JP4384870B2 - Method for producing pigment aqueous dispersion - Google Patents

Description

【００６６】
表１に示された結果から、実施例１によれば、従来技術である比較例１及び比較例２と対比して、処理流量が多く、平均粒径がより小さく、光沢に優れた水系インクが得られることがわかる。
【００６７】
【発明の効果】
本発明によれば、処理流量が多い場合であっても、顔料含有ポリマー粒子の粒径が小さく、光沢が良好な水系インクを効率よく製造することができる。
【図面の簡単な説明】
【図１】図１は、本発明の製造法に用いられる流路を複数有する液−壁衝突型チャンバーの一実施態様を示す概略説明図である。
【図２】図２は、従来の液−液衝突型チャンバーの一実施態様を示す概略説明図である。
【図３】図３は、従来の単一の流路をもつ液−壁衝突型チャンバーの一実施態様を示す概略説明図である。
【符号の説明】
１ 流入管路
２ 剪断管路
３ 流出管路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water-based ink. More specifically, the present invention relates to a water-based ink that can be suitably used for a water-based ink for inkjet recording, a pigment water dispersion used therefor, and a method for producing the same.
[0002]
[Prior art]
The ink jet recording system has been widely used in recent years because it can be easily colored and can use plain paper as a recording member.
[0003]
Water-soluble dyes are used for inks used in ink jets in order to prevent ink from clogging the nozzles. However, this ink is inferior in water resistance and light resistance, especially when used as a heat jet ink, the dye is oxidized by the heat of the heater surface, the ink tends to scorch on the heater surface, and the discharge property is reduced. There is a drawback of doing.
[0004]
In order to eliminate this drawback, a pigment ink has been proposed. The pigment ink contains a pigment water dispersion. As a pigment water dispersion, a pigment dispersion type ink containing a pigment water dispersion in which a pigment is dispersed in water with a dispersant such as a surfactant or a water-soluble polymer, and a pigment in water-insoluble polymer polymer particles, A pigment-encapsulated ink containing an aqueous dispersion of pigment-containing polymer particles dispersed in water has been proposed.
[0005]
Since both the pigment-dispersed ink and the pigment-encapsulated ink require fine dispersion of the pigment, a high-pressure homogenizer having a bead mill, a sand mill, and a homogeneous valve (hereinafter referred to as a homogeneous valve type) Dispersing apparatuses such as a high-pressure homogenizer) and a high-pressure homogenizer having a dispersion chamber (hereinafter referred to as a chamber-type high-pressure homogenizer) are used.
[0006]
When a chamber type high pressure homogenizer is used, there is an advantage that impurities are not mixed due to wear of members, and durability is superior to that of a homogeneous valve type high pressure homogenizer.
[0007]
Liquid-liquid collision type chambers and liquid-wall collision type chambers are known as dispersion chambers used in chamber-type high-pressure homogenizers.
[0008]
An example of a liquid-liquid collision type chamber is shown in FIG. As shown in FIG. 2, the liquid-liquid collision type chamber has a plurality of liquid inflow lines 1, the same number of shear lines 2 as the inflow lines, and a single outflow line 3 sequentially connected. The ends of the plurality of shear pipes close to the outflow pipes are connected at one place, and are dispersed by collision of liquid flows at the connection places (for example, see Patent Document 1). A high-pressure homogenizer having a liquid-liquid collision type chamber is also used in the production of inkjet ink (see, for example, Patent Document 2).
[0009]
However, the liquid-liquid collision type chamber has drawbacks that the structure of the chamber is complicated and durability is low.
[0010]
Next, an example of a liquid-wall collision type chamber is shown in FIG. As shown in FIG. 3, each of the liquid-wall collision type chambers has a single liquid inflow line 1, a shear line 2 and an outflow line sequentially connected to each other. Is a right angle, and the liquid flow in the shear line 3 is made to collide with the inner wall of the outflow line. A high-pressure homogenizer having a liquid-wall collision type chamber is also used in the production of inkjet ink (see, for example, Patent Document 3). The liquid-wall collision type chamber has an advantage that since the chamber structure is simple, the processing liquid in the chamber is less clogged and the life of the chamber is extended.
[0011]
A chamber having a single flow path needs to increase the inner diameter of the shear line in order to increase the processing flow rate. However, in the case of processing at the same pressure, simply increasing the inner diameter of the shear pipe line has a drawback that the shear stress acting on the processing liquid is reduced, so that the dispersibility is lowered.
