JPH05221687A - Fine spherular inorganic foam having thick skin shell and its production - Google Patents

Abstract

PURPOSE:To provide a fine spherular inorganic foam formed from natural glass as a raw material, having a compression strength capable of being used as a composite material, a spherular shape and a thick skin shell, and further to provide a method for massively producing the foam. CONSTITUTION:The subject fine spherular inorganic foam having a thick skin shell is characterized by comprising the 40-300mum diameter fine spherular particles of natural glassy rock and having a particle skin shell thickness of 6-30mum and a compression strength of >=60%. The method for producing the fine spherular inorganic foam is characterized by grinding natural glassy rock, preliminarily arranging the ground product into particles having diameters of <=300mum and subsequently spraying the arranged particle raw material together with a carrier gas into a flame having a maximum temperature of >2000 deg.C to melt, foam and sphere the particulate raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine spherical inorganic foam having a thick shell made of natural glass as a main raw material and excellent in compressive strength, and a method for producing the same.

[0002]

2. Description of the Related Art Natural vitreous rocks such as obsidian, pearlite, pinelite, etc. are crushed and sized, and then rapidly heated to soften the glass and simultaneously release bound water. So-called expanded perlite and so on. These foams are mixed with various industrial materials such as organic, inorganic, and metal and used as composite materials having functions such as light weight, heat resistance, heat insulation, heat retention, and soundproofing. While these foams have many advantages, they have some disadvantageous properties. For example,
Most of them have a cell-like internal structure, and thus the particle shape is a bumpy body having a surface with many irregularities. In addition, the shell of these particles, including spherical particles, is made of a glass film that is thinly stretched by expansion, and has a thin wall thickness of 1.5 to 2 μm, which is inferior in compression strength to general industrial materials, and When used as a material, it easily becomes powder. Further, even after expansion of these foams, the surface crust is exfoliated due to friction between the particles and often takes on the shape of squid chestnut. In such a state, the water absorption becomes high, and in some cases, the heat insulating property may be affected. Furthermore, those containing hump-shaped particles and squid-shaped particles have poor fluidity as compared with spherical particles. As these defects are caused by particles, especially the strength and shape of the shell, attempts have been made to granulate the foam or improve the water absorption as a fine spherical foam or develop the strength.
[Tiz, 103

[9] 535 / 538.1979, JP-A-62-41780]. In the former case, it is described that pearlite is finely crushed, and an alkaline solution is added thereto, followed by press molding or granulation and then firing to obtain granules having a particle diameter of 3 to 40 mm. In the latter case, obsidian is wet pulverized to 20 μm or less, dried, and then heated in an electrically heated tubular furnace at a heating rate of 20 ° C./sec.
It is fired for 20 to 30 seconds in an atmosphere of 950 ° C. to obtain a fine spherical foam having a cell-like structure and having a diameter of 1 to 40 μm.

[0003]

However, the former granules have a coarse particle size of 3 to 40 mm, and do not satisfy the intended use function as a filler by the present inventors.
Moreover, there is a drawback that the fine crushing and molding of the raw stones are complicated and the process is not economical. On the other hand, the latter fine spherical foam has an excessively small particle size and is economical because it has wet crushing and drying processes. Not only that, but because of the cell structure, the shell thickness is also insufficient. By mixing with various industrial materials such as organic, inorganic, and metal, it has the functions of light weight, heat resistance, heat insulation, heat retention, sound insulation, etc. It is insufficient to be used as a composite material in that it is difficult to exhibit the composite action effect. Therefore, in view of the state of the art, the present invention is a fine spherical inorganic foam having a compressive strength that can be used as a composite material using natural glass as a raw material, a spherical particle shape, and a thick shell. The purpose is to produce the body in large quantities.

