JP2019099819A - Manufacturing method of pigment water dispersion - Google Patents

Abstract

To provide a manufacturing method of a pigment water dispersion excellent in solvent resistance even when printing is conducted on a non-water-absorptive recording medium while maintaining low viscosity of water-based ink by using the water-based ink, and water-based ink for inkjet recording containing the pigment water dispersion obtained by the manufacturing method.SOLUTION: There is provided a manufacturing method of a pigment water dispersion having following processes 1 to 3, and water-based ink for inkjet recording containing the pigment water dispersion obtained by the manufacturing method. Process 1: a process for mixing polyester, an organic solvent, a pigment, and a basic compound to obtain a pigment mixture with a mass ratio of the pigment and the polyester [pigment/polyester] of 50/50 to 95/5. Process 2: a process for adding water while stirring the pigment mixture obtained in the process 1 to obtain a pigment dispersion. Process 3: a process for removing the organic solvent from the pigment dispersion obtained in the process 2.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a pigment water dispersion, and an aqueous ink for inkjet recording containing the pigment water dispersion obtained by the production method.

  The ink jet recording method is widely spread because it has many advantages such as being easy to realize full color and being inexpensive and being able to use plain paper as a recording medium. Among them, those using a pigment as a colorant are the mainstream from the viewpoint of weather resistance and water resistance of printed matter.

For example, in Patent Document 1, water is obtained by adding water to an organic solvent-based slurry of a pigment mixture as a method for producing an aqueous ink for inkjet recording, which is excellent in ink dischargeability, image density of printed matter, and light resistance. There is disclosed a method of producing an aqueous ink for ink jet recording, wherein the organic solvent is removed from the dispersion.
In Patent Document 2, an aqueous ink for inkjet recording, which is excellent in ink dischargeability, fixability of an image on a recording medium, and glossiness of a printed matter, and an inkjet containing pigment particles and polyester resin particles as a method for producing the same. An aqueous recording ink, wherein the pigment particles contain a pigment and a polyester resin (A) in a mass ratio [pigment / polyester resin (A)] 55/45 to 90/10, and the pigment in the pigment particles The mass ratio [pigment / polyester resin (A + B)] to the total amount of the polyester resin (A) and the polyester resin (B) constituting the polyester resin particles in the pigment particle is 10/90 to 40/60, An aqueous ink for inkjet recording and a method for producing the same are disclosed.

JP, 2016-27078, A JP, 2015-28114, A

For example, in the field of food and medicine, there is a scene where alcohol is used for sterilization and sterilization. In addition to package design, product information such as textbooks, methods of use, shelf life, lot numbers, etc. are printed on resin films of containers used in these fields, and these printed materials are resistant to solvents such as alcohol, ie, Solvent resistance is required.
The techniques of Patent Documents 1 and 2 require further improvement of solvent resistance when printing is performed on a non-water absorbing recording medium. In addition, when the ink viscosity is high, it causes ejection failure and the like when printing with an ink jet printer, and therefore, it is required that the ink used for ink jet recording has a low viscosity.
The present invention provides a method for producing a pigment water dispersion, which is excellent in solvent resistance even when printing is performed on a non-water absorbing recording medium while maintaining the low viscosity of the water based ink by using the water based ink. An object of the present invention is to provide a water based ink for ink jet recording containing a pigment water dispersion obtained by the above production method.
In the present specification, “non-water-absorptive” is a concept including low water-absorptivity and non-water-absorptivity, and the amount of water absorption per surface area of the recording medium at a contact time of 100 ms between the recording medium and pure water is 0 g / m ² or more and 2.5 g / m ² or less. The water absorption is measured by the method described in the examples using an automatic scanning liquid absorption meter. The following is also the same as the water absorption amount.
The “water-based ink” means an ink in which water is the largest proportion in the medium contained in the ink.

That is, the present invention provides the following [1] and [2].
[1] A method for producing a pigment water dispersion, which comprises the following steps 1 to 3.
Step 1: Step of mixing polyester, organic solvent, pigment and basic compound to obtain a pigment mixture having a mass ratio of pigment to polyester [pigment / polyester] of 50/50 to 95/5 Step 2: Step 1 Adding the water while stirring the pigment mixture obtained in Step b to obtain a pigment dispersion Step 3: Step of removing the organic solvent from the pigment dispersion obtained in step 2 [2] described in the above [1] An aqueous ink for ink jet recording, comprising a pigment water dispersion obtained by the method of

  According to the present invention, by using for a water-based ink, production of a pigment water dispersion having excellent solvent resistance even when printing is performed on a non-water-absorbent recording medium while maintaining the low viscosity of the water-based ink It is possible to provide a method and an aqueous ink for ink jet recording containing the pigment water dispersion obtained by the production method.

[Method of producing pigment water dispersion]
The method for producing the pigment water dispersion of the present invention (hereinafter, also simply referred to as "water dispersion") has the following steps 1 to 3.
Step 1: Step of mixing polyester, organic solvent, pigment and basic compound to obtain a pigment mixture having a mass ratio of pigment to polyester [pigment / polyester] of 50/50 to 95/5 Step 2: Step 1 Adding the water while stirring the pigment mixture obtained in step b to obtain a pigment dispersion step 3: removing the organic solvent from the pigment dispersion obtained in step 2

According to the present invention, by using the obtained pigment water dispersion in a water-based ink, the solvent resistance is improved even when printing is performed on a non-water-absorbent recording medium while maintaining the low viscosity of the water-based ink. It can be done. The reason is not necessarily clear, but is considered as follows.
Unlike a paper medium, a non-water-absorbent recording medium such as a PET film is smooth, so pigment particles contained in an aqueous ink discharged to the non-water-absorbent recording medium remain on the surface of the non-water-absorbent recording medium. Therefore, when the printed matter is rubbed with a non-woven fabric impregnated with an alcohol solvent such as ethanol, the printed surface may disappear. This is considered to be because pigment particles which are not included in the polyester or pigment particles which are not sufficiently adsorbed by the polyester on the surface of the non-water absorbing recording medium are easily removed.
On the other hand, according to the present invention, after mixing a polyester, an organic solvent, a pigment and a basic compound to obtain a pigment mixture having a mass ratio of pigment to polyester [pigment / polyester] within a specific range, the pigment mixture is stirred. While the addition of water reduces the solubility of the polyester and makes it easy for the polyester to adsorb uniformly to the pigment, as a result, the dispersion stability of the pigment by the polyester is improved, and the resulting pigment water dispersion is obtained. By using for a water-based ink, it is considered that the solvent resistance can be improved even when printing is performed on a non-water absorbing recording medium while maintaining the low viscosity of the ink.

<Polyester>
The polyester used in the present invention contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and is obtained by condensation polymerization of at least an alcohol component and a carboxylic acid component.

(Alcohol component)
It is preferable that the alcohol component which is a raw material monomer of polyester contains an aromatic containing diol from the viewpoint of pigment dispersibility and solvent resistance.
The aromatic-containing diol is preferably an alkylene oxide adduct of bisphenol A.
In the present invention, the alkylene oxide adduct of bisphenol A means the entire structure in which an oxyalkylene group is added to 2,2-bis (4-hydroxyphenyl) propane.
Specifically, the alkylene oxide adduct of bisphenol A is preferably a compound represented by the following general formula (I).

In the general formula (I), each of OR ¹ and R ² O is an oxyalkylene group, and each of them is preferably independently an oxyalkylene group having 1 to 4 carbon atoms, and more preferably an oxyethylene group or an oxypropylene group. It is a group.
x and y correspond to the average addition mole number of the alkylene oxide, and preferably each independently is preferably 1 or more, more preferably 2 or more, and preferably 16 or less, more preferably 7 or less, still more preferably 5 The following is more preferably 3 or less. Furthermore, from the viewpoint of reactivity with the carboxylic acid component, the average value of the sum of x and y is preferably 2 or more, and preferably 7 or less, more preferably 5 or less, still more preferably 3 or less. .
In addition, x pieces of OR ¹ and y pieces of R ² O may be identical to or different from each other, but are preferably identical from the viewpoint of solvent resistance. The alkylene oxide adducts of bisphenol A may be used alone or in combination of two or more. The alkylene oxide adduct of bisphenol A is preferably a propylene oxide adduct of bisphenol A and an ethylene oxide adduct of bisphenol A, and more preferably a propylene oxide adduct of bisphenol A.
The content of the alkylene oxide adduct of bisphenol A in the alcohol component which is a raw material monomer of polyester is preferably 50 mol% or more, more preferably 60 mol% or more, further preferably from the viewpoint of pigment dispersibility and solvent resistance. Is 70 mol% or more, and preferably 100 mol% or less.

