JP3723022B2 - Method for producing amorphous silica fine particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing amorphous silica fine particles having a high sphericity.
[0002]
[Prior art]
Conventionally, as a general method for producing metal oxide ultrafine particles, JP-B-1-55201 discloses that a chemical flame is formed by a burner in an atmosphere containing oxygen, and the target metal oxide is contained in the chemical flame. There is a disclosure of a production method for synthesizing ultrafine metal oxide particles having a particle diameter of about 5 to 100 nm by introducing a combustible metal powder in an amount capable of forming a dust cloud and burning it.
[0003]
Japanese Patent No. 2600181 discloses that a metal powder constituting a metal oxide and the metal oxide powder are supplied into a reaction vessel together with a carrier gas, and then the metal powder is burned to obtain a metal oxide powder as a raw material. There is disclosed a method for producing a metal oxide in which a metal oxide powder is grown by using a core as a core.
[0004]
[Problems to be solved by the invention]
In the manufacturing method described in the above Japanese Patent Publication No. 1-55201, since the raw material metal silicon is expensive, it is difficult to implement in terms of cost, and the particle diameter of the manufactured amorphous silica fine particles can be controlled in a wide range. There wasn't.
[0005]
Japanese Patent No. 2600181 only specifically describes a method for producing alumina particles, and with the described production method, it is possible to obtain alumina powder having a larger particle diameter than the raw material alumina powder. The manufacture of alumina powder having a particle size smaller than that of the raw material was not described. The sphericity of the produced alumina was not extremely high. Therefore, it was not clear that the production method described in this publication can produce amorphous silica fine particles having characteristics in properties.
[0006]
Amorphous silica fine particles having a high sphericity have various useful uses such as a use as a filler of a sealing agent covering a semiconductor package. In that case, the amorphous silica fine particles preferably have a high sphericity. There has been no method for easily producing amorphous silica fine particles having a high sphericity. Further, the amorphous silica fine particles are required to have various particle sizes depending on applications, and it is desirable that amorphous silica fine particles be obtained with various particle sizes by a simple manufacturing method.
[0007]
That is, in the present invention, it is an object to be solved to provide a method for producing amorphous silica fine particles with low production cost and high sphericity.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have intensively studied and, as a result, invented the following method for producing amorphous silica fine particles.
[0009]
That is, the method for producing amorphous silica fine particles of the present invention includes a raw material supply step of supplying silicon powder and silica powder together with a carrier gas into a reaction chamber, and heating the supplied silicon powder by burning the supplied silicon powder in the reaction chamber. the generated, the combustion heating step of dissolving or vaporization produced silica and by heating the silica powder, Ri Do and a cooling step of forming the amorphous silica particles cooling the dissolved or vaporized silica,
The silica powder has a weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder of 50% by weight or less,
The weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder, and the average volume diameter are combinations of values at which the generated silica and the silica powder are melted or vaporized in the combustion heating step. and wherein the der Rukoto.
[0010]
That is, when silica is heated and melted, it becomes a true sphere due to its surface tension, and is cooled as it is, thereby forming amorphous silica fine particles having a high sphericity. The silica is vaporized once to become amorphous silica fine particles with high sphericity when cooled and aggregated.
[0011]
In addition, since the heat generated when the metal silicon raw material is oxidized to melt or vaporize the silica, the silica can be heated for a long time, and the particle diameter of the produced amorphous silica fine particles is increased. It is also possible. Then, by adjusting the amount of silicon, the amount of heat generated can be increased to vaporize the silica to form fine particles.
[0012]
Therefore, the particle diameter of the finally produced amorphous silica fine particles can be changed by controlling the particle diameter of the silica initially introduced and the ratio of silicon and silica.
[0013]
Therefore, according to the method for producing amorphous silica fine particles of the present invention, amorphous silica fine particles having a required particle size distribution and high sphericity can be produced without using an unnecessarily large amount of expensive silicon. can do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the method for producing amorphous silica fine particles of the present invention will be described in detail. In addition, this invention is not limited by embodiment shown below.
[0015]
The method for producing amorphous silica fine particles of the present embodiment includes a raw material supply process, a combustion heating process, and a cooling process.
[0016]
The method for producing amorphous silica fine particles according to this embodiment is performed using, for example, a production apparatus having a raw material supply unit, a reaction chamber, and an amorphous silica fine particle collecting unit. The raw material supply unit is a means for storing the raw material and supplying the raw material into the reaction chamber, the reaction chamber is a means for burning the raw material inside, and the amorphous silica fine particle collection unit is the produced amorphous silica fine particle It is means to collect.
[0017]
The raw material supply step is a step of supplying silicon powder and silica powder together with a carrier gas into the reaction chamber.
