KR100427260B1 - A preparation method of micron-size silica - Google Patents

Abstract

The present invention relates to a method for producing micron-size silica, and more particularly, to wet grinding silica particles synthesized by a wet method by applying an impact force and a friction force to a grinding medium such as balls, rods, or pebbles from the outside in the presence of an aqueous medium. By introducing the present invention, the particle size distribution and the shape of the silica are controlled simultaneously to a method for producing a silica consisting of a fine and uniform particle size.

Description

A preparation method of micron-size silica

The present invention relates to a method for producing micron-size silica, and more particularly, to wet grinding silica particles synthesized by a wet method by applying an impact force and a friction force to a grinding medium such as balls, rods, or pebbles from the outside in the presence of an aqueous medium. By introducing the present invention, the particle size distribution and the shape of the silica are controlled simultaneously to a method for producing a silica consisting of a fine and uniform particle size.

Plastic films, sheets, and the like coated with various resins often have a tendency for their surfaces to stick together when wound or stacked in the final process. In this case, the opening properties of various plastic films and the adhesion of the surface itself can be improved by blending inorganic fillers such as silica in various resins. In addition, high speed performance is required in the printing process, and freshly printed films, sheets, and papers are often transferred to wet ink superimposed surfaces. Inorganic fillers are very effective in preventing such blocking or printed ink from transferring to other surfaces.

Silica-based fillers are known to be the most suitable as such inorganic fillers, and thus silica-based fillers are commonly used as antiblocking fillers such as most plastic films and sheets and paper.

In general, there are two types of silica fillers, a crystalline type and an amorphous type. Crystalline silica is produced by grinding and purifying high purity natural white quartzite or quartz, and has excellent thermal conductivity. Amorphous type silica includes fused silica produced by melting crystalline silica at high temperature and synthetic silica of dry or wet type, and this type is often used industrially because of its excellent thermal expansion characteristics and chemical stability.

In general, fine powder silica particles are used as antiblocking fillers for plastic films, paper, etc., which are pulverized amorphous silica or synthetic silica produced by a thermal spraying method or a spray drying method in a conventional crushing process. It has an angle as shown in 2. However, when the silica particles are not rounded and have an angle, the viscosity increases when the resin is mixed with the resin to form a plastic film or sheet, and wear of the molding apparatus is large, which lowers workability, and incorporates impurities due to device wear. Etc., and thus adversely affects the performance of the filler, so that the amount of the filler can not be increased.

Accordingly, in order to solve the above problems, the production of spherical fine powder silica has been attempted for amorphous fused silica. For example, Japanese Patent Application Laid-Open No. 61-118131 discloses a method for producing spherical amorphous fine powder silica particles by blowing crystalline silica together with a gas stream from a nozzle to control the dispersion, melting, and cooling of particles under suitable conditions. However, this method is expensive and it is difficult to obtain a predetermined particle size distribution because the particles fuse with each other in the melting process, and since the spherical shape has a drawback that the strength of the resin composition is lowered. . Japanese Patent Application Laid-Open No. 63-8208 discloses a method of contacting an aqueous alkali metal silicate solution with an ammonia-type cation exchange resin to produce an ammonium silicate sol, and then spray drying it to recover fine powder silica gel. The product obtained by the above method is spherical, and the lower limit of the average particle size is relatively fine, such as 3 µm. However, the gelling time is difficult to control, so that coarse particles (secondary particles) or silica having large pores are easily formed. Silicas with different particles or large voids are not suitable as plastic and paper fillers because they do not have sufficient mechanical strength and cause breakage or reduced packing density.

As another method for producing spherical fine powder silica, a method of controlling the size and shape of the particles by a mechanical method is also known. For example, Japanese Patent Application Laid-open No. Hei 4-92809 is a spherical silica (average particle size ≒ 36㎛) containing coarse fused particles produced by the thermal spraying method to cut the fusion between the silica particles by using a jet mill A method of obtaining a desired silica particle is disclosed. However, the above method employs a jet mill, which is an expensive special device, which not only has a problem in practicality but also focuses on the disintegration of the fused particles to obtain micron-sized fine silica with controlled particle size distribution and shape. There is no problem. Therefore, no mechanical preparation of amorphous type micron size silica has been proposed to date.

