JPH0794634B2 - Aqueous pigment dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention provides a coloring agent or a coloring agent-containing composition which does not have color separation and is used for writing inks, printing inks, paints and the like. It is a thing.

More specifically, by encapsulating two or more pigments in the same capsule, the pigment behaves in the same manner as one pigment particle, and a uniform colorant that cannot be obtained by simply combining individual pigments is provided.

(Prior art) As a coloring agent for writing ink, printing ink, paint, etc.,
An organic pigment, an inorganic pigment, and an extender pigment are used and dispersed in water by using an aqueous resin dispersion, a resin varnish such as a resin aqueous solution, or a surfactant.

The pigment may be used alone, but it is often used in combination with two or more kinds of pigments. For example, it may be used in combination with an organic pigment and an inorganic pigment, or may be used in combination with an organic pigment, an inorganic pigment and an extender pigment. In particular, a mixture of an organic pigment such as phthalocyanine blue with an inorganic pigment such as titanium white is a useful combination because it has a light color and retains strong fastness.

However, due to differences in the characteristics, particle size, surface potential, etc. of the pigments used together, even if the separation phenomenon called color separation or color float is in a dispersed state, in the final application of writing instrument ink, printing ink, paint, etc. And a lot of energy was spent on this measure.

(Problems to be Solved by the Invention) The present invention, by enclosing two or more kinds of pigments in the same capsule, exhibits the same behavior as in the case of one pigment, and causes no color separation or color floating phenomenon. It is an aqueous pigment dispersion intended for prevention.

[Structure of Invention]

(Means for Solving the Problem) The present invention is to encapsulate a core substance of an oil-based pigment dispersion containing two or more kinds of pigments, a resin and an organic solvent for dissolving the resin in a shell formed by interfacial polymerization. An aqueous pigment dispersion prepared by mixing an aqueous resin dispersion or a water-soluble resin aqueous solution as needed. Furthermore, the capsule is 0.2-10μ
An aqueous pigment dispersion having a particle size of m.

The core substance in the present invention is an oil-based pigment dispersion containing two or more pigments, a resin, and an organic solvent that dissolves the resin. Other examples of this oil-based pigment dispersion include dyes,
It may contain additives and the like.

As a pigment, inks for writing instruments, printing inks,
Pigments used for paints, recording materials, etc. are used, for example, zinc yellow, yellow iron oxide, Hansa yellow, disazo yellow, quinoline yellow, permanent yellow, permanent red, red iron oxide, resole red, watchyan red Ca salt, Watchyan red Mn salt, pyrazolone red, laked C, lake killed D, brilliant carmine 6B, brilliant carmine 3B, dark blue, phthalocyanine blue, metal-free phthalocyanine, titanium oxide, carbon black, etc.

As the resin, those having a function of satisfactorily dispersing the pigment are preferable, for example, ethylene-vinyl acetate copolymer, polystyrene type, styrene and acrylic acid ester,
Copolymer system containing styrene with methacrylic acid ester, acrylonitrile or maleic acid ester, polyacrylic acid ester type, polymethacrylic acid ester type,
Examples thereof include polyester-based, polyamide-based, polyvinyl acetate-based, epoxy-based, phenol-based, hydrocarbon-based, rosin, rosin-modified resins, petroleum-based resins, etc. These may be used alone or in combination. You can

Further, the solvent is preferably one that dissolves or swells the above resin, and even a solvent that does not dissolve the resin can be used as a part of the solvent.

As the solvent, hydrocarbon solvents such as phthalate ester, phosphate ester, fatty acid ester, benzoate ester, citrate ester, diarylalkane, alkyl phenyl ether, polybutene, vegetable oil, toluene, xylene, etc. Etc. can be used.

The core substance of the present invention may contain various additives, if desired, and examples thereof include various waxes and silicon compounds.

The above-mentioned core substance is obtained by heating or cooling the pigment, resin, solvent, other additives and the like with a dispersing machine such as a ball mill, an attritor, a dyno mill, or a three roll mill, if necessary.

In the present invention, the interfacial polymerization is carried out by dissolving and dispersing a hydrophobic polymerizable compound in the core substance, mixing and stirring with an aqueous medium containing a dispersion stabilizer to emulsify, and after emulsification, using a hydrophilic polymerizable compound. Polymerization with a hydrophobic polymerizable compound is performed.

