, 54, 60, 71, 86; C.I. I. Disperse Orange 1, 1: 1, 5, 20, 25, 25: 1, 33, 56, 76; C.I. I. Disperse Brown 2; C.I. I. Disperse Red 11, 50, 53, 55, 55: 1, 59, 60, 65, 70, 75, 93, 146, 158, 190, 190: 1, 207, 239, 240; I. Bat Red 41; C.I. I. Disperse Violet 8, 17, 23, 27, 28, 29, 36, 57; C.I. I. Disperse Blue 19, 26, 26: 1, 35, 55, 56, 58, 64, 64: 1, 72, 72: 1, 81, 81: 1, 91, 95, 108, 131, 141, 145, 359 C. I. Examples thereof include Solvent Blue 36, 63, 105 and 111.

The color material dispersion liquid according to the present embodiment may contain a plurality of types of color materials.

The lower limit of the content of the coloring material in the coloring material dispersion liquid according to the present embodiment is preferably 0.2% by mass, more preferably 0.3% by mass, and particularly preferably 0.5% by mass. is there. The upper limit of the content of the coloring material in the coloring material dispersion liquid according to the present embodiment is preferably 30% by mass, more preferably 25% by mass, and particularly preferably 20% by mass.

When the content of the coloring material is within the above range, more excellent color developing property can be obtained, and the dispersion stability of the coloring material and the storage stability of the coloring material dispersion liquid in the coloring material dispersion liquid are further improved. Further, when an ink for an inkjet is manufactured using this color material dispersion liquid, particularly excellent ejection stability can be obtained.

<Polymer dispersant>
The color material dispersion liquid according to the present embodiment contains the above-mentioned polymer dispersant. As a result, the above-mentioned effect can be obtained. The color material dispersion liquid according to the present embodiment may contain a plurality of types of polymer dispersants.

The lower limit of the content of the polymer dispersant in the color material dispersion liquid according to the present embodiment is preferably 0.2% by mass, more preferably 0.3% by mass, and particularly preferably 0.4% by mass. %. The upper limit of the content of the polymer dispersant in the color material dispersion liquid according to the present embodiment is preferably 30% by mass, more preferably 20% by mass, and particularly preferably 15% by mass.

When the content of the polymer dispersant in the color material dispersion liquid according to the present embodiment is within the above range, the dispersion stability of the color material and the storage stability of the color material dispersion liquid in the color material dispersion liquid are further improved. To do. Further, when this color material dispersion liquid is applied to an ink composition described later, the ejection stability by the inkjet method can be made more excellent.

When the content of the coloring material in the color material dispersion liquid according to the present embodiment is XD [mass%] and the content of the polymer dispersant is XB [mass%], the lower limit of XB / XD is preferably It is 0.3, more preferably 0.5, and particularly preferably 0.6. The upper limit of XB / XD is preferably 2.0, more preferably 1.5, and particularly preferably 1.2.

By satisfying such a relationship, the dispersion stability of the coloring material and the storage stability of the coloring material dispersion liquid are further improved. Further, when the color material dispersion liquid is applied to an ink composition described later, the ejection stability by the inkjet method can be made more excellent.

<Aqueous medium>
The color material dispersion liquid according to the present embodiment contains an aqueous medium. Examples of the aqueous medium include a mixed medium of water, water and a hydrophilic solvent. The hydrophilic solvent refers to a solvent having a solubility in water at 25 ° C. of 10 g / 100 g or more.

The lower limit of the water content in the color material dispersion liquid according to the present embodiment is not particularly limited, but is preferably 30% by mass, more preferably 35% by mass, and particularly preferably 40% by mass. The upper limit of the water content in the color material dispersion liquid according to the present embodiment is not particularly limited, but is preferably 85% by mass, more preferably 80% by mass, and particularly preferably 75% by mass. is there. Thereby, the viscosity of the color material dispersion liquid can be more reliably adjusted to a suitable value.

Further, since the color material dispersion liquid according to the present embodiment contains a hydrophilic solvent as a solvent other than water, the viscosity of the color material dispersion liquid can be suitably adjusted. In addition, the moisturizing property of the color material dispersion liquid can be enhanced. As a result, when the color material dispersion liquid is applied to an ink composition, particularly an ink composition for an inkjet, droplet ejection by the inkjet method can be performed more stably.

