JP2002356626A - Method for producing water-dispersible organic pigment and aqueous organic pigment dispersion prepared thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for an organic pigment which is easily dispersible in water by a simple and convenient treatment and is excellent in water-dispersibility; and a stable organic pigment dispersion prepared by the method. SOLUTION: In the production method for a water-dispersible organic pigment the organic pigment is treated with high-temperature high-pressure water in a liquid or supercritical state at 120 deg.C or higher under a pressure of 4 MPa or higher. A stable organic pigment dispersion is produced by the production method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-dispersible organic pigment used in printing inks, water-based paints, jet inks and the like.
A method for producing a water-dispersible organic pigment excellent in water dispersibility, characterized by treating an organic pigment with water at a high temperature and a high pressure in a liquid state or a supercritical state at 0 ° C. or more and a pressure of 4 MPa or more. To an aqueous dispersion of an organic pigment having excellent stability.

[0002]

2. Description of the Related Art Organic pigments used as colorants in printing inks and paints are classified into phthalocyanine-based, isoindolinone-based, quinacridone-based, insoluble azo pigment-based, and perylene-based pigments. Developed and sold. However, organic pigments generally tend to agglomerate, and in order to form inks and paints, finely disperse pigments by using a dispersant such as a surfactant in combination with a roll mill or ball mill that has strong shearing force. Has been done. In the manufacturing process of inks and paints, this dispersing process is the most energy consuming process, and the addition of a dispersant can cause deterioration in the quality of the final product ink or paint.

[0003] In recent years, water-based inks and water-based paints have been increasingly used in inks and paints as environmental awareness increases. Therefore, there is a demand for a water-dispersible organic pigment which does not require an excessive dispersant and has a low energy cost for dispersion, and attempts have been made to improve the dispersibility by modifying the surface of the organic pigment particles.

[0004] The method is disclosed in Japanese Patent Application Laid-Open No. 12-219841.
JP, JP-A-12-219749, JP-A-9-19749
No. 031360, a method using an aqueous resin having a specific composition, and JP-A-5-080927 and JP-A-Hei.
A method using a surfactant described in JP-A-109720, a method for emulsification described in JP-A-5-163454, and a pigment described in JP-A-12-191974 and JP-A-5-112748. A method of producing a derivative on the surface of a pigment, a method of using a polar / non-polar solvent described in JP-A-5-255632, and the like have been proposed.

However, even in these proposed methods, it is still difficult to make the surface of the pigment essentially hydrophilic, and special skills are required because special resins, solvents, additives and the like are used. It has drawbacks and problems such as insufficient long-term dispersion stability. Further, there is a problem that a large amount of energy and time are required in order to make the degree of dispersion constant.

[0006]

The problem to be solved by the present invention is to provide a method for producing an organic pigment having excellent water dispersibility, which can be easily dispersed in water by a simple treatment, and an organic pigment produced by the method. It is to provide a stable organic pigment dispersion.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have found that various organic compounds such as phthalocyanine, isoindolinone, quinacridone, insoluble azo pigment, and perylene are available. The pigment is oxidized with high-temperature and high-pressure water or high-temperature and high-pressure water containing an oxygen donor such as hydrogen peroxide, and then, if necessary, the organic pigment is reduced with a reducing agent. It has been found that by introducing an oxygen-containing functional group having a hydrophilic property such as a hydroxyl group to improve the hydrophilicity of the particle surface, an organic pigment which can be easily dispersed in water or an organic pigment dispersion which is stably dispersed in water can be produced. Thus, the present invention has been completed.

That is, according to the present invention, an organic pigment is treated at a temperature of 120 ° C.
As described above, the method for producing a water-dispersible organic pigment is characterized in that the surface of the pigment is oxidized with high-temperature and high-pressure water in a liquid state or a supercritical state at a pressure of 4 MPa or more. But especially at temperatures between 120 ° C. and 550
This is a method for producing a water-dispersible organic pigment having a temperature of 4 ° C. and a pressure of 4 to 50 MPa.

Further, the production method of the present invention is a method for producing a water-dispersible organic pigment in which the high-temperature and high-pressure water is water containing an oxygen donor, if necessary.
This is a method for producing a water-dispersible organic pigment selected from at least one selected from the group consisting of oxygen, ozone, and hydrogen peroxide. Furthermore, the present invention includes an organic pigment aqueous dispersion produced by the above-mentioned production method of the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for producing organic pigment particles having poor water dispersibility by using high-temperature high-pressure water containing a subcritical and supercritical state or high-temperature high-pressure water containing an oxygen donor such as hydrogen peroxide. By introducing an oxygen-containing functional group having a hydrophilic property such as a hydroxyl group into the pigment surface, and then performing a reduction treatment with a reducing agent such as sodium borohydride if necessary, the pigment surface is oxidized. Of the introduced oxygen-containing functional groups, quinone groups having low hydrophilicity are converted to hydroxyl groups, and the hydrophilicity of the pigment surface is further improved, so that organic pigments that are easily dispersed in water, or stably dispersed in water. This is a method for producing a prepared organic pigment dispersion.

