JP3880550B2 - Water-based ink - Google Patents

Description

【００５７】
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と対比して、分散粒子の平均粒径がより小さい顔料の水分散体、及びそれが用いられた濾過性及び光沢に優れた水系インクが得られることがわかる。
【００５８】
【発明の効果】
本発明の製造法によれば、従来の製造法と対比して、分散粒子の平均粒径がより小さい顔料の水分散体を製造することができる。また、得られた顔料の水分散体を用いれば、濾過性及び光沢に優れた水系インクを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water-based ink. More specifically, the present invention relates to a method for producing a water-based ink and an aqueous dispersion of a pigment used therefor. The water-based ink can be suitably used as, for example, a water-based ink for inkjet recording.
[0002]
[Prior art]
In recent years, pigment inks have been used for inks used in inkjet printers in order to improve water resistance and light resistance.
[0003]
The pigment ink is generally produced by dispersing a pigment at a low solid content concentration of about 10 to 40% by weight in an organic solvent or a mixed solution of water and an organic solvent. When dispersing, a sand mill, a bead mill, a high-pressure homogenizer, or the like is used as a dispersing device (see, for example, Patent Documents 1 and 2).
[0004]
Pigment inks are less glossy than dye inks, so the dispersed particle size is made as small as possible, and filter filterability is inferior to dye inks, so the development of pigment inks with better filterability is desired. Yes.
[0005]
However, in the method of dispersing at a low solid content concentration described in the above-mentioned document, if a pigment with strong cohesion of primary particles is used or if dispersion at the primary particle level is required, sufficient atomization is performed. May not be possible or the filterability may be poor.
[0006]
On the other hand, as a method using a solid coloring compound, a solid coloring compound obtained by kneading a mixture of a resin melt having an acid value or an organic solvent solution and a pigment, and water, an organic solvent and a base are mixed ( (Distribution) is described (for example, see Patent Documents 3 and 4). However, in this method, since the solid content concentration of the solid coloring compound is very high and the resin is not neutralized, dispersion in water and an organic solvent may be insufficient.
[0007]
[Patent Document 1]
JP-A-8-183920 [Patent Document 2]
JP-A-8-218013 [Patent Document 3]
Japanese Patent Laid-Open No. 10-88042 [Patent Document 4]
JP 2001-271008 A [0008]
[Problems to be solved by the invention]
The present invention provides a method capable of producing an aqueous dispersion of a pigment having a smaller average particle size of dispersed particles as compared with a conventional method of dispersing at a low solid content concentration and a method of using a solid coloring compound, It is another object of the present invention to provide a water-based ink excellent in filterability and gloss.
[0009]
[Means for Solving the Problems]
The present invention
(1) (A) a pigment, a polymer having a salt-forming group (hereinafter simply referred to as “polymer”), a neutralizing agent for neutralizing the polymer having the salt-forming group, an organic solvent and water, A mixture having a solid content of 50 to 80% by weight (hereinafter simply referred to as a mixture) is kneaded. Here, the kneading is performed by kneading the mixture with a kneader and further kneading with a roll mill.
(B) After adding water and / or an organic solvent and diluting to the obtained kneaded material,
(C) a method for producing an aqueous dispersion of a pigment in which the solid content is dispersed in the obtained dilution, and (2) an aqueous ink containing the aqueous dispersion of the pigment obtained by the production method. .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with extender pigments.
[0011]
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Among these, carbon black is preferable particularly for black aqueous ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
[0012]
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
Examples of extender pigments include silica, calcium carbonate, and talc.
[0013]
The amount of the pigment is preferably 100 to 700 parts by weight, more preferably 200 to 600 parts by weight, and still more preferably 300 to 500 parts by weight with respect to 100 parts by weight of the resin solid content of the polymer from the viewpoint of printing density. .
[0014]
The present invention is particularly suitable for dispersing a pigment having a strong primary particle cohesion, and examples of the shape of the pigment having a strong primary particle cohesion include needles and plates.
[0015]
As the polymer, a water-insoluble polymer that can contain a pigment or a water-soluble polymer that can disperse the pigment can be used. Of these, water-insoluble polymers are preferred. The water-insoluble polymer is preferably a polymer having a solubility of less than 2 g when dissolved in 100 g of water at 25 ° C. after neutralization. When a water-insoluble polymer is used, an aqueous dispersion of pigment-containing polymer particles is obtained. When a water-soluble polymer is used, a pigment dispersion is obtained. Therefore, in the present invention, an aqueous dispersion of pigment-containing polymer particles or a pigment dispersion is exemplified as the aqueous dispersion of pigment.