Examples of the hydrophobic polymerizable compound include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate,
Dimethoxybiphenyl diisocyanate, dimethyldiphenylmethane diisocyanate, xylylene diisocyanate, diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, butylene diisocyanate, ethylidine diisocyanate, cyclohexylene diisocyanate, toluylene diisocyanate,
Triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, dimethyldiphenylmethane tetraisocyanate, prepolymer of polyisocyanate, tetramethylene diisocyanate, hexamethylene diisothiocyanate, p-phenylene diisothiocyanate, xylene-1,4-diisothiocyanate, Urethane-based and urea resin-based shell-forming compounds such as ethylidyne diisocyanate, epoxy-based shell-forming compounds marketed under the trade name of Epicoat, oxazoloyl chloride, succinoyl chloride, adipoyl chloride, Sebacoyl chloride, phthaloyl chloride, isophthaloyl chloride, fumaroyl chloride, cyclohexanedicarbonyl chloride, poly with acid chloride groups Stell, polyamide, benzenedisulfonyl chloride, naphthalenedisulfonyl chloride, oxybisbenzenedisulfonyl chloride, hexanedisulfonyl chloride, ethylenebis (chloroformate), tetramethylenebis (chloroformate), 2,2'-dimethyl- Polyamide-based shell-forming compounds such as 1,3-propanebis (chloroformate) and p-propanebis (chloroformate) are used.
They can be used alone or in combination of two or more.

These compounds can be added when preparing a dissolved dispersion of the core substance,
Immediately before mixing and stirring with water having a dispersion stabilizer, it is preferable to add the solution to the core material dissolved dispersion. The solution dispersion prepared by mixing the core substance and the polymerizable compound is mixed and stirred with an aqueous medium having a dispersion stabilizer.

As the dispersion stabilizer, polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose gum, fine silica powder,
Examples include water-soluble polymer compounds such as sodium lauryl sulfate and sodium oleate, metal oxides, anionic surfactants, nonionic surfactants, and cationic surfactants. These dispersion stabilizers have the function of making the particles fine and uniform in particle size.

Mixing and stirring can be carried out by adding a dispersion liquid of the core substance to an aqueous medium having a dispersion stabilizer, or conversely, adding an aqueous medium having a dispersion stabilizer to the dissolution dispersion liquid. it can.

The mixing and stirring can be performed with a high speed stirrer, an ultrasonic disperser, or the like. A homomixer, a homogenizer, a colloid mill, a homodisper, etc. can be used as the high-speed stirrer, and stirring is performed for several thousand revolutions or more.

The above-mentioned emulsification by mixing and stirring can be carried out at room temperature, but if necessary, conditions such as heating, depressurization or pressurization can be added.

When isocyanate is used as the hydrophobic polymer compound, it is preferable to heat the mixture in the presence of a catalyst after emulsification to react the isocyanate with water in order to strengthen the capsule membrane.

In addition, when the viscosity of the core substance is reduced by using a low-viscosity solvent in order to reduce the particle size by the mixing and stirring, heating may be performed for the purpose of removing the low-viscosity solvent from the core substance. It is valid.

As described above, the atomized spherical core substance is produced in the aqueous medium.

While continuing the gentle stirring to such an extent that the core substance in the aqueous medium does not precipitate, a hydrophilic polymerizable compound which polymerizes with the hydrophobic polymerizable compound is added thereto.

Hydrophilic compounds that undergo such a polymerization reaction include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, phenylenediamine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylene. Polyamine such as pentane, piperazine, methylpiperazine, piperazine of dimethylpiperazine, ethylene glycol, catechol, resorcinol, hydroquinone, dihydroxymethylbenzene, dihydroxyethylbenzene, naphthalenediol, polythiol and the like are used.

This polymerization reaction proceeds even at room temperature, but it can be heated.

When a polybasic acid is used as the hydrophobic polymerizable compound, it is preferable to add a small amount of an acid neutralizing agent such as sodium carbonate.

After the completion of the polymerization reaction, the remaining hydrophilic polymerizable compound, dispersion stabilizer and the like can be washed if necessary. Examples of the washing include washing with water and washing with warm water by decantation performed 3 to 4 times or centrifugation.

The aqueous pigment dispersion obtained as described above can be used as a coloring agent for writing instrument inks, printing inks, paints, recording liquids and the like. In other words, this aqueous pigment dispersion
By adding it to resin varnish, etc., inks, paints and recording liquids without color separation can be obtained.

