JPH07196310A - Amorphous silica granule and its production - Google Patents

Abstract

PURPOSE:To obtain a spherical amorphous silica granules having a high apparent specific gravity in spite of being porous, smooth surface of the particles and no cracks. CONSTITUTION:An aqueous solution of an alkali silicate is reacted with an aqueous solution of an acid and heat-treated to give a silica hydrogel, which is ground in a wet state in 15-25wt.% slurry concentration at <50 deg.C under high shear to prepare a slurry of a silica hydrogel having <=4mum particle diameter. The slurry of the silica hydrogel is spray-dried or a miture of the slurry of the silica hydrogel and a slurry of amorphous silica by precipitation method is spray-dried to produce amorphous silica particles. The prepared silica particles are spherical particles having smooth surface and 20-100mum particle diameter, 0.2-0.5cc/g apparent specific gravity, 18-43,500 pore radius, 0.5-3.5cc/g pore volume and 100-600m<2>/g BET specific surface area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous silica granular material and a method for producing the same. More specifically, it is porous and has a large apparent specific gravity, and the particle surface is smooth and has no cracks. TECHNICAL FIELD The present invention relates to spherical amorphous silica particles and a method for producing the same.

[0002]

2. Description of the Related Art Amorphous silica particles such as so-called fine spherical silica gel are used for various polymerization catalysts, carriers for other catalysts, compounding agents for resins and cosmetics, other compositions, carriers for various chemicals, spacers, It is used in various applications such as chromatography. Conventionally, as a method for producing fine spherical silica gel, a method in which an aqueous solution of alkali silicate and an aqueous solution of mineral acid are reacted, the resulting silica hydrogel is optionally hydrothermally treated, and then the silica hydrogel slurry is spray-dried is generally used. There is.

In Japanese Patent Laid-Open No. 62-275014, an aqueous solution of an alkali metal silicate is reacted with an aqueous solution of a mineral acid to give a SiO ₂ concentration of 6.5 to 11.
5% by weight of active silicic acid is produced, the silicic acid is gelled under stirring, reacted with an aqueous ammonia solution, filtered, and the resulting hydrogel is wet-milled and spray-dried by a two-fluid nozzle method. Thereby producing silica gel for liquid chromatography.

Further, in JP-A-2-221112, a silica hydrogel obtained by reacting an alkali metal silicate with a mineral acid is subjected to a wet pulverization treatment, and then a slurry of the silica hydrogel and water is spray-dried. It is described that the amount of water present in the slurry is adjusted to 0.2 to 1.5 times the weight of the silica hydrogel when the spherical silica gel is produced. Further, in the above-mentioned publication, it is desirable that the physical properties of the spherical silica gel have a surface area of 50 to 700 m ² / g, an average pore diameter of 20 to 1000Å, a pore volume of 0.3 to 2.0 ml / g, and an average particle diameter of 5 μm to 5 mm. It has also been shown that it is very difficult to produce spherical silica gel that can satisfy all of these physical properties.

[0005]

However, while the amorphous silica granules according to the known method are porous, they have a large bulk (small apparent specific gravity) and are packed per unit weight in the final catalyst. There is an inconvenience that the volume becomes large, and this inconvenience is also disadvantageous in the use as a compounding agent for polymers and the like, and also in the point of distribution of the granular material.

Further, the amorphous silica granules according to the known method generally have low mechanical strength, and when they are subjected to ultrasonic irradiation or vibration, they tend to collapse toward the smaller particle size side. There is. According to the research conducted by the present inventors, the known fine-grained amorphous silica granules have a kind of pumice-like appearance with fine irregularities or pores on the surface, or a surface without such irregularities is relatively large. Most of the smooth ones had a relatively large number of cracks on the surface, and no such defects were not recognized.

Therefore, an object of the present invention is to provide a true spherical amorphous silica granular material having a relatively large apparent specific gravity, a smooth particle surface and no cracks, while having a porous interior, and a method for producing the same. To provide. Another object of the present invention is to provide particles having high particle strength, low abrasion tendency, compact packing volume, and excellent supportability for catalysts and other chemicals, and compoundability and fluidity with polymers and the like. SUMMARY OF THE INVENTION It is an object of the present invention to provide amorphous silica granules having a constant size and a method for producing the same. Still another object of the present invention is to provide a method capable of producing the amorphous silica particles having the above characteristics with high productivity.