[0016]
Examples of the polymer include vinyl polymers, polyester polymers, polyurethane polymers and the like. Of these polymers, vinyl polymers are preferred. Examples of the vinyl polymer include a polymer of one or more monomers selected from the group consisting of styrene, (meth) acrylic acid, and (meth) acrylic acid ester. The weight average molecular weight of the polymer is preferably 10,000 to 300,000 from the viewpoint of enhancing the durability of the ink after printing.
[0017]
The polymer has a salt-forming group, and a neutralizing agent is used to neutralize the salt-forming group.
[0018]
As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, and glyceric acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like. The amount of the neutralizing agent is not particularly limited, and it is usually preferable to adjust the aqueous dispersion of the obtained pigment to be neutral, for example, pH is 4.5 to 9.5. In addition, before mixing a pigment etc. and a neutralizing agent, you may neutralize a salt production group with the neutralizing agent beforehand.
[0019]
As the organic solvent, alcohol solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, and halogenated aliphatic hydrocarbon solvents are preferable, and hydrophilic organic solvents are more preferable.
[0020]
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. Of these, acetone and methyl ethyl ketone are preferred.
[0021]
The amount of water is preferably from 100 to 1000 parts by weight, more preferably from 200 to 500 parts by weight, based on 100 parts by weight of the organic solvent, from the viewpoint of the compatibility of the pigment.
[0022]
The solid content concentration in the mixture is 50% by weight or more, preferably 65% by weight or more from the viewpoint of obtaining an effective shearing force when the mixture is kneaded, and the resulting kneaded product has a too high viscosity and is uniform. From the viewpoints of preventing the kneading from becoming impossible and preventing the kneaded material from collapsing into particles, it is 80% by weight or less, preferably 75% by weight or less. From these viewpoints, the solid content concentration in the mixture is 50 to 80% by weight, more preferably 65 to 75% by weight. Here, the solid content in the mixture is a combination of the solid content of the pigment, polymer, and neutralizer.
[0023]
In the present invention, since a neutralizing agent, an organic solvent and water are present in the mixture in addition to the pigment and the polymer during kneading, the polymer adsorbing power to the pigment becomes strong and atomization can be sufficiently performed.
[0024]
When kneading the mixture, for example, a kneader, a planetary mixer, an extruder, a roll mill or the like can be used as a kneading apparatus. Among these, a kneader is preferable from the viewpoint of strong shear stress and easy control of operating conditions.
[0025]
The kneaded material obtained by a kneader or a planetary mixer may contain coarse particles. Therefore, in this case, it is preferable to further knead the kneaded product with a roll mill. As the roll mill, a two-roll mill or a three-roll mill can be used. During the kneading, it is preferable to add water.
[0026]
When the raw materials constituting the mixture are put into the kneading apparatus, (1) each may be put into the kneading apparatus separately, and (2) neutralization for neutralizing the pigment, polymer and the polymer in advance. After mixing the agent, organic solvent and water in separate containers, they may be put into a kneading apparatus all at once, or (3) polymer, organic solvent, water and neutralizing agent are mixed in separate containers in advance. The obtained mixture and pigment may be put into a kneading apparatus. Among these methods, (I-1) a polymer, an organic solvent, water and a neutralizing agent are mixed in a kneading apparatus or (I-2) ) A method in which these raw materials are mixed in a separate container, and then the obtained mixture is put into a kneader and (II) and then a pigment is put into a preferred method.
[0027]
The temperature at the time of kneading is preferably 50 ° C. or lower, more preferably 5 to 50 ° C., and further preferably 10 to 35 ° C. from the viewpoint of obtaining a shear stress suitable for kneading. The temperature at the time of kneading | mixing can be adjusted with the temperature or flow volume of the cooling medium sent through the jacket of a kneading apparatus.
[0028]
The kneading is preferably performed until the raw materials constituting the mixture are uniformly dispersed. Thus, after kneading | mixing, water and / or an organic solvent are added and diluted to the obtained kneaded material. When used in water-based inks, it is preferable to dilute with water in order to remove the organic solvent in the post-dilution step.
[0029]
The solid content concentration after dilution may be a concentration that can be processed in the next dispersion step, and is usually 10 to 40% by weight.
[0030]
There is no particular limitation on the method for diluting the kneaded product by adding water and / or an organic solvent, and a known diluting device can be used. Examples of such an apparatus include a disper and a butterfly mixer.
[0031]
Next, the solid content contained in the obtained dilution is dispersed in water and / or an organic solvent. A dispersion apparatus can be used for dispersion of the diluted product.
