JPH0688845B2 - Method for producing ceramic foam - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a ceramic foam that is suitable for application to an outer wall panel of a house and the like.

(Prior Art) It is well known that ceramic foam is an ideal material as a building material because it is lightweight and has excellent heat insulation and durability.

Therefore, although many inventions have been made in the past in an attempt to put this ceramic foam into practical use, there has been no good method for industrially inexpensively manufacturing it.

That is, in order to inexpensively manufacture a ceramic foam industrially, it is best to heat foam and mold it on a plate or a wire mesh made of a heat resistant metal such as stainless steel or in a heat resistant metal mold. Yes, for that reason, 850
It is necessary to foam by heating to 1000 ℃.

It was also found that the air bubbles inside the ceramic foam should be small and should be dispersed almost uniformly.

The inventors have tried the conventionally known manufacturing method, but could not obtain a ceramic foam satisfying the above object.

For example, in the methods proposed in JP-A-52-22010 and JP-A-54-65716, foaming does not occur unless heated to 1100 to 1300 ° C.

Further, when a large amount of water glass is added as in the method disclosed in JP-A-53-35730, the heating and foaming temperature decreases to around 1000 ° C., but the bubbles near the surface become coarse and the bubbles inside are fine. Things have been obtained.

(Problems to be Solved by the Invention) In the former method, since the heating and foaming temperature is high, it is difficult to use a metal belt or a metal mold in the heating furnace, and the furnace needs to have high performance. Therefore, the heating and cooling time becomes longer.

In the latter method, air bubbles are not uniformly dispersed, the mechanical strength of the whole becomes insufficient, and the shape retention near the surface is poor. Considering processing and construction, a separate member such as a sandwich panel is used. Reinforcement must be done.

As a result of various studies, the inventors of the present invention have found that it is almost impossible to foam at 1200 ° C. or lower with only volcanic products such as anti-firestone, shirasu, andesite, rhyolite, etc.
%, The heating and foaming temperature will drop to around 1000 ° C, but water glass will ooze out near the surface and the bubbles near the surface will grow, resulting in a foam in which small bubbles are almost evenly dispersed. I found that I could not get it.

Furthermore, instead of liquid water glass, we tried to produce a ceramic foam by mixing solid sodium silicate and soda ash that did not exude, but to make it foam at 1000 ° C or below, 30% of sodium silicate or soda ash was used. As described above, the air bubbles become coarse, the heat shrinkage of the melt becomes large, and it easily breaks during cooling after foaming, making it difficult to obtain a good product.

(Means for Solving the Problem) The present invention is intended to solve the above-mentioned problems by the configurations described in the claims. That is, by using soda ash and limestone or slaked lime,
The inventors have found that even if the soda ash is 30% or less, it can be heated and foamed at 1000 ° C. or less, and that it is difficult to crack even after cooling after foaming, and that a good product can be obtained, and the present invention has been completed.

Volcanic products such as anti-firestone, shirasu, andesite, rhyolite used in the present invention are the main components of ceramic foam. These volcanic products are preferably used as a powder, preferably as a fine powder passing through 200 mesh.

The soda ash and limestone or slaked lime used in the present invention work together to lower the melting and softening temperature of the volcanic ejecta which is the main component. For the first time, add 10 to 30 parts of soda ash and 5 to 20 parts of limestone or slaked lime to 60 to 80 parts of volcanic ejecta of the main component (the same applies hereafter by weight).
Melts and softens and foams at temperatures of up to 1000 ° C.

That is, when the soda ash is added in excess of 30 parts, the cells become coarse, cracks occur during cooling after foaming, a good ceramic foam cannot be obtained, and if the content is less than 10 parts, the melt softening temperature is 1000
It is difficult to keep the temperature below ℃.

Also, with only 10 to 30 parts of soda ash, the melt softening temperature is 1000
Although the temperature does not drop below ℃, the foaming temperature is 1000 ℃ only after adding 2 to 20 parts of limestone or slaked lime.
It becomes the following. If the amount of limestone or slaked lime is less than 2 parts, the effect of lowering the melting and softening temperature is small, and if it exceeds 20 parts, the melting and softening temperature rises.

All of these soda ash, limestone, and slaked lime in the present invention are used in a powder state. It is preferable to use a fine powder that passes through 200 mesh.

In the present invention, clay is not necessarily mixed, but
By mixing up to some parts of the clay, the melt viscosity of the composition is increased, and a good foam having small cells can be obtained. Mixing more than 15 parts of clay raises the melt softening temperature. Such clays include bentonite, clay, fly ash, kaolin, frog eye clay and the like.

Silicon carbide used in the present invention is a foaming agent, and is added in an amount of 0.1 to 1 part, preferably 0.15 to 0.5 part, relative to 60 to 80 parts of the main component volcanic rock. If the amount of the foaming agent is small, the expansion ratio becomes small, and if it is less than 0.1 part, almost no foaming occurs.
Conversely, when the amount of the foaming agent increases, the expansion ratio increases, but the specific gravity can be reduced to about 0.3 in the vicinity of 1 part. However, adding more than 1 part of the foaming agent has no further foaming effect and only raises the raw material cost.

Clays and foaming agents are also preferably used in powder form, preferably a fine powder passing through 200 mesh.

(Operation) In the present invention, the above-mentioned volcanic ejecta, soda ash, limestone or slaked lime, clay, and silicon carbide are powdered and uniformly mixed.