The alcohol component of the polyester raw material monomer may contain another alcohol component other than the alkylene oxide adduct of bisphenol A.
Other alcohol components include ethylene glycol, propylene glycol (same as "1,2-propanediol"), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylenes thereof (having 2 or more carbon atoms) 4 or less) Oxide adducts (average added mole number 1 or more and 16 or less) etc. are mentioned.
The other alcohol components may be used alone or in combination of two or more.

(Carboxylic acid component)
As a raw material monomer of polyester, a carboxylic acid component is used other than the said alcohol component.
The carboxylic acid component includes a carboxylic acid, an anhydride of the carboxylic acid, and an alkyl (1 to 3 carbon atoms) ester of the carboxylic acid.
As the carboxylic acid component, aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and trivalent or higher polyvalent carboxylic acids are preferable, and in view of the reactivity of carboxylic acid components and alcohol components, and ink From the viewpoint of lowering the viscosity and solvent resistance, aromatic dicarboxylic acids and aliphatic dicarboxylic acids are more preferable.
As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid and terephthalic acid are preferable, and terephthalic acid is more preferable.
Aliphatic dicarboxylic acids include unsaturated aliphatic dicarboxylic acids and saturated aliphatic dicarboxylic acids, and from the viewpoint of the reactivity between the carboxylic acid component and the alcohol component, and from the viewpoint of lowering the viscosity of the ink and the solvent resistance, Unsaturated aliphatic dicarboxylic acids are preferred.
As the unsaturated aliphatic dicarboxylic acid, fumaric acid and maleic acid are more preferable, and fumaric acid is more preferable.
As the saturated aliphatic dicarboxylic acid, adipic acid and succinic acid (succinic acid may be substituted with an alkyl group and / or an alkenyl group) are preferable.
As the alicyclic dicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid and tetrahydrophthalic acid are preferable.
As the trivalent or higher polyvalent carboxylic acid, trimellitic acid and pyromellitic acid are preferable.
The carboxylic acid components may be used alone or in combination of two or more.

[Method of producing polyester]
The polyester is obtained by condensation polymerization of at least the alcohol component and the carboxylic acid component. Preferred embodiments and preferred contents of the alcohol component and the carboxylic acid component are as described above.
The polyester is produced, for example, by condensation polymerization of the alcohol component and the carboxylic acid component in an inert gas atmosphere at a temperature of 180 ° C. or more and 250 ° C. or less, using an esterification catalyst as necessary. be able to.
Examples of the esterification catalyst include tin catalysts, titanium catalysts, metal compounds such as antimony trioxide, zinc acetate and germanium dioxide, and the like. Among them, a tin catalyst is preferred from the viewpoint of the reaction efficiency of the esterification reaction in the production of polyester. As a tin catalyst, dibutyltin oxide, tin (II) (diethyl (2-ethylhexanoate)), salts thereof or the like are preferable, and tin ((II) ethyl hexanoate) is more preferable.
If necessary, in addition to the above esterification catalyst, an esterification cocatalyst such as 3,4,5-trihydroxybenzoic acid (same as "gallic acid") may be used.
In addition, radical polymerization inhibitors such as 4-tert-butylcatechol and hydroquinone may be used in combination.

The softening point of the polyester is preferably 80 ° C. or higher, more preferably 85 ° C. or higher, still more preferably 90 ° C. or higher, and preferably 170 ° C. or lower, from the viewpoint of lowering the viscosity of the ink and solvent resistance. Preferably it is 145 degrees C or less, More preferably, it is 125 degrees C or less.
The glass transition temperature (Tg) of the polyester is preferably 50 ° C. or more, more preferably 55 ° C. or more, and preferably 95 ° C. or less, more preferably 90, from the viewpoint of lowering the viscosity of the ink and solvent resistance. C. or less, more preferably 85 ° C. or less, still more preferably 80 ° C. or less.
The acid value of the polyester is preferably 5 mg KOH / g or more, more preferably 15 mg KOH / g or more, still more preferably 20 mg KOH / g or more from the viewpoint of adhesion to non-water absorbing recording media, and solvent resistance From the viewpoint, it is preferably 50 mg KOH / g or less, more preferably 40 mg KOH / g or less, and still more preferably 35 mg KOH / g or less.
The weight average molecular weight (Mw) of the polyester is preferably 5,000 or more, more preferably 7,500 or more, still more preferably 10,000 or more, still more preferably 12,500 or more from the viewpoint of solvent resistance. And from the viewpoint of dispersion stability of the pigment water dispersion, preferably 100,000 or less, more preferably 75,000 or less, still more preferably 50,000 or less, still more preferably 30,000 or less. .
The softening point, glass transition temperature, acid value, and weight average molecular weight (Mw) of the polyester can be measured by the methods described in the examples, and the types of monomers used, the compounding ratio, the temperature of condensation polymerization, the reaction A desired thing can be obtained by adjusting time suitably.

<Organic solvent>
The organic solvent is preferably an organic solvent capable of dissolving the polyester from the viewpoint of improving the adsorption rate of the polyester onto the pigment, and reducing the solubility of the polyester by the addition of water to precipitate the polyester.
Examples of the organic solvent include alcohol solvents such as ethanol; ketone solvents such as methyl ethyl ketone; ether solvents; aromatic hydrocarbon solvents; aliphatic hydrocarbon solvents; halogenated aliphatic hydrocarbon solvents and the like Be
Among these organic solvents, an alcohol solvent having 1 to 3 carbon atoms, a ketone having 4 to 8 carbon atoms, and a ketone having 1 to 3 carbon atoms from the viewpoint of polyester solubility, and safety and operability of solvent removal in post-treatment A system solvent is preferable, and ethanol and methyl ethyl ketone are more preferable. The said organic solvent can be used individually or in mixture of 2 or more types.

<Pigment>
The pigment used in the present invention is not particularly limited, and may be an organic pigment, an inorganic pigment, or a mixture thereof.
Organic pigments include anthraquinone pigments, quinacridone pigments, indigo pigments, dioxazine pigments, perylene pigments, perinone pigments, isoindolinone pigments, isoindoline pigments, phthalocyanine pigments, quinophthalone pigments, diketopyrrolo pigments. Examples thereof include condensed polycyclic pigments such as pyrrole pigments; and azo pigments such as disazo pigments and condensed azo pigments.
Organic pigments include pigment derivatives. The pigment derivative can be prepared by subjecting a functional group such as a hydroxyl group, a carboxy group, a carbamoyl group, a sulfo group, a sulfonamide group or a phthalimido methyl group to a surface of an organic pigment.
Inorganic pigments include metal oxides such as carbon black, alumina and titanium dioxide. These inorganic pigments may be treated with known hydrophobicizing agents such as titanium coupling agents, silane coupling agents, and higher fatty acid metal salts.
The hue is not particularly limited, and achromatic pigments such as white, black and gray; and chromatic pigments such as yellow, magenta, cyan, blue, red, orange and green may be used.
In addition, these pigments can be used individually or in mixture of 2 or more types.

