WO2005077573A1

WO2005077573A1 - Method for producing valve metal

Info

Publication number: WO2005077573A1
Application number: PCT/JP2005/002242
Authority: WO
Inventors: Hitoshi Iijima; Yuji Fukumoto
Original assignee: Cabot Supermetals K.K.
Priority date: 2004-02-16
Filing date: 2005-02-15
Publication date: 2005-08-25

Abstract

A method for producing a valve metal powder is characterized in that a solid reducing agent is added to an oxide of a valve metal which has been heated to 900-1100˚C or a mixture of such an oxide of the valve metal and the solid reducing agent.

Description

Specification

Manufacturing method of valve metal

Technical field

The present invention relates to a method for producing a capacitor and a valve metal powder used for the capacitor.

This application claims the priority of Japanese Patent Application No. 2004-038409 filed on Feb. 16, 2004, the contents of which are incorporated herein by reference.

Background art

[0002] Tantalum and niobium metal powders are widely used in capacitors and capacitors because of their excellent corrosion resistance and their oxides are dielectrics. Conventionally, as a method for producing tantalum metal powder, for example, potassium and sodium tantalum fluoride are added to a molten salt such as potassium salt and sodium salt in a reactor equipped with a stirrer, and then the solution is added. A method of obtaining potassium tantalum metal powder by reducing potassium tantalum fluoride with sodium is known (for example, see Patent Document 1).

In addition, a solid reducing agent such as magnesium or calcium is heated and gasified in advance, and the gasified reducing agent is introduced into a heated reactor, and the temperature and time in the reduction reaction are selected, and the reducing agent is combined with the reducing agent. A method of reacting a valve metal with an oxide has been proposed (for example, see Patent Document 2).

Patent Document 1: U.S. Pat.No. 2,950,185

Patent Document 2: Japanese Patent Publication No. 2002-544375

Disclosure of the invention

Problems to be solved by the invention

[0003] However, the method described in Patent Literature 1 requires complicated post-treatment and requires a large amount of cost and time for production. In particular, disposal of a compound containing fluoride or chloride is a problem. . Furthermore, in the method of reducing potassium niobium fluoride with sodium, which is also known to apply the method of reducing potassium tantalum fluoride with sodium, potassium diobium fluoride does not easily precipitate. Highly reactive and corrosive, obtained for Low purity of niobium metal powder. Therefore, it is difficult to obtain high quality niobium metal powder.

Further, in the method described in Patent Document 2, heating for gasifying solid magnesium and heating for reaction are separate steps, and there is no waste in energy consumption.

The present invention has been made in view of the above-mentioned circumstances, is easy to perform post-treatment, and can obtain not only a tantalum metal powder but also a high-quality niobium metal powder. An object of the present invention is to provide a method for producing valve metal powder.

Means for solving the problem

[0004] The method for producing a valve metal powder according to the first aspect of the present invention provides a method for solid-state reduction of a heated valve metal oxide or a mixture of a valve metal oxide and a part of a solid reducing agent. It is characterized by adding an agent.

The method for producing the knob metal powder is preferably performed under reduced pressure.

In the production method of the valve metal powder, it is preferable to separately supply the oxide of the valve metal.

Further, the method for producing the valve metal powder is preferably performed under stirring. The method for producing a valve metal powder according to the second aspect of the present invention is characterized in that after mixing an oxidized product of a valve metal and a solid reducing agent, these are heated.

Further, in the above method for producing valve metal powder, the heating temperature is preferably 900-1100 ° C.

[0005] In the above method for producing a valve metal, the heating temperature may be 500 to 900 ° C.

In the above method for producing a valve metal, it is preferable that the heated oxidized valve metal or the oxidized valve metal is reacted with a solid reducing agent in a liquid phase.

The method for producing a valve metal powder according to the third aspect of the present invention,

Mixing a valve metal oxide and a solid reducing agent,

The mixture of the oxidized product of the knob metal and the solid reducing agent is gradually heated to a predetermined temperature, and is maintained at the predetermined temperature to mix the valve metal oxide and the solid reducing agent. Reacting. [0006] In the method for producing a valve metal powder according to the third aspect, the predetermined temperature is preferably 500 to 900 ° C.

