JP5994572B2 - Method for producing silicon oxide powder - Google Patents

Description

  The present invention relates to a method for producing silicon oxide powder by using high-frequency plasma generated at atmospheric pressure or near pressure by an electrodeless high-frequency induction method using inexpensive silicon dioxide powder as a raw material.

  2. Description of the Related Art Conventionally, silicon oxide powder is known to be used as a deposition raw material for, for example, an antireflection protective film for optical lenses and a gas barrier film for food packaging. Recently, silicon oxide powder is expected as a raw material for a negative electrode material of a lithium ion battery, a transparent conductive film, a silicon nanocrystal, and the like. Various techniques have been disclosed so far for the method for producing the silicon oxide powder (see, for example, Patent Documents 1 to 4).

In Patent Document 1, mixed raw material powder containing silicon dioxide powder is heated to 1100 to 1600 ° C. under inert gas or reduced pressure to generate silicon oxide gas, and this silicon oxide gas is deposited on the cooled substrate surface. Later, a method for producing a silicon oxide powder for recovering the silicon oxide precipitate is disclosed. In this method for producing silicon oxide powder, the mixed raw material powder is a mixture of silicon dioxide powder and metal silicon powder, the degree of mixing is 0.9 or more, and the bulk density is 0.3 g / cm ³ or more. . The specific surface area of the silicon dioxide powder is 50 m ² / g or more, and the specific surface area of the metal silicon powder is 0.5 m ² / g or more. The substrate surface is cooled to 200 to 500 ° C. In addition, a liquid such as water or a heat medium, or a gas such as air or nitrogen is used as the refrigerant, and a high melting point metal such as stainless steel, molybdenum, tungsten, or the like is used as the substrate in terms of workability. Further, the silicon oxide powder deposited on the substrate is recovered by scraping or the like.

Further, in Patent Document 2, a mixed raw material powder containing at least silicon dioxide powder is heated in a temperature range of 1100 to 1600 ° C. under an inert gas or reduced pressure to generate silicon oxide gas, and the surface of the substrate cooled by silicon oxide gas. Discloses a method for producing silicon oxide powder to be precipitated. In this method for producing silicon oxide powder, the temperature of the substrate surface is 100 to 400 ° C., and the vapor concentration of silicon oxide gas is 0.5 to 15 g / m ³ . Moreover, the obtained silicon oxide powder is porous, its pore average diameter is 0.5 to 20 nm, its pore volume is 0.005 to 0.2 cm ³ / g, and its specific surface area is 5 ˜300 m ² / g. The silicon oxide powder is a silicon oxide powder represented by the general formula SiOx, and the range of X is 0.9 or more and 1.8 or less. On the other hand, as a raw material, a mixture of silicon dioxide powder and a powder for reducing it is used, and specific reducing powders include metal silicon compounds and carbon-containing powders. Property and yield can be increased. Further, the silicon oxide gas comes into contact with the cooled substrate and is cooled, whereby silicon oxide powder is deposited on the substrate. In addition, a liquid such as water or a heat medium, or a gas such as air or nitrogen is used as the refrigerant, and a high melting point metal such as stainless steel, molybdenum, tungsten, or the like is used as the substrate in terms of workability. Further, the silicon oxide powder deposited on the substrate is recovered by scraping or the like, and is pulverized by means such as the recovered silicon oxide powder ball mill.

In Patent Document 3, thermal plasma of a mixed gas in which argon and hydrogen are mixed so as to have a volume ratio of (15: 1) to (4: 1) is generated in a thermal plasma apparatus. Disclosed is a method for producing silicon lower oxide particles by decomposing silica powder with plasma to obtain silicon lower oxide particles represented by the general formula SiOx (X is greater than 1.0 and 1.6 or less). Has been. In this method for producing silicon lower oxide particles, after the silica powder is decomposed by thermal plasma, the surface-treated silicon lower oxide particles are obtained by introducing a surface treating agent gas into the thermal plasma apparatus. Further, the surface treatment agent gas is one or both of a silazane compound gas and a silane coupling agent gas. In the method for producing silicon lower oxide particles thus configured, first, the air in the chamber is exhausted by a vacuum pump to adjust the pressure in the chamber to about 0.13 to 66.5 kPa, and then the heat Argon gas and hydrogen gas are respectively introduced from the argon gas introduction pipe and the hydrogen gas introduction pipe to the plasma generation unit, and DC power of a predetermined output is applied, and the volume ratio is (15: 1) to (4: 1). A thermal plasma jet in which the mixed gas of argon and hydrogen mixed so as to have a temperature of about 10,000 ° C. is generated, and further, silica powder as a raw material is introduced from a raw material introduction tube together with argon gas, Erupt inside. As a result, the raw silica (SiO ₂ ) particles are decomposed to the atomic level by the thermal plasma of the mixed gas, and Si, O, and SiO gases are generated. These Si, O, and SiO gases are transferred from the plasma to the inner wall of the chamber. And is rapidly cooled to produce SiOx particles.