<Basic compound>
Basic compounds are used to neutralize the anionic groups of the polyester. It is believed that the base-neutralized anionic group in the polyester dissociates in the pigment mixture and contributes to the dispersion stability of the pigment water dispersion and the ink by electrostatic repulsion between the anions.
Examples of the basic compound include metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonia; various amines and the like, preferably sodium hydroxide, potassium hydroxide and ammonia.
The use equivalent (mol%) of the basic compound to the anionic group in the polyester is preferably 10 mol% or more, more preferably from the viewpoint of improving the dispersion stability of the polyester in the pigment water dispersion and the ink. It is 20 mol% or more, more preferably 30 mol% or more, and preferably 300 mol% or less, more preferably 200 mol% or less, still more preferably 150 mol% or less.
The use equivalent (mol%) of the basic compound can be determined by the following formula. The use equivalent of the basic compound is the same as the neutralization degree when it is 100 mol% or less, and the basic compound is an anionic polyester when the use equivalent of the basic compound exceeds 100 mol% in the following formula It means that it is in excess with respect to the group, and the degree of neutralization of the polyester at this time is regarded as 100 mol%.
Usage equivalent of the basic compound (mol%) = [{added mass of basic compound (g) / equivalent of basic compound} / [{acid value of polyester (mg KOH / g) × weight of polyester (g)} // (56 × 1,000)]] × 100

(Step 1)
Step 1 is a step of mixing a polyester, an organic solvent, a pigment and a basic compound to obtain a pigment mixture having a mass ratio of pigment to polyester [pigment / polyester] of 50/50 to 95/5.
The pigment mixture obtained in Step 1 is preferably a mixture in which polyester is dissolved in an organic solvent, from the viewpoint of improving the adsorption rate of the polyester on the pigment.
In the step 1, the order of mixing the polyester, the organic solvent, the pigment and the basic compound is not particularly limited. After kneading the polyester and the pigment beforehand, it may be mixed with an organic solvent and a basic compound.
In step 1, from the viewpoint of sufficiently dispersing the pigment and from the viewpoint of improving the adsorption rate of the polyester onto the pigment, first, the polyester is dissolved in an organic solvent, and the polyester is dissolved in the organic solvent (hereinafter It is preferable to prepare a pigment mixture by preparing an organic solvent solution of polyester), adding a pigment, a basic compound, and, if necessary, a surfactant to the solution and mixing them. Although there is no restriction | limiting in the order which adds said each component to the organic-solvent solution of polyester, It is preferable to add in order of a basic compound and a pigment. The basic compound is preferably used as an aqueous solution, and the concentration of the basic compound aqueous solution is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 30 It is at most mass%, more preferably at most 20 mass%.

  The mass ratio [pigment / polyester] of pigment to polyester in the pigment mixture obtained in step 1 is 50/50 or more, preferably 55/45 or more, more preferably 58, from the viewpoint of lowering the viscosity of the ink. / 42 or more, and from the viewpoint of solvent resistance, 95/5 or less, preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80/20 or less.

The content of the polyester is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 40% by mass or less, in the pigment mixture obtained in Step 1. Preferably it is 30 mass% or less.
The content of the organic solvent is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, still more preferably 40% by mass or more in the pigment mixture obtained in Step 1. And, it is preferably 70% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less.
The content of the pigment in the pigment mixture obtained in Step 1 is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably Preferably it is 40 mass% or less.

Although there is no restriction | limiting in particular in the mixing method in the process 1, It is preferable to mix by rotating a stirring part using the stirring apparatus which has a stirring part. Examples of the stirring unit include a stirring blade including one or more stirring blades on a shaft, a screw having a single shaft or two or more shafts, a stirring member including a magnetically rotatable metal, and the like.
In the step 1, from the viewpoint of sufficiently dispersing the pigment to improve the viscosity reduction and the solvent resistance of the ink, it is preferable to perform the dispersion treatment at the time of mixing. As an apparatus used for dispersion processing, mixing and stirring devices such as anchor wings and disper wings; kneaders such as roll mills and kneaders; high pressure homogenizers such as microfluidizer (trade name of Microfluidics); media such as paint shakers and bead mills An example is a type disperser. These apparatuses can also combine 2 or more types. Among them, from the viewpoint of sufficiently dispersing the pigment, a mixing and stirring apparatus is preferable, and a high-speed stirring mixer is more preferable.
Among the high speed stirring mixers, a vertical axis rotating mixer having a multistage chopper blade is preferable. As such commercial products, Homomixer (Primix Co., Ltd.), Homodisper (Primix Co., Ltd.), Milder (Pacific Kiko Co., Ltd.), Caviton (Eurotech Co., Ltd.), High Share Mixer (Primix Co., Ltd.), Claire Mix (M Technique Co., Ltd.), Magic Lab (Shinmaru Enterprises Co., Ltd.), Zero Mill (Shibata Tekko Co., Ltd.), Apex Parser Zero (Hiroshima Metal & Machinery Co., Ltd.), etc. . The high speed stirring mixer may be a batch type or a circulation type.

The stirring speed at the time of mixing in step 1 is preferably 0.5 m / sec or more, more preferably 1 m at the tip peripheral speed from the viewpoint of sufficiently dispersing the pigment and improving the viscosity reduction and solvent resistance of the ink. / Sec or more, more preferably 2 m / sec or more, still more preferably 5 m / sec or more, and from the viewpoint of suppressing the temperature rise due to stirring energy, preferably 55 m / sec or less, more preferably 40 m / sec or less More preferably, it is 30 m / sec or less, still more preferably 25 m / sec or less.
The tip circumferential speed in the present invention means the tip circumferential speed of the stirring portion, and, for example, when using a stirring blade as the stirring portion, the circumferential speed of the outer peripheral portion of the largest stirring blade (main stirring blade) in the stirring device Means

The temperature at the time of mixing in step 1 is preferably 0 ° C. or more, and preferably 40 ° C. or less, more preferably 25 ° C. or less, from the viewpoint of production stability and viscosity reduction of the pigment mixture.
The mixing time in step 1 depends on the stirring speed and temperature conditions, but is preferably 0.3 hours or more, more preferably 0.5 hours or more, and preferably 20 hours or less, more preferably 10 hours or less More preferably, it is 5 hours or less, still more preferably 3 hours or less.

(Step 2)
Step 2 is a step of adding water while stirring the pigment mixture obtained in step 1 to obtain a pigment dispersion. In step 2, water is added to the pigment mixture to reduce the solubility of the polyester and the polyester is adsorbed to the pigment.
The stirring of the process 2 can use the stirring apparatus which has a stirring part mentioned by the above-mentioned process 1. Among them, a high-speed stirring mixer is preferable from the viewpoint of improving the adsorption rate of polyester to a pigment. As the high-speed stirring mixer, the same as those mentioned in the above-mentioned step 1 can be mentioned.
The stirring speed at the time of water addition in step 2 is preferably 0.3 m as the tip peripheral speed from the viewpoint of improving the adsorption rate of polyester to the pigment and improving the solvent resistance and the viscosity reduction of the ink. / Sec or more, more preferably 0.5 m / sec or more, further preferably 1 m / sec or more, still more preferably 2 m / sec or more, still more preferably 5 m / sec or more, and the viewpoint of ease of production And from the viewpoint of suppressing a temperature rise due to stirring energy, preferably 55 m / sec or less, more preferably 45 m / sec or less, still more preferably 35 m / sec or less, still more preferably 30 m / sec or less, still more preferably 25 m / sec. sec or less.
Further, from the viewpoint of improving the rate of adsorption of the polyester to the pigment, water is preferably added between the tip of the stirring unit and the wall surface in the stirring device, and when using a stirring blade, It is more preferable to add from the tip to the wall in the stirring device. As a method of addition, a method of dropping from above the liquid surface is preferable.
The addition rate of water in step 2 is preferably 0.1 parts by mass / min or more, more preferably 100 parts by mass of polyester used in the pigment mixture of step 1, from the viewpoint of shortening production time and enhancing production efficiency. Is 0.3 mass part / min or more, more preferably 0.5 mass part / min or more, and from the viewpoint of improving the adsorption rate of polyester to the pigment and improving the solvent resistance, and the low viscosity of the ink From the viewpoint of chemical conversion, it is preferably at most 500 parts by mass / min, more preferably at most 300 parts by mass / min, still more preferably at most 100 parts by mass / min, still more preferably at most 50 parts by mass / min, still more preferably 20 It is not more than mass part / min, more preferably not more than 10 mass part / min.

