JPH10273605A - Surface treated pigment, its production and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface-treated pigment that is excellent in dispersion stability in an aqueous dispersion and is useful as a water-based ink jet recording liquid by setting the ratio of a specific surface area of nitrogen gas to that of-carbon dioxide gas. SOLUTION: The objective pigment has a specific surface area of nitrogen gas (Sn) of 60-200 m<2> /g and its ratio to a specific surface area of carbon dioxide (Sc) is 0.7-3.0 (Sn/Sc). This pigment is prepared by dispersing (A) a pigment, particularly a phthalocyanine pigment together with (B) a dispersing agent, particularly a surfactant with an HLB of 11-40 in an aqueous medium to allow the component B to be adsorbed on the surface of the component A. In a preferred embodiment, the component A is subjected to a salt-milling treatment before the dispersion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated pigment having excellent dispersion stability in an aqueous medium, a method for producing the same, an aqueous pigment dispersion obtained by dispersing the same in an aqueous medium, and a colorant containing the same. It relates to an aqueous inkjet recording liquid.

[0002]

2. Description of the Related Art Conventionally, ink jet recording liquids have been disclosed in JP-A-53-61412 and JP-A-54-89.
As disclosed in JP-A-811 and JP-A-55-65269, those obtained by dissolving a water-soluble dye such as an acid dye, a direct dye or a basic dye in a glycol solvent and water are often used. . However, as water-soluble dyes, those having high solubility in water are generally used in order to obtain the stability of the recording liquid, so that the ink-jet recorded matter generally has poor water resistance and is easily damaged by water spill. There has been a problem that the dye of the recording portion is blurred.

In order to improve such poor water resistance,
As disclosed in JP-A-56-57862, attempts have been made to change the structure of a dye or to prepare a recording solution having a strong basicity. Also, Japanese Patent Laid-Open No. 50-490
No. 04, JP-A-57-36692, JP-A-57-36692.
As disclosed in Japanese Patent Application Laid-Open No. 9-20696 and Japanese Patent Application Laid-Open No. Sho 59-146889, improvement of water resistance has also been attempted by making good use of the reaction between recording paper and a recording liquid. Although these methods have a remarkable effect on specific recording paper, they lack versatility in that they are restricted by recording paper, and when using other than specific recording paper,
In many cases, sufficient water resistance of the recorded matter cannot be obtained.

As recording liquids having good water resistance, there are those in which an oil-soluble dye is dispersed or dissolved in a high boiling point solvent, and those in which an oil-soluble dye is dissolved in a volatile solvent. There is a problem of emission of water, which is environmentally unfriendly.
In addition, there are problems such as the necessity of solvent recovery or the like depending on the case where a large amount of recording is performed or the installation location of the apparatus. Therefore,
In order to improve the water resistance of the recorded matter, a pigment dispersion type recording liquid in which a pigment is dispersed in an aqueous medium has been developed.
However, in a pigment dispersion type recording liquid, although the colorant is changed from dye to pigment and the pigment is made finer to improve the water resistance of the recorded matter, there is a problem with the initial and temporal or ejection stability. Has occurred.

[0005] This is because, in the case of a dye-dissolved recording liquid, the dye is dissolved in the medium, whereas in the case of the pigment-dispersed recording liquid, the pigment is present as particles in the medium, and the pigment is coagulated. It is thought that this was due to sinking. In order to improve the dispersibility of the pigment, there is a method of improving the affinity between the pigment and the dispersant and preventing the pigment from aggregating and settling. However, since there is no index for evaluating the affinity between the pigment and the dispersant, various kinds of dispersants have to be examined for various pigments. In order to improve the dispersibility of the pigment, a method of treating the surface of the pigment is also known. However, there is no index for evaluating the relationship between the treatment method and the degree and the dispersibility. Therefore, much time was required to obtain a recording liquid having good dispersibility.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface-treated pigment having excellent dispersion stability in an aqueous medium and a method for producing the same, an aqueous pigment dispersion having excellent dispersion stability, and stability of initial, aging and ejection. An object of the present invention is to provide a pigment-dispersion type aqueous inkjet recording liquid having excellent properties.

