JP3229353B2 - Method for producing metal oxide 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 for producing a metal oxide powder for synthesizing a metal oxide powder from a metal powder by a metal powder combustion method.

[0002]

2. Description of the Related Art In recent years, a metal powder combustion method for synthesizing a metal oxide powder by burning a metal powder has been developed as disclosed in Japanese Patent Application Laid-Open No. 60-255602. To explain this manufacturing method, a metal powder such as aluminum, silicon and magnesium is supplied together with a carrier gas into a reaction vessel under an oxidizing atmosphere and ignited in the reaction vessel to form a flame. In this flame, metal powder, its oxide, and the like exist as solids, liquids, and gases, and it is considered that a part of the gases is turned into plasma. At such an ultra-high temperature, the oxidation reaction is completed instantaneously, and the oxide powder is synthesized immediately after the flame cooling. Thereafter, the oxide powder contained in the fuel exhaust gas is separated and collected by a collecting device such as a bag filter.

According to this manufacturing method, not only single metal oxide powders such as alumina, silica, and magnesia, but also
Composite metal oxide powders such as mullite and spinel can also be easily produced.

[0004]

However, the above metal powder combustion method has a feature that the synthesized oxide powder has a true spherical shape, and is applicable to semiconductor encapsulants, ceramic raw materials, cosmetic materials, and the like. It is considered. For example, silica
For alumina and the like, a semiconductor encapsulant is considered as one of the applications. Here, raw materials for the semiconductor industry such as semiconductor encapsulants are generally required to have extremely high purity.

[0005] However, the purity of the metal oxide powder synthesized by the conventional metal powder combustion method cannot always meet the demand. Thus, in the metal powder combustion method, it is extremely important to improve the purity of the synthesized metal oxide powder. The impurities contained in the synthesized metal oxide powder can be roughly classified into cationic, anionic, nonionic inorganic or organic substances, and the like. The metal powder used in the metal powder combustion method is generally subjected to an acid treatment with hydrofluoric acid, hydrochloric acid, a mixed acid or the like in order to control its purity. This acid treatment is mainly performed to remove cationic and nonionic inorganic substances. When the metal material is acid-treated, it is contaminated with an anionic substance. Therefore, the metal material after the acid treatment is washed with water.

However, as a result of investigations by the present inventor, it has been found that even if the metal powder thus treated with acid is used, the extracted water of the synthesized metal oxide powder contains several ppm to several ppm of fluorine ions and chlorine ions. It was found that the content was about 10 ppm. Also, when air or nitrogen is used as the carrier gas, NO _x is generated as a pollutant in the combustion flame,
Consequently synthesized metal oxide surface to NO _x the powder is also deposited and adsorption. As the pollutants in the combustion flame, there are carbon monoxide, soot and the like in addition to the above NO _x ,
These can be prevented from being generated by converting the flammable gas into hydrogen or the like, and these impurities are to the extent that they are not detected by actual extraction detection of the metal oxide powder.

The present invention has been made in view of the above circumstances, and has as its object to improve the purity of a synthesized metal oxide powder.

[0008]

SUMMARY OF THE INVENTION To solve the above problems the present invention is to provide a metal powder with a carrier gas is supplied into the reaction vessel under an oxidizing atmosphere to burn the metal powder in the reaction vessel, synthesizing the metal oxide powder, synthesized
In the method for producing a metal oxide powder, wherein the recovered metal oxide powder is recovered by a recovery means, the synthesized metal oxide powder is subjected to solid-gas phase separation while heating the recovery means .

A collecting means for collecting the synthesized metal oxide powder
As the steps, for example, as shown in an
A dust collector such as a filter can be used. This collection means
Solid phase separation of synthesized metal oxide powder while heating
By this, the synthesized metal oxide powder is
Control the recovery temperature when separating and recovering
Wear. That is, metal oxide synthesized by continuous operation
The material powder can be recovered while being heated. This heat treatment is preferable as the treatment temperature is increased and the treatment time is extended because volatile impurities adhering to and adsorbing to the metal oxide powder can be removed. The processing temperature is 1000
C. or higher is not preferable because it causes fusion and the like of the synthesized metal oxide powder. Note that the reference
As shown in the example, the recovered metal oxide powder was
-Batch operation of heating in a heat treatment furnace such as kiln or electric furnace
Attach and adsorb to synthesized metal oxide powder
It is possible to remove volatile impurities.

[0010] For example, it was synthesized by metal powder combustion method Shi
Regarding Lica powder, recovery temperature and adsorption NO _{x of} silica powder
The relationship between the concentration, the results of experiments on the concentration of NO _x different combustion exhaust gas as shown in FIG. 2, it is possible to lower the adsorption concentration of NO _x of the silica powder the higher the recovery temperature. Note NO _x due to the presence of moisture and excess oxygen with flammable gas combustion, most are considered to be present in the form of NO ₂ and HNO _3, which together highly soluble in water. Therefore, the metal oxide powder after the heat treatment, chlorine, to detect the degree of removal of volatile impurities such as fluorine and NO _x, the determination is to measure the extraction water electric conductivity of the metal oxide powder It is preferable because it can be performed quickly.

