JP2016169285A - Method for producing processed pigment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an organic pigment that can be applied also to a printer mounted with a high-resolution inkjet head and in which coarse particles have been subjected to a reduction treatment.SOLUTION: A method for producing a processed pigment includes: a step 1 of kneading a crude pigment, a water-soluble inorganic salt, and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt; a step 2 of adding the water-soluble inorganic salt, the water-soluble organic solvent and an acrylic resin; and a step 3 of removing the water-soluble inorganic salt and the water-soluble organic solvent. A relationship between the step 1 and the step 2 satisfies expression (1), and an amount of the acrylic resin after the step 2 to be added is in a range of 3-10 mass% with respect to the crude pigment. 0.14<time required for step 1/(time required for step 1+time required for step 2)<0.93SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a treated pigment.

  Pigment compositions that use organic pigments as coloring materials make use of the excellent light resistance of organic pigments, both in and outside the paint field for automobiles and building materials, offset ink, gravure ink, flexo ink, silk It is used in various applications such as printing ink fields such as screen inks, ink-jet recording ink fields, and color filter color resists. In particular, organic pigments used for high-functional applications such as ink-jet recording ink fields and color resists for color filters require higher-quality printing than general-purpose organic pigments used for coloring paints and printing inks. Therefore, there is a demand for finer pigments.

  As a method for obtaining a fine organic pigment, for example, a crude pigment is mixed with a kneader together with a synthetic resin that is solid and water-insoluble at room temperature, a water-soluble inorganic salt such as sodium chloride, and a water-soluble organic solvent that at least partially dissolves the synthetic resin. (Hereinafter, kneading a mixture containing a crude pigment, a water-soluble inorganic salt, and a water-soluble organic solvent is referred to as salt milling), followed by washing with water to obtain a water-soluble inorganic salt and a water-soluble organic solvent. (For example, refer to Patent Documents 1 to 3). In this method, since the primary particles are pulverized and crystal growth occurs in parallel, an organic pigment having a small particle size distribution and a small surface area is finally obtained.

  The above method is an excellent method for obtaining a fine organic pigment, but sometimes a large number of coarse particles are generated. Coarse particles become a problem particularly when the application is ink for ink jet recording, and causes nozzle clogging of the ink jet head. In particular, along with the recent increase in resolution of ink jet printers, the density of ink jet head nozzles and droplets have become finer, that is, the nozzle diameter for ejecting ink has become smaller and more highly integrated (see, for example, Patent Document 4). ). As the nozzle diameter becomes smaller, the size of allowable foreign matter also becomes smaller, resulting in increased nozzle clogging. In other words, the ink that could be applied to a conventional inkjet printer is a newly developed high-resolution inkjet head. There arises a problem that the printer cannot be used.

Japanese Patent Laid-Open No. 05-043704 Japanese Patent Laid-Open No. 7-13016 JP 2009-144126 A JP2013-993A

  An object of the present invention is to provide a method for producing an organic pigment in which coarse particles are reduced, which can be applied to a printer equipped with a high-resolution inkjet head.

  In the salt milling process, the present inventors have found that the synthetic resin to be used affects the generation of coarse particles, and by specifying the type and amount of the synthetic resin to be used, and the timing of addition, the problem described above Solved.

That is, the present invention includes a step 1 of kneading a crude pigment, a water-soluble inorganic salt, and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt;
Step 2 of adding the water-soluble inorganic salt, the water-soluble organic solvent and the acrylic resin,
Step 3 for removing the water-soluble inorganic salt and the water-soluble organic solvent,
The relationship between the step 1 and the step 2 satisfies the formula (1), and
Provided is a method for producing a treated pigment, wherein the addition amount of the acrylic resin after the step 2 is in the range of 3 to 10% by mass with respect to the crude pigment.

（１）

(1)

  The pigment obtained by the production method of the present invention has reduced coarse particles even after being dispersed in an aqueous medium, and can be suitably used for inks that can be applied to a printer equipped with a high-resolution inkjet head. it can.