[0007]

The present inventors have found that nitrogen gas is physically and uniformly adsorbed on the pigment surface, and carbon dioxide gas has a polar structure similar to that of water molecules. It has been found that the surface properties of the pigment can be quantified by the adsorption and the ratio thereof, and the index can be used as an index for evaluating the dispersion stability of the pigment in an aqueous medium. More specifically, the inventor has determined that the specific surface area (Sn) of nitrogen gas
Is not less than 60 m ² / g and not more than 200 m ² / g, and the ratio of the specific surface area (Sc) of carbon dioxide gas to the specific surface area (Sn) of nitrogen gas (Sc /
A surface-treated pigment having Sn) of 0.7 or more and 3.0 or less can be stably dispersed in an aqueous medium, and an aqueous inkjet recording liquid containing the surface-treated pigment as a colorant has excellent dispersion and ejection stability. And found the present invention.

That is, according to the present invention, the specific surface area (Sn) of nitrogen gas is not less than 60 m ² / g and not more than 200 m ² / g, and the specific surface area (Sc) of carbon dioxide gas and the specific surface area (Sn) of nitrogen gas are (Sc). / Sn) is 0.7 or more and 3.0 or less. In addition, the present invention is characterized in that the pigment is dispersed in an aqueous medium together with a dispersant, and the dispersant is adsorbed on the surface of the pigment, and the specific surface area of nitrogen gas (S
n) is not less than 60 m ² / g and not more than 200 m ² / g, and the ratio (S) of the specific surface area (Sc) of carbon dioxide gas to the specific surface area (Sn) of nitrogen gas is
c / Sn) is from 0.7 to 3.0. The present invention also relates to an aqueous pigment dispersion obtained by dispersing the surface-treated pigment in an aqueous medium. Further, the present invention relates to an aqueous inkjet recording liquid comprising the above-mentioned surface-treated pigment as a colorant.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The specific surface area of nitrogen gas and carbon dioxide gas is expressed by the following BE
The monolayer adsorption amount (Vm) of gas molecules is calculated by applying the isothermal adsorption equation of T, and the calculated monolayer adsorption amount (Vm) is calculated.
From the following specific surface area calculation formula. The calculation was performed under the assumption that the molecular occupied cross-sectional area of nitrogen gas was 0.162 nm ² and the molecular occupied cross-sectional area of carbon gas was 0.170 nm ² .

BET isothermal adsorption equation x / (V · (1-x)) = 1 / (Vm · C) + ((C−
1) / (Vm · C)) xx: relative pressure (= P / Po) P: partial pressure of gas Po:
Saturated vapor pressure V: Adsorption amount at relative pressure x Vm: Monolayer adsorption amount (standard state) C: Constant> 0

[0011] The specific surface area calculation formula S = s × Vm / Vo × K A S: specific surface area [m ² / g] s: Molecular occupied cross-sectional area [m ^2] Vm: monolayer adsorption amount [cm ³ (standard state ) / G] Vo: 22414 [cm ³ (standard condition)] K _A : Avogadro number

The method of calculating the monolayer adsorption amount (Vm) will be specifically described. The horizontal axis is x, and the vertical axis is x / (V · (1
−x)), the slope (C-1) /
(Vm · C), a straight line of intercept 1 / (Vm · C) is obtained,
From this, Vm and C can be determined. In particular, when x is in the range of 0.05 to 0.35, generally good linearity is obtained, so that Vm is obtained using this range. BET
The method includes a multipoint method and a one-point method, but a multipoint method is preferred.

Before measuring the gas volume under standard conditions,
As a pretreatment of the sample (pigment), heating vacuum is sufficiently performed to remove moisture and other contaminants. Usually 1 at 100 ° C
It is preferable to perform drying under reduced pressure for about 2 hours. In addition, in order to adjust the measurement temperature during measurement, liquid nitrogen is used for nitrogen gas,
For carbon dioxide, dry ice-ethanol is used.

