JP3297881B2 - Ultrafine particle surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an atmospheric pressure plasma treatment method for the surface of fine ultrafine particles of the order of (t), and to continuously process the surface of ultrafine fine particles of the order of nm (nanometer). The present invention relates to a method for surface treatment of ultrafine particles subjected to atmospheric pressure plasma treatment.

[0002]

2. Description of the Related Art At present, powder production technology has remarkably progressed, and many fine powders having a particle diameter of nm (nanometer) called ultrafine particles have been produced. These ultrafine particles are used in various fields. For example, it is possible to improve the output and frequency characteristics by converting cobalt-iron necessary for high-density magnetic tapes and video tapes of electronic technology, particularly computers, into ultrafine particles,
Conventionally, ultrafine particles such as alumina oxide and titanium oxide have been frequently used for low-temperature processing of ceramics and sintered materials.

[0003] These ultrafine particles have a strong surface activity,
Some types have extremely high hydrophilicity, but conversely, secondary aggregation is apt to occur, and it is difficult to obtain good dispersion. And, these fine particles are not arbitrarily hydrophilic or lipophilic.

On the other hand, powders such as pigments and dyes are subjected to an atmospheric pressure glow discharge plasma treatment to arbitrarily increase the hydrophilicity or hydrophobicity of the surface to improve the wettability, or to improve the aqueous or oily properties. It is easy to disperse in a solvent.

In connection with the technique of the atmospheric pressure glow discharge plasma treatment, the present inventor has first made it possible to continuously form a powder together with a mixture of an inert gas and a ketone at atmospheric pressure during plasma excitation. A method of making the surface of the powder hydrophilic or hydrophobic by allowing the powder to pass therethrough (Japanese Patent Laid-Open No. 4-1 / 1991).
No. 35638). However, the apparatus specifically disclosed for carrying out this method has an electrode attached to the outside of the cylinder, and the inside of the cylinder is mixed with a powder and an insoluble gas for generating an atmospheric pressure plasma such as helium, argon or the like. Is passed through. Therefore, the plasma processing time is extremely short because it is proportional to the gas flow rate, so that the plasma cannot be completely applied to the powder, and a large amount of plasma must be processed in a limited space inside the cylinder. However, there is a disadvantage that the powder cannot be processed.

Accordingly, the present inventor has invented a method which improves the above points (Japanese Patent Application No. 4-163071). The method includes lining a dielectric on the outside of the metal inner cylinder and / or the inside of the coaxial metal outer cylinder, and coaxially supporting these inner and outer cylinders. A constant gap is provided between them, these inner and outer cylinders are tilted and rotatably installed, and a voltage is applied between the inner and outer cylinders to apply a voltage between the inner and outer cylinders to generate an atmospheric pressure plasma in the gap between them. A plasma processing method for powder is characterized in that the powder to be processed is moved in the gap to perform plasma processing continuously.
According to this method, a large amount of powder can be continuously subjected to plasma processing.

[0007] As described above, recently, ultrafine particles having a fine particle size have been obtained, and these ultrafine particles have been regarded as important in various fields. Is a very important issue. However, when the plasma processing method of the ultrafine particle surface is performed by the above-described plasma processing method, the ultrafine particles cause a problem such as scattering and do not move in a fixed direction between the inner and outer cylinders and are not necessarily suitable for the fine particle surface processing method. It is hard to say that.

[0008]

