JP3350139B2 - Method for producing spherical silica particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing spherical silica particles from a siliceous raw material, and more particularly to a method for producing spherical silica particles having a particle size of 0.03 mm to 2.0 mm.
It relates to a method for producing spherical silica particles in the range of mm.

[0002]

2. Description of the Related Art Spherical silica particles have been used as a raw material for grinding media of a stirring and mixing mill, ball lenses made of quartz glass, and sintered filters. 0.03 mm to 2.
Those having a range of 0 mm are preferred. However, conventionally obtained spherical silica particles generally have a particle size of 0.03 mm or less, and a spherical particle of 0.03 mm to 2.0 mm, which is particularly suitable for the above-mentioned applications, as described in detail below. Obtaining silica particles is extremely difficult.

Conventionally, spherical silica particles have been produced by the following flame fusion method, combustion method, sol-gel method, quartz glass cutting and polishing method, and the like. The flame fusion method is a method in which crystalline or amorphous silica is used as a raw material and is melted in oxygen and hydrogen or in an LPG flame, and the generated spherical silica particles are collected from a furnace bottom or an exhaust gas. The particle size of the spherical silica particles that can be produced by this method is usually 0.03 mm or less, and the maximum flame temperature is as low as about 3000 ° C.
It is difficult to produce spherical silica particles of 0.03 mm or more. The combustion method is a method in which silicon tetrachloride or silicon powder is used as a raw material and burned in oxygen and hydrogen or an LPG flame. The particle size of the spherical silica particles that can be produced by this method is
It is said that the size of the raw material is from 0.01 μm to 1.0 μm because the raw material burns to fume, and it is difficult to produce spherical silica particles of 1.0 μm or more. The sol-gel method is a method in which a raw material silicate alkoxide is introduced little by little into a mixture of alcohol and pure water, and is hydrolyzed. At this time, by keeping the solution alkaline or dispersing it with a surfactant, the polycondensed silica can be formed into spherical silica particles without gelling or secondary association. The particle size of the spherical silica particles that can be produced by this method is
If the polycondensation is too large, formation becomes impossible and it is broken, so that it is usually 0.03 mm or less, and it is considered difficult to produce spherical silica particles having a particle size of 0.03 mm or more.

On the other hand, the cutting and polishing method of quartz glass is a method in which quartz is heated and quenched to crush it, and the powder is flame-melted or electro-melted to be vitrified, and then cut and polished to form a spherical shape. In principle, it is possible to produce spherical silica particles of any size. However, in this method, since the quartz raw material is vitrified and then cut from the glass one by one, and the cut one is polished to produce spherical silica particles, the productivity is extremely poor, and therefore the production cost is extremely low. There is a problem that it is expensive.

[0005]

As described above, in the conventional spherical silica particle production technology, the particle size is reduced from 0.03 mm to 2.
It is extremely difficult to produce spherical silica particles of 0 mm, and even if it can be produced, there is a problem that the productivity is extremely poor and the cost becomes extremely high. Therefore, the present invention overcomes the above-mentioned problems of the conventional spherical silica production technology and has a particle size of 0.03 mm to 2.
An object of the present invention is to provide a novel method for producing spherical silica particles that can easily and efficiently produce 0 mm spherical silica particles at low cost.

[0006]

Means for Solving the Problems As a result of intensive studies on a method for producing spherical silica particles, the present inventor has found that a siliceous raw material is melted by a high-frequency thermal plasma, which is a completely different method from conventional methods, to obtain a particle diameter of 0.1%. The inventors have found that spherical silica particles in the range of 03 mm to 2.0 mm can be produced, and have reached the present invention. That is, the present invention provides a method for producing spherical silica particles having a particle diameter of 0.03 mm to 2.0 mm by passing a siliceous raw material through a high-frequency thermal plasma to melt the particles. This problem has been solved by a manufacturing method. The siliceous raw material used in the present invention may be either crystalline or amorphous. As the crystalline siliceous raw material, natural quartz powder, synthetic quartz powder, quartzite powder, quartz sand powder and the like can be used. As the amorphous siliceous raw material, an aqueous solution of an alkali metal silicate or amorphous silica obtained from silicon tetrachloride or silicate alkoxide can be used. Further, crystalline quartz powder, silica powder, silica sand powder, or the like may be melted and vitrified, and then pulverized.