The amount of water added in step 2 is preferably 100 parts by mass or more, more preferably 300 parts by mass or more, more preferably 100 parts by mass with respect to 100 parts by mass of the organic solvent used in the pigment mixture of step 1 Is 500 parts by mass or more, more preferably 700 parts by mass or more, and from the viewpoint of enhancing production efficiency, preferably 5,000 parts by mass or less, more preferably 4,000 parts by mass or less, still more preferably 3, It is not more than 000 parts by mass, more preferably not more than 2,000 parts by mass.
The amount of water added in step 2 is preferably 300 parts by mass or more, more preferably 500 parts by mass or more, still more preferably 100 parts by mass of polyester used in the pigment mixture of step 1 from the viewpoint of solvent resistance. The amount is 1,000 parts by mass or more, and preferably 10,000 parts by mass or less, more preferably 8,000 parts by mass or less, and still more preferably 5,000 parts by mass or less from the viewpoint of enhancing production efficiency.
The temperature at the time of water addition in step 2 is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, still more preferably 20 ° C. or higher, from the viewpoint of production stability and viscosity reduction of the pigment mixture. The temperature is 40 ° C. or less, more preferably 35 ° C. or less, still more preferably 33 ° C. or less.

(Step 3)
Step 3 is a step of removing the organic solvent from the pigment dispersion obtained in step 2.
An aqueous dispersion can be obtained by removing the organic solvent from the pigment dispersion obtained in step 2 by a known method in step 3. The organic solvent in the obtained aqueous dispersion is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. The amount of residual organic solvent in the aqueous dispersion is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.
Further, if necessary, the pigment dispersion obtained in Step 2 may be heated and stirred before distilling off the organic solvent.
Examples of the organic solvent removing apparatus include a batch single distillation apparatus, a vacuum distillation apparatus, a thin film distillation apparatus such as a flash evaporator, a rotary distillation apparatus, and a stirring evaporator.
The pressure at the time of removing the organic solvent can be appropriately selected according to the type of the organic solvent to be used, but is preferably 30 kPa or less, more preferably 20 kPa or less, still more preferably 15 kPa or less from the viewpoint of suppressing the rise in liquid temperature.
The temperature of the heat medium at the time of removing the organic solvent can be appropriately selected according to the type of the organic solvent to be used, but is preferably 20 ° C. or more, more preferably 25 ° C. or more, still more preferably 30 ° C. or more under reduced pressure Preferably it is 80 degrees C or less, More preferably, it is 70 degrees C or less, More preferably, it is 65 degrees C or less.
The removal of the organic solvent is carried out until the non-volatile component (solid content) concentration of the aqueous dispersion from which the organic solvent is removed is preferably 18% by mass or more, more preferably 20% by mass or more, still more preferably 22% by mass or more It is preferable to carry out until it becomes 60 mass% or less, more preferably 40 mass% or less, and still more preferably 35 mass% or less. The non-volatile component (solid content) concentration can be measured by the method described in the examples.
Furthermore, in order to remove coarse particles and the like, the aqueous dispersion from which the organic solvent has been removed is further centrifuged, and then the liquid layer portion is filtered with a filter or the like, and the aqueous dispersion passing through the filter or the like Is preferably obtained as a pigment water dispersion.

  The pigment water dispersion obtained by the production method of the present invention may be added and mixed with one or more selected from preservatives, fungicides and sterilants from the viewpoint of suppressing the decay of the water dispersion. preferable. The mixing method is, for example, mixing the pigment water dispersion and one or more selected from an antiseptic agent, an anti-mildew agent and a sterilizing agent while preferably stirring at 60 ° C. or more, more preferably 65 ° C. or more Methods are included.

In the pigment water dispersion obtained by the production method of the present invention, polyester resin particles A containing pigment (hereinafter also referred to as “pigment-containing resin particles A”) are dispersed in an aqueous medium containing water as a main medium It is
Here, the form of the pigment-containing resin particle A is not particularly limited as long as the particle is formed of at least the pigment and the polyester. For example, a particle form in which at least a part of the pigment is contained in polyester, a particle form in which the pigment is dispersed in polyester, a particle form in which a part of the pigment is exposed on the surface of pigment-containing resin particle A, etc. And mixtures of Among them, from the viewpoint of lowering the viscosity of the ink and the solvent resistance, it is preferable that the polyester is in the form of particles in which at least a part of the pigment is contained in the polyester. .
The adsorption ratio of polyester to the pigment in the pigment water dispersion obtained by the present invention is preferably 60% by mass or more, more preferably 63% by mass or more, still more preferably 65% by mass or more, from the viewpoint of solvent resistance. The content is preferably 67% by mass or more, more preferably 70% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less from the viewpoint of the dispersion stability of the pigment water dispersion.
The adsorption rate can be measured by the method described in the examples.
The average particle diameter of the pigment-containing resin particles A in the pigment water dispersion obtained by the present invention is preferably 50 nm or more, more preferably 70 nm or more, still more preferably 100 nm or more, still more preferably from the viewpoint of printing density. It is 150 nm or more, and preferably 400 nm or less, more preferably 350 nm or less, and still more preferably 300 nm or less from the viewpoint of lowering the viscosity of the ink and the solvent resistance.
The average particle size of the pigment-containing resin particles A can be measured by the method described in the examples.

[Water-based ink for inkjet recording]
The aqueous ink for inkjet recording of the present invention (hereinafter, also simply referred to as “aqueous ink” or “ink”) contains the pigment water dispersion.
The content of the pigment water dispersion is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more in terms of solid content in the water-based ink from the viewpoint of printing density. And, from the viewpoint of solvent resistance, it is preferably 25% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.
The mass ratio of the pigment to the polyester [pigment / polyester] is preferably 50/50 or more, more preferably 55/45 or more, and still more preferably 58/42 or more in the water-based ink from the viewpoint of lowering the viscosity of the ink. And from the viewpoint of solvent resistance, it is preferably 95/5 or less, more preferably 90/10 or less, still more preferably 85/15 or less, still more preferably 80/20 or less.

  The pigment-containing resin particles A in the water-based ink preferably do not cause swelling or shrinkage of the particles or aggregation between the particles, and the average particle diameter of the pigment-containing resin particles A in the water-based ink is the pigment aqueous dispersion It is preferable that it is the same as the average particle diameter in the inside. The preferred embodiment of the average particle diameter of the pigment-containing resin particles A in the water-based ink is the same as the preferred embodiment of the average particle diameter in the pigment water dispersion. The average particle diameter of the pigment-containing resin particles A in the water-based ink is also measured by the method described in the examples.

<Organic solvent B>
The aqueous ink of the present invention preferably contains an organic solvent B. When the ink contains the organic solvent B, the moisturizing property of the ink is enhanced, and the clogging of the nozzle is suppressed to obtain the effect of improving the ejection stability of the ink. Examples of the organic solvent B include polar solvents such as ethers, alcohols, esters, lactones, lactams, and amines from the viewpoint of use in water-based ink.
The organic solvent B is preferably one that is liquid at 25 ° C. environment. When an organic solvent B which is liquid at 25 ° C. is used, the organic solvent B is easily removed by evaporation after the ink is discharged onto the recording medium, and the image sticking obtained by drying the ink is suppressed. And solvent resistance can be improved.
The content of the organic solvent B is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably, with respect to the total amount of water and the organic solvent B from the viewpoint of the wettability of the ink to the recording medium. Is 30% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less from the viewpoint of storage stability of the water-based ink.

(Organic solvent b)
The organic solvent B preferably contains 90% by mass or more of an organic solvent b having a boiling point of 235 ° C. or less (hereinafter, also simply referred to as “organic solvent b”).
The boiling point of the organic solvent b is preferably 150 ° C. or more, more preferably 165 ° C. or more, still more preferably 180 ° C. or more, from the viewpoint of improving the moisture retention and ejection stability of the ink, and the solvent resistance viewpoint C. or less, preferably 225.degree. C. or less, more preferably 215.degree. C. or less, still more preferably 205.degree. C. or less.
The organic solvent b may be used alone or in combination of two or more. When two or more organic solvents are used, the boiling point of the organic solvent b is weighted by the content (mass%) of each organic solvent It is a weighted average value.