In the method for producing a valve metal powder according to the third aspect, the mixture of the valve metal oxide and the solid reducing agent is gradually heated to a predetermined temperature, and is maintained at the predetermined temperature. The step of reacting the valve metal with the solid reducing agent is preferably performed in a closed atmosphere.

In the method for producing a valve metal powder according to the third aspect, the mixture of the valve metal oxide and the solid reducing agent is gradually heated to a predetermined temperature, and is maintained at the predetermined temperature. The step of reacting the valve metal with the solid reducing agent is preferably performed with stirring.

[0007] The method for producing a valve metal powder according to a fourth aspect of the present invention comprises:

A method for producing valve metal powder, characterized by gradually adding a solid reducing agent to a heated valve metal oxide and reacting the valve metal oxide with the solid reducing agent. .

In the method for producing a valve metal powder according to the fourth aspect, the oxide of the valve metal is preferably heated to 900-1100 ° C.! /.

In the method for producing a valve metal powder according to the fourth aspect, it is preferable that the addition of the solid reducing agent is performed in a closed atmosphere.

In the method for producing a valve metal powder according to the fourth aspect, it is preferable that the addition of the solid reducing agent is performed while stirring the oxidized product of the valve metal.

In the method for producing a valve metal powder according to the third or fourth aspect, it is preferable that the valve metal powder and Z or a solid reducing agent oxide are further included as a diluent.

[0008] In addition, the valve metal generally means aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, or the like, whose surface is anodized by anodic oxidation. In the present invention, tantalum and niobium among the above metals are collectively referred to as a valve metal. In addition, the valve metal may include a lower oxidized material having a lower oxidized number than TaO, such as tantalum monooxide. Yes. This is because even a low-grade oxidant can be used as an anode of a capacitor. The invention's effect

[0009] According to the method for producing a valve metal powder of the present invention, post-processing is simple, and not only a tantalum metal powder but also a high-quality niobium metal powder can be obtained. In addition, since heating for gasifying solid magnesium and heating for reaction can be shared, there is little waste in energy consumption. As a result, the cost required for producing the valve metal powder can be reduced.

In the production method of the valve metal powder of the present invention, when performed under reduced pressure, the solid reducing agent can be gasified at a lower temperature than at normal pressure, so that the energy consumption can be further reduced.

In the method for producing valve metal powder of the present invention, the valve metal powder can be prevented from becoming coarser by dividing and supplying the valve metal oxide.

Further, according to the valve metal powder production method according to the third and fourth aspects of the present invention, the hydroxide of the valve metal is appropriately granulated by using the reducing agent in a solid state. Thus, the valve metal powder suitable for a capacitor can be obtained without going through the subsequent aggregation step.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram showing a manufacturing apparatus used in an embodiment according to the present invention.

Explanation of symbols

[0011] 10 Manufacturing equipment

11 Reaction chamber

12 Stirrer

13 heater

14 Gas lead-in / out pipe

15 Reducing agent supply pipe

16 Oxide supply pipe

21 Valve 26 magnet

27 Stirring shaft

28 Stirrer blade

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the method for producing a valve metal powder of the present invention will be described.

This embodiment is an example in which solid magnesium is used as a solid reducing agent to produce tantalum metal powder from tantalum oxide.

FIG. 1 shows a schematic configuration diagram of a manufacturing apparatus for performing the method for manufacturing tantalum metal powder.

This production apparatus 10 is a device that performs a reaction between tantalum acid sardine (Ta 2 O 3) and solid magnesium.

twenty five

A reaction chamber 11 made of Tenres, a stirrer 12 for stirring the contents in the reaction chamber 11, a heater 13 for heating the reaction chamber 11, a gas outlet / inlet pipe 14 for introducing and introducing gas into the reaction chamber 11, and a solid It has a reducing agent supply pipe 15 that supplies magnesium into the reaction chamber 11 and an oxide supply pipe 16 that supplies tantalum oxide into the reaction chamber 11.

[0013] In the manufacturing apparatus 10, a valve 21 that can be closed is installed in the gas outlet / inlet pipe 14 so that the inside of the reaction chamber 11 can be maintained after the pressure inside the reaction chamber 11 is reduced. Further, the reducing agent supply pipe 15 and the oxidizing substance supply pipe 16 are provided such that their tips are located at the lower part in the reaction chamber 11.