The specific surface area (S) of the nitrogen gas of the surface-treated pigment
n) must be not less than 60 m ² / g and not more than 200 m ² / g. Pigments having a specific surface area (Sn) of nitrogen gas of more than 200 m ² / g tend to agglomerate, and an aqueous pigment dispersion obtained by dispersing the pigment in an aqueous medium has poor stability. On the other hand, S
A surface-treated pigment having an n of less than 60 m ² / g is difficult to perform a filtration operation at the time of producing an aqueous inkjet recording liquid, and causes sedimentation of the recording liquid over time. The Sn of the pigment is 60 m ²
If it is less than / g, it is preferable to carry out a salt milling treatment (a treatment of using an inorganic salt as a crushing aid and mechanically reducing the primary particle diameter of the pigment) before the surface treatment of the pigment.

In the salt milling treatment, a small amount of a water-soluble solvent is added as a lubricant to a mixture of a pigment and a water-soluble inorganic salt, and the mixture is kneaded mechanically and strongly with a kneader or the like to obtain fine particles. This treatment removes salts and water-soluble solvents. When mechanically kneading the pigment, the water-soluble inorganic salt and the water-soluble solvent, the weight ratio of the water-soluble inorganic salt to the pigment is preferably 2 to 20 times, more preferably 3 to 10 times. The weight ratio of the water-soluble solvent to the pigment is 0.5 to 3
Times, more preferably 0.7 to 2 times. Removal of the water-soluble inorganic salt and the water-soluble solvent is carried out by adding a kneaded product of the pigment, the water-soluble inorganic salt and the water-soluble solvent into water, stirring the mixture, forming a slurry, and repeating filtration and washing with water. Do it.

As the water-soluble inorganic salt, sodium chloride, potassium chloride and the like are used. Examples of the water-soluble solvent include 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether,
Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, diethylene glycol Propylene glycol monoethyl ether, liquid polypropylene glycol and the like are used.

Further, the ratio (Sc / S) of the specific surface area (Sc) of the carbon dioxide gas and the specific surface area (Sn) of the nitrogen gas of the surface-treated pigment.
n) must be greater than or equal to 0.7 and less than or equal to 3.0.
It is preferably from 9 to 2.0. A surface-treated pigment having an Sc / Sn of less than 0.7 has high hydrophobicity, and therefore has poor stability in an aqueous medium. On the other hand, a surface-treated pigment having a Sc / Sn of more than 3.0 has too high a water solubility, so that when the surface-treated pigment is used in an aqueous inkjet recording liquid, the water resistance of the recorded matter becomes poor.

The surface treatment of the pigment is preferably carried out by dispersing the pigment together with a dispersant in an aqueous medium and physically adsorbing the dispersant on the surface of the pigment. Specifically, a pigment, a dispersant, and an aqueous medium are put into a disperser such as a sand mill, a homogenizer, a ball mill, a paint shaker, or an ultrasonic disperser, and dispersed for several hours.
A concentrated aqueous pigment dispersion of about 0% by weight is prepared, and the dispersant is adsorbed on the pigment surface. When the pigment is surface-treated, the pigment derivative may be used in the range of 0.5% by weight to 10% by weight based on the pigment in order to promote the adsorption of the dispersant on the pigment surface.

The ratio of the pigment to the dispersant in the surface treatment of the pigment is 0.05 to 1 part by weight, more preferably 0.1 to 0.9 part by weight, based on 1 part by weight of the pigment. Is preferred. When the amount of the dispersant is less than 0.05 part by weight, the dispersant is not sufficiently adsorbed on the pigment surface, and when the amount is more than 1 part by weight, the dispersant is eluted when dispersed in an aqueous medium, and coloring of the ink jet recording liquid is performed. When used as an agent, the ejection stability may be reduced.

Examples of the pigment include insoluble azo pigments such as toluidine red, toluidine maroon, hansa yellow, benzidine yellow, and pyrazolone red;
Soluble azo pigments such as Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B; pigments derived from vat dyes such as alizarin, indanthrene, and thioindigo maroon; phthalocyanine-based pigments such as phthalocyanine blue and phthalocyanine green; quinacridone red and quinacridone Used are quinacridone pigments such as magenta, perylene pigments such as perylene red and perylene scarlet, isoindolinone pigments such as isoindolinone yellow and isoindolinone orange, quinophthalone pigments, dianthraquinonyl red, and carbon black. Can be

Of these, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, and carbon black are preferably used from the viewpoint of light resistance. In some cases, two or more different pigments may be used in combination.

