JPH0212897B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a zirconia fiber molded body, and more particularly to a refractory zirconia fiber molded body used, for example, as a heat insulating material for a high temperature furnace, a catalyst carrier, a setter, and the like. (Conventional technology) Conventionally, fire-resistant zirconia fiber molded bodies were
It consists of zirconia fibers and a binder of colloidal silica aqueous solution.
When this colloidal silica is used, a migration phenomenon occurs in which the colloidal silica component becomes unevenly distributed in the surface layer from the half-dried molded product during drying, and after drying, only the surface layer hardens while the inside remains soft. There's a problem. To prevent this migration phenomenon,
Various proposals have been made. For example, a coagulant is added to a slurry liquid made by dispersing inorganic fibers and colloidal silica in a dispersion medium, and the pH of the slurry liquid is immediately adjusted to 4.5 or less to produce a colloidal silica coagulant, and then to this slurry liquid, A fiber molded article has been proposed in which a polymer flocculant is added to fix the colloidal silica coagulate on an inorganic fiber, and a molded article made from the slurry liquid is fired (Japanese Patent Application Laid-open No. 33244/1983). . In addition, a coagulant is added to a slurry in which inorganic fibers and colloidal silica are dispersed in a dispersion medium, and then polyethylene oxide is added to fix the colloidal silica to the fibers, and from the resulting slurry composition, A fiber molded body made by firing a molded body has also been proposed (Japanese Patent Application Laid-Open No. 104059/1983). These conventional techniques can prevent migration of colloidal silica. (Problems to be Solved by the Invention) However, in the prior art, since colloidal silica is used as a binder, when applied to a zirconia fiber molded article, the melting point of zirconia is 2600°C, whereas the melting point of silica is 2600°C. but
Since the temperature is significantly lower than 1650°C, there is a problem that a highly fire-resistant zirconia fiber molded article cannot be obtained. This invention was made against the background of the above-mentioned circumstances, and its purpose is to provide a zirconia fiber molded article that is free from the binder migration phenomenon and has high fire resistance. (Means for Solving the Problems) As a result of various studies on zirconia fiber molded bodies, the present inventors have determined that zirconia monoclinic sol can be used instead of silica sol, which was conventionally considered to be desirable as a binder. The present inventors have found that the use of a so-called crystal stabilizer, which stabilizes crystals to tetragonal crystals, as a binder is effective in achieving the object of the present invention, and has completed the present invention. That is, the zirconia fiber molded article of the present invention comprises a zirconia fiber and a binder that is a crystal stabilizer for zirconia or a precursor that converts into the crystal stabilizer by heating, such as magnesium, yttrium, calcium, samarium, and cadmium. , lanthanum, and at least one crystal stabilizer selected from neodymium oxides, carbonates, basic carbonates, acetates, oxalates, nitrates, chlorides, and sulfates, or a precursor thereof. It is characterized by consisting of a binder. In a preferred embodiment of this invention, the binder is 0.1μ
It can have a viscosity of 0.3 mm to 0.3 mm. In another preferred embodiment of the present invention, the amount of the binder added can be 1 to 20 parts by weight in terms of oxide based on 100 parts by weight of zirconia fiber. As one aspect of the present invention, the zirconia fiber molded body can be formed by paper-making, and in this case, it is desirable that the medium used for paper-making is one that does not substantially dissolve the binder. Furthermore, as another embodiment, the zirconia fiber used in the present invention can be at least one type of fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and ittria-stabilized zirconia fiber. . This invention will be explained in more detail below. The binder used in this invention is a crystal stabilizer for zirconia or a precursor that converts into the crystal stabilizer upon heating. That is,
The binder is a metal oxide that exhibits a crystal stabilizing effect on zirconia and/or a metal salt that forms a metal oxide upon heating. Examples of such binders include oxides, carbonates, basic carbonates, acetates, oxalates, nitrates, chlorides, and sulfates of magnesium, yttrium, calcium, samarium, cadmium, lanthanum, neodymium, etc. From an economic point of view, powders of oxides, chlorides, carbonates, and basic carbonates of magnesium, calcium, and yttrium are preferred. The particle size of the metal oxide and metal salt binders is
It is 0.01 μm to 1 mm, preferably 0.1 μm to 0.3 mm.
If it is less than this minimum limit, a migration phenomenon may occur during drying, and if it exceeds the maximum limit, its function as a binder will decrease and the strength will deteriorate. The amount of binder added is zirconia fiber 100
The amount is 0.5 to 30 parts by weight, preferably 1 to 20 parts by weight in terms of oxide. This is because if the strength is less than the minimum limit, the strength of the zirconia fiber molded object will not be expressed, and on the other hand, if it exceeds the maximum limit, the zirconia fiber molding will not wet metal or glass, will be chemically stable, and has excellent corrosion resistance. This is because the characteristics of the body are impaired. The zirconia fibers used in this invention include zirconia fibers to which a crystal stabilizer is added, such as lime-stabilized zirconia fibers, yttria-stabilized zirconia fibers, and magnesia-added zirconia fibers. There are some that are not pure zirconia fibers. Types of zirconia fibers,
The shape and dimensions can be changed as appropriate depending on the purpose and use. In addition to the zirconia fiber and the binder, the zirconia fiber molded article according to the present invention includes:
Various additives can be included as necessary. For example, conventional refractory powders such as alumina, zirconia, and silica can be added to form a composite material, and various auxiliary materials can be added to impart various performances to the final molded product. Molding into the zirconia fiber molded article of the present invention can be carried out by various methods depending on the form of the intended final product. For example, in the case of a plate-shaped molded body, it can be carried out by paper forming. That is, the above-mentioned binder, which is a crystal stabilizer, is added to a predetermined amount of zirconia fibers and dispersed in a dispersion medium to form a slurry. A plate-shaped molded product is obtained by paper-making from this slurry. During this papermaking, it is desirable that the binder is not substantially dissolved in the dispersion medium. This is because if it dissolves, the migration phenomenon cannot be prevented. Therefore, in the case of non-aqueous metal salts and oxides, water can be used as the medium, but in the case of aqueous metal salts, it is desirable to use kerosene, heavy oil, alcohols, etc. as the medium. A sizing agent such as polyvinyl acetate, carboxymethylcellulose polyacrylate, methylcellulose, or polyethylene oxide may be added to this medium for the purpose of imparting viscosity to the medium and imparting strength after drying. As a forming method other than paper molding, molding is performed by spraying a medium containing a sizing agent onto a fixed-shaped aggregate made of zirconia fibers and binder powder, or by immersing the aggregate in a sizing agent-containing medium solution. You can also do it. The molded body is usually subjected to a drying process. This drying can be carried out by various methods such as natural drying, drying by blowing air, hot air drying, and hot ray drying. The zirconia fiber molded body according to the present invention can be used after drying, but the molded body may be used only after being fired. Through this firing, the binder, which is a crystal stabilizer, contributes to bonding between the zirconia fibers and to stabilizing the crystals of the zirconia fibers. The firing temperature is
It is desirable to change the amount appropriately depending on the type of metal salt or metal oxide of the binder to be added. For example, its temperature is 1300-2000°C. Heat to firing temperature,
This is maintained for a predetermined period of time to obtain a zirconia fiber molded body. The zirconia fiber molded article of the present invention can be used as heat insulating materials for various high-temperature furnaces, catalyst carriers, special filters, high-temperature heating elements, setters, mold release materials, and the like. (Example) Hereinafter, the present invention will be explained using specific examples. Example 1 Zirconia 100 with an average diameter of 5 μm and an average length of 20 to 30 mm
Magnesium carbonate powder with an average particle size of 1 to 5 μm per 100 parts by weight of % fiber (manufactured by Shinagawa Shirorenga Co., Ltd.)
A suspension for papermaking was prepared by adding 10 parts by weight to water as a medium. A plate-shaped molded body was formed from this suspension by paper forming. After molding, dry at 100℃ for 24 hours, then 1600℃
A zirconia fiber molded body was produced by firing at ℃. Table 1 shows the properties of the molded product obtained. Example 2 To 100 parts by weight of lime-stabilized zirconia fibers (manufactured by Shinagawa Shiroenga Co., Ltd.) with an average diameter of 5 μm and an average length of 20 to 30 mm, 15 parts by weight of calcium carbonate powder with an average particle size of 5 to 10 μm was added to water as a medium. A suspension for papermaking was prepared. Thereafter, a fiber molded body was prepared in the same manner as in Example 1. Table 1 shows the properties of the molded product obtained. Example 3 50 parts by weight of ittria-stabilized zirconia fibers with an average diameter of 5 μm and an average length of 20 to 30 mm and an average diameter of
A suspension for papermaking was prepared by adding 50 parts by weight of magnesia-added zirconia fibers having a diameter of 5 μm and an average length of 2030 mm and 5 parts by weight of ittria powder having an average particle size of 10 to 50 μm to alcohol as a medium. Hereinafter, Example 1
A fiber molded body was prepared in the same manner. Table 1 shows the properties of the molded product obtained.