The hydrophilic solvent is a liquid substance by itself at room temperature (25 ° C.), and the lower limit of its standard boiling point is preferably 180 ° C., more preferably 185 ° C., and particularly preferably 190 ° C. The upper limit of the standard boiling point of the hydrophilic solvent is preferably 320 ° C., more preferably 310 ° C., and particularly preferably 300 ° C.

Examples of such a hydrophilic solvent include glycerin, propylene glycol, 2-pyrrolidone and the like. By containing these hydrophilic solvents, the evaporation rate can be slowed down due to the excellent moisturizing ability, and more stable droplet ejection can be performed in the ink composition to which the color material dispersion liquid according to the present embodiment is applied. It can be carried out. The color material dispersion liquid according to the present embodiment may contain a plurality of types of solvents as hydrophilic solvents.

The lower limit of the content of the hydrophilic solvent in the color material dispersion liquid according to the present embodiment is preferably 0% by mass, more preferably 10% by mass, and particularly preferably 15% by mass. The upper limit of the content of the hydrophilic solvent in the color material dispersion liquid according to the present embodiment is preferably 45% by mass, more preferably 43% by mass, and particularly preferably 40% by mass. As a result, the effect of containing the above-mentioned hydrophilic solvent is more remarkable.

<Surfactant>
The color material dispersion liquid according to the present embodiment may contain a surfactant. Thereby, the wettability of the color material dispersion liquid and the ink composition to which the color material dispersion liquid is applied to the recording medium can be made more suitable. As a result, for example, the image quality of the image formed by using the ink composition can be improved.

As such a surfactant, for example, various surfactants such as an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. More specifically, such surfactants include acetylene-based surfactants, silicone-based surfactants, fluorine-based surfactants, and the like.

When the color material dispersion liquid according to the present embodiment contains a silicone-based surfactant, the wettability of the color material dispersion liquid and the ink composition to which the color material dispersion liquid is applied can be made more suitable for the recording medium. The above-mentioned effects are more prominently exhibited.

When the color material dispersion liquid according to the present embodiment contains a silicone-based surfactant, the lower limit of the content of the silicone-based surfactant is preferably 5.0 parts by mass with respect to 100 parts by mass of the color material. It is more preferably 7.0 parts by mass, and particularly preferably 10 parts by mass. The upper limit of the content of the silicone-based surfactant is preferably 150 parts by mass, more preferably 140 parts by mass, and particularly preferably 70 parts by mass with respect to 100 parts by mass of the coloring material. As a result, the effect of containing the above-mentioned silicone-based surfactant is more remarkable.

Examples of commercially available silicone-based surfactants include BYK-306, BYK-307, BYK-333, BYK-337, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-. 349, BYK-378 (trade name, manufactured by Big Chemie Japan), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF -643, KF-945, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

<Other ingredients>
The color material dispersion liquid according to the present embodiment may contain components other than the above-mentioned components. Examples of other components include dispersants other than the polymer dispersant, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, diethylene glycol monomethyl ether, 1,2-hexanediol, 1,2-pentanediol, and 1, Penetrants such as 2-butanediol and 3-methyl1,5-pentanediol, pH adjusters, chelating agents such as ethylenediaminetetraacetic acid (EDTA), preservatives / antifungal agents, rust preventives, antioxidants , UV absorbers, oxygen absorbers, solubilizers, ureas and the like. As the preservative / fungicide, for example, a compound having an isothiazolin ring structure in the molecule can be preferably used.

The lower limit of the viscosity of the color material dispersion liquid according to the present embodiment at 25 ° C. is preferably 2 mPa · s, more preferably 3 mPa · s, and particularly preferably 4 mPa · s. The upper limit of the viscosity of the color material dispersion liquid according to the present embodiment at 25 ° C. is preferably 30 mPa · s, more preferably 20 mPa · s, and particularly preferably 15 mPa · s. As a result, the fluidity of the color material dispersion liquid can be made appropriately excellent. Further, in the ink composition to which the color material dispersion liquid according to the present embodiment is applied, it is easy to adjust the ejection stability by the inkjet method so as to be good.

The viscosity is determined by reading the viscosity at 25 ° C. using a viscoelasticity tester (for example, MCR-300 manufactured by Pysica) when the shear rate is 10 [s- ¹ ]. Can be measured.

