JP2003201419A - Pigment surface treatment method and water-dispersible pigment obtained thereby - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Without using a polymer compound such as a dispersant,
Provided is a production method for efficiently producing a pigment excellent in dispersion stability in water by a simple means by directly introducing a hydrophilic functional group to a pigment surface. SOLUTION: A hydrogen peroxide solution containing phthalocyanine is put into a reaction vessel 4, and an argon gas is bubbled through the solution from an argon gas cylinder 8 by bubbling. This reaction vessel 4 is immersed in a water tank 3 containing predetermined water, and the ultrasonic oscillator
Irradiate ultrasonic waves of kHz.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface treatment method for a pigment which is hydrophilized to have excellent dispersion stability in water by treating the surface of the pigment. More specifically, the present invention relates to a surface treatment method for an organic pigment such as phthalocyanine and the like. The present invention relates to a surface treatment method for carbon black.

[0002]

2. Description of the Related Art Generally, an organic pigment such as copper phthalocyanine or carbon black, which is a typical black colorant, is used for an aqueous pigment ink which is generally used for an ink jet ink. A compound containing an aromatic ring such as a benzene ring such as an organic pigment is generally insoluble and has a high surface hydrophobicity, so that the dispersion stability in water is low as it is.

Therefore, for example, the surface of fine pigment particles such as copper phthalocyanine is subjected to a hydrophilic treatment to improve dispersion stability in water. Examples of the hydrophilic treatment method for pigment fine particles include a microencapsulation method in which a polymer compound such as styrene acrylic resin that acts as a dispersant in water is attached to the surface of the pigment fine particles, or a hydroxyl group or a sulfone is directly added to the surface of the pigment fine particles. A method of introducing a highly hydrophilic functional group such as a group is known.

Among them, the microencapsulation method is a method in which a polymer compound is attached to the pigment particles while finely dispersing the pigment particles together with a polymer compound having an amphipathic property in a bead disperser or the like. A polymer compound is required as a dispersant, and a great deal of labor is required in the step of attaching the polymer compound to the pigment, which may cause a problem in terms of manufacturing cost.

Further, when a water-soluble organic solvent is added as a moisturizer or a surface tension adjusting agent to an aqueous dispersion of pigment particles produced by this method, the stability of the microencapsulated pigment particles may decrease. There may be a quality problem.

On the other hand, as a method for directly introducing a hydrophilic functional group into the surface of the pigment particle, the surface of the pigment particle is oxidized to introduce a hydroxyl group or the like, or, for example, JP-A-08-283596.
As disclosed in the publication, a method of reacting a reaction reagent to introduce a hydrophilic functional group such as a hydroxyl group, a carboxyl group and a sulfone group can be mentioned.

According to these methods, since the hydrophilic functional group is directly introduced into the surface of the pigment particle, and the components other than the pigment fine particles such as the dispersant are not contained, it is effective in reducing the raw material cost. In some cases.

As another method for producing a water-dispersible pigment, the pigment is subjected to plasma treatment in the presence of water vapor to decompose the water vapor and generate reactive active species such as hydroxy radicals to oxidize the surface of the pigment to introduce a hydroxyl group. A known surface oxidation method is known. This method is a simple and economical manufacturing method because it does not require a special reaction reagent or reaction solvent, but it is difficult to efficiently perform plasma treatment on the entire surface of pigment particles having an extremely large surface area and complicated shape. In many cases, as the scale of the equipment increases and the amount of pigment to be treated increases, the contact efficiency between radical species generated from water vapor and pigment particles by plasma treatment decreases, making it difficult to carry out on an industrial scale. There may be a problem such as.

Phthalocyanine, which is one of the organic pigments, can be hydrophilized by the above-mentioned surface treatment method or the like, but the above-mentioned surface treatment method is not always an efficient method because of problems in manufacturing cost and quality.

Further, studies have been made to improve various dispersibility even when the pigment is carbon black.
For example, as disclosed in Japanese Patent Application Laid-Open No. 08-319444, carbon black is oxidized in an aqueous solution containing a strong oxidant such as sodium hypochlorite to give a highly hydrophilic functional group such as a hydroxyl group or a carboxyl group. Although a method of introducing lactic acid to its surface is known, there are problems that a step of removing the solvent is required and that the manufacturing cost is increased due to the wastewater treatment.