[Table] As can be seen from Table 1, the zirconia fiber according to the present invention has no migration phenomenon and has a high fire resistance of 2000 to 2300°C. (Effects and Operations of the Invention) The zirconia fiber molded article according to the present invention uses a metal oxide, which is a crystal stabilizer for zirconia, and its precursor as a binder for the zirconia fiber, and this binder is applied to the surface of the zirconia fiber. Since it strongly adheres to the surface, it does not move to the surface of the molded product during drying and/or firing. Therefore, the migration phenomenon seen when using colloidal silica does not occur, and the entire molded article can have a uniform composition and strength. Metal oxides, which are crystal stabilizers for zirconia, have a high melting point of 2500 to 2800°C;
In combination with the 2600°C zirconia fiber, a zirconia fiber molded article having high fire resistance can be obtained. Since the binder used in this invention also has a crystal stabilizer effect on zirconia, it is also possible to use a zirconia fiber without adding a crystal stabilizer to the zirconia fiber.

Claims (1)

[Scope of Claims] 1. A zirconia fiber molded article comprising a zirconia fiber and a binder that is a crystal stabilizer for zirconia or a precursor that converts into the crystal stabilizer by heating. 2 Binders are oxides, carbonates, basic carbonates of magnesium, yttrium, calcium, samarium, cadmium, lanthanum, and neodymium,
The zirconia fiber molded article according to claim 1, which is at least one crystal stabilizer selected from acetate, oxalate, nitrate, chloride, and sulfate or a precursor thereof. 3. The zirconia fiber molded article according to claim 2, wherein the binder has a particle size of 0.1 μm to 0.3 mm. 4 The amount of binder added is zirconia fiber 100
The zirconia fiber molded article according to any one of claims 1 to 3, which contains 1 to 20 parts by weight in terms of oxide based on parts by weight. 5 Claims 1 to 4, in which the zirconia fiber molded body is formed by paper forming.
The zirconia fiber molded article according to any one of the above items. 6. The zirconia fiber molded article according to claim 5, wherein the medium used for papermaking does not substantially dissolve the binder. 7. Any one of claims 1 to 6, wherein the zirconia fiber is at least one type of fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and yttoria-stabilized zirconia fiber. The zirconia fiber molded article according to item 1. 8. The zirconia fiber molded article according to any one of claims 1 to 7, which has been subjected to a firing treatment.