Further, the obtained aqueous pigment dispersion is added with an aqueous resin dispersion,
It is also possible to mix an aqueous solution of a water-soluble resin or the like to form a composition close to that of ink or the like, or to form an ink or the like. That is,
The particles encapsulated by the interfacial polymerization are mixed with an aqueous resin dispersion liquid in which resin fine particles that become hydrophobic when dried are dispersed in water, and the resin in the resin dispersion liquid is attached to the outer surface of the capsule, Coat the capsules.

As such an aqueous resin dispersion, a dispersion produced by emulsion polymerization can be used as it is or after being concentrated. In addition, a dispersion obtained by soap-free emulsion polymerization can also be used. For example, JP-A-58
-127702,59-1503,59-199703, etc., which are obtained by the technique disclosed in
It is preferable that the particles have a spherical shape of about 0.01 to 1 μm and have a uniform particle diameter so that a uniform film can be obtained.

For example, the resin in the resin dispersion liquid may be a styrene-methylmethacrylate copolymer, an isobutylmethacrylate-methylmethacrylate copolymer, or the like.

It is also effective to use two or more types of aqueous resin dispersions or the like for the purpose of changing the properties of the outer surface in a multifaceted manner with resin fine particles having different properties.

The following vinyl-based monomers may be used for polymerization.

That is, as the vinyl monomer, styrene, vinyltoluene, 2-methylstyrene, styrene monomer such as t-butylstyrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, Acrylic acid or methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and 2-ethylhexyl methacrylate, monobasic acids such as acrylic acid, methacrylic acid and crotonic acid, fumaric acid, itacone Acids, dibasic acids such as maleic acid or their anhydrides, ethylenically unsaturated carboxylic acid monomers, N-methylol acrylamide, N-methylol methacrylamide, N-butoxymethyl N-substituted (meth) acrylic monomers such as crylamide and N-butoxymethylmethacrylamide, hydroxyl group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate, glycidyl acrylate and glycidyl methacrylate The epoxy group-containing monomer and the like.

The above resin dispersion is a capsule 100 obtained by interfacial polymerization.
About 0.3 to 10 parts by weight is used as a solid content ratio to parts by weight. If it is 0.3 parts by weight or less, the surface of the capsule cannot be sufficiently covered, and if it is 10 parts by weight or more, the effect just added cannot be obtained. In addition, the capsules may aggregate with each other.

In addition, after mixing the dispersion liquid of the capsule obtained by interfacial polymerization with the aqueous resin dispersion liquid, by adding a solvent, adjusting PH, adding heating or cooling agglomeration, charging particles, etc. An operation of adhering the resin in the aqueous resin dispersion may be used.

Examples of the present invention will be described below. In the examples, “part” means “part by weight”.

Example 1 (1) Preparation of Oily Pigment Dispersion TYPURE R-900 (DuPont Japan Inorganic Pigment) 1
0 parts Rionol Blue SM (organic pigment manufactured by Toyo Ink Mfg. Co., Ltd.) 10 parts Tamanol 350 (rosin modified phenolic resin manufactured by Arakawa Chemical Industry Co., Ltd.) 10 parts Swazol 1000 (high boiling organic solvent manufactured by Maruzen Petroleum Co., Ltd.) Ten
Parts The mixture of the above formulation was dispersed with a three-roll mill to obtain a soft oily pigment dispersion.

(2) Preparation of Oily Pigment Dispersion Diluent Mix 10 parts of the above oily pigment dispersion, Swazol 1000 50 parts Millionate MR-200 (isocyanate manufactured by Nippon Polyurethane Industry Co., Ltd.) 10 parts, and a low viscosity oily pigment dispersion diluent Got

(3) Emulsified Emulgen 913 (Nonion activator manufactured by Kao Co., Ltd.) 15 parts Water 300 parts aqueous solution is stirred with a high-speed mixer (tabletop high-speed mixer manufactured by Tokushu Kika Kogyo Co., Ltd.) at 4000 rpm while being an oil-based pigment. 70 parts of the dispersion diluted solution was added dropwise over 10 minutes, and after completion of the addition, stirring was continued for 10 minutes to emulsify.