Examples of the organic solvent b include polar solvents such as ethers, alcohols, esters, lactones, lactams and amines from the viewpoint of use in water-based inks, and preferred are ethers and alcohols. Among them, the organic solvent b is preferably at least one selected from diols and glycol ethers.
The diol is preferably an aliphatic diol having 2 to 6 carbon atoms having a hydroxy group bonded to a secondary carbon atom, more preferably a hydroxy group bonded to a secondary carbon atom, from the viewpoint of solvent resistance. It is a C3-C5 aliphatic diol which it has, More preferably, it is a C3-C4 aliphatic diol which has a hydroxyl group couple | bonded with the secondary carbon atom. Among the aliphatic diols, 1,2-alkanediol and 1,3-alkanediol are more preferable, and propylene glycol (1,2-propanediol, boiling point 187 ° C.), 1,2-butanediol (boiling point 190) C.) and 1,3-butanediol (boiling point: 207.degree. C.) is more preferably one or more selected from.
The glycol ether is preferably at least one selected from alkylene glycol monoalkyl ethers and dialkylene glycol monoalkyl ethers. For example, ethylene glycol monoethyl ether (boiling point 135 ° C.), ethylene glycol monobutyl ether (boiling point 171 ° C.), diethylene glycol monomethyl ether (boiling point 194 ° C.), diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether (boiling point 207 ° C.), diethylene glycol monobutyl ether (Boiling point 230 ° C.), diethylene glycol monoisobutyl ether (boiling point 220 ° C.). Among the glycol ethers, at least one selected from diethylene glycol monobutyl ether and diethylene glycol monoisobutyl ether is preferable, and more preferably diethylene glycol monoisobutyl ether, from the viewpoint of the wettability to the recording medium of the ink and solvent resistance. .

  The organic solvent B may be used in combination with the organic solvent b, but other organic solvents may be used in combination, but the content of the organic solvent b having a boiling point of 235 ° C. or less is preferably in the total organic solvent B contained in the ink. It is 90 mass% or more, more preferably 95 mass% or more, still more preferably 99 mass% or more, still more preferably 100 mass%. By containing 90% by mass or more of the organic solvent b having a boiling point of 235 ° C. or less, the solvent hardly remains between the image obtained by drying the ink and the recording medium, and the solvent resistance is improved.

<Water>
The water-based ink of the present invention contains water. As water contained in the ink, pure water such as ion exchange water and distilled water, and ultrapure water are preferable.
The content of water is preferably 40% by mass or more, more preferably 45% by mass or more, and still more preferably 50% by mass in the water-based ink from the viewpoint of reducing the amount of the organic solvent B used and improving the dischargeability of the ink. The content is preferably not less than 70% by mass, more preferably not more than 65% by mass, still more preferably not more than 60% by mass.

<Surfactant C>
The water-based ink of the present invention preferably contains a surfactant C as a surface tension regulator from the viewpoint of improving the ejection stability of the ink. The surfactant C may, for example, be a nonionic surfactant, an anionic surfactant, or a cationic surfactant, but a nonionic surfactant is preferable. Examples of the surfactant C include those used as surfactants of water-based inks, and those commercially available as surfactants can be used.
Nonionic surfactants include, for example, polyoxyalkylene alkyl ether surfactants, acetylene glycol surfactants, polyhydric alcohol surfactants, fatty acid alkanolamides, silicone surfactants, fluorosurfactants. Etc. Among them, one or more selected from polyoxyalkylene alkyl ether type surfactants, acetylene glycol type surfactants and silicone type surfactants are preferable, and acetylene glycol type surfactants are more preferable.
The content of the surfactant C in the aqueous ink is preferably 0.05% by mass or more, more preferably 0.30% by mass or more, still more preferably 0.50% by mass or more, and preferably 5. The content is 00% by mass or less, more preferably 1.50% by mass or less, and still more preferably 1.00% by mass or less.

The water-based ink of the present invention optionally contains, in addition to the above-mentioned components, pH adjusters such as amines, chelating agents such as ethylenediaminetetraacetic acid, and other optional components such as rust inhibitors and antioxidants. It is also good.
The viscosity at 25 ° C. of the aqueous ink of the present invention is preferably 1 mPa · s or more, more preferably 1.3 mPa · s or more from the viewpoint of containing a pigment, and preferably 1.8 mPa · s from the viewpoint of dischargeability. s or less, more preferably 1.7 mPa · s or less. The viscosity can be measured by the method described in the examples.

[Method of producing water-based ink for inkjet recording]
The water-based ink of the present invention is preferably produced by mixing the pigment water dispersion with the organic solvent B. The water-based ink of the present invention may further contain water and optional components described above, if necessary.
Furthermore, the water-based ink of the present invention can be obtained by a production method including the step of filtering the mixed liquid obtained by mixing these components with a filter or the like, as necessary.

[Ink jet recording method]
The water-based ink of the present invention can be used in an ink jet recording method of forming an image by the ink jet recording method. The inkjet recording method is not particularly limited as long as the aqueous ink of the present invention is used, but the effects of the present invention can be further enhanced by using the following method.
Examples of the recording medium used in the ink jet recording method include highly absorbent normal paper, non-water absorbent coated paper, resin film and the like. The aqueous ink of the present invention is preferably used in an ink jet recording method for recording on a non-water-absorbent recording medium, from the viewpoint of being excellent in solvent resistance even when printing is carried out on a non-water-absorbent recording medium.

Examples of the recording medium to be used include at least one resin film selected from polyester films such as polyethylene terephthalate, polyvinyl chloride films, polypropylene films, polyethylene films, and nylon films. These resin films may be subjected to surface treatment such as corona treatment as needed. The recording medium is preferably a polyester film from the viewpoint of solvent resistance.
As a resin film generally available, for example, Lumilar (registered trademark) T60 (made by Toray Industries, Ltd., polyethylene terephthalate, water absorption 2.3 g / m ² ), PVC 80 BP (made by Lintec Co., Ltd., polyvinyl chloride, water absorption Amount: 1.4 g / m ² ), Kainasu KEE70CA (made by Lintec Co., Ltd., polyethylene), Yupo SG90 PAT1 (made by Lintec Co., Ltd., polypropylene), Bonyal RX (made by Kojin Film & Chemicals Co., Ltd., nylon), etc. may be mentioned. .

The ink jet recording apparatus used for the ink jet recording method includes a thermal method and a piezo method. It is preferable to record the water-based ink on a recording medium using a piezo method ink jet recording device. The piezo method causes less heating and evaporation of the ink at the time of printing, and enables printing without impairing the performance of the water-based ink.
In the inkjet recording method, an image may be formed by the inkjet recording method using the aqueous ink after heating the recording medium. The heating temperature before image formation is preferably 40 ° C. or higher, more preferably 50 ° C. or higher from the viewpoint of solvent resistance, and preferably 100% from the viewpoint of suppressing denaturation of the recording medium and energy suppression. C. or less, more preferably 80 ° C. or less, still more preferably 60 ° C. or less.
Further, from the viewpoint of promoting the drying of the ink after the image formation, heating may be performed after the image formation. The heating temperature after image formation is preferably 40 ° C. or more, more preferably 50 ° C. or more from the viewpoint of solvent resistance, and preferably 100 from the viewpoint of suppressing the denaturation of the recording medium and the viewpoint of energy suppression. C. or less, more preferably 80 ° C. or less, still more preferably 60 ° C. or less.
The heating time after the image formation is preferably 10 seconds or more, more preferably 60 seconds or more, and still more preferably 120 seconds or more from the viewpoint of promoting the drying of the ink, and the viewpoint of suppressing the denaturation of the recording medium and From the viewpoint of energy suppression, it is preferably 300 seconds or less, more preferably 200 seconds or less.

