JP2005263864A - Preparation method of aqueous dispersion of colorant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method of an aqueous dispersion of a colorant whereby a solvent can be removed through evaporation without deteriorating a filtration property of a filter. <P>SOLUTION: In the preparation method of the aqueous dispersion of the colorant for inkjet printing, the organic solvent is removed from the dispersion containing the colorant, a water-insoluble polymer having a salt-producing group, the organic solvent and water through evaporation by heating the dispersion using a batch evaporator under a condition represented by formula (1): 30≤(B/A)×100≤100 (wherein A is the total amount (kg) of the solvent removed through evaporation; and B is the amount (kg) of the solvent removed through evaporation in a region above the upper end of a heating part of the batch evaporator). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a colorant aqueous dispersion. More specifically, the present invention relates to a method for producing a colorant aqueous dispersion that can be suitably used for an aqueous ink for inkjet recording.

  A water-based ink, particularly an inkjet recording ink, is mainly obtained by dissolving or dispersing a pigment or dye in water and / or an organic solvent in the presence of a dispersant, and then evaporating and removing the water and / or organic solvent. It is manufactured. In the case of evaporating and removing water and / or organic solvent, a batch-type evaporator that evaporates and removes water and / or organic solvent by heating the wall surface of the tank, and a stirring tank in which a stirrer is provided in the batch-type evaporator A batch evaporator and a stirring tank thin film evaporator have been proposed (see, for example, Patent Document 1).

  However, when these evaporators are used, there is a problem that the filter filterability is lowered depending on the heating method.

  In the ink jet recording system, the printer nozzle resolution has been reduced to increase the resolution of the printer, so that filter filterability is high, coarse particles such as aggregates are not mixed, and there is no clogging of the printer nozzle. Although water-based ink is required, so far, a heating method at the time of manufacturing the ink has not been studied.

Japanese Patent Laid-Open No. 2001-152053

  An object of the present invention is to provide a method for producing a colorant aqueous dispersion capable of evaporating and removing a solvent without reducing the filterability of the filter.

The present invention employs a batch-type evaporator from a dispersion containing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent, and water, using the formula (1):
30 ≦ (B / A) × 100 ≦ 100 (1)
(In the formula, A represents the total amount of solvent to be removed by evaporation (kg), and B represents the amount of solvent to be removed by evaporation in the region above the upper end of the heating part of the batch evaporator (kg)).
In the manufacturing method of the coloring agent water dispersion for inkjet recording which evaporates and removes the said organic solvent by heating on the conditions represented by these.

  According to the present invention, a colored water having excellent filter filterability can be obtained by evaporating and removing a solvent without mixing agglomerates in a dispersion containing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent and water as much as possible. Dispersions can be produced.

  In the present invention, when the solvent is removed by evaporation from a dispersion containing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent, and water, the organic solvent is used under the conditions represented by the formula (1). Is evaporated by heating.

(Coloring agent)
Examples of the colorant used in the present invention include those selected from pigments and dyes. These can be used alone or in admixture of two or more.

  The pigment and dye are not particularly limited as long as they are generally used for water-based inks.

  The pigment may be either an inorganic pigment or an organic pigment. Moreover, they and an extender can also be used together as needed.

  Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Among these, carbon black is preferable particularly for black aqueous ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Examples of extender pigments include silica, calcium carbonate, and talc.

  Examples of the dye include oily dyes, disperse dyes, aqueous dyes, direct dyes, acid dyes, and basic dyes.

  When the colorant aqueous dispersion obtained in the present invention is used in an aqueous ink for inkjet recording, a colorant selected from pigments and hydrophobic dyes is preferred because of excellent printing density and light resistance. As the hydrophobic dye, an oily dye and a disperse dye are preferable. The hydrophobic dye is desirably dissolved at 2 g / L or more, preferably 20 to 500 g / L, in an organic solvent used (for example, methyl ethyl ketone) at 25 ° C. in order to produce a stable dye dispersion.