As disclosed in JP-A-10-212426, there is also known a method of oxidizing carbon black in water using ozone as an oxidant. Insufficient to make hydrophilic to the extent that it can be used in pigment inks, or as disclosed in JP 2001-164148 A, carbon black after ozone oxidation treatment is treated with a disperser such as a mill. In the method of miniaturizing, there is a case where a part of carbon black that is not oxidized may be generated, so even if it is miniaturized after the oxidation treatment, some of the carbon black settles, etc., and it is used as an aqueous pigment ink. In some cases it was not possible.

By the way, it is known that the organic substance is oxidatively decomposed when ultrasonic waves are applied to water in which the organic substance is dissolved. As a mechanism for decomposing an organic substance by irradiating ultrasonic waves to this water, a part of the volatilized water is decomposed in cavitation bubbles in a high temperature and high pressure state generally generated by irradiating ultrasonic waves having a frequency of 20 kHz or more. It is considered that a hydroxy radical that acts as a strong oxidant is generated, and the organic substance is oxidatively decomposed by the oxidative action of this active oxygen species.

There is also a report that the production rate of hydrogen atoms and hydroxy radicals in water which decomposes in or near the cavitation bubbles becomes maximum at 200 kHz ("Ultrasonic application technology in environmental protection chemical process", Ultra Sonic TECNO 1997.7.).

Although the above-mentioned mechanism for producing hydroxy radicals is premised on the formation of cavitation bubbles, the frequency used for precision cleaning of silicon wafers and glass substrates for liquid crystal displays in recent years is from 500 kHz to 5 MHz.
There is also a report that hydroxy radicals are generated even in a megasonic cleaning tank that irradiates ultrasonic waves in water at a level that does not cause cavitation (“Future of megasonic cleaning”, ultrasonic TECNO 2
000.9. ).

In addition, water containing an organic compound containing a benzene ring such as styrene, bromobenzene or naphthalene is
There is also a report that the above organic compounds are decomposed by irradiating with an ultrasonic wave of 00 kHz (“Decomposition method of organic pollutants using ultrasonic waves”, ECO INDUSTRY V
ol. 4 No. 12 1999).

Further, it has been reported that when ozone is supplied into water while irradiating ultrasonic waves, the amount of hydroxyl radicals produced is increased (for example, Japanese Patent Laid-Open No. 2000-288495).
Issue).

[0017]

The problem to be solved by the present invention is to provide a manufacturing method for efficiently manufacturing a pigment having excellent dispersion stability in water by a simple means.

[0018]

The present inventors efficiently generate hydroxy radicals by oscillating ultrasonic waves in hydrogen peroxide water or ozone water, or water in which ozone and hydrogen peroxide are dissolved. Even if the pigment is water-insoluble, if the carbon chain in the pigment molecule can be decomposed by ultrasonic irradiation even if it is a water-insoluble pigment, active oxygen is bonded to this position to directly bind the hydrophilic functional group. The present invention has been completed as a result of earnestly investigating that the pigment can be made finer by cavitation by ultrasonic irradiation.

That is, the present invention provides a surface treatment method for a pigment, which comprises irradiating the pigment with ultrasonic waves in hydrogen peroxide water or ozone water, or water in which hydrogen peroxide and ozone are dissolved. It is a thing.

The pigment which can be made hydrophilic by the treatment method of the present invention is preferably an organic pigment or carbon black. The organic pigment is not particularly limited, and examples thereof include phthalocyanine pigments, quinacridone pigments, perylene pigments, dioxazine pigments, Examples include anthraquinone pigments.

For example, as the phthalocyanine, a phthalocyanine having no substituents on the four benzene rings in its molecular structure, or a part of the benzene ring is halogenated or alkylated to have a substantially hydrophilic property. A phthalocyanine having a substituent introduced therein, which may be a metal phthalocyanine containing a metal atom such as copper, iron or nickel in the center of its molecular structure, or a metal-free phthalocyanine.

Although a functional group having hydrophilicity such as a sulfone group is introduced into a part of the four benzene rings in the molecular structure, the contribution of phthalocyanine to the water dispersion stability is low, and the phthalocyanine is substantially hydrophobic. It may be a metallic phthalocyanine or a non-metallic phthalocyanine.

By irradiating the above phthalocyanine with ultrasonic waves in hydrogen peroxide water or ozone water, or in water in which hydrogen peroxide and ozone are dissolved, the phthalocyanine, which is originally hydrophobic, is directly hydrophilic to the surface such as hydroxyl groups. A functional group can be introduced, and phthalocyanine having excellent dispersion stability can be obtained.