  In the following production examples, examples and comparative examples, measurement and evaluation of various physical properties and characteristics were performed by the following methods.

[Softening point of polyester]
Using a flow tester “CFT-500D” (manufactured by Shimadzu Corporation), while heating a 1 g sample at a temperature elevation rate of 6 ° C./min, a load of 1.96 MPa is applied by a plunger, diameter 1 mm, length 1 mm Was pushed out of the nozzle. The plunger drop of the flow tester was plotted against temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

[Glass transition temperature of polyester]
The sample was heated to 200 ° C. using a differential scanning calorimeter (trade name: Pyris 6 DSC, manufactured by Perkin Elmer) and cooled from that temperature to 0 ° C. at a temperature decrease rate of 10 ° C./min. The temperature was raised by min, and the temperature at the intersection of the extension of the baseline below the maximum endothermic peak temperature and the tangent showing the maximum slope from the rising portion of the peak to the peak of the peak was taken as the glass transition temperature.

[Acid value of polyester]
The neutralization titration described in JIS K0070-1992 except that the measurement solvent is changed from a mixed solvent of ethanol and ether to a mixed solvent of acetone and toluene [acetone: toluene = 1: 1 (volume ratio)]. It measured according to the method.

[Weight average molecular weight of polyester (Mw)]
(1) Preparation of sample solution The resin was dissolved in chloroform so that the concentration was 0.5 g / 100 mL. Next, this solution was filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) with a pore size of 2 μm to remove insoluble components, and used as a sample solution.
(2) Molecular weight measurement As a solution, tetrahydrofuran was flowed at a flow rate of 1 mL / min, and the column was stabilized in a 40 ° C. thermostat. The measurement was performed by injecting 100 μL of the sample solution thereto. The weight average molecular weight of the sample was calculated based on a previously prepared calibration curve. The calibration curve includes several types of monodispersed polystyrene [monodispersed polystyrene manufactured by Tosoh Corp .; 2.63 × 10 ³ , 2.06 × 10 ⁴ , 1.02 × 10 ⁵ (weight average molecular weight (Mw)), GL Science Monodispersed polystyrene manufactured by Co., Ltd .; 2.10 × 10 ³ , 7.00 × 10 ³ , 5.04 × 10 ⁴ (weight average molecular weight (Mw))] was used as a standard sample.
Measuring device: "CO-8010" (made by Tosoh Corporation)
Analysis column: "GMHXL" + "G3000HXL" (made by Tosoh Corporation)

[Non-volatile content (solid content) concentration]
In a 30 ml polypropylene container (inner diameter 40 mm, height 30 mm), 10.0 g of sodium sulfate constant in a desiccator was weighed, and 1.0 g of a sample was added thereto and mixed to obtain a mixture. The mixture was then weighed, maintained at 105 ° C. for 2 hours to remove volatiles, and left in a desiccator for 15 minutes to measure the weight of the mixture after devolatilization. The mass obtained by subtracting the mass of sodium sulfate from the mass of the mixture after volatilization removal is divided by the mass of the sample before volatilization removal as the solid content of the sample after volatilization removal, and the non volatile matter (solid content) concentration (mass) %).

[Average Particle Size of Polyester-Based Resin Particles A Containing Pigment (Pigment-Containing Resin Particles A)]
The average particle size of the pigment-containing resin particles A was determined as the cumulant average particle size measured using a laser particle analysis system “ELS-8000” (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions were a temperature of 25 ° C., an angle of 90 ° between the incident light and the detector, and an integration count of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measured concentration was 5 × 10 ⁻³ mass%.

[Measurement of adsorption rate]
The adsorption rate of polyester to the pigment in the pigment water dispersion was determined by the following equation.
Adsorption rate (mass%) = mass of polyester resin adsorbed on pigment [g] / mass of polyester added in step 1 [g] × 100
The mass of polyester adsorbed to the pigment was determined by the following method.
First, 9 g of pigment water dispersion is placed in a centrifuge tube "11PA atstube" (manufactured by Hitachi Koki Co., Ltd.), and a centrifuge "himac CR22" (manufactured by Hitachi Koki Co., Ltd., set temperature 25.degree. C.) and rotor R21. (Manufactured by Hitachi Koki Co., Ltd.) was subjected to centrifugation for 180 minutes under conditions of centrifugal acceleration 39, 120 G at a rotation speed of 18,000 r / min. Next, the liquid phase portion after centrifugation is collected, and the mass of solid content contained in the liquid phase is regarded as the mass of unadsorbed polyester not adsorbed to the pigment, and the mass of the polyester added in step 1 is not adsorbed The mass obtained by subtracting the mass of the polyester was calculated as the mass of the polyester adsorbed on the pigment.

[Water absorption amount of recording medium at 100 ms contact time of recording medium and pure water]
Using an automatic scanning liquid absorption meter (manufactured by Kumagaya Riki Kogyo Co., Ltd., “KM 500 win”), measure the amount of transition of pure water at a contact time of 100 ms under the conditions of 23 ° C. and 50 mass% relative humidity, The amount of water absorption was 100 ms. The measurement conditions are shown below.
"Spiral Method"
Contact Time (sec): 0.010 to 1.0
Pitch (mm): 7
Length Per Sampling (degree): 86.29
Start Radius (mm): 20
End Radius (mm): 60
Min Contact Time (msec): 10
Max Contact Time (msec): 1,000
Sampling Pattern (1 to 50): 50
Number of Sampling Points (> 0): 19
"Square Head"
Slit Span (mm): 1
Slit Width (mm): 5

  The pigments, the organic solvent B and the surfactant C used in the following Production Examples, Examples and Comparative Examples are as follows.

[Pigment]
Yellow pigments: C.I. I. Pigment yellow 155 (hereinafter also referred to as “PY 155”) (INK JET YELLOW 4 GC, manufactured by CLARIANT)
Cyan pigment C.I. I. Pigment blue 15: 3 (hereinafter, also referred to as "PB 15: 3")
(CHROMOFINE BLUE, made by Dainichi Seika Kogyo Co., Ltd.)

[Organic solvent B]
・ IBDG: diethylene glycol monoisobutyl ether, boiling point 220 ° C. (manufactured by Wako Pure Chemical Industries, Ltd.)
PG: Propylene glycol, boiling point 187 ° C. (manufactured by Wako Pure Chemical Industries, Ltd.)

[Surfactant C]
・ Propylene glycol (50% by mass) solution of acetylene glycol surfactant (trade name “Serfynol (registered trademark) 104PG-50”, manufactured by Air Products, non-ionic surfactant)

(Production of polyester PA-1)
Production Example 1
Each raw material monomer (alcohol component and carboxylic acid component) and esterification catalyst shown in Table 1 are compounded in the amount shown in Table 1, and the internal volume is 10 L equipped with a thermometer, a stirring device, a downflow condenser and a nitrogen introducing pipe. In a four-necked flask, the reaction was carried out at 210 ° C. for 10 hours in a mantle heater in a nitrogen atmosphere, and then the reaction was continued until the temperature shown in Table 1 was reached at -8.3 kPa (G). Then, polyester PA-1 was obtained.
Table 1 shows the types and blending amounts of the alcohol component and the carboxylic acid component used as raw materials, and the physical properties and the like of the obtained polyester PA-1.

