JPH0761810A - Surface modified silicon dioxide fine powder - Google Patents

Abstract

(57) [Summary] [Structure] A silicon dioxide fine powder that has been surface-modified with an organosilicon compound and then consolidated by mechanical coagulation treatment, and the change in bulk density after consolidation is within ± 20%. Characteristic silicon dioxide powder. [Effect] Since the bulk density hardly changes, there is no change in volume even when the powder filled in the container is transferred to a duct, a hopper or the like and pneumatically transported or stirred, which is suitable for processing such as quantitative transportation and quantitative feeding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-modified silicon dioxide powder which, after being filled in a container, has a bulk density which hardly changes even if an external force is applied thereto and maintains a compacted state.

[0002]

2. Description of the Related Art Silicon dioxide powder is widely used as a filler for various resin compositions and as an aid for improving the fluidity of powder. Conventionally, this silicon dioxide powder has been subjected to surface modification (hydrophobization treatment) with an organosilicon compound in order to improve dispersibility in a resin or powder, and then pressing or vacuum deaeration to consolidate the powder. It is known to increase bulk density. It is also known that this surface modification is carried out simultaneously with mechanical grinding to increase the bulk density (Japanese Patent Publication No. 52-3829). The surface-modified silicon dioxide powder having an increased bulk density has the advantages that the addition time is shortened when it is added to various resin compositions, and the generation of dust is small.

However, any of the conventional silicon dioxide powders whose bulk density has been increased by the above-mentioned method has a problem that the bulk density gradually decreases when an external force is applied after filling the container.
As an example, the conventional powder obtained by pressing the hydrophobized surface-modified silicon dioxide powder to a bulk density of about 150 g / l has a rapid decrease in the bulk density during repeated air transportation in the duct. It is about one-third (less than 50 g / l). Therefore, when the silicon dioxide powder is packed in a container for transportation, pneumatic transportation is performed using a duct, or stirring is performed in the container, the volume of the powder increases, which causes a problem.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a silicon dioxide powder which solves the above problems of the conventional surface modified silicon dioxide powder. The present inventor has proceeded with the investigation on the reduction of the bulk density, and, contrary to the conventional treatment method, if mechanical coagulation treatment is carried out after modifying the surface of the silicon dioxide powder with an organic silicon compound, then vibration is generated. It has been found that the bulk density does not decrease even when an external force such as a pump pressure is applied, and a stable consolidated state is maintained. The present invention has solved the above-mentioned conventional problems based on such knowledge.

[0005]

According to the present invention, the following surface-modified silicon dioxide fine powder is provided. (1) A silicon dioxide fine powder that has been surface-modified with an organosilicon compound and then consolidated by mechanical coagulation treatment, wherein the change in bulk density after consolidation is within ± 20%. . (2) The silicon dioxide powder according to (1) above, which has been surface-modified with an organosilicon compound and then introduced into a pulverizer for mechanical coagulation.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The fine powder of silicon dioxide used in the present invention is produced, for example, by flame hydrolysis of halogenated silane described in JP-B-47-46274. According to this method, silicon tetrachloride gas is passed through a flame of oxygen and hydrogen and hydrolyzed at high temperature to obtain fine particles of silicon dioxide.

The surface of the above silicon dioxide fine powder is modified by a hydrophobic treatment. The organosilicon compound used may be any one generally used as a hydrophobizing agent. This hydrophobizing agent is a compound which binds to and blocks a hydroxyl group on the surface of silicon dioxide powder and which itself has a hydrophobic group. Practically used compounds are a silane coupling agent having a hydrophobic group and a silylating agent. And specifically, for example, an organosiloxane such as hexamethyldisilazane, hexamethyldisiloxane, trimethylsilanol, trimethylsilane ethoxide, trimethylsilane methoxide, or an organopolysiloxane.

