JPH0725643A - Production of ultrafine hollow glass sphere - Google Patents

Abstract

PURPOSE:To readily obtain the glass spheres while alleviating conditions of a device for burning by treating volcanic glass deposit powder having specific particle diameters with an aqueous solution of an alkali, facilitating heating and expansion by increasing structural water in glass. CONSTITUTION:A naturally productive mineral of volcanic glass deposit powder (e.g. Shirasu, obsidian or perlite) having <=20mum particle diameters is prepared. The mineral powder is hydrothermally treated with an aqueous solution of an alkali to increase structural water in glass necessary for heating and expansion or to reduce the softening temperature of glass. Then, the mineral is burnt at 900-1,100 deg.C for 1-60 seconds and a hollow substance is separated and recovered from the burnt material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultrafine hollow glass spheres. More specifically,
The present invention relates to a method for producing ultrafine hollow glass spheres useful as a material for various lightweight composite materials.

[0002]

2. Description of the Related Art The main mineral component of volcanic glassy deposits is natural glass, and a method for producing super-granular hollow glass spheres from this is known (Japanese Patent Publication No. 48-1).
7645). By the way, most of the loss on ignition of this volcanic vitreous deposit is water, so if this volcanic vitreous deposit is fired under conditions that can simultaneously soften the vitreous and generate steam, it will foam. As a result, hollow glass spheres are obtained.

However, when the fine powder of volcanic glassy deposits having a particle size of 20 μm or less is fired, the diffusion rate of water contained in the glass structure to the outside of the particles is too fast, and appropriate foaming conditions can be obtained. It will be difficult.

On the other hand, there is known a method for producing ultrafine hollow glass spheres by performing heat treatment in an acid solution prior to firing (Japanese Patent Publication No. 4-296750). However, this method requires corrosion-resistant material because it causes corrosion of the device by acid, and is not suitable for industrial use.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks associated with the production of ultrafine hollow glass spheres from volcanic glassy deposits as a raw material by the conventional method, and provides ultrafine hollow glass spheres. It was made for the purpose of providing an industrially practicable method for efficient production.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted diligent research to develop a method suitable for industrially producing ultrafine hollow glass spheres, and as a result, volcanic glass deposition It was found that the object can be achieved by pulverizing the product to a particle size of 20 μm and then heat-treating it in an alkaline aqueous solution prior to firing, and completed the present invention based on this finding.

That is, in the present invention, a volcanic glass deposit powder having a particle size of 20 μm or less is heat-treated in an alkaline aqueous solution, and alkali is eluted with an acid as desired,
The present invention provides a method for producing an ultrafine hollow glass sphere, which comprises firing at 900 to 1100 ° C for 1 to 60 seconds and separating and recovering the hollow body from the fired product.

In the method of the present invention, the volcanic glassy deposit used as a raw material is a naturally occurring mineral such as shirasu, obsidian, pearlite and pinelite, and these are usually SiO ₂ , Al ₂ O ₃ and Fe. ₂ O ₃ , CaO, MgO,
Consists of Na ₂ O and K ₂ O, water content 3-10% by weight
Is included.

In the method of the present invention, these volcanic glassy deposits are crushed, and the pulverized products are classified into 20 μm or smaller sections for use.

In the method of the present invention, this particle size is 20 μm.
The following volcanic glass deposit powder is then heat treated in aqueous alkaline solution. At this time, as the alkali, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide or the like is used. The concentration of the alkaline aqueous solution is 0.0 in the case of potassium hydroxide or sodium hydroxide.
It is preferably about 5 to 1.0 mol / liter, and in the case of calcium hydroxide, the solubility is low, so a saturated aqueous solution is usually used. The alkaline aqueous solution is usually used in an amount of 1 to 10 times the weight of the volcanic glassy deposit powder.