(Coarse pigment)
In the present invention, the crude pigment refers to particles that have a primary particle size larger than that of organic pigments generally used as a color material and are not suitable as a color material. For example, the specific surface area takes a significantly smaller value than the organic pigment.
Phthalocyanine synthesized by the Weiler method or the phthalonitrile method has a large primary particle size as it is and is not suitable as a coloring material, and is called a crude pigment. Also called crude crude, or simply crude. By kneading the crude pigment with a water-soluble inorganic salt and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt, the crude pigment can be made fine enough to be applied as a coloring material. In the present application, the crude pigment is kneaded with a water-soluble inorganic salt and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt, and is refined to such a degree that it can be applied as a coloring material. .
And the pigment which surface-treated in order to provide the kneading pigment with the suitability according to each use is called a treated pigment. The pigment of the present invention is characterized in that surface treatment for application suitability was simultaneously performed during kneading.

  The crude pigment used in the present invention is not particularly limited, and those used as organic pigments for water-based inkjet recording inks can be used. Specifically, known organic pigments that can be dispersed in water or water-soluble organic solvents can be used. Specifically, azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigos) Pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye-type chelates, acidic dye-type chelates), nitro pigments, nitroso pigments, aniline black, and the like.

  For example, specific examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like.

  Specific examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, etc. It is done.

  Specific examples of pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 5, 15: 6, 16, 22, 60, 63, 66, and the like.

In the present invention, the coarse pigment may have any particle size, but in the dry powder, it is preferable that the average particle size of the primary particles is 100 nm or less because a clearer colored product can be easily obtained.
The average particle diameter of primary particles is measured as follows. First, the particle | grains in a visual field are image | photographed with a transmission electron microscope or a scanning electron microscope. And the longest length (maximum length) of the internal diameter of each particle | grain is calculated | required about 50 of the primary particles which comprise the aggregate on a two-dimensional image. The average value of the maximum length of each particle is defined as the average particle size of the primary particles.

(Water-soluble inorganic salt)
As the water-soluble inorganic salt used in the present invention, it is preferable to use inorganic salts such as sodium chloride, potassium chloride, sodium sulfate and the like. Moreover, it is more preferable to use an inorganic salt having an average particle size of 0.5 to 50 μm. Such an inorganic salt can be easily obtained by pulverizing a normal inorganic salt.

(Water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt)
As the water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt used in the present invention (hereinafter sometimes simply referred to as “water-soluble organic solvent”), those capable of suppressing crystal growth of organic pigments are suitable. For example, diethylene glycol, glycerin, ethylene glycol, propylene glycol, liquid polyethylene glycol, liquid polypropylene glycol, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyl) Oxy) ethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, 1-methoxy-2-propanol, 1 Use ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol, triethylene glycol, polyethylene glycol, 1,2-propanediol, 1-methoxy-2-propanol, etc. However, ethylene glycol or diethylene glycol is preferred.

(Acrylic resin)
Examples of the acrylic resin used in the present invention include styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, (meth) acrylic acid ester- (meta ) Styrene monomers such as acrylic acid copolymers and styrene-acrylic acid copolymers containing (meth) acrylic acid as a raw material monomer. In the present invention, the “styrene-acrylic acid copolymer” is defined as “a copolymer containing a styrene monomer and (meth) acrylic acid as a raw material monomer” as described above. Therefore, a general-purpose monomer other than the styrene monomer and (meth) acrylic acid may be copolymerized.

  The ratio of the styrene monomer used as the raw material for the styrene-acrylic acid copolymer is more preferably 50 to 90% by mass, and particularly preferably 70 to 90% by mass.

The styrene-acrylic acid copolymer is obtained by copolymerization of at least one of a styrene monomer, an acrylic acid monomer, and a methacrylic acid monomer, but it is preferable to use acrylic acid and methacrylic acid in combination. The reason is that the copolymerization at the time of resin synthesis is improved, the uniformity of the resin is improved, and as a result, the storage stability of the pigment dispersion is improved and a more finely divided pigment dispersion is obtained. This is because there is a tendency.
In the styrene-acrylic acid copolymer, the total during copolymerization of the styrene monomer, the acrylic acid monomer, and the methacrylic acid monomer is preferably 95% by mass or more based on the total monomer components.

