JPS61266331A - Low-density, high-strength, heat-resistant molded product and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a molded article having high heat resistance, low density and high strength;
and its manufacturing method.

Conventional technology Conventionally, heat-resistant, low-density molded bodies that have been put into practical use include inorganic fibers such as rock wool, glass wool, and ceramic fibers combined with an organic binder or colloidal silica.
Inorganic foam materials such as 7 ohm glass, asbestos foam materials, perlite, vermiculite,
There are molded bodies made mainly of foam such as shirasu, calcium silicate molded bodies, and insulating bricks.

However, these materials have the drawback that, for example, those made by bonding inorganic fibers with an organic binder do not have any strength at high temperatures. On the other hand, in the case of inorganic binders, low-density products are difficult to obtain strength at room and high temperatures, and some, such as alkali silicate, impair heat resistance, while others, such as alumina cement and Portland cement, do not maintain strength at high temperatures. Materials that cause a significant decrease in strength, such as colloidal silica, alumina sol, and phosphoric acid aluminum, have drawbacks such as migration during drying after molding, making it difficult to obtain uniform strength.

Please note that new materials such as 7-ohm glass and inorganic foam materials such as asbestos foam materials have low heat resistance, with the operating temperature being around 500℃ at most. There are no other materials, such as calcium acid molded bodies or insulating bricks, that have both low density and high strength.

OBJECT OF THE INVENTION The object of the present invention is to provide a molded article having high heat resistance, low density and high strength, without the above-mentioned drawbacks, in particular, having a heat resistance temperature of 1000°C or more and a density of 121/cm or less, Bending strength is jo
It is an object of the present invention to provide a fiber molded article having a yield exceeding kp/m.

That is, according to the present invention, a siliceous material, an inorganic fiber, and boron oxide are uniformly mixed, molded, and then heat-treated to form a molten borosilicate glass layer on the surface of the siliceous material, thereby forming an inorganic fiber. A low-density, high-strength molded body obtained by fusion bonding between the two is provided.

Preferred Embodiment of the Invention The siliceous material, which is one of the starting materials in the present invention, has a surface occupied by sio of 90 fi or more. As these substances, powdered materials such as silica powder, silica sand, and silica flour, as well as silica fibers can be used.

In particular, in the case of silica fibers, the mixing ratio range can be widened and there are many fused portions between the fibers, so it is possible to obtain a molded article with high strength.

Further, as the inorganic fiber, natural inorganic fibrous substances such as ceramic fiber, crystalline alumina fiber, rock wool or asbestos, and wollastonite can be used.

Now, to describe the combination of silica fibers and alumina fibers, which is a very preferred embodiment of the present invention, silica fibers with an average fiber diameter of 4 to 20μ and alumina fibers with an average fiber diameter of 5 to 20μ are mixed with a predetermined amount of boron oxide. It is mixed with a binder (dry or wet), shaped and then fired at a predetermined temperature. In this way, a more suitable heat insulating structure can be obtained. In addition, if it is thicker than the above average diameter,
Since the number of points of intersection with the alumina fibers is extremely small and the portion fused by boron oxide is small, it is difficult to obtain sufficient strength, and there are drawbacks such as high thermal conductivity. In this case, silica fibers and aluminum fibers are fused into a net-like three-dimensional structure. That is, the silica fibers and alumina fibers are fused at their intersections by an adhesive member (borosilicate glass layer) made of boron oxide.

It is important that the silica fibers used here have an average fiber diameter within the above range; if the silica fibers are thinner than this, the reactor water resistance during molding will be extremely poor, productivity will be poor, and the surface area will be small. This reaction progresses and causes internal defects during sintering.

As mentioned above, when mixing the siliceous material, inorganic fiber, and boron oxide, both dry mixing and wet mixing can be employed, but in the case of the dry method, boron oxide may be mixed in powder form. Alternatively, it may be sprayed in the form of an aqueous solution.

In the case of the wet method, the siliceous material and inorganic fibers are generally added to an aqueous boron oxide solution, stirred and mixed, and then dehydrated and molded. This is a preferred embodiment because it is easy to obtain a material with particularly high strength since the siliceous material and boron oxide are in uniform contact with each other.

