JPH10273606A - Water-based pigment dispersion and water-based ink-jet recording solution using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based pigment dispersion that is excellent in dispersion stabilit y and is useful as a water-based ink jet recording liquid by dispersing a specific oxidization-treated pigment in an aqueous medium. SOLUTION: The objective oxidation-treated 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) and is dispersed in an aqueous medium. This treated pigment is prepared by dispersing (A) a pigment, particularly a phthalocyanine pigment in sulfolane, adding sulfamic acid, then heating them at 60-200 deg.C and they are stirred for 0.5-15 hours. The treatment with sulfamic acid is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment dispersion having excellent dispersion stability and an aqueous ink jet recording liquid containing the same as a colorant.

[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 addition, there is no index for evaluating the relationship between the dispersibility and the method and degree of treatment in order to improve the dispersibility of the pigment. 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 an aqueous pigment dispersion having excellent dispersion stability, and a pigment dispersion type aqueous inkjet recording liquid having excellent initial, temporal and discharge stability. .

[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 /
An aqueous pigment dispersion obtained by dispersing an oxidized pigment having Sn) of 0.7 or more and 3.0 or less in an aqueous medium has excellent dispersion stability, and an aqueous inkjet recording liquid containing the aqueous dispersion as a colorant is The present invention has been found to be excellent in dispersion and discharge stability.

That is, according to the present invention, the specific surface area (Sn) of nitrogen gas is 60 m 2 / g or more and 200 m 2 / g or less, and the ratio (Sc / Sn) of the specific surface area (Sc) of carbon dioxide gas to the specific surface area (Sn) of nitrogen gas. The present invention relates to an aqueous pigment dispersion obtained by dispersing a pigment having a ratio of 0.7 to 3.0 in an aqueous medium. The present invention also relates to the aqueous pigment dispersion, wherein the oxidation treatment is a sulfamic acid treatment.

The present invention is also characterized in that the pigment is at least one pigment selected from phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments and carbon black. Regarding the dispersion. Further, the present invention relates to an aqueous inkjet recording liquid comprising the aqueous pigment dispersion as a colorant. Furthermore, the present invention relates to the above-mentioned aqueous inkjet recording liquid, comprising an aqueous resin.

[0010]

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

Specific surface area calculation formula S = s × Vm / Vo × KA S: specific surface area [m ² / g] s: molecular occupied sectional area [m ² ] Vm: monomolecular layer adsorption amount [cm ³ (standard state) / G] Vo: 22414 [cm ³ (standard condition)] KA: Avogadro number

The method of calculating the adsorption amount (Vm) of the monolayer 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
n) must be not less than 60 m ² / g and not more than 200 m ² / g. Oxidized pigments having a specific surface area (Sn) of nitrogen gas exceeding 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, an oxidized pigment having an Sn 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. When the Sn of the pigment to be oxidized is less than 60 m ² / g, the pigment is subjected to a salt milling treatment (an inorganic salt is used as a crushing aid and the primary particle diameter of the pigment is mechanically reduced before the oxidizing treatment). Process).

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 strongly with a kneader or the like to finely pulverize the mixture. 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.

The ratio of the specific surface area (Sc) of carbon dioxide gas to the specific surface area (Sn) of nitrogen gas of the oxidized pigment (Sc / S
n) must be greater than or equal to 0.7 and less than or equal to 3.0.
It is preferably from 08 to 3.0. Sc / Sn
Since the pigment having a value of less than 0.7 has high hydrophobicity, the stability in an aqueous medium becomes poor. On the other hand, a pigment having a Sc / Sn of more than 3.0 has high water solubility, and when used in an aqueous inkjet recording liquid, the pigment is eluted from the printed matter, resulting in poor water resistance.

Examples of the oxidation treatment of the pigment include ozone treatment, hypochlorous acid treatment, hydrogen peroxide treatment, fuming nitric acid treatment, nitric acid treatment, permanganic acid treatment, plasma treatment and the like, with sulfamic acid treatment being preferred. In the sulfamic acid treatment, the pigment is dispersed in sulfolane, and after adding sulfamic acid, the mixture is heated to 60 to 200 ° C. for 0.5 hours to 15 hours.
Perform by stirring for hours. After the heat treatment, sulfolane and sulfamic acid are repeatedly washed with water, centrifuged, and filtered from the pigment slurry.

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

When pigments are represented by color index (CI) numbers, CI pigment yellows 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.

Among the above pigments, from the viewpoint of light resistance,
Phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, and carbon black are preferably used. In some cases, two or more different pigments may be used in combination. To disperse the oxidized pigment in an aqueous medium, use a sand mill, a homogenizer,
An oxidized pigment, a dispersant, and an aqueous medium are placed in a disperser such as a ball mill, a paint shaker, or an ultrasonic disperser, and dispersed for several hours.