(Production of pigment water dispersion)
Example 1
(1) Process 1
In a container with an internal volume of 5 L, dissolve 100 g of polyester PA-1 in 295 g of methyl ethyl ketone (MEK), add 10.5 g of a 5 N aqueous solution of sodium hydroxide and 150 g of yellow pigment (PY 155) as a neutralizing agent in the container. Dispersion was carried out at a temperature of 25 ° C. for 1 hour at a tip peripheral speed of 9.4 m / sec using a homodisper wing “TK Robomix” (manufactured by Primix, Inc.) to obtain a pigment mixture 1. The mass ratio [pigment / polyester] of pigment to polyester at this time was 60/40.
(2) Process 2
Pigment mixture 1 obtained in step 1 at a stirring temperature at a tip circumferential speed of 9.4 m / sec using a homodisper wing "TK. ROVO MIX" (manufactured by PRIMIX CO., LTD.) At a container temperature of 25 ° C. While stirring, with respect to 100 parts by mass of polyester used in the pigment mixture of step 1, 147 g of ion exchange water was added at a speed of 15.6 parts by mass / min, near the tip of the homodisper wing. At this time, since the appearance of the solution changed from transparent to white, it was judged that the polyester which had been dissolved was deposited. Next, the remaining 2,803 g of ion-exchanged water is added in the same manner as described above such that the addition amount of ion-exchanged water is 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of Step 1. And pigment dispersion 1 were obtained.
(3) Process 3
In a warm bath adjusted to 60 ° C. at a rotational speed of 50 r / min using the rotary dispersion device “rotary evaporator N-1000S” (manufactured by Tokyo Rika Kikai Co., Ltd.) and the pigment dispersion 1 obtained in step 2 The organic solvent was removed by holding at a pressure of 15 KPa for 3 hours. The solution was further concentrated to a solid concentration of 24.0% by mass to obtain a concentrate.
The concentrate obtained is put into a 500 ml angle rotor and centrifuged at 3,660 r / min for 20 minutes using a high speed cooling centrifuge "himac CR22G" (made by Hitachi Koki Co., Ltd., set temperature 20 ° C.) The liquid layer portion was filtered with a membrane filter “Minisart” (manufactured by Sartorius) with a pore diameter of 5 μm to obtain an aqueous dispersion of pigment-containing resin particles A-1.
62.4 g of ion-exchanged water is added to 695 g of the aqueous dispersion of the pigment-containing resin particle A-1, and further, "Proxel (registered trademark) LV (S)" (manufactured by Lonza Japan Co., Ltd .: preservative, active 20 mass) %) 0.76 g was added and stirred at 70 ° C. for 2 hours. After cooling to 25 ° C., the solution is filtered with the pore size 5 μm filter, and ion-exchanged water is further added so that the solid content concentration becomes 22.0 mass%, pigment aqueous dispersion A containing pigment-containing resin particles A-1 I got.

Examples 2 and 3
Example 1 In the same manner as in Example 1 except that the addition rate of ion-exchanged water in step 2 was 30.7 parts by mass in Example 2 and 123.3 parts by mass in Example 3. A pigment water dispersion A-II containing pigment-containing resin particles A-2 and a pigment water dispersion A-III containing pigment-containing resin particles A-3 were obtained.

Examples 4 and 5
(1) Process 1
In a container with an internal volume of 5 L, dissolve 100 g of polyester PA-1 in 295 g of methyl ethyl ketone (MEK), add 10.5 g of a 5 N aqueous solution of sodium hydroxide and 150 g of yellow pigment (PY 155) as a neutralizing agent in the container. At a temperature of 25 ° C., using a homomixer “T.K. Robomix” (manufactured by Primix, Inc.), disperse at a tip peripheral speed of 20.0 m / sec, a clearance of 0.5 mm for 1 hour, Obtained. The mass ratio [pigment / polyester] of pigment to polyester at this time was 60/40.
(2) Process 2
The pigment mixtures 4 and 5 obtained in step 1 are each stirred at a tip inner peripheral speed of 9.4 m / sec using a homodisper wing "TK. ROVOMIX" (manufactured by PRIMIX CO., LTD.) At a container internal temperature of 25 ° C. With respect to 100 parts by mass of polyester used in the pigment mixture of step 1, while stirring at a speed, the speed of 1.9 parts by mass / min of ion exchange water in Example 4 and 370.4 parts by mass in Example 5 with ion exchange water And added 147 g. Next, the remaining 2,803 g of ion-exchanged water is added so that the addition amount of ion-exchanged water is 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of step 1, pigment dispersion 4 And 5 were obtained.
(3) Step 3 was carried out in the same manner as in Example 1 to obtain pigment water dispersion A-V containing pigment water dispersion A-IV containing pigment containing resin particles A-4 and pigment containing resin particles A-5 .

Examples 6, 7
(1) Process 1
In a container with an internal volume of 5 L, dissolve 100 g of polyester PA-1 in 295 g of methyl ethyl ketone (MEK), add 10.5 g of a 5 N aqueous solution of sodium hydroxide and 150 g of yellow pigment (PY 155) as a neutralizing agent in the container. Dispersion was carried out at a temperature of 25 ° C. for 1 hour at a tip peripheral speed of 20.0 m / sec using a homomixer “T.K. Robomix” (manufactured by Primix, Inc.) to obtain pigment mixtures 6 and 7, respectively. The mass ratio [pigment / polyester] of pigment to polyester at this time was 60/40.
(2) Process 2
The pigment mixture 6 and 7 obtained in step 1 was treated with a homomixer "T.K. Robomix" (manufactured by Primix, Inc.) at a temperature in the container of 25 ° C., and in Example 6, the tip circumferential velocity was 2.4 m. In Example 7, 15.6 parts by mass / min of ion exchanged water per 100 parts by mass of polyester used for the pigment mixture of Step 1 while stirring at a stirring speed of 20.0 m / sec at a tip peripheral speed of 2 / sec. Add 147g at speed. Next, add 2,803 g of the remaining ion-exchanged water so that the addition amount of ion-exchanged water is 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of step 1, and pigment dispersion 6 And 7 were obtained.
(3) Step 3 was carried out in the same manner as in Example 1 to obtain pigment water dispersion A-VI containing pigment-containing resin particles A-6 and pigment water dispersion A-VII containing pigment-containing resin particles A-7 .

Examples 8 and 9
(1) Process 1
Step 1 was carried out as in Example 1 to obtain pigment mixtures 8 and 9, respectively. The mass ratio [pigment / polyester] of pigment to polyester at this time was 60/40.
(2) Process 2
The pigment mixtures 8 and 9 obtained in Step 1 are respectively supplied to the in-line emulsifying and dispersing machine “Cavitron CD 1000” (Eurotec Co., Ltd.) from the bottom of the container, and in Example 8, 30.0 m / sec, In Example 9, 147 g of ion exchanged water was added at a rate of 15.6 parts by mass / min with respect to 100 parts by mass of polyester used in the pigment mixture of Step 1, while performing circulation operation at a stirring speed of 40.0 m / sec. Next, add 2,803 g of the remaining ion-exchanged water so that the addition amount of ion-exchanged water is 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of Step 1, and then pigment dispersion 8 And 9 were obtained.
(3) Process 3
Step 3 was performed in the same manner as in Example 1 to obtain a pigment water dispersion A-VIII containing pigment-containing resin particles A-8 and a pigment water dispersion A-IX containing pigment-containing resin particles A-9.

Example 10
(1) Process 1
Dissolve 100 g of polyester PA-1 in 295 g of methyl ethyl ketone (MEK) in a container with an inner volume of 5 L, and add 10.5 g of 5 N aqueous sodium hydroxide solution and 150 g of cyan pigment (PB 15: 3) as a neutralizing agent in it. Dispersion was conducted for 1 hour at a tip peripheral velocity of 22.0 m / sec using a homomixer "T.K. ROBOMIX" (manufactured by PRIMIX CO., LTD.) At a temperature in the container of 25 ° C. to obtain a pigment mixture 10. The mass ratio [pigment / polyester] of pigment to polyester at this time was 60/40.
(2) Process 2
The pigment mixture 10 obtained in Step 1 is stirred at a stirring speed of a tip peripheral speed of 22.0 m / sec using a homomixer "T.K. Robomix" (manufactured by Primix Corporation) at a container temperature of 25 ° C. While adding, 147 g of ion-exchanged water was added at a rate of 6.0 parts by mass / min to 100 parts by mass of polyester used for the pigment mixture of step 1. Next, add 2,803 g of the remaining ion-exchanged water so that the added amount of ion-exchanged water is 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of step 1, I got
(3) Step 3 was performed in the same manner as in Example 1 to obtain a pigment water dispersion A-X containing pigment-containing resin particles A-10.