[0012]
[Patent Document 1]
US Pat. No. 4,533,254 [Patent Document 2]
Japanese Patent Publication No.8-30158 [Patent Document 3]
Japanese Patent Laid-Open No. 8-109344
[Problems to be solved by the invention]
The present invention includes a method for producing a pigment water dispersion capable of obtaining a sufficient dispersion force even when the treatment flow rate is large, a pigment water dispersion obtained by the production method, and the water dispersion. It is an object of the present invention to provide a water-based ink.
[0014]
[Means for Solving the Problems]
The present invention,
An inflow line, a plurality of shear lines, and an outflow line are sequentially connected, these lines are straight, the inner diameter of the shear line is 30 to 150 μm, and the total cross-sectional area of the shear line is The cross-sectional area of the inflow pipe line and the cross-sectional area of the outflow pipe line are smaller than each other, the angle between the shear pipe line and the outflow pipe line is 45 to 135 °, and the treatment liquid is subjected to a pressure of 50 MPa or more. A method for producing an aqueous pigment dispersion in which pigment-containing polymer particles having an average particle size of 50 to 200 nm are dispersed in water using a high-pressure homogenizer chamber having a structure in which the liquid passes through these pipes ,
Step (1): A step of passing a mixture containing a pigment, a water-insoluble vinyl polymer having a weight average molecular weight of 3,000 to 200,000, and a dispersion medium containing water and a ketone solvent as a treatment liquid into the high-pressure homogenizer chamber . Here, the content of the water-insoluble vinyl polymer is 10 to 400 parts by mass with respect to 100 parts by mass of the pigment, and
Step (2): A step of removing the ketone solvent from the dispersion obtained in Step (1) .
The present invention relates to a method for producing an aqueous pigment dispersion characterized by comprising:
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, an aqueous pigment dispersion in which the treatment liquid is passed through a liquid-wall collision type chamber having a plurality of flow paths, and the mixture is dispersed by shearing in the flow paths, collision with the wall surface, and rapid pressure drop. Get.
[0016]
In the present invention, unlike the single-channel liquid-wall collision type chamber, the number of shear pipes can be optimized according to the processing flow rate without changing the inner diameter of the flow path, so that the shear force is reduced. Even if the processing flow rate is increased, a sufficient dispersion force can be obtained.
[0017]
In the chamber used in the present invention, the number of inflow conduits and outflow conduits may be single or plural. The number of inflow conduits and outflow conduits is preferably 1 to 10 and more preferably 1 to 3 independently. The inflow conduit and the outflow conduit are preferably a single inflow conduit and a single outflow conduit, respectively, from the viewpoint of ease of manufacture.
[0018]
Next, one mode of a preferred chamber used in the production method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory view showing an embodiment of a liquid-wall collision type chamber having a plurality of flow paths used in the production method of the present invention.
[0019]
The flow channel 1, the shearing pipeline 2, and the outflow pipeline 3 are connected in order.
The inner diameter of the shear pipe 2 is preferably 30 to 200 μm, more preferably 50 to 150 μm, from the viewpoint of increasing the shearing force and improving the dispersibility. Examples of the shape of the shear pipe 2 include a circle, a rectangle, and an ellipse. In the case of a circle, the inner diameter is the inner diameter. When the shape is a rectangle or an ellipse, the inner diameter is a minimum inter-wall distance. .
[0020]
The total cross-sectional area of the shear pipe line 2 (the sum of the cross-sectional areas of the respective shear pipe lines, hereinafter the same) increases the flow rate of the processing liquid, obtains a stronger shear force, and enhances the dispersion effect due to collision with the wall surface. The cross-sectional area of the inflow conduit 1 (if there are multiple inflow conduits, the total cross-sectional area of each inflow conduit; the same applies hereinafter) and the cross-sectional area of the outflow conduit 3 (there are multiple outflow conduits) In this case, the total cross-sectional area of each outflow pipe is set to be smaller than each cross-sectional area. The total cross-sectional area of the shear pipe 2 is preferably 1/5 to 1/1000 of the cross-sectional area of the inflow pipe 1 and the cross-section of the outflow pipe 3, and more preferably 1/10 to 1/100. preferable.
[0021]
The number of the shear pipe lines 2 is plural, and is appropriately selected so as to be suitable for the processing flow rate. The number of the shear pipe lines 2 is preferably 2 to 20, and more preferably 3 to 10.
[0022]
The inner diameter and shape of the inflow conduit 1 are not particularly limited, and examples of the cross-sectional shape include a circle, an ellipse, a square, and a rectangle.
[0023]
The positional relationship between the inflow conduit 1 and the shear conduit 2 is not particularly limited. The positional relationship between the two may be, for example, a straight line, or an angle may be provided between the two.
