JP2705667B2 - Method and apparatus for granulating tantalum powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for granulating tantalum powder, and more particularly to a method for granulating tantalum powder for a capacitor "mixing and granulating tantalum powder and solid organic powder" and a method for granulating tantalum powder. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, tantalum powder is compression-molded into pellets, and after the pellets have been molded, they are placed in a high vacuum for 1400 hours.
A porous sintered body is sintered at a high temperature of not less than ℃ to form a porous sintered body, which is subjected to a chemical conversion treatment to form an oxide film, and the obtained tantalum sintered body is used as a “capacitor-anode body”.

[0003] The tantalum sintered body for a capacitor is preferably one in which each particle has a complicated outer shape with a lot of irregularities and presents an extremely porous sea surface. Preferably, the working surface area is much larger than it looks.

By the way, tantalum powder is pelletized,
In order to mold this, the following conditions are required for the powder and the compact. Good flowability of tantalum powder. [Because it is necessary to make the amount of tantalum powder filled in a die constant to improve the capacitance accuracy as a capacitor. ] The lubricity of the tantalum powder is good. [Because it is necessary to prevent the mold from being damaged by the tantalum powder biting into the die and punch. The irregularities are formed on the surface of the compact made of tantalum powder. [To ensure that the tantalum sintered body obtained in the subsequent sintering step improves the electrical characteristics (Tan δ) as a capacitor. ]

Conventionally, as means for satisfying the above conditions (1), a method of (1) supplying an organic powder to a tantalum powder and mixing both powders using, for example, a V-shaped mixer (hereinafter referred to as "conventional method 1") (2) a method in which an organic powder is not mixed, wherein a binder is supplied to the tantalum powder to perform granulation;
(Hereinafter referred to as “conventional method 2”).

The above-mentioned conventional method 1 is a method in which a solid organic powder is mixed with a tantalum powder in order to improve fluidity (flowability) at the time of molding the tantalum powder and obtain a porous molded body. is there. This conventional method 1 will be described with reference to FIG. FIG. 3 is a diagram showing a tantalum powder mixing apparatus (V-shaped mixer) used in the conventional method 1.

Conventional method 1 is a method using, for example, a V-shaped mixer shown in FIG. 3, and this V-shaped mixer comprises a V-shaped container 50 having a cylinder joined at about 90 degrees, The shafts 51 are welded horizontally from the left and right side surfaces of the V-shaped container 50, the left and right ends of each shaft 51 are fitted into a bearing 52, and the left end of the shaft 51 is directly connected to a motor 53. -Ta 53
This makes the V-shaped container 50 rotatable.
Then, after the tantalum powder and the organic powder are supplied into the V-shaped container 50, the V-shaped container 50 is rotated to mix the two powders.

On the other hand, in the conventional method 2, i) a tantalum powder is produced by supplying an organic binder such as PVA (polyvinyl alcohol) to the tantalum powder using a granulator such as a spray dryer. Ii) In a method of granulating tantalum powder using a fluidized bed granulator, first, an inorganic binder (water, phosphoric acid, etc.) is used.
Is sprayed and granulated, and then an organic binder is sprayed and granulated (see JP-A-5-65502).

[0009]

In the conventional method 1 (method of supplying an organic powder to a tantalum powder), when the obtained mixed powder is subjected to compression molding, the difference in specific gravity between the tantalum powder and the organic powder (tantalum powder) is obtained. Due to the specific gravity of the powder: 1.6 to 3 and the specific gravity of the organic powder: 0.6), a powder that is not mixed uniformly is supplied into the die, and there is a problem that the molding density becomes non-uniform.

[0010] That is, although detailed in later, as shown in (B) in FIG. 4, the upper portion of the molded body D ₂ will gather small organic powder specific gravity, a molded body of a predetermined density, yet the weighing constant There was a problem that it was difficult to obtain a molded body.

In the conventional method 2 (a method of supplying a binder to a tantalum powder and granulating), when the powder is compression-molded, friction occurs between a molding die and the tantalum powder. It has a drawback that irregularities are hardly formed on the surface of the body.

The present invention has been made in view of the above problems and disadvantages, and has as its object to produce tantalum powder and tantalum powder satisfying the above-mentioned conditions required for a molded product thereof. Provided is a granulation method and a granulation apparatus therefor, in particular, to obtain a granulated tantalum powder having good fluidity and lubricity, and to form irregularities on the surface of a compact made of tantalum powder It is an object of the present invention to provide a method for granulating tantalum powder and an apparatus for granulating the tantalum powder.

[0013]

According to the present invention, as a means for achieving the above object, there is provided a method for mixing and granulating tantalum powder and organic powder using a fluidized bed granulator, and a method for carrying out the method. First, a tantalum powder and an organic powder are allowed to flow with a gas having a saturation point or less containing the solvent of the organic powder, and then the gas flow temperature is gradually lowered to reduce the solvent in the gas. Is made to flow in a supersaturated state for a certain period of time, and then made to flow again with a gas having a saturation point or less to perform granulation.

