JPH04124073A - Zirconia-based complex refractory and heat-insulating material - Google Patents

Abstract

PURPOSE:To improve resistance against heat shock of a complex refractory heat-insulating material by mixing zirconia raw material with zirconia fibers. CONSTITUTION:5-100 pts.wt. zirconia fibers (e.g. yttria-added zirconia fiber having 5mum average diameter and 20-30mm average length) are added to 100 pts.wt. zirconia raw material composed of 50-100 pts.wt. zirconia hollow sphere having 0.2-5mm diameter (e.g. lime-stabilized zirconia hollow sphere) and the residual amount of zirconia powder having 0.5-100mu diameter (e.g. magnesia-- stabilized zirconia powder). Furthermore, an organic foaming agent (e.g. foamed styrol beads) and zirconia sol and/or solution of a zirconia salt as a binder are added to said mixture in amounts of respectively <=20 pts.wt. and 2-30 pts.wt. and kneaded, then the resultant mixture is subjected to press-molding, thus dried to afford the objective refractory heat-insulating material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to ceramic refractories, and more specifically to zirconia composite refractories reinforced with zirconia fibers, which are mainly used as insulation materials for high-temperature furnaces. Regarding.

[Conventional technology]

Zirconia ZrO2 has a high melting point of about 2715℃, very low thermal conductivity, low electrical resistance at high temperatures and high electrical resistance at low temperatures, and has excellent chemical stability and is basic. It also has excellent properties not found in other ceramics, such as not getting wet with acidic slag, low volatility, and a Mohs hardness of 7 or more.

Taking advantage of these properties, zirconia can be used as polishing and abrasive materials,
In addition to applications such as electronic materials, ceramic pigments, glass additives, and sensor materials, it is also used in fire-resistant molded products.
It is useful as a fireproof insulation material for high temperatures.

However, molded bodies made only of zirconia have low thermal conductivity and a large coefficient of expansion, making them susceptible to thermal shock.
Zirconia heat-insulating refractories, which are used as heat-insulating materials that take advantage of their low thermal conductivity, are also susceptible to thermal shock.

This invention was made based on the above-mentioned background, and its purpose is to provide a zirconia-based composite fire-resistant insulation material that has resistance to thermal shock without impairing the excellent properties of zirconia. be.

The present inventors tried to improve the characteristics of zirconia fireproof insulation materials by adding various reinforcing materials to zirconia hollow spheres, and as a result, they found that adding fireproof fibers would relatively improve the properties.
Based on this knowledge, as a result of further detailed research, it was discovered that adding zirconia fibers among the fire-resistant fibers would be effective in achieving the object of the invention, leading to the completion of this invention.

[Summary of the invention]

Thus, the present invention provides 100 parts by weight of zirconia raw material consisting of 50 to 100 parts by weight of zirconia hollow spheres and the remainder being zirconia powder.
The present invention relates to a zirconia composite fire-resistant heat insulating material characterized in that 5 to 100 parts by weight of zirconia fibers are added to the parts by weight.

In a preferred embodiment of the present invention, the zirconia fiber used in the present invention is at least one refractory fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and ittria-stabilized zirconia fiber, preferably ittria. It can be a stabilized zirconia fiber.

In one embodiment of the present invention, the fireproof heat insulating material can be fired.

In a preferred embodiment of this invention, the fireproof insulation material includes:
A large number of pores formed by burning off the added organic matter can be provided.

In the above embodiment, the amount of the organic substance added can be less than 20 parts by weight based on 100 parts by weight of the total amount of the zirconia raw material and zirconia fiber.

In another embodiment of this invention, the diameter of the zirconia hollow sphere can be 0.2 to 5 mm.

In a preferred embodiment of the present invention, a total of 1 zirconia sol or/and zirconia salt solution is added to the fireproof heat insulating material as a binder.
2 to 30 parts by weight per 00 parts by weight.

[Detailed description of the invention]

This invention will be explained in more detail below.