After mixing, K undergoes a heat treatment (
(firing process) is required.

The heating conditions are preferably 800 to 1400°C for 1 to 15 hours.

At temperatures lower than 800° C., the reaction between the silica material and boron oxide is insufficient and a strong borosilicate alkali glass layer cannot be formed.

Just in case, if the temperature is higher than 1400°C, the reaction between the silica material and boron oxide will proceed too much and cause internal defects, which will actually deteriorate the strength.

Boron oxide acts as a binder, and it attaches to the intersection of the siliceous material and the inorganic fibers and binds them together during the firing process to form a three-dimensional network structure. It is. Further, boron oxide has the effect of preventing silica fibers from crystallizing when exposed to temperatures around 1000°C. Therefore, the blending amount is preferably set within the range of 1 to 15 parts by weight so as to sufficiently exhibit the fusing effect and the crystallization inhibiting effect. Incidentally, the blending amounts of the siliceous substance and inorganic fiber are preferably 10 to 90 parts by weight and 10 to 85 parts by weight, respectively.

In the present invention, it is also possible to blend in advance a predetermined amount of inorganic fine powder such as silicon carbide, silicon carbide whiskers, and silicon chloride for the purpose of reducing radiant heat transfer.

EXAMPLES Hereinafter, the present invention will be explained with reference to Examples, but the present invention is not limited thereto.

Tables 1 and 2 show the results of the following examples and comparative examples.

Example (1) 30 parts of silica sand fine powder (average particle diameter 2μ) and 66 parts of crystalline alumina fiber (average fiber diameter 44μ) were mixed in a dry method, and then a total of 10 parts of a boric acid aqueous solution (containing 8mOs4μ) was mixed.
Add 0 parts of spray, mix further, press mold to form a board with a thickness of 50 mm, and after drying naturally at room temperature,
It was heated and baked at 1250°C for 5 hours.

Example (2) B store Os! Add 60 parts of silica fiber (average fiber diameter 9μ) and 34 parts of ceramic fiber to 500 parts of 8 degree boric acid water droplet, stir and mix, then dehydrate and mold to a water content of 200% to 600x60oxao■
This board was dried at a low temperature of 0° C. or lower or in a high frequency dryer, and then heated and baked at 1100° C. for 5 hours.

Comparative Example (1) After dry mixing 10 parts of phenol resin powder and 90 parts of crystalline alumina fiber, 150
C. for 20 minutes to obtain a board with a thickness of 30 mm.

Comparative Example (2) After adding 100 parts of ceramic fiber to 3,000 parts of a 10% colloidal silica aqueous solution and stirring and mixing, a molded body was obtained in the same process as in Example (2).

Table 2 (Performance of general heat insulating materials) Effects of the invention As stated above, 1) According to this invention, low density 1)
However, it is possible to obtain a heat-resistant molded product having high strength, uniform strength without unevenness throughout the interior, and a low heat shrinkage rate.

In particular, according to the present invention, since the surface of the siliceous material has a structure covered with a borosilicate glass layer, the crystallization of the siliceous material is suppressed, so that a molded article with good heat resistance is obtained. .

Claims (6)

[Claims] (1) A siliceous material, an inorganic fiber, and boron oxide are mixed and molded, and then heated to form a fused borosilicate glass layer on the surface of the siliceous material, and the inorganic fibers are fused and bonded. A low-density, high-strength molded body. (2) The molded article according to claim 1, wherein the blending amounts of the siliceous substance, inorganic fiber, and boron oxide are 10 to 90 parts by weight, 10 to 85 parts by weight, and 1 to 15 parts by weight, respectively. (3) The molded article according to claim 1 or 2, wherein the surface of the siliceous material is occupied by 90% or more of SiO_2. (4) The molded article according to any one of claims 1 to 3, wherein the siliceous substance is a silica fiber having an average fiber diameter of 4 to 20 μm. (5) The molded article according to any one of claims 1 to 4, wherein the inorganic fiber is an alumina fiber. (6) The silica material, inorganic fibers and boron oxide are mixed and molded and then heat treated to form a fused borosilicate glass layer on the surface of the siliceous material, thereby creating a fusion bond between the inorganic fibers. A method for producing a low-density, high-strength molded body.