JP3191325B2 - Particle size control method for silica powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle size control method for sharpening the particle size distribution of silica powder.

[0002]

2. Description of the Related Art Conventionally, various powders have been used in a wide range of fields such as medicines, agricultural chemicals, foods, and ceramics. The particle size of the powder used in these fields greatly affects the physical properties of the final product. For example, when (1) the inorganic powder is used as a reinforcing filler such as rubber, if the particle size is too large, a sufficient reinforcing effect cannot be obtained. Conversely, if the particle size is too small, the bulkiness is increased and workability is poor. Or adverse effects such as too high plasticity of the product rubber,
(2) In the field of agrochemicals, if the particle size distribution of the carrier powder is uniform and particles of 10 μm or less are removed, the dispersibility, scattering properties, and stability over time are significantly improved. 3) The toner of the copying machine is composed of a thermoplastic resin, a colorant, or the like, and is adjusted to a particle size range of about 5 to 25 μm so that the charge amount of these powders becomes uniform during copying. It is known.

[0003] For the various powders handled in various industries as described above, what is almost commonly required is that the average particle size is relatively small (several μm to several tens μm) and the particle size is uniform. That is.

As a method of responding to such a demand, conventionally,
A method of pulverizing a material serving as a raw material to a desired particle size and then filtering or classifying the material is employed.

[0005]

However, when the material as a raw material is pulverized in this way, a large amount of particles considerably smaller than a desired particle size are generated in the pulverization process, but a large amount of micron-order powder is generated. It is difficult. Also,
Even with a commonly used air classifier, cutoff of 1 μm or less is difficult, and therefore, when the target powder is classified fine powder, mixing of submicron particles into the product cannot be avoided.

[0006] The coarse powder separated in the classification step is returned to the pulverization step and re-pulverized. However, since the powder that has become finer than necessary cannot be reused, the yield of the product deteriorates. For example, a toner used in a copying machine is prepared by melting and kneading a thermoplastic resin or a colorant with a roll mill, pulverizing with a jet mill or the like, and then using an air classifier to obtain a predetermined product particle size (5%).
２５25 μm). In this case, it is common practice to return unnecessarily pulverized products in the pulverizing step to the melting step, but the production efficiency of the product naturally declines.

[0007] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a method for controlling the particle size of an inorganic powder, which can easily and surely sharpen the particle size distribution by growing fine particles of silica powder.

[0008]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies to achieve the above object, silica powder having an average particle size of 0.1 to 50 μm was converted to 600 to 900 ° C.
By heat treatment to a temperature in the range, fine particles of silica powder grow, thereby shifting the entire particle size distribution,
The sharpness of the particle size distribution makes it possible to easily and surely grow the unnecessarily fine particles in the silica powder containing a large amount of fine particles considerably finer than the desired particle size after the pulverization to the target particle size. The present inventors have found that silica powder having a desired particle size and having a uniform particle size can be easily and economically obtained, and the present invention has been accomplished.

Hereinafter, the present invention will be further described. In the method for controlling the particle size of silica powder according to the present invention, the average particle size containing fine particles smaller than a desired particle size after pulverization is 0.1 to 50 μm.
m is heated to 600 to 900 ° C. to grow fine particles of the silica powder, thereby narrowing the particle size distribution of the silica powder.

[0010]

The average particle size of the silica powder is 0.1 to 50 μm. If the average particle size is larger than 50 μm, a sufficient heat treatment effect may not be obtained, and a considerably high temperature may be required to obtain a target particle size.

Therefore, when the first raw material is not powder but bulk, or when the average particle size is larger than 50 μm, it is necessary to use a conventional pulverizer (such as a hammer mill or a jet mill) for pulverization. preferable.

When the powder is heat-treated, it can be carried out by using a usual heating device, dryer, baking device and the like. In this case, the heat treatment temperature is 600 to 900C. On the other hand, the heat treatment time is not particularly limited. The heat treatment time varies depending on the heating method. For example, in the case of indirect heating, it is usually 0.5 to 2 hours, and in the case of direct heating, almost instantaneous heating is sufficient. May be set so as to approach the target particle size distribution in accordance with the type of. However, heat treatment for too long a time is not only wasteful, but also sintering progresses more than necessary, and there is a possibility that large particles larger than the intended purpose may be formed or solidified.
Further, the heat treatment atmosphere is not particularly limited, and may be generally in the air. However, when an oxidation reaction or the like becomes a problem, the heat treatment is performed in an inert gas such as helium or nitrogen or a reducing gas such as hydrogen gas. It can be performed.

The particle size control method of the present invention grows fine particles in the silica powder by such heat treatment and sharpens the particle size distribution, and the silica powder thus obtained is effective for various uses. Used for

[0015]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Reference Examples, but the present invention is not limited to the following Examples.

Reference Example 1 A metal oxide (Fe ₂ O ₃ , Cu) manufactured by Wako Pure Chemical Industries, Ltd.
O, NiO) powder was passed through a 350-mesh sieve, and the powder under the sieve was heat-treated in an electric furnace at a temperature shown in Table 1 for 1 hour, and the particle size distribution before and after the heat treatment was compared. The results are shown in Table 1 and FIGS.

Here, FIG. 1 is a distribution diagram on the integrated screen of Fe ₂ O ₃ untreated and after heat treatment, FIGS. 2 to 5 are distribution diagrams of the same frequency, respectively, and FIG. 6 is an integrated screen of CuO untreated and after heat treatment. The upper distribution diagram, FIGS. 7 to 9 are the same frequency distribution diagram, and FIG.
Is a distribution map on the integrated screen of untreated NiO and after heat treatment,
11 to 12 are the same frequency distribution diagrams.