  Further, Patent Document 4 discloses that a silicon dioxide powder is dispersed in a liquid substance containing carbon, further added with water to form a slurry, and the slurry is formed into droplets to form a thermal plasma flame containing no oxygen. A method for producing silicon monoxide fine particles to be supplied to the company is disclosed. In this method for producing silicon monoxide particles, the amount of silicon dioxide powder is 10 to 65% by mass with respect to the total amount of the liquid substance containing silicon dioxide powder and carbon, and the amount of the liquid substance containing carbon is The amount is 90 to 35% by mass with respect to the total amount of the liquid substance containing silicon dioxide powder and carbon, and the amount of water is 10 to 10% with respect to the total amount of the liquid substance containing silicon dioxide powder and carbon. 40% by mass. The liquid substance containing carbon is alcohol, ketone, kerosene, octane or gasoline, and the thermal plasma flame is derived from at least one gas of hydrogen, helium and argon. Further, the silicon monoxide fine particles are obtained by dispersing silicon dioxide powder in a liquid substance containing carbon, adding water to make a slurry, and making the slurry into droplets in a thermal plasma flame not containing oxygen. Produced by supplying.

Japanese Patent No. 3824047 (Claims 1 to 4, paragraphs [0021] and [0022]) JP 2007-099621 A (claims 1 to 3, paragraphs [0014], [0021], [0022], [0026]) JP 2011-079695 A (Claims 1 to 3, paragraph [0016]) JP, 2011-168212, A (claims 1-5)

  However, in the conventional methods for producing silicon oxide powders disclosed in Patent Documents 1 and 2, silicon oxide heats a mixed raw material powder containing silicon dioxide powder to a high temperature of 1100 to 1600 ° C. under an inert gas or reduced pressure. Then, the silicon oxide gas is generated, and after the silicon oxide gas is deposited on the cooled substrate surface, the silicon oxide deposit is collected and then batch production is performed. . Moreover, in the manufacturing method of the silicon oxide powder shown by the said conventional patent documents 1 and 2, a part of silicon oxide gas generated by the reaction of silicon dioxide and metal silicon is inevitably cooled to 100 to 500 ° C. There is also a problem that some silicon oxide powder does not precipitate on the surface of the substrate and the recovery rate of the silicon oxide powder is low. From the above, the conventional silicon oxide powder manufacturing methods disclosed in Patent Documents 1 and 2 have a problem that the manufacturing cost of silicon oxide increases.

  Moreover, in the manufacturing method of the silicon oxide powder shown by the said conventional patent documents 1 and 2, the silicon oxide which precipitated on the board | substrates, such as stainless steel, molybdenum, and tungsten cooled to 100-500 degreeC is scraped off and collect | recovered. Therefore, there is a problem that impurities such as iron are inevitably mixed. In the conventional method for producing silicon oxide powder shown in Patent Document 2, the collected silicon oxide is pulverized by a ball mill or the like. There was a problem that more impurities such as iron were mixed. Furthermore, in the conventional methods for producing silicon oxide powders disclosed in Patent Documents 1 and 2, it is necessary to adjust the particle size of metal silicon used to increase the reactivity with silicon dioxide to 1 μm or less, In order to efficiently adjust the particle size of metal silicon such as grades, ceramics grades, and semiconductor grades from millimeter-sized coarse particles to fine particles of 1 μm or less, it is necessary to go through several particle size adjustment processes. There is also a problem that a relatively large number of man-hours are required to adjust the particle size.

  On the other hand, in the conventional method for producing silicon lower oxide particles disclosed in Patent Document 3, argon gas and hydrogen gas are introduced into the thermal plasma generation unit, DC power of a predetermined output is applied, A thermal plasma jet having a mixed gas temperature of about 10,000 ° C. is generated, and since the generation method of this thermal plasma jet is a direct current arc discharge method having electrodes, impurities from electrode materials such as tungsten and iron are generated. There was a problem of being mixed into silicon lower oxide particles. In addition, in the conventional method for producing fine silicon monoxide particles disclosed in Patent Document 4, silicon dioxide powder is dispersed in a liquid substance containing carbon such as alcohol or ketone, and water is further added to form a slurry. By making the slurry into droplets and supplying them into a thermal plasma flame that does not contain oxygen, the silicon monoxide fine particles are produced. Therefore, liquid substances containing carbon and water are evaporated and decomposed. In addition, since the heat energy of the high-frequency plasma is consumed, there is a problem that silicon oxide cannot be produced efficiently.

  The first object of the present invention is to be able to continuously produce silicon oxide powder, to collect all the produced silicon oxide powder, and to use liquid substance containing carbon and water by high frequency plasma. Therefore, it is not necessary to evaporate and decompose, thereby providing a method for producing silicon oxide powder that can improve the productivity of silicon oxide powder. The second object of the present invention is to suppress the entry of impurities such as iron and tungsten into the silicon oxide powder and eliminate the need for using metal silicon that requires a relatively large number of man-hours to adjust the particle size. The object is to provide a method for producing silicon powder.

A first aspect of the present invention is a method for producing silicon oxide powder represented by amorphous SiOx using silicon dioxide powder as a raw material in high-frequency plasma generated by an electrodeless high-frequency dielectric method, in the range of oxygen content X is 1 to 1.8 of silicon oxide powder, a method for producing a silicon oxide powder, wherein the impurity concentration of the silicon oxide powder is at most 11 pp m.

The second aspect of the present invention is an invention based on the first aspect, further adjusts the pressure of the high-frequency plasma generating atmosphere to a range of 0.05 to 0.12 MPa, and sets the high-frequency output of the high-frequency plasma to A. (W) When the supply rate of silicon dioxide powder is B (kg / hour), the A / B is adjusted to be 1.0 × 10 ⁴ (W · hour / kg) or more, and the high-frequency plasma is adjusted. Is generated.

  A third aspect of the present invention is the invention based on the first aspect, and is characterized in that the average particle diameter of the silicon oxide powder is in the range of 0.002 to 1 μm on a volume basis.