The present inventor has developed a plasma processing method suitable for the above-mentioned ultrafine particle surface, whereby the ultrafine particles having a particle size of 0.1 μm or less and a nanometer order are obtained. As a result of various studies to impart hydrophilicity and lipophilicity arbitrarily, the present invention has been completed, and the object of the present invention is to make ultrafine particles extremely suspended when suspended in oil, organic solvent, resin, or water. It is an object of the present invention to provide an atmospheric pressure plasma treatment method for ultrafine particles for good dispersion.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is that a plasma generating electrode is placed in a closed container having a gas inlet and a gas outlet, and a container made of a dielectric is placed on one of the electrodes. Then, the container is filled with ultrafine particles, the inside of the closed container is set to an atmospheric pressure plasma generation atmosphere, and the atmospheric pressure plasma is generated between the two electrodes to process the surface of the fine particles. In addition, a raw material supply port is provided at an upper portion near one end of a sealed container having a gas inlet and a gas outlet, and a raw material outlet is provided at a lower portion near the other end, so that the container can be vibrated. And, the raw material supply port is installed at a slightly higher inclination, the powder to be treated of the ultrafine particles is supplied into the container from the raw material supply port and moved, and the plasma generating electrode is disposed on the outer surface of the container, Atmospheric pressure plasma generated gas from gas inlet Introduced to the container as atmospheric pressure plasma generating atmosphere, thereby generating an atmospheric pressure plasma between the electrodes, an atmospheric pressure plasma treatment method, which comprises treating the continuous fine particle surface.

That is, according to the present invention, when the surface of ultra-fine particles of the order of nm is subjected to atmospheric pressure plasma treatment, the ultra-fine particles are filled in a container made of a dielectric material and are continuously treated. Then, the container storing the ultrafine particles is subjected to the atmospheric pressure plasma treatment by moving the ultrafine particles in the container while tilting and vibrating.

Further, the present invention will be specifically described. The ultrafine particles in the present invention have an order of nanometer in particle diameter.
It refers to a fine powder such as, the type of ultra-fine particles may be any one that has been subjected to conventional plasma treatment, for example, pigments such as titanium oxide and aluminum oxide, dyes, ceramics, It is applied to various kinds of ultrafine particles such as plastic and glass.

FIG. 1 shows an example of an apparatus used in the present invention.
Shown in In FIG. 1, electrodes 4 and 5 are arranged in a container 1 having a gas inlet 2 and a gas outlet 3 so as to keep a gap vertically. This gap varies depending on the type of gas to be introduced, but is about 5 to 40 mm, usually about 6 to 15 mm.
At least one of these electrodes is previously applied with a ceramic sprayed or glass layer as a dielectric over the entire surface. Then, the glass plate 6 is placed on the lower electrode 5. As for the dimensions of the glass plate, the low area is the maximum and the same area as the electrodes, and the height is about the same as the gap between the electrodes. Ultrafine particles of the powder to be treated are put in the dish.

FIG. 2 shows an apparatus for performing continuous operation. In FIG. 2, a raw material supply port 7 is provided at an upper portion near one end of a closed container 1 having a gas inlet 2 and a gas outlet 3, and a raw material outlet 8 is provided at a lower portion near the other end. This container 1
Is installed with an inclination of about 10 degrees to 20 degrees and is capable of vibrating, so that the raw material in the container can be moved from one side to the other side. The electrodes 4 and 5 are arranged on the outer surface of the container. The raw material is supplied from a hopper through a raw material supply port 7 into the container. When the container is installed at an angle and vibrates, the raw material in the container moves and moves toward the raw material discharge port 8. A mixed gas of argon and helium is introduced from the gas inlet port 2 and the gas outlet port 3 of the container to make the inside of the container an atmospheric pressure plasma generating atmosphere. 5000 Hz, 2500 V between both electrodes 4 and 5
Is applied, a glow discharge occurs and the surface of the ultrafine particles is subjected to atmospheric pressure plasma treatment. The treated ultrafine particles move by vibration and fall into the storage tank 9 from the raw material discharge port.
In addition, when this apparatus is used, ultrafine particles are continuously processed, and work can be performed by introducing a very small amount of a gas for plasma generation, and there is no need to replace the entire container with gas as in the conventional case.