3. 3. Ink Composition Next, an ink composition according to an embodiment of the present invention will be described.

The ink composition according to this embodiment contains the above-mentioned color material dispersion liquid. Thereby, it is possible to provide an ink composition which is excellent in dispersion stability and storage stability of the coloring material and in which gelation is suppressed.

The ink composition according to the present embodiment may be an ink composition obtained by using the above-mentioned color material dispersion as it is, or by adding another component such as a diluting solvent to the above-mentioned color material dispersion. It may be prepared, or it may be prepared by mixing two or more kinds of the above-mentioned color material dispersions.

The ink composition according to the present embodiment is a water-based ink composition, and it is particularly preferable that the ink composition is a water-based inkjet ink composition.

Since the ink composition according to the present embodiment is excellent in dispersion stability and storage stability of the coloring material, it effectively prevents unintentional aggregation and sedimentation of the coloring material even when stored for a long period of time. can do. As a result, even when ejection is performed by the inkjet method, ejection defects and the like are unlikely to occur. Therefore, when the present invention is applied to an ink composition for an inkjet, the effect of the present invention is more remarkably exhibited. The ink composition according to this embodiment may contain a plurality of types of polymer dispersants.

The lower limit of the content of the polymer dispersant in the ink composition according to the present embodiment is preferably 0.1% by mass, more preferably 0.2% by mass, and particularly preferably 0.4% by mass. Is. The upper limit of the content of the polymer dispersant is preferably 30% by mass, more preferably 18% by mass, and particularly preferably 10% by mass. When the content of the polymer dispersant is within the above range, the dispersion stability of the coloring material in the ink composition and the storage stability of the ink composition are further improved. Further, when this ink composition is used as an ink for an inkjet, particularly excellent ejection stability can be obtained.

The lower limit of the content of the coloring material in the ink composition according to the present embodiment is preferably 0.1% by mass, more preferably 0.3% by mass, and particularly preferably 0.5% by mass. .. The upper limit of the content of the coloring material is preferably 30% by mass, more preferably 15% by mass, and particularly preferably 8.0% by mass. When the content of the color material is within the above range, more excellent color development property can be obtained, and the dispersion stability of the color material and the storage stability of the ink in the ink composition are further improved. Further, when this ink composition is used as an ink composition for an inkjet, particularly excellent ejection stability can be obtained.

When the content of the coloring material in the ink composition is XD [mass%] and the content of the polymer dispersant is XB [mass%], the relationship of 0.3 ≦ XB / XD ≦ 2.0 is satisfied. It is more preferable that the relationship of 0.5 ≦ XB / XD ≦ 1.5 is satisfied, and it is more preferable that the relationship of 0.6 ≦ XB / XD ≦ 1.2 is satisfied. By satisfying such a relationship, the dispersion stability of the coloring material and the storage stability of the ink composition are further improved. Further, when this ink composition is used as an ink for an inkjet, particularly excellent ejection stability can be obtained.

<Aqueous medium>
The ink composition according to this embodiment contains an aqueous medium. Examples of the aqueous medium include a mixed medium of water, water and a hydrophilic solvent. As the hydrophilic solvent, those described as the constituent components of the color material dispersion liquid can be preferably used.

The lower limit of the water content in the ink composition according to the present embodiment is not particularly limited, but is preferably 40% by mass, more preferably 45% by mass, and particularly preferably 50% by mass. The upper limit of the water content is not particularly limited, but is preferably 85% by mass, more preferably 80% by mass, and particularly preferably 75% by mass. Thereby, the viscosity of the ink composition can be more reliably adjusted to a suitable value. Further, when this ink composition is used as an ink composition for an inkjet, particularly excellent ejection stability can be obtained.

The lower limit of the content of the hydrophilic solvent in the ink composition according to the present embodiment is preferably 0% by mass, more preferably 10% by mass, and particularly preferably 15% by mass. The upper limit of the content of the hydrophilic solvent is preferably 45% by mass, more preferably 43% by mass, and particularly preferably 40% by mass. As a result, the effect of containing the above-mentioned hydrophilic solvent is more remarkable.

<Surfactant>
The ink composition according to this embodiment may contain a surfactant. Thereby, the wettability of the ink composition with respect to the recording medium can be made more suitable. As a result, for example, the image quality of the image formed by using the ink composition can be improved.