Upon irradiation with ultrasonic waves, active oxygen species such as hydroxy radicals and active oxygen generated in water act on the surface of the pigment, and, for example, quinone groups and hydroxy radicals derived from only oxygen atoms are derived. It is considered that a hydroxyl group or a functional group containing oxygen such as a carboxyl group generated by the cleavage of the carbon chain in the pigment molecule by the action of the active oxygen species is generated. From the dispersion stability of the pigment, it is assumed that hydrophilic hydroxyl groups and carboxyl groups were directly introduced to the surface of the pigment.

In the present invention, it is also possible to use a water slurry of the organic pigment before the granulating and drying step. This water slurry is dispersed in water after the reaction step is completed, the pigment is transformed into a desired crystal form in a pigmentation step such as a solvent milling method, and the particle size is reduced to about 30 to 300 nm. Thus, it is possible to obtain an aqueous dispersion of the pigment whose pigment concentration is adjusted to about 1% to 5%.

As an advantage of using the water slurry of the organic pigment for the surface treatment of the present invention, the organic pigment is present in water in a state close to primary particles, and strongly aggregates like a pigment after granulation and drying. I can point out what I have not done. In addition, since the surface of dried and powdered organic pigment has extremely low hydrophilicity, a fine dispersion step may be required prior to the surface treatment step in order to disperse it in water, which leads to an increase in manufacturing cost. Therefore, the use of water slurry is advantageous in terms of manufacturing cost.

The carbon black that can be used in the present invention is not particularly limited, and various commercially available carbon blacks such as oil furnace black, gas furnace black, channel black and acetylene black can be used.

Some of these carbon blacks have a hydrophilic functional group such as a carboxyl group or a hydroxyl group on a part of their surface, and since these carbon blacks have relatively high dispersibility in water, It is suitable for surface treatment by ultrasonic irradiation in water according to the present invention. Examples of carbon blacks having relatively high dispersibility in water include "MA8" and "MA100" manufactured by Mitsubishi Chemical Corporation. Although the carbon blacks listed here have relatively high dispersion stability in water, the surface thereof is not hydrophilized to such an extent that it can be used in an aqueous pigment ink, and the hydrophilicity is further improved by using the method of the present invention. It cannot be suitably used as an aqueous pigment ink unless subjected to a chemical treatment.

Further, carbon black which does not contain many hydrophilic functional groups on its surface, for example, "#
The surface treatment method of the present invention can also be applied to "45", "# 960" and the like.

In general, although generation of hydroxy radicals is confirmed even when ultrasonic waves are applied to distilled water, it is observed that the amount of hydroxyl radicals is not so high in hydrogen peroxide water or ozone water or in water in which hydrogen peroxide and ozone are dissolved. It is considered that the irradiation with the sound wave can more efficiently introduce the functional group containing oxygen into the surface of the pigment. It should be noted that simply adding the pigment to hydrogen peroxide water, etc.
It has been confirmed that no oxygen-containing functional group is introduced onto the surface.

The concentration of the hydrogen peroxide solution may be 0.01% to 50%, and the present invention can be carried out without problems if it is in the range of 0.1% to 40%. Since the hydrogen peroxide solution that is generally commercially available has a concentration of 30%,
This hydrogen peroxide solution is appropriately prepared and can be suitably used if it is in the range of 5% to 30%.

In addition, ozone is generated by an ozone generator and dissolved in water to give a maximum of 15 ppm.
Since it is possible to produce a degree of ozone water, it is possible to use such ozone water.

Incidentally, by using hydrogen peroxide and ozone together,
It is also possible to use water in which these are dissolved, and in this case, the concentration may be appropriately adjusted according to the respective solubility as described above.

Considering that active oxygen species such as hydroxy radicals are generated in water regardless of the presence or absence of cavitation as described above, the frequency range of ultrasonic waves is not particularly limited, and practically from 20 kHz. It may be 5 MHz, and when considering the generation efficiency of active oxygen species, the range of 100 kHz to 1 MHz is preferable, and 200 kHz is particularly preferable.

The carbon black may be 20 kHz to 5 MHz in the same manner as described above.
Even in the range of 0 kHz to 40 kHz, the effect can be sufficiently exerted on dispersion stability and atomization.

By bubbling a rare gas, which is a monoatomic molecule such as argon or helium, in hydrogen peroxide solution, the rare gas diffuses into the cavitation bubbles and the bubbles are adiabatically compressed by the action of ultrasonic waves. Therefore, it is considered that the temperature inside the cavitation bubble becomes higher than that in the case where there is no rare gas, the decomposition of surrounding water molecules is further promoted, and the efficiency of generating active oxygen species is increased.

