JP2021080380A - Pigment including resin particle and method for producing the same, and ink using the pigment including resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and industrialized synthetic method for producing pigment-encapsulating resin particles having a nano-order particle size. A method for producing pigment-encapsulating resin particles, wherein the pigment-encapsulating resin particles are batch-type in an emulsion containing a pigment, an aqueous medium, a monomer, a low CMC surfactant, and a polymerization initiator. A production method in which the average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less. [Selection diagram] Fig. 2

Description

The present invention relates to pigment-encapsulating resin particles, a method for producing the same, and an ink using the pigment-encapsulating resin particles.

Conventionally, from the viewpoint of improving the fixability of the colorant in the ink to the recording medium and improving the abrasion resistance of the printed image, the pigment contained in the ink for inkjet printing is coated with a resin having a particle size of nano-order level. Pigment particles are used, which are called pigment-encapsulating resin particles, pigment-encapsulating particles, pigment-containing resin particles, microencapsulating pigments, microcapsule pigments, and the like. By using the pigment-encapsulating resin particles having such a small particle size, the ejection of ink from the nozzle of the recording head can be stabilized and the dispersion stability can be improved.

The pigment-encapsulating resin particles used in the ink for inkjet printing are preferably those having a nano-order particle size of, for example, 500 nm or less, and the pigment-encapsulating resin particles having such a small particle size have a sufficient surface coating of the pigment and are simple. Various methods have been proposed for production with dispersion (ie, narrow particle size distribution). For example, Patent Document 1 discloses a dye-encapsulating microcapsule having an average particle size of 0.6 to 0.7 μm formed by self-accumulation of a polymer and a method for producing the same, and Patent Document 2 describes a hydrophilic group. A method for producing a microencapsulated pigment having a small particle size and a narrow particle size distribution is disclosed by coating the pigment particles on the surface with a polymer by a mini-emulsion polymerization method.

JP-A-2002-167522 Japanese Unexamined Patent Publication No. 2005-97518

However, for example, in the method disclosed in Patent Document 1, since a rod-coil block polymer which is a self-integrating polymer is used, a complicated processing step for synthesizing this rod-coil block polymer is used. Is required. Further, in the method disclosed in Patent Document 2, a complicated treatment is required in order to bond a hydrophilic group to the surface of the pigment, and further, in order to obtain nano-order microcapsules, while irradiating ultrasonic waves. It is necessary to carry out a mini-emulsion reaction. In order to produce pigment-encapsulating resin particles having nano-order particle size by other conventional methods, mechanical treatment (sonication treatment, homogenizer treatment, etc.) using a strong shearing force at the time of polymerization can be performed, or hydrohove (hydrophobe treatment, etc.) can be performed. Reagents such as (hydrophobic substances) were added, unreacted monomers were removed after polymerization, and process control was required (Japanese Patent Laid-Open No. 3940909, JP-A-2014-40579, JP-A-2003-306611). Gazette, etc.).

As described above, depending on the conventional method for synthesizing the pigment-encapsulating resin particles, it is difficult to improve the productivity and the hurdle for industrialization is high because many kinds of reagents are used and complicated treatment is required. Therefore, it has been desired to develop a simple and industrialized synthetic method for producing pigment-encapsulated resin particles having a nano-order particle size. Therefore, an object of the present invention is to provide pigment-encapsulating resin particles, a method for producing the same, and an ink using the pigment-encapsulating resin particles, which can solve the above problems.

The inventor of the present application has conducted diligent research on a method for producing pigment-encapsulated resin particles having a particle size of nano-order. Then, they found that by adopting a configuration in which emulsion polymerization was performed using a low CMC surfactant or the like, pigment-encapsulating resin particles having a nano-order particle size could be produced more easily than the conventional method, and the present invention was completed. did.