In the present invention, a metal oxide powder is synthesized by a conventional metal powder combustion method. That is, a metal oxide powder is synthesized by supplying a metal powder together with a carrier gas into a reaction vessel under an oxidizing atmosphere, igniting in the reaction vessel to form a flame, and burning the metal powder. . The types of the metal powders were silicon, aluminum, magnesium, titanium, silicon, zirconium, a mixture of silicon and aluminum prepared in a mullite composition, a mixture of magnesium and aluminum prepared in a spinel composition, and a cordierite composition. A mixture of aluminum, magnesium, and silicon can be used. Further, an alloy powder prepared with these compositions may be used. The particle size distribution of the metal powder may be within a range in which deflagration can be formed. However, since the metal powder having a particle diameter larger than 400 μm may be separated and recovered without being completely oxidized, the particle diameter of the metal powder is preferably 400 μm or less. μm
And more preferably several tens μm.

Air, nitrogen, oxygen, helium, argon and the like can be used as the carrier gas into which the metal powder is dispersed and introduced into the reaction vessel. Further, a flammable carrier gas can be used. The metal powder introduced into the reaction vessel together with the carrier gas is a chemical flame such as a burner, resistance heating, arc discharge, plasma flame,
It is ignited using a heat source such as a laser, high-frequency induction heating, and an electron beam, and forms an initial flame by explosive combustion. The metal powder forms a liquid incompletely burned metal oxide powder by initial oxidation combustion in the flame.

For example, when a burner is used as a heat source for ignition, the metal powder is ignited by a burner flame formed by a combustible gas and a flammable gas, and forms an initial flame by explosive combustion. Oxygen / air and a mixed gas thereof can be used as the supporting gas for forming the initial flame. The combustible gas as the pilot flame is methane, ethane, it can be used a hydrocarbon gas, or hydrogen gas represented by the chemical formula C _n H2 _{n + 2} such as propane. In addition,
The combustion flame for the pilot fire by the combustible gas only needs to have a minimum ignition energy necessary to form an initial dust explosion. Further, the combustible gas may be continuously supplied during the combustion of the metal powder, or may be stopped after the combustion flame is stabilized. However, since the amount of the flammable gas slightly affects the particle size of the metal oxide powder, it is necessary to appropriately select the amount according to the desired particle size.

The metal powder and the combustion gas are usually supplied into the reaction vessel at room temperature. However, the reaction vessel is preferably lined with a heat-resistant material such as alumina because the combustion flame temperature becomes 1000 ° C. or higher. . Also, inside the reaction vessel,
It is preferable that an exhaust fan or the like is provided on the exhaust side for suction, and the pressure is a negative pressure of about −200 to −10 mmAq on the atmospheric pressure basis.

The metal oxide powder synthesized in the reaction vessel is separated and recovered by a recovery device provided on the exhaust side of the reaction vessel. As the collection device, a dust collector can be used. As dust collectors, electric dust collectors, bag filters,
A collecting drum type fine powder collecting device or the like can be used.

[0016]

Method for producing a metal oxide powder of the effects of the present invention is recovered hand
By the metal oxide powder which is synthesized while heating the stage for solid-gas phase separation <br/>, attached to the surface of the metal oxide powder, fluorine adsorbed, volatile impurities such as chlorine and NO _x It can be volatilized and removed, and a high-purity metal oxide powder can be obtained.

[0017]

Embodiments of the present invention will be described below. EXAMPLE 1 A production apparatus schematically shown in FIG. 1 comprises a reaction vessel 1 having an inner wall lined with alumina brick,
And a burner 3 disposed between the reaction vessel 1 and the metal powder supply device 2.
And a recovery device 4 connected to the downstream side of the reaction vessel 1.

The metal powder supply device 2 has a valve 21 at one end.
And a second end connected to the burner 3 to introduce a carrier gas, in which metal powder is dispersed, into the burner 3.
Hopper 23 having a lower end connected to metal powder 22 and containing metal powder.
And L is connected to the burner 3 via a valve 31.
A flammable gas supply pipe 32 connected to a PG gas cylinder (not shown) is connected to a flammable gas supply pipe 34 connected to an oxygen cylinder (not shown) via a valve 33. The flammable gas and the flammable gas supplied from the flammable gas supply pipe 32 and the flammable gas supply pipe 34 are supplied into the reaction vessel 1.

The collecting device 4 includes a collecting pipe 41 opened on the side wall of the reaction vessel 1, a bag filter 42 provided downstream of the collecting pipe 41, and a connecting pipe 43 provided downstream of the bag filter 42. The exhaust gas processing device 44 is disposed through the exhaust gas processing device, and an air blower 45 is also disposed downstream of the exhaust gas processing device via the connection pipe 43. Bag filter 42
Is heat-resistant and has a heater 42a for heating.