  Examples of oil-based dyes include C.I. Solvent Black, C.I. Solvent Yellow, C.I. Solvent Red, C.I. Solvent Violet, C.I. Solvent Blue, C.I. Solvent Green, C.I. Solvent Orange, and the like.

  Examples of disperse dyes include C.I. Disperse Yellow, C.I. Disperse Orange, C.I. Disperse Red, C.I. Disperse Violet, C.I. Disperse Blue, and C.I. Disperse Green Series.

[Water-insoluble polymer having a salt-forming group]
Examples of the water-insoluble polymer having a salt-forming group include a water-insoluble vinyl polymer having a salt-forming group, a water-insoluble polyester polymer having a salt-forming group, and a water-insoluble polyurethane polymer having a salt-forming group. Among these polymers, a water-insoluble vinyl polymer having a salt-forming group is preferable.

  As the water-insoluble vinyl polymer having a salt-forming group, a polymer of a monomer mixture containing a polymerizable monomer having a carboxyl group is preferable, and one kind selected from the group consisting of (meth) acrylic acid esters and aromatic ring-containing monomers. A polymer of a monomer mixture containing the above is more preferable.

  As the polymerizable monomer having a carboxyl group, α, β-unsaturated carboxylic acid is preferable, and (meth) acrylic acid is more preferable.

  The content of the monomer having a carboxyl group in the monomer mixture is preferably 3 to 50% by weight, more preferably 10 to 35% by weight, from the viewpoint of high printing density.

As (meth) acrylic acid ester, for example, the ester moiety such as methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate has a carbon number. The (meth) acrylic acid ester which is a 1-18 alkyl group is mentioned.
Styrene is preferred as the aromatic ring-containing monomer.

  The total content of the (meth) acrylic acid ester and the aromatic ring-containing monomer in the monomer mixture is preferably 50 to 97% by weight, more preferably 65 to 90% by weight, from the viewpoint of stably dispersing the pigment. The monomer mixture may contain other monomers as long as the object of the present invention is not impaired.

  The weight average molecular weight of the water-insoluble polymer having a salt-forming group is preferably 10,000 to 300,000 from the viewpoint of enhancing the durability of the ink after printing. The weight average molecular weight can be measured by gel permeation chromatography using polystyrene as a standard substance and 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide-containing dimethylformamide as a solvent.

〔Neutralizer〕
A neutralizing agent can be used to neutralize the salt-forming group of the water-insoluble polymer having a salt-forming group.

  As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, and glyceric acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like.

  The amount of the neutralizing agent is not particularly limited, and is usually an amount such that the aqueous dispersion of the obtained pigment has a neutral to weak alkaline property, for example, a pH of 4.5 to 9.5, preferably 7 to 9.5. It is desirable to be. In addition, before mixing a pigment etc. and a neutralizing agent, you may neutralize the salt forming group of the water-insoluble polymer which has a salt forming group previously with the neutralizing agent.

  The solubility in water at 25 ° C. of the water-insoluble polymer having a salt-forming group after neutralization is preferably 15% by weight or less, more preferably 10% by weight or less, from the viewpoint of reducing the viscosity of the pigment dispersion. 5% by weight or less is further preferable, and 1% by weight or less is even more preferable.

  The amount of the water-insoluble polymer having a salt-forming group is preferably 10 to 100 parts by weight with respect to 100 parts by weight of the colorant from the viewpoint of dispersion stability and easy inclusion of the colorant in the polymer particles. Preferably it is 20-60 weight part.

(Organic solvent)
Examples of the organic solvent include alcohol solvents, ketone solvents such as methyl ethyl ketone, ether solvents, aromatic hydrocarbon solvents such as toluene and benzene, aliphatic hydrocarbon solvents such as heptane and hexane, and fats such as cyclohexane. Examples thereof include cyclic hydrocarbon solvents, halogenated aliphatic hydrocarbon solvents such as 1,1,1-trichloroethane, chloroform, carbon tetrachloride, and 1,2-dichloroethane. Among these, those having hydrophilicity are preferable, and methyl ethyl ketone is more preferable. The organic solvents can be used alone or in combination. The organic solvent used in the present invention preferably has a boiling point of 40 to 150 ° C. under atmospheric pressure (101.3 kPa), more preferably 60 to 130 ° C.