In order to solve the above problems, the present invention provides silica particles in the presence of an aqueous medium while applying impact and frictional forces to a silica particle synthesized by a wet method from a outside, such as a ball, rod, or pebble. The present invention was completed by wet grinding to prepare silica.

Accordingly, an object of the present invention is to provide an economical method for producing micron size silica using a general mill such as a ball mill or a vibration mill as well as controlling the particle size distribution and shape of the silica.

1 is a process diagram schematically showing a method for producing micron size silica according to the present invention.

Figure 2 shows an electron micrograph of the coarse pulverized silica as a comparative example of the present invention.

Figure 3 shows an electron micrograph of the silica prepared by Example 1 of the present invention.

Figure 4 shows an electron micrograph of the silica prepared by Example 4 of the present invention.

The present invention is characterized by a method for producing micron-sized silica in which silica particles are wet-divided with a grinding media selected from balls, rods and pebbles in the presence of an aqueous medium.

The present invention will be described in detail as follows.

The silica particle which is a raw material of this invention uses the crushed silica of the average particle diameter 300-340 micrometers which grind | pulverized the silica gel (water content of 60-80 weight%) synthesize | combined by the wet method by the roller mill.

The method for producing a micron size silica of the present invention will be described in more detail with reference to FIG. 1 as follows.

First, the silica particles which are the raw materials of the present invention are obtained through the processes shown in FIGS. 1 and 2, and are obtained by coarsely pulverizing silica gel synthesized by the wet method of 1 using a mill such as a roller mill of 2. In this case, in order to prevent contamination, the liner of the grinder is preferably made of zirconium oxide or high purity alumina.

Next, a fine grinding process of silica according to the present invention shows a process of fine grinding using a mill such as a ball mill or a vibration mill in the presence of an aqueous medium (FIG. 3). As the grinder, a vessel-driven grinder such as a ball mill or a vibration mill may be used, and these grinders generally include a cylindrical container and a grinding medium (ball, rod or pebble). The ball is charged into the container and the container is rotated or vibrated to cause crushing of silica between the ball and the ball or between the container inner wall and the ball. At this time, the grinding time is 0.5 to 3 hours, the rotational speed of the ball mill is 60 rpm, the frequency of the vibration mill is preferably 1000 vpm. In the case of using such a container-driven pulverizer, the parts contacting the silica powder such as a rotating container and a ball are made of ceramics or lined with polyurethane resin to prevent contamination due to wear and tear. As the ball, an alumina ball having a diameter of 5 to 15 mm can be used.

The amount of the silica particles: aqueous medium: pulverized medium used in the micronization step is preferably contained in a volume ratio of 20 to 40:20 to 40:40 to 80. If the amount of silica particles charged in the micronization process is too small, there is a problem that the impact / friction between the grinding media or the grinding media and the inner wall of the container increases, resulting in contamination, and if too large, cushioning of the silica particles may occur. Due to this there is a problem of lowering the grinding performance. In addition, if the amount of the aqueous medium charged in the micronization process is too small, the action force of the grinding medium does not sufficiently reach the silica, that is, the silica becomes entangled with the ball and the inner wall of the container due to the increase of the adhesive force, and thus, There is a problem that the impact force is weak and the grinding effect is low, if too much silica is in a slurry state, there is a problem that the micronization operation does not proceed well. In addition, if the amount of the pulverizing medium charged in the micronization process is too small, there is a problem that the action of the pulverizing medium does not sufficiently reach the silica, so that the pulverizing effect is lowered.

The maximum particle diameter of the silica particles through this micronization process is less than 100 µm, and the average particle diameter is 0.8 to 12.8 µm.

In addition, the silica particles through the micronization process obtain a final micron size silica (5 in FIG. 1) through a drying process (4 in FIG. 1).

On the other hand, when the fine particles are subjected to the micronization process using a ball mill or a vibration mill, the fine particles of silica are charged into a ball mill or a vibration mill without using an aqueous medium to perform the micronization process. Easily separated from the problem of lowering the grinding efficiency. Therefore, by adding an appropriate amount of an aqueous medium to smoothly transfer the frictional force of the grinding media to the silica, it is possible to obtain a micron size silica with high efficiency.

In addition, as the aqueous medium, silica particles may interact with each other, and a liquid that is easy to transfer pressure from the outside to the silica may be used. Preferably, liquid materials such as water, alcohols, mineral oil, and the like may be used. In consideration of the ease of handling during operation and the ease of separation after operation, water alone or a mixture of water and alcohols such as ethyl alcohol and methyl alcohol can be most advantageously used industrially.