(4) Encapsulation After emulsification, 40 parts of a 10% aqueous solution of diethylenetriamine was added at the same rotation speed, stirring was continued for 1 hour, and an interfacial polymerization reaction was performed to obtain a microcapsule aqueous pigment dispersion with the oily pigment dispersion as the core substance. It was

This aqueous pigment dispersion has a pH of 9.7, a tube gauge of 10 μm or less,
Microscopic observation The average particle size was 1.5 μm, the solid content was 6.5%, and the viscosity was 13 cps.

Example 2 (1) Preparation of Oily Pigment Dispersion TYPURE R-101 (DuPont Japan Inorganic Pigment) 10
Part Brilliant Carmine 6B (organic pigment manufactured by Toyo Ink Mfg. Co., Ltd.) 10 parts ester gum AAG (rosin ester manufactured by Arakawa Chemical Industry Co., Ltd.) 10 parts polybutene oil (LV-10 manufactured by Nippon Oil Co., Ltd.) 10 parts xylene 5 An oily pigment dispersion was obtained in the same manner as in Example 1.

(2) Preparation of Oily Pigment Dispersion Diluent 10 parts oily pigment dispersion 10 parts xylene 50 parts Coronate L (isocyanate manufactured by Nippon Polyurethane Industry Co., Ltd.) 10 parts were mixed to obtain a low viscosity oily pigment dispersion diluent.

(3) Emulsification Demol N (anion activator manufactured by Kao Corporation) 20 parts Water An aqueous solution of 300 parts was prepared and emulsified in the same manner as in Example 1.

(4) Encapsulation After emulsification, 40 parts of a 10% hexamethylenediamine aqueous solution was added while the rotation speed was maintained, and a microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained in the same manner as in Example 1.

This aqueous pigment dispersion has a pH of 9.3, a tube gauge of 10 μm or less,
The viscosity was 20 cps.

Example 3 (1) Preparation of oily pigment dispersion TYPURE R-101 10 parts Lionol Yellow GG toner (organic pigment manufactured by Toyo Ink Mfg. Co., Ltd.) 10 parts Byron 300 (polyester resin manufactured by Toyobo Co., Ltd.) 10 parts Toluene 20 parts Ethyl acetate 5 parts The mixture of the above formulation was dispersed with an attritor to obtain a soft oily pigment dispersion.

(2) Preparation of Oily Pigment Dispersion Diluent Mix 15 parts of the above oily pigment dispersion, 30 parts of toluene, 5 parts of ethyl acetate, 10 parts of Slack 1160 (isocyanate manufactured by Nippon Polyurethane Industry Co., Ltd.) to dilute the oily pigment dispersion of low viscosity. A liquid was obtained.

(3) Emulsification Hydroxyethylcellulose BG-15 (manufactured by Fuji Chemical Co., Ltd.) 0.5 part Emulgen A-60 (Kao Co., Ltd. nonionic activator) 5 parts Water 300 parts An aqueous solution was prepared in the same manner as in Example 1. , Emulsified.

(4) Encapsulation Example 1 using 10% triethylenetetramine aqueous solution
Similarly to the above, a microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained.

This aqueous pigment dispersion has a pH of 9.5, a tube gauge of 10 μm or less,
Microscopic observation revealed an average particle size of 1.3 μm and a viscosity of 12 cps.

Example 4 (1) Preparation of oil-based pigment dispersion Chromium Yellow NEO5GS (inorganic pigment manufactured by Nippon Inorganic Chemical Co., Ltd.)
15 parts Rionol Blue SM 5 parts Petrosin 120 (petroleum resin manufactured by Mitsui Petrochemical Co., Ltd.) 7 parts Toluene 20 parts were treated in the same manner as in Example 3 to obtain an oily pigment dispersion.

(2) Preparation of Oily Pigment Dispersion Diluent The above oily pigment dispersion 10 parts Toluene 50 parts Desmodur R (isocyanate from Bayer) 10 parts were mixed to obtain a low viscosity oily pigment dispersion diluent.

(3) Emulsification 5 parts of PVA-205 (polyvinyl alcohol manufactured by Kuraray Co., Ltd.) An aqueous solution of 300 parts of water was prepared and emulsified in the same manner as in Example 1.

(4) Encapsulation Using 40 parts of a 10% aqueous piperazine solution, and in the same manner as in Example 1, a microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained.

This aqueous pigment dispersion has a pH of 9.2, a tube gauge of 10 μm or less,
Microscopic observation showed an average particle size of 3.7 μm and a viscosity of 16 cps.