(Method for producing colorant aqueous dispersion)
The dispersion used in the present invention contains a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent, water, and preferably a neutralizing agent.

  The dispersion can be obtained by mixing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent, water and a neutralizing agent, and performing a dispersion treatment. From the viewpoint of dispersion stability of the dispersion, the dispersion is preferably obtained by dissolving or dispersing a water-insoluble polymer having a salt-forming group in an organic solvent together with a colorant, and adding water and, if necessary, a neutralizing agent. Can be obtained by dispersing the mixture.

  Examples of the emulsifier used for dispersion include a general ultrasonic emulsifier, an ultrahigh pressure homogenizer, and a membrane emulsifier. Examples of suitable emulsifiers include a microfluidizer (manufactured by Microfluidizer), a nanomizer (manufactured by Tokushu Kika Kogyo Co., Ltd.), an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.), and the like.

  The content of the colorant in the dispersion is preferably 1 to 30% by weight, more preferably 3 to 15% by weight, from the viewpoints of print density and ejection stability. The water content in the dispersion is preferably 35 to 75% by weight, more preferably 45 to 65% by weight, from the viewpoint of the stability of the particle size of the dispersion. The content of the organic solvent in the dispersion is preferably 10 to 25% by weight, more preferably 15 to 25% by weight, from the viewpoint of the stability of the particle size of the dispersion. Further, the content of the dispersing agent in the dispersion is preferably 0.2 to 15% by weight, more preferably 1 to 10% by weight.

  Similarly, the ratio of the organic solvent to water is preferably 150 to 750 parts by weight with respect to 100 parts by weight of the organic solvent from the viewpoint of the stability of the particle size of the dispersion.

Next, a dispersion containing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent, water, and preferably a neutralizing agent, is obtained using a batch evaporator using the formula (1):
30 ≦ (B / A) × 100 ≦ 100 (1)
(In the formula, A represents the total amount of solvent to be removed by evaporation (kg), and B represents the amount of solvent to be removed by evaporation in the region above the upper end of the heating unit attached to the batch evaporator).
In the range where the conditions represented by the above are satisfied, the organic solvent can be evaporated and removed by heating to produce a colorant aqueous dispersion for inkjet recording. Here, the amount of solvent to be removed by evaporation is the total amount of the organic solvent to be evaporated and water, and the total amount of solvent means the total amount of the solvent.

  The value of (B / A) × 100 is 30 to 100, preferably 40 to 100, more preferably 70 to 100, still more preferably 90 to 100, and particularly preferably 100 from the viewpoint of improving filter filterability. is there.

  The decrease in filter filterability may be due to the formation of aggregates by heating on the tank wall surface in the batch evaporator. In the stirred tank thin film evaporator, it is considered that the agglomerates are generated by heating on the wall of the tank even when the thin film is formed. Therefore, the production method of the present invention can be suitably applied to a production method using a stirring tank thin film evaporator.

  In the present invention, when evaporating and removing the organic solvent from the dispersion liquid, the liquid level of the dispersion liquid decreases, but in order to reduce the heating part accordingly, the jacket part which is the heating part is divided into multiple stages in parallel. It is preferable to keep it. The multi-stage is two or more stages, preferably 2 to 5 stages. Most preferably, the batch evaporator has a jacket part that can continuously adjust the heating part. Thereby, even when a large amount of the organic solvent is removed by evaporation, the formation of aggregates due to the dispersion being heated on the heating wall surface can be effectively suppressed.

  Here, the batch-type evaporator is a device in which a heating part such as a jacket (outer) part or a heat transfer heater that can pass or vent a heat medium such as hot water or steam is provided on the outer wall surface of the tank. An apparatus or the like in which a coil capable of passing or venting a heating medium such as hot water or steam is disposed inside the stirring tank, and is an evaporation apparatus capable of evaporating and removing the solvent by heating.