That is, according to the present invention, in the method for producing pigment-encapsulating resin particles, the pigment-encapsulating resin particles are an emulsion containing a pigment, an aqueous medium, a monomer, a low CMC surfactant, and a polymerization initiator. A method for producing the pigment-encapsulating resin particles, which is synthesized in a batch manner and has an average particle size of 30 nm or more and 200 nm or less. The low CMC surfactant is preferably an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms. It is preferable that the polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.

Further, according to the present invention, it is a method for producing pigment-encapsulating resin particles.
(A) A step of dispersing a pigment in an aqueous medium to prepare a pigment dispersion liquid, and
(B) A step of preparing a mixture of the pigment dispersion liquid and a surfactant, and
(C) A step of adding a monomer to the mixture to form an emulsion, and
(D) Including a step of adding a polymerization initiator to the emulsion and emulsion-polymerizing the monomer to synthesize pigment-encapsulating resin particles.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The surfactant is a low CMC surfactant,
The steps (B), (C) and (D) are carried out in the same reaction vessel.
A manufacturing method is provided. It is preferable that the steps (B), (C) and (D) are carried out under stirring of 300 rpm or more and 500 rpm or less. The low CMC surfactant is preferably an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms. It is preferable that the polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.

Further, according to the present invention, it is a method for producing pigment-encapsulating resin particles.
The pigment-encapsulating resin particles are synthesized in a batch manner in an emulsion containing a pigment, an aqueous medium, a monomer, a surfactant, and a polymerization initiator.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.
A manufacturing method is provided.

In addition, according to the present invention, pigment-encapsulating resin particles produced by any of the above-mentioned production methods and ink containing the pigment-encapsulating resin particles are provided.

According to the present invention, a pigment-encapsulating fine particles having a nano-order particle size and an ink containing the pigment-encapsulating fine particles can be produced more easily than the conventional method, and application to industrialization becomes easy. Further, by blending such pigment-encapsulating resin particles into the ink, an ink having good fixability on a recording medium and excellent scratch resistance of a printed image can be obtained.

It is a figure which shows an example of the structure of the reaction vessel which concerns on one Embodiment of this invention. FIG. 1 (A) is a vertical sectional view, and FIG. 1 (B) is a horizontal sectional view. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 1. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 2. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 3. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 4. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 5. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 6. 6 is an FE-SEM image of the pigment-encapsulating resin particles synthesized in Example 7. It is a table which shows the outline and the result of the Example of this invention.

The present invention will be described below with reference to preferred embodiments. The production method according to one embodiment of the present invention is a method for producing pigment-encapsulating resin particles, wherein the pigment-encapsulating resin particles are a pigment, an aqueous medium, a monomer, a low CMC surfactant, and a polymerization initiator. This is a production method in which the pigment-encapsulating resin particles are synthesized in a batch manner and have an average particle size of 30 nm or more and 200 nm or less. Thereby, the pigment-encapsulating resin particles having a nano-order particle size can be obtained by a simple production method.

In this embodiment, the low CMC surfactant is preferably an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms. It is preferable that the polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.

The production method according to another embodiment of the present invention is a method for producing pigment-encapsulating resin particles.
(A) A step of dispersing a pigment in an aqueous medium to prepare a pigment dispersion liquid, and
(B) A step of preparing a mixture of the pigment dispersion liquid and a surfactant, and
(C) A step of adding a monomer to the mixture to form an emulsion, and
(D) Including a step of adding a polymerization initiator to the emulsion and emulsion-polymerizing the monomer to synthesize pigment-encapsulating resin particles.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The surfactant is a low CMC surfactant,
The steps (B), (C) and (D) are carried out in the same reaction vessel.
It is a manufacturing method. According to such a configuration, pigment-encapsulated resin particles having an average particle size of 30 nm or more and 200 nm or less can be obtained by a simple production method.

In this embodiment, the low CMC surfactant is preferably an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms. It is preferable that the polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.