[0018]
Silicon powder and silica powder may be mixed in advance and stored in the same place, or may be stored separately and mixed before being supplied to the reaction chamber or after being supplied. . When storing in the same place, one type of carrier gas may be used, but when storing separately, two types of carrier gases may be used.
[0019]
As the silicon powder, silicon powder having a purity corresponding to the purity required for the produced amorphous silica fine particles is used. Specifically, the allowable content of elements other than silicon element and oxygen element is defined according to the purity required for the amorphous silica fine particles. When producing high-purity amorphous silica fine particles, the purity of the silicon powder is specified so that the required purity can be ensured.
[0020]
The particle size of the silicon powder is not particularly limited, but is preferably a particle size that can be easily mixed with silica particles. Further, the particle diameter should be small to some extent for the purpose of facilitating combustion. However, if the particle size is too small, the fluidity is deteriorated and it is difficult to supply the reaction chamber. Specifically, it is more preferably about 5 to 30 μm. The shape of the silicon powder particles is not particularly limited and is not limited.
[0021]
The silica powder may be in any crystalline form such as crystalline or amorphous. Further, the amorphous silica fine particles produced by the method for producing amorphous silica fine particles of the present invention can be used again as a raw material. And also about silica powder, the silica powder of the purity according to the purity calculated | required by the amorphous silica fine particle manufactured is used. Specifically, similarly to the silicon powder, the allowable amount of elements other than the silicon element and the oxygen element contained in the silica powder is determined according to the purity required for the produced amorphous silica fine particles.
[0022]
The shape of the silica powder particles is not particularly limited, as is the case with the silicon powder, and is not limited. The particle size of the silica powder is not determined solely by the particle size of the silica powder, but is also influenced by the mixing ratio of the silicon powder and the silica powder to be mixed.
[0023]
That is, the particle diameter of the silica powder is such that the silica powder and the silica produced in the combustion heating process described later melt or vaporize according to the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder. It must be a diameter. Conversely, when the particle size of the silica powder is determined, the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is such that the silica powder and the silica produced in the combustion heating process described later are melted or melted. It is necessary for the weight ratio to evaporate. This is because, unless silica is melted or vaporized, amorphous silica fine particles having a high sphericity cannot be produced.
[0024]
The combination of the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder and the average volume diameter results in an average volume diameter of the amorphous silica fine particles finally formed of 20 μm or less. Thus, it is preferable to determine a combination of values. This is because amorphous silica fine particles having an average volume diameter of 20 μm or less are more useful.
[0025]
Further, it is preferable that the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder and the average volume diameter are a combination of values generated by vaporization of silica and silica powder generated in the combustion heating process described later. This is because it is possible to produce amorphous silica fine particles having a small particle diameter as compared with silica powder supplied by vaporizing silica without using a large amount of expensive silicon. Further, for the same reason, the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder and the average volume diameter are such that the average volume diameter of the finally formed amorphous silica fine particles is 2 μm or less. It is more preferable that the value is a combination.
[0026]
And the average volume diameter of a silica powder has preferable 20 micrometers or less, and it is more preferable that it is 10 micrometers or less. In this case, the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is preferably less than 50%, and more preferably less than 30%.
[0027]
And the combination of the particle diameter of the more preferable silica powder and the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is, when the average volume diameter of the amorphous silica fine particles to be produced is 2 μm or less, A combination of an average volume diameter of silica powder of 10 μm, a weight ratio of silica powder to the combined weight of silica powder and silicon powder of less than 30%, an average volume diameter of silica powder of 5 μm, silica powder of silica powder And a weight ratio with respect to the total weight of the silicon powder is a combination of less than 50%. Among these, a combination of the silica powder having an average volume diameter of 5 μm and a weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder of less than 50% is more preferable. This is because the amount of expensive silicon powder used is smaller, so that the cost can be reduced.
[0028]
When the average volume diameter of the amorphous silica fine particles to be produced is 2 μm or more, the average volume diameter of the silica powder is 10 μm, and the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is 30%. The combination of 70% or less and the average volume diameter of the silica powder is 5 μm, and the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is 50% or more and 80% or less. Among these, a combination of an average volume diameter of the silica powder of 5 μm and a weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder of 50% to 80% is more preferable. This is because, for the same reason as described above, since the amount of expensive silicon powder used is smaller, the cost can be reduced.
[0029]
In addition, the combination of the particle diameter of the other preferable silica powder and the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is an average of the amorphous silica fine particles produced by the average volume particle diameter of the silica powder. The weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is a value that is a value that does not vaporize the silica and silica powder produced in the combustion heating process described later. . When silica is vaporized, the amorphous silica fine particles to be formed have substantially the same particle size regardless of the particle size of the raw silica powder. Thereby, the particle diameter of the amorphous silica fine particles to be produced can be controlled.