In practice, the amount of the organic silicon compound used as a hydrophobizing agent is preferably about 0.5 to 40% by weight based on the raw material silicon dioxide fine powder. Usage is 0.
If it is less than 5% by weight, the effect of hydrophobizing is low, and even if the amount used exceeds 40% by weight, the effect of hydrophobizing is not significantly different. As an example of the hydrophobic treatment, that is, the surface modification treatment, the organosilicon compound is mixed with the silicon dioxide powder in an inert gas atmosphere at a temperature range of 60 ° C. to 350 ° C.
It may be held for 4 minutes to 4 hours and then dried to remove unreacted substances and by-products. Oxidation of the hydrophobizing agent is prevented by carrying out the hydrophobizing reaction in an inert gas atmosphere. If the reaction temperature is lower than 60 ° C, the hydrophobizing reaction does not proceed sufficiently, and if it is higher than 350 ° C, the hydrophobizing agent is thermally decomposed, which is not preferable.

The silicon dioxide powder surface-modified by such a hydrophobizing treatment is subjected to a mechanical aggregating treatment. Here, the mechanical agglomeration treatment means that the mechanical pulverization and the agglomeration are simultaneously performed by utilizing the mechanical pulverization force. By this mechanical coagulation treatment, the silicon dioxide powder is compacted and the bulk density is increased. Incidentally, since the powder is pulverized and agglomerated at the same time, the average particle size of the powder does not change apparently. For the mechanical coagulation treatment, a usual crusher such as a ball mill, a conical mill, or a tower mill can be used. Further, it may be one that utilizes the grinding force such as a stone mill. The treatment conditions are also not particularly limited. As an example, in order to obtain a fine powder having a bulk density of 80 to 300 g / l, a surface-modified silicon dioxide powder having a specific surface area of 100 to 200 m ² / g is subjected to a ball mill at a rotation speed of 10 to 100 rpm for 5 minutes to 5 hours. Just handle it.

After the hydrophobic treatment, the bulk density is increased by consolidating by the mechanical coagulation treatment, and the bulk density hardly changes even if external force is applied after the powder is filled in the container. That is, it is possible to obtain a fine powder having a change in bulk density within ± 20% even when subjected to an external force such as vibration or pump pressure after compaction. On the other hand, as in the conventional method, a method of mechanically aggregating with a ball mill at the same time as the hydrophobizing treatment, a method of hydrophobizing after mechanically agglomerating the silicon dioxide powder, or pressing or vacuum releasing after the hydrophobizing. It is not possible to obtain a fine powder whose bulk density does not change as in the present invention by the method of compacting by air. Although the reason for this is not clear, a certain amount of the silicon dioxide fine powder according to the present invention is placed in a graduated cylinder, and the bulk density (tap density) of the silicon dioxide powder inside does not change even if a light shock is applied to this container, Although the volume of the powder is almost the same, the conventional silicon dioxide powder, which has been subjected to the mechanical treatment and the hydrophobic treatment at the same time, has a bulk specific gravity (tap density) due to impact when tested under the same conditions.
Is significantly reduced and the volume inside the graduated cylinder is increased by about 50%, and the two can be clearly distinguished. The same phenomenon is observed in the conventional silicon dioxide powder that has been subjected to the hydrophobic treatment after the mechanical coagulation treatment.

[0011]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the present invention are shown together with comparative examples. The following examples are illustrative and do not limit the scope of the present invention.

Example 1 200 g of silicon dioxide powder having an average particle size of 12 mμ (Aerosil-200 manufactured by Nippon Aerosil Co., Ltd.) was mixed with 13 g of hexamethyldisilazane, and the mixture was heat treated at 150 ° C. to give 211 g of hydrophobicity. An oxidised silicon dioxide powder was obtained. The bulk density of this silicon dioxide powder was 52 g / l.
This silicon dioxide powder was mechanically agglomerated using a stone mill consisting of two stone plates having a diameter of 30 cm and a thickness of 10 cm to obtain a fine powder having a bulk density of 240 g / l. When this powder was pneumatically transported using a diaphragm pump, as shown in FIG. 1, the bulk density was 210-240 g /
The change was within the range of ± 15%, which was extremely small.