  The stirred tank batch type evaporator is an evaporator that is provided with a stirrer in the batch type evaporator and can evaporate and remove the solvent while stirring the inside of the tank.

  The stirred tank thin film evaporator means an evaporator that can form a thin film such as a solution using a heating wall surface in a stirred tank batch type evaporator, and can evaporate and remove the solvent from the thin film surface. Specific examples of the stirring tank thin film evaporator include a stirring tank thin film evaporator represented by Kansai Chemical Machinery Manufacturing Co., Ltd., trade name: wall wetter, and the like.

  Moreover, in this specification, evaporation removal means the concentration operation for evaporating and distilling an organic solvent and raising the density | concentration of a non-evaporation component. When removing the organic solvent, water may be removed by evaporation at the same time.

In this specification, the filter filterability is an index for evaluating whether or not coarse particles are present in the dispersion, and means the passing amount of the dispersion per unit area of a filter having a pore diameter of 5 μm. To do. The dispersion with a passage of 12 mL / cm ² or more when using a pigment and 1 mL / cm ² or more when using a dye contains almost no coarse particles such as agglomerates. This is preferable because the filterability is hardly lowered.

  There are no particular limitations on the evaporation conditions for evaporating and removing the organic solvent from the dispersion. However, the temperature of the wall surface of the heating unit of the batch evaporator is preferably 20 to 80 ° C, more preferably 40 to 60 ° C, from the viewpoint of suppressing thermal deterioration of the dispersion. Moreover, the pressure at the time of evaporating and removing the organic solvent from the dispersion is preferably 1 to 50 kPa, more preferably 5 to 20 kPa, from the viewpoint of reducing the load on the vacuum decompression device. When the organic solvent is removed from the dispersion under such conditions, the organic solvent can be efficiently removed.

  The concentration of the non-evaporated component in the dispersion before evaporating and removing the organic solvent is preferably 1 to 40% by weight, more preferably 10 to 30% by weight from the viewpoints of improving productivity and filter filterability. It is. Further, the concentration of the non-evaporable component in the dispersion after evaporating and removing the organic solvent is preferably 1 to 60% by weight, more preferably 5 to 40% by weight, and still more preferably 10 to 10% from the viewpoint of maintaining the performance of the ink. 30% by weight. The non-evaporating component is the total concentration of the colorant, dispersant, and neutralizer.

  As described above, a colorant aqueous dispersion is obtained by evaporating and removing the organic solvent from the dispersion so as to obtain a desired content of non-evaporated components by using a stirring type evaporator.

  Examples of the aqueous dispersion obtained in the present invention include an aqueous dispersion of water-insoluble polymer particles having a salt-forming group containing a colorant (hereinafter referred to as a containing aqueous dispersion), and a water-insoluble having a salt-forming group. Any of a water dispersion dispersed in water with a polymer (hereinafter referred to as a dispersion-type water dispersion) may be used. “Contained” here means that it may be included in the polymer particles or may be present on the surface of the polymer particles.

  Contained water dispersions generally produce coarser particles more easily than dispersed water dispersions. However, when the inclusion-type aqueous dispersion is used in the production method of the present invention, it is possible to effectively prevent the formation of coarse particles, so that it can be suitably used in the present invention.

  In this case, the average particle diameter of the water-insoluble polymer particles having a salt-forming group containing a colorant is preferably 0.01 to 1 μm, more preferably 0.02 to 0.5 μm, from the viewpoint of dispersion stability.

  The average particle size of the colorant used in the dispersion type dispersion is preferably 0.01 to 1 μm, more preferably 0.02 to 0.5 μm, from the viewpoint of dispersion stability.

  The colorant aqueous dispersion obtained in the present invention is made into an aqueous ink for ink jet recording by adding additives such as a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, and a chelating agent, if necessary. Can do. The water content in the water-based ink is preferably about 40 to 90% by weight.

