JPH0148225B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a porous refractory made of ceramic fiber having a heat resistance of at least 1000° C. and used for high-temperature refractory heat insulating materials, high-temperature fluid filters, catalyst carriers, etc., and a method for producing the same. [Prior art] Ceramic fiber molded products are used as high-temperature fireproof insulation materials used in molten metal runners, tundishes, burner tiles, electric furnace linings, filters for high-temperature fluids, catalyst carriers for high-temperature reactions, etc.
Generally, SiO ₂ fibers, Al ₂ O ₃ fibers, and Al ₂ O ₃ -SiO ₂ fibers are dispersed in water containing silica sol or alumina sol, vacuum formed, and a dried molded product is produced.
It is obtained by firing at 1250-1300°C for 1-1.5 hours.
However, the bending strength of these products (JIS9503−1969,
5.7 Depends on bending strength. (same below) is 2-4Kg/cm ²
However, it is still not enough. If phosphoric acid, water glass, or the like other than silica sol or alumina sol is used as a binder, it is undesirable because it deteriorates the fibers and conversely reduces bending strength and heat resistance. [Problems to be Solved by the Invention] The present invention provides a porous refractory made of a molded product with greater bending strength than before, and the refractory can be produced at low cost, without reducing the heat resistance of the ceramic fibers described above. The purpose of this paper is to provide a manufacturing method for obtaining the same. [Means for solving the problems] In order to achieve the above object, the present invention uses SiO ₂ fibers,
A porous structure in which the intersections of the fibers of a fiber aggregate consisting of one or more of Al ₂ O ₃ fibers and Al ₂ O ₃ -SiO ₂ fibers are fused with a composition mainly consisting of SiO ₂ and B ₂ O ₃ . and that these fibers constituted a refractory.
Dispersed in water containing SiO ₂ sol, vacuum formed,
After drying and firing, the material is immersed in an aqueous solution containing dissolved B ₂ O ₃ and then dried and fired to obtain a porous refractory. [Function] In the present invention, the above-mentioned fibers having heat resistance of 1000° C. or more are made into a length of, for example, about 30 to 1 mm, most of them 5 to 7 mm, in an amount of about 10 parts by weight or less per 100 parts by weight of water. Disperse 1 to 2 parts by weight of silica sol in water, vacuum form it, and dry the molded product.
Bake at 1300℃ for 1 to 1.5 hours. The water contained between the fibers evaporates during drying, the silica sol dispersed in the water is concentrated, and after firing, the fibers become 100%
9 to 10 parts by weight should be fused to each part by weight. Next, the fired molded product was immersed in boric acid solution containing about 1 part of B ₂ O ₃ per 100 parts by weight of water, taken out and dried, and heated at 1250 to 1300°C for 1 to 30 minutes.
Bake for 1.5 hours. B ₂ O ₃ is preferably bound in an amount of 2 to 10 parts by weight, preferably 3 to 5 parts by weight, per 100 parts by weight of fibers after firing. Boric acid turns into B ₂ O ₃ at 300℃. The melting point _{of B2O3} is 577℃ and the boiling point
Although the temperature is above 1,500℃, it begins to partially sublimate at around 900℃ and mainly collects in the gaps between the intersections of the fibers, reacts with SiO ₂ produced by the silica sol, becomes a type of borate glass, and fuses the intersections of the fibers. At this time, some of the components in the fibers may also be dissolved therein, but no reaction occurs that changes the composition of the fibers or lowers their heat resistance. [Example] Bending strength (Kg/cm ² ) of the present invention example and other examples,
The bulk density (in parentheses) is shown in the table below.

〔Effect of the invention〕

Figure 2 is an electron micrograph of a porous refractory made by molding and firing Al ₂ O ₃ -SiO ₂ fibers using only silica sol as a binder, but the SiO ₂ particles are granular and only partially fused to the fiber surface. There are very few areas where fiber intersections are connected. In contrast, the porous refractory of the present invention completely fuses the intersections of Al ₂ O ₃ -SiO ₂ fibers, as shown in the electron micrograph in Figure 1, and retains its original state without changing the composition of the fibers. It is clear that it is maintained. In the above table, Al ₂ O ₃ − containing B ₂ O ₃ as a component
In the molded body using B ₂ O ₃ −SiO ₂ fibers, the bending strength increases as the SiO ₂ content in the total composition of the molded body increases, even if only SiO ₂ sol is used as a binder. This is because the fiber components reacted during firing to form a low melting point composition, producing a large amount of melt, and the fiber itself also melted and shrunk. When this happens, the heat resistance of the fibers decreases. Furthermore, when conventional SiO ₂ sol or Al ₂ O ₃ sol is used as the only binder, the intersections of the fibers are not sufficiently bonded, so the bending strength does not improve, and when using phosphoric acid or water glass as the binder, , the composition changed due to firing, and the fibers deteriorated. As described above, according to the porous refractory of the present invention, it is possible to provide a porous refractory with high bending strength without changing the composition of the fiber itself and without reducing the heat resistance of the fiber. high temperature insulation material,
For high temperature filters, catalyst carriers, etc., SiO ₂ fibers,
The applications of Al ₂ O ₃ fiber and Al ₂ O ₃ -SiO ₂ fiber molded products can be expanded. In addition, in the production method of the present invention, the amount of SiO _{2 and} B ₂ O ₃ added as binders can be easily adjusted in consideration of the fire resistance and bending strength of the fiber composition and application.
Porous refractories with high strength can be provided at low cost using sol and B ₂ O ₃ powder.

[Brief explanation of drawings]

Figure 1 is an electron micrograph of a porous refractory according to the present invention using Al ₂ O ₃ -SiO ₂ fibers, and Figure 2 is
FIG. 2 is an electron micrograph of a porous refractory obtained by molding and firing Al ₂ O ₃ —SiO ₂ fibers using SiO ₂ sol as a binder.

Claims (1)

[Claims] 1. The intersection of fibers in a fiber assembly consisting of one or more of SiO ₂ fibers, Al ₂ O ₃ fibers, and Al ₂ O ₃ -SiO ₂ fibers is mainly composed of SiO ₂ and B ₂ O ₃ A porous refractory characterized by being fused with a composition. 2. After dispersing one or more of SiO ₂ fibers, Al ₂ O ₃ fibers, and Al ₂ O ₃ -SiO ₂ fibers in water containing SiO ₂ sol, vacuum forming, and drying and firing,
A method for producing a porous refractory, which comprises immersing it in an aqueous solution containing dissolved B ₂ O ₃ and drying and firing it.