As the organic pigment used in the production method of the present invention, various organic pigments used for inks or coatings, that is, phthalocyanine, isoindolinone,
Organic pigments such as quinacridone-based, insoluble azo pigment-based, and perylene-based pigments can be used, and there is no particular limitation.
The average particle size of primary particles of these organic pigments is 5 to 300 n
m, more preferably 10 to 100
nm, particularly preferably 20 to 60 nm.

When the primary particle size is larger than 300 nm, even if the surface is made hydrophilic, the particles may not stably disperse in water and may settle. In addition, if a pigment smaller than 5 nm is oxidized with high-temperature and high-pressure water, it may be unsuitable for use as a coloring material such as ink due to a decrease in light resistance.

In the production method of the present invention, these organic pigments are charged into a reaction vessel capable of withstanding high temperature and high pressure, and then water is supplied into the reaction vessel by a high pressure pump. Here, if necessary, water obtained by adding an oxygen donor such as hydrogen peroxide to high-temperature and high-pressure water may be used. After reaching the predetermined pressure, the temperature is increased until the temperature reaches the predetermined temperature.

The high-temperature and high-pressure water referred to in the present invention means that the temperature is 1
Water in a liquid state or water in a supercritical state, including a subcritical region or a supercritical region at a temperature of 20 ° C. or more and a pressure of 4 MPa or more. There is no particular upper limit on temperature and pressure, but from a practical viewpoint, the temperature is 120 ℃ ~ 550 ℃, pressure is 4MPa ~
50 MPa, more practically, 220 ° C. to 360 ° C., 1
Water in the range of 0 MPa to 30 MPa is preferred.

The water to be used is not limited to purified water, but may be any water having few impurities, and may be ordinary tap water. However, it is preferable to use ion-exchanged water or distilled water called pure water. It is preferable from the viewpoint of impurity management.

In the present invention, the optimum reaction temperature is around 280 ° C. where the ionic product of water is maximized. Although the reaction mechanism is not clear, it is considered that the dissociation state of water is maximized in the subcritical state, and the ability to add hydrophilicity is maximized.
Above the critical temperature of water (374 ° C.), these tendencies decrease in reverse.

However, the oxygen addition ability itself is 380 ° C.
You can also see above. More oxygen-containing functional groups are introduced on the surface of the organic pigment, and then, by reducing the oxygen-containing functional groups among the oxygen-containing functional groups by applying a reducing agent to a functional group having a low hydrophilicity such as a quinone group, the amount is increased. Can be used to introduce a hydrophilic group into the organic pigment. The reason why the reduction treatment may be effective is that, when the organic pigment is oxidized with high-temperature and high-pressure water, the oxygen-containing functional group introduced to the pigment surface is, in addition to a highly hydrophilic hydroxyl group, a quinone group having a low hydrophilicity. Is included in some cases. Although the concentration of the oxygen donor used is not particularly limited, for example, when the oxygen donor is hydrogen peroxide, it is 0.1% by weight to 10% by weight, preferably 0.1% by weight to 2% by weight with respect to the water used. Add%.

The method of supplying the organic pigment and water to the reaction vessel is not particularly limited. A method of treating a mixture of the two in a closed vessel, a method of continuously supplying water to a vessel filled with the organic pigment, The method includes a supply method, a continuous reaction method in which an organic pigment is mechanically suspended in water in advance, and the organic pigment is continuously supplied to a reaction vessel and continuously discharged. The reaction time is not particularly limited, but the residence time in the reaction system is preferably 30 minutes or less when a continuous reaction is performed, and 30 minutes or less when a batch reaction is performed. The reason is that if the time of the oxidation treatment becomes longer, not only the pigment surface but also the inside thereof may be oxidized or a part of the pigment may be decomposed.

In the present invention, since the reaction solvent is water, an aqueous dispersion of an organic pigment containing no impurities can be obtained after the completion of the reaction, so that the aqueous ink or paint can be prepared without any special post-treatment. You can proceed. Even when an oxygen donor is used, if the oxygen donor is hydrogen peroxide, it is easily decomposed into water and oxygen by the high-temperature and high-pressure water in the reaction vessel, so no special post-treatment is required for aqueous inks and paints. Can proceed to the manufacturing process. Therefore, when it is preferable to add an oxygen donor, and if possible, it is preferable to use hydrogen peroxide that can be easily used by diluting a commercially available aqueous hydrogen peroxide solution with water.