Therefore, for example, the frequency is 200 kHz.
In the case of irradiating the hydrogen peroxide solution with the ultrasonic wave, the rare gas such as argon or helium is preferably dissolved in advance, or the rare gas is preferably continuously aerated while the ultrasonic wave is being irradiated.

FIG. 1 shows a schematic view of a processing apparatus which is an embodiment for carrying out the surface treatment method of the pigment according to the present invention.
FIG. 2 shows a schematic view of a processing apparatus which is another embodiment. FIG. 1 shows a batch type ultrasonic oscillator, and FIG. 2 shows a circulation type ultrasonic oscillator. 1 is an ultrasonic transmitter, 2 is an ultrasonic oscillator, 3 is a water tank, 4 is a container for containing an aqueous dispersion of pigment, 5 is a thermometer for measuring the liquid temperature, 6 is a cylinder of oxygen or compressed air, Reference numeral 7 is an ozone generator, which can generate ozone from oxygen of 6 or oxygen introduced from a compressed air cylinder. 8 is a noble gas cylinder, 9
Is a circulation pump.

As described above, it is also possible to bubble air, oxygen or the like in addition to the above rare gas. In particular, oxygen is supplied to the discharge type ozone generator and ultrasonic waves are generated while a mixed gas of ozone and oxygen is passed through water. It is expected that the functional group containing oxygen will be efficiently introduced into the pigment surface by irradiating with.

The functional groups introduced into the surface of the organic pigment or carbon black by irradiating ultrasonic waves in hydrogen peroxide water or ozone water are considered to be a hydroxyl group and a quinone group. It is also possible that a carboxyl group may be generated due to the cleavage of the benzene ring of, and it is unclear which functional group was produced at what concentration, but at least part of it was a highly hydrophilic oxygen such as a hydroxyl group or a carboxyl group. It is believed that the contained functional groups are introduced on the pigment surface.

As a basis for this, for example, even if the phthalocyanine is forcibly dispersed in water, the phenomenon that the phthalocyanine is eventually aggregated and settled is observed, but after the ultrasonic irradiation, the phthalocyanine is observed to be aggregated and settled in the water. This is because it is possible to visually confirm that the dispersion is stable over a long period of time.

Although the measurement of zeta potential is effective as a method for evaluating the dispersion stability of particles in water, the zeta potential of phthalocyanine treated by the method of the present invention was measured, and it was found that it was higher than that of untreated phthalocyanine. It is confirmed that the dispersion stability in water is also increased because the zeta potential is clearly decreased.

The inventors of the present invention added hydrogen peroxide solution having a concentration of 30% to distilled water having a pH of 6.50 to obtain a concentration of 10%.
% Hydrogen peroxide solution was prepared to prepare a hydrogen peroxide solution having a pH of 4.51, and the change in pH due to ultrasonic irradiation was examined. 0.5 g of copper phthalocyanine was added to 49.5 g of this hydrogen peroxide solution (F manufactured by Dainippon Ink and Chemicals, Inc.
Astogen Blue 5380E) is dispersed, ultrasonic waves having a frequency of 200 kHz and an output of 200 W are irradiated for 1 hour using W-200-HF MK-II (manufactured by Honda Electronics Co., Ltd.), and then the pH of the dispersion is measured. Then, it was lowered to 3.56, and it was confirmed that an acidic component was clearly generated.

While filtering this dispersion through a membrane filter having a pore size of 5 μm, the wet cake of copper phthalocyanine remaining on the filter was washed thoroughly with water and dispersed again in distilled water having a pH of 6.50. It was 5.05.

From this, at least a part of the acidic component is derived from the copper phthalocyanine after ultrasonic irradiation, and is due to the action of the hydroxyl group or the carboxyl group of the oxygen-containing functional groups introduced on the surface. It is thought to be something.

A pH of 4.51 prepared by the same method
It has been confirmed in advance that the pH hardly changes even if only 49.5 g of the hydrogen peroxide solution is irradiated with the ultrasonic waves.

Further, as a result of performing surface element analysis of the copper phthalocyanine after the treatment by ultrasonic irradiation using ESCA-850 (manufactured by Shimadzu Corporation), the element existing on the surface is carbon which is a constituent element of copper phthalocyanine. It has also been confirmed that only oxygen atoms, which are considered to be derived from functional groups containing nitrogen, copper, and oxygen, and no other element is observed.