The production method according to still another embodiment of the present invention is a method for producing pigment-encapsulating resin particles.
The pigment-encapsulating resin particles are synthesized in a batch manner in an emulsion containing a pigment, an aqueous medium, a monomer, a surfactant, and a polymerization initiator.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.
It is a manufacturing method. According to such a configuration, pigment-encapsulated resin particles having a nano-order particle size can be obtained by a simple manufacturing method, and application to industrialization becomes easy.

According to yet another embodiment of the present invention, pigment-encapsulating resin particles produced by any of the above-mentioned production methods of the present invention are provided. Inks containing the pigment-encapsulating resin particles are also provided. As a result, it is possible to obtain pigment-encapsulating resin particles having an average particle size of 30 nm or more and 200 nm or less, and an ink using such pigment-encapsulating resin particles, which has good fixability to a recording medium and excellent wear resistance.

<Pigment-encapsulating resin particles>
(Average particle size)
The average particle size of the pigment-encapsulating resin particles produced by the method of the present invention is preferably in the range of 30 nm or more and 200 nm or less, more preferably in the range of 60 nm or more and 200 nm or less, and in the range of 85 nm or more and 150 nm or less. It is even more preferable to have.

The particle size of the pigment-encapsulated resin particles can be measured by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. Alternatively, the particle size can be measured by taking a particle image with a field emission scanning electron microscope or a transmission electron microscope. In the present invention, it is preferable to measure the average particle size of the pigment-encapsulated resin particles by a dynamic light scattering method (DLS) or by taking a particle image of a field emission scanning electron microscope.

(Pigment)
The pigment used in the present invention is not particularly limited as long as it does not dissolve in the aqueous medium in which the pigment is dispersed, and known inorganic pigments and organic pigments can be used depending on the intended purpose. As the inorganic pigment, for example, titanium oxide, antimony red, red iron oxide, cadmium red, cadmium yellow, cobalt blue, navy blue, ultramarine, carbon black, graphite and the like can be used, and as the organic pigment, for example, quinacridone pigment and quinacridone quinone pigment can be used. Pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanslon pigments, flavanthron pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, Anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, azo pigments and the like can be used. Examples of pigments that can be used in the present invention are also described in The Color Index, Third Edition (The Society of Dyers and Colorists, 1982). Two or more of these pigments may be used in combination. As will be described later, a commercially available pigment dispersion may be used.

The amount of the pigment added is preferably 1.0% by mass or more and 14.0% by mass or less, and more preferably 6.0% by mass or more and 12.0% by mass or less based on the total amount of the water-based ink.

(Aqueous medium)
As the aqueous medium used in the present invention, water (for example, ion-exchanged water, distilled water, ultrapure water, etc.), a water-soluble organic solvent, or a mixture thereof can be used. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, n- and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol; alkyl ethers of polyalkylene glycol. Kind: Lactams such as N-methyl-2-pyrrolidone and the like. From the viewpoint of safety and environmental impact, it is preferable to use water or a mixture of water and a water-soluble organic solvent.

(Surfactant)
The surfactant used in the present invention is not particularly limited, but for example, anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, and polyoxyethylene. Nonionic surfactants such as alkylallyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts are particularly anionic surfactants. Surfactants can be preferably used. Of these, low CMC surfactants are preferred. In the present invention, the "low CMC surfactant" means a surfactant having a low critical micelle concentration (CMC) (for example, CMC of 0.1 to 0.001 mol / l). As the anionic surfactant having a low critical micelle concentration (CMC), an anionic surfactant containing a linear hydrocarbon is preferable. For example, those having a linear alkyl or alkenyl group having 11 to 25 carbon atoms, preferably 15 to 23 carbon atoms can be used. It is preferable to use an anionic surfactant having a linear alkyl group, and it is more preferable to use an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms, and it is more preferable to use a linear surfactant having 18 carbon atoms. It is even more preferable to use an anionic surfactant having an alkyl group.