The particle size of the siliceous raw material is adjusted by pulverizing and classifying as necessary. When pulverizing the siliceous raw material, a conventional pulverizer such as a rolling mill or a vibrating ball mill such as a pot mill, a tube mill, a uniball ball mill or a compartment mill, or a stirring and mixing mill such as a tower mill or a stirring tank mill is used. Alternatively, a roll mill or the like can be used, and preferably, a rolling ball mill, a vibration ball mill, or a vibration ball mill is used. In order to prevent the siliceous raw material from being contaminated by the pulverizing / classifying operation, the material of the crushing medium such as a ball, a rod, or the like, which is used in contact with the siliceous raw material or as necessary, is quartz glass,
What is necessary is just to select each suitably from siliceous materials, such as fused quartz, quartz, agate, or silica stone. The method for producing spherical silica particles according to the present invention is a method essentially free of impurities. If a high-purity siliceous raw material is used, the resulting spherical silica particles will also have high purity.

On the other hand, as the high-frequency thermal plasma used in the present invention, a high-temperature ionized gas obtained by high-frequency induction heating of a plasma forming gas, that is, high-frequency induction thermal plasma can be adopted. The high-frequency induction thermal plasma consists of a single plasma frame formed by using one induction heating coil, or two induction heating coils.
Any of two-stage plasma frames formed by individually winding and generating high-frequency induction thermal plasma in two stages using two high-frequency power sources is possible.

[0009]

[Function] High frequency thermal plasma is approximately 10,000K ~ 3,
000K high temperature thermal plasma frame is generated.
The siliceous raw material is classified and adjusted to a predetermined range of particle size, and is supplied from the powder injector into the plasma frame to spread the thermal plasma while expanding at a certain angle (adjustable by back pressure). Fall in the frame. The siliceous raw material falls while melting at the ridge while passing through the thermal plasma frame, and falls while being cooled after leaving the temperature range of the plasma frame, so that the shape becomes spherical. The particle size of the spherical silica particles corresponds to the particle size of the classified siliceous raw material, and can be adjusted by adjusting the passage time of the plasma flame (that is, the back pressure, the length of the plasma flame). Large spherical silica particles having a particle size of 10 μm or more, especially 0.03 mm to 2.0 mm, which were difficult to obtain, can be easily obtained. Furthermore, in the case of the two-stage plasma, the raw material powder for which the minimum passage time was not obtained is reheated by the second-stage thick plasma, and the melting time is obtained, resulting in a spherical silica particle having a large particle size that was impossible in the past. .

[0010]

The present invention will be specifically described below with reference to examples and application examples. Note that the present invention is not limited to the following examples and application examples. First, a specific example of an apparatus for producing spherical silica particles for carrying out the method for producing spherical silica particles according to the present invention and a method for producing spherical silica by the apparatus will be described with reference to the drawings. As shown in FIG. 1, the spherical silica production apparatus includes a feeder 1 for supplying a raw material, a plasma torch 2, a heat retaining tower 3, a cooling chamber 4, and a spherical silica particle collector 5. The raw material supply feeder 1 vibrates a vibrating ball in which the raw material is stored, sends out the raw material, supplies the raw material to the powder injector 7 via the supply pipe 6 with the carrier gas, and uses the plasma torch from the powder injector. It is supplied into the generated high-frequency thermal plasma frame 10. At that time, by adjusting the gas pressure of the carrier gas, it is possible to adjust the supply speed of the siliceous raw material and the spread angle from the powder injector 7 into the thermal plasma frame.

As shown in detail in FIG. 2, the plasma torch 2 has a tubular body 8 having an open end on the heat retaining tower 3.
A predetermined gas G1 is injected into the tube from the other end side, and power is supplied from a high-frequency power supply (not shown) to an induction coil 9 wound around the outer periphery of the tube 8 close to the heat-retaining tower 3 to generate high-frequency energy. Generated by the high-frequency energy,
The plasma generating gas in the tube is a high temperature ionized gas, that is, a thermal plasma. At this time, the sheath gas G2 is supplied along the inner tube wall of the tube to protect and cool the plasma torch from the high temperature of the plasma. The heat retaining tower 3 is provided to fulfill a function of securing a temperature gradient of the generated thermal plasma and a falling distance of the raw material.
The fused spherical silica particles are cooled to near room temperature in the cooling chamber 4 and collected by the collecting device 5.

