JPH0153237B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a fire-resistant coating that is applied to the surface of a base material such as a refractory used for a furnace, a flue, or a construction board to increase fire resistance. It is related to materials.

(Prior art) The surface of refractories used in parts exposed to high-temperature atmospheres, such as kilns, is made of refractory materials whose main ingredients are granular materials such as mullite and alumina, with the addition of adhesives such as clay or water glass. In the past, conventional coating materials were applied to prevent fusion between the refractory surface and the product to be fired inside, as well as to prevent damage to the refractory surface. When coated on the surface, the water glass contained as an adhesive becomes vitrified and cracks and peels due to the difference in thermal expansion with the refractory, so the protective function of the refractory is not sufficient, and the refractory is damaged due to high temperature atmosphere. In addition to being unable to sufficiently prevent oxidation, the thermal shock buffering effect is small due to insufficient heat insulation, and it cannot fully contribute to extending the life of refractories. The disadvantage of using cladding materials is that they require more frequent maintenance and repair, resulting in higher installation costs.

(Object of the invention) The object of the present invention is to provide a fire-resistant coating material that eliminates the above-mentioned drawbacks, has no risk of peeling, has good oxidation resistance and thermal shock resistance, and can effectively protect the surface of refractories. It was completed as.

(Structure of the Invention) The main components of the present invention are 35 to 50% by weight of ceramic short fibers adjusted to a mesh size of 60 to 300 and 50 to 65% by weight of silica sol containing 5 to 70% by weight of silica with a particle size of 5 to 30 μm. This is characterized by the addition of an appropriate amount of an organic binder.

The ceramic fibers used in the present invention are selected with consideration to the operating temperature. For example, if the operating temperature is 800 to 1600°C, alumina fibers whose main component is alumina that can withstand this temperature are selected. It is preferable to do so. After crushing, the ceramic fibers are deironated and sieved into approximately 60 to 300 mesh pieces to produce short fibers. Here, the dimensions of the ceramic short fibers are 60
If it is below mesh, the impact resistance will decrease;
If the number exceeds 300 meshes, the adhesive strength will decrease, making it unsuitable for achieving the object of the present invention. On the other hand, as an inorganic binder, silica is
A silica sol containing 70% by weight, preferably 15-50% by weight is used. The reason for this is that if the silica content is less than 5% by weight, its ability as a binder will decrease and it will easily peel off, whereas if it exceeds 70% by weight, silica will melt onto the surface of the fire-resistant coating layer and cause problems with fired products, etc. This is because the effect of preventing fusion will be reduced, and the particle size of the silica should be adjusted to 5 to 5 to increase homogeneity and prevent the adhesive force from becoming small due to a decrease in the bonding force between particles.
The thickness is preferably about 30 μm. These ceramic short fibers and silica sol are mixed in a ratio of 50 to 65 weight percent of silica sol to 35 to 50 weight percent of ceramic short fibers, and are combined with an organic temporary caking agent such as powdered carboxymethylcellulose, polyvinyl alcohol, or glycerin. For example,
Add an appropriate amount of about 0.2 to 1.0% by weight to make a fire-resistant coating material. The reason why the mixing ratio of ceramic short fibers and silica sol is limited as described above is that the content of silica sol is 50 to 65% by weight as shown in Figure 1.
2.5~ suitable for application to refractory surfaces when
This is because a viscosity of 30 poise can be obtained.
The fire-resistant coating material obtained in this way is sprayed onto the surface of the base material such as refractory material or heat-resistant metal.
By an appropriate method such as brush painting or datuping
A protective layer is formed by coating to a thickness of about 0.1 to 2 mm. However, if the lining refractory used for the walls inside the kiln is used as the base material, the surface may be coated to a thickness of 2 mm or more, with emphasis on the effect of increasing heat insulation. The refractory coating material obtained in this way firmly adheres to the surface of the base material, such as a refractory-based material, and forms siloxane bonds to form a strong connective tissue. After firing, it reacts with the main refractory, fuses to the surface, and partially penetrates into the structure of the refractory, forming an impermeable protective layer. As shown in Fig. 2, the base material 1 is mainly made of silicon carbide refractory material, and on its surface, alumina fibers are used as short ceramic fibers, and a fire-resistant coating material using a silica binder is used for protection. layer 2
When deposited, an alumina-rich layer 2a is formed on the surface side of the protective layer 2, and a silica-rich layer 2b is formed below it, and these two layers trap oxygen and other substances that cause deterioration of refractories. Since the infiltration of combustion gas is prevented, particularly excellent anti-oxidation effects can be obtained.