It is considered that the greater the amount of hydrophilic oxygen-containing functional groups introduced onto the surface of the pigment, the higher the dispersion stability in water. Since it is also possible to make small, the effect of micronization by ultrasonic irradiation and the effect of introducing a hydrophilic oxygen-containing functional group to the pigment surface act synergistically, resulting in excellent dispersion stability in water. Pigments can be produced.

Further, it is considered that the oxygen-containing functional group introduced into the surface of the pigment by the treatment method of the present invention includes a quinone group having low hydrophilicity. This quinone can be converted to a hydroxyl group by the action of a reducing agent,
By causing a reducing agent such as sodium borohydride to act on the pigment dispersion treated by the method of the present invention, the quinone group on the pigment surface can be converted into a hydroxyl group to further enhance dispersion stability. After the reduction treatment, unreacted reducing agent and by-products may be separated and removed from the dispersion using an ultrafiltration membrane or the like.

[0050]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. (Surface element composition analysis) For surface element analysis, ESCA-850 manufactured by Shimadzu Corporation was used. (Zeta potential measurement) For the zeta potential measurement, a zeta potential measuring device (PEN KEM, INC LAZER ZE) is used.
E METER MODEL 501) was used. (Measurement of particle size distribution) MICROTRAC UPA150 manufactured by Nikkiso Co., Ltd. was used for particle size and particle size distribution measurement.

Example 1 Distilled water was added to 16.7 ml of hydrogen peroxide solution having a concentration of 30% (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare 100 ml of a hydrogen peroxide solution having a concentration of 5%.
The mixture was put into a four-necked flask equipped with a stirrer and having a volume of 200 ml. This flask was immersed in a water tank having an ultrasonic vibrator attached to the bottom. The water tank was previously filled with tap water up to a predetermined water level, and the water temperature was adjusted to 25 ° C.
Argon gas was bubbled into the hydrogen peroxide solution in the flask for about 10 minutes at a flow rate of 200 ml per minute using a nozzle. Subsequently, copper phthalocyanine (Fast
Ogen Blue 5380E) (0.5 g) was added and stirring was started. Ultrasonic oscillator W-200-HF MK-II under argon gas ventilation while maintaining the water temperature at 25 ° C.
(Manufactured by Honda Electronics Co., Ltd.), 200 kHz, 20
After irradiation with 0 W ultrasonic waves for 1 hour, stirring and aeration of argon gas were stopped, and the dispersion liquid in the flask was recovered.

Approximately 20 ml was separated from the recovered liquid and the pore size was 5 μm.
m was filtered under reduced pressure using a membrane filter and washed with distilled water. After washing with water, it was further washed with methanol (manufactured by Wako Pure Chemical Industries, Ltd.) to completely remove water. Then, filter the residue on the membrane filter to 80
It was dried at 0 ° C. for 2 hours to obtain a sample 1 for surface elemental analysis.

Further, the remaining 80 ml of the recovered liquid was similarly filtered under reduced pressure using a membrane filter and washed with distilled water. The wet cake-like filter residue after washing with water is redispersed in distilled water to obtain an aqueous dispersion of copper phthalocyanine, and about 1 ml of this dispersion is further diluted with distilled water to obtain a test solution 1 for measuring zeta potential. Obtained.

(Example 2) Take 100 ml of hydrogen peroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 30%, and add 200 ml.
The dispersion liquid in the flask was recovered in the same manner as in Example 1 except that the four-necked flask with a stirrer of ml volume was charged.

Then, a sample 2 for surface element analysis and a test liquid 2 for zeta potential measurement were obtained in the same procedure as in Example 1.

Example 3 A polypropylene container having a capacity of 100 ml was charged with zirconia beads having a diameter of about 1.5 mm to about half the capacity, and then 2.0 g of copper phthalocyanine as in Example 1 and 20 g of distilled water were charged. Finely dispersed for 30 minutes using a paint shaker. The dispersion was separated and collected from the zirconia beads, and 33.3 ml of 30% hydrogen peroxide water was added, and further 46.7 ml of distilled water was added to prepare 100 ml of a 10% hydrogen peroxide aqueous dispersion containing copper phthalocyanine. This dispersion was placed in a polypropylene container having a volume of 250 ml, and argon gas was bubbled through the dispersion for about 10 minutes. After that, the polypropylene container was closed with a lid and immersed in a water tank with an ultrasonic vibrator attached to the bottom, and then the ultrasonic oscillator W-200-HF MK-II (Honda Ultrasonic waves of 200 kHz and 200 W were applied for 2 hours using Denshi Co., Ltd., and then the polypropylene container was removed to recover the dispersion liquid.