  A fourth aspect of the present invention is the invention based on the first aspect, wherein the silicon dioxide powder is fumed silica, or the fumed silica is used as a raw material and the average particle size is 0 on a volume basis. .Granulated powder in the range of 1 to 80 μm.

  A fifth aspect of the present invention is an invention based on the fourth aspect, wherein the granulated powder is further dried at a temperature in the range of 100 to 1100 ° C. after slurrying or gelling fumed silica. It is characterized by being obtained.

  In the method for producing silicon oxide powder according to the first aspect of the present invention, an inexpensive silicon dioxide powder is used as a raw material, and the silicon dioxide powder is evaporated in a high-frequency plasma generated by an electrodeless high-frequency dielectric method. The silicon oxide powder was produced by generating a silicon oxide gas and quenching it in a gas flow, so that the oxygen content X of the silicon oxide powder represented by SiOx is in the range of 1 to 1.8. The silicon oxide powder obtained above becomes amorphous. In addition, silicon oxide is heated after the mixed raw material powder containing silicon dioxide powder is heated under an inert gas or under reduced pressure to generate silicon oxide gas, and this silicon oxide gas is deposited on the cooled substrate surface. Compared with the conventional method for producing silicon oxide powder with low productivity because it is produced in a batch system in which the product is recovered, in the present invention, silicon oxide powder can be produced continuously. The productivity of powder can be improved. In addition, some silicon oxide gas generated by the reaction between silicon dioxide and metal silicon inevitably does not precipitate as silicon oxide on the surface of the substrate cooled to 100 to 500 ° C., and the silicon oxide powder recovery rate Compared with the conventional method for producing silicon oxide powder, which has a problem of being low, in the present invention, all produced silicon oxide powder can be recovered, so that productivity of silicon oxide powder can be improved. Furthermore, conventional silicon monoxide fine particles have a problem in that silicon oxide cannot be produced efficiently because much of the heat energy of high-frequency plasma is consumed to evaporate and decompose liquid substances containing water and water. Compared with this manufacturing method, in the present invention, since it is not necessary to evaporate and decompose a liquid substance containing carbon or water by high-frequency plasma, the productivity of silicon oxide powder can be improved.

On the other hand, a conventional silicon oxide powder in which silicon oxide deposited on a substrate such as stainless steel, molybdenum or tungsten is recovered by scraping or the like, or the recovered silicon oxide is pulverized by a ball mill or the like to adjust the particle size. Compared with this manufacturing method, in the present invention, the impurity concentration is as low as 11 pp m at the maximum. When silicon oxide containing the above impurities (silicon lower oxide) is used as a vapor deposition material, it causes abnormal discharge (arc spot) when forming a silicon oxide film on the gas barrier film, and this abnormal discharge (arc spot) When gas is generated, non-gasified silicon oxide adheres to the gas barrier film, so that a non-uniform surface of silicon oxide such as a convex portion or a pinhole is generated on the gas film, thereby reducing gas barrier properties. Compared with the conventional method for producing silicon lower oxide particles having a point, since the impurity concentration of silicon oxide powder is 11 pp m at the maximum in the present invention, when silicon oxide powder is used as a gas barrier film, A deposited film having good gas barrier properties can be formed. Further, when silicon oxide containing the above impurities (silicon lower oxide) is used as the negative electrode active material of a lithium ion secondary battery, the irreversible capacity at the first charge / discharge is increased due to iron or tungsten in the silicon oxide, resulting in a cycle. Compared with the conventional method for producing silicon lower oxide particles having a problem that the characteristics deteriorate, in the present invention, since the impurity concentration of the silicon oxide powder is 11 pp m at the maximum, the silicon oxide powder is replaced with lithium ion. When used as a negative electrode active material for a secondary battery, it is possible to reduce the incapacity during initial charge / discharge, thereby improving cycle characteristics. Furthermore, it is necessary to adjust the particle size of the metal silicon used to increase the reactivity with silicon dioxide to 1 μm or less, and in order to efficiently adjust the particle size of the metal silicon from millimeter-sized coarse particles to 1 μm or less, Compared with the conventional method for producing silicon oxide powder, which requires a number of steps for adjusting the particle size and requires a relatively large number of steps to adjust the particle size of the metal silicon, Since it is not necessary to use metallic silicon, the man-hour for adjusting the particle size of metallic silicon can be eliminated.

In the method for producing silicon oxide powder according to the second aspect of the present invention, the pressure of the atmosphere in which high-frequency plasma is generated is adjusted to a range of 0.05 to 0.12 MPa. Heating can be efficiently performed in a short time, and the reaction rate of the silicon dioxide powder can be exponentially increased in a high temperature region. Further, when the high frequency output of the high frequency plasma is A (W) and the supply rate of the silicon dioxide powder is B (kg / hour), A / B is 1.0 × 10 ⁴ (W · hour / kg) or more. Thus, high frequency plasma is generated. When the A / B is smaller than 1.0 × 10 ⁴ (W · hour / kg), the energy content of the high-frequency plasma applied to the silicon dioxide powder is small, so that the oxygen content X of the silicon oxide powder represented by SiOx is stable. It will be larger than 1.8 without. On the other hand, even if the A / B is increased to increase the energy of the high-frequency plasma applied to the silicon dioxide powder, the silicon oxide powder represented by SiOx has an oxygen content X smaller than 1 because of the reaction rate. Hardly produces. For these reasons, the oxygen content X of the silicon oxide powder represented by SiOx can be controlled in the range of 1 to 1.8.