The heat treatment with the alkaline aqueous solution is preferably a so-called hydrothermal treatment, which is carried out by raising the temperature and pressure in a closed container, whereby the structural water in the glass, which is indispensable for the heat-foaming, increases, and the heat-foaming is easier Becomes The heat treatment temperature is usually selected in the range of 100 to 200 ° C., and
The treatment time is short when the temperature is high and long when the temperature is low. For example, when the treatment is performed at a temperature of about 150 ° C., the treatment time is about 4 to 100 hours.

By this heat treatment with the alkaline aqueous solution, the silica network structure in the volcanic glassy deposit is cut, the softening temperature of the glass is lowered, and as described above, the structural water in the particles is increased. In the heat treatment described later, heat-foaming easily occurs, and it becomes possible to form ultrafine hollow glass spheres.

The volcanic glassy deposit thus heat-treated with the alkaline aqueous solution is washed with water as desired, then dried and calcined. Can also be eluted. Since the content of iron and alkali metals in the surface layer decreases when this elution treatment with acid is performed, it is possible to prevent fusion during firing, and also to prevent coloring due to oxidation of iron by deironing only the surface layer. The resulting ultrafine hollow glass sphere becomes white. The acid at this time is usually 0.1 to 1.0.
An aqueous solution of hydrochloric acid or sulfuric acid having a mol / l concentration is used.

Next, firing is performed to remove 900 volcanic glassy deposits.
It is carried out by maintaining the temperature in the range of ˜1100 ° C. for 1 to 60 seconds. By this baking treatment, softening of glass and generation of water vapor occur at the same time, and ultrafine hollow glass spheres are formed. Next, the hollow body is separated and recovered by floating / settling separation in water or air classification. In this way, good quality ultrafine hollow glass spheres can be obtained.

[0015]

Industrial Applicability The method for producing ultrafine hollow glass spheres of the present invention is a method in which a volcanic glassy deposit, which is one of the unused resources, is used as a raw material, and a heat treatment with an alkaline aqueous solution is performed as a pretreatment. By adopting it, compared to the conventional heat treatment with an acid solution, the selection of material for the treatment equipment can be greatly eased, which is industrially advantageous, and the ultrafine and white hollow glass spheres can be used in the furnace. It is possible to manufacture without fusion.

The hollow glass spheres obtained by the method of the present invention are ultrafine particles and are inorganic substances having a particle density of 1 g / cm ³ or less, and are therefore useful for various applications such as materials for various lightweight composite materials. .

[0017]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Examples 1 and 2 Volcanic glassy deposits from Yoshida Town, Kagoshima Prefecture, commonly known as Yoshida Shirasu, were crushed for 8 hours with a porcelain pot mill, and then powdered in a particle size range of 5 to 10 μm with tap water (tap bulk density 0. 83
g / cm ³ and air displacement particle density 2.33 g / cm ³ ) were obtained. The composition of this Yoshida Shirasu is SiO ₂ 70.
54 wt%, Al ₂ O ₃ 13.10 wt%, Fe ₂ O
₃ 1.82 wt%, CaO 0.53 wt%, MgO
0.48 wt%, Na ₂ O 3.60 wt%, K ₂ O
The amount was 2.90 wt% and the loss on ignition was 6.05 wt%.

Into a pressure vessel made of stainless steel, the powder raw material and an aqueous solution of sodium hydroxide having a concentration of 5 ml / g and a concentration of 0.1 mol / liter with respect to the powder were placed, and the mixture was kept at 150 ° C. for 24 hours in a closed system. After holding, cool, wash with water,
Dried. The unheated powder having a particle size range of 5 to 10 μm recovered by hydration had a heating loss of 5.40 wt%, whereas the alkali-treated powder had a heating loss of 5.85 wt%.
Increased.

Next, the above-mentioned powder is heated from room temperature to 1000 ° C. or 1100 ° C. within 1 minute, and the temperature is raised to 10 ° C.
After holding for 2 seconds and firing at an air volume of 8 liters / minute,
Floating and sedimentation was performed in water, and ultrafine hollow glass spheres were collected as a float.