  As a method for producing the styrene-acrylic acid copolymer, a usual polymerization method can be employed, and a method of performing a polymerization reaction in the presence of a polymerization catalyst such as solution polymerization, suspension polymerization, bulk polymerization, etc. It is done. Examples of the polymerization catalyst include 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), Examples thereof include benzoyl peroxide, dibutyl peroxide, butyl peroxybenzoate, and the amount used is preferably 0.1 to 10.0% by mass of the vinyl monomer component.

  The styrene-acrylic acid copolymer may be a random copolymer or a graft copolymer. As the graft copolymer, a copolymer of polystyrene or a nonionic monomer copolymerizable with styrene and styrene is used as a trunk or branch, and a copolymer of acrylic acid, methacrylic acid and other monomers including styrene is branched. Or the graft copolymer used as a trunk can be shown as the example. The styrene-acrylic acid copolymer may be a mixture of the graft copolymer and the random copolymer.

  In the present invention, the weight average molecular weight of the acrylic copolymer having an anionic group is preferably in the range of 5000 to 20000. For example, also when using the said styrene-acrylic-acid type copolymer, it is preferable that the weight average molecular weight exists in the range of 5000-20000, and it is more preferable that it exists in the range of 5000-18000. Especially, it is especially preferable that it exists in the range of 5500-15000. Here, the weight average molecular weight is a value measured by a GPC (gel permeation chromatography) method, and is a value converted to a molecular weight of polystyrene used as a standard substance.

  In the case of the styrene-acrylic acid copolymer used in the present invention, it has a carboxyl group derived from an acrylic acid monomer and a methacrylic acid monomer, and its acid value is preferably 50 to 300 (mgKOH / g), 60 More preferably, it is -200 (mgKOH / g).

  The acid value here is a numerical value measured in accordance with Japanese Industrial Standard “K0070: 1992. Test method for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponified product of chemical products” This is the amount (mg) of potassium hydroxide required to completely neutralize 1 g of resin. In the present invention, specifically, the acid value is measured as follows.

(Measurement method of acid value)
The acid value of the resin was determined by dissolving 0.1 g of a sample in a 7: 3 mixed solvent of methanol and toluene, and titrating with 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

  When the acid value is too low, pigment dispersion and storage stability are lowered, and when an aqueous ink for inkjet recording described later is prepared, printing stability is deteriorated, which is not preferable. If the acid value is too high, the water resistance of the colored recording image is lowered, which is also not preferable. In order to make the copolymer within the range of the acid value, (meth) acrylic acid may be included and copolymerized so as to be within the range of the acid value.

(Basic compound)
The acrylic resin is preferably neutralized with a basic compound. Known compounds can be used as the basic compound, for example, alkali metal hydroxides such as potassium and sodium; carbonates of alkali metals such as potassium and sodium; carbonates such as alkaline earth metals such as calcium and barium; Inorganic basic compounds such as ammonium hydroxide, amino alcohols such as triethanolamine, N, N-dimethanolamine, N-aminoethylethanolamine, dimethylethanolamine, NN-butyldiethanolamine, morpholine, N -Organic basic compounds such as morpholines such as methylmorpholine and N-ethylmorpholine, and piperazine such as N- (2-hydroxyethyl) piperazine and piperazine hexahydrate. Among these, alkali metal hydroxides represented by potassium hydroxide, sodium hydroxide, and lithium hydroxide are preferable, and potassium hydroxide is particularly preferable.

  Although the neutralization rate of the anionic group using these is not particularly limited, it is generally carried out in a range of 50 to 200%. In the present invention, the neutralization rate is a numerical value indicating the percentage of the basic compound blended with respect to the amount required for neutralization of all carboxyl groups in the anionic group-containing organic polymer compound. Is calculated by the following formula.

(Production method)
The production method of the present invention comprises a step 1 of kneading a crude pigment, a water-soluble inorganic salt, and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt;
Step 2 of adding the water-soluble inorganic salt, the water-soluble organic solvent and the acrylic resin,
Step 3 for removing the water-soluble inorganic salt and the water-soluble organic solvent,
The relationship between the step 1 and the step 2 satisfies the formula (1), and
The amount of the acrylic resin added after the step 2 is in the range of 3 to 10% by mass with respect to the crude pigment.