In the method for producing silicon oxide powder according to the third aspect of the present invention, since the average particle size of the silicon oxide powder is in the range of 0.002 to 1 μm on a volume basis, silicon oxide deposited on a substrate such as stainless steel is used. There is no need to collect by scraping or the like, and there is no need to adjust the particle size by pulverizing the collected silicon oxide with a ball mill or the like, so that impurities are not mixed into the silicon oxide powder. As a result, the impurity concentration in the silicon oxide powder is as low as 11 pp m at the maximum.

In the method for producing silicon oxide powder according to the fourth aspect of the present invention, fumed silica used as silicon dioxide powder is highly pure and inexpensive, and the average particle size of fumed silica is as small as 5 to 50 nm. Since the specific surface area of dosilica is as wide as 10 to 400 m ² / g, fumed silica is susceptible to thermal energy in high-frequency plasma and is likely to evaporate. As a result, the silicon oxide powder can be produced efficiently. Further, the same effect as described above can be obtained even when a granulated powder using fumed silica as a raw material and having an average particle size in the range of 0.1 to 80 μm on a volume basis is used.

  Since the bulk density of fumed silica is as extremely low as 20 to 100 g / liter, it is difficult to stably supply a relatively large amount of fumed silica into the high-frequency plasma. For this reason, in the method for producing silicon oxide powder according to the fifth aspect of the present invention, fumed silica is slurried or gelled and then dried at a temperature in the range of 100 to 1100 ° C. Since the granulated powder is 0.1 to 80 μm on the basis, a relatively large amount of fumed silica can be stably supplied into the high-frequency plasma. As a result, since the amount of evaporation per unit time of the fumed silica granulated powder can be increased, the production amount per unit time of the silicon oxide powder can be increased.

It is a schematic sectional drawing of the high frequency plasma apparatus used for manufacture of the silicon oxide powder of embodiment of this invention. It is a schematic sectional drawing which shows the state which mixes the raw material fumed silica and ion-exchange water with a continuous kneader, and prepares the slurry of fumed silica.

  Next, an embodiment for carrying out the present invention will be described with reference to the drawings. As shown in FIG. 1, silicon oxide powder 11 generates high-frequency plasma 12 by a high-frequency dielectric method using an electrodeless high-frequency plasma apparatus 10, and supplies silicon dioxide powder as a raw material into this high-frequency plasma 12. It is manufactured by. The electrodeless high-frequency plasma apparatus 10 includes a plasma torch 13 that generates high-frequency plasma 12, a chamber 14 that is a reaction cylinder provided at the lower portion of the plasma torch 13, and a chamber 14 that is provided at the lower portion of the chamber 14. And a collection container 16 for collecting the silicon oxide powder 11 produced therein. The plasma torch 13 includes a quartz tube 13a having an open bottom surface and communicating with the inside of the chamber 14, an open top surface, a high-frequency induction coil 13b around which the quartz tube 13a is wound, and a lid for sealing the top surface of the quartz tube 13a. And a body 13c. A raw material supply pipe 17 is inserted through the lid 13c, and a gas introduction pipe 18 is connected thereto. A gas discharge port 14 a for discharging the gas in the chamber 14 is provided on the upper side surface of the chamber 14.

In the high-frequency plasma apparatus 10, one or more mixed gases selected from the group consisting of argon gas, helium gas, hydrogen gas, nitrogen gas and oxygen gas are introduced from the gas introduction tube 18 into the quartz tube 13a. When a predetermined high frequency power is supplied to the high frequency induction coil 13b, the high frequency plasma 12 is generated from the quartz tube 13a to the chamber 14, and the silicon dioxide powder as the raw material powder passes through the raw material supply tube 17 in the high frequency plasma 40. To be supplied. When the high frequency output of the high frequency plasma 12 is A (W) and the supply rate of the silicon dioxide powder is B (kg / hour), A / B is 1.0 × 10 ⁴ (W · hour / kg) or more. Then, the high frequency plasma 12 is generated. Here, the A / B is limited to 1.0 × 10 ⁴ (W · hour / kg) or more when the A / B is smaller than 1.0 × 10 ⁴ (W · hour / kg). This is because the oxygen content X of the silicon oxide powder represented by SiOx becomes unstable and becomes higher than 1.8 because the energy of the high-frequency plasma applied to the powder is small. The pressure of the atmosphere in which the high-frequency plasma 12 is generated is adjusted to a range of 0.05 to 0.12 MPa, preferably 0.07 to 0.10 MPa, in terms of total pressure (pressure of the entire mixed gas). Here, the reason why the pressure of the atmosphere in which the high-frequency plasma 12 is generated is limited to 0.05 MPa or more in terms of the total pressure is that not only electrons but also heavy particles such as ions and atoms become high temperature. This is because the silicon dioxide powder can be heated efficiently in a short time, and an exponential increase in the reaction rate of the silicon dioxide powder in a high temperature region can be expected. In addition, the pressure of the atmosphere in which the high-frequency plasma 12 is generated is limited to 0.12 MPa or less in terms of the total pressure. When A / B exceeds 0.12 MPa, the temperature of the mixed gas heated by the high-frequency plasma becomes too high, This is because the surface of the chamber 14 is melted.