Zirconia hollow sphere The zirconia hollow sphere used in this invention is a hollow sphere made essentially of zirconia (ZrO2), and the refractory raw material powder for forming this zirconia hollow sphere is zirconia or zirconia mixed with magnesia. (
MgO), Lime (Cab), Ittria (Y 203
), or zirconia with one or more of alumina cement, chamotte, clays, calcia, magnesium carbonate, calcium carbonate, silica, and alumina. Examples include those containing 1 to 10% of the total amount.

The size of this zirconia hollow sphere is in the range of 0.2 to 5 mm in diameter. If it is less than 0.2 mm, the insulation properties are poor;
On the other hand, if it exceeds 5 mm, the pore diameter becomes too large and heat transfer occurs due to convection, resulting in poor insulation properties. The thickness of the hollow sphere is 0
．． 05-0.3mm, specific gravity 0. It is in the range of 5 to 1.5.

The content of the zirconia hollow spheres is 100% of the zirconia raw material consisting of the zirconia hollow spheres and the zirconia powder described below.
The amount is 50 to 100 parts by weight. Content is 5
If the amount is less than 0 parts by weight, the resulting fireproof heat insulating material will have poor insulation properties. It is possible to use only zirconia hollow spheres without containing zirconia material or zirconia powder.

Such zirconia hollow spheres are manufactured, for example, by melting zirconia and one or more of its crystal stabilizers such as magnesia, lime, and ittria in an arc furnace, and then blowing off the melt. (melt spraying method). An example of a product made in this way is the product name "Jirbon" manufactured by Fukushima Steel Corporation.

Alternatively, a spherical combustible material such as a styrofoam ball having a diameter of several dragons is used as a core material, and a zirconia refractory raw material powder is attached to the core material through a binder such as an aqueous polyvinyl alcohol solution to form zirconia on the surface of the core material. A zirconia hollow sphere can be manufactured by a core decomposition method in which the core material is coated with a high quality refractory raw material powder and then heated and fired at a high temperature to thermally decompose the core material and make it hollow.

Zirconia powder The zirconia powder used in this invention consists essentially of zirconium oxide represented by the chemical formula ZrO2, and may also contain zirconium compounds such as zirconium carbonate and zirconium hydroxide, or magnesia. , lime, ittria, etc., and consists of at least one of these. This powder can be obtained, for example, by a method for producing fine powder by spray drying.

This zirconia powder is added to assist in sintering the zirconia hollow spheres and zirconia fibers, and to supplement the plasticity of the clay.

In order to achieve the above purpose, the particle size of the zirconia powder should be 0.
It is necessary that the thickness is 5 to 100μ.

If the particle size exceeds 100μ, the sintering aid effect will be small, while if it is less than 0.5μ, a large amount of binder will be required and the strength of the heat insulating material will decrease.

The content of this zirconia powder is 50 to 100 parts by weight of the remaining zirconia hollow spheres, that is, 50-0 parts by weight, based on 100 parts by weight of the zirconia raw material consisting of zirconia hollow spheres and zirconia powder. When the content exceeds 50 parts by weight, the content of the zirconia hollow spheres becomes relatively small, resulting in insufficient heat insulation. Further, as described above, there are cases in which the zirconia powder is not contained.

Zirconia fibers Examples of zirconia fibers that can be used in the present invention include pure zirconia fibers, zirconia fibers added with manesia, zirconia fibers added with lime, zirconia fibers added with ittria, and mixtures thereof, and preferably zirconia fibers added with ittria. There is.

This zirconia fiber can be produced by various methods. For example, an aqueous solution of zirconium salt is used as a starting material (
It can be produced by turning it into fibers as a spinning material to form a fiber precursor (precursor), and firing the fiber precursor at a high temperature, which can be appropriately selected depending on the use, shape, etc. of the zirconia refractory. be able to.

The fiber length and fiber diameter of the zirconia fibers used in this invention are, for example, 0. 1-50em.

and 0.1 to 20 μm.

The amount of zirconia fiber added is 5 to 100 parts by weight, preferably 5 to 50 parts by weight, and more preferably 10 to 30 parts by weight per 100 parts by weight of the zirconia raw material. This is because if the amount of zirconia fiber added is less than 5 parts by weight, the fiber addition effect will be small, whereas if it exceeds 100 parts by weight, there will be too much fiber and creep deformation will easily occur due to the load or own weight during actual use. It is.