The stirrer 12 is disposed outside the reaction chamber 11 and is a motor 25 that is driven to rotate, a cylindrical magnet 26 connected to the motor 25, and is disposed inside the reaction chamber 11 and is linked to the motor 25. It has a stirring shaft 27 that rotates by rotation and a stirring blade 28 attached to the stirring shaft 26 so that the contents supplied into the reaction chamber 11 can be stirred and mixed.

In the method for producing tantalum metal powder using the production apparatus 10, first, tantalum oxide is supplied into the reaction chamber 11 through the oxide supply pipe 16, then the valve 21 is opened, and the gas The gas in the reaction chamber 11 is discharged through the inlet / outlet pipe 14 to reduce the pressure. Next, after closing the valve 21, the inside of the reaction chamber 11 is stirred by the stirrer 12 and heated by the heater 13. Then, while the heating temperature is maintained, a part of the solid magnesium is added through the reducing agent supply pipe 15. Further, solid magnesium is newly added to the mixture of the tantalum oxide and a part of solid magnesium. Then, the addition of solid magnesium is continued until the tantalum oxide is reduced to metal. The solid magnesium added may be continuous or intermittent, and the amount added is about ヽ, which does not rapidly react.

In the stirring in the above manufacturing method, the rotation of the motor 25 of the stirrer 12 is transmitted to the magnet 26, and the rotation of the motor 26 is transmitted to the upper portion 29 of the stirring shaft in the reaction chamber 11 by the magnetic force of the magnet 26 to rotate the stirring shaft 27. . In this way, if the rotation of the motor 25 is transmitted to the stirring shaft 27 by magnetic force, it is not necessary to use the gland packing for sealing the stirring shaft 27, and the stirring shaft in the sealed container can be rotated. The tightness of the reaction chamber 11 can be increased.

[0017] The heating temperature when adding solid magnesium to tantalum oxide is preferably 900 to 1100 ° C. If the heating temperature is lower than 900 ° C, the reactivity between the tantalum oxide and solid magnesium tends to be low even if the pressure in the reaction chamber is reduced, and if it exceeds 1100 ° C, it is obtained by rapid reaction. Tantalum metal powder tends to be coarse.

In the above manufacturing method, before adding solid magnesium, argon gas may be sealed in the reaction chamber 11 through the gas inlet / outlet pipe 14 to a degree that the pressure becomes atmospheric pressure. preferable. Since stainless steel and magnesium have high affinity, gasified magnesium

However, if argon gas is sealed in the reaction chamber, magnesium can be prevented from adhering to the inner wall of the reaction chamber.

In the embodiment described above, a portion of solid magnesium is added to the heated tantalum sulfide, and the solid magnesium is gasified on the surface of the tantalum sulfide and the gas is converted to a gas. The solid magnesium thus reacted reacts with the tantalum oxide to produce tantalum metal powder. That is, since the gasification of solid magnesium and the reaction of solid magnesium and tantalum oxide are performed simultaneously, heating for gasifying solid magnesium and heating for reaction can be shared, and waste of energy consumption can be reduced. .

In addition, since the tantalum oxide is used as a raw material and no molten salt is used, post-treatment is simple, and the cost and time required for production can be reduced. In particular, the problem of discarding compounds containing fluoride and chloride can be omitted.

[0020] Further, in the above-described production method, a part of solid magnesium is added to the tantalum sardine. After that, solid magnesium is newly added to the mixture of the tantalum oxide and a part of the solid magnesium to divide the amount of solid magnesium necessary to reduce the tantalum oxide. Add soil. Therefore, rapid heat generation can be suppressed, and coarsening of the tantalum metal powder can be prevented. However, solid magnesium is added in an amount that reacts to the extent that heat of reaction can be removed.

[0021] In addition, in the above-mentioned production method, since solid magnesium is added to tantalum oxide under reduced pressure, solid magnesium can be gasified at a temperature lower than normal pressure, and energy consumption can be further reduced. Can be reduced.

Furthermore, in the above-mentioned production method, the solid magnesium is added while stirring with a stirrer, so that the reaction between the tantalum oxide and the solid magnesium can be homogenized, and a local rise in temperature can be prevented. It is possible to further prevent the product from becoming coarse. Furthermore, since the particles are granulated by stirring, the shape of the tantalum sulfide may not be particulate, so that the tantalum sulfide used by granulation by spray drying or the like may not be used.