[0030]
It is necessary to supply a sufficient amount of oxygen into the reaction chamber to oxidize the silicon powder. Otherwise, unoxidized silicon remains. As a method of supplying oxygen into the reaction chamber, there are a method of independently supplying oxygen directly into the reaction chamber, a method of mixing with the carrier gas, and a method of using both of the above methods together. Simple and preferable.
[0031]
The carrier gas is a gas used for the purpose of fluidizing and supplying silicon powder and silica powder into the reaction chamber. As described above, it is preferable that the carrier gas contains oxygen in an amount sufficient to oxidize all silicon powder supplied as a raw material as a whole.
[0032]
As the carrier gas, any gas having low reactivity with respect to silicon powder and silica powder in addition to oxygen can be mixed with the carrier gas. For example, it is possible to mix nitrogen etc. with carrier gas. Therefore, the carrier gas can be used only with oxygen gas, or an inexpensive gas such as air can be used as it is or with further oxygen added.
[0033]
The total amount of the carrier gas is at least necessary to fluidize the supplied silicon powder, silica powder, or a mixture of silicon powder and silica powder and supply it into the reaction chamber, but it is too If the amount of gas supplied is large, the heat generated by the combustion of the silicon powder is cut off, making it difficult to supply it to the silica powder. At the same time, the combustion of the silicon powder cannot be sustained in the reaction chamber, so an appropriate amount is necessary. There is.
[0034]
In the combustion heating process, silicon powder is ignited by an ignition source in the reaction chamber, the silicon powder is combusted, and the generated heat heats silica and silica powder generated by the combustion of the silicon powder. This is a step of melting or vaporizing generated silica and silica powder.
[0035]
The ignition source is not particularly limited as long as it is a means capable of igniting silicon powder. Examples of the ignition source that can be used in the combustion heating process include those caused by discharge, LPG in the reaction chamber, and the like. Examples include those that form the chemical flame used, plasma discharges, and arcs.
[0036]
The inner wall of the reaction chamber in which the combustion heating process proceeds is coated with a substance that does not affect the amorphous silica fine particles formed even when it comes into contact with silica or other fused or vaporized silica, or other inert substances. It is preferable to prevent impurities from being mixed into the produced amorphous silica fine particles.
[0037]
The cooling step is a step of cooling the fused or vaporized silica to form amorphous silica fine particles. The cooling step can also be performed in the same reaction chamber as the combustion heating step. The fused or vaporized silica is cooled and solidified when it is cooled and melted as it moves away from the place where the silicon was ignited, and when it is vaporized, it agglomerates as it cools. Solidify.
[0038]
Therefore, when the silica is melted, the particle diameter of the formed amorphous silica fine particles is often larger than the raw silica powder. When silica is vaporized, as described above, since silica is once vaporized, the particle diameter of the amorphous silica fine particles formed is almost constant regardless of the particle diameter of the raw silica powder. It becomes size.
[0039]
The amorphous silica fine particles thus formed are collected by a collector or the like after being classified by a classifier or the like as necessary.
[0040]
【Example】
<Method for producing amorphous silica fine particles>
FIG. 1 shows a manufacturing apparatus according to the manufacturing method of the present invention. This manufacturing apparatus includes a reaction chamber having an inner wall surrounded by a heat-resistant brick 10a, a reaction vessel 10 having a discharge passage 11a on the side wall, and a burner 9 forming a flame 8 on the upper wall of the reaction vessel 10. It is mainly composed.
[0041]
The burner 9 is connected to a powder supply device 1 for supplying silicon powder and silica powder, and a conduit 4 in which an oxygen supply pipe 40 and an LPG supply pipe 5 for supplying LPG for seed fire are arranged. .
[0042]
A powder collecting device 11 is provided in the discharge passage 11 a, and exhaust gas is sucked into the powder collecting device 11 by a blower 12.
[0043]
The following reaction was performed with the reactor configured as described above to obtain an oxide.
[0044]
First, the valves 50 of the oxygen supply pipe 40 and the LPG supply pipe 5 were opened, the burner 9 was ignited, the inside of the reaction vessel 10 was sufficiently dried, and deoxygenation was performed. Flow rate 8 m ³ / time of the carrier gas, was fed to the reaction chamber at a flow rate of LPG0.4m ³ / time. Next, silicon powder and silica powder were supplied from the powder supply device 1 and burned. The powder supply apparatus 1 was mixed with the particle diameters of Examples 1 and 2 shown below and the mixing ratio of the respective crystalline silica powder and silicon powder, and the mixture was put into the powder supply apparatus.
[0045]
The blower 12 was operated to suck the combustion exhaust gas containing silica powder, and the silica powder was collected by the collection attachment 11.