However, in some cases, the organic pigment itself contains impurities. In some cases, these impurities are decomposed in high-temperature and high-pressure water, remain as a colloidal suspension or oil, and need to be separated. When such impurities requiring separation are generated, it is effective to charge only the organic pigment into the reaction vessel at a time and supply water continuously. In this way, most of the impurities are easily discharged from the reaction system together with the water.

A mixed slurry of an organic pigment and water is continuously supplied to a tubular reactor and the like, and reacted at a high temperature and a high pressure. Then, a continuous centrifugal separator is used to continuously recover the surface-modified organic pigment. A method to do this is also available. Oxygen is introduced into the surface of the organic pigment by the production method of the present invention, but the concentration and hydrophilicity of the oxygen-containing functional group to be introduced are different due to differences in operating conditions such as temperature and pressure.

When a hydrophilic oxygen-containing functional group such as a hydroxyl group is introduced on the surface of the pigment, a stable aqueous dispersion of the organic pigment can be obtained immediately, but the concentration of the oxygen-containing functional group is high.
When the concentration of the hydrophilic functional group is low, after the oxidation treatment with high-temperature and high-pressure water, the reducing agent is used to further reduce the quinone group having a low hydrophilicity among the introduced oxygen-containing functional groups, thereby reducing the hydrophilicity. A method of modifying to a high hydroxyl group is effective. As the reducing agent, known reducing agents such as hydrogen, sodium borohydride, lithium aluminum hydride and the like can be used, but it is preferable to use the reducing agent within a range that does not affect the color of the organic pigment. Among them, it is preferable to use a water-soluble reducing agent from the viewpoint of post-treatment and the like. For example, sodium borohydride, which is easy to handle, is preferably used.

According to the production method of the present invention, a simple treatment in an extremely short time (substantial reaction time is about 10 to 30 minutes) and no separation / purification step is required, or only a simple washing is required. An organic pigment excellent in water dispersibility or an aqueous dispersion of an organic pigment can be obtained.

[0024]

EXAMPLES Example 1 1.0 g of a copper phthalocyanine pigment (manufactured by Dainippon Ink and Chemicals, Inc.) was weighed and placed in a Hastelloy high-pressure container (capacity: 10 ml). Distilled water containing 2% hydrogen peroxide was continuously supplied to this container from the bottom of the container at a flow rate of 1 ml / min using a high-pressure plunger pump. The supplied liquid was discharged from the upper part of the container after coming into contact with the copper phthalocyanine pigment inside the container. A pressure control valve was provided at the outlet, and the pressure of the container was maintained at 25 MPa.

Here, a sintered filter is provided at the bottom and the top of the container to prevent the pigment from flowing out of the high-pressure container.
This high-pressure vessel was fixed in an electric heating furnace, and the internal temperature of the vessel was 2
The temperature was raised until it reached 80 ° C. After the internal temperature reached 280 ° C., the temperature was maintained for 30 minutes. After completion of the reaction, the temperature was lowered, and after confirming that the internal temperature was less than 100 ° C., the internal pressure was gradually lowered to return the internal pressure of the container to normal pressure. After confirming that the container was sufficiently cooled, the contents were taken out, and an aqueous dispersion of copper phthalocyanine stably dispersed was obtained.

The resulting dispersion maintained a stable dispersion even after standing for one month. After the dispersion was filtered, washed with water and dried, water was added to the obtained copper phthalocyanine pigment, and the mixture was gently shaken to obtain a copper phthalocyanine pigment dispersion which was dispersed stably again.

The amount of oxygen on the surface of the copper phthalocyanine pigment was determined by XP
When measured by the S method (X-Ray Photoelectoron Spectrometory, X-ray photoelectron spectroscopy), as shown in Table 1, the water-dispersible copper phthalocyanine pigment produced by the production method of the present invention was compared with the untreated one. It was confirmed that a relatively large amount of the oxygen-containing functional group was introduced. When the zeta potential was measured to check the stability of the water dispersibility, it was confirmed that the water dispersibility was more stable than that of the untreated product.

(Example 2) 1.0 g of copper phthalocyanine
It was weighed and put into a Hastelloy high-pressure container (volume: 10 ml). Using a high pressure plunger pump for this container,
Distilled water containing 2% hydrogen peroxide 1 m from the bottom of the container
It was fed continuously at a flow rate of 1 / min. The distilled water was discharged from the upper part of the container after coming into contact with the copper phthalocyanine pigment inside the container. A pressure control valve was installed at the outlet to maintain the pressure of the container at 23.5 MPa.