FIG. 3 shows another embodiment of the manufacturing apparatus in which the plasma torch is changed. In this embodiment, the tube 20 is formed so that the lower portion is formed larger in diameter than the upper portion, and the first guide is provided on the outer periphery of the small diameter portion. The second induction coil 22 is separately wound around the large diameter portion of the coil 21 below, and each is connected to a different high-frequency power supply so that it can be controlled separately. As a result, as shown conceptually in the figure, a two-stage plasma in which a thin plasma frame and a thick plasma frame are continuous can be obtained. In addition,
Normally, a thermal tower need not be used. Therefore, according to this device, the crushed powder of the siliceous raw material supplied from the powder injector 7 passes through the thin plasma frame 25 formed by the first induction coil, and further enters the thick plasma frame 26 formed by the second induction coil 22. Reheated. As a result, as shown in the figure, even if the raw material powder could not obtain the minimum passage time required for spherical formation only with the primary plasma flame, the ridge was gradually melted by reheating with the thick plasma flame. To form a spherical shape.

Example 1 1) Preparation of Siliceous Raw Material JIS No. 3 water glass was heated and concentrated to have a viscosity at 20 ° C. of 300 cps. Approximately 8 liters of this water glass is pressurized with a pump, and 300 liters of an 8 wt% sulfuric acid aqueous solution maintained at 50 ° C. is passed through a filter (aperture: 0.07 mm) and a nozzle (a hole diameter: 0.5 mm, number of holes: 50) through a nozzle. It was extruded into the coagulating bath at a speed of 1 m per second. The silica particles obtained in a fibrous state are immersed in a 10-fold amount of a freshly prepared 8 wt% aqueous sulfuric acid solution and stirred at a temperature of about 95 ° C. for about 1 hour,
The impurities were extracted and then washed twice using 10 times the amount of pure water of the silica particles. After repeating the above extraction and washing operations 5 times, the wet silica particles obtained by dehydration with a centrifugal separator were dried at a temperature of 150 ° C. for 8 hours by a hot air drier,
3.7 kg of amorphous dry silica particles were obtained. The dried amorphous silica particles were fired at 1250 ° C. for 2 hours in an atmospheric pressure atmosphere to obtain 3.3 kg of amorphous fired silica particles. The amorphous calcined silica particles were pulverized using a quartz ball mill and classified to obtain amorphous calcined component-grade silica particles having a particle size range of 0.03 mm to 1.0 mm, which was used as a siliceous raw material.

2) High-Frequency Thermal Plasma Treatment The amorphous baked component-grade silica particles were melted by high-frequency induction thermal plasma under the following conditions in the manufacturing apparatus shown in FIG. Plasma gas conditions; Core gas: Ar 15 L / min O ₂ 5 L / min Sheath gas: Ar 30 L / min, O ₂ 10 L / min Oscillation conditions; Anode voltage: 10.4 kv Anode current: 3.0 A Frequency: 4 0 MHz Raw material supply amount: 1.0 kg / hr As a result, spherical silica particles having a particle size of 0.03 mm to 1.0 mm were obtained.

Example 2 1) Preparation of Siliceous Raw Material Quartz glass (manufactured by Toshiba Ceramics Co., Ltd.) was coarsely ground with a jaw crusher to obtain a coarsely ground powder of silica glass. This coarsely pulverized powder is washed with hydrochloric acid, and the coarsely pulverized silica glass powder from which contaminants have been removed is pulverized using a quartz ball mill and classified to obtain amorphous classified silica particles having a particle size range of 0.03 mm to 1.0 mm. ,
This was used as a siliceous raw material. 2) High-frequency thermal plasma treatment The above-mentioned amorphous classified silica particles were subjected to melting treatment by high-frequency induction thermal plasma under the following conditions in the manufacturing apparatus shown in FIG. Plasma gas conditions; Core gas: Ar 15 L / min, O ₂ 5 L / min Sheath gas: Ar 30 L / min, O ₂ 10 L / min Oscillation conditions: Anode voltage 10.3 kv Anode current 3.1 A Frequency 4.0 MHz Raw material Supply amount: 1.0 kg / hr As a result, spherical silica particles having a particle size of 0.03 mm to 1.0 mm were obtained.

Example 3 1) Preparation of Siliceous Raw Material Natural quartz (manufactured by Unimin Co., Ltd.) is pulverized using a quartz ball mill and classified to classify crystalline classified silica particles having a particle size range of 0.03 mm to 1.0 mm. This was used as a siliceous raw material. 2) High-Frequency Thermal Plasma Treatment The crystalline classified silica particles were melted by the production apparatus shown in FIG. 1 using high-frequency induction thermal plasma under the following conditions. Plasma gas conditions; Core gas: Ar 15 L / min, O ₂ 5 L / min Sheath gas: Ar 30 L / min, O ₂ 10 L / min Oscillation conditions: Anode voltage 10.3 kv Anode current 3.1 A Frequency 4.0 MHz Raw material Supply amount: 1.0 kg / hr As a result, spherical silica particles having a particle size of 0.03 mm to 1.0 mm were obtained.