[0032]
Examples of the dispersing device include a ball mill, a bead mill, a high-pressure homogenizer, and a high-speed stirring type disperser. Among these, a high-pressure homogenizer is preferable because it contains less inorganic impurities.
[0033]
Examples of the high-pressure homogenizer include those having a chamber in which the flow path of the processing liquid is fixed and those having a homogeneous valve capable of adjusting the width of the flow path of the processing liquid. As a high-pressure homogenizer having a chamber in which the flow path of the processing solution is fixed, a microfluidizer (trade name, manufactured by Microfluidics), a nanomizer (trade name, manufactured by Nanomizer), an optimizer (manufactured by Sugino Machine, product) Name). Examples of high-pressure homogenizers having a homogeneous valve include high-pressure homogenizers (trade name, manufactured by Lani), high-pressure homogenizers (trade name, manufactured by Mimaru Machinery Co., Ltd.), and high-pressure homogenizers (trade name, manufactured by Izumi Food Machinery Co., Ltd.). Can be mentioned.
[0034]
The pressure when dispersing with a high-pressure homogenizer is preferably 50 MPa or more, more preferably 80 MPa or more, because polymer particles having a desired particle diameter can be easily obtained in a short time.
[0035]
Thus, an aqueous dispersion of the pigment of the present invention is obtained.
When producing a water-based ink using the aqueous dispersion of the pigment of the present invention, it is preferable to remove the organic solvent from the aqueous dispersion.
[0036]
A method for removing the organic solvent from the pigment aqueous dispersion is not particularly limited, but a vacuum distillation method is preferable, and a thin film type is more preferable.
[0037]
If necessary, coarse particles may be removed from the pigment aqueous dispersion by centrifugation, filter filtration, or the like.
[0038]
The aqueous ink of the present invention can be obtained by adding additives such as a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, and a chelating agent to the aqueous dispersion as necessary. From the viewpoint of printing density and ejection stability, the solid content in the water dispersion in the water-based ink is the polymer particles in the water dispersion of the pigment-containing polymer particles contained in the water-based ink or the pigment dispersion. It is desirable to adjust the pigment particle content to 1 to 30% by weight, preferably 2 to 15% by weight.
[0039]
【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 [number average molecular weight: 375, manufactured by Aldrich Japan Co., Ltd.] 2.5 parts by weight, 1.2 parts by weight of methacrylic acid Parts and 6.3 parts by weight of styrene monomer were mixed and mixed with nitrogen gas sufficiently to obtain a mixed solution.
[0040]
On the other hand, 22.5 parts by weight of polypropylene glycol monomethacrylate (number average molecular weight: 375, manufactured by Aldrich Japan Co., Ltd.), 10.8 parts by weight of methacrylic acid and 56.7 parts by weight of styrene monomer were charged into a dropping funnel, 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 added and mixed, and the mixture was sufficiently replaced with nitrogen gas to obtain a mixed solution.
[0041]
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 dropwise addition, a solution of 0.3 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) in 5 parts by weight of methyl ethyl ketone was added, and further at 65 ° C for 2 hours, 70 ° C. For 2 hours to obtain a polymer solution.
[0042]
A portion of the resulting polymer solution was dried at 105 ° C. for 2 hours under reduced pressure 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.
[0043]
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 solution, and 7 parts by weight of ion-exchanged water and 0.47% aqueous 48% sodium hydroxide solution were added to the resulting solution. Part by weight was added and mixed with a disper wing for 30 minutes, and then charged into a kneader. Further, 20 parts by weight of quinacridone pigment [CI Pigment Red 122, manufactured by Dainippon Ink & Chemicals, Inc., trade name: Fastgen Super Magenta R] was added thereto. The solid concentration at this time was 67% by weight. In a sealed state, 1 ° C. cooling water was poured into the jacket and kneaded at 20 ° C. for 2 hours to obtain a kneaded product.
[0044]
The resulting kneaded product is kneaded with a three-roll mill while adding 10 parts by weight of ion-exchanged water, diluted by adding 50 parts by weight of ion-exchanged water, and then microfluidizer (trade name, manufactured by Microfluidics). And 5 pass dispersion treatment at a pressure of 200 MPa.
[0045]
After adding 30 parts by weight of ion-exchanged water to the resulting dispersion and stirring, the organic solvent and a part of the water were removed at 60 ° C. under reduced pressure. ] To remove coarse particles, and an aqueous dispersion of pigment-containing polymer particles having a solid content concentration of 20% by weight was obtained.