As the surfactant, those described as constituents of the colorant dispersion can be preferably used. As a result, the same effect as described above can be obtained.

When the ink composition according to the present embodiment contains a silicone-based surfactant, the lower limit of the content of the silicone-based surfactant in the ink composition is preferably 5 with respect to 100 parts by mass of the coloring material. It is 0.0 parts by mass, more preferably 7.0 parts by mass, and particularly preferably 10 parts by mass. The upper limit of the content of the silicone-based surfactant in the ink composition is preferably 150 parts by mass, more preferably 140 parts by mass, and particularly preferably 70 parts by mass with respect to 100 parts by mass of the coloring material. It is a mass part. As a result, the effect of containing the above-mentioned silicone-based surfactant is more remarkable.

<Other ingredients>
The ink composition according to the present embodiment may contain components other than the above-mentioned components. As the other components, for example, those described as the constituent components of the color material dispersion liquid can be preferably used.

The lower limit of the surface tension of the ink composition according to the present embodiment at 25 ° C. is preferably 20 mN / m, more preferably 21 mN / m, and particularly preferably 23 mN / m. The upper limit of the surface tension is preferably 50 mN / m, more preferably 40 mN / m, and particularly preferably 30 mN / m. As a result, clogging of the nozzle of the droplet ejection head is less likely to occur, and the ejection stability of the ink composition is further improved. Further, even when the nozzle is clogged, the recovery by capping the nozzle (capping) can be made more excellent.

As the surface tension, a value measured by the Wilhelmy method can be adopted. A surface tension meter (for example, manufactured by Kyowa Interface Science Co., Ltd., CBVP-7, etc.) can be used for measuring the surface tension.

The lower limit of the viscosity of the ink composition according to the present embodiment at 25 ° C. is preferably 2 mPa · s, more preferably 3 mPa · s, and particularly preferably 4 mPa · s. The upper limit of the viscosity is preferably 10 mPa · s, more preferably 8 mPa · s, and particularly preferably 6 mPa · s. Thereby, the fluidity of the ink composition can be made appropriately excellent. Further, when the ink composition according to the present embodiment is used as an ink composition for an inkjet, particularly excellent ejection stability can be obtained.

The ink composition according to the present embodiment is usually applied to various recording devices, for example, a recording device by an inkjet method, in a state of being stored in a container such as a cartridge, a bag, or a tank.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

For example, in the above-described embodiment, the case where the above-mentioned color material dispersion liquid is used as the ink composition or its stock solution has been mainly described, but the use of the above-mentioned color material dispersion liquid is not limited to these, and for example, a paint. May be used as.

4. Examples Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. Hereinafter, "%" is based on mass unless otherwise specified.

4.1. Example 1
(Synthesis of Polymer Dispersant A)
Butyl acrylate 13.1 g (102 mmol), 2-(((carboxymethyl) sulfanylthiocarbonyl) sulfanyl) propanoic acid 0.65 g (2.56 mmol), azobisisobutyronitrile 0.33 g (2.01 mmol), And 5 mL of toluene was added to the flask with a branch, and after freeze degassing was performed 3 times, the mixture was stirred at 75 ° C. for 4 hours. The reaction solution was vacuum dried to remove the solvent and residual monomers. The yield of the obtained polymer was 10.24 g.
Subsequently, 7.53 g (40 mmol) of ethoxyethoxyethyl acrylate, 2.92 g (40.5 mmol) of acrylic acid, and 0 azobisisobutyronitrile were added to the obtained polymer.
.. 26 g (1.60 mmol) and 5 mL of N, N-dimethylformamide were added, freeze-degassed three times, and heated at 75 ° C. for 2 hours. The resulting reaction solution was diluted with tetrahydrofuran and precipitated in hexane. The supernatant was removed and vacuum dried to obtain a polymer dispersant A having a structure represented by the following formula (3). The yield of the obtained polymer dispersant A was 19.8 g. The number average molecular weight of the obtained polymer dispersant A measured by gel permeation chromatography was 7523, and the dispersion ratio was 1.66.

(Preparation of varnish solution)
7.19 g of the polymer dispersant A obtained above, 0.89 g of potassium hydroxide, and 39.82 g of pure water were added to the flask with branches and heated at 80 ° C. for 3 hours.