Production Example 1 (Production of polymer a)
As monomers, 68 parts by weight of methyl methacrylate, 2 parts by weight of methacrylic acid, 10 parts by weight of silicone macromer [manufactured by Chisso Corporation, trade name: FM-0711], styrene macromer [manufactured by Toa Gosei Co., Ltd., trade name: AN- 6 (styrene-acrylonitrile copolymer macromer, styrene content: 70% by weight, weight average molecular weight: 6000, polymerizable functional group: methacryloyl group)] 5 parts by weight, 2-hydroxyethyl methacrylate 10 parts by weight and methoxypolyethylene glycol methacrylate [new Nakamura Chemical Co., Ltd., trade name: NK Ester M90G] 5 parts by weight, 30 parts by weight of methyl ethyl ketone as polymerization solvent and 3 parts by weight of polymerization chain transfer agent (2-mercaptoethanol) 17% by weight in a reaction vessel And nitrogen gas substitution was sufficiently performed to obtain a mixed solution.

  Meanwhile, in the dropping funnel, the remaining 83% by weight of each monomer is charged, and 16 parts by weight of methyl ethyl ketone and 0.8 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) are mixed and mixed. The mixture was replaced with nitrogen gas to obtain a mixed solution.

  Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. After 2 hours at 65 ° C from the end of the dropping, a solution in which 0.2 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) was dissolved in 4 parts by weight of methyl ethyl ketone was added, and then at 65 ° C for 2 hours, 70 ° C. After aging for 2 hours, 52 parts by weight of methyl ethyl ketone was added to adjust the concentration.

  A portion of the polymer solution a thus obtained was isolated by drying at 105 ° C. under reduced pressure for 2 hours and removing the solvent. When the weight average molecular weight was measured by gel permeation chromatography using dimethylformamide solution containing polystyrene as a standard substance and 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent, it was 10000. It was.

Example 1
60 g of oil-soluble dye [Orient Chemical Co., Ltd., trade name: Oil Black 860] was dissolved in 282 g of toluene, and 180 g of a methyl ethyl ketone solution (50% by weight) of polymer a obtained in Production Example 1 was mixed. To obtain a mixed solution.

  To the obtained mixed solution, 52 g of 1N sodium hydroxide aqueous solution and 1900 g of ion-exchanged water were added and mixed, and further, 25 ° C. using a high-pressure homogenizer [manufactured by Mimaru Machinery Co., Ltd., model number: H3-1C]. Then, dispersion treatment was performed for 1 hour under the condition of pressure 19.6 MPa to obtain a dispersion.

  750 g of the obtained dispersion (non-evaporable component concentration: 6.1% by weight) was heated in a heating tank (hot water) at a liquid temperature of 60 ° C. and a pressure of 13.3 kPa using a stirred tank batch evaporator (2 L container, inner diameter: 12.5 cm). ) Under heating conditions where the liquid level is lower than the liquid level (the value of (B / A) × 100 in the formula (1) is 100), until the content of non-evaporated components in the dispersion becomes 20% by weight. The solvent and a part of the water were removed by evaporation to obtain a colorant (dye) aqueous dispersion.

  More specifically, in the stirred tank batch-type evaporator (2L container, inner diameter: 12.5cm) shown in FIG. 1, the heating unit extends upward from the bottom of the device to 3.0cm (the heating unit in FIG. 1). A), the liquid level of the dispersion liquid is 5.5 cm above the upper end of the heating part A (liquid level position before evaporation), and heating is started at a heating temperature of 60 ° C. to evaporate the dispersion liquid. Evaporation was continued until the liquid level of the dispersion reached a position 1.0 cm 2 above the upper end of the heating part A (liquid level position after evaporation). As a result, 530 g of an organic solvent and a part of water were distilled off.

Comparative Example 1
By using the same dispersion as in Example 1 and adjusting the height of the hot water tank, the condition that the heating medium (warm water) is higher than the liquid level [the value of (B / A) × 100 in formula (1) is A colorant (dye) dispersion was obtained in the same manner as in Example 1 except for changing to 0).