Additives In the present invention, the raw material for the molded body may contain various additives in addition to the above-mentioned components depending on the purpose. Examples of such additives include binders, porosity-forming agents, surfactants, dispersants, and flocculants.

Binders that can be used include, for example, synthetic polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylic acid, cellulose derivatives such as methylcellulose, carboxyethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and cellulose phosphate, starch and starch derivatives, Examples include animal and vegetable mucilages such as pectin, sodium alginate, and agar, as well as zirconia sol and/or zirconium salt aqueous solution.

The zirconia sol that can be used in the present invention is, for example, a milky white colloidal liquid in which zirconia having a particle size of about 70 mm is suspended in water.

The zirconium salt aqueous solution is a colloidal solution of zirconia using water as a solvent, and in this invention, for example, zirconyl acetate,
Zirconyl nitrate, zirconyl acid chloride, zirconyl sulfate,
Zirconyl ammonium carbonate and the like can be used.

In order to reduce the weight of the zirconia composite insulation material of this invention,
Further, in order to use the molded product as a filter medium, a catalyst carrier, etc., a substance that is burnt out and vaporized during the firing process and leaves a large number of pores in the molded body, that is, a porosity-forming agent may be added. Examples of such pore-forming agents include organic fibers such as organic fibers such as expanded styrene beads, expanded urethane foam beads, and polyethylene beads, as well as synthetic fibers and natural fibers such as linen thread and cotton. The amount of the spherical or fibrous organic material added as a porosity agent varies depending on the use, porosity, and pore diameter. For example, the amount of the spherical or fibrous organic substance added is less than 20 parts by weight, preferably 2 to 20 parts by weight, and more preferably 2 to 10 parts by weight to 100 parts by weight of the total amount of zirconia raw material and zirconia fiber. be. This is because if the amount exceeds 20 parts by weight, the strength of the obtained zirconia composite heat insulating material will decrease and sufficient handling strength will not be obtained.

Manufacturing method The zirconia fireproof insulation material of this invention can be prepared and molded by various methods. Specifically, in addition to methods such as isostatic press and hot press, molding methods that can be used here include -axis press,
Examples include pour molding and injection molding.

In this invention, after forming, the refractory may be dried and may or may not be subjected to a firing treatment,
It can be selected as appropriate depending on the type of components of the zirconia refractory, its use, etc. For example, the zirconia composite may be dried after being molded and used as is as a so-called unfired refractory.

In addition, firing treatment is performed when gas components generated from the added binder or firing shrinkage become a problem.

When firing, the firing temperature is, for example, 1000 to 2000
℃, preferably 1500 to 1900℃. This is because the sintering strength is weak below 1000°C, and when it exceeds 2000°C, oversintering occurs and deformation occurs.

The obtained zirconia composite refractory is cut into the desired shape.
It can be divided and used.

[For production]

The zirconia fiber used in the zirconia composite fireproof insulation material of this invention has excellent mechanical strength, so it acts as a reinforcing material for zirconia, which is the main component of refractories. Because it has a high melting point, phenomena such as decomposition and melting that often occur with refractory fibers other than zirconia fibers do not occur. Zirconia fibers are added to this refractory material, which acts as a reinforcing material, allowing for unlimited molding methods and significantly increasing the mechanical strength of the resulting molded product.

In a preferred embodiment of the present invention in which zirconia sol and/or zirconium salt aqueous solution is added as a binder, the bond between zirconia powder or zirconia fibers is strengthened, and moreover, it forms a tough film itself, and has heat resistance equivalent to that of zirconia fibers. This imparts high mechanical strength and excellent chemical stability to the resulting composite.

〔Effect of the invention〕

This invention having the above configuration and operation has the following effects.

(a) Even if there are slight scratches on the zirconia fireproof insulation material,
It has high resistance to scratches and can suppress the progression of cracks.