On the other hand, as the raw material silicon dioxide powder, fumed silica is used, or the fumed silica is used as a raw material, and the average particle size is in the range of 0.1 to 80 μm on a volume basis, preferably in the range of 0.5 to 30 μm. It is preferable to use the granulated powder in Here, the average particle diameter of the fumed silica granulated powder was limited to the range of 0.1 to 80 μm on a volume basis. If the average particle diameter is less than 0.1 μm, the bulk density of the fumed silica granulated powder is low. However, the silicon dioxide powder has a low thermal conductivity, so if it exceeds 80 μm, heat will reach the center of the fumed silica granulated powder. This is because the temperature does not rise and the temperature does not rise. The average particle size of fumed silica is in the range of 5 to 50 nm, and the specific surface area of fumed silica is in the range of 10 to 400 m ² / g. When fumed silica is used as the silicon dioxide powder, the fumed silica is highly pure and inexpensive, the average particle size of the fumed silica is as small as 5 to 50 nm, and the specific surface area of the fumed silica is 10 to 400 m ² / Since it is relatively wide as g, fumed silica is easily evaporated by receiving thermal energy in high-frequency plasma. As a result, the silicon oxide powder can be produced efficiently.

  On the other hand, when fumed silica granulated powder is used as the silicon dioxide powder, the fumed silica is slurried or gelled and then dried at a temperature in the range of 100 to 1100 ° C, preferably in the range of 150 to 400 ° C. Is preferred. Here, when fumed silica was gelled, the gelled fumed silica was dried by holding at a temperature of 200 to 400 ° C. for 6 to 24 hours in an argon gas atmosphere, a nitrogen gas atmosphere, dry air, or the like. Thereafter, a fumed silica granulated powder can be obtained by pulverizing with a bead mill or the like so that the average particle diameter is in the above range. When fumed silica is slurried, hot air at a temperature of 150 to 200 ° C. is applied by a spray dryer while dripping the slurry of fumed silica onto a rotating disk in an argon gas atmosphere, a nitrogen gas atmosphere, dry air, or the like. By spraying and drying, fumed silica having an average particle diameter in the predetermined range can be obtained. Further, when fumed silica is slurried, the slurried fumed silica is kept at a temperature of 400 to 1100 ° C. for 20 minutes to 6 hours in an argon gas atmosphere, a nitrogen gas atmosphere, dry air, etc., and dried. By pulverizing with a roll crusher or the like, and further classifying the pulverized product with a vibration sieve or the like, fumed silica having an average particle size in the predetermined range can be obtained.

  Note that the amount of silicon oxide powder produced per unit time can be increased by using fumed silica granulated powder rather than using fumed silica. The reason is as follows. Since the bulk density of fumed silica is as extremely low as 20 to 100 g / liter, it is difficult to stably supply a relatively large amount of fumed silica into the high-frequency plasma. For this reason, fumed silica is slurried or gelled as described above, and then dried at a predetermined temperature to obtain a granulated powder having a predetermined average particle diameter. An amount of fumed silica can be stably supplied. As a result, since the amount of evaporation per unit time of the fumed silica granulated powder can be increased, the production amount per unit time of the silicon oxide powder can be increased.

  In the manufacturing method of the silicon oxide powder thus configured, an inexpensive silicon dioxide powder is used as a raw material, and the silicon dioxide powder is evaporated in a high-frequency plasma generated by an electrodeless high-frequency dielectric method. Since silicon oxide powder was produced by generating silicon oxide gas and rapidly cooling it in a gas flow, the oxygen content X of the silicon oxide powder represented by SiOx was in the range of 1 to 1.8. The obtained silicon oxide powder becomes amorphous. Specifically, when the high-frequency plasma is generated by the high-frequency dielectric method using the electrodeless high-frequency plasma apparatus, the temperature of the high-frequency plasma becomes about 10,000 K. Therefore, the silicon dioxide powder in the high-frequency plasma evaporates. Thus, silicon oxide gas is obtained, and a part of the silicon oxide gas is in a plasma state of silicon oxide, and silicon and oxygen decomposed from the silicon oxide gas are in a plasma state. These silicon oxide gas, plasma silicon oxide, and plasma silicon and oxygen are used to protect the high frequency plasma apparatus from the high frequency plasma gas generated by the electrodeless high frequency induction method and from these high frequency plasmas. Is rapidly cooled by the sheath gas flowing into the fine particle silicon oxide powder having an average particle diameter of 2 to 1000 nm on a volume basis. Accordingly, the obtained fine silicon oxide powder becomes amorphous. Examples of the sheath gas include argon gas, nitrogen gas, and hydrogen gas.

On the other hand, since the pressure of the atmosphere in which high-frequency plasma is generated is adjusted to a range of 0.05 to 0.12 MPa, the energy density of the high-frequency plasma is large, and silicon dioxide powder can be efficiently heated in a short time, and silicon dioxide in a high temperature region. The reaction rate of the powder can be increased exponentially. Further, when the high frequency output of the high frequency plasma is A (W) and the supply rate of the silicon dioxide powder is B (kg / hour), A / B is 1.0 × 10 ⁴ (W · hour / kg) or more. Since the high frequency plasma is generated by adjusting so that the energy of the high frequency plasma applied to the silicon dioxide powder increases, the oxygen content X of the silicon oxide powder represented by SiOx is stably smaller than 1.8. For this reason, the oxygen content X (oxygen valence X) of the silicon oxide powder represented by SiOx can be controlled in the range of 1 to 1.8.

In the silicon oxide powder produced in this way, the average particle size is in the range of 0.002 to 1 μm on a volume basis, so it is necessary to collect silicon oxide deposited on a stainless steel substrate by scraping or the like. In addition, there is no need to adjust the particle size by pulverizing the recovered silicon oxide with a ball mill or the like, and there is little mixing of impurities into the silicon oxide powder. As a result, the impurity concentration in the silicon oxide powder is as low as 11 pp m at the maximum. In addition, it is preferable that the average particle diameter of silicon oxide powder exists in the range of 0.05-0.5 micrometer on a volume basis, and it is preferable that the impurity concentration in silicon oxide powder is less than 1 ppm at maximum.

