KR960010902B1 - Process for the preparation of high purity amorphous spherical silica powder - Google Patents

Abstract

The process includes the steps of smashing silica powders with mill including polyurethane, nylons or elastic organics, silica rock ball or melted crystal ball at 10-40 r. p. m. during 0.5-5 hours and spray drying it so as to form spherical silica powders; and heat-treating these powders at 500-1300 deg.C during one minute or two hours in rotary kiln.

Description

Method for producing dense high purity amorphous spherical silica powder.

1 is a scanning electron micrograph (magnification: 10,000 times) before and after heat treatment of the spherical silica powder prepared according to the present invention,

2 is a scanning electron micrograph (magnification: 1,000 times) of spherical silica powder prepared by the present invention and the conventional method.

The present invention relates to a method for producing dense high purity amorphous spherical silica powder. More specifically, before the spray-drying of the silica powder of granules produced as a result of neutralization of alkali silicate with acid, a high-purity spherical silica powder is prepared through a pulverization process and heat-treated to obtain a dense high-purity amorphous spherical silica powder. It relates to a manufacturing method.

High purity silica powder is used as a high purity silica glass raw material used for various fillers such as resin and rubber for integrated circuit encapsulation materials, substrates, electronic materials, and jig for semiconductor manufacturing, and its range of use is increasing due to its excellent thermal and electrical properties. . In addition, the spherical silica powder improves fluidity and moldability, and is advantageous in terms of wear of the mold during molding, and its application field is being expanded for high quality.

As a method for producing high purity silica powder, there is a method for refining high quality silica and natural crystals. However, this method is increasingly difficult to obtain a high-purity raw material, which is becoming a reality. As another method, Japanese Patent Laid-Open No. 62-21703 discloses a gas phase decomposition method of silicon tetrachloride, but the raw materials used in this method are expensive, and there are problems such as corrosiveness and flammability, making it difficult to handle. As another method, Japanese Patent Application Laid-Open Nos. 60-90811 and 63-35411 disclose a wet method using alkali silicate and silicon alkoxide, but in fact, acid neutralization reaction using alkali silicate (Japanese Patent Publication No. 1-21093) Compared with the use of silicon alkoxides, it is easier in terms of economics and handling, and therefore the technique of Japanese Patent Laid-Open No. 63-35411 is rarely used.

In addition, Japanese Patent Application Laid-Open No. 1-21093 discloses a method for producing silica powder of high purity using alkali silicate as a raw material. In this method, Na ₂ O is removed by neutralization with acid and ion exchange resin. Practical methods to manufacture by using are introduced. In particular, the silica powder prepared in the above method is capable of purifying SiO ₂ from 99.99% to 99.999% according to the reaction conditions (acid concentration during reaction, SiO ₂ / Na ₂ O molar ratio, reaction temperature, reaction time), and powder size. It can manufacture to several nm-several mm. However, the powder of several nm size is difficult to the next process (filtration separation, washing), and more than 2mm aggregates have a problem in purity because the components such as alkali (Na ₂ O) or thorium (Th) is not completely removed.

On the other hand, conventionally, the preparation of spherical silica powder is Japanese Patent Laid-Open No. 60-191016, which manufactures a fine silica powder and then uses a spray dryer to produce spherical silica powder. Difficult to obtain with high purity because it is difficult to wash, etc. On the contrary, when spray drying the silica of the granules as it is to obtain a high purity, a large particle size (50 μm or more) powder is mixed, there is a problem that it is difficult to obtain the desired particle size and spherical shape.

Conventionally, the spherical silica powder has a problem in purity because the particles are porous and the binder remains according to the purpose, and the effect of the spherical filler is halved because it cannot maintain the spherical shape by the pressure when molding into a mold. (Chargeability) also had a bad flaw.

In order to solve this problem, Japanese Patent Laid-Open No. 2-59416 and Japanese Patent Laid-Open No. 60-131868 introduce a method of thermal spraying using a gas flame, respectively, but the former method has a problem that the use particle size is limited to 50 μm. In the latter method, the flaw becomes elliptical by flame melting in the spherical state, the particle size is not maintained due to the increase of the particle size, or cracks occur in spherical silica powder. The disadvantage is that the purity is poor as impurities mixed in.

In addition, Japanese Patent Application Laid-Open No. 62-96313 introduces a method for thermal spraying after prefiring, but during the thermal spraying after prefiring, the flame temperature must be maintained at 1850 ° C or higher, which makes the manufacturing process complicated and increases the manufacturing cost. In addition, there are disadvantages of the thermal spray powder as described above.

Accordingly, an object of the present invention is to solve such a problem in the prior art, and when the high-purity spherical silica powder is prepared, a disintegration step is added, and a heat treatment step is performed to improve the compactness. It is to provide a method for producing a silica powder.

Hereinafter, the present invention will be described in detail.

The present invention provides a spherical silica powder obtained by neutralizing a silicic acid alkali and an acid with a spray-dried powder to form a spherical silica powder, wherein the silica powder is an organic matter-containing mill, After wet or dry pulverization with a quartz ball or a molten quartz ball, it is spray dried to prepare a spherical silica powder, which is then subjected to heat treatment at 500 to 1300 ° C. for 1 minute to 2 hours to prepare a high-purity amorphous spherical silica powder. It features.

Hereinafter, the present invention will be described in more detail.

In the present invention, as described in Japanese Patent Application Laid-Open No. 1-21092, a neutralized reaction of an alkali silicate and an acid is used to prepare a silica powder of high purity. In the present invention, in consideration of the workability and purity, the particle size of the silica powder is prepared to be 1μm to 2mm.