（１）

(1)

(Process 1)
In Step 1, the crude pigment, the water-soluble inorganic salt, and the water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt are each 1 part of the crude pigment, and the water-soluble inorganic salt is: It is preferably 4 to 20 parts in terms of mass, more preferably 6 to 15 parts, and the water-soluble organic solvent is preferably 0.01 to 5 parts in terms of mass and 0.1 to 3 parts. More preferably.

  The kneader used may be a known and conventional kneader. Specifically, for example, a kneader, a mix muller, a Toray manufactured by Inoue Seisakusho, which is a planetary mixer described in Japanese Patent Application Laid-Open No. 2007-100008. Miracle KCK manufactured by Asada Tekko Co., Ltd., which is a remix (trade name), a continuous twin-screw extruder described in JP-A-4-122778, and a continuous single-screw kneader described in JP-A 2006-306996 Etc. can be used.

  The temperature during kneading is preferably 10 ° C to 150 ° C, more preferably 30 ° C to 120 ° C, and most preferably 70 ° C to 110 ° C. When atomization is performed at 150 ° C. or higher, the particle growth rate may exceed the atomization rate, and the atomization may be difficult to proceed. Further, it is not preferable to atomize at 10 ° C. or lower because it becomes difficult to control due to the heat generated during atomization and the production stability is affected. The total kneading time can be any time during which the desired particle size can be obtained, but is usually 2 hours to 24 hours, and 2 hours to 15 hours are preferable in consideration of productivity. In the present invention, the total kneading time is the sum of the time required for step 1 and the time required for step 2.

(Process 2)
During the kneading, the water-soluble inorganic salt, the water-soluble organic solvent, and the acrylic resin are added. It is known that a polymer compound may be added during kneading, and is described in paragraph 0068 of Patent Document 3, for example. However, the present invention is characterized in that it is added at a timing that satisfies the formula (1).

  The formula (1) is a formula specifying the timing of adding the water-soluble inorganic salt, the water-soluble organic solvent and the acrylic resin in the total kneading time. When this formula is not satisfied, the coarse particles of the obtained treated pigment tend to increase.

  Further, the amount of the acrylic resin added at the timing satisfying the formula (1) is also in the range of 3 to 10% by mass with respect to the crude pigment, and the coarse particles of the treated pigment obtained within this range are To reduce. In particular, the amount is preferably in the range of 3 to 8% by mass, and most preferably in the range of 4 to 7% by mass.

In addition, the water-soluble inorganic salt and the water-soluble organic solvent are each preferably used in an amount of 0.1 to 10 parts in terms of mass with respect to 1 part of the crude pigment. The water-soluble organic solvent is preferably 0.01 to 5 parts, more preferably 0.1 to 1 part in terms of mass. The purpose of adding the water-soluble inorganic salt in step 2 is to keep the degree of grinding at the time of kneading at the same level as in step 1, and the purpose of adding the water-soluble organic solvent is to increase the share at the time of kneading to step 1. And keep it at the same level.
In addition, it is preferable that the total amount of the water-soluble inorganic salt does not exceed 20 parts with respect to 1 part of the crude pigment in the stage after Step 1 and Step 2, and the total amount of the water-soluble organic solvent is 10 with respect to 1 part of the crude pigment. It is preferable not to exceed the part.

  The reason why the coarse particles of the obtained treated pigment are reduced under the above conditions is estimated as follows. That is, as the grinding proceeds to some extent, the pigment is uniformly reduced in particle size, and the particle size distribution of the pigment particles becomes sharper. However, because the ground pigment particles have a high surface energy and are active, the pigment particles are attracted together to form strong aggregates. By coexisting the resin at this time, it is possible to suppress the agglomeration by suppressing the energy of the active surface of the pigment particles by grinding, to suppress the agglomeration, to enable easy dispersion of the pigment dispersion, and to process the coarse pigment Particles can be reduced.

  This method is particularly effective when a phthalocyanine pigment is used as the pigment. Examples of the phthalocyanine pigment include C.I. I. Pigment blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 5, 15: 6, 16, 22, 60, 63, 66, and the like.

