JPH0651595B2 - Method for manufacturing fireproof insulation board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for manufacturing a fireproof heat insulating board. More specifically, the present invention relates to a method for producing a refractory insulation board having good dimensional stability at high temperatures from alumina fibers.

<Prior Art> Heat-resistant inorganic oxide fibers such as ceramic fibers and alumina fibers are used as a refractory heat insulating material as it is or after being processed into molded products such as boards and blankets. Among them, alumina fibers are excellent in heat resistance, and are used as materials for furnace wall linings in high temperature regions where aluminosilicate ceramic fibers cannot be used.

In order to manufacture a board from these inorganic oxide fibers, these fibers are first put in 5 to 20 times its weight in water and stirred to uniformly disperse them. Then, an inorganic binder such as alumina sol or silica sol or an organic binder such as polyvinyl alcohol or acrylic latex is added to this, followed by dehydration molding and drying the molded product.

<Problems to be Solved by the Invention> One of the problems in the method for producing a fireproof heat insulating board as described above is that the board finally obtained often has a hard surface layer but a soft inside. Being homogenous. In addition, when the board is heated to a high temperature, it may expand in the longitudinal direction of the board but contract greatly in the thickness direction.

Therefore, there is a strong demand for a method of manufacturing a board that is uniformly hardened to the inside and has a small anisotropy of thermal expansion.

<Means for Solving the Problems> According to the present invention, a molded article obtained by mixing alumina fiber having an alumina content of 90 (wt)% or more with an inorganic binder in water and dehydration molding the mixture is obtained. In the method for producing a refractory heat-insulating board, the alumina fiber containing 60% by weight or more of α-alumina is used as the inorganic fiber, and the inorganic binder is silica gel or a material which can be converted into silica gel in water. Of the alumina fiber and the inorganic binder are mixed in water so that the ratio of alumina to the total amount of alumina and silica in the molded body is 75 to 90 (wt)%, and the inorganic binder is gelled. After that, by dehydration molding, it is possible to easily manufacture a board that is uniformly hardened to the inside and has a small anisotropy of thermal expansion at high temperature.

To describe the present invention in more detail, in the present invention, as the alumina fiber, one having an alumina content of 90 (wt)% or more and containing α-alumina of 60 (wt)% or more is used. Such an alumina fiber is known, and as a commercially available product, Suffil (trade name, composition: Al ₂ O manufactured by ICI) is used.
_{3 95%, SiO 2 5%} ) is. Generally, a spinning solution prepared by adding a water-soluble organic polymer to an aqueous solution containing various aluminum salts as a main component to prepare a solution having a predetermined viscosity is spun by a centrifugal force or an air flow to obtain raw fiber, which is then baked. And manufactured into an alumina fiber. To set the content of α-alumina to 60 (wt)% or more, calcination should be 1100.
It may be performed at a temperature of ℃ or higher. The board manufactured by the present invention is
When exposed to high temperatures in use, the alumina of the alumina fibers reacts with the inorganic binder silica to form mullite. Since the specific gravity of α-alumina is 4.0, while the specific gravity of mullite is 3.0, expansion occurs when α-alumina is converted to mullite. Therefore, α-in the alumina fiber
The higher the alumina content, the greater the effect of suppressing the shrinkage of the board at high temperature.

In the present invention, as the inorganic binder, silica gel or a binder which is converted into silica sol under stirring in water is used. That is, in the present invention, the inorganic binder needs to be silica gel at the time of dehydration molding. Therefore, when silica gel is used as the inorganic binder, a gelling agent for converting the sol into a gel is also used. Various gelling agents are known, but alumina sol is preferable from the viewpoint of not contaminating the alumina fiber. However, since the alumina in the inorganic binder acts to increase the shrinkage of the board at high temperature, the amount of alumina in the silica-alumina mixed sol should be as small as possible within the range necessary to cause gelation. Usually, the ratio of silica to alumina is in the range of 3: 1 to 50: 1 (weight ratio). The inorganic binder usually contains 5 to 30 parts by weight, preferably 10 to 20 parts by weight of silica as the inorganic binder based on 100 parts by weight of the alumina fiber in the molded product obtained by dehydration molding. To use. The inorganic binder is dispersed in the alumina fiber-inorganic binder dispersion for dehydration molding so as to be usually 1 to 10 (wt)%, preferably 2 to 4 (wt)%. During dehydration molding, a part of the inorganic binder usually remains in the water that is released from the molded body without adhering to the fiber, so the amount of the inorganic binder added to the dispersion is the amount contained in the molded body. A little more than. Incidentally, in order to increase the adhesion rate of the inorganic binder to the alumina fiber, when the dispersion is well stirred and made into a uniform slurry and then allowed to stand, a slight amount of water is released on the surface. It is preferable to adjust the charging conditions.