The conditions for generating the atmospheric pressure glow discharge plasma are the same as those in the conventional method, and the frequency is 200 Hz to 1,000 in an atmosphere of an inert gas such as helium or argon or a mixed gas obtained by mixing these with ketones. 000H
z, a voltage is applied to generate an electric field of 2000 V to 7000 V to generate a glow discharge plasma. In order to impart lipophilicity to the ultrafine particles, a hydrocarbon is present together with an inert gas for generating atmospheric pressure plasma. Hydrocarbons to be provided to impart lipophilicity include aliphatic hydrocarbons such as propane, butane, pentane, hexane, trimethylpentane, and trimethylolpropane, and their substituted products, and unsaturated hydrocarbons such as ethylene, butene, pentene and hexene. Aliphatic hydrocarbons and their substituted products, aromatic hydrocarbons such as benzene, toluene, xylene, styrene, ethylbenzene and cumene and their substituted products, alicyclic hydrocarbons such as cyclopentane, cyclohexane and cyclohexene and their substituted products It is.

Among the hydrocarbons, those having a low boiling point, such as n-butane, may be mixed as they are from the cylinder, but those of liquids, such as hexane and isooctane,
Those having a vapor pressure at room temperature may be passed through the solution as it is and mixed using partial pressure, and those having a high boiling point such as trimethylolpropane may be mixed by heating. The plasma treatment time for imparting lipophilicity is usually from 2 seconds to 10 minutes, and the longer the treatment time, the greater the thickness of the polymer film and the greater the lipophilic effect.

Next, in order to impart hydrophilicity, the above-described reactor is used, and ultrafine particles are positioned between the upper and lower electrodes.
For example, a mixed gas of 70 parts of argon gas and 30 parts of helium gas may be introduced to replace the air, and then a glow discharge may be generated. In the case of imparting hydrophilicity, the effect is hardly changed even if some air remains.

Although argon gas is very effective for hydrophilicity, glow discharge does not occur with argon gas alone, so helium is mixed or a small amount of ketone is mixed to discharge. Since helium is an expensive gas, it is preferable to use 20 parts of helium for 80 parts of argon gas and 50 parts of helium for 50 parts of argon. When mixing ketones,
The proportion of ketone in argon is preferably 3 ppm to 10 ppm, and if it is 10 ppm or more, an organic thin film is formed on the surface, so that the effect of hydrophilicity is slightly reduced. The role of the ketone in this case is to mix to enable a glow discharge in argon, and the limit of the ketone that causes the discharge is 2-3 pp.
m, the most preferable is 3 to 5 ppm.

As the ketone to be used, acetone, methyl ethyl ketone, methyl isobutyl ketone and the like can be used, but acetone and methyl ethyl ketone having a low boiling point have a high vapor pressure and are easily mixed. Next, the present invention will be specifically described with reference to examples.

[0019]

【Example】

Example 1 In an atmospheric pressure plasma processing apparatus having an internal volume of 10 liters as shown in FIG. 1, ultrafine titanium oxide powder was placed flat in the gap between upper and lower electrodes 1 and 2 which had been subjected to ceramic spraying as a dielectric beforehand. Place the glass dish,
60 parts of argon, 39.5 parts of helium from gas inlet, n
-A mixture of 0.5 parts of butane is introduced at a flow rate of 3 L / min to replace the air inside the apparatus. When the replacement is completed, the gas flow rate is reduced to 100 cc / min and 3 KH is applied between the upper and lower electrodes.
z, a high frequency voltage of 3800 V is applied. A red-purple glow discharge occurs and is excited by plasma, and hydrocarbons such as n-butane immediately undergo radical polymerization to form an extremely thin lipophilic film on the surface of the powder. Table 1 shows a comparison between untreated and treated. This is a measurement in which toluene is put in a test tube, a certain amount of powder is put therein, shaken and allowed to stand, and the time until it becomes transparent is measured. The longer the suspension time, the better the dispersion.