The mixture may be heat-foamed as a powder, but the mixture may be granulated with a granulator, or may be press-molded and then heat-foamed.

During heating and foaming, a wire or a wire net made of a heat resistant metal such as stainless steel can be embedded in the mixture for reinforcement, or a jig can be embedded.

When the powder, granules or molded body of this mixture is heated and foamed in the furnace, the powder, granules or molded body of the mixture is placed on the endless belt made of stainless steel or the like passing through the furnace, and the mixture is heated in the furnace. It is continuously produced by heat-foaming it while passing through it, compressing it into a suitable shape while still soft enough to deform, and then slowly cooling it before it comes out of the furnace. can do. For such an endless belt, a dense balance type belt with a small gap between the wires is suitable so that powder or melt does not drop. In order to prevent the melt from adhering to the belt, it is advisable to coat the belt with alumina powder or alumina hydroxide powder.

Put the powder, granules or compact of the mixture into a mold coated with alumina powder, heat foam while passing through the tunnel furnace, press in a still deformable soft state, and then cool slowly. You can also

In the heating furnace, the mixture begins to melt and soften under the heat of 850 to 1000 ° C., and the presence of molten silicic acid causes the silicon carbide to decompose and foam. When soda ash and limestone or slaked lime are used in combination, the melting and softening temperature becomes 850 to 1000 ° C, and a uniform foam having fine cells can be obtained. In addition, the presence of clay increases the melt viscosity of the melt, resulting in a good foam having uniform cell diameters.

(Effects of the Invention) As described above, in the present invention, since foaming can be performed by heating at 850 to 1000 ° C., heat-foaming on a belt made of metal or press-molding with a metal mold while soft after foaming. It becomes possible to roll-form. Therefore, a high-performance heating furnace is not required, the heating / cooling time can be shortened, the manufacturing efficiency can be improved, and the manufacturing cost can be reduced.

Also, the amount of soda ash used is 30 to 60 to 80 parts of volcanic rock.
It is possible to obtain a good ceramic foam without causing the cells to become coarse and cracking during cooling.

The product obtained in this way is a roof material if it is plate-shaped,
It can be used as a building board such as outer wall materials and floor materials. Further, the press-molded product using a mold has improved mechanical strength and can be used for roof tiles, tiles, ceiling materials, fence materials and the like.

(Example 1) Anti-fire stone was crushed using a ball mill, and 70 kg of anti-fire stone fine powder passing through 300 mesh, soda ash powder 15 kg, slaked lime powder 10 kg, bentonite powder 5 kg, and silicon carbide powder 250 g
And were placed in a cross rotary type powder mixer and mixed uniformly.

Alumina powder dispersed in water is applied on a stainless steel plate (length 2 m, width 1 m 20 cm) and dried to form an alumina powder film, on which the above mixture is uniformly applied to a thickness of about 5 cm. I put it on.

When this was placed in a furnace and heated to 950 ° C. for 1 hour, the mixture began to melt and foam.

When kept at 950 ° C for 5 minutes and cooled to 200 ° C in about 3 hours, it evenly foams with a thickness of about 55 mm.
A ceramic foam of 0.7 was obtained.

When this was cut, and the cut end was observed, it was a ceramic foam with a maximum of 1.5 mm and a substantially uniformly dispersed cell.

(Example 2) 65 kg of Shirasu fine powder passing through 250 mesh and soda ash powder 2
A mixture of 0 kg, 10 kg of limestone powder, 5 kg of fly ash, and 300 g of silicon carbide powder was mixed in the same manner as above, and the thickness was formed on a dense balanced endless belt made of stainless steel wire coated with aluminum hydroxide. Place it so that it is 2 cm.

When this belt was passed through a furnace with a maximum temperature of 900 ° C, the mixture began to foam near the maximum temperature,
Then, while the foamed melt mixture was still soft, it was formed into a plate by a roll. Then, it was gradually cooled. The total time for the mixture to pass through the furnace was about 2 hours.

The obtained product was a pale green one having a specific gravity of about 0.6 and was a uniformly dispersed ceramic foam having a diameter of about 1 mm when the cross section of the cut surface was observed.

(Example 3) 650 g kg of andesite fine powder passing through 300 mesh, 150 g of soda ash powder, 50 g of slaked lime powder, 50 g of kaolin powder, 4 g of silicon carbide powder, and 50 g of water were uniformly mixed, and then pressed with a tile. It was molded into a shape.

After drying it sufficiently, it was placed in a stainless steel mold whose inner surface was slightly larger than this tile-shaped molded body and was coated with alumina powder, and this was heated in a heating furnace at 870 ° C for 10 minutes. Melted and foamed.

This was immediately pressed with a tile-shaped plate to be molded, and then gradually cooled.

When the ceramic foam was taken out of the mold, a black roof tile shaped body having a specific gravity of 0.45 was obtained. When the cut body was cut and the cut end was observed, it was a ceramic foam having uniformly dispersed cells with a maximum diameter of 1.5 mm.

Claims (1)

[Claims] 1. From 60 to 80 parts by weight of at least one selected from the group of volcanic products such as anti-firestones, shirasu, andesite, rhyolite, 10 to 30 parts by weight of soda ash, and from the group of limestone and slaked lime One or more selected from 2 to 20 parts by weight, 0 to 15 parts by weight of clay, and 0.1 to 1 parts by weight of silicon carbide are uniformly mixed, and 850
A method for producing a ceramic foam, which comprises heating to 1000 ° C to cause foaming.