  In the present specification, the specific surface area of fumed silica is a value measured by a BET three-point method using a specific surface area measuring device (model name: AUTOSORB-iQ2, manufactured by QUANTACHROME). Here, the BET three-point method is a method for obtaining a slope from a nitrogen adsorption amount with respect to three relative pressures and obtaining a specific surface area value from the BET equation. Further, the measurement of the nitrogen adsorption amount is performed after the deaeration treatment in which the temperature is maintained at 150 ° C. for 60 minutes. In this specification, the average particle size of the silicon oxide powder having an average particle size of less than 0.01 μm on a volume basis is prepared by dispersing the silicon oxide powder in ion-exchanged water subjected to ultrasonic waves to prepare a slurry or gel. Then, using this slurry or gel, a replica film was prepared by a freeze-fracture replica method, and this replica film was observed with a transmission electron microscope (TEM) (model name: JEM-1400 type, manufactured by JEOL Ltd.), This is a value obtained by measuring the particle size of 100 particles of silicon oxide powder and calculating the average value of these. Further, in this specification, the average particle size of fumed silica, fumed silica granulated powder, silicon oxide powder, etc. is measured using a laser diffraction particle size distribution analyzer (model name: MS-3000, manufactured by Malvern). Thus, the average particle diameter on a volume basis was measured three times, and the average value was calculated by calculating these average values.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, fumed silica having a specific surface area of 30 m ² / g and an average particle size of 0.04 μm on a volume basis was prepared. Next, as shown in FIG. 1, an electrodeless high frequency plasma apparatus 10 was used to generate a high frequency plasma 12 by a high frequency dielectric method under the conditions shown in Table 1. Further, the fumed silica was put into the generated high-frequency plasma to produce amorphous silicon oxide powder 11 (SiOx). Specifically, first, argon gas as a working gas is introduced from the gas introduction pipe 18 of the electrodeless high-frequency plasma apparatus 10 at a flow rate shown in Table 1, and the frequencies shown in Table 1 are applied to the high-frequency induction coil 13 b of the plasma torch 13. In addition, high-frequency plasma 12 was generated from the inside of the quartz tube 13a to the inside 14 of the chamber by supplying high-frequency power of output. Next, after the high-frequency plasma 12 was stabilized, hydrogen was gradually introduced until the flow rate shown in Table 1 was reached to generate the high-frequency plasma 12 made of argon-hydrogen plasma. Further, the fumed silica was put into a high-frequency plasma 12 made of argon-hydrogen plasma to produce amorphous silicon oxide powder 11 (SiOx). The silicon oxide powder 11 (SiOx) generated in the high-frequency plasma 12 dropped into the recovery container 16 and was recovered. A part of the silicon oxide powder was discharged together with the exhaust gas from the discharge port 14a and recovered by a bag filter (not shown). The silicon oxide powder 11 collected in the collection container 16 and the bag filter was taken as Example 1.

<Example 2>
First, 13 mol of ion-exchanged water was prepared for 1 mol of fumed silica having a specific surface area of 90 m ² / g. Next, this ion-exchanged water was put in a container, fumed silica was added while stirring while maintaining the temperature at 25 ° C. in a nitrogen atmosphere, and then stirring was continued for 3 hours to prepare a siliceous gel. . Next, this siliceous gel was placed in a Pyrex (registered trademark of Corning) glass container and dried at a temperature of 200 ° C. for 24 hours under an argon atmosphere to obtain a dried powder of fumed silica. . Further, the dried powder of fumed silica was pulverized with a bead mill to obtain a granulated powder of fumed silica. Here, the dry fumed silica powder is pulverized by a bead mill. The dry fumed silica powder and silica beads are placed in a quartz cylindrical container, and the cylindrical container is rotated at a rotation speed of 30 rpm for 24 hours. Was done.

  Subsequently, as shown in FIG. 1, an electrodeless high frequency plasma apparatus was used to generate high frequency plasma by a high frequency dielectric method under the conditions shown in Table 1. Further, the fumed silica granulated powder was introduced into the generated high-frequency plasma to produce amorphous silicon oxide powder 11 (SiOx). Specifically, first, argon gas as a working gas is introduced from the gas introduction pipe 18 of the electrodeless high-frequency plasma apparatus 10 at a flow rate shown in Table 1, and the frequencies shown in Table 1 are applied to the high-frequency induction coil 13 b of the plasma torch 13. In addition, high-frequency plasma 12 was generated from the inside of the quartz tube 13 a to the inside of the chamber 14 by supplying high-frequency power of output. Next, after the high-frequency plasma 12 was stabilized, hydrogen gas and helium gas were gradually introduced until the flow rates shown in Table 1 were reached, thereby generating the high-frequency plasma 12 composed of argon-hydrogen-helium plasma. Further, the fumed silica granulated powder was put into a high-frequency plasma 12 composed of argon-hydrogen-helium plasma to produce amorphous silicon oxide powder 11 (SiOx). The silicon oxide powder 11 (SiOx) generated in the high-frequency plasma 12 dropped into the recovery container 16 and was recovered. A part of the silicon oxide powder was discharged together with the exhaust gas from the discharge port 14a and recovered by a bag filter (not shown). The silicon oxide powder 11 collected in the collection container 16 and the bag filter was taken as Example 2.