Example 2 200 g of hydrophobized silicon dioxide powder having an average particle diameter of 14 mμ and a bulk density of 51 g / l (manufactured by Nippon Aerosil Co., Ltd .: RY-200) was placed in a vibration mill and mechanically agglomerated to give a bulk density of 150. g
A fine powder of / l was obtained. When this powder was pneumatically transported using a diaphragm pump under the same conditions as in Example 1, as shown in FIG. 1, even if the transportation was repeated, the bulk density was 140 to
It was 150 g / l, and the change in bulk density was about 6%, which was almost unchanged.

Example 3 Hydrophobization was carried out in the same manner as in Example 1 except that 100 kg of silicon dioxide powder having an average particle size of 12 mμ (Aerosil-200 manufactured by Nippon Aerosil Co., Ltd.) was used and 6.5 kg of hexamethyldisilazane was used. A silicon dioxide powder (bulk density 49 g / l) was obtained. The silicon dioxide powder was mechanically agglomerated using a tower mill having an inner diameter of 30 cm and a height of 100 cm to obtain a fine powder having a bulk density of 110 g / l. When this powder was pneumatically transported using a diaphragm pump under the same conditions as in Example 1, as shown in FIG. 1, the bulk density was 100 to 12 even if the transportation was repeated.
0 g / l The change was within a range of ± 20% and was very slight.

Comparative Example 1 The hydrophobized silicon dioxide powder obtained in Example 1 was packaged without mechanical coagulation treatment, sandwiched between iron plates and pressed from both sides to consolidate. The bulk density after compaction was 80 g / l. When this powder was pneumatically transported using a diaphragm pump in the same manner as in Example 1, as shown in FIG. 1, the bulk density significantly decreased to about 40 g / l in the first and second transportation (Comparative Example 1- 1). Further, the packed silicon dioxide powder was compacted by vacuum deaeration instead of pressing to consolidate, and the bulk density was 100 g / l. When this powder was similarly pneumatically transported using a diaphragm pump, as shown in FIG. 1, the bulk density significantly decreased to about 40 g / l during the first and second transports (Comparative Example 1-2).

Comparative Example 2 13 g of hexamethyldisilazane was added to 200 g of silicon dioxide powder (Aerosil-200 manufactured by Nippon Aerosil Co., Ltd.) having an average particle diameter of 12 mμ, and the mixture was put into a vibration mill having a capacity of 5 liters. It was kept at 70 ° C. and subjected to mechanical coagulation treatment for 2 hours. Thus, the bulk density of the silicon dioxide powder subjected to the mechanical coagulation treatment and the hydrophobization treatment at the same time was 120 g / l.
When this powder was pneumatically transported using a diaphragm pump under the same conditions as in Example 1, as shown in FIG.
The bulk density was greatly reduced to about 50 g / l by the second transportation (Comparative Example 2-1). Further, 200 g of silicon dioxide powder having an average particle diameter of 12 mμ (Aerosil-200 manufactured by Nippon Aerosil Co., Ltd.) was put into a vibration mill having a capacity of 5 liters, and mechanical coagulation treatment was performed for 2 hours. Then, 13 g of hexamethyldisilazane was added to and mixed with this powder, and heat treated at 150 ° C. to obtain 211 g.
A hydrophobized silicon dioxide powder was obtained. The bulk density of this powder was 150 g / l. When this powder was pneumatically transported using a diaphragm pump under the same conditions as in Example 1,
As shown in FIG. 1, the bulk density was 70 in the first and second transportation.
It was significantly reduced to about g / l (Comparative Example 2-2).

[0017]

The silicon dioxide powder of the present invention is compacted by mechanical coagulation treatment and its bulk density hardly changes. Therefore, the powder filled in a container is transferred to a duct or a hopper for pneumatic transportation or stirring. Even when it is used, the volume does not change, and it is suitable for processing such as quantitative transportation and quantitative feeding.

[Brief description of drawings]

FIG. 1 is a graph showing changes in bulk density of Examples and Comparative Examples.

Claims (2)

[Claims] 1. A silicon dioxide fine powder which has been surface-modified with an organosilicon compound and then consolidated by mechanical coagulation treatment, wherein the change in bulk density after consolidation is within ± 20%. Silicon powder. 2. The silicon dioxide powder according to claim 1, which has been surface-modified with an organosilicon compound and then introduced into a pulverizer for mechanical coagulation.