[0008]

According to the present invention SUMMARY OF], by reacting an aqueous alkali silicate solution and an acid aqueous solution, the silica hydrogel obtained by a heat treatment at a slurry concentration of SiO ₂ concentration of 15 to 25 wt%, Amorphous, characterized in that it comprises wet-milling at a temperature not exceeding 50 ° C. and under high-speed shearing to prepare a slurry of silica hydrogel having a particle size of 4 μm or less, and spray-drying the slurry of silica hydrogel. A method of making a fine silica granule is provided.

[0009] According to the present invention, by reacting an aqueous alkali silicate solution and an acid aqueous solution, the silica hydrogel obtained by a heat treatment, at a slurry concentration of SiO ₂ concentration of 15 to 25 wt%, beyond 50 ° C. Wet milling at a constant temperature and under high-speed shearing to prepare a silica hydrogel slurry having a particle size of 4 μm or less. The silica hydrogel slurry (A) is prepared by a precipitation method to form an amorphous silica slurry (B).
When the mixed slurry is spray-dried with
A method for producing amorphous silica particles is provided, characterized in that the weight ratio of silica based on O ₂ is in the range of A: B = 9: 1 to 1: 9.

According to the present invention, furthermore, the particles are made of spherical particles having a smooth surface without cracks under an electron microscope, and have a volume-based median diameter of 20 to 100 μm as measured by the Coulter counter method. The apparent specific gravity according to 6.8 is in the range of 0.2 to 0.5 g / cc, and the pore volume by the mercury intrusion method is 18 to 43.
0.5 to 3.5 cc in the range of 500 Å
/ G range and BET specific surface area of 100 to 6
Provided is an amorphous silica granule characterized by being in the range of 00 m ² / g.

[0011]

In the present invention, the silica hydrogel slurry is treated with Si.
A remarkable feature is that the O ₂ concentration is 15 to 25% by weight and the wet pulverization is performed at a temperature not exceeding 50 ° C. and under high-speed shearing so that the particle diameter becomes 4 μm or less. Generally, wet pulverization of silica hydrogel into fine particles is technically very difficult because silica hydrogel is a kind of viscoelastic material. In the present invention, the silica hydrogel slurry is used as SiO ₂ which has never been considered before.
The above fine pulverization is made possible by high-concentration of 25 to 25% by weight, particularly 18 to 22% by weight, and wet pulverization at a temperature not exceeding 50 ° C. under high-speed shearing.

In the process of studying the relationship between the SiO ₂ concentration and the viscosity of silica hydrogel slurry, the present inventors
It was found that there is a region where the viscosity increases as the concentration of SiO ₂ increases, but the viscosity decreases rather than a certain concentration. Further, in this silica hydrogel slurry, the influence of temperature and the influence of shearing force are significant, and if the temperature exceeds a certain temperature or the shearing force becomes small, it becomes difficult to grind, but in the present invention, the SiO ₂ concentration is By wet pulverizing at a high concentration and at a temperature not exceeding 50 ° C. and under high shear, wet pulverization to the above particle size is possible, and amorphous silica particles having excellent properties described below are obtained. It was successful.

The surface state and the apparent density of the amorphous silica particles by the gel method are closely related to the pore volume having a pore radius of 100 to 1000 angstroms (hereinafter simply referred to as mesopores, which will be described later). To do. According to the method of the present invention, the particle size of the hydrogel is 4 μm or less, especially 2.
By performing wet pulverization so as to have a particle size of 5 μm or less, amorphous silica satisfying the above-mentioned various properties can be obtained. The attached drawing “FIG. 1” shows the hydrogel particle size in the slurry in the gel method and the pore volume (1) of the resulting amorphous silica particles.
It is understood that there is a very close relationship between the two because it is a plot of the relationship with the range of 0 to 1000Å).