[0022] The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, after heating the tantalum iris, solid magnesium was previously added to the force tantalum iris, mixed, and then heated. May be. However, in that case, care should be taken not to increase the amount of solid magnesium and the heating temperature too much! If the amount of solid magnesium is too high or the heating temperature is too high, a runaway reaction may occur.

Further, the power of dividing and adding solid magnesium to tantalum iris may be added to the tantalum iris. Other solid reducing agents include solid calcium and solid lithium.

Further, in the above-described embodiment, the tantalum oxide may be divided and supplied by dividing and adding only solid magnesium. If the tantalum oxide is also divided and supplied, the rapid reaction can be further suppressed, and the resulting tantalum metal powder can be further prevented from becoming coarse. The tuna soup of the tantalum sardine may be continuous or intermittent. In addition, when adding tantalum acid stilts, they may be added independently of solid magnesium, or mixed with solid magnesium and subjected to forced addition. In the above-described embodiment, the niobium metal powder can also be manufactured from the niobium aniride by replacing the tantalum aniride with the niobium aniride. In the case of niobium oxide, the same effects as those of tantalum oxide are exhibited, and high-quality niobium metal powder is used because potassium niobium fluoride, which is highly reactive and corrosive, is not used as a raw material. Obtainable.

[0024] A diluent may be added at the time of reaction between the tantalum oxide and the solid reducing agent. If a diluent is added, the concentration of the reactants can be reduced, so that a rapid reaction can be further suppressed and the calorific value can be reduced. Therefore, coarsening of the metal powder can be further prevented.

Here, the diluent is a substance that does not participate in the reaction between the tantalum oxide and the solid reducing agent.A diluent that does not become an impurity of the obtained metal powder, that is, an oxide or a target substance of the solid reducing agent. For example, in the case of a reaction between tantalum oxide and solid magnesium, tantalum metal or magnesium oxide is preferred.

. Further, when coarse particles are used as the diluent, the diluent can be separated only by a sieve after the reaction, and thus it is easy to separate into tantalum metal and solid magnesium.

[0025] Furthermore, in the present invention, the pressure in the reaction chamber does not necessarily have to be reduced, and stirring is not necessary. However, when the pressure is reduced, the energy consumption can be reduced, and when the stirring is performed, coarsening is further prevented. preferable. However, even without stirring, coarsening can be prevented by uniformly adding the solid reducing agent. As a method of uniformly adding the solid reducing agent, for example, a method of adding the solid reducing agent while appropriately changing the addition position by making the tip of the reducing agent supply pipe freely movable in the reaction chamber, and the like. Can be In this manner, if the solid reducing agent is uniformly added, the oxidized product of the valve metal and the solid reducing agent can be gently reacted with each other, so that the resulting metal powder can be prevented from becoming coarse. .

[0026] The valve metal powder obtained by the above-described manufacturing method is mainly used for a solid electrolytic capacitor. Generally, to manufacture a solid electrolytic capacitor, a binder is added to tantalum metal powder, press-molded, and then sintered to produce a porous sintered body. Next, the lead wire is embedded in the porous sintered body, pressed by force, sintered, and the lead wire is integrally formed. Let This is subjected to a chemical conversion treatment (anodic oxidation) in an electrolytic solution such as phosphoric acid or nitric acid to form an oxide on the surface, thereby obtaining an anode for a solid electrolytic capacitor and a dielectric.

Then, a power source such as manganese dioxide, lead oxide, or a conductive polymer, a dalaphite layer, and a silver paste layer are sequentially formed on the oxide by a known method, and then a cathode terminal is mounted thereon. After connection, a resin jacket is formed to obtain a solid electrolytic capacitor.

Example 1

Hereinafter, examples of the method for producing valve metal powder of the present invention will be described.

440 g of tantalum oxide raw material (approximately spherical powder with an average particle diameter of 3 μm) was preheated to 500 ° C while stirring at 200 rpm, and 5 g of solid magnesium was added when the heat generation stopped while observing the heat generation status It was added 30 times while controlling so that A black mass with a diameter of about 2-3 cm was obtained. It was easily disintegratable by hand. The crushed product was sieved through a 60-mesh sieve, and the sieved 60-mesh pass product was washed with an acid and analyzed. As a result, it was found that the metal was high-purity tantanole metal.