(Process 3)
Step 3 for removing the water-soluble inorganic salt and the water-soluble organic solvent may be performed by a known method. Generally, it is cooled and the water-soluble inorganic salt and the water-soluble organic solvent can be removed therefrom by acid cleaning. The obtained wet cake can be further washed with water, filtered, dried, pulverized, etc. as necessary to obtain a treated pigment.

  As washing, either water washing or hot water washing can be employed. The number of washings can be repeated, for example, in the range of 1 to 5 times. By washing, it is possible to remove the acrylic resin not adsorbed on the organic pigment. If necessary, acid cleaning, alkali cleaning, and solvent cleaning may be performed so as not to change the crystal state of the pigment.

  Examples of the drying after filtration and washing described above include batch-type or continuous drying in which the pigment is dehydrated and / or desolvated by heating at 80 to 120 ° C. with a heating source installed in a dryer. Examples of the dryer used at this time include a box dryer, a band dryer, and a spray dryer. In particular, spray dry drying is preferable because a pigment that can be easily dispersed can be obtained at the time of preparing the paste. In addition, the pulverization after drying is not an operation for increasing the specific surface area and reducing the average particle diameter of the primary particles. For example, the pigment is in a lamp shape as in the case of drying using a box dryer or a band dryer. When the mixture becomes a lump or the like, the pigment is dissolved to make a powder, and examples thereof include mortar, hammer mill, disk mill, pin mill, jet mill and the like.

  In order to reduce impurities such as free metals and free metal ions, it is effective to wash the treated pigment obtained in the present invention with acids. The acids used at this time are preferably acids such as hydrochloric acid, nitric acid or sulfuric acid having a concentration of 0.3% to 10%. Moreover, the temperature at the time of washing | cleaning has preferable 50-90 degreeC. Moreover, you may wash | clean using water.

Examples of the present invention will be described in detail below.
Unless otherwise specified, “part” is “part by mass” and “%” is “% by mass”.
The resins used in the examples and comparative examples are as follows.

(Synthesis example 1 manufacturing method of acrylic resin (A-1))
100 parts of methyl ethyl ketone was charged into a reaction vessel having a stirring device, a dropping device, and a reflux device, and the inside of the reaction vessel was purged with nitrogen while stirring. The reaction vessel was heated to a methyl ethyl ketone reflux state while maintaining a nitrogen atmosphere, and then 72 parts of styrene, 12 parts of acrylic acid, 16 parts of methacrylic acid, and a polymerization catalyst (“W- 59 ") 8 parts of the mixture was added dropwise over 2 hours. In the middle of dropping, the temperature of the reaction system was kept at 80 ° C. After completion of the dropwise addition, the reaction was continued for another 25 hours at the same temperature. In the course of the reaction, a polymerization catalyst was added as appropriate while confirming the consumption of the raw materials. After completion of the reaction, methyl ethyl ketone was distilled off under reduced pressure, and the resulting solid was pulverized to obtain an acrylic acid resin (A-1) powder.
As a result, an acrylic resin (A-1) having a styrene / acrylic acid / methacrylic acid = 72/12/16 (wt%), a weight average molecular weight of 9000, and an acid value of 180 mgKOH / g was obtained.

The weight average molecular weight in the present invention is a value measured by GPC (gel permeation / chromatography) method and converted to the molecular weight of polystyrene used as a standard substance. In addition, the measurement was implemented with the following apparatuses and conditions.
Liquid feed pump: LC-9A
System controller: SCL-6B
Autoinjector: SIL-6B
Detector: RID-6A
Made by Shimadzu Corporation.
Data processing software: Sic480II data station (manufactured by System Instruments).
Column: GL-R400 (guard column) + GL-R440 + GL-R450 + GL-R400M (manufactured by Hitachi Chemical Co., Ltd.)
Elution solvent: THF
Elution flow rate: 2 ml / min

Example 1
(Processed pigment production method: Step 1)
Put 75 parts of phthalocyanine crude pigment, 90 parts of diethylene glycol, 563 parts of sodium chloride, 1.57 parts of xylene and 0.87 parts of sodium hydroxide in a double arm kneader (manufactured by Yoshida Seisakusho) and knead at 90 ° C to 95 ° C for 5 hours. did.