Thereafter, a sample 3 for surface element analysis and a test liquid 3 for zeta potential measurement were obtained in the same procedure as in Example 1.

Example 4 A 10% hydrogen peroxide aqueous dispersion containing copper phthalocyanine was prepared in the same procedure as in Example 3. Ultrasonic Cleaner (US Ltd. US-
The dispersion liquid was collected in the same manner as in Example 3 except that the ultrasonic wave of 38 kHz and 150 W was irradiated for 1 hour using 3).

Then, a sample 4 for surface elemental analysis and a test solution 4 for zeta potential measurement were obtained in the same procedure as in Example 1.

Example 5 A 10% hydrogen peroxide aqueous dispersion containing copper phthalocyanine was prepared in the same procedure as in Example 3. High frequency ultrasonic cleaner (W-
The dispersion was recovered in the same manner as in Example 3 except that the ultrasonic wave having a frequency of 1 MHz and 600 W was applied for 1 hour.

Thereafter, a sample 5 for surface element analysis and a test solution 5 for zeta potential measurement were obtained in the same procedure as in Example 1.

Comparative Example 1 A 10% aqueous hydrogen peroxide dispersion containing copper phthalocyanine was prepared in the same manner as in Example 3. After that, the influence of the oxidation reaction of hydrogen peroxide was examined in Examples 1 to 1.
The dispersion was left for 1 hour in the same manner as in Example 5, and the dispersion was recovered in the same manner as in Example 3 except for the above.

Then, a comparative sample 1 for surface element analysis and a comparative test solution 1 for zeta potential measurement were obtained in the same procedure as in Example 1.

Table 1 shows the measurement results of these samples 1 to 5, comparative sample 1, test liquids 1 to 5, and comparative test liquid 1.

[0065]

[Table 1]

From the results shown in Table 1, it is considered that in the samples of Examples 1 to 5, the elements present on the surface are derived from functional groups containing oxygen in addition to the constituent elements of copper phthalocyanine, carbon, nitrogen and copper. It can be seen that although oxygen atoms are observed, oxygen atoms are not observed in the sample of Comparative Example 1.
Further, in the test liquids of Examples 1 to 5, the zeta potential was clearly lower than that of the comparative test liquid of Comparative Example 1 which was not irradiated with ultrasonic waves, and the dispersion stability in water was increased. I understand that.

Example 6 100 g of an aqueous slurry containing 3.3% of copper phthalocyanine pigmented by the salt milling method was placed in a polypropylene container having a capacity of 250 ml, and the ultrasonic vibrator shown in FIG. It was immersed in an aquarium. The ultrasonic irradiation device has a frequency of 38 kHz and 150 W
Ultrasonic cleaner US-3 manufactured by SND Co., Ltd. was used, and the water temperature in the water tank was kept at 25 ° C. This water slurry was irradiated with ultrasonic waves for 5 hours while aerating oxygen containing ozone at 0.5 l / min. Here, ozone was manufactured using oxygen (purity 99.9%) manufactured by Nippon Oxygen Co., Ltd. using an ozone generator AOC-C-052ATEF manufactured by Yasunaga Co., Ltd.

The dispersion liquid after ultrasonic irradiation was collected, and a part of the dispersion liquid was filtered under reduced pressure using a membrane filter having a pore size of 0.025 μm and washed with distilled water. After washing with water, it was further washed with methanol (manufactured by Wako Pure Chemical Industries, Ltd.) to completely remove water. Subsequently, the filter residue on the membrane filter was dried at 80 ° C. for 2 hours to obtain a sample 6 for surface elemental composition analysis.

20 g of the dispersion liquid after ultrasonic irradiation was taken, and 0.1 g of sodium borohydride was added with stirring.
After 2 hours, the membrane was again filtered under reduced pressure using a membrane filter having a pore size of 0.025 μm, and washed with distilled water.

The wet cake after washing with water was recovered and redispersed in distilled water to measure the zeta potential.
It was mV. The volume average particle diameter was 125 nm. 1N sodium hydroxide was added dropwise to this dispersion,
The pH was adjusted to about 8. This dispersion is extremely stable,
It was observed for more than a month, but no precipitation of copper phthalocyanine particles was observed.