When the pigment is represented by a color index (CI) number, CI pigment yellow 12, 13, 1
4,17,20,24,74,83,86 93,10
9,110,117,125,137,138,14
7,148,153,154,166,168, CI Pigment Orange 13,16,36,43,51,5
5,59,61, CI Pigment Red 9,48,4
9, 52, 53, 57, 97, 122, 123, 14
9,168,177,180,192,215,21
6,217,220,223,224,226,22
7,228,238,240, CI Pigment Violet 19,23,29,30,37,40,50, CI
Pigment Blue 15, 15: 1, 15: 4, 15:
6, 22, 60, 64, CI Pigment Green 7, 3
6, CI Pigment Brown 23, 25, 26, CI Pigment Black 7, and the like.

The dispersant used for the surface treatment of the pigment includes a surfactant and an aqueous resin. As the surfactant, HLB is 11 or more and 40 or less, furthermore, HL
An anionic surfactant or a nonionic surfactant in which B is 13 or more and 39 or less is suitably used. When a surfactant having an HLB of less than 9 is used, dispersibility of the obtained surface-treated pigment in an aqueous medium becomes difficult, and the dispersion stability decreases. Further, a surfactant having an HLB of more than 40 has high solubility in water, and the surfactant is eluted from the surface-treated pigment, so that the amount of adsorption decreases, and the stability of the aqueous pigment dispersion decreases. Further, when the amount of the surfactant is increased in order to increase the adsorption amount of the surfactant, foaming becomes severe when the aqueous inkjet recording liquid is produced, and the ejection stability is reduced.

Examples of the anionic surfactant include fatty acid salts, alkyl sulfate salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, and alkyl phosphorus. Acid salt, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester, etc. Can be exemplified.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitol fatty acid ester. Glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based, silicone-based nonionic activators. In some cases, two or more different surfactants may be used in combination.

The aqueous resin has an acid value of 110 or more and 26
A resin soluble in water of 0 or less is preferably used. When a resin having an acid value of less than 100 is used, it is difficult to disperse the obtained surface-treated pigment in an aqueous medium, and the dispersion stability is reduced. When a resin having an acid value of more than 260 is used, the resin adsorbed on the surface of the pigment may be eluted. Specific examples of the aqueous resin include acrylic, styrene-acrylic, polyester, polyamide, and polyurethane resins, with acrylic resins being preferred. Two or more different aqueous resins may be used in some cases.

As the aqueous medium, water and, if necessary, an aqueous solvent are used. As the water, ion-exchanged water from which metal ions and the like have been removed or distilled water is used. Aqueous solvents include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol,
Polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, ketone alcohol, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, 1,2-hexanediol, N-
Methyl-2-pyrrolidone, substituted pyrrolidone, 2,4,6
Hexanetriol, tetrafurfuryl alcohol,
4-methoxy-4-methylpentanone and the like can be exemplified.

It is preferable to adjust the pH of the concentrated aqueous pigment dispersion to a weak alkalinity of 6 to 10, particularly 7 to 9, in order to improve the dispersion stability. pH to desired p
In order to adjust the pH to H, a pH adjuster such as an amine, an inorganic salt or ammonia, or a buffer such as phosphoric acid can be used. In particular, volatile basic components are preferred. The measurement of the specific surface area of the nitrogen gas and the carbon dioxide gas of the surface-treated pigment is performed after producing the concentrated aqueous pigment dispersion, and then isolating and drying the surface-treated pigment by filtration, centrifugation or ultrafiltration.

Since the surface-treated pigment of the present invention has excellent dispersion stability in an aqueous medium, it is suitably used as a colorant for an aqueous inkjet recording liquid. Aqueous inkjet recording liquid, the surface-treated pigment of the present invention or an aqueous pigment dispersion obtained by dispersing the surface-treated pigment in an aqueous medium,
It can be produced by adding water and, if necessary, an aqueous solvent, an aqueous resin, additives and the like to form an ink. The amount of the pigment in the ink jet recording liquid is not particularly limited, but is generally 1 to 15% by weight, more preferably 1 to 15% by weight based on the total weight of the recording liquid.
A range of 10% by weight is preferred. Water is 40 to 9 of the recording liquid.
0% by weight is added. The aqueous solvent may be used alone or mixed to prevent drying of the recording liquid at the nozzle portion, solidification of the recording liquid, and stable ejection of the recording liquid and drying of the nozzle over time. It can be used in the range of 50% by weight.