In the present invention, a high-concentration finely pulverized slurry of silica hydrogel obtained by the gel method can be used alone for spray-drying granulation, and a so-called sedimentation method amorphous silica slurry is blended with this slurry, and this mixture is mixed. The slurry can also be used for spray drying granulation. In this latter aspect, the mixing ratio of the silica hydrogel slurry (A) of the gel method and the amorphous silica slurry (B) of the precipitation method is SiO 2.
Silica weight ratio of ₂ criteria A: B = 9: 1 to 1: 9, especially 8: 2 to 2: 8 may be mixed in, it is possible to obtain a large granulate, especially particle strength without a crack in the surface.
The amorphous silica granular material of the present invention has a volume-based median diameter (D50) measured by the Coulter counter method of 10 to 150 μm, and particularly 20 to 100 μm.
A remarkable feature is that the surface is smooth and has a spherical shape without cracks as observed with a scanning electron microscope.

A and B in the attached drawing "FIG. 2" are scanning electron micrographs showing the particle structure of the amorphous silica granules obtained by the spray method in which the mesopores of the silica hydrogel obtained by the gel method are 0.8 cc / g. Is 200, B is 100
It is 0. Also, A and B in "FIG. 3" are scanning electron micrographs showing the particle structure of the amorphous silica particles of the gel method with mesopores of 0.7 cc / g, and A and B are the same as above. Magnification.

According to these photographs, when the amorphous silica particles by the gel method have mesopores of the order of 0.8 cc / g, they have a rough structure with fine irregularities and pores on the entire surface. As shown in Sample H-4 in Table 1 of Comparative Example described later, the particle strength is extremely low and the tendency to wear is large. In addition, those having a mesopore of the order of 0.7 cc / g have no rough structure on the surface and have a smooth surface as a whole as compared with those mentioned above, but cracks are generated on the entire particle surface. Has a different structure,
This is Sample H-1 shown in Table 1 of Comparative Example described later, which is not yet satisfactory in terms of particle strength and particle surface abrasion tendency.

On the other hand, A and B in FIG. 4 are scanning electron micrographs showing the particle structure of the gel method amorphous silica granules having mesopores of 0.4 cc / g produced according to the present invention. , A and B have the same magnification as above,
This is Sample 1-5 shown in Table 1 of Example 1 described later. 2, FIG. 3 and FIG. 4 and Table 1 show that the gel amorphous silica particles of the present invention are porous particles because the mesopores are smaller than a certain critical value. Is smooth, has no cracks, and is spherical in shape, and from the appearance shown in FIG. 4, the silica granules of the present invention have particle strength and abrasion resistance. It becomes clear that it has a great advantage in terms of wear tendency. The whisker-like holes observed in FIG. 4 are holes formed by the loss of water during spray drying.

According to the present invention, the gel method of amorphous silica granules having a smooth surface without cracks under an electron microscope has a BET specific surface area of 1 in relation to having a porous structure.
00 to 600 m ² / g and a pore radius of 18 to 43
The pore volume measured by mercury porosimetry in the range of 500 Å is in the range of 0.5 to 3.5 cc / g,
In particular, the most remarkable feature is that the pore volume in the pore radius range of 100 to 1000 angstrom is 0.2 to 0.65 cc / g, preferably 0.3 to 0.5 cc / g.

The attached drawing "FIG. 5" is a graph showing the distribution of the pore volume with the pore radius as the horizontal axis for various types of amorphous silica particles, and the curve A is the amorphous silica of "FIG. 2", The curve B shows the pore volume distribution of the amorphous silica shown in FIG. 3, the curve C shows the amorphous silica shown in FIG. 4, and the curve D shows the pore volume distribution of the amorphous silica shown in FIG. ing. Generally, those having a pore volume distribution smaller than 150 angstroms in the pore volume distribution are called micropores, and those having a larger pore size distribution are called macropores. The range of the pore radius of 100 to 1000 angstroms defined in the present invention is that of micropores and macropores. It was found that there are pores in the intermediate region, that is, mesopores, and the pore volume in the pore radius of this region is closely related to the smoothness and apparent density of the surface of the particles without cracks.

That is, in the amorphous silica granules of the present invention (curve C), only the pore volume in the specific region is larger than that of the conventional gel method amorphous silica granules (curves A and B). It is greatly reduced, and the surprising fact that it contributes selectively and preferentially to the densification of the grain surface and the increase of the apparent specific gravity becomes clear. In the present invention, setting the pore volume (mesopore) in this specific region to 0.65 cc / g or less is essential in terms of densification of the particle surface and increase in apparent specific gravity, but the pore volume is 0. When it is less than 0.2 cc / g (curve D), various activities required for the amorphous silica are lost, which is not preferable. From these things, in the present invention, by using the above-mentioned hydrogel slurry by the gel method, the slurry of amorphous silica by the precipitation method is mixed with this slurry, and both are sprayed in the same manner in a wide range by spray drying. It is understood that a crack-free amorphous silica granular material whose particle surface is densified even when mixed is obtained in the same manner.