Example 2

[0028] 1 kg of a tantalum oxide raw material (approximately spherical powder having an average particle diameter of 3 µm) is preheated to 500 ° C with stirring at 70 rpm, and 13 g of solid magnesium is heated while observing the heat generation state. When it was settled, the addition was repeated, and the mixture was added to 470 g to reach 950 ° C. A black mass of about 2-3 cm in diameter was obtained. It was easily disintegratable by hand. The dried product was sieved through a 60-mesh sieve, and the sieved 60-mesh pass product was washed with an acid and then analyzed.

Example 3

[0029] 450g of magnesium oxide and 450g of magnesium tantalum having an average particle diameter of 7 were preheated to 700 ° C, and while stirring at 250rpm, 5g of solid magnesium was observed while the heat generation was stopped. The addition was performed 40 times while controlling the addition. The obtained powder was treated with a 60-400 mesh sieve, the obtained powder was washed with an acid, and the obtained powder was analyzed. As a result, it was found that the powder was a highly pure tantanole metal.

Example 4 [0030] 350 g of magnesium oxide having an average particle size of 2. l ^ m (specific surface area: 7.8 m ² ) previously impregnated with 150 g of magnesium at 900 ° C is used as a reducing agent. After adding tanitantalum, they were mixed and reacted at 900 ° C. The obtained powder was treated with a 60-400 mesh sieve, the obtained powder was washed with an acid, and the obtained product was analyzed. As a result, it was found to be high-purity tantalum metal.

Comparative example

[0031] When 440 g of tantalum raw material was preheated to 900 ° C, and 25 g of solid magnesium was added five times, a hard lump was generated. When this was analyzed, tantalum magnesium iridani was detected. Was.

[0032] (Knowledge)

The following findings were obtained from the above Examples and Comparative Examples.

From the results of Examples 14 to 14, it can be seen from the results that a mass of a metal obtained by reacting an oxide material having a diameter of about several centimeters with a reducing agent and a reducing agent oxidized product was formed by hand. It was brittle enough to break, resulting in granulation of the porous body. Therefore, by using the method for producing a knurled metal powder of the present invention, reduction can be performed continuously without going through multiple steps. The result was not a composite with magnesium, and a porous metal tantalum was obtained.

500 ° C strength Magnesium addition was started and maintained at about 800 ° C, enabling agitation reduction reaction. It is thought that the effects of the melting point and boiling point of magnesium will be the same even under vacuuming and under the conditions of! /.

The contact time between tantalum and magnesium is problematic. It is thought that a rapid reaction occurs when sufficiently contacted even near the melting point, but once the magnesium oxide film is formed, the rapid reaction stops.

Although it is possible to cause a mild reduction reaction by gasifying magnesium, as described in JP-A-2003-277822, the shape of tantalum oxide used as a raw material is taken over. However, since the shape remains as the shape of the final product, tantalum, it is necessary to adjust the shape at the raw material stage.If fine tantalum oxide is used, the subsequent aggregation process required for tantalum for capacitors will be required. It becomes difficult. On the other hand, by using magnesium in a solid state as in the method of the present invention, it is possible to reduce oxidized tantalum while appropriately granulating it, and to use it for a capacitor without a subsequent aggregation step. A suitable tantalum powder can be obtained.

Industrial applicability

The method for producing a valve metal powder of the present invention can be applied to the production of tantalum metal powder, niobium metal powder, and the like.

Claims

The scope of the claims

[1] A method for producing a valve metal powder, comprising adding a solid reducing agent to a heated valve metal oxidizing compound or a mixture of a valve metal oxidizing compound and a part of a solid reducing agent.

[2] The method for producing a valve metal powder according to claim 1, wherein the method is performed under reduced pressure.

[3] The method for producing a valve metal powder according to claim 1, wherein the oxide of the valve metal is divided and supplied.

[4] The method for producing a valve metal powder according to claim 1, wherein the method is performed under stirring.

[5] A method for producing a valve metal powder, which comprises mixing an oxide of a knob metal and a solid reducing agent and then heating them.

[6] The method for producing a valve metal powder according to claim 1, wherein the heating temperature is 900 to 1100 ° C.

[7] The method for producing a valve metal powder according to claim 1, wherein the heating temperature is 500 to 900 ° C.

8. The method for producing valve metal powder according to claim 1, wherein the heated valve metal oxide or the valve metal oxide and a solid reducing agent react in a liquid phase.