Example 5 (1) Preparation of Oily Pigment Dispersion TYPURE R-900 10 parts Chrome Yellow NEO5GS 10 parts Rionol Blue SM 5 parts Eva Flex 40 (ethylene vinyl acetate resin manufactured by Mitsui Polychemical Co., Ltd.) 5 parts Dioctyl phthalate 10 parts An oily pigment dispersion was obtained in the same manner as in Example 1 except that 10 parts of xylene was used.

(2) Preparation of Oily Pigment Dispersion Dilution Liquid The above oily pigment dispersion 10 parts xylene 50 parts Desmodur R 10 parts were mixed to obtain a low viscosity oily pigment dispersion dilution liquid.

(3) Emulsification In the same manner as in Example 1, emulsification was performed.

(4) Encapsulation A microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained in the same manner as in Example 1 except that a 15% resorcinol aqueous solution was used and heated at 50 ° C.

This aqueous pigment dispersion has a pH of 6.3, a tube gauge of 10 μm or less,
Microscopic observation revealed an average particle size of 5.6 μm and a viscosity of 35 cps.

Example 6 (1) Preparation of oil-based pigment dispersion Mapico Red R516L (Inorganic pigment manufactured by Titanium Industry Co., Ltd.) 2
Part Thai Pure R900 10 parts Raven 420 (Colombian carbon inorganic pigment 10 parts Paraloid B-66 (Rohm & Haas methacrylic acid resin) 5 parts Toluene 20 parts were dispersed in a hole mill to obtain an oily pigment dispersion.

(2) Preparation of oil-based pigment dispersion dilution liquid 10 parts of the above-mentioned oil-based pigment dispersion, 40 parts of toluene, 10 parts of methyl ethyl ketone, Millionate MT (10 parts of isocyanate manufactured by Nippon Polyurethane Industry Co., Ltd.) were mixed to prepare a low-viscosity oil-based pigment dispersion dilution liquid. Obtained.

(3) Emulsification In the same manner as in Example 1, emulsification was performed.

(4) Encapsulation In the same manner as in Example 1, a microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained.

This aqueous pigment dispersion has a pH of 9.2, a tube gauge of 10 μm or less,
Microscopic observation revealed an average particle size of 1.9 μm and a viscosity of 18 cps.

Example 7 (1) Preparation of Oily Pigment Dispersion TYPURE R900 10 parts Chrome Yellow NEO5GS 10 parts Brilliant Carmine 6B 2 parts Thermolite P (Seiko Chemical Co., Ltd. sensitized rubber) 5 parts Toluene 25 parts dispersed in a hall mill Then, an oily pigment dispersion was obtained.

(2) Preparation of Oily Pigment Dispersion Diluent 10 parts of the above oily pigment dispersion and 50 parts of toluene Millionate MT were mixed to obtain a low viscosity oily pigment dispersion diluent.

(3) Emulsification In the same manner as in Example 1, emulsification was performed.

(4) Encapsulation In the same manner as in Example 1, a microcapsule aqueous pigment dispersion having an oily pigment dispersion as a core substance was obtained.

This water-based pigment dispersion has a pH of 9.0, a tube gauge of 10 μm or less,
Microscopic observation revealed that the average particle size was 3.0 μm and the viscosity was 23 cps.

Comparative Example 1 (1) Preparation of oil-based pigment dispersion A soft oil-based pigment dispersion was obtained in the same manner as in (1) Preparation of oil-based pigment dispersion of Example 1.

(2) Preparation of Oily Pigment Dispersion Diluent 10 parts of oily pigment dispersion and 50 parts of Swazol 1000 were mixed to obtain a low viscosity oily pigment dispersion diluent.

(3) Emulsification The same operation as (3) Emulsification in Example 1 was carried out to obtain an emulsion of a low-viscosity oily pigment dispersion.

This emulsion has a pH of 7.0, a tube gauge of 10μ or less, and a microscope observation.
The average particle size was 1.7 μm and the viscosity was 21 cps.

Comparative Example 1 was stopped before the encapsulation treatment, and the effects of encapsulation can be compared.

Comparative Example 2 (1) Preparation of oil-based pigment dispersion A soft oil-based pigment dispersion was obtained in the same manner as in (2) Preparation of oil-based pigment dispersion of Example 2.

(2) Preparation of oily pigment dispersion dilution liquid 10 parts of oily pigment dispersion and 50 parts of xylene were mixed to obtain a low viscosity oily pigment dispersion dilution liquid.