Comparative Example 1
(1) Process 1
In a container with an inner volume of 5 L, dissolve 225 g of polyester PA-1 in 443 g of methyl ethyl ketone (MEK), add 23.7 g of 5 N sodium hydroxide aqueous solution as a neutralizing agent and 150 g of yellow pigment (PY 155) in the container. Dispersion was carried out at a temperature of 25 ° C. for 1 hour at a tip peripheral speed of 9.4 m / sec using a homodisper wing “TK Robomix” (manufactured by Primix Inc.) to obtain a pigment mixture C1. The mass ratio [pigment / polyester] of pigment to polyester at this time was 40/60.
(2) Process 2
The pigment mixture C1 obtained in step 1 is stirred at a temperature of 25 ° C. in a container at a stirring speed of a tip circumferential speed of 9.4 m / sec using a homodisper wing "TK. ROVOMIC" (manufactured by PRIMIX CO., LTD.) Then, with respect to 100 parts by mass of polyester used for the pigment mixture of step 1, 331 g of ion exchange water was added at a speed of 15.6 parts by mass / min. Next, the remaining 4,099 g of ion exchange water was added such that the addition amount of ion exchange water was 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of step 1.
(3) Step 3 was performed in the same manner as in Example 1 to obtain a pigment water dispersion AC-I containing pigment-containing resin particles AC-1.

Comparative example 2
(1) Process 1
Step 1 was performed in the same manner as Example 1.
(2) Process 2
With respect to 100 parts by mass of polyester used in the pigment mixture, 331 g of ion exchange water was added at a rate of 15.6 parts by mass / min without stirring the pigment mixture obtained in Step 1. Next, the remaining 4,099 g of ion exchange water was added such that the addition amount of ion exchange water was 1,000 parts by mass with respect to 100 parts by mass of MEK used in the pigment mixture of step 1.
Thereafter, the mixture was stirred at a stirring speed of a tip peripheral velocity of 9.4 m / sec using a homodisper wing "TK. ROVOMICX" (manufactured by PRIMIX CO., LTD.) At a temperature of 25 ° C. in the container. The parts were present unevenly. This was considered to be that the polyester was not well adsorbed to the pigment, so step 3 was discontinued.

(Production of water-based ink for inkjet recording)
A mixed solution is prepared in the amount shown in Table 2 below, and the obtained mixed solution is filtered with a membrane filter "Minisart" (manufactured by Sartorius) with a pore diameter of 1.2 μm to obtain aqueous inks 1-10 and C1. The The obtained water-based ink was evaluated by the following method. The results are shown in Table 2.

(Evaluation of water-based ink for inkjet recording)
[Solvent resistance (ethanol) resistance]
Polyethylene terephthalate film "Lumirror (registered trademark) T60 heated to 60 ° C. by filling the water-based ink obtained in each example and comparative example into an ink jet printer having a rubber heater mounted on" IPSIO SG 2010 L "manufactured by Ricoh Co., Ltd. A solid image was printed on # 75 "(Toray Industries, Inc .; water absorption amount: 2.3 g / m ² ). Next, the obtained printed matter was placed on a hot plate heated to 60 ° C. and dried for 3 minutes, to obtain a printed matter for evaluation in which the recording medium is polyethylene terephthalate.
100% by mass of ethanol is impregnated into a 2.0 cm × 2.0 cm non-woven cellulose fabric “BENCOT M-3II” (manufactured by Asahi Kasei Corporation), and the printed matter for evaluation is the bottom of the weight of the non-woven fabric Using a surface area of 78.5 cm ² ), a load of 22.5 g was applied, the printed surface was rubbed back and forth for 30 cycles, and the following five-step evaluation was performed visually. If it is 3 or more by the following evaluation criteria, it can use for practical use.
(Evaluation criteria)
5: There were no scratches on the surface of the printing surface, and no change was observed on the surface.
4: Although there was a scratch on the printing surface, there was no exposure of the recording medium surface.
3: The surface of the printing surface was peeled off to expose the surface of the recording medium, but the loss area of the printing portion was less than 50%.
2: The surface of the printing surface was peeled off to expose the surface of the recording medium, and the loss area of the printing portion was 50% or more and less than 100%.
1: The surface of the printing surface was peeled off to expose the surface of the recording medium, and the entire printing portion disappeared.

[Measurement of ink viscosity]
The viscosity of the water-based ink obtained in each Example and Comparative Example was measured using an E-type viscometer ("RE 80 type" manufactured by Toki Sangyo Co., Ltd.). The measurement conditions are a temperature of 25 ° C. and a rotational speed of 100 r / min. As the ink viscosity is lower, ejection failure and the like can be suppressed when printing with an ink jet printer.

Each notation in Table 2 is as follows.
* 1: Indicates the blending amount of each component relative to the total amount of water-based ink. The blending amount of propylene glycol includes the carry over from Surfynol 104PG-50.
* 2: The compounding quantity of Surfynol 104PG-50 shows an active ingredient.
* 3: Adsorption rate (%) in pigment water dispersion = mass of polyester adsorbed to pigment [g] / mass of polyester added in step 1 [g] × 100
* 4: Additive amount of water per unit minute to 100 parts by mass of polyester used in the pigment mixture of step 1 (parts by mass / min)
* 5: Addition amount of water (parts by mass) with respect to 100 parts by mass of the organic solvent used in the pigment mixture of step 1

From Table 2, the water-based inks 1 to 10 of Examples 1 to 10 are superior to the water-based ink C1 of Comparative Example 1 in solvent resistance even if the viscosity of the ink is low. This is considered to be because in Examples 1 to 10, the polyester is efficiently adsorbed to the pigment and the amount of polyester is not excessive.
Further, in the water-based inks 1 to 10 of Examples 1 to 10, since the addition of water in Step 2 is performed at the time of stirring, the polyester is sufficiently adsorbed to the pigment, and the solvent resistance is maintained while maintaining the low viscosity of the ink. Is considered to be improving.

  According to the method for producing a pigment water dispersion of the present invention, by using for a water-based ink, even when printing is carried out on a non-water-absorbent recording medium while maintaining the low viscosity of the water-based ink, An excellent pigment water dispersion can be obtained.

Claims (8)

The manufacturing method of a pigment water dispersion which has following processes 1-3.
Step 1: Step of mixing polyester, organic solvent, pigment and basic compound to obtain a pigment mixture having a mass ratio of pigment to polyester [pigment / polyester] of 50/50 to 95/5 Step 2: Step 1 Adding the water while stirring the pigment mixture obtained in step b to obtain a pigment dispersion step 3: removing the organic solvent from the pigment dispersion obtained in step 2   The method for producing a pigment water dispersion according to claim 1, wherein the pigment mixture is a mixture in which polyester is dissolved in an organic solvent.   Step 1 adds a pigment and a basic compound to a solution in which polyester is dissolved in an organic solvent and mixes them, and the mass ratio of pigment to polyester [pigment / polyester] is 50/50 or more and 95/5 or less The manufacturing method of the pigment water dispersion of Claim 1 or 2 which is a process of obtaining a certain pigment mixture.   The pigment water dispersion according to any one of claims 1 to 3, wherein the addition rate of water in step 2 is 0.1 parts by mass / min or more and 500 parts by mass / min or less with respect to 100 parts by mass of polyester. Production method.   The method for producing a pigment water dispersion according to any one of claims 1 to 4, wherein the amount of water added in step 2 is 100 parts by mass or more and 5,000 parts by mass or less with respect to 100 parts by mass of the organic solvent.   The method for producing a pigment water dispersion according to any one of claims 1 to 5, wherein dispersion treatment is carried out at the time of mixing in step 1.   The method for producing a pigment water dispersion according to any one of claims 1 to 6, wherein in the step 2, the pigment mixture is stirred at a stirring speed of 0.3 m / sec or more and 55 m / sec or less.   An aqueous ink for ink jet recording comprising a pigment water dispersion obtained by the method according to any one of claims 1 to 7.