(Preparation of color material dispersion)
In a cup for a defoaming stirrer, 13.5 g of the varnish solution obtained above, 9.46 g of pure water, C.I. I. 4.04 g of Disperse Yellow 54 and 80.6 g of zirconia beads were added, and the mixture was stirred 10 times, and then the beads were separated using a filter to obtain a color material dispersion liquid.

(Presence or absence of gelation of color material dispersion)
When the presence or absence of gelation was visually confirmed in the color material dispersion liquid obtained above, no gelation was observed.

(Storage stability test of color material dispersion)
When the average particle size of the coloring material was determined for the color material dispersion liquid immediately after production obtained above, it was 279 nm. Then, the average particle size of the coloring material was determined for the color material dispersion liquid left in an environment of 60 ° C. for 5 days, and the rate of increase in the average particle size was determined to be less than 10%. The average particle size was measured using UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Further, when the color material dispersion liquid left in the environment of 60 ° C. for 5 days was visually confirmed, no sedimentation of the color material was observed.

4.2. Example 2
(Synthesis of Polymer Dispersant B)
A polymer dispersant B having a structure represented by the following formula (4) was obtained in the same manner as in Example 1 except that the same molar amount of acrylic phenoxyethyl was used instead of butyl acrylate in Example 1. .. The number average molecular weight of the obtained polymer dispersant B measured by gel permeation chromatography was 7671, and the dispersion ratio was 1.33.

(Preparation of varnish liquid and color material dispersion liquid)
A varnish solution and a color material dispersion were obtained in the same manner as in Example 1 except that the polymer dispersant B was used instead of the polymer dispersant A.

(Presence or absence of gelation of color material dispersion)
When the presence or absence of gelation was visually confirmed in the color material dispersion liquid obtained above, no gelation was observed.

(Storage stability test of color material dispersion)
When the rate of increase in average particle size of the colorant dispersion obtained above was determined in the same manner as in Example 1, it was less than 10%. Further, when the color material dispersion liquid left in the environment of 60 ° C. for 5 days was visually confirmed, no sedimentation of the color material was observed.

4.3. Comparative Example 1
(Synthesis of Polymer Dispersant C)
Phenoxyethyl acrylate 8.4 g (44 mmol), 1.22 g (17 mmol) acrylic acid, 3.19 g (17 mmol) ethoxyethoxyethyl acrylate, 2-(((carboxymethyl) sulfanylthiocarbonyl) sulfanyl) propanoic acid 0. 24 g (0.93 mmol), 0.13 g (0.79 mmol) of azobisisobutyronitrile, and 8 mL of ethanol were added to the flask with branches, freeze-degassed three times, and then stirred at 75 ° C. for 6 hours. The reaction solution was diluted with tetrahydrofuran and precipitated in hexane. The supernatant was removed and vacuum dried to obtain a polymer dispersant C having a structure represented by the following formula (5). The yield of the obtained polymer dispersant A was 12.4 g. The number average molecular weight of the obtained polymer dispersant C measured by gel permeation chromatography was 11867, and the dispersion ratio was 1.27.

(Preparation of varnish liquid and color material dispersion liquid)
A varnish solution and a color material dispersion were obtained in the same manner as in Example 1 except that the polymer dispersant C was used instead of the polymer dispersant A.

(Presence or absence of gelation of color material dispersion)
When the presence or absence of gelation was visually confirmed in the color material dispersion liquid obtained above, no gelation was observed.

(Storage stability test of color material dispersion)
When the average particle size of the coloring material was determined for the color material dispersion liquid immediately after production obtained above, it was 272 nm. Then, the average particle size of the coloring material was determined for the color material dispersion liquid left in an environment of 60 ° C. for 5 days, and the rate of increase in the average particle size was determined to be more than 30%. The average particle size was measured using UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Further, when the color material dispersion liquid left in the environment of 60 ° C. for 5 days was visually confirmed, sedimentation of the color material was observed.