[0004]

According to the present invention, when natural glassy rocks having a certain particle size range are blown into a flame at 2000 ° C. or higher, a natural glassy fine particle having a particle size of 40 to 300 μm and excellent in compressive strength is obtained. It was made paying attention to the fact that a spherical inorganic foam can be obtained. It is a microsphere made of natural glassy rock and having a particle size of 40 to 300 μm, and a particle shell has a thickness of 6
A natural glassy fine spherical foam having a compressive strength of 60% or more. Examples of the natural glassy rock include obsidian, pearlite and pine rock, and those used as natural glass ore are used. The above-mentioned foam is crushed from the above-mentioned natural glassy rock, and then sized in advance to 300 μm or less, preferably 50 to 200 μm, and the sized raw material is blown together with a carrier gas into a flame exceeding a maximum temperature of 2000 ° C. to melt, foam, and spheroidize. It can be manufactured by performing. Therefore, the present invention is a natural glassy material in which the above natural glassy rock is crushed to 300 μm or less in advance, and the sized material is blown together with a carrier gas into a flame exceeding a maximum temperature of 2000 ° C. to melt, foam and spheroidize. It also provides a method for producing a fine spherical foam.

[0005]

The reason why a natural glassy foam having a thick shell is obtained by the method of the present invention is not clear. However, even if the same raw material is used, in the conventional case, it is produced in a rotary kiln or a vertical kiln. , Most of the raw material is charged and expanded toward the maximum temperature of the flame, but the maximum temperature is 1
It is around 500 ° C. On the other hand, in the present invention, a flame having a maximum temperature exceeding 2000 ° C. is produced by combining propane gas and oxygen gas, or propane gas and oxygen-enriched air, or hydrogen gas and oxygen gas.
Thickening the shell of spherical expanded particles during flight in a flame stream in order to blow raw material powder with oxygen-enriched air or carrier gas such as air to instantly cause melting, foaming and spheroidizing of raw material particles. Is expected to be achieved. Therefore, it is the load heat amount that mainly controls the thickness of the shell of the spherical expanded particles, and the conditions to control this load heat amount are the weight of the feed raw material powder per unit time and the amount of fuel gas used. In addition, the ratio of the theoretical oxygen amount is particularly important.

The shell thickness of this spherical foam treated under the above optimum conditions is 6 to 30 μm, and especially the foam particle size is 4
It is in the range of 0 to 300 μm, and the particle shell is 6 to 30 μm.
Those having the above have a compressive strength of 60%, preferably 65% or more, and have a compressive strength preferable as a composite material. It is contrasted with the fact that a foam having a particle size of 300 μm or more having an equivalent shell thickness does not have a compressive strength of 60% and the particle shape is a non-spherical bump shape (see Table 2). ). In the present invention, the reason why the particle size is 40 to 300 μm is that if it is 40 μm or less, it is too small to form a foamed body.
This is because if it is more than 00 μm, it is difficult to form a spherical body. Further, even when the foam particle size is in the range of 40 to 300 μm, the strength decreases when the shell wall thickness is less than 6 μm, and the surface shell of the particle is exfoliated due to friction between particles, and the heat insulating property and soundproofing property also decrease. On the other hand, if it exceeds 30 μm, on the other hand, the amount of fuel used by the heating element increases and the manufacturing efficiency deteriorates. The compressive strength referred to here is the residual volume ratio after pressing the natural filler at 80 kg / cm ² .

Since the particle size of the foam produced by the present invention is controlled by the particle size of the raw material, the particle size of the raw material such as obsidian, pearlite and pine rock used as natural glassy rock is 40
In order to obtain a spherical foam having a size of μm or more and 300 μm or less, the raw material is pulverized and then sized in advance in a range of particle size smaller than 300 μm,
It is necessary to suppress the generation of fine powder having a size of 40 μm or less during pulverization as much as possible. This is because it is difficult for a raw material having a thickness of more than 300 μm to form a predetermined thickness, and if the thickness is less than 40 μm, the thermal efficiency in the space portion due to flame injection tends to deteriorate. Therefore, the raw material particle size is preferably in the range of 50 to 200 μm. For that purpose, it is economical to use a crusher such as a cage mill that generates less fine powder. The adhering water of the pulverized material needs to be dried and removed in advance, but preheating for making an appropriate amount of the bound water contained in the natural glassy raw material is not required.