[0046]
When the particle size distribution is wide in the above manufacturing apparatus, a two-stage collection device as shown in FIG. 2 is provided and a filter for collecting only oxides having a desired particle size or more is provided in the first stage. Small particles that have passed through are collected in the second stage, and if necessary, a hopper provided separately with large or small amorphous silica particles collected in the first or second stage. When transported and re-supplied into the reaction vessel, amorphous silica fine particles having a uniform particle size were obtained.
[0047]
Therefore, it is possible to obtain amorphous silica fine particles having a uniform particle diameter without increasing the number of steps and changing the apparatus. In addition, since the manufacturing apparatus shown in FIG. 2 is configured to reuse the amorphous silica fine particles having a small particle diameter, when it is necessary to reuse the amorphous silica fine particles having a large particle diameter, It is necessary to provide a tube for transporting the amorphous silica fine particles to the powder supply device before the first-stage filter.
[0048]
(Particle size and mixing ratio of silicon powder and silica powder)
(Example 1)
The silicon powder having a volume average diameter of 20 μm and the crystalline silica having a volume average diameter of 5 μm are 5, 10, 30, 40, and 50% by weight based on the total amount of the crystalline silica combined with the silicon powder and the crystalline silica powder. Each was mixed.
[0049]
(Example 2)
Silicon having a volume average diameter of 20 μm and crystalline silica having a volume average diameter of 10 μm are set to 5, 10, 30, 40 wt% with respect to the total amount of the crystalline silica combined with the silicon powder and the crystalline silica powder. Each was mixed.
[0050]
(result)
Example 1
When the amount of crystalline silica mixed was 40% by weight or less, the particle size distribution of the produced amorphous silica fine particles was about 0.1 to 2 μm, and the volume average diameter was about 1 μm. When the amount of crystalline silica mixed was 50% by weight, the volume average diameter of the produced amorphous silica fine particles was about 8 μm. The produced amorphous silica fine particles all have a sphericity (in this specification, the aspect ratio of the amorphous silica fine particles by an electron microscope is referred to as sphericity) of 0.98 to 1.02. Value.
[0051]
Example 2
When the amount of the crystalline silica mixed is 10% by weight or less, the particle size distribution of the produced amorphous silica fine particles was about 0.1 to 2 μm, and the volume average diameter was about 1 μm. . When the amount of the crystalline silica mixed was 30, 40% by weight, the particle size distribution of the produced amorphous silica fine particles was about 10 to 20 μm, and the volume average diameter was 12 μm. The produced amorphous silica fine particles all had a sphericity of 0.98 to 1.02.
[0052]
【The invention's effect】
That is, the present invention has an effect of providing a method for producing amorphous silica fine particles with low production cost and high sphericity.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a manufacturing apparatus according to an embodiment.
FIG. 2 is a schematic cross-sectional view of a production apparatus which is a modification of the embodiment and reuses amorphous silica fine particles having a small (large) particle size.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1 '... Powder supply apparatus 4 ... Conduit 5 ... LPG supply pipe 40 ... Oxygen supply pipe 8 ... Flame 9 ... Burner 10 ... Reaction container 11, 11' ... Powder collection container 12 ... Blower

Claims (7)

A raw material supply step of supplying silicon powder and silica powder together with a carrier gas into the reaction chamber;
A combustion heating step of burning the supplied silicon powder in the reaction chamber to generate heat, heating the generated silica and the silica powder to dissolve or vaporize, and
Ri Do and a cooling step of forming the amorphous silica particles cooling the dissolved or vaporized silica,
The silica powder has a weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder of 50% by weight or less,
The weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder, and the average volume diameter are combinations of values at which the generated silica and the silica powder are melted or vaporized in the combustion heating step. method for producing amorphous silica particles, characterized in der Rukoto.   In the silica powder, the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder and the average volume diameter are such that the average volume diameter of the formed amorphous silica fine particles is 20 μm or less. The method for producing amorphous silica fine particles according to claim 1, which is a combination of values. The silica powder is a weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder, and an average volume diameter is a value at which the average volume diameter of the formed amorphous silica fine particles is 2 μm or less. the method for producing an amorphous silica particle according to claim 1 or 2 which is a combination of. 4. The silica fine particles according to claim 3 , wherein the silica powder has an average volume diameter of 10 μm or less, and the silica powder is less than 50% by weight based on a total weight of the silica powder and the silicon powder. Manufacturing method.   The silica powder has an average volume diameter that is half the average volume diameter of the amorphous silica fine particles to be produced, and the weight ratio of the silica powder to the combined weight of the silica powder and the silicon powder is The method for producing silica fine particles according to claim 2, wherein in the combustion heating step, the generated silica and the silica powder have a value that does not vaporize. The method for producing silica fine particles according to claim 1, wherein the carrier gas has a higher oxygen concentration than air. The method for producing silica fine particles according to claim 1, wherein the carrier gas is oxygen.

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