The amount of the low CMC surfactant added is preferably 0.01% by mass or more and 0.50% by mass or less, and 0.03% by mass or more and 0.25% by mass or less, based on the total amount of the monomers. Is even more preferable.

(monomer)
The monomer used in the present invention is not particularly limited as long as it has polymerizable properties. For example, styrene-based monomers such as styrene, α-methylstyrene, and chlorostyrene; acrylic acid, methacrylate; methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, butyl methacrylate, etc., preferably having 1 or more and 22 or less carbon atoms. Styrene ester having an alkyl group of 1 or more and 12 or less, more preferably 1 or more and 8 or less; vinyl halide such as vinyl chloride and vinyl bromide and vinylidene halide such as vinylidene chloride; vinyl acetate, vinyl propionate and the like. Vinyl esters and the like can be used, and styrene-based monomers and methacrylic acid esters are preferably used. Two or more kinds of monomers may be used in combination. In particular, styrene, methyl methacrylate (methyl methacrylate), glycidyl methacrylate (glycidyl methacrylate) and the like are preferably used. Only one kind of these monomers may be used, or two or more kinds may be used.

The amount of the monomer used is preferably 2.0% by mass or more and 5.0% by mass or less, more preferably 3.0% by mass or more and 4.0% by mass or less, still more preferably, based on the total amount of the water-based ink. It is 3.0% by mass or more and 3.5% by mass or less.

(Polymerization initiator)
The polymerization initiator used in the present invention is not particularly limited, but is, for example, hydroperoxides such as hydrogen peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramentan hydroperoxide, benzoyl peroxide, and lauroylper. Peroxides such as oxides and 2,2'-azobis {2-methyl-N- [2- (1-hydroxybutyl) propionamide]}, 2,2'-azobis [(2-methylpropionamidine) dihydro Chloride], 2,2'-azobis [N- (2-carboxyethyl) -2-methyl-propiondiamine] tetrahydrate, 2,2'-azobis (2,4-dimethylvaleronitrile), azobisisobuty Examples thereof include organic polymerization initiators such as azo compounds such as ronitrile and inorganic polymerization initiators such as persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate. Further, a so-called redox-based polymerization initiator in which a reducing agent such as sodium bisulfite, ascorbic acid and a salt thereof is used in combination with the polymerization initiator can also be used. Among them, those having an action of lowering the ionic strength of the reaction system of emulsion polymerization (aqueous phase of emulsion) are preferable. For example, persulfates such as ammonium persulfate and potassium persulfate are preferably used. In particular, ammonium persulfate is preferably used.

The amount of the polymerization initiator added is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 30% by mass or less, based on the total amount of the monomers, and is 10% by mass or more and 20% by mass or less. Even more preferably, it is less than or equal to%.

<Synthesis of pigment-encapsulating resin particles>
In the present invention, an emulsion containing oil droplets in water is produced by mixing a pigment, a monomer, an aqueous medium, and a surfactant, and the monomer is polymerized using a polymerization initiator. The pigment-encapsulating resin particles containing the pigment can be synthesized in a batch manner.

In the present invention, the pigment, the monomer, the surfactant and the polymerization initiator may be added to the reaction system of emulsion polymerization including the aqueous medium, and the order of addition is not particularly limited.

In the present invention, the pigment may be first added to an aqueous medium, treated with ultrasonic waves or the like to disperse, and a surfactant, a monomer, or a polymerization initiator may be added to the obtained dispersion. According to such a configuration, the emulsion polymerization performed after the pigment is dispersed can be carried out in a batch manner under gentle stirring of 300 to 500 rpm. Unlike the conventional method, pigment-encapsulating resin particles having a small particle size on the nano-order can be synthesized in the same container without performing mechanical treatment using a strong shearing force such as sonication. The work process can be simplified in comparison, and the work efficiency can be improved from this point as well.