For the purpose of speeding up the drying of the recording liquid on paper, alcohols such as methanol, ethanol and isopropyl alcohol can be used. When the recording liquid substrate is a permeable material such as paper,
A penetrant can be added to speed up the penetration of the recording liquid into the paper and the apparent dryness. As the penetrant, glycol ethers such as diethylene glycol monobutyl ether exemplified as aqueous solvents, alkylene glycol, polyethylene glycol monolauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, sodium dioctylsulfosuccinate and the like can be used. it can. They are,
A sufficient effect is obtained with the use amount of 5% by weight or less of the recording liquid.
And it becomes undesirable.

The aqueous inkjet recording liquid of the present invention preferably contains an aqueous resin in order to fix the surface-treated pigment to the substrate. The aqueous resin is contained in the aqueous inkjet recording liquid as a non-adsorbed resin not adsorbed on the pigment. As the aqueous resin for fixing, a resin which is dissolved or dispersed in water is used alone or in combination. Examples of the aqueous resin include acrylic, styrene-acrylic, polyester, polyamide, and polyurethane resins. The resin adsorbed on the pigment surface and the resin not adsorbed are preferably contained in the recording liquid in a range of 0.1 to 5% by weight, more preferably 0.2 to 2% by weight. If it is less than 0.1% by weight, the pigment cannot be sufficiently fixed, and if it is more than 5% by weight, the ejection stability of the recording liquid may be reduced.

When a water-soluble resin is used as the aqueous resin, the viscosity of the recording liquid tends to increase, but when a water-dispersible resin is used, the viscosity of the recording liquid must be kept low. And the water resistance of the recorded matter can be further improved. A neutralizing agent for aqueous resin such as ammonia, amine, inorganic alkali or the like can be appropriately adjusted and added to the aqueous inkjet recording liquid. In this case, too, the pH is adjusted to a desired pH within 6 to 10. Is preferred.

The recording liquid of the present invention may contain a fungicide in an amount of 0.05 to 1.0% by weight of the recording liquid in order to prevent the occurrence of mold. Examples of fungicides include sodium dihydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, zinc pyridinethione-1
-Oxide, 1,2-benzisothiazolin-3-one, amine salt of 1-benzisothiazolin-3-one and the like are used.

In order to prevent the deposition of metal at the nozzle portion and the deposition of insoluble matters in the recording liquid, a chelating agent is used in the range of 0.005 to 0.5% by weight of the recording liquid. Can be. The chelating agent blocks metal ions in the recording liquid, and specifically includes ethylenediaminetetraacetic acid, sodium salt of ethylenediaminetetraacetic acid, diammonium salt of ethylenediaminetetraacetic acid, and ethylenediaminetetraacetic acid. Acid ammonium tetraammonium salt.

Further, an antifoaming agent can be added in order to prevent the circulation and movement of the recording liquid or the generation of bubbles during the production of the recording liquid. Urea, dimethyl urea and the like can be added as other additives. The recording liquid of the present invention is preferably filtered with a filter having a pore size of 3 μm or less, preferably 1.0 μm or less, and more preferably 0.45 μm or less. Prior to the filtration, the particles having a large particle size can be removed by centrifugation, whereby clogging in the filtration can be reduced and the service life of the filter can be prolonged.

The recording liquid has a viscosity of 0.8 to 15 cps (at 25 ° C.) and a surface tension of 25, depending on the type of the recording apparatus.
The liquid is preferably adjusted to a liquid density of 50 to 50 dyne / cm, and the average particle size of the recording liquid is preferably 20 to 200 nm from the viewpoint of storage stability of the recording liquid.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
In Examples, "parts and%" means "parts by weight" and "% by weight". The treatments shown in Table 1 were applied to the pigments shown in Table 1 to obtain surface-treated pigments. Sn and Sc / S of the obtained surface-treated pigment
n was as shown in Table 1. A specific processing method and a method for measuring Sn and Sc / Sn are shown below.