<Example 3>
First, as shown in FIG. 2, fumed silica having a specific surface area of 200 m ² / g is supplied to a container 51 of a continuous kneading apparatus 50 having a plurality of rotating projecting pieces 54 at a rate of 3 kg / hour, and 15 ° C. Ion exchange water was supplied at a rate of 7 kg / hour and mixed to prepare slurry 55 containing 30% by mass of fumed silica. The continuous kneading apparatus 50 is rotated so that a cylindrical container 51 having a bottom plate 51 a having an open upper surface is inserted in the center of the bottom plate 51 a so as to extend in the vertical direction and the upper end is located in the upper part of the container 51. A rotating shaft 52 that can be provided, a disk-shaped rotating plate 53 fixed to the upper end of the rotating shaft 52, and a lower surface of the rotating plate 53 with predetermined intervals in the radial direction and the circumferential direction, respectively. And a plurality of columnar protrusions 54 projecting downward. Between the bottom plate 51a and the rotating shaft 52, there are a seal member 56 that prevents leakage of the slurry 55 in the container 51, and a pair of bearings 57, 57 that hold the rotating shaft 52 rotatably with respect to the bottom plate 51a. Intervened. Also, reference numeral 58 in FIG. 2 is a discharge pipe for discharging the slurry 55 in the container 51. Further, reference numeral 59 in FIG. 2 is an open / close valve provided in the discharge pipe 58, and when the open / close valve 59 is opened, the slurry 55 in the container 51 is discharged through the discharge pipe 58. Next, the slurry was granulated by spraying 200 ° C. hot air with a spray dryer while dropping the slurry onto a pin disk having a diameter of 100 mm rotating at a rotational speed of 12500 rpm in air having a humidity of 80% or more. As a result, a spherical fumed silica granulated powder having open pores and an average particle diameter of 7 μm on a volume basis was obtained.

  Subsequently, as shown in FIG. 1, an electrodeless high frequency plasma apparatus was used to generate high frequency plasma by a high frequency dielectric method under the conditions shown in Table 1. Further, the fumed silica granulated powder was introduced into the generated high-frequency plasma to produce amorphous silicon oxide powder 11 (SiOx). Specifically, first, argon gas as a working gas is introduced from the gas introduction pipe 18 of the electrodeless high-frequency plasma apparatus 10 at a flow rate shown in Table 1, and the frequencies shown in Table 1 are applied to the high-frequency induction coil 13 b of the plasma torch 13. In addition, high-frequency plasma 12 was generated from the inside of the quartz tube 13 a to the inside of the chamber 14 by supplying high-frequency power of output. Next, after the high-frequency plasma 12 was stabilized, hydrogen gas and helium gas were gradually introduced until the flow rates shown in Table 1 were reached, thereby generating the high-frequency plasma 12 composed of argon-hydrogen-helium plasma. Further, the fumed silica granulated powder was put into a high-frequency plasma 12 composed of argon-hydrogen-helium plasma to produce amorphous silicon oxide powder 11 (SiOx). The silicon oxide powder 11 (SiOx) generated in the high-frequency plasma 12 dropped into the recovery container 16 and was recovered. A part of the silicon oxide powder was discharged together with the exhaust gas from the discharge port 14a and recovered by a bag filter (not shown). The silicon oxide powder 11 collected in the collection container 16 and the bag filter was taken as Example 3.

<Example 4>
First, as shown in FIG. 2, fumed silica having a specific surface area of 300 m ² / g is supplied to a container 51 of a continuous kneading apparatus 50 having a plurality of rotating projecting pieces 54 at a rate of 10 kg / hr. Ion exchange water was supplied at a rate of 10 kg / hour and mixed to prepare slurry 55 containing 50% by mass of fumed silica. Next, this slurry was put in a quartz container, and dried at a temperature of 1100 ° C. for 6 hours in an air atmosphere to obtain a dried fumed silica powder. Further, the dried fumed silica powder was taken out of the quartz container and pulverized using a roll crusher. At this time, the roll gap of the roll crusher was adjusted to 0.2 mm, and the roll rotation speed was adjusted to 50 rpm. The pulverized dry powder was classified using a vibrating sieve having an opening of 120 μm to obtain a fumed silica granulated powder having an average particle size of 56 μm on a volume basis.

  Subsequently, as shown in FIG. 1, an electrodeless high frequency plasma apparatus was used to generate high frequency plasma by a high frequency dielectric method under the conditions shown in Table 1. Further, the fumed silica granulated powder was introduced into the generated high-frequency plasma to produce amorphous silicon oxide powder 11 (SiOx). Specifically, first, argon gas as a working gas is introduced from the gas introduction pipe 18 of the electrodeless high-frequency plasma apparatus 10 at a flow rate shown in Table 1, and the frequencies shown in Table 1 are applied to the high-frequency induction coil 13 b of the plasma torch 13. In addition, high-frequency plasma 12 was generated from the inside of the quartz tube 13 a to the inside of the chamber 14 by supplying high-frequency power of output. Next, after the high-frequency plasma 12 was stabilized, hydrogen gas was gradually introduced until the flow rate shown in Table 1 was reached to generate the high-frequency plasma 12 made of argon-hydrogen plasma. Further, the fumed silica granulated powder was put into a high-frequency plasma 12 made of argon-hydrogen plasma to produce amorphous silicon oxide powder 11 (SiOx). The silicon oxide powder 11 (SiOx) generated in the high-frequency plasma 12 dropped into the recovery container 16 and was recovered. A part of the silicon oxide powder was discharged together with the exhaust gas from the discharge port 14a and recovered by a bag filter (not shown). The silicon oxide powder 11 collected in the collection container 16 and the bag filter was taken as Example 4.