In the present invention, the "batch type" means that the process is performed in one facility. That is, in the present invention, the synthesis of the pigment-containing resin particles containing the pigment inside by emulsion polymerization can be carried out in the reaction system in the same reaction vessel.

In the present invention, a pigment dispersion in which a high-concentration pigment is dispersed in an aqueous solvent is prepared in advance, and when the pigment-encapsulating resin particles are synthesized, the pigment dispersion is further dispersed in an aqueous medium and used. You may. Such a pigment dispersion can be prepared by treating an aqueous medium containing a pigment with ultrasonic waves or the like. A dispersant may be used to improve the dispersibility of the pigment in the pigment dispersion, and for example, a known dispersant such as a polymer-based dispersant can be used. Mechanical treatment and dispersant may be used in combination. Commercially available products may be used as such pigment dispersions, for example, Cyan BG-PT of Hostaget (trade name), Magenta E5B-PT VP 3565, Magenta E7B VP3985 S250, Yellow 4G-PT VP 2669 (Clariant), and the like. EMACOL SF CYAN AE2034F, EMACOL SF MAGENTA AE2033F, EMACOL SF YELLOW AE2032F (manufactured by Sanyo Pigment Co., Ltd.) and the like can be mentioned.

As the aqueous medium for preparing the pigment dispersion, water (for example, ion-exchanged water, distilled water, ultrapure water, etc.), a water-soluble organic solvent, or a mixture thereof can be used. From the viewpoint of safety and environmental impact, it is preferable to use water or a mixture of water and a water-soluble organic solvent.

As a method for adding the monomer to the reaction system, any method such as a monomer dropping method, a monomer batch charging method, or a pre-emulsion method (the monomer is prepared into an emulsion (pre-emulsion) for dropping and then dropped) can be used. It can be carried out. In the present invention, even if the total amount of the monomers is added to the reaction system at once by adopting the monomer batch charging method, the quality of the pigment-encapsulated resin particles to be synthesized is not impaired, and thus the work efficiency is also improved from this point. Can be planned.

The reaction vessel for carrying out emulsion polymerization in the present invention is not particularly limited, but for example, a plurality of baffles on the inner wall are shown in FIGS. 1 (A) and 1 (B), respectively. A reaction vessel having 11 and the stirring unit 12 can be used. The baffle 11 is preferably installed at a predetermined distance from the bottom surface of the container, and the stirring unit 12 preferably has a plurality of blades.

<Ink>
The ink of the present invention contains pigment-encapsulating resin particles produced by the method for producing pigment-encapsulating resin particles of the present invention. The components other than the pigment-encapsulating resin particles that can be contained in the ink of the present invention are not particularly limited, and may be any components that can be contained in ordinary inks, particularly ink jet inks. For example, the ink of the present invention may contain an aqueous solvent, a binder resin, and the like, in addition to the pigment-encapsulating resin particles produced by the method for producing pigment-encapsulating resin particles of the present invention. Other components such as penetrants, fungicides, rust preventives, pH adjusters, wetting agents, defoamers, additional surfactants, water-soluble UV absorbers, water-soluble infrared absorbers, etc. May include.

The ink of the present invention can be produced, for example, by dispersing the pigment-encapsulating resin particles produced by the method for producing pigment-encapsulating resin particles of the present invention in an aqueous medium together with a binder resin or the like. In order to improve the dispersibility between the pigment-encapsulating resin particles and the binder resin, a surfactant or the like may be added. Further, components such as a fungicide, a rust preventive, a pH adjuster, a wetting agent, an antifoaming agent, a water-soluble ultraviolet absorber, and a water-soluble infrared absorber may be added to the produced ink.