A flame injection burner is usually used to generate a flame temperature exceeding 2000 ° C., but especially Bernoulli-type flame burner, petroleum for high-purity magnesia clinker sintering, rotary kiln burner using coke, damage to refractory furnace wall It is possible to use a flame-retardant sprayed burner for part repair. The flame burner can be blown from either the upper part, the lower part, or the side body of the spherical foam generation furnace, and the furnace body is made of refractory bricks or amorphous refractory inside the iron shell, It is desirable to choose a spall lining. It is also desirable to blow cold air to the inner wall of the furnace to lower the temperature of the inner wall for the purpose of preventing the spherical foam from welding to the inner surface of the furnace wall, and at the same time, to assist the transfer of the foam to the collector. Product recovery is done with normal cyclones and bag filters.

Next, an example of a method for producing the fine spherical inorganic foam having a thick shell of the present invention will be described.

[0010]

EXAMPLE The natural glass raw material used in the present invention is a pearlitic volcanic glass, and one example of its chemical composition is shown in Table 1. This pearlite has a high K ₂ O / Na ₂ O of 1.76,
The burning loss is 5.25%, and it has bound water close to pine rock in the general concept. The rough stone is roughly crushed, dried at 150 to 200 ° C, crushed with a cage mill, sieved, and the particle size is 250 μm.
Less than 10%, and less than 45 μm 10%
The following particle sizes were used, and those having an average particle size of 100 μm were used. A commercially available propane oxygen flame burner was used for the heat treatment. Supply ratio of raw material powder is 1 for 1 m ³ of propane gas
It was set to 0 kg.

[0011]

[Table 1]

The product of the present invention produced at a flame temperature of 2000 ° C. or more (raw material particle size 40 to 300 μm), and the comparative product 1 produced by the same method as the product of the present invention (raw material particle size 300 to 60).
0 μm) and the characteristics of the expanded perlite comparative product 2 (raw material particle size 45 to 800) produced by the conventional method are shown in Table 2. The characteristics of the inorganic foam according to the present invention are compared with the expanded perlite prepared by the conventional method (Comparative Example 2) as follows. In the product of the present invention, as shown in FIG. 1, the inorganic foam particles have a substantially spherical shape, and the particle diameter is 40 to 300 μm. Moreover,
As shown in FIG. 2, the inside of the particle does not have a cell structure (partition wall) and often contains spherical bubbles. In some cases, it is difficult to distinguish between the skin shell portion and the central air bubble portion with fine particles, and the thickness of the shell of the spherical foam extends from 6 μm to 30 μm, and the bulk density is 0.60. On the other hand, in the case of Comparative Example 2, since the expansion ratio is large, the bulk density is as small as 0.20, the particle shape is not only a hump-like body, but the shell thickness is 2 to 4 μm.
It is thin with m. As for the chemical composition of the foam, Na ₂ O decreased compared to the raw material, and the K ₂ O / Na ₂ O ratio increased to 2.31. This supports the fact that the viscosity of the molten glass is further increased, which helps to form a strong crust. In the conventional manufacturing method, this tendency is not observed because the firing temperature is low. The compressive strength of the product of the present invention, which is expressed by the residual volume ratio, is 1.5 times or more higher than that of the conventional product.
Although the foam of Comparative Example 1 produced in the same step as the method of the present invention may have the same shell thickness, the bulk density is small and the compressive strength is not so improved as compared with the conventional method.

[0013]

[Table 2]

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a particle shape showing a structure of a fine spherical inorganic foam of the present invention.

FIG. 2 is a scanning electron micrograph showing a structure of a fracture surface of the particles.

Claims (2)

[Claims] 1. A natural glassy rock having a particle size of 40 to 300 μm.
m microspheres, the particle shell has a thickness of 6 to 30 μm,
A natural glassy fine spherical foam having a compressive strength of 60% or more. 2. The natural glassy rock is pulverized to 300 μm in advance.
A fine spherical inorganic foam having a thick-shelled shell characterized by being sized to m or less and blowing the sized raw material together with a carrier gas into a fire exceeding a maximum temperature of 2000 ° C. for melting, foaming and spheroidizing. Production method.