(3) Emulsification The same operation as (3) Emulsification in Example 2 was carried out to obtain an emulsion of a low-viscosity oily pigment dispersion.

The emulsion had a pH of 7.1, a tube gauge of 10 μm or less, a microscopic observation, an average particle size of 2.0 μm, and a viscosity of 37 cps.

Comparative Example 3 Thai Pure R900 10 parts Lionol Blue SM 10 parts John Kryl 678, 30% Aqueous ammonia solution (Johnson styrene acrylic resin) 50 parts Water 30 parts Disperse the mixture of the above formulation with a ball mill to obtain pH 8.3, An aqueous pigment dispersion having a tub gauge of 30 μm, an average particle size of 0.13 μm and a viscosity of 470 cps was obtained.

Comparative Example 4 A mixture of 20 parts of water and 80 parts of water of the dispersion of Comparative Example 3 was prepared to have a viscosity of 15 cps, a tube gauge of 30 μm, and a pH of 7.7.
An aqueous pigment dispersion having an average particle size of 0.13 μm was obtained.

By comparing this dispersion with the dispersion of Example 1, the effect of encapsulation can be confirmed.

Comparative Example 5 TYPURE R101 10 parts Brilliant Carmine 6B 10 parts Emulgen A-60 5 parts Demol N 1 part Water 74 parts A mixture of the above formulation was dispersed in a sand mill, pH 7.8, Tube gauge 10 μm or less, average particle size 0.15 μm, An aqueous pigment dispersion having a viscosity of 37 cps was obtained.

Comparative Example 6 Chromium Yellow NEO5GS 15 parts Lionol Blue SM 5 parts Marquide No32, 30% aqueous ammonia solution (rosin modified maleic acid resin manufactured by Arakawa Chemical Industry Co., Ltd.) 30 parts Casein 15% aqueous ammonia solution 30 parts Water 20 parts Mixture of the above formulation Was dispersed with an attritor to obtain an aqueous pigment dispersion having a pH of 8.8, a Tube gauge of 10 μm or less, an average particle size of 0.20 μm and a viscosity of 830 cps.

Comparative Example 7 Thai Pure R900 10 parts Chrome Yellow NEO5GS 10 parts Rionol Blue SM 5 parts Casein 15% Aqueous Ammonia Solution 30 parts Stilite CM15 Ammonia Aqueous Solution (Daido Kogyo Styrene-Manic Acid Resin) 10 parts Water 39 parts Mixture of the above formulation in a ball mill Dispersion was performed to obtain an aqueous pigment dispersion having a pH of 8.5, a tube gauge of 30 μm, an average particle size of 0.32 μm and a viscosity of 2150 cps.

Comparative Example 8 Mapico Red R516L 2 parts TYPURE R900 10 parts Raven 420 10 parts SYNCHRIL 74J (Johnson Co. acrylic resin) 40
Parts water 40 parts The mixture of the above formulation was dispersed by a sand mill to obtain an aqueous pigment dispersion having a pH of 8.2, a tube gauge of 10 μm, an average particle size of 0.28 μm and a viscosity of 47 cps.

* 1. Measurement with BL type viscometer (manufactured by Tokyo Keiki) * 2. Observation of coarse particles with a tube gauge The coarse particles of the dispersion were observed by a method according to JIS K-5400.

* 3. Drop the dispersion on the glass plate and press down with the cover glass. The average particle size was determined by examining the particle size in 20 fields per field and 5 fields under an optical microscope of 500 times.

* 4. The average particle size of pigment particles in the dispersion was determined using a centrifugal sedimentation type particle size distribution analyzer (manufactured by Shimadzu Corporation).

* 5. The sample was put up to a height of 290 mm in a tester with a 300 mm height stopper and stored in a test tube stand at a constant temperature of 50 ° C.

After 30 days, the dispersion was separated, precipitated, and colored. After the observation, the particles were returned to the dispersed state by vigorous shaking and the particle size was measured.

Claims (2)

[Claims] 1. A core substance of an oil-based pigment dispersion containing two or more pigments, a resin and an organic solvent capable of dissolving the resin is encapsulated in a shell formed by interfacial polymerization, and an aqueous resin dispersion is formed if necessary. Body or a water-soluble resin aqueous solution is mixed to prepare an aqueous pigment dispersion. 2. The aqueous pigment dispersion according to claim 1, wherein the capsule has a particle size of 0.2 to 10 μm.