In the heat treatment, even if the holding time at 1000 ° C. was set to 1 minute or more, the recovery ratio of the ultrafine hollow glass spheres did not change in both untreated and treated powders.

When the maximum temperature in the furnace was raised to 1100 ° C., the recovery rate of the ultrafine hollow glass spheres increased in both the untreated and treated powders, but the ratio with the untreated powder remained unchanged. However, at 1100 ° C. or higher, fusion in the furnace occurred, making it difficult to recover the heat-treated product. Moreover, as the maximum temperature in the furnace became lower than 1000 ° C., the recovery ratio of the ultrafine hollow glass spheres gradually decreased, and it could not be recovered at 900 ° C.

When the concentration of sodium hydroxide is 0.5 mol / liter, or when the concentration is 0.2 mol / liter and the holding time is 48 hours or more, the powder is solidified in the pretreatment container and It was difficult to process. Table 1 shows the hydrothermal treatment and heat treatment conditions, and Table 2 shows the respective results.

Examples 3 to 6 Yoshida Shirasu powder having the same particle size range of 5 to 10 μm as that used in Example 1 was added at a concentration of 5 mol / g and a concentration of 0.05 mol / l or 0.1 mol / g. It was immersed in 1 liter of an aqueous solution of sodium hydroxide, kept for 24 hours or 72 hours, washed with water, dried, then immersed in 0.55N hydrochloric acid and treated for 24 hours. Then, this treated product is taken out, washed with water, dried, and then 1000 ° C. or 1100 ° C.
The temperature was raised to within 1 minute within 1 minute, and the temperature was maintained for 10 seconds for firing. A hollow body was recovered from this fired product in the same manner as in Example 1. Table 1 shows the treatment conditions at this time, and Table 2 shows the density of the burned material and the recovery rate of the hollow bodies (underwater floating rate).
Shown in.

Example 7 The same procedure as in Example 1 was carried out using the same amount of a saturated aqueous solution of calcium hydroxide instead of the aqueous sodium hydroxide solution in Example 1. Table 1 shows the treatment conditions at this time, and Table 2 shows the density of the fired product and the recovery rate of the hollow bodies (underwater floating rate).

Examples 8 and 9 A saturated aqueous solution of calcium hydroxide was used in place of the aqueous solution of sodium hydroxide in Example 3, heat treatment was performed in an alkali, and then acid treatment was performed. To obtain a hollow body. Table 1 shows the treatment conditions at this time, and Table 2 shows the density of the fired product and the recovery rate of the hollow bodies (underwater floating rate).

[0027]

[Table 1]

[0028]

[Table 2]

Comparative Example For comparison, Yoshida Shirasu powder having a particle size range of 5 to 10 μm was subjected to 100 as it was without any alkali treatment.
Table 2 shows the density of the fired product obtained by performing the firing treatment at 0 ° C. for 10 seconds and the recovery rate of the hollow bodies (floating rate in water).

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Kenichiro Matsuda, Inventor Kenichiro Matsuda, Ichihara City, Chiba Prefecture, No. 8 Goi Minami Kaigan No. 8 Stock Company, Calced (72) Inventor Fumio Fukagawa, No. 4611, Isa Town, Mine City, Yamaguchi Prefecture Company Calcied (72) Inventor Hiromi Okada 8-2 Goi Minami Kaigan, Ichihara, Chiba Stock Company Company Calcied

Claims (2)

[Claims] 1. A volcanic glass deposit powder having a particle size of 20 μm or less is heat treated in an alkaline aqueous solution, and then 900 to
A method for producing an ultrafine hollow glass sphere, which comprises firing at 1100 ° C. for 1 to 60 seconds and separating and recovering the hollow body from the fired product. 2. A volcanic glass deposit powder having a particle size of 20 μm or less is heat-treated in an alkaline aqueous solution, and then alkali on the surface is eluted with an acid, and then 900 to 1100.
A method for producing an ultrafine hollow glass sphere, which comprises firing at 1 ° C for 1 to 60 seconds, and separating and recovering the hollow body from the fired product.