<Comparative Example 1>
First, 100 g of fumed silica having a specific surface area of 300 m ² / g and 50 g of metal silicon powder having a specific surface area of 2 m ² / g and a purity of 99.8% are placed in a stainless steel container. Was mixed in a dry powder mixing apparatus for 3 hours at a rotation speed of 30 rpm. Next, this mixed powder was put in a tungsten container and evacuated to a pressure of 100 Pa or less, and then heated to 1300 ° C. and held at this temperature for 10 hours to generate silicon oxide gas. The silicon oxide gas was introduced onto a stainless steel substrate cooled to 500 ° C., and silicon oxide was deposited on the substrate. Further, the deposited silicon oxide was scraped off from the substrate and then pulverized by a bead mill to obtain a silicon oxide powder. Specifically, silicon oxide powder is obtained by putting the scraped silicon oxide and stainless steel beads in a stainless steel cylindrical container and grinding the cylindrical container by rotating at a rotational speed of 50 rpm for 24 hours. Got. This silicon oxide powder was designated as Comparative Example 1.

<Comparative test 1 and evaluation>
The oxygen content X (oxygen valence X) of the silicon oxide powders (SiOx) of Examples 1 to 4 and Comparative Example 1 was measured by X-ray photoelectron spectroscopy (XPS). Moreover, the average particle diameter of the silicon oxide powders of Examples 1 to 4 and Comparative Example 1 was measured by observation with a transmission electron microscope (TEM). The oxygen content X (oxygen valence X) of the silicon oxide powder (SiOx) was measured using an X-ray photoelectron spectroscopy (XPS) apparatus (model name: model-5600LS, manufactured by ULVAC PHI). The narrow spectrum of the elements detected from the powder was determined by quantitative analysis. The results are shown in Table 1.

なお、表１において、(注１)には、『加熱してガス化した後に、析出させて粉砕することにより、酸化珪素粉末を作製した。』という文が挿入される。

In Table 1, (Note 1) indicates “Silicon oxide powder was produced by heating and gasifying, then precipitating and grinding. Is inserted.

  As is clear from Table 1, in Comparative Example 1, the oxygen content X (oxygen valence X) of the silicon oxide powder (SiOx) was 1.67, whereas in Examples 1 to 4, the silicon oxide powder (SiOx) had silicon oxide. The oxygen content X (oxygen valence X) of the powder (SiOx) was 1.01-1.78. From this, it can be seen that the silicon oxide powders of Examples 1 to 4 have an oxygen content X (oxygen valence X) in the range of 1 to 1.8, similarly to the silicon oxide powder of Comparative Example 1. It was. In Comparative Example 1, the average particle size of the silicon oxide powder was as large as 1.2 μm, whereas in Examples 1 to 4, the average particle size of the silicon oxide powder was 0.003 μm, 0.015 μm, and 0, respectively. It was as small as .325 μm and 0.920 μm. From these facts, it was found that the oxygen content X (oxygen valence X) and the average particle diameter of the silicon oxide powder can be controlled by changing the generation conditions of the electrodeless high-frequency plasma, the supply rate of the raw material, and the like.

<Comparative test 2 and evaluation>
The content of impurities contained in the silicon oxide powders of Examples 1 to 4 and Comparative Example 1 was measured. Specifically, the contents of aluminum (Al), iron (Fe), and nickel (Ni) contained in the silicon oxide powders of Examples 1 to 4 and Comparative Example 1 were measured. The results are shown in Table 2.

  As is clear from Table 2, in Comparative Example 1, the impurities aluminum (Al), iron (Fe), and nickel (Ni) were as high as 17 ppm, 315 ppm, and 45 ppm, respectively, whereas in Examples 1 to 4, Impurities such as aluminum (Al), iron (Fe), and nickel (Ni) were reduced to 0.3 to 0.5 ppm, 0.7 to 8.7 ppm, and 0.1 to 1.8 ppm, respectively.

11 Silicon oxide powder 12 High frequency plasma

Claims (5)

In a high-frequency plasma generated by an electrodeless high-frequency dielectric method, a silicon oxide powder represented by amorphous SiOx is produced using silicon dioxide powder as a raw material,
The oxygen content X of the silicon oxide powder is in the range of 1 to 1.8,
Method for producing a silicon oxide powder in which the impurity concentration of the silicon oxide powder is characterized in that it is a maximum of 11 pp m. The pressure of the high-frequency plasma generation atmosphere is adjusted to a range of 0.05 to 0.12 MPa, the high-frequency output of the high-frequency plasma is A (W), and the supply rate of the silicon dioxide powder is B (kg / hour). The method for producing silicon oxide powder according to claim 1, wherein the high-frequency plasma is generated by adjusting A / B to be 1.0 × 10 ⁴ (W · hour / kg) or more.   The method for producing a silicon oxide powder according to claim 1, wherein an average particle diameter of the silicon oxide powder is in a range of 0.002 to 1 µm on a volume basis.   2. The silicon oxide according to claim 1, wherein the silicon dioxide powder is fumed silica or a granulated powder using the fumed silica as a raw material and having an average particle diameter in the range of 0.1 to 80 μm on a volume basis. Powder manufacturing method.   The manufacturing method of the silicon oxide powder of Claim 4 obtained by drying the said granulated powder at the temperature of the range of 100-1100 degreeC after slurrying or gelatinizing fumed silica.

Images