Using the manufacturing apparatus configured as described above,
Silica powder was synthesized from commercially available powdered metallic silicon adjusted to about 2 mm and metal silicon powder whose average particle diameter was adjusted to 15 μm. The valve 31 is opened to supply LPG gas at a flow rate of 1 Nm ³ / hr from the flammable gas supply pipe 32, and the valve 33 is opened to supply 15 Nm of oxygen from the flammable gas supply pipe 32.
It is supplied at a flow rate of ³ / hr, and is ignited by ignition means (not shown) to form an LPG flame as a pilot flame. Then, the valve 21 is opened and air as carrier gas is
While supplying at a flow rate of Nm ³ / hr, metallic silicon powder was supplied from the hopper 23 at a flow rate of 9 kg / hr. As a result, the metal silicon powder together with the carrier gas is
And contacted with the LPG flame to form a combustion flame, thereby synthesizing a silica powder as a metal oxide powder. Then, the combustion exhaust gas containing the silica powder was sucked by the suction force of the air blower 45, and the silica powder was separated and collected by the bag filter 42. At this time, the heater 4 of the bag filter 42
The recovery temperature is controlled to a predetermined temperature by the control of 2a. The pressure in the reaction vessel 1 is set to −100 mmAq on the basis of the atmospheric pressure by the suction force of the exhaust fan 45. The BET specific surface area of the recovered silica powder is 9
m ² / g, and the NO _x concentration of the exhaust gas is 1620 pp
m. (Evaluation 1) A 10% slurry solution of each silica powder (extraction water electric conductivity was 1.1 μs /
cm of ion-exchanged water) and the concentrations of nitrate ion, fluorine ion and chloride ion were measured, and the following results were obtained.

[0021]

[Table 1] As described above, by directly controlling the recovery temperature of the synthesized metal oxide powder, the extraction water purity of the metal oxide powder could be significantly improved. ( Reference Example ) Using the same manufacturing apparatus as in Example 1, silica powder was synthesized from commercially available powdered metallic silicon adjusted to about 2 mm and metal silicon powder adjusted to an average particle diameter of 15 μm. The flow rate of each gas is as follows: carrier gas: 4 Nm ³ / hr;
LPG Gas: 1Nm ³ / hr, oxygen gas: 15Nm ³ /
hr, and the supply amount of the metal silicon powder was 9 kg / hr. Then, the collection temperature is set to 60 ° C. by the heater 42 a of the bag filter 42, and the BET specific surface area of 15 m ² / g
The silica powder was recovered.

The recovered silica powder is supplied at a rate of 30 kg / hr to a rotary kiln having a quartz tube having a diameter of 150 mm and maintained at a predetermined temperature.
Heat treatment was performed while flowing at a flow rate of 0 liter / hr. (Evaluation 2) The holding temperature of the rotary kiln was 100 ° C., 200 ° C., and 4
Measure the concentration of nitrate ion, fluorine ion, and chloride ion and the extracted water electric conductivity of a 10% slurry solution (ion-exchanged water having an extracted water electric conductivity of 1.1 μs / cm) at 00 ° C and 500 ° C. Then, the following results were obtained.

[0023]

[Table 2] By subjecting the recovered silica powder to a heat treatment, the purity of the extracted water of the silica powder was significantly improved.

[0024]

As described above in detail, according to the method for producing a metal oxide powder of the present invention, the metal oxide powder is synthesized while heating the recovery means.
By a simple method of solid-phase separation of the obtained metal oxide powder, extremely high-purity metal oxide particle powder containing no halogen element such as fluorine and chlorine or NO _x can be obtained.

Therefore, the metal oxide powder obtained by the method of the present invention can be effectively used as a raw material for the semiconductor industry such as a semiconductor encapsulant which requires particularly high purity.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus used in an example.

The synthesized silica powder by Figure 2 the metal powder combustion method, the relationship between the adsorption concentration of NO _x recovery temperature and the silica powder is a graph showing the results of experiments on the concentration of NO _x different combustion exhaust gases.

[Explanation of symbols]

1 is a reaction vessel, 2 is a metal powder supply device, 3 is a burner, 4
Is a recovery device, 23 is a hopper, 32 is a flammable gas supply pipe,
Reference numeral 34 denotes a combustion supporting gas supply pipe, and reference numeral 42 denotes a bag filter.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shuji Tanaka 28-1 Nishifukushima, Nishifukushima, Nakakushijo-gun, Niigata Pref. No. 1-2-22, Admatex Co., Ltd. (56) References JP-A-2-217308 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 13/32 C01B 33 / 18 C01F 5/04 C01F 7/42 C01G 23/047 C01G 25/02

Claims (1)

(57) [Claims] The method according to claim 1 to a metal powder is supplied together with the carrier gas into the reaction vessel under an oxidizing atmosphere to burn the metal powder in the reaction vessel, the synthesis of metal oxide powder
And a method for producing a metal oxide powder in which the synthesized metal oxide powder is recovered by a recovery means , wherein the synthesized metal oxide powder is heated while heating the recovery means.
A method for producing a metal oxide powder, comprising performing solid-vapor separation .