[0024]
The inner diameter of the outflow conduit 3 may be the same as that of the outflow conduit 1. Further, the shape of the outflow pipe 3 is not particularly limited. Examples of the cross-sectional shape include a circle, an ellipse, a square, and a rectangle.
[0025]
The angle formed by the shear pipe line 2 and the outflow pipe line 3 is 45 to 135 °, preferably 90 °, from the viewpoint of causing the treatment liquid to collide with the inner wall of the outflow pipe line 3.
[0026]
The pressure when supplying the treatment liquid to the chamber is preferably 50 MPa or more, and more preferably 100 to 300 MPa, from the viewpoint of improving the dispersibility by increasing the shearing force, the collision force against the wall surface, and the rapid pressure drop. For example, a high-pressure pump can be used to supply the treatment liquid to the chamber.
[0027]
Examples of the high-pressure homogenizer having a chamber used in the present invention include a product name: Microfluidizer (Z-chamber multi-slot type) manufactured by Microfluidic Corporation.
[0028]
Examples of the treatment liquid include a mixture containing a pigment, a dispersant and / or a water-insoluble polymer, and a dispersion medium. When a mixture containing a pigment, a water-insoluble polymer and a dispersion medium is used as the treatment liquid, an aqueous pigment dispersion is obtained as an aqueous dispersion of pigment-containing polymer particles.
[0029]
The pigment may be either an inorganic pigment or an organic pigment. Moreover, this pigment and extender can also be used together as needed.
[0030]
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Among these, carbon black is particularly preferable for black ink. Examples of carbon black include furnace black, thermal black, acetylene black, and channel black.
[0031]
Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
[0032]
Examples of extender pigments include silica, calcium carbonate, and talc.
The dispersion medium requires water and may be water alone, or water and an organic solvent may be used in combination.
[0033]
Among organic solvents, alcohol solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, and halogenated aliphatic hydrocarbon solvents are preferable.
[0034]
Examples of the alcohol solvent include methanol, ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Examples of the aromatic hydrocarbon solvent include benzene and toluene. Examples of the aliphatic hydrocarbon solvent include heptane, hexane, cyclohexane and the like. Examples of the halogenated aliphatic hydrocarbon solvent include methylene chloride, 1,1,1-trichloroethane, chloroform, carbon tetrachloride, 1,2-dichloroethane and the like.
[0035]
Of these organic solvents, isopropanol, acetone and methyl ethyl ketone are preferred.
[0036]
Examples of water-insoluble polymers include water-insoluble vinyl polymers, polyester polymers, polyurethane polymers, and the like. Among these water-insoluble polymers, water-insoluble vinyl polymers are preferable. Examples of the water-insoluble vinyl polymer include a polymer of one or more monomers selected from the group consisting of styrene, (meth) acrylic acid, (meth) acrylic acid ester, and (meth) acrylic acid amide. As the water-insoluble polymer, a polymer having a solubility of less than 1 g in 100 g of water at 25 ° C. is preferable.
[0037]
The weight-average molecular weight of the water-insoluble polymer is 3000 to 200,000, preferably 10,000 to 100,000, from the viewpoints of ejection properties, prevention of scorching of the printer head, durability of the ink after printing, and stability of the solution or dispersion. Is desirable.
[0038]
The water-insoluble polymer preferably has a salt-forming group and is further neutralized with a neutralizing agent from the viewpoint of dispersion stability.
[0039]
The neutralizing agent is appropriately selected and used depending on the type of the salt-forming group. An acid or a base can be used as the neutralizing agent. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid, and polyethylene glycol acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like.
[0040]
The degree of neutralization of the water-insoluble polymer is not particularly limited, but usually it is preferably adjusted so that the liquid property of the aqueous dispersion of pigment-containing polymer particles is neutral, for example, pH 4.5 to 10.
[0041]
The amount of the water-insoluble polymer is 5 to 400 parts by mass, preferably 10 to 150 parts by mass with respect to 100 parts by mass of the pigment, from the viewpoint of printing density and ejection stability.
[0042]
Examples of the dispersant include a water-soluble polymer and a surfactant. The amount of the dispersant is preferably 5 to 400 parts by mass, more preferably 10 to 150 parts by mass with respect to 100 parts by mass of the pigment from the viewpoint of stably dispersing the pigment.
[0043]
Further, the amount of the dispersion medium is 100 to 2000 parts by mass, preferably 150 to 1000 parts by mass with respect to 100 parts by mass of the total amount of the pigment and the dispersant and / or the water-insoluble polymer from the viewpoint of the viscosity of the mixture. It is desirable to be.