According to the present invention, therefore, the particle strength is high, the abrasion tendency is small, the filling volume is compact, and the supportability for catalysts and other products, the compoundability in polymers and the like and the filling ability are excellent. Amorphous silica granules can be obtained, and since silica hydrogel slurry can be subjected to high-concentration wet pulverization and spray granulation, it is possible to reduce the equipment cost and energy cost, and at the same time, to produce amorphous silica with high productivity. The advantage is that silica granules can be produced.

[0022]

Preferred Embodiment of the Invention

(Preparation of Hydrogel Slurry) According to the present invention, an alkali silicate aqueous solution is reacted with an acid aqueous solution to first produce a silica hydrogel by the gel method. Alkali silicate as a raw material is an alkali metal hydroxide on easily reactive silica recovered from sodium silicate or potassium silicate of water glass, which is standardized by JIS as an industrial product, and clayey raw materials such as acid clay. It is possible to use, for example, an alkali silicate obtained by reacting the product solution. SiO in alkaline silicate aqueous solution
_{The 2} concentration should be in the range of 6 to 28% by weight.
The molar ratio of O ₂ : M ₂ O (M is an alkali metal) is
Generally, it should be in the range of 2: 1 to 4: 1, especially 2.5: 1 to 3: 1.

As the mineral acid used in the neutralization reaction, hydrochloric acid, sulfuric acid and the like are generally used, but a mixed acid thereof can also be used. The concentration of the aqueous mineral acid solution is generally 10 to 75% by weight,
It is particularly preferable that the amount is in the range of 20 to 60% by weight. The neutralization reaction by contacting both raw materials includes a method of adding one raw material of both raw materials to the other solution under stirring, and a method of simultaneously contacting both raw material solutions under constant conditions. The neutralization temperature is not particularly limited, but is generally 50 ° C or lower,
The pH at the end of neutralization is suitably in the range of 0-10. This neutralization produces a silica hydrosol, which is generally converted to a silica hydrogel by leaving it for 30 minutes or longer.

The SiO ₂ concentration in the hydrogel to be formed is generally as low as 5 to 30% by weight, but in the present invention, silica is also used to control the water content (increase the SiO ₂ concentration) in addition to controlling the pores of the hydrogel. Heat treatment of the hydrogel of
The silica hydrogel has an O ₂ concentration of 5% or more. The temperature of this heat treatment is suitably 100 to 170 ° C., and it can be carried out, for example, in an autoclave.

After the silica hydrogel after the heat treatment is washed with water, it is generally coarsely pulverized to have a diameter of 20 to 100 μm to obtain the above-mentioned silica hydrosol slurry having a SiO ₂ concentration of 15 to 25% by weight, and then the above-mentioned. Wet milling under high speed shear. For the wet pulverization, a friction inner plate mill known per se, for example, (Dyno Mill manufactured by Willie A. Bakofen) is preferably used, but of course, if high speed shear is possible, another wet pulverizer is used. You can also In this case, it is important that the temperature of the slurry does not exceed 50 ° C., preferably 40 ° C., in order to produce a silica hydrogel slurry having a particle size of 4 μm or less. The particle size thus obtained is 4 μm or less,
The fine silica hydrogel slurry having a particle size of preferably 3 μm or less, more preferably 2.5 μm or less can be directly subjected to spray drying granulation, or can be mixed with a slurry of precipitated amorphous silica obtained by a method known per se. Then, this mixed slurry may be spray-dried and granulated.

(Preparation of Precipitation Amorphous Silica Slurry) Precipitation amorphous silica is prepared by dissolving sodium silicate, hydrochloric acid, and nitric acid in a concentrated alkali metal salt solution, as will be described later.
It is produced by reacting with a mineral acid such as sulfuric acid.
As the alkali metal salt solution, alkali metal salts of inorganic acids or organic acids can be used alone or in combination of two or more kinds. It is preferable to select a combination that produces sodium chloride as an alkali metal salt solution, a raw material for silicic acid, and sodium chloride as an acid component because the cost is low and the metal salt solution can be easily recycled.

