JP2002129065A - Production method for carbon black having water dispersibility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for a carbon black excellent in water dispersibility, easily dispersed in water by an easy treatment, and to provide a dispersion liquid for a stable carbon black produced thereby. SOLUTION: The carbon black having a water dispersibility is produced by treating the carbon black with a high-temperature and high-pressure water in the liquid or supercritical state of a temperature of 120 deg.C or above and a pressure of 4 MPa or above, or with the high-temperature and high-pressure water having an oxygen donor, and further, if necessary, with a reduction agent, and the water dispersion liquid for carbon black produced thereby is provided.

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 water-dispersible carbon black for use in printing inks, water-based paints, jet inks and the like. A method for producing a water-dispersible carbon black having excellent water dispersibility, comprising treating carbon black particles with high-temperature and high-pressure water in a state or a supercritical state, and carbon having excellent stability produced by the method. It relates to a black aqueous dispersion.

[0002]

2. Description of the Prior Art Carbon black, which is used as a black colorant in printing inks and paints, generally tends to agglomerate. Fine dispersion of carbon black is performed by using a roll mill or a ball mill having power. This dispersing step is the most energy-consuming step in the production process of inks and paints, and the addition of a dispersant can cause deterioration of the quality of inks and paints as final products.

[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 carbon black 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 carbon black particles.

As the method, a method of grafting a hydrophilic polymer to the surface of carbon black described in JP-A-6-301239 and JP-A-8-337624, a method disclosed in JP-A-11-349212 and a method disclosed in JP-A-11-34912 are disclosed. 3
A method of introducing various hydrophilic functional groups such as a sulfone group and an amino group by an organic synthetic technique described in No. 49315 has been proposed.

However, since the surface of carbon black is inherently poor in reactivity, the grafting rate is low and sufficient dispersion stability cannot be obtained, and various chemicals must be used to introduce functional groups. There is a problem that the reaction requires a long time, and the separation and purification of the finally modified carbon black requires much more energy and time.

[0006]

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

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, carbon black particles were subjected to high-temperature and high-pressure water containing high-temperature and high-pressure water or an oxygen donor such as an oxidizing agent. By treating with water and further treating with a reducing agent as necessary, an oxygen-containing group is introduced into the surface of carbon black to improve the hydrophilicity of the surface of the carbon black particles, and carbon black that is easily dispersed in water, Alternatively, they have found that a carbon black dispersion liquid dispersed in water can be produced stably, and have completed the present invention.

That is, the present invention provides: (1) carbon black at a temperature of 120.degree.
Treating with high-temperature and high-pressure water in a liquid state or a supercritical state of Pa or more, a method for producing a water-dispersible carbon black,

(2) High-temperature, high-pressure water has a temperature of 120 ° C. to 55 ° C.
The method for producing a water-dispersible carbon black according to (1), wherein the temperature is 0 ° C. and the pressure is 4 MPa to 50 MPa;

(3) The method for producing water-dispersible carbon black according to (1) or (2), wherein the high-temperature high-pressure water is water containing an oxygen donor.

(4) The method for producing water-dispersible carbon black according to (3), wherein the oxygen donor is at least one selected from oxygen, ozone, and hydrogen peroxide.

(5) The method for producing water-dispersible carbon black according to any one of (1) to (4), wherein the carbon black treated with high-temperature and high-pressure water is further treated with a reducing agent.

(6) The method for producing a water-dispersible carbon black according to (5), wherein the reducing agent is at least one selected from the group consisting of hydrogen, sodium borohydride, and lithium aluminum hydride.

(7) An aqueous carbon black dispersion produced by the production method according to any one of the above (1) to (6).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to treating carbon black particles which have essentially no water dispersibility with high-temperature and high-pressure water containing subcritical and supercritical water or high-temperature and high-pressure water containing an oxygen donor such as an oxidizing agent. Then, if necessary, by treating with a reducing agent, a hydrophilic group is introduced into the surface of the carbon black, and the carbon black is easily dispersed in water by greatly improving the hydrophilicity of the surface of the carbon black particles. This is a method for producing a carbon black dispersion liquid that is stably dispersed in water.