As such, the method for producing micron-size silica according to the present invention can control the particle size distribution and shape of the silica. In addition, it is industrially advantageous because ordinary ball mills, vibration mills, and the like can be used as it is, or only a part of modification, such as a portion in contact with silica particles or a lining with a polyurethane resin.

In addition, the manufacturing method of the micron size silica which concerns on this invention can be performed also in any case of a batch operation or a continuous operation.

As such, the present invention can control the particle size distribution and shape of the silica prepared as a method for producing the micron size silica can be usefully used in antiblocking fillers such as plastic film and paper.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to Examples.

Example 1.

Into a ball mill (type A-5, manufactured by Nippon Kagaku Togyo Co., Ltd.), crushed silica having an average particle size of 320 µm, which was preliminarily crushed by a roller mill, was loaded with alumina balls having a diameter of 10 mm and water at the same time. The crushed silica: alumina: water was added in a volume ratio of 35:55:35. Silica particles were prepared by treating the grinder at 60 rpm for 2 hours. The prepared silica particles were measured using a centrifugal sedimentation particle size distribution analyzer (manufactured by Shimadzu, model SA-CP3). As a result, the average particle diameter of the silica particles was about 2.9 μm.

Electron micrographs were observed to determine the particle shape of the prepared silica particles (FIG. 3), and coarsely pulverized fused silica was used as a comparative example (FIG. 2). As a result of electron micrograph, it was confirmed that the particle shape of the prepared silica was considerably spherical compared to the fused silica.

Example 2.

Silica particles were prepared in the same manner as in Example 1, except that alumina balls having a diameter of 5 mm were used and the grinding treatment time was 3 hours, and the prepared silica had a spherical shape with an average particle diameter of about 0.8 μm. It was confirmed to have.

Example 3.

Silica particles were prepared in the same manner as in Example 1 except that the grinding treatment time was 1 hour, and the prepared silica had a spherical shape with an average particle diameter of about 6.2 μm.

Example 4.

A crushed silica having an average particle size of 320 µm, which was preliminarily crushed by a roller mill in a vibrating mill (MB-1 type, manufactured by Chuo Kakohki Co., Ltd.) was charged, and alumina balls having a diameter of 10 mm and water were added at the same time. The crushed silica: alumina balls: water was added in a volume ratio of 30:60:30. Silica particles were prepared by treating the grinder with an amplitude of 8.5 mm and a frequency of 1,000 vpm for 1 hour. The prepared silica particles were measured using a centrifugal sedimentation particle size distribution analyzer (manufactured by Shimadzu, model SA-CP3). As a result, the average particle diameter of the silica particles was about 1.6 μm.

In order to examine the particle shape of the prepared silica particles, electron micrographs were observed (FIG. 4), and coarsely pulverized fused silica was used as a comparative example (FIG. 2). As a result of electron micrograph, it was confirmed that the particle shape of the prepared silica was considerably spherical compared to the fused silica.

Example 5.

Silica particles were prepared in the same manner as in Example 4 except that the grinding process time was 0.5 hours, and the prepared silica had a spherical shape with an average particle diameter of about 2.1 μm.

As described above, the silica particles according to the method of the present invention are micron-sized, have a spherical shape, and are composed of uniform particle diameters. Thus, antiblocking fillers such as plastic films, sheets, and paper, additives of various polymers, cosmetics, ink, etc. It can be usefully used as a raw material for hydrophobic applications such as paint and paint.

Claims (7)

delete delete delete delete In the method of producing a silica powder by wet pulverization using a drive mill including a ball mill or vibration mill, a) crushed silica particles having a water content of 60 to 80% by weight and an average particle diameter of 300 to 340 µm, b) alumina balls having a ball size of 5 to 10 mm ø, and c) water or a mixed solution of water and alcohol. Wet grinding, but containing a), b) and c) in a volume ratio of 20 to 40: 20 to 40: 40 to 80, and pulverizing for 0.5 to 3 hours to obtain spherical silica powder having an average particle diameter of 0.8 to 12.8 μm. Method for producing micron size silica. The method of claim 5, wherein the ball mill has a rotation speed of 60 rpm and a vibration mill having a frequency of 1000 vpm. delete