As the aqueous medium, water and, if necessary, an aqueous solvent are used. As the water, ion-exchanged water or distilled water from which metal ions or the like have been removed 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.

The pH of the aqueous pigment dispersion of the present invention is preferably adjusted to 6 to 10, particularly 7 to 9, in order to improve the dispersion stability. pH to desired pH
In order to adjust the pH, 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 aqueous pigment dispersion of the present invention has excellent dispersion stability and is therefore suitably used as a colorant for an aqueous inkjet recording liquid.

The aqueous inkjet recording liquid is prepared by adding water, an aqueous solvent, an aqueous resin, and It can be produced by adding an agent or the like to form an ink. The amount of the pigment in the ink jet recording liquid is not particularly limited, but is generally in the range of 1 to 15% by weight, preferably 1 to 10% by weight, based on the total weight of the recording liquid. Water is added so as to be in the range of 40 to 90% by weight of the recording liquid. 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 pigment to the substrate. 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 aqueous resin is contained in the recording liquid in an amount of 0.1%.
It is preferably contained in an amount of 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 the range 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 (25 ° C.) and a surface tension of 25, although it depends 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.

[0033]

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 specific methods of the pigment refining treatment and oxidation treatment, the method of preparing a pigment concentrate, and the methods of measuring Sn and Sc / Sn performed in Examples and Comparative Examples are shown below.

[Micronization treatment] A stainless steel 1 gallon kneader (manufactured by Inoue Seisakusho) was charged with 250 parts of pigment, 2500 parts of sodium chloride and 200 parts of diethylene glycol, 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.

[Oxidation treatment] 2 parts of pigment was treated with sulfolane 150
After heating at a temperature of 120 ° C., 3 parts of sulfamic acid were added, and the mixture was stirred and maintained for 4 hours.
Then, it was washed several times with sulfolane, poured into water, washed again with water, and dried to obtain an oxidized pigment.

[Preparation of concentrated recording liquid] The following materials were placed in a paint conditioner and dispersed for 3 hours to prepare a concentrated recording liquid for inkjet. Pigment 20.0 parts Purified water 79.7 parts Dimethylaminoethanol 0.1 part Antifungal agent ("Sodium Omazine" manufactured by Olin Chemical Co., Ltd.) 0.2 parts Total 100.0 parts

[Method of measuring Sn and Sc / Sn] The measurement was carried out 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.

(Examples 1 to 6 and Comparative Examples 1 to 5) A raw material having the following formulation was mixed to produce an aqueous ink jet recording liquid. Concentrated recording liquid (solid content 20%) 15.0 parts Dimethylaminoethanol 0.1 part Acrylic resin emulsion 3.0 parts (Nippon Polymer Co., Ltd., "W-215", solid content 30%) Glycerin 10.0 parts Anionic Surfactant 0.5 part ("Perex OTP" manufactured by Kao Corporation, solid content 70%) Antifungal agent ("Sodium Omazine" manufactured by Olin Chemical Co.) 0.3 part Sodium salt of ethylenediaminetetraacetic acid 0. 1 part Purified water 71.0 parts Total 100.0 parts

The obtained aqueous ink jet recording liquid was evaluated for filterability, initial average particle diameter, viscosity, stability over time, and printing stability. Table 1 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] The viscosity was 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). [Stability over time] Place 30 cc of the recording solution in a screw-necked bottle,
After standing at ℃ for one month, the average particle size of the recording liquid and 25
The viscosity at ℃ was measured and compared with that before standing. ：: 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 placed in a cartridge of an ink jet printer (“Desktop 560” manufactured by HP) and printed 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 recording liquid, disturbance of printing, and chipping were not observed during continuous printing. Δ: Non-discharge of the recording liquid at several places in the solid print portion during continuous printing was slightly observed. ×: Non-discharge of the recording liquid at several places in the solid printing portion during continuous printing was observed. -: The printing test was not performed.

[0042]

[Table 1]

Pigment * 1: Carbon black (CI Pigment Black 7) 2: Copper phthalocyanine blue (CI Pigment Blue 15: 3) 3: Dimethylquinacridone (CI Pigment Red 122) 4: Quinophthalone (CI Pigment Yellow 138) treatment * − : Not treated 1: Oxidation treatment 2: Fine processing + Oxidation treatment

[0044]

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 (5)

[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.
An aqueous pigment dispersion obtained by dispersing an oxidized pigment of 7 or more and 3.0 or less in an aqueous medium. 2. The aqueous pigment dispersion according to claim 1, wherein the oxidation treatment is a sulfamic acid treatment. 3. The pigment is at least one selected from phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments and carbon black.
3. The aqueous pigment dispersion according to claim 1, which is a kind of pigment. 4. An aqueous ink jet recording liquid comprising the aqueous pigment dispersion according to claim 1 as a coloring agent. 5. The method according to claim 4, further comprising an aqueous resin.
The aqueous inkjet recording liquid according to the above.