That is, the method for granulating tantalum powder according to the present invention is a method for granulating tantalum powder by mixing an organic powder with tantalum powder, wherein a fluidized bed granulator is used. In, the mixed powder of the tantalum powder and the organic powder, (1) a step including the solvent of the organic powder, a step of flowing with a gas below the saturation point of the solvent, (2) gradually lower the gas flow temperature in the fluidized bed, Granulating a tantalum powder, comprising: a step of flowing the solvent in the gas in a supersaturated state for a certain period of time, and (3) a step of flowing the solvent in the gas in the fluidized bed to a saturation point or lower again. Method ”(Claim 1).

Further, a granulating apparatus according to the present invention is an apparatus for performing the above-described method for granulating tantalum powder,
A fluidized bed granulator having a cylindrical processing vessel having an intake duct, an exhaust duct, and a frustoconical lower part tapered downward, wherein an air heater provided in the intake duct And a temperature detector provided in the processing container, a vaporizer for vaporizing an organic solvent, and a control unit for detecting the temperature and the flow time in the processing container and controlling the heat amount of the air heater and the vaporizer. A granulating apparatus for tantalum powder characterized by having a gamma powder "(claim 2).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. According to the granulation method including the steps (1) to (3) according to the present invention, in particular, the “fluidized bed” of the step (2) Step of gradually lowering the temperature of the gas stream in the inside and allowing the solvent in the gas to flow in a supersaturated state for a certain period of time, '' the tantalum mixed by the fluidized gas stream containing the solvent of the organic powder in the fluidized bed granulator The powder and the organic powder are condensed by lowering the airflow temperature, and the surface of the organic powder starts to dissolve due to the dew condensation, and the organic powder adheres to the tantalum powder during mixing,
The tantalum powder is granulated.

Then, when the above-mentioned adhesion has progressed,
In step (3), when the gas flow temperature in the fluidized bed is increased again as a means of `` flowing the solvent in the gas in the fluidized bed again at or below the saturation point '' and the powder is dried, the tantalum powder and the organic powder are removed. Is obtained. After that, if this granulated powder is compression-molded, a molded article of a constant density in which the organic powder is uniformly dispersed in each part is obtained, and when this molded article is sintered, the organic matter in the molded article is vaporized, A porous sintered body having an uneven surface can be produced.

Here, the compact of the tantalum powder obtained by the method for granulating the tantalum powder according to the present invention will be described with reference to FIG. FIG. 4 is a view showing a compact of tantalum powder, (A) is an external view of a compact made of the tantalum powder produced according to the present invention, and (B) is produced by the conventional method 1. It is an outline view of a compact made of tantalum powder.

The molded article D ₁ of the tantalum powder obtained by the granulation method according to the present invention, as shown in FIG. (A), is obtained as a uniform density. On the other hand, in the compact D ₂ of the tantalum powder produced by the conventional method 1 (compact D ₂ composed of a powder obtained by mixing only the tantalum powder and the solid organic powder),
Figure 4 (B), the cause gathered small organic powder on top of the specific gravity of the molding D _2, has a a molded body, yet not weighed constant of the molded body is obtained disadvantage of constant density .

As the organic powder and the solvent for the organic powder used in the granulation method according to the present invention, for example, PVB powder and methyl alcohol as a solvent for the PVB powder can be used. However, the present invention is not limited to the above-described organic powder and solvent, and any organic powder may be used as long as a desired granulated product or sintered body of tantalum powder aimed at in the present invention can be obtained. And a solvent can be used.

The apparatus for granulating tantalum powder according to the present invention comprises:
In summary, the fluidized-bed granulator having a cylindrical processing container having an intake duct, an exhaust duct, and a frustoconical lower portion tapered downward is provided. A solvent heater provided in the intake duct, a heater provided in the intake duct, a temperature detector provided in the processing vessel, and a temperature and flow time in the processing vessel for detecting the solvent heating. And a control unit for controlling the calorific value of the heater.

In particular, it is effective to have a structure in which the exhaust duct is branched, a part of which is connected to the intake duct, and which has a damper capable of switching the air flow to the exhaust side or the intake side. This is a preferred embodiment of the apparatus for granulating tantalum powder according to the present invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tantalum powder granulator according to the present invention will be described in detail with reference to FIG. FIG.
FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a tantalum powder granulator according to the present invention.