Example 7 100 g of a water slurry containing 3.6% of quinacridone magenta after the pigmentation step was irradiated with ultrasonic waves having a frequency of 38 kHz for 2 hours in the same manner as in Example 6 in the presence of ozone. Then, using the treatment device of FIG.
Ultrasonic waves having a frequency of 1.7 MHz were irradiated for 3 hours using USV-48Z1700S manufactured by Ultrasonic Industrial Co., Ltd.

Further, a sample 7 for surface analysis was prepared in the same manner as in Example 6, and sodium borohydride was added to the dispersion liquid after ultrasonic irradiation. After a lapse of 2 hours, the zeta potential and the volume average particle diameter of the dispersion obtained by filtering and washing with water were measured, and each was found to be -48.3 m.
V, 183 nm. Also, as in Example 6, p
The dispersion in which H was adjusted to about 8 was extremely stable, and no sedimentation of particles was observed for 1 month or longer.

Example 8 1.0% of perylene maroon
In the same manner as in Example 6, 100 g of the contained water slurry was irradiated with ultrasonic waves having a frequency of 38 kHz for 5 hours in the presence of ozone. The dispersion liquid after ultrasonic irradiation was collected, and Sample 8 for surface analysis was prepared in the same manner as in Example 6.

Example 9 3.0 g of carbon black "MA8" manufactured by Mitsubishi Chemical Co., Ltd. and 97.0 g of distilled water were placed in a polypropylene container having a volume of 250 mL, and ozone was aerated in the same manner as in Example 6 below. While the frequency is 38
The ultrasonic wave of kHz was irradiated for 5 hours.

The dispersion after the ultrasonic irradiation was recovered and
Sample 9 for surface analysis was prepared in the same manner as in. Furthermore, when a part of the dispersion liquid was filtered and washed with water to measure the zeta potential and the volume average particle diameter, −66.2 mV and 72, respectively.
was nm. Further, the dispersion liquid in which the pH was adjusted to about 8 in the same manner as in Example 6 was extremely stable, and no sedimentation of particles was observed for one month or longer.

(Example 10) A water dispersion of carbon black "MA8" was carried out in the same manner as in Example 9 except that the frequency of ultrasonic waves to be irradiated was 200 kHz, and compressed air was used instead of oxygen as a raw material for producing ozone. A liquid was obtained. Here, for ultrasonic irradiation, Honda Electronics Co., Ltd. W-200-HF MK-
II was used.

A sample 10 for surface elemental composition analysis was prepared by the same procedure as in Example 6 and subjected to reduction treatment with sodium borohydride, and the zeta potential and the volume average particle diameter were measured. -70.2 mV, 8
The dispersion liquid having a size of 1 nm and a pH adjusted to about 8 was extremely stable, and no sedimentation of particles was observed for one month or longer.

(Example 11) 1.0 g of carbon black "# 45" manufactured by Mitsubishi Chemical Co., Ltd. and 99.0 g of distilled water were placed in a polypropylene container having a capacity of 250 mL, and ozone was added in the same manner as in Example 7 below. In the presence, the frequency is 38k
An ultrasonic wave of Hz was applied for 2 hours, and an ultrasonic wave of a frequency of 1.7 MHz was applied for 3 hours.

The dispersion after the ultrasonic irradiation was recovered and
Sample 11 for surface analysis was prepared in the same manner as in. Further, a part of the dispersion liquid was filtered and washed with water to measure the zeta potential and the volume average particle diameter, which were respectively -67.4 mV and 1
It was 53 nm. Further, the dispersion liquid in which the pH was adjusted to about 8 in the same manner as in Example 6 was extremely stable, and no sedimentation of particles was observed for one month or longer.

(Results of Surface Elemental Analysis) In order to compare the samples 6 to 11 obtained in Examples 6 to 11 with the surface elemental composition before treatment, respectively, an aqueous slurry of copper phthalocyanine and an aqueous slurry of dimethylquinacridone (magenta) were prepared. , Perylene, MA8, # 45 were prepared in the same procedure as in Example 1 to examine the surface elemental composition.

Tables 2 to 6 show the respective pigments of Examples 6 to 11 and the surface elemental composition analysis results of the pigments thereof before treatment.

[0082]

[Table 2]

[0083]

[Table 3]

[0084]

[Table 4]

[0085]

[Table 5]

[0086]

[Table 6]

From the results of Tables 2 to 6, it is found that the amount of oxygen atoms which is considered to be derived from the functional group containing oxygen is increased by the treatment method of the present invention in all the samples of Examples 6 to 11. I understand.