[0020]

[Table 1]

Example 2 10 g of ultrafine titanium oxide particles were placed in a glass dish (wall height: 6 mm), and the surface was leveled so as to be flat. It is installed between the electrodes of an atmospheric pressure plasma reactor having an internal volume of 10 liters in the same manner as described above, and a mixed gas of 70 parts of argon and 30 parts of helium is introduced to replace air therein. The flow rate is 2 l / min, and the replacement is almost completed in about 7 minutes. Therefore, a voltage of 3 kHz and 3000 V is applied between the electrodes. Since blue-violet glow discharge occurs and plasma is excited, the treatment is performed for 3 minutes. 20 cc of distilled water is put in a test tube, 0.2 g of the treated powder is put in the test tube, and shaken and allowed to stand. Also,
Unprocessed ones are similarly compared. Table 2 shows the results.

Example 3 10 g of ultrafine titanium oxide particles were placed in a glass dish and treated in the same manner as in Example 1 using the same apparatus. However, the inflowing gas was 99.9 parts of argon and 0.1 part of acetone.
One part of the gas mixture was used. When the amount of acetone is converted into ppm, it is 2.6 ppm. 3KHz between electrodes, 37
When a voltage of 00 V is applied, a blue-white glow discharge occurs. In this state, a sample treated for 5 minutes was compared with an untreated product. Table 2 shows the results.

Example 4 5 g of ultrafine aluminum oxide was placed in a glass dish and subjected to lipophilic treatment using the same apparatus as in Example 1. 60 parts of argon as a mixed gas
A mixture of 5 parts and 0.5 part of xylene was used. The mixing method of xylene was such that the above-mentioned argon gas was blown into xylene at room temperature to saturate and mix xylene. 5KH between electrodes
z, a voltage of 2900 V was applied. A red-purple glow discharge occurred, in which plasma treatment was performed for 3 minutes. Table 2 shows the result of comparison with the untreated product.

Example 5 5 g of ultrafine aluminum oxide was placed in a glass dish and placed between the electrodes in exactly the same manner as in Example 1. Next, as a mixed gas, 70 parts of argon and 29.7 parts of helium are mixed with 0.3 part of styrene to be replaced with air. Since styrene has a low boiling point of 150 ° C. and a low vapor pressure, it was heated to 100 ° C. to increase the vapor pressure and helium was passed through the liquid surface to introduce the vapor. When a voltage of 1 KHz and a voltage of 3200 V are applied, glow occurs.
Discharge occurs and a thin styrene polymer film is formed on the surface of the powder. This powder is very hydrophobic and lipophilic. Next, the result of comparison with the untreated product is shown in Table 2.

[0025]

[Table 2]

[0026]

As described above, according to the present invention, ultrafine particles can be subjected to surface treatment without causing problems such as scattering during plasma processing. The plasma treatment can be performed without operating the.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus for performing a method of the present invention.

FIG. 2 is an explanatory view of an apparatus for carrying out the method of the present invention continuously.

FIG. 3 is a sectional view of the device shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Gas inlet 3 Gas outlet 4 Upper electrode 5 Lower electrode 6 Glass tray 7 Raw material supply port 8 Raw material discharge port 9 Storage tank

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 19/00-19/34

Claims (2)

(57) [Claims] 1. A placing one container made of a dielectric material on top of the plasma generating electrode in a sealed container and placed the electrode having the inlet and outlet of the gas, nanometer O within the vessel
An atmospheric pressure plasma generating atmosphere in a closed vessel, and an atmospheric pressure plasma is generated between both electrodes to treat the surface of the ultrafine particles. 2. A closed container having a gas inlet and a gas outlet, a raw material supply port is provided at an upper portion near one end and a raw material discharge port is provided near the other end, and the container can be vibrated. and,
The raw material supply port is installed at a slightly higher inclination, and
Along with supplying and moving the powder to be treated of nanometer-order ultrafine particles into the container, an electrode for plasma generation is arranged on the outer surface of the container, and an atmospheric pressure plasma generating gas is introduced from the gas introduction port into the container. was atmospheric pressure generated atmosphere, by generating an atmospheric pressure plasma between the electrodes, an atmospheric pressure plasma treatment method, which comprises treating the continuously the ultrasonic <br/> fine particle surface.