4.4. Comparative Example 2
(Polymer dispersant D)
As the polymer dispersant D, poly-4-methylphenylethyl vinyl ether (A block), poly-2- (2-methoxyethyl) ethyl vinyl ether (B block), and poly-4- (2-vinyloxy) ethoxybenzoic acid ( A triblock copolymer composed of (C block) (polymerization ratio: A: B: C = 98: 90: 14) was used. The synthesis method was as follows.
Toluene was added to the container after adding 4-methylphenylethyl vinyl ether and ethyl acetate as monomers 2.5 times the amount of the monomer and 1-butoxyethyl acetate 10 times the amount of the monomer, and the temperature in the system reached 0 ° C. Then, a toluene solution of Et1.5AlCl1.5 (20 mM) was added to initiate polymerization. After 1.8 hours, 2- (2-methoxyethyl) ethyl vinyl ether was added, and the mixture was further stirred for 2 hours. Subsequently, 4- (2-vinyloxy) ethoxybenzoic acid was added, and the mixture was further stirred for 3 hours. A toluene solution having a concentration of 10% by weight of a partially saponified product of polyvinyl acetate (polymerization degree 500, degree of saponification 10 mol%) is used, and the number of moles of hydroxy groups of the partially saponified product of polyvinyl acetate is twice that of Et1.5AlCl1.5. The polymerization reaction was stopped by adding the amount (40 mM). The ratio of the number of moles of the monomer added at this time was 98:90:14. Methanol was added 5 minutes after the polymerization reaction was stopped, the solution was further diluted with dichloromethane, and then washed with water to remove the initiator residue. Then, the solution was concentrated and dried under reduced pressure to obtain a polymer dispersant D which is a random copolymer.
The number average molecular weight of the obtained polymer dispersant D measured by gel permeation chromatography was 27,200, and the dispersion ratio was 1.36.

(Preparation of varnish liquid and color material dispersion liquid)
A varnish solution and a color material dispersion were obtained in the same manner as in Example 1 except that the polymer dispersant D was used instead of the polymer dispersant A.

(Presence or absence of gelation of color material dispersion)
When the presence or absence of gelation was visually confirmed in the color material dispersion liquid obtained above, the dispersion of the color material was partially broken, and gelation was observed.

(Storage stability test of color material dispersion)
When the rate of increase in average particle size of the colorant dispersion obtained above was determined in the same manner as in Example 1, it was less than 10%. Further, when the color material dispersion liquid left in the environment of 60 ° C. for 5 days was visually confirmed, no sedimentation of the color material was observed.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes a configuration substantially the same as the configuration described in the embodiment, for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect. The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. The present invention also includes a configuration that exhibits the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. The present invention also includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (11)

A polymer dispersant having a hydrophobic block and a hydrophilic block.
The hydrophilic block contains a structural unit derived from a first hydrophilic monomer and a structural unit derived from a second hydrophilic monomer, and a structural unit derived from the first hydrophilic monomer and the second hydrophilic monomer. A polymer dispersant in which structural units derived from the hydrophilic monomers of the above are randomly arranged. The polymer dispersant according to claim 1, wherein the first hydrophilic monomer is an ionic monomer and the second hydrophilic monomer is a non-ionic monomer. The polymer dispersant according to claim 2, wherein the ionic monomer is an unsaturated carboxylic acid. The polymer dispersant according to claim 2 or 3, wherein the ionic monomer is (meth) acrylic acid. The polymer dispersant according to any one of claims 2 to 4, wherein the nonionic monomer is a monomer represented by the following general formula (1).

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a polyoxyethylene alkyl ether group or a hydroxyalkyl group in which two or more methyl groups and oxyethylene groups are linked.) The invention according to any one of claims 2 to 5, wherein the nonionic monomer is at least one selected from the group consisting of ethoxyethoxyethyl (meth) acrylate and methyl (meth) acrylate. Polymer dispersant. The polymer dispersant according to any one of claims 1 to 6, wherein the hydrophobic block has a structural unit derived from a hydrophobic monomer represented by the following general formula (2).

In formula (2), R ³ represents a hydrogen atom or a methyl group, and X is a branched alkyl ester group having 2 or more carbon atoms, a substituted or unsubstituted aryl group, a pyridyl group or an aryloxy. Represents an ethyl ester group.) At least the hydrophobic monomer is selected from the group consisting of styrene, butyl (meth) acrylate, -2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, and vinylpyridine. The polymer dispersant according to claim 7, which is one type. The polymer dispersant according to any one of claims 1 to 8, wherein the number average molecular weight (Mn) measured by gel permeation chromatography is 8,000 to 20,000. A color material dispersion liquid containing a color material, an aqueous medium, and the polymer dispersant according to any one of claims 1 to 9. An ink composition containing the color material dispersion liquid according to claim 10.