Simultaneous injection of sodium silicate and hydrochloric acid into a concentrated saline solution produces silica by a metathesis reaction, but it is necessary to control the pH in this reaction step, and during the simultaneous injection, The pH is maintained in the range of 2 to 7, and particularly preferably in the range of 3.5 to 6, and the aging is performed while the pH is in the range of 2 to 5 after the completion of the simultaneous injection. The concentration at the start of simultaneous injection of saline solution is generally 5 to 30% by weight,
Particularly preferably, it is in the range of 13 to 18% by weight, while the silica concentration at the end of the simultaneous pouring is 1 to 20.
It should be in the range of weight percent. The temperature during the simultaneous pouring reaction is preferably in the range of 50 to 100 ° C., and the simultaneous pouring reaction is preferably completed in 3 to 20 hours.
After the completion of simultaneous pouring, the aging is 30 at a temperature of 50 to 100 ° C.
It is preferable to perform this for about 5 minutes to 25 hours. The silica formed is separated from the mother liquor, then washed with water and filtered to obtain Si
The silica cake has an O ₂ concentration of 5 to 30% by weight.

The amorphous silica obtained by the precipitation method has an average particle size of 0.5 to 3 μm by the Coulter counter method.
And the specific surface area according to the BET method is 120 to 350 m ² /
g, the aromatic adsorption index (AAI) is 4.5 to 15, and the adsorption ratio defined as the ratio of aromatic adsorption index (AAI) / BET specific surface area is 4.0 × 10 ^{-2 to} 7.5. × 1
It should be in the range of 0 ^-2 .

(Preparation of Mixed Slurry) When the mixed slurry is used in the present invention, the gel method silica hydrogel slurry (A) and the precipitation method amorphous silica slurry (B) are mixed in a weight ratio based on SiO ₂ . A: B = 9: 1 to 1: 9 It is particularly preferable to mix them in a weight ratio of 8: 2 to 2: 8. The above-mentioned precipitated amorphous silica lacks the ability to be formed into particles, but it is surprising that it could be formed into granular silica with a smooth surface and high particle strength by mixing with silica hydrogel. Met.

(Granulation into Granules) According to the present invention, the above silica hydrogel slurry or mixed slurry is spray-dried and granulated into spherical particles having a volume median diameter of 20 to 100 μm. In order to obtain spherical particles with a smooth surface, the SiO ₂ concentration should be 15 to 25% by weight.
It is advantageous to have a high concentration of The dry atmosphere temperature is preferably in the range of 200 to 400 ° C. Since the slurry used in the present invention has a remarkably high SiO ₂ concentration, it has the advantages that the amount of water evaporation is small, the efficiency of spray drying granulation is high, and the energy cost is low.

(Use) The fine spherical silica granules of the present invention have high particle strength, smooth surface, no wear, uniform particle size, and are porous and have adsorption performance and apparent specific gravity. Since it is in an appropriate range, it is a carrier for various polymerization catalysts or other catalysts, a compounding agent for resins and cosmetics, other compositions, a carrier for various chemicals, a spacer, a packing material for chromatography, useful components (fragrance, medicinal effect, etc.). component,
It is used for various purposes such as bactericides, antifungal agents and fertilizer carriers.

Example 1 The true spherical amorphous silica particles according to the present invention obtained by using the silica hydrogel by the gel method will be described below. Silica hydrosol was prepared by reacting No. 3 sodium silicate having a concentration of 22 wt% as SiO ₂ and 45% sulfuric acid, and then allowed to stand to gel the agar-like silica hydrogel to a size of 2 to 5 mm. After crushing, it was thoroughly washed with water. Then, this gel, which was aged for 4 hours under the heat of water at 135 ° C., was coarsely crushed using a Nara crusher M-4 type to obtain S.
After making a water-washed slurry of 18 to 25 wt% as iO ₂ , the slurry was wet-milled under high-speed shearing with a Dyno-mill manufactured by Shinmaru Enterprises Co., Ltd. to obtain 6 kinds of finely-milled slurries having different particle diameters and silica slurry concentrations. It was prepared (the temperature of the slurry was maintained at 50 ° C. or lower during pulverization). Next, 6 kinds of slurries were used for SD manufactured by Ashizawa Niro
-25 spray mist (inlet temperature 2
40 ° C., outlet temperature 100 ° C.) to recover spherical silica gel. The results of the preparation conditions and the physical properties of the obtained silica granules are shown in Table 1, where * 1 indicates the total pore volume and * 2 indicates the mesopore pore volume.