As the carbon black used in the production method of the present invention, any known carbon black used for inks or paints can be used, and there is no particular limitation. Furnace black, channel black, lamp black, thermal black, acetylene black, and the like, or those obtained by previously oxidizing these with an oxidizing agent may be used. The average particle diameter of these primary particles is 5 to 100 nm, preferably 20 to 60 nm.

In the production method of the present invention, first, carbon black is charged into a reaction vessel capable of withstanding high temperature and 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 a small amount of impurities, and may be ordinary tap water. However, it is preferable to use ion-exchanged water called distilled water or distilled 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.
As described above, the tendency for further improvement is seen, and a production method in which more hydrophilic groups are introduced into carbon black by introducing more oxygen-containing groups into carbon black and then reducing these groups can also be used. Although the concentration of the oxygen donor to be used is not particularly limited, 0.1% by weight to 10% by weight, preferably 0.1% by weight to 2% by weight is added to the water used.

The method of supplying the carbon black and water to the reaction vessel is not particularly limited. A method of treating a mixture of both in a closed vessel, a method of continuously supplying water to a vessel charged with carbon black. A supply method or a continuous reaction method in which carbon black is mechanically suspended in water in advance, this is continuously supplied to a reaction vessel, and continuously discharged, and the like. The reaction time is not particularly limited, but when a continuous reaction is performed, the residence time in the reaction system is preferably within 30 minutes.

In the present invention, since the reaction solvent is water, an aqueous dispersion of carbon black 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 such as an oxidizing agent 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 that no special post-treatment is required. Proceed to the production process of water-based inks and paints.

However, there are cases where carbon black itself contains impurities. Most of these impurities are decomposed in high-temperature, high-pressure water, but some remain as colloidal suspensions or oils, and may need to be separated. When such impurities occur, it is effective to charge only the carbon black into the reaction vessel at a time and continuously supply water. In this way, most of the impurities are easily discharged from the reaction system together with the water.

After continuously supplying a mixed slurry of carbon black and water to a tubular reactor or the like and reacting the mixture at a high temperature and a high pressure, the carbon black whose surface has been modified by continuous treatment with a centrifugal separator is continuously collected. A method to do this is also available. Oxygen is introduced to the surface of carbon black by the production method of the present invention, but due to differences in operating conditions such as temperature and pressure,
The concentration and hydrophilicity of the oxygen-containing groups introduced are different.

When a hydrophilic oxygen-containing group is introduced,
Immediately, a stable aqueous dispersion of carbon black is obtained, but when the concentration of the oxygen-containing group is high but the concentration of the hydrophilic group is low, the introduced oxygen-containing group is further converted to a hydrophilic group using a reducing agent. Is effective. As the reducing agent, known reducing agents such as hydrogen, sodium borohydride, and lithium aluminum hydride can be used, and there is no particular limitation.However, it is preferable to use a water-soluble reducing agent from post-treatment and the like. Sodium borohydride is preferably used.

For example, carbon black treated with high-temperature, high-pressure water is introduced into an aqueous solution in which sodium borohydride is dissolved in a 0.1 N aqueous sodium hydroxide solution, and reacted for about 10 minutes to 2 hours to cause oxygen-containing functional groups on the carbon black surface. By reducing and hydrophilizing the groups and filtering and washing, a stable aqueous dispersion of carbon black can be obtained.

According to the production method of the present invention, an extremely short time (substantially the reaction time is about 30 minutes) is a simple treatment, and does not require a separation / purification step, or the water is dispersed only by a simple washing. Carbon black or an aqueous dispersion of carbon black having excellent properties can be obtained.

[0029]

EXAMPLES Example 1 1.0 g of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: # 45) was weighed and placed in a high-pressure container (volume: 10 ml) made of Hastelloy. 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 carbon black inside the container. A pressure control valve was installed at the outlet to maintain the pressure of the container at 25 MPa.

Here, sintered filters are provided at the bottom and the top of the container to prevent carbon black from flowing out of the high-pressure container. This high-pressure vessel was fixed in an electric heating furnace, and the temperature was raised until the internal temperature of the vessel reached 280 ° C. Internal temperature is 28
After reaching 0 ° 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 stably dispersed carbon black 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 carbon black, and the mixture was shaken lightly to obtain a carbon black dispersion which was dispersed stably again. XPS for the amount of oxygen on the surface of carbon black
As shown in Table 1, the water-dispersible carbon black produced by the production method of the present invention has a larger amount of oxygen-containing groups than the untreated carbon black as shown in Table 1. Indicated.