The particle size distribution was measured using a Coulter Counter TA-II type viscometer (manufactured by Nikkaki Co., Ltd.).
The measurement was performed using a 00 μm aperture tube.

[0019]

[Table 1]

Example 1 White carbon (SiO ₂ , Carplex FPS-1) manufactured by Shionogi & Co., Ltd. was heat-treated in an electric furnace at a temperature shown in Table 2 for 1 hour, and the particle size distribution before and after the heat treatment was compared. did. The results are shown in Table 2 and FIGS.

FIG. 13 is a distribution diagram on the integrated screen after untreatment and after heat treatment, and FIGS. 14 to 16 are distribution diagrams of the same frequency.

[0022]

[Table 2]

Reference Example 2 Various metal powders (Ni, Cr, S) manufactured by Wako Pure Chemical Industries, Ltd.
(n, Zn) was used as it is for Zn, and the other metal powder was passed through a 350 mesh sieve and heat-treated at a temperature shown in Table 3 for 1 hour in a He gas flow using an electric furnace. The particle size distribution before and after was compared.
The results are shown in Table 3 and FIGS.

FIG. 17 is a distribution diagram of Ni on an integrated screen after untreated and heat-treated, FIGS. 18 to 19 are distribution diagrams of the same frequency, respectively, and FIG. 20 is a distribution diagram of Cr on an integrated screen after untreated and heat-treated. , FIGS. 21 to 22 are the same frequency distribution diagrams,
23 is a distribution diagram of Sn on untreated and heat-treated integrated screens, FIGS. 24-26 are distribution diagrams of the same frequency, FIG. 27 is a distribution diagram of Zn on untreated and treated heat-treated integrated screens, and FIGS. It is the same frequency distribution figure.

[0025]

[Table 3]

[0026]

According to the present invention, it is possible to obtain a silica powder having a sharp particle size distribution, and thus it is possible to recover unnecessary superfluous fine particles and use them effectively. By controlling the heat treatment conditions, a silica powder having a particle size distribution suitable for the purpose can be obtained.

[Brief description of the drawings]

FIG. 1 is a distribution diagram of Fe ₂ O ₃ on an integrated screen after untreatment and after heat treatment.

FIG. 2 is a frequency distribution diagram of untreated Fe ₂ O ₃ and after heat treatment (700 ° C.).

FIG. 3 is a frequency distribution diagram of untreated Fe ₂ O ₃ and after heat treatment (800 ° C.).

FIG. 4 is a frequency distribution diagram of untreated Fe ₂ O ₃ and after heat treatment (900 ° C.).

FIG. 5 is a frequency distribution diagram of untreated Fe ₂ O ₃ and after heat treatment (1000 ° C.).

FIG. 6 is a graph showing the distribution of CuO on an integrated screen after untreatment and after heat treatment.

FIG. 7 is a frequency distribution diagram of untreated CuO and after heat treatment (700 ° C.).

FIG. 8 is a frequency distribution diagram of untreated CuO and after heat treatment (900 ° C.).

FIG. 9 is a frequency distribution diagram of untreated CuO and after heat treatment (1000 ° C.).

FIG. 10 is a distribution chart on an integrated screen of untreated NiO and after heat treatment.

FIG. 11 is a frequency distribution diagram of untreated NiO and after heat treatment (500 ° C.).

FIG. 12 is a frequency distribution diagram of untreated NiO and after heat treatment (700 ° C.).

13 is a on cumulative sieve distribution chart after untreated and heat treatment of SiO _2.

FIG. 14 is a frequency distribution diagram of untreated SiO ₂ and after heat treatment (600 ° C.).

FIG. 15 is a frequency distribution diagram of untreated SiO ₂ and after heat treatment (800 ° C.).

FIG. 16 is a frequency distribution diagram of untreated SiO ₂ and after heat treatment (900 ° C.).

FIG. 17 is a distribution chart on an integrated screen of untreated Ni and after heat treatment.

FIG. 18 is a frequency distribution diagram of untreated Ni and after heat treatment (400 ° C.).

FIG. 19 is a frequency distribution diagram of untreated Ni and after heat treatment (600 ° C.).

FIG. 20 is a distribution diagram of Cr on an integrated screen after untreatment and after heat treatment.

FIG. 21 is a frequency distribution diagram of Cr untreated and after heat treatment (600 ° C.).

FIG. 22 is a frequency distribution diagram of Cr untreated and after heat treatment (800 ° C.).

FIG. 23 is a distribution chart of integrated Sn on an integrated screen after untreatment and after heat treatment.

FIG. 24 is a frequency distribution chart of untreated Sn and after heat treatment (100 ° C.).

FIG. 25 is a frequency distribution diagram of untreated Sn and after heat treatment (150 ° C.).

FIG. 26 is a frequency distribution diagram of untreated Sn and after heat treatment (200 ° C.).

FIG. 27 is a distribution diagram of integrated Zn on untreated and after heat treatment.

FIG. 28 is a frequency distribution diagram of untreated Zn and after heat treatment (200 ° C.).

FIG. 29 is a frequency distribution diagram of untreated Zn and after heat treatment (400 ° C.).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 2/00 B22F 1/00 C01B 33/18

Claims (1)

(57) [Claims] 1. Silica powder having an average particle size of 0.1 to 50 μm containing fine particles smaller than a desired particle size after pulverization is 60
A method for controlling the particle size of silica powder, comprising heat-treating the powder in the range of 0 to 900 ° C. to grow fine particles of the silica powder and narrowing the particle size distribution of the silica powder.