[0046]
Next, 27.5 parts by weight of an aqueous dispersion of the obtained pigment-containing polymer particles, 15.5 parts by weight of glycerol, 5 parts by weight of propylene glycol monobutyl ether, 3.5 parts by weight of triethylene glycol monobutyl ether, Surfynol 104 (Air Products Japan Co., Ltd.) (Product) 0.3 parts by weight and 48.2 parts by weight of ion-exchanged water were mixed to obtain a water-based ink.
[0047]
Comparative 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 67 parts by weight of ion-exchanged water and 0.47% aqueous 48% sodium hydroxide solution were added to the resulting solution. After adding parts by weight and mixing with a disper blade for 30 minutes, further add 20 parts by weight of quinacridone pigment [CI Pigment Red 122, manufactured by Dainippon Ink & Chemicals, Inc., trade name: Fastgen Super Magenta R]. In addition, the mixture was mixed with a disper blade at 20 ° C. for 2 hours. The solid concentration at this time was 26% by weight.
[0048]
The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 180 MPa. The obtained dispersion-treated product was treated in the same manner as in Example 1 to obtain an aqueous ink.
[0049]
Comparative Example 2
5 parts by weight of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 4 parts by weight of methyl ethyl ketone, and 1 part by weight of ion-exchanged water and 0.47% by weight of 48% sodium hydroxide aqueous solution were added to the resulting solution. The mixture was added to the kneader after mixing for 30 minutes with a disper blade. Further, 20 parts by weight of quinacridone pigment [CI Pigment Red 122, manufactured by Dainippon Ink & Chemicals, Inc., trade name: Fastgen Super Magenta R] was added. The solid concentration at this time was 83% by weight. Next, the mixture was kneaded for 30 minutes at 60 ° C. in a sealed state, but the kneaded product aggregated in the kneader and did not reach a good kneaded state.
[0050]
About the obtained water-based ink, the average particle diameter, filterability, and glossiness were evaluated by the following method. The results are shown in Table 1.
[0051]
(1) Average particle diameter The average particle diameter was measured using a laser particle analysis system ELS-8000 manufactured by Otsuka Electronics Co., Ltd.
[0052]
(2) Filterability
Filtering with a syringe of 25 mL capacity (with Terumo Corporation) attached with a 0.8 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.), one filter is clogged. The amount of liquid passed was measured and evaluated according to the following evaluation criteria.
[0053]
〔Evaluation criteria〕
○: Flow rate is 100mL or more △: Flow rate is 20mL or more and less than 100mL ×: Flow rate is less than 20mL [0054]
(3) Glossy Seiko Epson Co., Ltd. Inkjet Printer (Model: EM900C) was used to print solid on commercially available MC glossy paper and left for 1 hour at 25 ° C. Manufactured, product name: HANDY GLOSSMETER, product number: PG-1], and evaluated based on the following criteria.
[0055]
〔Evaluation criteria〕
○: 35 or more △: 30 or more and less than 35 ×: less than 30 [0056]
[Table 1]

[0057]
From the results shown in Table 1, according to Example 1, as compared with Comparative Example 1 which is the prior art, an aqueous dispersion of a pigment having a smaller average particle diameter of dispersed particles, and filtration using the same It can be seen that a water-based ink having excellent properties and gloss can be obtained.
[0058]
【The invention's effect】
According to the production method of the present invention, it is possible to produce an aqueous dispersion of a pigment having a smaller average particle diameter of dispersed particles as compared with the conventional production method. Moreover, if the obtained pigment aqueous dispersion is used, an aqueous ink excellent in filterability and gloss can be obtained.

Claims (4)

(A) It contains a pigment, a polymer having a salt-forming group, a neutralizing agent for neutralizing the polymer having the salt-forming group, an organic solvent and water, and the solid content is 50 to 80% by weight. Kneading the mixture , wherein the kneading is kneading the mixture with a kneader, and further kneading with a roll mill,
(B) After adding water and / or an organic solvent and diluting to the obtained kneaded material,
(C) A method for producing an aqueous dispersion of a pigment in which the solid content is dispersed in the obtained dilution.   The method for producing an aqueous dispersion of a pigment according to claim 1, wherein in the step (A), the temperature during kneading is 50 ° C or lower. The method for producing an aqueous dispersion of a pigment according to claim 1 or 2 , wherein in the step (C), the solid content in the dilution is dispersed with a high-pressure homogenizer. An aqueous ink comprising an aqueous dispersion of a pigment obtained by the production method according to any one of claims 1 to 3 .