As shown in FIG. 1, the fluidized-bed granulator of this embodiment has a granulation vessel 1 as a processing vessel, an exhaust duct 2 connected to the upper part of the vessel 1, and a gas supply duct 2 connected to the lower part. It is composed of an intake duct 3 and the like. The granulation container 1 has a lower portion 4 having a truncated conical shape, a back filter 5 at a ceiling portion, and an air flow regulating plate 6 at a bottom portion (air having a mesh having an opening smaller in diameter than powder particles). A current plate 6) is provided.

An air heater 7 for heating air and a steam generator 8 for generating a solvent vapor are provided in the middle of the above-mentioned intake duct 3. This steam generator 8 includes:
The compressed hot air is supplied through the heater 9. The heating source (heater 9) of the steam generator 8 is an electric heater.
However, it is necessary to pay close attention to the safety of the solvent.

In the exhaust duct 2 described above, a manual damper 13 is provided at a stage subsequent to the back filter 5, and the distal end thereof is branched in three directions. The first branch 20 is for opening to the atmosphere, and an automatic damper 17 that can be opened and closed by the control unit 12 is installed in the opening. The second branch 21 is also open to the atmosphere, and an automatic damper 18 that can be opened and closed by the control unit 12 is installed in the opening.

Further, a first branch 20 and a second branch 21
, An automatic damper -1 that can be opened and closed by the control unit 12
9 are installed. On the other hand, the third branch 22 is connected to the intake side via a blower 23.
The exhaust side of 23 is connected to the intake duct 3.

In FIG. 1, reference numeral 10 denotes a temperature detector for measuring the temperature of the air flow in the granulation vessel 1, which is configured to send a signal to a temperature controller 11. The control unit 12 opens and closes the air supply valve 15 of the air heater 7, the compressed air supply valve 16 of the heater 9, and the valve 14 of the steam generator 8 based on the setting conditions of the temperature controller 11.

Next, the operation of the granulating apparatus (fluidized bed granulator) having the above configuration will be described with reference to FIG. 2 (timing chart).

First, a material supply port (not shown) of the granulation container 1
Tantalum powder A and solid organic powder B as materials
(Eg, PVB powder) is supplied to the granulation container 1, and the material supply port is closed. Next, the automatic dampers 17 and 18 are closed.
When the automatic damper 19 is opened and the blower 23 is operated, air flows as shown by the arrow in FIG.

The air that has flowed to the air straightening plate 6 flows in the direction of the arrow shown in the truncated cone-shaped lower part 4 of the granulation container 1, and then the tantalum powder A and the organic powder B (for example, PVB) are mixed in the granulation container 1. To mix. Powder state during this mixing is the "powder state" I "" shown in FIG. 2, this mixing is carried out for a predetermined time T _1.

The air in the granulation container 1 passes through a manually adjusted damper 13 via a bag filter 5 and is sucked into the blower 23 again.

Subsequently, the temperature inside the granulation container 1 is controlled by the control unit 12 to the temperature set by the temperature controller 11 (for example, 60 ° C.).
Until the air supply valve 15 is opened, warm air is supplied by the air heater 7 until the air supply valve 15 is opened. This operation is performed by a required time T ₂ shown in FIG.

Next, the valve 14 and the compressed air supply valve 16 are opened, whereby the solvent in the steam generator 8 is
(E.g., methyl alcohol) is exploded by hot air from the heater 9 to be vaporized, and the gas containing the solvent vapor is supplied to the intake duct 3.
Insulate inside. The vaporization of the solvent takes a predetermined time T shown in FIG.
Do only ₃ Although not shown, a solvent (eg, methyl alcohol) of an organic powder (PVB powder) is supplied to the steam generator 8 in advance.

Thereafter, the valve 14 and the compressed air supply valve 16 are set to "close", while the air supply valve 15 of the air heater 7 is set to "open", and the temperature set by the temperature controller 11 (for example, 20 ° C.). Gradually lower it. Do this by a required time T ₄ shown in FIG. This time T ₄
Inside, as shown in the “powder state“ II ”” of FIG. 2, the solvent condenses around the tantalum powder A and the organic powder B, whereby the organic powder B is dissolved and adheres to the tantalum powder A.

Subsequently, the process is continued at the set temperature (20 ° C.) for a predetermined time T ₅ . As a result, the tantalum powder A grows into the granulated tantalum powder C using the organic powder B as a binder, as shown in “powder state“ III ”” in FIG.

Finally, the control unit 12 controls the automatic damper-1.
7, 18 to "open", automatic damper 19 to "close",
Then, the air supply valve 15 of the air heater 7 is set to "open" so as to raise the temperature again to the temperature (for example, 60 ° C.) set by the temperature controller 11 in advance. Thereby, the air containing the circulating solvent is exhausted from the first branch 20, the air taken in from the second branch 21 becomes hot air, and the granulated tantalum powder C is dried. Time required T ₆ ).