Measurement method (1) Apparent specific gravity The apparent specific gravity was measured according to JIS K-6220.6.8. (2) Specific surface area Sorptomatic Series manufactured by Carlo Erba
s 1800 was used and measured by the BET method. (3) Pore volume 0.5 g of a sample dried at 150 ° C. for 3 hours was charged with a mercury porosimetry horosimeter (Autopore 9 manufactured by Micromeritics).
220) was used to measure the pore size of 18 to 43500 Å to determine the pore volume. (4) Particle Size The particle size was measured by a Coulter counter (TA-II type manufactured by Coulter Electronics Co., Ltd.) using an aperture tube of 50 μm. (5) Primary particle diameter From the photographic image obtained with a scanning electron microscope (Hitachi S-570), representative particles were selected and the diameter of the particle image was measured using a scale to obtain the primary particle diameter.

[0034]

[Table 1]

Example 2 A spherical amorphous silica granule obtained by using a mixed slurry of a silica hydrogel slurry prepared by the gel method and an amorphous silica slurry prepared by the precipitation method, prepared in the same manner as in Example 1. Will be described below. Precipitated silica 22% by weight sodium silicate solution and 10% by weight hydrochloric acid as SiO ₂ are simultaneously added to 15% by weight saline solution. During the pouring, the reaction pH was maintained at 3.5 to 6, and after the pouring, aging was performed for 2 hours while maintaining the pH at 3 to 5. Then, it was filtered and washed with water to obtain amorphous silica by the precipitation method. Simultaneous pouring temperature: 50 to 85 ° C. Aging temperature: 50 to 85 ° C. Silica granules SiO ₂ concentration of 18 and 23 wt% Gel method silica hydrogel finely pulverized slurry (A) with SiO ₂ concentration of 12 wt% A mixture of the precipitated silica cake (B) at a weight ratio of SiO _{2 of} A: B = 8: 2 and 3: 7,
Spray drying was carried out in the same manner as in Example 1 to prepare spherical silica particles. The preparation conditions and the physical properties of the silica granules are shown in Table 2.

[0036]

[Table 2]

Application Example 1 Sample No. obtained in the example. 1-1 Microsphere 100
30 ml of a commercially available liquid deodorant Pancil (manufactured by Release Kagaku Kogyo Co., Ltd.) was added to g to allow sufficient absorption. The obtained sample was a microsphere which was smooth without aggregation.
This sample was placed in an empty bottle of table salt manufactured by Ajinomoto Co., Inc. and left in the room for one month. Then, it was sprinkled on a bag containing garbage in the kitchen, and the dispersibility (sprinkling property) and the deodorizing effect of the sample were evaluated by three panelists, and the results are shown in Table 3. Sample No. obtained similarly as a comparative example. To 100 g of the microspheres of H-1 and H-6, 30 ml of pancil was added, respectively, and they were sufficiently absorbed. As a result, the sample H-1 was crushed and exhibited an aggregated state as a whole, and the dispersibility test could not be performed. On the other hand, Sample H-6 had aggregates of 2 to 3 mm and lacked fluidity.

[0038]

[Table 3]

Description of evaluation symbols in Table 3 Dispersibility ◯: Dust in the bag can be sprinkled uniformly without clogging through the holes of the container. X: The hole of the container is often clogged, and it is difficult to sprinkle it evenly. Odor eliminating effect ○: It can be clearly discriminated by sensory evaluation that the bad odor of dust before use is weakened. X: The difference from before use cannot be determined by sensory evaluation.

Application Example 2 Sample No. obtained in the example. 1-2 micro spheres 50g
Was added to an aqueous solution of permethrin, a hillethroid insecticide, which was stirred by a high stirrer, and the mixture was stirred at 600 rpm for 1 hour.
Stir for 0 minutes. The obtained slurry was The microspheres which had been filtered using the filter paper No. 2 and separated from water were dried in an electric dryer at 110 ° C. for 5 hours. The obtained powder was fine spherical particles with good fluidity without agglomerated particles.