(Processed pigment production method: Step 2)
After Step 1, 3.75 parts of the acrylic acid resin (A-1) obtained in Synthesis Example 1, 40 parts of diethylene glycol, and 188 parts of sodium chloride were added and kneaded for 2 hours.

(Processed pigment production method: Step 3)
After Step 2, the contents were washed with 0.4% hydrochloric acid, filtered, washed with hot water at 70 ° C., filtered, and dried at 90 ° C. to obtain a pigment composition.

(Aqueous pigment dispersion manufacturing method)
50 parts of the pigment composition obtained in Example 1, 15 parts of the acrylic acid resin (A-1) obtained in Synthesis Example 1, 20 parts of triethylene glycol, and 7.99 parts of 8N potassium hydroxide have a capacity of 0.4 L. In the planetary mixer ACM-0.4LVT (Aikosha Seisakusho Co., Ltd.), the jacket was heated to 80 degrees and kneaded for 1 hour at a rotational speed of 80 rpm. Subsequently, 150 parts of ion exchange water was gradually added to the kneaded material in the stirring layer while stirring was continued, and the whole was taken out after stirring for another hour. Triethylene glycol and ion exchange water were added to this dispersion to adjust the pigment concentration to 15.45%.

(Comparative Example 1)
Example 1 (Processed pigment production method: Step 1) In Example 1, except that the kneading time was changed to 7 hours and (Processed pigment production method: Step 2) was not performed. Thus, a pigment composition and an aqueous pigment dispersion were obtained.

(Comparative Example 2)
In Example 1 (processed pigment production method: step 1), the pigment composition was changed in the same manner as in Example 1 except that kneading was started and (processed pigment production method: step 2) was started at the same time. And an aqueous pigment dispersion were obtained.

(Comparative Example 3)
In Example 1 (Processed pigment production method: Step 1), except that the kneading time was changed to 6.5 hours, and in (Processed pigment production method: Step 2), the kneading time was changed to 0.5 hours. A pigment composition and an aqueous pigment dispersion were obtained in the same manner as in Example 1.

(Comparative Example 4)
In Example 1 (Manufacturing method of treated pigment: Step 2), the addition amount “3.75 parts” of the acrylic acid resin (A-1) obtained in Synthesis Example 1 was changed to “2.25 parts”. Were the same as in Example 1 to obtain a pigment composition and an aqueous pigment dispersion.

(Comparative Example 5)
Except for changing the amount of addition of “3.75 parts” of the acrylic resin (A-1) obtained in Synthesis Example 1 to “7.5 parts” in Example 1 (Manufacturing method of treated pigment: Step 2). In the same manner as in Example 1, a pigment composition and an aqueous pigment dispersion were obtained.

(Evaluation method)
The following items were measured and evaluated for the aqueous pigment dispersions produced in Example 1 and Comparative Examples 1-5.
<Number of coarse particles immediately after preparation>
The aqueous pigment dispersions prepared in Example 1 and Comparative Examples 1 to 5 were diluted 2000 times and measured with Accusizer 780APS (manufactured by International Business). The number of coarse particles was converted to the number of particles per ml of an aqueous pigment dispersion having a pigment concentration of 14.5%.
The evaluation criteria were as shown in Table 1.

The results are shown in Table 2.

Claims (3)

Kneading a crude pigment, a water-soluble inorganic salt, and a water-soluble organic solvent that does not substantially dissolve the water-soluble inorganic salt; and
Step 2 of adding the water-soluble inorganic salt, the water-soluble organic solvent and the acrylic resin,
Step 3 for removing the water-soluble inorganic salt and the water-soluble organic solvent,
The relationship between the step 1 and the step 2 satisfies the formula (1), and
The method for producing a treated pigment, wherein the added amount of the acrylic resin after the step 2 is in the range of 3 to 10% by mass with respect to the crude pigment.

(1) The method for producing a treated pigment according to claim 1, wherein the acrylic resin has an acid value of 50 to 300 mgKOH / g and is neutralized within a range of a neutralization rate of 50 to 200%. The process for producing a treated pigment according to claim 1 or 2, wherein the crude pigment is a phthalocyanine pigment.