[Micronization treatment] 250 parts of pigment, 2500 parts of sodium chloride and 200 parts of diethylene glycol were charged into a 1 gallon stainless steel kneader (manufactured by Inoue Seisakusho) and kneaded for 3 hours. Next, the mixture was poured into 2.5 liters of warm water, stirred for about 1 hour with a high-speed mixer while heating to about 80 ° C. to form a slurry, and then filtered and washed with water five times to repeat sodium chloride and water. Except for the solvent, a dried pigment product was obtained.

[Surface treatment] In a paint conditioner, 20 parts of a pigment and 5 parts of a dispersant shown in Table 1 (in terms of solid content) were used.
And water were added to make the total amount 100 parts and dispersed for 3 hours. The obtained aqueous pigment dispersion was centrifuged at 15000 rpm for 6 hours, and then dried, and the specific surface areas of nitrogen gas and carbon dioxide gas were measured.

[Method for measuring Sn and Sc / Sn] The measurement was performed using a high-speed specific surface area measuring apparatus “ASAP 2000” and “ASAP data processing software” manufactured by Micromeritics, USA. Nitrogen adsorption is about 77k using liquid nitrogen
It measured under. Carbon dioxide adsorption is dry ice
It was measured under alcohol at about 196k. The analysis is applied to the BET equation, where 0.000066 is used as the non-ideal gas correction constant, 0.0015468 is used as the nitrogen gas density conversion constant, and 0.00181589 is used as the carbon gas density conversion constant. The specific surface area was calculated using 9.5300 Å as the Kelvin constant of the quality.

[0041]

[Table 1]

A: Kao's anionic surfactant "Neoperex No. 6", HLB37 B: Kao's nonionic surfactant "Emulgen 91"
0 "), HLB10.8 C: Kao Corporation's nonionic surfactant" Emulgen 91 "
3)), HLB 15.5 D: Acrylic resin aqueous solution "Johncryl 611" (ammonia neutralized, solid content 20%) manufactured by Johnson Polymer, acid value 57 E: Acrylic resin aqueous solution "Johncryl 586 manufactured by Johnson Polymer" (Neutralized ammonia, solid content 20%), acid value 108 F: Acrylic resin aqueous solution "Johncryl 683" (ammonia neutralized, solid content 20%) manufactured by Johnson Polymer, 160 G: manufactured by Johnson Polymer Acrylic resin aqueous solution “Joncryl 690” (neutralized ammonia, solid content 20%), acid value 240

To 20 parts of the surface-treated pigment, 0.1 part of 30% aqueous ammonia and 79.9 parts of purified water were added, and the mixture was redispersed with a paint conditioner to prepare a concentrated recording liquid for inkjet. For the pigments not subjected to the surface treatment, 20 parts of the pigment was added to dispersant C (formulation 4) or dispersant G.
(Formulation 5) was added with 5 parts (solid content) and purified water to make a total amount of 100 parts, and the mixture was dispersed with a paint conditioner to prepare a concentrated recording liquid for inkjet. The concentrated recording solution was filtered with a 90 mmφ 1 μm membrane filter, and subsequently with a 90 mmφ 0.45 μm membrane filter. When the concentrate could not be filtered through a 1 μm membrane filter, no aqueous inkjet recording liquid was produced.

(Examples 1 to 10 and Comparative Examples 1 to 25) Using the concentrated recording solution obtained, the raw materials having the formulations shown in Table 3 were mixed, and the mixture was filtered through a 1-μm membrane filter. The mixture was filtered through a 45 μm membrane filter to produce an aqueous inkjet recording liquid. Table 2 shows details of the prescription (raw materials and the number of blending parts).