On the other hand, sample N similarly obtained as a comparative example.
o. 50 g of H-2 microspheres were treated as described above. The obtained powder has an aggregate with a diameter of 5 to 8 mm,
It lacked liquidity. The physical properties and the like of the obtained sample are shown in Table 4.

[0042]

[Table 4]

The particle size, angle of repose, and insecticidal effect in Table 4 are as follows. * ^-1 Coulter Counter Method Apatcher tube 4
Using 00 μm (manufactured by Coulter Electronics Co., Ltd.) * ^-2 Powder tester (manufactured by Hosokawa Micron Co., Ltd.) * ^-3 Aphids were placed in a container with powder placed in the center to check the range of movement. ◯: Moved avoiding powder. X: Moved in the container regardless of the powder.

[0044]

As described above, according to the present invention, the surface is smooth under a microscope, there are no cracks on the surface, the particle strength is large, the abrasion tendency is small, the packing volume is compact, and the catalyst and other carriers for chemicals are used. Amorphous silica granules having excellent properties and blending properties with polymers, etc. can be obtained, and since silica hydrogel slurry can be subjected to wet pulverization and spray granulation at high concentration, equipment cost and energy can be reduced. The advantage is that amorphous silica particles can be produced with high productivity while reducing costs.

[0045]

[Brief description of drawings]

FIG. 1 is a plot of the relationship between the hydrogel particle size in a gel method silica hydrogel slurry and the mesopore pore volume of amorphous silica particles produced by the spray method.

FIG. 2 is a scanning electron micrograph showing a particle structure of an amorphous silica granular material (Comparative Example 1) obtained by a spray method in which the mesopores of the silica hydrogel obtained by the gel method is 0.8 cc / g. A is a magnification of 200. , B is a magnification of 1000.

3 is exactly the same as FIG. 2 except that the mesopores in FIG. 2 are 0.7 cc / g (Comparative Example 2).

FIG. 4 is a scanning electron micrograph showing the particle structure of an amorphous silica granular material according to the present invention (Example 1) in which the mesopores of the silica hydrogel by the gel method are 0.4 cc / g.
The magnifications of B and B are the same as in FIG.

FIG. 5 is a graph showing the distribution of the pore volume of various amorphous silica granules with the pore radius as the horizontal axis.
2 is the amorphous silica of FIG. 2, curve B is the amorphous silica of FIG. 3, curve C is the amorphous silica of FIG. 4 and curve D is the amorphous silica of FIG. Further, the pore volume distribution of the one subjected to alkali treatment is shown.

Claims (3)

[Claims] 1. A by reacting an aqueous alkali silicate solution and an acid aqueous solution, a heat treatment-obtained silica hydrogel at a slurry concentration of SiO ₂ concentration of 15 to 25 wt%, 50 ° C.
By wet pulverization at a temperature not exceeding the above and under high-speed shearing to prepare a silica hydrogel slurry having a particle size of 4 μm or less,
A process for producing amorphous silica granules, which comprises spray-drying the silica hydrogel slurry. Wherein reacting an aqueous alkali silicate solution and an acid aqueous solution, the silica hydrogel obtained by a heat treatment at a slurry concentration of SiO ₂ concentration of 15 to 25 wt%, 50 ° C.
By wet pulverization at a temperature not exceeding the above and under high-speed shearing to prepare a silica hydrogel slurry having a particle size of 4 μm or less,
When this silica hydrogel slurry (A) is mixed with the amorphous silica slurry (B) by the precipitation method and the mixed slurry is spray-dried, the silica weight ratio based on SiO ₂ A: B = 9: 1 to 1: 1. A method for producing an amorphous silica granular material, which is in the range of 9. 3. An electron microscopic observation that the surface is composed of perfectly spherical particles without cracks, has a volume-based median diameter of 20 to 100 μm measured by the Coulter counter method, and has an apparent size according to JIS K6220.6.8. Specific gravity is 0.2
To 0.5 g / cc, the pore volume by mercury porosimetry is 0.5 to 3.5 cc / g in the range of pore radius 18 to 43500 angstroms, and B
An amorphous silica granular material having a specific surface area by ET method in the range of 100 to 600 m ² / g.