Example 4 1) Preparation of Siliceous Raw Material The treatment was performed in the same manner as in Example 5 except that the particle size range of the crystalline classified silica particles was changed from 1.0 mm to 2.0 mm. 2) High-frequency thermal plasma treatment (two-stage plasma) The crystalline classified silica particles were melted by a high-frequency induction thermal two-stage plasma under the following conditions using the manufacturing apparatus shown in FIG. Plasma gas conditions; Core gas: Ar 20 L / min, O ₂ 7 L / min Sheath gas: Ar 40 L / min, O ₂ 14 L / min Oscillation conditions; (1st stage) Anode voltage: 10.3 kv Anode current: 3 A frequency: 4.0 MHz (second stage) Anode voltage: 10.0 kv Anode current: 1.3 A Frequency: 13.56 MHz Raw material supply amount: 2.0 kg / hr As a result, the particle size is 1.0 mm to 2.0 mm. Was obtained.

Application Example 657.2 g of the spherical silica particles obtained in Example 1 were charged into a stirring and mixing mill as grinding media. Average particle size 12.8
A silica slurry (slurry concentration: 30%) of 1430 g of silica having a particle size of 1,340 g and pure water (3,340 g) was introduced into a stirring and mixing mill by a pump and circulated for 18 minutes. At this time, the stirring disk of the stirring and mixing mill had a diameter of 64 mm, a thickness of 3 mm, and four disks, and a peripheral speed of the disk was 10 m / S. When the silica slurry was recovered and the average particle size of the silica was measured, it was 0.9 μm, and submicron pulverization was performed efficiently. The weight of the spherical silica particles used as the grinding media was measured to be 645.9 g, and the wear amount was 11.3 g.
Met. The abrasion loss of the crushed media with respect to the crushed silica was 11.3 / 1430 = 0.79%, which was a good value.

[0019]

According to the present invention, it has been physically difficult to produce spherical silica particles having a particle size of 0.03 mm (30 μm) or more by the conventional method. By adjusting the heat energy given to the silica particles, spherical silica particles having a large particle diameter can be economically produced as a pulverizing medium for a stirring and mixing mill, a ball lens made of quartz glass, and a raw material for a crystal filter, which is suitable. In addition, by using the two-step plasma, the raw material powder, for which the minimum passage time was not obtained, was reheated by the second-stage thick plasma, and the melting time was obtained. Can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for producing spherical silica particles for carrying out the method for producing spherical silica particles of the present invention.

FIG. 2 is an enlarged view of the plasma torch part.

FIG. 3 is a schematic diagram of spheroidization by a two-stage plasma torch which is another embodiment of the plasma torch of another spherical silica particle producing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Feeder for supply of raw material 2 Plasma torch 3 Insulation tower 4 Cooling chamber 5 Recovery flask 7 Powder injector 8, 20 Tubular body 9 High frequency induction coil 21 First induction coil 22 Second induction coil

Continuation of the front page (72) Inventor Yoshiaki Inoue 2- 16-21 Higashi-Gotanda, Shinagawa-ku, Tokyo Inside of High-frequency Refining Co., Ltd. (72) Inventor Kazuhiro Kawasaki 2- 16-21 Higashi-Gotanda, Shinagawa-ku, Tokyo (72) Inventor Seiji Yokota 2-16-21, Higashi-Gotanda, Shinagawa-ku, Tokyo Inside (56) References JP-A-1-96008 (JP, A) JP-A Sho JP-A-2-203932 (JP, A) JP-A-64-65043 (JP, A) JP-A-61-197416 (JP, A) JP-A-63-221842 (JP, A) A) JP-A-57-191238 (JP, A) JP-A-60-175537 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/18 C03C 8/00 C03B 20 / 00

Claims (5)

(57) [Claims] 1. A method in which a siliceous raw material is passed through a high-frequency thermal plasma and melted to obtain a particle size of 0.03 mm to 2.
A method for producing spherical silica particles, wherein spherical silica particles having a diameter of 0 mm are produced. 2. The method for producing spherical silica particles according to claim 1, wherein the siliceous raw material is a crystalline silicic acid raw material. 3. The method for producing spherical silica particles according to claim 1, wherein the siliceous raw material is an amorphous silicic acid raw material. 4. The method for producing spherical silica particles according to claim 1, wherein the high-frequency thermal plasma for melting the siliceous raw material is a high-frequency induction thermal plasma. 5. The method for producing spherical silica particles according to claim 4, wherein the high-frequency induction thermal plasma is a two-stage plasma.