Example 2 1.0 g of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: CF9) was weighed and placed in a high-pressure container (volume: 10 ml) made of Hastelloy. Distilled water 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 distilled water was discharged from the upper part of the container after coming into contact with the carbon black inside the container. A pressure control valve was provided at the outlet to maintain the pressure of the container at 23 MPa.

Here, a sintered filter was installed at the bottom and the top of the vessel to prevent carbon black 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. Internal temperature is 38
After reaching 0 ° C., the temperature was maintained for 30 minutes. After completion of the reaction, lower the temperature, confirm that the internal temperature has become less than 100 ° C., gradually lower the internal pressure, return the internal pressure of the container to normal pressure, confirm that the container has sufficiently cooled, and remove the contents. I took it out. At this time, the carbon black was precipitated in water and was not sufficiently hydrophilized.

0.4 g of this carbon black was added to 100 m
liter of a round-bottomed flask, and then 50 ml of an aqueous solution obtained by dissolving 0.1 g of sodium borohydride in 300 ml of a 0.1 N aqueous sodium hydroxide solution, and the reduction reaction was allowed to proceed while stirring under a nitrogen atmosphere. . After reacting for about 2 hours, 3 ml of 6N sulfuric acid was added to decompose unreacted sodium borohydride, and then the treated carbon black was filtered and washed to obtain an aqueous dispersion of carbon black stably dispersed in water. Obtained.

When the amount of oxygen on the surface of carbon black was measured in the same manner as in Example 1, it was estimated that the surface oxygen amount increased due to the high-temperature and high-pressure treatment, and that it was changed to a hydrophilic oxygen-containing group by a subsequent reduction reaction. did it. Table 1 shows the atomic composition of the carbon black surface.

(Comparative Example 1) 1.0 g of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: # 45) was weighed and charged into a Hastelloy high-pressure container (capacity: 10 ml). Distilled water 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 carbon black inside the container. A pressure control valve was installed at the outlet to maintain the pressure of the container 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 carbon black was precipitated in water, was not sufficiently hydrophilized, and a stable dispersion of the carbon black dispersion could not be obtained. The surface oxygen content was analyzed by XPS.
No increase in oxygen content was observed as shown in FIG.

Comparative Example 2 As in Example 1, 1.0 g of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: # 45)
It was weighed and put into a Hastelloy high-pressure container (volume: 10 ml). Use a high-pressure plunger pump to
% Distilled water containing 1% hydrogen peroxide from the bottom of the container
/ MPa at a flow rate of 3.5MPa / min.
a.

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 carbon black was precipitated in water, was not sufficiently hydrophilized, and a stable dispersion of the carbon black dispersion could not be obtained. The surface oxygen content was analyzed by XPS.
No increase in oxygen content was observed as shown in FIG.

[0040]

[Table 1]

[0041]

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

Claims (7)

[Claims] Claims: 1. A carbon black having a temperature of 120 ° C. or higher,
A method for producing a water-dispersible carbon black, which comprises treating with a high-temperature and high-pressure water in a liquid state or a supercritical state at a pressure of 4 MPa 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 carbon black according to claim 1, wherein the pressure is 4 ° C to 50MPa. 3. The method for producing a water-dispersible carbon black according to claim 1, wherein the high-temperature high-pressure water is water containing an oxygen donor. 4. The method for producing a water-dispersible carbon black according to claim 3, wherein the oxygen donor is at least one selected from oxygen, ozone, and hydrogen peroxide. 5. The method for producing a water-dispersible carbon black according to claim 1, wherein the carbon black treated with high-temperature and high-pressure water is further treated with a reducing agent. 6. The method for producing a water-dispersible carbon black according to claim 5, wherein the reducing agent is one or more selected from the group consisting of hydrogen, sodium borohydride, and lithium aluminum hydride. 7. An aqueous carbon black dispersion produced by the production method according to claim 1.