[0044]
In the present invention, first, a pigment, a dispersant and / or a water-insoluble polymer, and a dispersion medium are mixed. The degree of mixing of these components is not particularly limited, and these components may be simply mixed or may be mixed so as to have a uniform composition.
[0045]
In mixing, a normal mixing and stirring device can be used. Among the mixing and stirring devices, a high-speed stirring and mixing device such as a disper is preferable.
[0046]
Next, the mixture of the pigment, the dispersant and / or the water-insoluble polymer, and the dispersion medium is subjected to a dispersion step. The dispersion using the high-pressure homogenizer chamber used in the production method of the present invention is preferably carried out for 1 to 30 passes, more preferably 5 to 20 passes. The temperature during dispersion is preferably 10 to 30 ° C.
[0047]
The average particle diameter of the pigment-containing polymer particles, from the viewpoint of dispersion stability and printing characteristics, preferably 50 to 1000 n m, and more preferably 50 to 200 n m. The average particle diameter is a value measured by a laser particle analysis system (ELS-8000, manufactured by Otsuka Electronics Co., Ltd.) (hereinafter the same).
[0048]
When the pigment water dispersion contains an organic solvent, the organic solvent can be removed by distillation under reduced pressure or the like.
[0049]
Next, an aqueous ink can be obtained by adding an appropriate amount of additives such as a wetting agent, a dispersing agent, an antifoaming agent, a chelating agent, and an antifungal agent to the pigment aqueous dispersion as necessary.
The aqueous ink thus obtained has excellent printing characteristics.
[0050]
【Example】
Production Example 1
In a reaction vessel, 20 parts by weight of methyl ethyl ketone and 0.03 part by weight of a polymerization chain transfer agent (2-mercaptoethanol), polypropylene glycol monomethacrylate [manufactured by Aldrich Japan Co., Ltd., number average molecular weight: 375] 2.5 parts by weight, methacrylic acid 1.2 weights Part and 6.3 parts by weight of styrene monomer were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
[0051]
Meanwhile, a dropping funnel was charged with 22.5 parts by weight of polypropylene glycol monomethacrylate [manufactured by Aldrich Japan, number average molecular weight: 375], 10.8 parts by weight of methacrylic acid and 56.7 parts by weight of styrene monomer, and a polymerization chain transfer agent (2-mercapto). Ethanol) 0.27 parts by weight, methyl ethyl ketone 60 parts by weight, and 2,2′-azobis (2,4-dimethylvaleronitrile) 1.2 parts by weight were mixed and sufficiently substituted with nitrogen gas to obtain a mixed solution.
[0052]
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 added dropwise over 3 hours. After 2 hours at 65 ° C from the end of the dropping, a solution in which 0.3 part by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) was dissolved in 5 parts by weight of methyl ethyl ketone was added, and then at 65 ° C for 2 hours, 70 ° C. For 2 hours to obtain a polymer solution.
[0053]
A portion of the resulting polymer solution was dried under reduced pressure at 105 ° C. for 2 hours and isolated by removing the solvent, and a gel using polystyrene as the standard substance and chloroform containing 1 mmol / L dodecyldimethylamine as the solvent. The weight average molecular weight measured by permeation chromatography was 55000.
[0054]
Example 1
5 parts by weight of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 5 parts by weight of methyl ethyl ketone, and 0.35 part by weight of a neutralizing agent (48% aqueous sodium hydroxide solution) was added thereto. The salt-forming group was neutralized, and 7.5 parts by weight of a phthalocyanine pigment (Dainippon Ink Chemical Co., Ltd., trade name: TGR-SD) and 30 parts by weight of ion-exchanged water were added to obtain a mixture.
[0055]
This mixture was dispersed under the following conditions using a chamber-type high-pressure homogenizer (trade name: Microfluidizer, manufactured by Microfluidics) to obtain a dispersion. The treatment flow rate discharged from the high pressure homogenizer was measured. The results are shown in Table 1.
[0056]
Processing pressure: 180MPa
Number of dispersion passes (number of treatments with high-pressure homogenizer): 5-pass chamber: G10Z-3 (Z-type chamber)
Shear pipe inner diameter: 87μm
Number of inflow lines: 1 Number of shear lines: 3
To the obtained dispersion, 35 parts by weight of ion-exchanged water was added and stirred, and then methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed to obtain a solid content concentration of 20% by weight. An aqueous dispersion of pigment-containing polymer particles was obtained.
