JPH044278B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing ceramic foam using volcanic ejecta.

[Conventional technology]

A lot of research has been done on ceramic foam in the past, but all of them have had their pros and cons. For example, JP-A-56-109859 describes a method in which granulated blast furnace slag is heated and foamed by adding a silicic acid-containing substance such as silica sand, a binder, and silicon carbide as a foaming aid. However, granulated blast furnace slag is not available everywhere and its quality is not consistent, making it difficult to produce products of consistent quality.

Further, Japanese Patent Publication No. 56-14627 describes heating and foaming volcanic ejecta such as whitebait, blast furnace water slag, and a water glass composition. However, the foam made by this method has the disadvantage that it is difficult to obtain a uniformly foamed product and also has low mechanical strength.

[Problems to be Solved by the Invention] The present inventors conducted research in order to eliminate the above-mentioned drawbacks such as difficulty in obtaining raw materials, inconsistent quality, and low mechanical strength. As a result, the present inventors discovered that volcanic ejecta, limestone, etc. distributed throughout Japan.
Formation of foams using CaO compounds, especially
The present invention was completed by discovering that a foam with strong mechanical strength can be obtained by adding a CaO compound.

[Means to solve the problem]

That is, the gist of the present invention is to add silicon carbide to 60 to 90 parts by weight of volcanic ejecta and 40 to 10 parts by weight of CaO compound, mix them and mold them into a predetermined shape, and then mold this molded product to 900 parts by weight. The present invention relates to a method for producing a ceramic foam, which is characterized by foaming by heating to ~1250°C.

[Effect]

Since the present invention has the above-mentioned composition, a ceramic foam of constant quality can be obtained at a relatively low temperature, and the mechanical strength of the ceramic foam is strong.

Further, since the raw material is foamed after being molded into a predetermined shape, there is no distortion and it is easy to obtain a ceramic foam having a desired shape.

The volcanic ejecta used in the present invention includes volcanic rock,
It is volcanic ash, etc., and its chemical composition is
It is preferable that SiO ₂ is contained in an amount of 45 to 80% and Al ₂ O ₃ is contained in an amount of 5 to 25%. Examples of the above-mentioned volcanic ejecta include volcanic ash such as shirasu, obsidian, pearlite, rosinite, and pumice; altered volcanic ash such as white clay and bentonite; andesite, basalt, anti-pyrosite, and rhyolite;
Examples include volcanic rocks such as granite, feldspar, and rouseki.

In addition to calcium oxide, the CaO compounds used in the present invention include calcium hydroxide, calcium carbonate, calcium oxalate, etc., which decompose into CaO, and these compounds generally exist in large amounts naturally as limestone, lime, etc. can be used.

The silicon carbide used in the present invention acts as a foaming agent, and when heated together with the above volcanic ejecta and CaO compound to a temperature of about 900°C or higher, SiC + 2O ₂ →
It decomposes into SiO ₂ + CO ₂ and generates carbon dioxide gas.

In the present invention, the volcanic ejecta and the CaO compound are mixed at a ratio of 60 to 90 parts by weight and 40 to 10 parts by weight, respectively, to help melt the volcanic ejecta and the CaO compound and facilitate foaming. For this purpose, water glass, glass powder, or crushed fragments of the foam of the present invention may be added as an auxiliary agent. The amount added is preferably 20 parts by weight or less, more preferably 10 parts by weight or less for water glass or glass powder. If more than 20 parts by weight is added, the heat resistance will be poor and it will be difficult to foam uniformly. No matter how much debris was added to the foam of the present invention, it had no effect on the physical properties. Addition of once melted material, such as foam fragments, is particularly preferred since the mixture will melt more evenly.

Silicon carbide serves as a foaming agent, and the amount used varies depending on the desired foaming ratio of the product, but in most cases, 1 part by weight or less is sufficient.

In the present invention, each composition is made into a fine powder, mixed in a desired proportion, water is added if necessary, kneaded, and molded, or each fine powder mixture is press molded. Adding water improves the adhesion between powder particles and the reaction proceeds uniformly. The shape to be molded is a predetermined shape such as a reduced shape of the final product. The thus formed product is heated and foamed using an electric furnace, tunnel furnace, etc.

Heating temperature is 900℃~1250℃, preferably
The temperature is 1100°C to 1250°C. Heat the molded product to 900℃
Continuing to heat it to ~1250℃ for about 10 minutes will cause it to melt and foam evenly. When this is gradually cooled, a foam having a desired shape is obtained. Note that the shape may be corrected by heating and foaming and press-molding into a desired shape while the foam is still hot and softened at around 900°C. In this case, the final product is formed by pressure molding, correction, and then slow cooling. Moreover, after obtaining the foam, cutting or machining may be performed as necessary.

〔Effect of the invention〕

In the present invention, since volcanic ejecta and CaO compounds such as limestone, which are produced all over Japan, are used, there is no difficulty in obtaining raw materials.
Because CaO compounds are added, a product with strong mechanical strength can be obtained. Further, since the raw material is foamed after being molded into a predetermined shape, a ceramic foam having a desired shape without distortion can be obtained. Moreover, products produced from the same region have almost the same composition, so there is little variation in product quality, and good ceramic foams can be obtained. Furthermore, the foaming temperature is low, resulting in low energy costs during production.

The ceramic foam of the present invention can be suitably used as a heat insulating material, a fireproof material, a building material such as an outer wall of a building, a roofing material, and various other uses. Incidentally, the heat resistance of a heat insulating material made of glass fiber is around 400°C, whereas the ceramic foam of the present invention has a heat resistance of around 900°C.

〔Example〕

Next, examples of the present invention will be shown.

Example 1 Finely powdered whitebait (produced in Tarumi City, Kagoshima Prefecture,
Containing 71% SiO ₂ and 14% Al ₂ O ₃ ) 75.5 parts by weight, 24.5 parts by weight calcium carbonate, 0.3 parts by weight silicon carbide,
After adding 25 parts by weight of water and mixing and kneading, it was formed into pellets using an extruder, which was further formed into a disk shape, and heated to 1200°C for 10 minutes in an electric furnace to foam. A circular plate-shaped ceramic foam was obtained by slow cooling. The resulting ceramic foam has a specific gravity of 0.33.
The bending strength was 30Kg/cm ² .

Example 2 Finely powdered anti-flame stone (produced in Niijima, Tokyo, SiO ₂
78.7%, Al ₂ O ₃ (12.3%)) 73.2 parts by weight, limestone 26.5 parts by weight, silicon carbide 0.3 parts by weight, water glass 5
Parts by weight were mixed, formed into a plate shape using a press, heated to 1250°C for 10 minutes in an electric furnace to foam, and then slowly cooled to obtain a plate-shaped ceramic foam. The ceramic foam obtained had a specific gravity of 0.40 and a bending strength of 40 kg/cm ² .

Claims (1)

[Claims] 1 Volcanic ejecta 60-90 parts by weight, CaO compound 40-10
Silicon carbide is added to the weight part, mixed and molded into a predetermined shape, and the molded product is heated to 900 to 1250
A method for producing a ceramic foam, which is characterized by foaming by heating to ℃.