(Example 1)
200 ml of ion-exchanged water was added to 2.69 g of EMACOL SF CYAN AE2034F (manufactured by Sanyo Pigment Co., Ltd., pigment concentration 20%), which is a commercially available cyan pigment dispersion, and ultrasonic waves were applied for 30 minutes to disperse the pigment in the ion-exchanged water. After that, 18.6 mg (0.050 mmol) of sodium octadecyl sulfate was added. The obtained aqueous solution (220 ml) was poured into a half-liter four-mouth separate reactor (inner diameter 7.5 cm) which had been preheated in a constant temperature bath at 70 ° C. The four-neck separate reactor is equipped with an aren cooling pipe, a nitrogen gas inflow pipe and a mechanical stirrer, and further has four baffles (0.7 cm wide) and four blade pitch paddle impellers located 1 cm above the bottom. It was equipped with (length 5 cm). The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Then, 7.80 g (74.9 mmol) of styrene monomer was added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes in a nitrogen atmosphere (360 rpm). In order to initiate emulsion polymerization, a 30 ml aqueous solution of ammonium persulfate in which 1.14 g of ammonium persulfate was dissolved was prepared and added to a four-mouth separate reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed using a field-emission scanning electron microscope (FE-SEM: S-5000, manufactured by Hitachi, Ltd.), it was composed of spherical pigment-encapsulating fine particles having a uniform particle size. It was (Fig. 2). Further, when the particle size of the obtained pigment-encapsulating fine particles was measured with a dynamic light scattering measuring device (DLS measuring device: ZETASIER Nano manufactured by Malvern), the volume average particle size (DLS) was 84.2 nm. .. Moreover, when the particle size (diameter) of 30 pigment-encapsulating fine particles was measured on the FE-SEM photograph and the average value was calculated, the average particle size (FE-SEM) was 100 nm.

(Example 2)
To 2.69 g of the same commercially available cyan pigment dispersion as in Example 1, 200 ml of ion-exchanged water was added, ultrasonic waves were applied for 30 minutes to disperse the pigment in ion-exchanged water, and then 18.6 mg of sodium octadecyl sulfate was added. It was. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor preheated in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of methyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 3).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device and FE-SEM in the same manner as in Example 1, the volume average particle size (DLS) was 86.3 nm and the average particle size (FE-SEM), respectively. SEM) was 100 nm.

(Example 3)
To 2.69 g of the same commercially available cyan pigment dispersion as in Example 1, 200 ml of ion-exchanged water was added, ultrasonic waves were applied for 30 minutes to disperse the pigment in ion-exchanged water, and then 18.6 mg of sodium octadecyl sulfate was added. It was. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor that had been warmed in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of glycidyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 4).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device and an FE-SEM in the same manner as in Example 1, the volume average particle size (DLS) was 109 nm and the average particle size (FE-SEM), respectively. It was 110 nm.

(Example 4)
200 ml of ion-exchanged water is added to 2.69 g of EMACOL SF MAGENTA AE2033F (manufactured by Sanyo Pigment Co., Ltd., pigment concentration 20%), which is a commercially available magenta pigment dispersion, and the pigment is dispersed in the ion-exchanged water by applying ultrasonic waves for 30 minutes. After that, 18.6 mg of sodium octadecyl sulfate was added. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor that had been warmed in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of methyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 5).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device in the same manner as in Example 1, the volume average particle size (DLS) was 92.7 nm.

(Example 5)
200 ml of ion-exchanged water is added to 2.69 g of EMACOL SF YELLOW AE2032F (manufactured by Sanyo Pigment Co., Ltd., pigment concentration 20%), which is a commercially available yellow pigment dispersion, and ultrasonic waves are applied for 30 minutes to disperse the pigment in the ion-exchanged water. After that, 18.6 mg of sodium octadecyl sulfate was added. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor that had been warmed in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of methyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 6).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device in the same manner as in Example 1, the volume average particle size (DLS) was 86.2 nm.