[0058]
27.5 parts by weight of an aqueous dispersion of the obtained pigment-containing polymer particles, 15.5 parts by weight of glycerin, 5 parts by weight of propylene glycol monobutyl ether, 3.5 parts by weight of triethylene glycol monobutyl ether, Surfynol 104 [manufactured by Air Products Japan Co., Ltd., product Name] 0.3 parts by weight and 48.2 parts by weight of ion-exchanged water were mixed, and the resulting mixture was 25 μm in volume with a 0.5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) Was filtered with a needleless syringe (manufactured by Terumo Corp.) to remove coarse particles to obtain an aqueous ink.
[0059]
Comparative Example 1
In Example 1, instead of using three shear pipes having an inner diameter of 87 μm, a solid content concentration of 20% by weight was obtained in the same manner as in Example 1 except that one shear pipe having an inner diameter of 250 μm was used. An aqueous dispersion of pigment-containing polymer particles and an aqueous ink were obtained. Table 1 shows the processing flow when dispersing.
[0060]
Comparative Example 2
In Example 1, instead of using three shear pipes having an inner diameter of 87 μm, a solid content concentration of 20% by weight was obtained in the same manner as in Example 1 except that one shear pipe having an inner diameter of 87 μm was used. An aqueous dispersion of pigment-containing polymer particles and an aqueous ink were obtained. Table 1 shows the processing flow when dispersing.
[0061]
About the obtained water-based ink, the average particle diameter and the glossiness were evaluated by the following methods. The results are shown in Table 1.
[0062]
(1) Average particle size The average particle size was measured using a laser particle analysis system (ELS-8000, manufactured by Otsuka Electronics Co., Ltd.).
[0063]
(2) Using a glossy inkjet printer (Seiko Epson Corp., model number: EM900C), print on a solid MC glossy paper and leave it at 25 ° C for 1 hour. ), Product name: HANDY GLOSSMETER, product number: PG-1], and evaluated based on the following criteria.
[0064]
〔Evaluation criteria〕
○: 38 or more △: 35 or more and less than 38 ×: less than 35 [0065]
[Table 1]

[0066]
From the results shown in Table 1, according to Example 1, compared with Comparative Examples 1 and 2 which are the prior art, the water-based ink has a higher processing flow rate, a smaller average particle size, and excellent gloss. It can be seen that
[0067]
【The invention's effect】
According to the present invention, even when the treatment flow rate is large, it is possible to efficiently produce a water-based ink having a small particle diameter of the pigment-containing polymer particles and good gloss.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing an embodiment of a liquid-wall collision type chamber having a plurality of flow paths used in the production method of the present invention.
FIG. 2 is a schematic explanatory view showing an embodiment of a conventional liquid-liquid collision type chamber.
FIG. 3 is a schematic explanatory view showing one embodiment of a conventional liquid-wall collision type chamber having a single flow path.
[Explanation of symbols]
1 Inflow line 2 Shear line 3 Outflow line

Claims (4)

An inflow line, a plurality of shear lines, and an outflow line are sequentially connected, these lines are straight, the inner diameter of the shear line is 30 to 150 μm, and the total cross-sectional area of the shear line is The cross-sectional area of the inflow pipe line and the cross-sectional area of the outflow pipe line are smaller than each other, the angle between the shear pipe line and the outflow pipe line is 45 to 135 °, and the treatment liquid is subjected to a pressure of 50 MPa or more. A method for producing an aqueous pigment dispersion in which pigment-containing polymer particles having an average particle size of 50 to 200 nm are dispersed in water using a high-pressure homogenizer chamber having a structure in which the liquid passes through these pipes ,
Step (1): A step of passing a mixture containing a pigment, a water-insoluble vinyl polymer having a weight average molecular weight of 3,000 to 200,000, and a dispersion medium containing water and a ketone solvent as a treatment liquid into the high-pressure homogenizer chamber . Here, the content of the water-insoluble vinyl polymer is 10 to 400 parts by mass with respect to 100 parts by mass of the pigment, and
Step (2): A step of removing the ketone solvent from the dispersion obtained in Step (1) .
A method for producing a pigment aqueous dispersion, comprising: 2. The production method according to claim 1 , wherein the amount of the dispersion medium is 150 to 1,000 parts by mass with respect to 100 parts by mass of the total amount of the pigment and the water-insoluble vinyl polymer . The production method according to claim 1 or 2, wherein the water-insoluble vinyl polymer is a polymer of at least one monomer selected from the group consisting of styrene, (meth) acrylic acid, and (meth) acrylic acid ester . The production method according to claim 1, wherein the ketone solvent is methyl ethyl ketone .

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