(Example 12) Aqueous dispersion 10 containing 3.0 g of carbon black "MA8" manufactured by Mitsubishi Chemical Corporation.
0 g was prepared, and ultrasonic waves having a frequency of 38 kHz were irradiated for 5 hours while aerating oxygen containing ozone at a flow rate of 0.5 l per minute. The particle size distribution of the aqueous dispersion after irradiation is shown in FIG. The dispersion stability of carbon black in the obtained dispersion was good, and as can be seen from the particle size distribution in FIG. 3, the carbon black after the treatment was fine, and no aggregates were confirmed in this dispersion. It was

(Comparative Example 2) Except that oxygen containing ozone was not ventilated and ultrasonic waves of 38 kHz were irradiated for 5 hours,
An aqueous dispersion was obtained in the same manner as in Example 12. The particle size distribution of the aqueous dispersion after irradiation is shown in FIG. In the obtained dispersion, precipitation of agglomerates was confirmed after a while.

(Comparative Example 3) An aqueous dispersion was obtained in the same manner as in Example 12, except that the ultrasonic wave of 1 MHz was irradiated for 5 hours without passing oxygen containing ozone. As for the particle size distribution of the aqueous dispersion after irradiation, as shown in FIG. 5, although miniaturization was promoted as compared with Comparative Example 2, precipitation of aggregates was confirmed after a while and dispersion stability was poor.

(Comparative Example 4) An aqueous dispersion was obtained in the same manner as in Example 12 except that stirring was carried out without irradiating ultrasonic waves while aerating oxygen containing ozone. In the obtained aqueous dispersion, there were aggregates of a size that could be visually confirmed, and after standing for a while, precipitation of carbon black was also confirmed.

[0092]

As described above in detail, according to the surface treatment method for a pigment of the present invention, it becomes possible to hydrophilize by directly introducing an oxygen-containing functional group into the surface of the pigment, and It is possible to provide a pigment having excellent dispersibility, which can be suitably used for a fine aqueous pigment ink or the like.
Further, by the oxygen-containing functional group introduced on the pigment surface, a complex with a polymer compound by grafting or a silane coupling agent is added to newly introduce an amino group, a vinyl group, or the like, so that it can be used in various solvents. It can also be expected to improve dispersibility and compatibility with polymer compounds.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for treating a surface of a pigment according to the present invention,
The schematic diagram of the batch type processing apparatus which is one Embodiment.

FIG. 2 is a diagram illustrating a method of treating a surface of a pigment according to the present invention,
The schematic diagram of the circulation distribution type processing apparatus which is another embodiment.

FIG. 3 is a particle size distribution chart after irradiating ultrasonic waves having a frequency of 38 kHz while aerating ozone in a water dispersion liquid of carbon black.

[Fig. 4] Frequency of 38 kHz for an aqueous dispersion of carbon black
The particle size distribution chart after irradiating the ultrasonic wave of z.

FIG. 5: Frequency of 1 MHz in an aqueous dispersion of carbon black
Of particle size distribution after irradiating the ultrasonic waves.

[Explanation of symbols]

1 Ultrasonic transmitter 2 Ultrasonic transducer 3 aquarium 4 reaction vessels 5 thermometer 6 Oxygen or compressed air cylinder 7 Ozone generator 8 rare gas cylinders 9 Circulation pump

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Claims (6)

[Claims] 1. A method for surface treatment of a pigment, which comprises irradiating the pigment with ultrasonic waves in hydrogen peroxide water or ozone water, or in water in which hydrogen peroxide and ozone are dissolved. 2. The method for surface treatment of a pigment according to claim 1, wherein the oscillation frequency of the ultrasonic wave is in the range of 20 kHz to 5 MHz, and the pigment is an organic pigment. 3. The surface treatment method for a pigment according to claim 2, wherein the ultrasonic wave has an oscillation frequency of 200 kHz. 4. The surface treatment method for a pigment according to claim 1, wherein the oscillation frequency of the ultrasonic wave is in the range of 20 kHz to 40 kHz, and the pigment is carbon black. 5. The ultrasonic wave irradiation according to claim 1, wherein a rare gas is introduced into the hydrogen peroxide solution or the ozone water, or water in which the hydrogen peroxide and ozone are dissolved, and ultrasonic waves are applied. Pigment surface treatment method. 6. A water-dispersible pigment obtained by the method for surface treatment of a pigment according to claim 1.