(Example 6)
Add 200 ml of ion-exchanged water to 1.345 g each of the same commercially available magenta pigment dispersion as in Example 4 and 1.345 g each of the same commercially available yellow pigment dispersion as in Example 5, and ultrasonically for 30 minutes. After dispersing the pigment in ion-exchanged water, 9.3 mg of sodium octadecyl sulfate was added. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor that had been warmed in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of methyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 7).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device in the same manner as in Example 1, the volume average particle size (DLS) was 112 nm.

(Example 7)
1.345 g each of the same commercially available cyan pigment dispersion as in Example 1 and the same commercially available yellow pigment dispersion as in Example 5, 200 ml of ion-exchanged water was added to a total of 2.69 g, and ultrasonic waves were used for 30 minutes. After dispersing the pigment in ion-exchanged water, 9.3 mg of sodium octadecyl sulfate was added. The obtained aqueous solution (220 ml) was poured into a four-mouth separate reactor that had been warmed in the same manner as in Example 1. The aqueous solution was bubbled with nitrogen gas for 30 minutes while stirring at 360 rpm. Next, 3.90 g of styrene monomer and 3.75 g of methyl methacrylate were added to the aqueous solution at one time, and the aqueous solution was stirred for 20 minutes under a nitrogen atmosphere. In order to initiate emulsion polymerization, 30 ml of ammonium persulfate aqueous solution in which 1.14 g of ammonium persulfate was dissolved was prepared and added to the reactor at one time. Polymerization was carried out at 70 ° C. for 6 hours while stirring at 360 rpm in a nitrogen atmosphere.

When the morphology of the obtained pigment-encapsulating fine particles was observed by FE-SEM, it was composed of spherical pigment-encapsulating fine particles having a uniform particle size (FIG. 8).

When the particle size of the obtained pigment-encapsulating machine particles was measured with a DLS measuring device in the same manner as in Example 1, the volume average particle size (DLS) was 89.5 nm.

The production method according to the present invention can be suitably used for producing pigments of inks (particularly ink for inkjet), for example. The pigment-encapsulating resin particles according to the present invention can be suitably used as a pigment for ink (particularly ink for inkjet), for example. The ink according to the present invention can be suitably used as an ink jet ink.

1 Reaction vessel 11 Baffle 12 Stirrer

Claims (8)

A method for producing pigment-encapsulating resin particles.
The pigment-encapsulating resin particles are synthesized in a batch manner in an emulsion containing a pigment, an aqueous medium, a monomer, a low CMC surfactant, and a polymerization initiator.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
Production method. A method for producing pigment-encapsulating resin particles.
(A) A step of dispersing a pigment in an aqueous medium to prepare a pigment dispersion liquid, and
(B) A step of preparing a mixture of the pigment dispersion liquid and a surfactant, and
(C) A step of adding a monomer to the mixture to form an emulsion, and
(D) Including a step of adding a polymerization initiator to the emulsion and emulsion-polymerizing the monomer to synthesize pigment-encapsulating resin particles.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The surfactant is a low CMC surfactant,
The steps (B), (C) and (D) are carried out in the same reaction vessel.
Production method. The production method according to claim 2, wherein the steps (B), (C), and (D) are carried out under stirring of 300 rpm or more and 500 rpm or less. The production method according to any one of claims 1 to 3, wherein the low CMC surfactant is an anionic surfactant having a linear alkyl group having 15 to 23 carbon atoms. The production method according to any one of claims 1 to 4, wherein the polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion. A method for producing pigment-encapsulating resin particles.
The pigment-encapsulating resin particles are synthesized in a batch manner in an emulsion containing a pigment, an aqueous medium, a monomer, a surfactant, and a polymerization initiator.
The average particle size of the pigment-encapsulating resin particles is 30 nm or more and 200 nm or less.
The polymerization initiator has an action of lowering the ionic strength of the aqueous phase of the emulsion.
Production method. Pigment-encapsulating resin particles produced by the production method according to any one of claims 1 to 6. An ink containing the pigment-encapsulating resin particles according to claim 7.

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