In the present invention, an organic binder may be used in combination with the inorganic binder in order to improve the mechanical strength of the board at room temperature. That is, when an organic binder is added to the dispersion and mixed well, and then dehydration molding and drying are performed, a board having a larger mechanical strength and easier to handle can be obtained. Examples of the organic binder include polyvinyl acetate, polyvinyl alcohol, starch and the like. The organic binder is the inorganic binder 1
It is usually used in an amount of 5 to 50 (weight) parts with respect to 00 (weight) parts.

Dehydration molding and drying of the dispersion are carried out by conventional methods.
For drying, the temperature and time are usually adjusted so as to be in an absolutely dry state. Normally 100 depending on the size of the molded product.
Drying may be performed at a temperature of not less than 0 ° C., for example, 100 to 120 ° C. for several hours to several tens of hours.

The refractory insulation board obtained by the present invention is extremely excellent in dimensional stability under high temperature conditions of 950 ° C. or higher, and under high temperature of 1500 ° C. or higher, which has been restricted in use by conventional products due to poor dimensional stability. Is also suitable for use.

<Example> Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

The alumina fibers used in the following examples and comparative examples are as follows.

Fiber A: Alumina-silica fiber having an alumina content of 95 (wt)% was fired at 1350 ° C. for 1 hour to obtain a fiber containing 82 (wt)% of α-alumina.

Fiber B: An alumina-silica fiber having an alumina content of 95 (wt)% and containing α-alumina of 40 (wt)%.

Fiber C: Alumina-silica fiber having an alumina content of 80 (wt)% was fired at 1350 ° C. for 1 hour to obtain a fiber containing 27 (wt)% of α-alumina.

Fiber D: 126 aluminosilicate ceramic fibers
Crystallized by firing at 0 ° C for 1 hour.

In addition, the following silica and alumina were used for the preparation of the inorganic binder.

Cataloid S-20L: Silica sol, manufactured by Catalysis Chemicals Co., Ltd. Cataloid SN: Silica sol, 〃 Aerosil 300: Silica gel, manufactured by Nippon Aerosil Co., Ltd. Alumina sol 200: Alumina sol, manufactured by Nissan Chemical Industries, Ltd. Aluminum oxide C: Alumina gel, manufactured by Nippon Aerosil Co., Ltd. Was mixed with silica and alumina to prepare 800 parts by weight of an aqueous solution of an inorganic binder having a predetermined concentration, and 100 parts by weight of fibers was mixed with this and well stirred to form a uniform dispersion liquid, followed by dehydration molding. And dried.

Claims (4)

[Claims] 1. A method for producing a fire-resistant insulation board, comprising mixing alumina fibers having an alumina content of 90 (wt)% or more with an inorganic binder in water, dehydrating the mixture, and drying the molded body. Alumina fibers containing 60% by weight or more of α-alumina were used, and silica gel or an inorganic binder capable of being converted into silica gel in water was used to obtain these alumina fibers and inorganic binder. The ratio of alumina to the total amount of alumina and silica in the formed molded body is 75 to 90 (weight)
% In water so that the inorganic binder is gelled, and then dehydration molding is performed. 2. The inorganic binder contains silica sol and alumina, and the ratio of silica to alumina is 3: 1 to 5.
The method according to claim 1, wherein the ratio is 0: 1 (weight ratio). 3. The method according to claim 1 or 2, wherein an organic binder is used together when the alumina fiber and the inorganic binder are mixed in water. 4. A molded article obtained by dehydration molding contains 5 to 30 parts by weight of an inorganic binder as silica per 100 parts by weight of alumina fiber. The method according to any one of claims 1 to 3.