[0045]

[Table 2]

Resin 1: Acrylic resin emulsion "W-215" manufactured by Nippon Polymer Co., Ltd., solid content 30% Resin 2: Aqueous resin solution "Johncryl 61J" manufactured by Johnson Polymer Co., Ltd., solid content 30% Neutralizing agent: dimethylaminoethanol Moisturizer: Glycerin Penetrant: Anionic surfactant "Perex O" manufactured by Kao Corporation
TP ", solid content 70% Fungicide:" Proxel GXL "manufactured by Zeneca Chelating agent: Sodium salt of ethylenediaminetetraacetic acid Water: Purified water

The obtained aqueous ink jet recording liquid was evaluated for filterability, initial average particle diameter, viscosity, stability over time, and printing stability. Table 3 shows the results. The evaluation was performed as follows. [Filterability] 300 ml of an aqueous inkjet recording liquid was
Filtration was performed using a membrane filter having a pore size of 1 μm and 90 mmφ, and subsequently, filtration was performed using a membrane filter having a pore size of 0.45 μm and 90 mmφ. ○: Filtration of 1 μm and 0.45 μm was completed. Δ: Filtration was possible only in 1 μm ×: Filtering was not possible [Viscosity] Measured at 25 ° C. using a B-type viscometer. [Average particle size] It was measured with a laser diffraction type particle size distribution meter (“SALD-1100” manufactured by Shimadzu Corporation).

[Temperature stability] 30 cc of the recording liquid was put in a screw cap bottle, left at 70 ° C. for one month, and the average particle diameter of the recording liquid and the viscosity at 25 ° C. were measured and compared with those before leaving. ：: Little change in average particle size and little change in viscosity. Δ: The change in average particle size is large or the change in viscosity is large. X: The change in average particle size is large and the change in viscosity is large.

[Printing stability] The recording liquid was put into a cartridge of an ink jet printer (“Desktop 560” manufactured by HP), and printing was performed on plain paper (“K” manufactured by Xerox) at room temperature. The presence or absence of non-discharge was visually evaluated. In addition, the same evaluation was performed after standing for 1 hour after printing. ：: No non-discharge of the recording liquid, disturbance of printing, and chipping were not observed before and after standing. Δ: No non-discharge of recording liquid, disorder of printing, and chipping were not observed before standing, but non-discharge of recording liquid, disorder of printing,
Chipping is observed. ×: Non-discharge of the recording liquid at several places in the solid printing portion before leaving was observed. -: No evaluation was performed.

[0050]

[Table 3]

[0051]

According to the present invention, it is possible to provide a pigment-dispersion type aqueous inkjet recording liquid having good initial and temporal stability and discharge stability.

Claims (10)

[Claims] A specific surface area (Sn) of nitrogen gas is 60 m ² / g.
The ratio (Sc / Sn) of the specific surface area (Sc) of carbon dioxide gas to the specific surface area (Sn) of nitrogen gas is not more than 200 m ² / g.
A surface-treated pigment having a molecular weight of 7 or more and 3.0 or less. 2. The surface-treated pigment according to claim 1, wherein the surface treatment is adsorption of a dispersant. 3. The surface-treated pigment according to claim 2, wherein the dispersant is a surfactant having an HLB of 11 to 40. 4. The surface-treated pigment according to claim 2, wherein the dispersant is a resin having an acid value of 110 or more and 260 or less. 5. The pigment is at least one selected from phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments and carbon black.
The surface-treated pigment according to any one of claims 1 to 4, which is a kind of pigment. 6. A pigment is dispersed in an aqueous medium together with a dispersant,
The specific surface area (Sn) of nitrogen gas is 60 m ² / g or more and 200 m ² / g or less, and the specific surface area of carbon dioxide gas (Sc) and the specific surface area of nitrogen gas (Sn) are characterized by adsorbing a dispersant on the pigment surface. The method for producing a surface-treated pigment having a ratio (Sc / Sn) of 0.7 or more and 3.0 or less. 7. The method for producing a surface-treated pigment according to claim 6, wherein the pigment is subjected to a salt milling treatment before the pigment is dispersed in an aqueous medium together with a dispersant. 8. An aqueous pigment dispersion comprising the surface-treated pigment according to any one of claims 1 to 5 dispersed in an aqueous medium. 9. An aqueous ink jet recording liquid comprising the surface-treated pigment according to claim 1 as a coloring agent. 10. The aqueous ink jet recording liquid according to claim 9, further comprising a non-adsorbing resin.