  More specifically, in the stirred tank batch type evaporator (2L container, inner diameter: 12.5 cm) shown in FIG. 1, the heating section is in the range from the bottom of the apparatus up to 18.0 cm (the heating section in FIG. 1). B), at the position where the liquid level of the dispersion is 9.5 cm 2 below the upper end of the heating part B (the liquid level before evaporation), heating is started at a heating temperature of 60 ° C. to evaporate the dispersion. Evaporation was continued until the liquid level of the dispersion reached a position of 14.1 cm below the upper end of the heating part B (liquid level position after evaporation). As a result, 530 g of an organic solvent and a part of water were distilled off.

Production Example 2 (Production of polymer b)
In a reaction vessel, 20 parts by weight of methyl ethyl ketone and 0.03 part by weight of a polymerization chain transfer agent (2-mercaptoethanol) were added, and as a monomer, styrene macromer [manufactured by Toagosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group] 10 parts by weight, polyethylene glycol monomethacrylate [addition of 9 moles of ethylene oxide, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G], 10 parts by weight, polypropylene glycol mono 10 parts by weight of each of methacrylate (Aldrich Japan Co., Ltd., number average molecular weight: 375) 10 parts by weight, 12 parts by weight of methacrylic acid and 58 parts by weight of styrene monomer were mixed and thoroughly replaced with nitrogen gas. A mixed solution was obtained.

  On the other hand, the remaining 90% by weight of each monomer was charged into a dropping funnel and 0.27 parts by weight of a polymerization chain transfer agent (2-mercaptoethanol), 60 parts by weight of methyl ethyl ketone and 2,2′-azobis (2,4- Dimethylvaleronitrile) 1.2 parts by weight was added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.

  Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. After 2 hours at 65 ° C from the end of the dropwise addition, a solution of 0.3 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) in 5 parts by weight of methyl ethyl ketone was added, and further at 65 ° C for 2 hours, 70 ° C. After aging, the concentration was adjusted by adding 135 parts by weight of methyl ethyl ketone to obtain a polymer solution b having a resin solid content of 32% by weight.

  A portion of the resulting polymer solution b was isolated by drying at 105 ° C. under reduced pressure for 2 hours and removing the solvent. A weight average molecular weight of 74,000 was measured by gel permeation chromatography using polystyrene as a standard substance and 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide-containing dimethylformamide as a solvent.

Production Example 3 (Production of quinacridone pigment)
Quinacridone pigment (Dainippon Ink Industries Co., Ltd., CI Pigment Red 122) 300 parts by weight, sodium chloride 3000 parts by weight and diethylene glycol (Wako Pure Chemical Industries, Ltd.) 200 parts by weight in a stainless steel 5L volume It was put into a kneader and kneaded at 80 ° C. for 5 hours.

  The obtained kneaded product was taken out, poured into 3.0 L of warm water, stirred for about 1 hour, and then subjected to a washing operation of filtering. Thereafter, the washing operation was performed five times in the same manner as described above to remove sodium chloride and diethylene glycol, thereby obtaining a pigment-containing hydrate having a pigment content of 50% by weight. This pigment hydrate was dried with a vacuum dryer, and the desired quinacridone pigment was obtained. The average primary particle size of the obtained quinacridone pigment was about 70 nm.

Example 2
To the polymer solution b 6.4 kg obtained in Production Example 2, 0.46 kg of 5N sodium hydroxide aqueous solution, 0.092 kg of 25% ammonia aqueous solution, 1.4 kg of methyl ethyl ketone and 17.1 kg of ion-exchanged water are added, and the mixture is placed in a disper tank for 20 minutes. Mixed.

  Next, 6.08 kg of the quinacridone pigment was added thereto and mixed in the same manner for 6 hours. Add 5.7 kg of deionized water to 31.6 kg of the resulting dispersion, dilute it so that the concentration of non-evaporated components is 22% by weight, and use a high-pressure disperser [Microfluidizer (manufactured by Microfluidics)] to 200 MPa. 9-pass dispersion treatment at a pressure of

  16.0 kg of ion-exchanged water was added to 35.0 kg of the dispersion obtained after the dispersion treatment, and diluted so that the content of non-evaporated components was 15% by weight.