(Example) Alumina short fibers crushed to 70 mesh and 150 mesh
Fire resistance with a viscosity of 10 poise, made by adding 61.8% by weight of an inorganic binder whose main component is silica sol as a binder and 0.2% by weight of carboxymethyl cellulose to 38% by weight of ceramic fibers mixed with the same weight of alumina short fibers from mesh. The coating material is applied to the surface of a plate-shaped refractory whose main component is silicon carbide at varying thicknesses of 0.1 mm within the range of 0.7 to 1 mm, and then exposed to a firing furnace at a maximum temperature of 1350°C for 12 hours. After that, it was taken out and the impact resistance value was measured, and the results shown in FIG. 3 were obtained. That is, when the thickness of the protective film was 1 mm, it was possible to obtain an impact resistance value 14 times that of a refractory without a protective film. In addition, if the thickness of the protective layer is increased, the impact resistance value will increase, but as shown in the figure, the rate of peeling will increase, so in practical terms the thickness of the protective layer should be
Approximately 0.7 to 1 mm is appropriate.

Next, a plate-shaped refractory on which the same protective layer as above was formed was heated to 300 to 900°C in a firing furnace, then immediately taken out of the furnace at room temperature and rapidly cooled, and the state of crack formation was observed. No cracks were observed on the surface of the refractory on which the protective layer was formed, and as shown in Figure 4, even after receiving thermal shock due to rapid cooling, the bending strength was higher than that of the refractory without the protective layer. 900℃
It showed an improvement of about 15% in the quenching temperature difference. Furthermore, when the refractory on which the protective layer of this example was formed was continuously used in a firing furnace with a maximum operating temperature of 1,350°C, the life was approximately twice as long as that of the refractory without a protective layer. In the above examples, a refractory whose main component is silicon carbide was used as the base material, but the refractory coating material of the present invention can also be applied to other refractories, heat-resistant metals, and the like.

(Effect of the invention) As is clear from the above description, the present invention
The main ingredients are ceramic short fibers adjusted to ~300 mesh and silica sol containing 5 to 70% by weight of silica with a particle size of 5 to 30 μm, to which an appropriate amount of organic binder is added, making it easy to peel. It is safe from damage and has good oxidation resistance, heat resistance, thermal shock resistance, etc., and can be used to prevent damage to refractories used in furnaces, flues, and other areas exposed to high temperature atmospheres. It can extend the lifespan and reduce the frequency of maintenance and repair, which has the economic benefit of reducing installation costs.As an excellent fire-resistant covering material, it will greatly contribute to the development of industry. It's large.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the viscosity of the fire-resistant coating material according to the present invention and the content of the inorganic binder contained therein, and FIG. A partial cross-sectional view, FIG. 3 is a graph showing the relationship between the thickness of the protective layer, impact resistance value, and peeling rate in a refractory coated with the fire-resistant coating material according to the present invention, and FIG. It is a graph showing the relationship between the quenching temperature difference and the normal temperature bending strength after the quenching in a refractory coated with a refractory coating material. 1: Base material, 2: Protective layer.

Claims (1)

[Claims] 1 The main components are 35 to 50% by weight of ceramic short fibers adjusted to 60 to 300 mesh and 50 to 65% by weight of silica sol containing 5 to 70% by weight of silica with a particle size of 5 to 30 μm, and an appropriate amount of organic A fire-resistant coating material characterized by the addition of a binder.