JPWO2011010620A1 - Powder surface treatment apparatus and powder surface treatment method - Google Patents

Abstract

A novel powder surface treatment apparatus and powder surface treatment method capable of efficiently performing powder surface treatment in a short time are provided. A powder surface treatment apparatus according to the present invention includes a container 20 for storing a liquid 30 therein, a first electrode 40 provided at a predetermined distance from the liquid surface of the liquid, and a liquid in the container. A second electrode provided so as to be electrically connected to the liquid 30 when storing 30; and a power source 50 connected to the first and second electrodes. Then, the liquid 30 is stored and the powder P as the object to be processed is placed on the liquid surface, and the first electrode and the liquid are applied by applying a voltage to the first and second electrodes. It is characterized in that it is configured to generate plasma between the liquid level. [Selection] Figure 1

Description

  The present invention relates to a powder surface treatment apparatus and a powder surface treatment method for increasing the hydrophilicity of a powder.

  Conventionally, as a method for imparting hydrophilicity to a powder to improve wettability and to disperse it in a solvent, a method of performing surface treatment by irradiating the powder with plasma is known (Patent Document 1). ~ 4 etc.). For example, Patent Document 1 describes a surface treatment method using plasma capable of continuously plasma-treating a large amount of powder.

  On the other hand, when the surface treatment with plasma is not performed, the powder tends to be less dispersible as the particle diameter becomes finer. Used to increase dispersibility. For example, Patent Document 5 describes that a surfactant is used to mix metal powder and resin.

JP-A-6-365 JP-A-1-193332 JP-A-6-228739 JP 2003-19434 A JP 2008-108539 A

  However, all of the conventional methods for performing so-called surface treatment by subjecting powder to plasma treatment require complicated equipment, and thus cannot be manufactured in large quantities at low cost.

  On the other hand, the conventional method of kneading or dispersing powder in a resin or solvent requires various additives such as a surfactant in order to obtain a uniform dispersion. However, the additive reduces the purity of the powder and causes the original functions and characteristics of the powder to deteriorate.

  The present invention has been made in view of the above, and an object of the present invention is to provide a novel powder surface treatment apparatus and powder surface treatment method capable of efficiently performing powder surface treatment in a short time. To do.

The powder surface treatment apparatus according to the present invention stores the liquid 30 in the container, the container 20 that stores the liquid 30 therein, the first electrode 40 provided at a predetermined distance from the liquid surface of the liquid, and the container. A second electrode provided to be electrically connected to the liquid 30 and a power source 50 connected to the first and second electrodes.
The liquid 30 is stored and the powder P as the object to be processed is placed on the liquid surface, and a voltage is applied to the first and second electrodes, whereby the first electrode and the liquid It is characterized by being configured to generate plasma between the liquid surface.

  According to the above powder surface treatment apparatus, the affinity of the liquid is enhanced by the surface modification of the powder placed on the liquid surface by the action of the plasma generated on the liquid surface (water plasma), A dispersion using a liquid as a dispersion solvent can be produced. This dispersion can maintain the dispersed state of the powder for a long period of time by physical action, and does not contain impurities such as a surfactant.

  The powder surface treatment apparatus may be configured such that a plurality of the first electrodes 40 and a power source 50 are provided and electrically connected in parallel to the liquid 30. With this configuration, the plasma generation range is expanded, so that a wide range of powders can be irradiated with plasma simultaneously. As a result, it is possible to surface-treat more powder with one discharge.

  The powder processing apparatus may further include an inlet 70 and an outlet 80 for the liquid 30 and an inlet 90 for the powder P. According to this configuration, the liquid 30 is introduced from the introduction port 70 of the liquid 30 and the powder P is introduced from the powder introduction port 90 before the discharge treatment, and the dispersion obtained by the discharge is discharged after the discharge treatment. Since it can discharge | emit from the exit 80, a lot of powder surface treatment can be performed continuously.

  The voltage of the power supply 50 applied to the first electrode 40 is preferably 1 [kV / mm] or more per electrode interval. This is because the discharge start voltage can vary under various conditions, but if such a voltage is applied, a sustained plasma discharge is possible even in an air atmosphere at atmospheric pressure.

  In the powder surface treatment apparatus, the first electrode 40 is preferably made of carbon or a transition metal element. This is to prevent the constituent elements of the first electrode from being dissolved or mixed in the liquid 30 due to a high temperature due to discharge.