  Next, as shown in FIG. 2, the stirring jacket thin-film evaporator (45L container, inner diameter: 31.0 cm) is arranged in the heating jacket section X, the heating section Y and the heating section Z as shown in FIG. 15.0 kg of the dispersion is placed inside, under the conditions of a heating mode (heating water passes only in the area of the heating part X) in which the liquid temperature is 60 ° C, the pressure is 13.3 kPa, and the heating medium (warm water) is below the liquid level. [In the formula (1), A is 5.9 kg, B is 5.8 kg], and the organic solvent and a part of the water are removed by evaporation until the content of the non-evaporated component in the dispersion is 25% by weight. Pigment) aqueous dispersion was obtained.

Examples 3-7 and Comparative Examples 2-3
In Example 2, a colorant water dispersion was obtained in the same manner as in Example 2 except that the conditions were changed to those shown in Table 1.

The content of the non-evaporable component in the aqueous dispersion was examined by the following method.
[Content of non-evaporable components]
Non-evaporable component concentration Non-evaporable component concentration measuring instrument (made by Kett, product name: INFRARED MOISTURE DETERMINATION BALANCE FD-23) The evaporation component concentration was measured.

  Next, as a physical property of the colorant aqueous dispersion obtained in each Example and each Comparative Example, filter filterability was examined according to the following method. The results are shown in Table 1.

[Filter filterability]
The pore size is 0.8 μm (dye water dispersion: Example 1 and Comparative Example 1) and 5 μm (pigment water dispersion: Example 2 to the tip of a needle-free syringe (manufactured by Terumo Corporation) having a filter filtration capacity of 25 mL. 5 and Comparative Examples 2 to 3) (Fuji Photo Film Co., Ltd., acetylcellulose membrane (circular flat membrane), outer diameter 2.5 cm) was attached, and the concentration of non-evaporated components was 20% by weight (dye 20 mL of a solution or dispersion adjusted to an aqueous dispersion: Example 1 and Comparative Example 1) or 25% by weight (pigment aqueous dispersion: Examples 2 to 5 and Comparative Examples 2 to 3) was added.

Only the pigment aqueous dispersion was centrifuged (3800 G · hr), and then 98% by weight of the supernatant was recovered. The operation of manually applying pressure to each solution put into this syringe and passing through the filter is repeated until the solution or dispersion does not pass through, and the total amount passed (pass per membrane area (5 cm ² ) of the filter having a pore size of 5 μm) Amount (mL / cm ² )].

  From the results shown in Table 1, in contrast to Example 1 and Comparative Example 1, Examples 2-7 and Comparative Examples 2-3, all the colorant aqueous dispersions obtained in each Example were It can be seen that the filter filterability is remarkably excellent.

  The colorant aqueous dispersion obtained by the production method of the present invention can be suitably used for an aqueous ink for ink jet recording.

It is a schematic explanatory drawing of the stirring tank batch type evaporator used in Example 1 and Comparative Example 1. It is a schematic explanatory drawing of the stirring tank thin film type | formula evaporator used in Examples 2-7 and Comparative Examples 2-3.

Claims (3)

From a dispersion containing a colorant, a water-insoluble polymer having a salt-forming group, an organic solvent and water, using a batch evaporator, the formula (1):
30 ≦ (B / A) × 100 ≦ 100 (1)
(In the formula, A represents the total amount of solvent to be removed by evaporation (kg), and B represents the amount of solvent to be removed by evaporation in the region above the upper end of the heating part of the batch evaporator (kg)).
In the range which satisfy | fills the conditions represented by these, the manufacturing method of the coloring agent water dispersion for inkjet recording which evaporates and removes the said organic solvent by heating.   The process according to claim 1, wherein in formula (1), the value of (B / A) x 100 is 40 to 100.   The production method according to claim 1 or 2, wherein the batch evaporator is a stirred tank thin film evaporator.

Images