(b) Since it contains zirconia fibers that have excellent mechanical and thermal properties, it gives the zirconia composite refractory insulation material good resistance to thermal shock, allowing it to be used in applications where conventional zirconia refractories could not withstand it. For example, it can be used as a lining material for fast heating furnaces.

(c) Even if ordinary fine powder zirconia on the order of microns is used, it can be molded more easily by various methods than when no zirconia fiber is added.

(d) Since the heat-insulating refractory according to the present invention has excellent thermal shock resistance, it can fully utilize the low thermal conductivity of zirconia to fully exhibit its heat-insulating properties.

(e) Since this refractory contains zirconia fibers with excellent mechanical properties, it exhibits flexibility and is difficult to break under mechanical stress.

〔Example〕

This invention will be explained in more detail below using Examples and Comparative Examples, but this invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Lime-stabilized zirconia hollow spheres (CaO
5%, ZrO295%) 80 parts by weight, -0.3mm
magnesia stabilized zirconia powder (Mg0 5%, Z
rO295%) 20 parts by weight, 100 parts by weight of ittria-doped zirconia fibers (manufactured by Shirobrick) with an average diameter of 5 μm and an average length of 20 to 30 m, 1 part by weight of methylcellulose, zirconium acetate aqueous solution (ZrO2-15%)
) 5 parts by weight were added and blended, and after kneading, uniaxial pressure molding was carried out at a pressure of 50 kg/c- and drying to obtain a zirconia refractory. Table 1 shows the properties of a fired product obtained by firing this molded body at 1800°C.

Example 2 Lime-stabilized zirconia hollow spheres (Ca0
7%, Z r O2 93%), 50 parts by weight of Ittria-stabilized zirconia fibers (manufactured by Shinyo Shirorenga Co., Ltd.) with an average diameter of 5 μm and an average length of 20 to 30+n;
Adding and blending 5 parts by weight of zirconium chloride powder, 2 parts by weight of expanded polystyrene beads with an average diameter of 1 m, and 30 parts by weight of water,
After mixing, it was poured into a mold and dried to obtain a zirconia heat insulating refractory. Table 1 shows the properties of the fired product obtained by firing this refractory at 1800°C.

Comparative Example 1 A zirconia refractory was obtained and fired in the same manner as in Example 1, except that the zirconia fiber used in Example 1 was not blended. Its characteristics are shown in Table 1.

No cracking occurred after drying during the manufacturing process.

Comparative Example 2 A zirconia refractory was obtained in the same manner as in Example 2, except that the zirconia fibers used in Example 2 were not blended.

During the manufacturing process, several cracks occurred after drying, but the parts without cracks were fired. Its characteristics are shown in Table 1.

Table 1 Application agent Sa Wisteria male

Claims (7)

[Claims] 1. For 100 parts by weight of a zirconia raw material consisting of 50 to 100 parts by weight of zirconia hollow spheres and the remainder being zirconia powder,
A zirconia composite fireproof insulation material, characterized in that zirconia fibers are added in an amount of 5 to 100 parts by weight. 2. The dicornia-based composite fire-resistant insulation material according to claim 1, wherein the zirconia fiber is at least one refractory fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and yttria-stabilized zirconia fiber. 3. Claim 1, wherein the fireproof heat insulating material is fired.
Or the zirconia composite fireproof insulation material according to 2. 4. The dicornium composite refractory insulation material according to claim 3, wherein the dicornium composite refractory insulation material has a large number of pores formed by burning out organic matter to which the refractory insulation material has been added. 5. The zirconia composite fire-resistant heat insulating material according to claim 4, wherein the amount of the organic substance added is less than 20 parts by weight based on 100 parts by weight of the total amount of the zirconia raw material and the zirconia fiber. 6. The zirconia composite fireproof insulation material according to claim 1 or 5, wherein the zirconia hollow spheres have a diameter of 0.2 to 5 mm. 7. 7. The heat insulating material contains 2 to 30 parts by weight of zirconia sol or/and zirconia salt solution as a binder based on a total of 100 parts by weight of the zirconia raw material and zirconia fibers. The zirconia composite fireproof insulation material described in .