After the required time T ₆ has elapsed, the air supply valve 15 is closed, the temperature in the granulation vessel 1 is lowered, and the operation of the blower 23 is stopped. Then, the granulated tantalum powder C is taken out from the material supply port (not shown) of the granulation container 1, and the operation of the present granulating apparatus (fluidized bed granulator) is completed.

Granulated tantalum powder C obtained in this example
And a powder obtained by the conventional method 1 (a powder obtained by mixing only the tantalum powder and the solid organic powder) for comparison. Table 1 shows the measurement results. In addition, "fluidity FR (g / sec) of powder" shown in Table 1
Represents the weight of the powder flowing down in one second by the measuring method according to JIS 2504.

[0040]

[Table 1]

As is clear from Table 1, the granulated tantalum powder C obtained in the present example has better fluidity than the powder obtained by the conventional method.

In the granulated tantalum powder C obtained in this example, the tantalum powder A and the organic powder B were not separated during the powder molding, and the granulated tantalum powder C having a uniform particle size was applied to the die. Since it is supplied, as shown in FIG.
Pressed compacts D ₁ may be of a uniform density was obtained. Moreover, after the sintering of the molded mold bodies D _1, the organic powder is vaporized, porous sintered compact which irregularities are formed on the surface of the molded mold bodies D ₁ was obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the present invention.
Modifications are possible and these are also included in the present invention. For example, without providing the automatic damper 19 shown in FIG.
An example can be given in which the first branch 20 is dedicated to exhaust and the second branch 21 is dedicated to intake. In this case, since the air for stirring the tantalum powder C does not circulate, a large amount of heat is required for the steam generator 8 when evaporating the solvent.

[0044]

As described in detail above, the present invention provides a method for mixing and granulating tantalum powder and an organic powder using a fluidized-bed granulator, and a granulator for performing the method. First, the tantalum powder and the organic powder are caused to flow with a gas having a saturation point or lower containing the solvent of the organic powder, and then the gas flow temperature is gradually lowered to allow the solvent in the gas to flow in a supersaturated state for a certain period of time. After that, the mixture is granulated by flowing again with a gas having a saturation point or less, thereby producing an effect that a granulated tantalum powder having good fluidity and lubricity can be obtained.

Further, according to the present invention, since the fluidity and lubricity are good, a compact having a uniform density and a constant weight can be obtained, and the properties of the sintered body obtained from the compact can be obtained. As a result, there is an effect that an extremely porous sintered body can be obtained in which the individual particles have a complicated outer shape with a lot of irregularities, and a sintered body suitable for a capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a tantalum powder granulator according to the present invention.

FIG. 2 is a timing chart of the embodiment shown in FIG. 1;

FIG. 3 shows an apparatus for mixing tantalum powder used in conventional method 1.
The figure which shows a (V-shaped mixer).

FIG. 4 is a view showing a compact of a tantalum powder, and (A)
1 is an external view of a molded article made of a tantalum powder produced according to the present invention, and FIG. 2 (B) is an external view of a molded article made of a tantalum powder produced by Conventional Method 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Granulation container 2 Exhaust duct 3 Intake duct 4 Lower part of truncated-cone shape 5 Bag filter 6 Air rectifying plate 7 Air heater 8 Steam generator 9 Heater 10 Temperature detector 11 Temperature controller 12 Control part 13 Manual damper 14, 15, 16 Valve 17, 18, 19 Automatic damper 20 First branch 21 Second branch 22 Third branch 23 Blower 50 V-shaped container 51 Shaft 52 Bearing 53 Motor A Tantalum powder B organic powders C granulated tantalum powder D _1, D ₂ moldings

Claims (3)

(57) [Claims] 1. A method for granulating tantalum powder by mixing an organic powder with a tantalum powder, wherein a fluidized bed granulator is used, and a mixed powder of the tantalum powder and the organic powder is mixed in the granulator. 1) containing the solvent of the organic powder, and flowing with a gas having a temperature lower than the saturation point of the solvent, (2) gradually lowering the gas flow temperature in the fluidized bed, and allowing the solvent in the gas to flow in a supersaturated state for a certain period of time. And (3) a step of causing the solvent in the gas in the fluidized bed to flow again at or below the saturation point to flow the tantalum powder. 2. A fluidized-bed granulator having a cylindrical processing vessel having an intake duct, an exhaust duct, and a downwardly tapering frustoconical lower portion, provided in the intake duct. Air heater, a temperature detector provided in the processing container, a vaporizer for vaporizing an organic solvent, and detecting a temperature and a flow time in the processing container to control the amount of heat of the air heater and the vaporizer. The apparatus for granulating tantalum powder used in the method for granulating tantalum powder according to claim 1, further comprising a controller. 3. The damper according to claim 2, wherein the exhaust duct is branched, and a part of the branch is connected to the intake duct, so that the airflow can be switched to the exhaust side or the intake side. Tantalum powder granulator.