  The powder surface treatment method according to the present invention includes a step of introducing a powder as an object to be treated onto a liquid as a dispersion solvent, a step of generating a water plasma on the liquid surface of the liquid, and the water plasma. Generating a predetermined period of time.

The liquid 30 is preferably a hydrophilic liquid. The powder P to be treated includes, for example, carbon-based powders such as carbon nanotubes, graphite carbon, fullerene (C ₆₀ ), silicon-based powders such as silicon dioxide or trisilicon tetranitride, silver, tungsten, It is a metal-based powder such as titanium or titanium oxide, and the size is not limited.

  The powder surface treatment apparatus according to the present invention is capable of making a powder compatible with a liquid in a short time without using a surfactant, so that a paint containing carbon powder or a hybrid material mixed with graphite carbon is used. Cost savings can be achieved in manufacturing. Furthermore, since the purity of the material lost by the surfactant can be maintained, it is effective in maintaining the characteristics. In addition, there is an effect that quality can be improved, for example, graphite carbon which is a positive electrode material or a negative electrode material of a battery can be easily aggregated and molded without a binder.

The conceptual diagram explaining the basic principle of the powder surface treatment apparatus of 1st Embodiment The schematic diagram which shows the mode of the plasma discharge by the powder surface treatment apparatus of 1st Embodiment (a) During discharge (b) After discharge The photograph which image | photographed the mode before and behind plasma discharge by the powder surface treatment apparatus of 1st Embodiment (a) Immediately before discharge start (b) After discharge The conceptual diagram for demonstrating the powder surface treatment apparatus of 2nd Embodiment The schematic diagram which shows the mode of the plasma discharge by the powder surface treatment apparatus of 2nd Embodiment. Sectional view showing electrode structure of lithium ion battery (A) Schematic diagram illustrating how graphite resin powder is added to graphite carbon for molding (a) Schematic diagram showing graphite carbon powder G (b) Graphite carbon powder G and molecules of fluorinated resin Schematic diagram showing the state immediately after F is mixed (c) Schematic diagram showing the state after molding by mixing graphite carbon powder G and fluorinated resin molecule F Schematic diagram illustrating a state in which the surface treatment of the present invention is performed on graphite carbon without adding a binder. (A) Schematic diagram showing graphite carbon powder G (b) Graphite carbon powder G (C) The schematic diagram which shows the state which shape | molded the graphite carbon without a binder immediately after implementing the powder surface treatment method of this invention

  Embodiments of a plasma surface treatment apparatus and a powder surface treatment method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not construed as being limited to the embodiments. Moreover, the same code | symbol is attached | subjected to the same or equivalent member, and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a conceptual diagram for explaining the basic principle of a powder surface treatment apparatus of the present invention as a first embodiment of the present invention. The powder surface treatment apparatus 100 stores the liquid 30 inside the container 20 and is provided with a first electrode 40 spaced apart from the liquid surface by a predetermined distance (that is, via air or the like). The first electrode 40 is connected to the positive electrode of the DC power supply 50. The second electrode 60 has one end connected to the negative electrode of the DC power supply 50 and the other end electrically connected to the liquid 30 through an electric wire. Then, the powder P is placed on the liquid surface of the liquid 30.

Examples of the powder P include carbon-based powders such as carbon nanotubes, graphite carbon, and fullerene (C ₆₀ ), silicon-based powders such as silicon dioxide or trisilicon tetranitride, silver, tungsten, titanium, and titanium oxide. It is a metal-based powder and does not have any size. For example, the particle size of the powder is about 1 nm to 100 μm.

On the other hand, the liquid 30 is preferably a hydrophilic liquid such as water (H ₂ O) or an alcohol-based aqueous solution (alcohol). In addition, when using alcohol-type aqueous solution for a liquid, since there exists a danger of igniting alcohol by discharge, the gas atmosphere containing oxygen like air is not preferable. In such a case, it is preferable to perform discharge in an atmosphere that does not contain oxygen gas, such as an argon gas atmosphere or a nitrogen gas atmosphere.

  Although the powder P is charged from above the liquid 30 by a powder charging means (not shown), the powder P does not mix with the liquid 30 immediately after the charging because the powder P is not hydrophilic. Therefore, the liquid is separated above the liquid surface or remains floating on the liquid surface due to surface tension.

  Next, a high voltage is applied to the DC power supply 50 to generate plasma between the first electrode 40 and the liquid surface. As described above, air or the like is interposed between the first electrode 40 and the liquid surface of the liquid 30, but when the voltage applied by the DC power supply 50 is increased, the dielectric breakdown voltage is finally reached and discharge is started. The plasma discharge start condition affects the gas atmosphere, pressure, humidity, etc., and there are strict calculation formulas, but approximately 1 kV (that is, about 3 kV when 3 mm apart) is used as a guide for the discharge start voltage For example, when a power source having an applied voltage of 0.1 kV to 30 kV can be prepared, the distance between the first spacing electrode and the liquid surface may be approximately 0.1 mm to 30 mm. However, what is necessary is just to implement by the voltage and distance required in order to start discharge, and the numerical value itself does not have so important meaning.

  The first electrode 40 connected to the positive electrode is, for example, a rod-shaped (needle-shaped) conductive member as shown in FIG. 1, and the material thereof is preferably composed of, for example, carbon or a transition metal. This is to prevent the constituent elements of the first electrode from being dissolved or mixed in the liquid 30 due to a high temperature due to discharge. However, if the first electrode and the powder are made of the same kind of metal, there may be cases where the influence of the first electrode and the powder is reduced even if it is dissolved or mixed. For example, the first electrode is a carbon electrode and the powder that is the object to be processed is also a carbon-based powder. As described above, there is a case where selecting a combination of materials composed of the same kind or the same kind of elements of the material of the first electrode and the material of the powder may bring merit. On the other hand, the type of the second electrode 60 connected to the negative electrode is not particularly limited because it is not exposed to discharge. That is, the second electrode 60 may be any material as long as it is electrically connected to the liquid 30, and the type of the material is not limited. During the discharge, a plasma discharge is generated in the gap between the first electrode (positive electrode) and the liquid surface of the liquid 30. In addition, in this specification, plasma discharge that discharges from a rod-shaped electrode (positive electrode) to a liquid surface of a wide area is called “water plasma”.

  Then, when water plasma is generated and the discharge state is maintained for a certain period of time, the powder P separated from the liquid 30 is hydrophilicly mixed and dispersed in the liquid 30. This phenomenon is considered to be because the hydrophobic group terminating the surface of the powder is removed by the energy of the plasma and immediately after that, the hydrophilicity is imparted by contacting with the liquid. This dispersed state is a physical state obtained without additives such as a surfactant, and lasts for a very long time. That is, the liquid 30 not only functions as a counter electrode with respect to the first electrode (positive electrode), but also functions as a dispersion solvent for the powder P.

  FIG. 2A is a schematic diagram showing a state of the powder surface treatment apparatus 100 during plasma discharge. D in the figure schematically shows a discharge generation region by water plasma. FIG. 2B is a schematic diagram showing a state in which the powder is dispersed in the liquid after the plasma discharge.

  As described above, according to the powder surface treatment apparatus of the first embodiment, it is possible to efficiently impart hydrophilicity by performing a surface treatment on the powder as the object to be treated. In addition, according to the water plasma of this device, the plasma discharge generation region is limited to the liquid surface where the object to be processed (powder) floats and its vicinity, so that the power source is used efficiently and the power consumption is greatly reduced. Can do. In the first embodiment, a DC power source is used as the power source. However, a configuration capable of generating water plasma and irradiating the powder is important, and the type of the power source is not limited. For example, an AC power supply may be used instead of the DC power supply. In this case, it goes without saying that a matching circuit and other additional equipment are required as necessary.

  The powder dispersion obtained by the powder surface treatment method using the powder surface treatment apparatus of the first embodiment is basically composed of water and powder and does not contain additives such as surfactants. Therefore, there is an advantage that there are few factors that deteriorate the characteristics of the material such as conductivity.

  Further, this apparatus can be carried out in an air atmosphere under atmospheric pressure, and if the liquid is a water-soluble liquid, there is no problem even if it contains some impurities such as tap water. The apparatus of this embodiment is extremely easy to implement, for example, if it has a high-voltage power supply and electrodes that generate tens of kV at most, it does not require any special apparatus and can be carried out under atmospheric pressure in an air atmosphere. For this reason, if it implements in large quantities at a factory etc., a manufacturing cost can be reduced extremely. In addition, the continuous mass processing in consideration of implementation in the factory will be described in detail in the second embodiment.

-Experimental example-
As a basic experiment for confirming the effect of the present invention, an experiment was performed under the following conditions. First, a beaker having a diameter of about 5 cm is used as the container 10, about 100 mL of room temperature tap water is placed therein, the tip of the first electrode 40 is placed at a position about 2.5 mm away from the water surface, and the positive electrode of the DC power supply 50 Connected to. On the other hand, the second electrode was connected to the negative electrode of the DC power source 50, and the other end was connected to the liquid in the beaker. After putting graphite carbon having a mass of about 2 to 3 g, a DC voltage of about 2.5 kV was applied to start plasma discharge. After the discharge was continued for about 1 minute, the discharge was stopped. The atmosphere during discharge was an atmospheric air atmosphere.

  FIG. 3A is a photograph of the beaker immediately before the start of discharge, and FIG. 3B is a photograph of the beaker after discharge. The graphite carbon powder separated above the liquid level before the start of discharge was uniformly mixed and dispersed after the start of discharge.

(Second Embodiment)
FIG. 4 is a conceptual diagram for explaining a practical application example of the powder surface treatment apparatus as the second embodiment of the present invention. The powder surface treatment apparatus 200 stores the liquid 30 inside the container 20, and is provided with first electrodes 40a to 40c separated from the liquid surface by a predetermined distance (that is, via air or the like). The first electrodes 40a to 40c are connected to the positive electrodes of the DC power sources 50a to 50c, respectively. The second electrode 60 has one end connected to the negative electrode of the DC power supply 50 and the other end electrically connected to the liquid 30 through an electric wire. Then, the powder P is placed on the liquid surface of the liquid 30.

  That is, in the second embodiment, since the vessel 10 is enlarged and a plurality of electrodes on the positive electrode side of plasma discharge are provided, the generation range of the water plasma is expanded. It is configured to be able to. In order to continuously perform the powder surface treatment, a liquid inlet 70 and a discharge outlet 80 and a powder inlet 90 are provided. Further, the positions of the first electrodes 40a to 40c with respect to the liquid level are configured so that the relative distance from the liquid level can be finely adjusted by a moving means (not shown). This is because it is necessary to adjust the electrode interval of discharge in order to generate water plasma continuously and stably. The introduction of the liquid before the plasma treatment, the discharge of the dispersion liquid after the plasma treatment and the introduction of the powder into the liquid are controlled by a control means (not shown). It becomes possible. Since other implementation conditions and the like are as described above, the description of the first embodiment is incorporated.

  FIG. 5 is a schematic view showing a state of the powder surface treatment apparatus 200 during plasma discharge. After the plasma discharge, the powder P is uniformly dispersed in the liquid 30 as in FIG.

  As shown in this figure, according to the powder surface treatment apparatus according to the second embodiment, the plasma discharge range is widened by providing a plurality of plasma discharge electrodes, and a large amount of powder can be applied to the powder surface at once. Can be processed.

  As described above, according to the powder surface treatment apparatus of the second embodiment, it is possible to efficiently impart hydrophilicity by subjecting the powder as the object to be treated to surface treatment. In addition, according to the water plasma of this device, the plasma discharge generation region is limited to the liquid surface where the object to be processed (powder) floats and its vicinity, so that the power source is used efficiently and the power consumption is greatly reduced. Can do.

(Third embodiment)
FIG. 6 is a cross-sectional view showing an example of an electrode structure of a lithium ion battery. The negative electrode terminal 1 is connected to the positive electrode material 4 through the negative electrode 2 and the separator 3, and is connected to the positive electrode terminal 7 through the current collector 6. A gasket 5 is provided around the battery. For the electrode material 5 used in such batteries as lithium ion batteries, fluorinated graphite containing graphite carbon as a main component is used. However, since graphite carbon is a difficult-to-mold material, a so-called fluorinated resin containing fluorine is kneaded to facilitate molding.

  When molding is performed by aggregating graphite carbons, polyvinylidene fluoride having no conductivity and water-dispersed styrene-butadiene rubber are used as a binder. Although these are additives for facilitating molding, they are impurities that impede conductivity for electrode materials and are essentially unnecessary.

  FIG. 7A is a schematic diagram showing the graphite carbon powder G, and FIG. 7B is a schematic diagram showing the state immediately after the graphite carbon powder G and the fluorinated resin molecules F are mixed. FIG. 7C is a schematic diagram showing a state after the graphite carbon powder G and the fluorinated resin molecules F are mixed and molded.

  As shown in this figure, a conventional molded body of graphite carbon powder G as an electrode material is added with a substance that inhibits conduction, such as a molecule F of a fluorinated resin, as a binder. The actual situation includes various problems caused by mixing fluorinated resins, such as an increase, an increase in production cost, and an increase in weight.

  However, surface treatment of graphite carbon powder by the powder surface treatment method of the present invention activates the surface, and as a result of the graphite carbon attracting each other, it contains impurities that impede conductivity after molding. Not a pure carbon material.

  FIG. 8A is a schematic diagram showing the graphite carbon powder G, and FIG. 8B is a diagram immediately after the powder surface treatment method of the present invention is performed on the graphite carbon powder G of FIG. FIG. 8C is a schematic diagram showing a state in which the graphite carbon of FIG. 8B is molded without a binder.

  As described above, by applying the powder surface treatment method of the present invention to graphite carbon and using it as a battery electrode material, it becomes possible to mold without a binder, contributing to improvement of electrical characteristics, production cost and weight reduction. Is expected to do.

(Other embodiments)
The following can be considered as application fields of various powders to which the powder surface treatment method of the present invention is applied.
(1) Application to water-soluble ink Water-soluble ink for drawing electrical wiring with carbon nanotubes, etc., needs to dissolve carbon or organic powder as a raw material in water-soluble liquid, but the production efficiency No good technology has been established. However, according to the powder surface treatment method of the present invention, it is expected to improve the production efficiency and lower the production cost.
(2) Application to drug discovery development Conventionally, fullerenes have been dissolved in aqueous solutions using laser technology for the development of new drug discovery. A big wall was standing. However, according to the powder surface treatment method of the present invention, it is expected to improve the production efficiency and lower the production cost.
(3) Application to sliding material, etc. Heat resistance temperature and friction coefficient are improved by mixing graphite carbon into resin, and it is used as a sliding material. In the current sliding material, a surfactant is mixed in order to improve dispersibility. However, the addition of the surfactant also causes a decrease in performance and an increase in manufacturing cost.
(4) Application to other technologies Various powders have already been put into practical use in various fields such as foundation (TiO ₂ ), which is one of cosmetics, and slurries used in polishing processes of semiconductor integrated circuit devices. Yes. Some of these are mixed with various additives in order to improve dispersibility or for other purposes. However, by using a dispersion that retains dispersibility over a long period of time due to the physical action obtained by applying the powder surface treatment method of the present invention, there is a possibility that improvement in characteristics and reduction in manufacturing cost can be realized. large.

  The present invention is expected to be applied to manufacturing processes of various products using powder, and the industrial applicability of the present invention is extremely large.

100,200 Powder surface treatment apparatus 20 Container 30 Liquid 40 First electrode (positive electrode)
50 DC power supply 60 Second electrode 70 Liquid inlet 80 Ejector 90 Powder inlet

Claims (8)

A container for storing liquid therein, a first electrode provided at a predetermined distance from the liquid surface of the liquid, and a first electrode provided to be electrically connected to the liquid when the liquid is stored in the container Two electrodes, and a power source connected to the first and second electrodes,
The liquid is stored, and the powder P as an object to be processed is placed on the liquid surface, and a voltage is applied to the first and second electrodes, whereby the first electrode and the liquid liquid A powder surface treatment apparatus configured to generate plasma between surfaces.   The powder surface treatment apparatus according to claim 1, wherein a plurality of the first electrodes and a power source are provided and are electrically connected in parallel to the liquid.   The powder surface treatment apparatus according to claim 2, further comprising an inlet and an outlet for the liquid and an inlet for the powder.   4. The powder surface treatment apparatus according to claim 1, wherein a voltage of a power source applied to the first electrode is 1 [kV / mm] or more per electrode interval. 5.   5. The powder surface treatment apparatus according to claim 1, wherein the material of the first electrode is made of carbon or a transition metal element. 6. A powder surface treatment method for modifying a powder surface to disperse the powder in a liquid,
A step of introducing a powder as an object to be treated onto a liquid as a dispersion solvent; a step of generating a water plasma on a liquid surface of the liquid; and a step of maintaining the generation of the water plasma for a predetermined time. A powder surface treatment method comprising:   The powder surface treatment method according to claim 6, wherein the liquid is a hydrophilic liquid. The powders to be treated include carbon-based powders such as carbon nanotubes, graphite carbon, fullerene (C ₆₀ ), silicon-based powders such as silicon dioxide or trisilicon tetranitride, silver, tungsten, titanium, and titanium oxide. The powder surface treatment apparatus according to claim 6 or 7, comprising any one or more of metal-based powders such as products.

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