In the present invention, the high purity silica powder obtained above is first wet or dry pulverized and then granulated using a spray dryer to prepare a high purity spherical silica powder having a desired particle size.

At this time, the disintegration process may be a wet or dry disintegration process as described above, but in order to continuously perform the spray drying process, it is more preferable to use wet disintegration, and as a result, powder of 1 μm or less is produced. In particular, the disintegration process according to the present invention performs the disintegration using an organic material, for example, a polyurethane or rubber or nylon embedded rod or a 20 to 30 mm quartz ball or molten quartz ball.

The rotation speed of the ball mill is preferably 10 to 40 times per minute, but preferably 15 to 30 times per minute. If the number of revolutions of the ball mill is less than 10 times per minute, the disintegration process becomes difficult. On the contrary, if the ball mill exceeds 40 times, the wear of the interior materials and the balls is not good.

In addition, the disintegration time is appropriately performed for 30 minutes to 5 hours, more preferably for 1 hour to 2 hours.

The two sheets of the disintegrated car powder are manufactured as spherical silica powders having a desired particle size through a spray dryer, for example, 1 to several hundred μm, wherein the equipment conditions of the spray dryer (disk rotation speed) , Spherical silica powder of desired size can be obtained by adjusting injection speed, amount of binder, raw material input speed, inlet / outlet temperature, etc.

In the present invention, the spherical silica powder obtained as described above is subjected to a heat treatment step to prevent the speed from being lowered by the organic substances mixed during the disintegration and to improve the compactness (filling property). That is, the heat treatment process according to the present invention may be carried out in a box furnace, so that aggregation may occur between particles. Therefore, the heat treatment process may be performed in a fluidized bed calcination furnace or a rotary kiln. More preferably, the heat treatment is performed in a fluidized bed calcination furnace with low pollution.

Heat treatment according to the present invention is preferably carried out for 1 minute to 2 hours at a temperature of 500 to 1300 ℃, preferably at 800 to 1100 ℃ for 5 minutes to 1 hour. Here, if the heat treatment time or temperature is above the above range or Na ₂ O is present in the spherical silica powder, cristobalite crystal phase is formed, so it is preferable to perform heat treatment under the above conditions.

When the spherical silica powder is heat-treated as described above, while the silica powder is maintained in an amorphous phase, organic matter, remaining binders, chlorine components, etc. mixed during the disintegration are volatilized to obtain a finer spherical silica powder.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

3N hydrochloric acid was added over a period with stirring and then heated to 2500ml to 70 ℃ alkali silicate No. 2 (Na ₂ O 14% by weight, SlO ₂ 34 _{wt%, SiO 2 / Na 2 O} = 2.4) 1400kg per hour. At this time, the reaction temperature was maintained at 70 ℃ or more. After the addition was completed, the reaction was stirred by 90 ° C./3 hours. The granular silica powder prepared by solid-liquid separation of this reaction was washed, filtered and dried to obtain granular silica powder.

Impurity content of the prepared granular silica powder is shown in Table 1 below.

The granulated silica prepared above was wet crushed by putting 900 g of the sample with respect to 3400 g of water in a polyurethane built-in ball mill. At this time, the disintegration condition was performed 20 times per minute and time for 1 hour. After disintegration, the silica powder sheets were spheroidized using a spray dryer. Spray drying conditions were 15,000 times the rotation speed of the disk per minute, the inlet and outlet temperature was 250 ℃ and 100 ℃, and added as a binder vinyl vinyl polymer (PVA) 0.1% by weight.

Subsequently, the spherical silica powder was heat-treated at 1100 ° C. for 15 minutes using a fluidized packed calcination furnace.

The densified silica powder thus obtained was an amorphous phase as a result of X-ray diffraction analysis (XRD). The impurity content of the prepared spherical silica powder is shown in Table 1 below, and scanning electron micrographs are as shown in FIGS. 1 and 2.

1 (a) is a photograph (magnification: 10,000 times) of the spherical salica powder before heat treatment, and FIG. 1 (b) is a photograph (magnification: 10,000 times) after heat treatment.

(A) is a photograph (magnification: 1,000 times) of the spherical silica powder spray-dried.

After heating 2500 ml of 3N hydrochloric acid solution to 70 degreeC, 1400 kg of alkali silicate No. 2 (14 weight% of NaO, 34 weight% of S10, and SiO / NaO = 2.4) was added over 1 hour, stirring. At this time, the reaction temperature was maintained at 70 ℃ or more. After the addition was completed, the reaction was stirred by 90 ° C./3 hours. The granular silicide powder prepared by solid-liquid separation of this reaction was washed, filtered and roughened to obtain granular silica powder.

The granulated silica powder obtained above was spray-dried, but the spray-drying conditions were 15,000 times per minute of the disk rotation speed, the inlet and outlet temperatures were 250 ° C and 100 ° C, and the binder was added by adding 0.1% by weight of vinyl alcohol polymer (PVA). Silica powder was obtained.

The spherical silica powder thus prepared was sprayed using a flame spraying machine to obtain a final spherical silica powder.

Scanning electron micrographs of the silica powder (learning: 1,000 times) are the same as those of the second drawing (b).

Claims (1)

In the method for producing a spherical silica powder by spray drying a silica powder prepared by neutralizing an alkali silicate with an acid, and from the same, a high-purity amorphous spherical silica powder is prepared. The spherical silica powder was prepared by spray drying after wet or dry disintegration with a built-in mill, silica ball or fused quartz ball at 10 to 40 revolutions per minute and a disintegration time of 30 minutes to 5 hours. Method for producing a dense high purity amorphous spherical silica powder, characterized in that the heat treatment in a fluidized bed calcination furnace or rotary furnace for 1 minute to 2 hours at 500 to 1300 ℃.