Here, a sintered filter was installed at the bottom and the top of the vessel to prevent the copper phthalocyanine pigment from flowing out of the high-pressure vessel. This high-pressure vessel was fixed in an electric heating furnace, and the temperature was raised until the internal temperature of the vessel reached 380 ° C. After the internal temperature reached 380 ° C, the temperature was maintained for 30 minutes. After the completion of the reaction, the temperature was lowered, and after confirming that the internal temperature was less than 100 ° C., the internal pressure was gradually lowered, and the internal pressure of the container was returned to normal pressure.
After confirming that the container was sufficiently cooled, the contents were taken out to obtain a copper phthalocyanine pigment dispersion liquid which was stably dispersed.

When the amount of oxygen and the zeta potential on the surface of the copper phthalocyanine pigment were measured in the same manner as in Example 1, it was found that the amount of surface oxygen increased and the dispersion stability increased. Table 1 shows the properties of the copper phthalocyanine pigment.

Comparative Example 1 1.0 g of the copper phthalocyanine pigment used in Example 1.2 was weighed and placed in a Hastelloy high-pressure container (capacity: 10 ml). Using a high pressure plunger pump, add 1 ml of distilled water to the container from the bottom of the container.
/ Min continuously. The supplied liquid was discharged from the upper part of the container after coming into contact with the copper phthalocyanine pigment inside the container. A pressure control valve was provided at the outlet, and the pressure of the container was maintained at 3.5 MPa.

Here, the high-pressure vessel was fixed in an electric heating furnace as in Example 1, and the temperature was raised until the internal temperature of the vessel reached 110 ° C. After the internal temperature reached 110 ° C., the temperature was maintained for 30 minutes. After the reaction is completed, the temperature is lowered and the internal temperature becomes 100
After confirming that the temperature became lower than 0 ° C., the internal pressure was gradually lowered to return the internal pressure of the container to normal pressure. After confirming that the container was sufficiently cooled, the contents were taken out. At this time, the copper phthalocyanine pigment was precipitated in water, was not sufficiently hydrophilized, and a stable dispersion of the copper phthalocyanine pigment dispersion could not be obtained. When the surface oxygen content was analyzed by XPS, the oxygen content was low as shown in Table 1.

[0033]

[Table 1]

Example 3 1.0 g of quinacridone magenta (manufactured by Dainippon Ink and Chemicals, Inc.) was weighed and placed in a high-pressure container (volume: 10 ml) made of Hastelloy. The high pressure vessel was then filled with distilled water containing 5% hydrogen peroxide, sealed and a pressure control valve was installed at the outlet. Thereafter, the high-pressure container was fixed in an electric heating furnace, and the internal temperature was raised to 280 ° C. while maintaining the pressure of the container at 17 MPa. After the internal temperature reached 280 ° C., the temperature was maintained for 10 minutes. After the reaction is completed, the temperature is lowered and the internal temperature is 100 ° C.
After confirming that the pressure was less than 1, the internal pressure was gradually lowered, and the internal pressure of the container was returned to normal pressure.After confirming that the container was sufficiently cooled, the contents were taken out to obtain a stable dispersion of the quinacridone magenta pigment dispersion. Was.

The surface oxygen atom concentration of untreated quinacridone magenta and the zeta potential of the quinacridone magenta dispersion liquid which was forcibly dispersed in water with ultrasonic waves were also measured. Table 2 shows the measurement results.

[0036]

[Table 2]

From the results shown in Table 2, it can be seen that the surface oxygen amount is increased by the treatment method of the present invention, and the dispersion stability in water is increased.

Example 4 A perylene maroon pigment dispersion was obtained in the same manner as in Example 3 except that perylene maroon was used as the pigment to be treated. The surface oxygen atom concentration of untreated perylene maroon was measured, and the measurement results are shown in Table 3.

[0039]

[Table 3]

From the results shown in Table 3, it can be seen that the surface oxygen amount is increased by the treatment method of the present invention. The zeta potential could not be measured because untreated perylene maroon was hardly dispersed in water even by using ultrasonic waves.

[0041]

The present invention provides a method for producing an organic pigment having excellent water dispersibility, which can be easily dispersed in water by a simple treatment, and a stable organic pigment dispersion produced by the method. Can be.

Claims (5)

[Claims] 1. An organic pigment having a temperature of 120 ° C. or higher and a pressure of 4 M
A method for producing a water-dispersible organic pigment, comprising treating with water at a high temperature and a high pressure in a liquid state or a supercritical state of Pa or more. 2. A high-temperature and high-pressure water having a temperature of 120 ° C. to 550
The method for producing a water-dispersible organic pigment according to claim 1, wherein the pressure is 4 ° C. to 50 MPa. 3. The method for producing a water-dispersible organic pigment according to claim 1, wherein the high-temperature high-pressure water is water containing an oxygen donor. 4. The oxygen donor is one or more selected from the group consisting of oxygen, ozone, and hydrogen peroxide.
3. The method for producing a water-dispersible organic pigment according to item 1. 5. An organic pigment aqueous dispersion produced by the production method according to claim 1. Description: