JPS623078A - Inorganic fiber monolithic heat-resistant refractory composition and formed body thereof - 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 [Industrial Application Field] The present invention relates to an amorphous heat-insulating refractory material composition having ceramic fiber as a basic composition, and a heat-insulating refractory molded article formed from the composition.

[Conventional technology]

If the amount of water is enough to wet the bulk fibers of inorganic fibers (less than 50% water to bulk fiber), it may be said that the two are evenly mixed, but if the amount of water increases slightly, the water will separate. Alternatively, they tend to separate and do not form a homogeneous composition. Therefore, it is necessary to add a thickener to the water in order to give it appropriate plasticity and fluidity.

Acrylic polymers and polyethylene oxide are used for this purpose. These dissolve in water and have a large thickening effect with a small amount, dispersing fibers and coexisting fine powders in water (solution) and forming a homogeneous composition.
These also have a large thickening effect and dispersion effect, and when attempting to separate only water (solution) from the composition later, they have extremely poor over-dehydration properties. It cannot be improved.

[Problem that the invention seeks to solve]

The present invention provides an integrated refractory heat-resistant wall with no joints that deforms freely under relatively large stress, such as plastic refractories, but only deforms under small stress such as its own weight. On the one hand, it is an inorganic fibrous heat-insulating and fire-resistant composition (first composition) that can be constructed, and on the other hand, it is a composition containing a large amount of water in the form of slurry, due to its excellent fluidity. If the material has the property of easily filling small gaps and the surrounding area or a part thereof is water-absorbing or porous material, the above composition is easily dehydrated and reduced to the above-mentioned first composition with a much lower water content. The composition is an inorganic fibrous refractory material composition (second composition) having the desired properties, and there are compositions exhibiting many intermediate properties between the first composition and the second composition. Furthermore, the desired or required shape can be easily formed by press molding in the case of the first composition, vacuum forming in the case of the second composition, pouring into porous molds, gaps between ceramic fiber walls, etc. It has a wide composition range that allows it to be formed into molded products with a wide range of physical properties (bulk specific gravity, air permeability, thermal conductivity, etc.) by drying and firing.

The composition according to the present invention uses water as a medium, and even if it contains a large amount of water, it becomes a homogeneous slurry, but it is extremely easy to dehydrate, and expensive colloidal silica or colloidal alumina and other emulsions can be removed. Most of it remains in the dehydrated composition, and only a small proportion is lost in the wastewater.

[Means for solving problems]

The inventors selected a thickening agent that has a moderate thickening effect and a low electrical polarity when dissolved in water.

These include methylcellulose, starch, and PVA. These are soluble in water, have a moderate thickening effect, and do not show great resistance when used later.

One of the basic materials of the present invention is bulk fiber,
At the same time, the addition of refractory fine powder has an extremely excellent effect depending on the composition and the high-temperature usage conditions of the molded article. For example, its addition can improve fire resistance, corrosion resistance, thermal conductivity, strength, etc.

Any fine powder of a normal refractory material such as alumina, mullite, clay, zircon, silica, zirconia, silicon nitride, silicon carbide, etc., which is finer than about 200 μm, can be easily mixed with the fibers. The amount should be no more than 10 times that of bulk fiber. (See Japanese Patent Publication No. 57-35087.) Next, what is required for the composition of the present invention is a binder that is effective at high temperatures. Under high-temperature usage conditions, ceramic fibers and fine powders must be bonded together to maintain a certain shape and have the necessary strength to form a heat insulating or fireproof wall. The binder used for this purpose is colloidal silica or colloidal alumina. These are commonly used as binding materials for ceramic fibers, but colloidal silica or colloidal alumina is agglomerated and cross-linked into fibers or fine powder, and the colloidal silica and colloidal alumina are wastefully discharged into wastewater. It is quite difficult to prevent this from happening.

In the present invention, an emulsion of higher fatty acids is used as the aggregating material. Particularly good are emulsions of stearic acid, for example, in which colloidal silica is agglomerated in a methylcellulose solution to form a large secondary emulsion, which engages and crosslinks ceramic fiber fibers or fine powders. form. Moreover, the composition is a homogeneous, flexible material or slurry-like material, and when dehydrating later, most of the water (solution) can be easily separated while maintaining the crosslinked structure. Conventionally, when colloidal glue is used as a binder for ceramic fibers, when the mixed composition is dried, a phenomenon (referred to as migration) occurs in which colloidal silica moves to the outer surface of the composition as water evaporates. The composition of the present invention prevents this migration of colloidal silica and provides a dry product with uniform hardness.

Next, although not essential to the present invention, the first requirement that makes the present invention more effective is the addition of glycerin as a deformation preventing material. When the present composition is press-molded to form a thin plate and then dried, it is necessary to maintain the flatness of the thin plate, but this is actually very difficult.

The present inventors have discovered that by adding glycerin to the composition of the present invention, deformation during drying can be effectively prevented. However, the reason for this has not yet been elucidated.

Next, when the present composition is dehydrated, the effect of the wax emulsion in imparting fluidity to a certain dehydrated composition will be discussed.

Wax emulsion binds to crosslinked large particles formed from higher fatty acid emulsion and colloidal silica, and during dehydration, it effectively drains the water (solution) between the large particles and improves the mutual sliding between the button large particles. It is believed that this improves the moldability of the partially dehydrated composition. Without the addition of wax emulsion, fluidity is poor and moldability is poor. Addition of wax emulsion solves these problems, but at the same press pressure, a molded product with a smaller bulk specific gravity can be obtained than one without the addition of wax emulsion.

Next, conditions necessary for the configuration of the present invention will be explained.

(a) The amount of water added is 50 parts or more per 100 parts of bulk fiber.If the amount of water added is as small as 50 parts, the bulk fiber is only in a damp or wet state, and the appropriate plasticity is not achieved. cannot be given.

When the amount of water is large, there is no problem and the composition can be dehydrated to an appropriate amount.

Φ) Methyl cellulose, starch, and PVA as thickeners are added in an amount of 0.5 to 10 parts per 100 parts of water, and one or a combination of two or more of the thickeners may be used. The amount of thickener naturally has upper and lower effective limits, which have been determined experimentally. If the amount of the thickener is less than 0.5 part, it will not be possible to impart appropriate viscosity to the water (solution), and as a result, the bulk fibers and coexisting fine refractory powder will not be dispersed appropriately. More than 10 parts gives excessive viscosity to the water (solution), so that water (WI-liquid) can later be extracted from this composition.
is difficult to dehydrate.

(C) Fine powder of refractory material may be added for the purpose of improving the properties of the composition during use at high temperatures.

The amount added is 1000 parts per 100 parts of bulk fiber.
below. Types of refractory fine powder include commonly used alumina, mullite, clay, silica, zircon, norconia, silicon nitride, silicon carbide, etc., and the particle size is 200.
It is preferable that μ is smaller. 1000 pieces of refractory material fine powder
If more than 100% of the refractory material is added, the proportion of fine refractory material particles agglomerating together will increase, making it difficult to obtain a homogeneous mixture with the bulk fiber.

When the amount is 100 parts or less, a uniform mixed state can be obtained in a state where it is uniformly adhered to the surface of the bulk phi-zu.

(d) To combine fibers and fine particles at high temperatures to form a heat-insulating fireproof wall, etc., and to combine with other additives to provide the composition with appropriate plasticity and fluidity as well as excellent dehydration properties. A 40% suspension of colloidal silica or colloidal alumina is used as the binder, and 5 parts per 100 parts of the bulk fiber and refractory fine powder are used.
~50 copies.

Naturally, this addition amount also has upper and lower limits. If the amount of binder added is less than 5 parts, the strength of the composition after drying will be insufficient. If the amount is 50 parts or more, the dehydration time will be longer when dehydrating this composition.

(e) The agglomerate for combining with the colloidal silica or colloidal alumina to give the composition suitable plasticity, fluidity and good dehydration properties is an emulsion of higher fatty acids. Among these, stearic acid emulsion is easily available and convenient. The amount added is 1 part of a 40% suspension of colloidal silica or colloidal alumina.
The effect appears at 0.1 part or more per 00 parts. If the amount is less than 0.1 part, no effect will be seen.

(f) Although not essential to the present invention, there are two requirements for effective addition, the first of which is glycerin. Glycerin is added after dehydrating the composition.
When drying, the amount added is 3 parts or less per 100 parts of water, which has the function of preventing the occurrence of "scratch" especially when drying a thin plate. If more than 3 parts are added, the time required for drying the composition will be too long.

(g) The second requirement is a wax emulsion.

The wax emulsion has the effect of imparting fluidity to the dehydrated product during or after dehydration of the present composition, and improves moldability during molding. The amount added is 10 parts or less per 100 parts of a 40% suspension of colloidal silica or colloidal alumina. There is no change in the effect even if 10 parts or more is added.

In addition, a molded article can be produced by using this composition and dehydrating, molding, drying, or baking it by a known method.

〔Example〕

Examples of the present invention will be described.

In Table 1, experimental parts A, C, II, and H are the present invention, and mounting points, G, and H are reference examples. (Please note that the numbers indicate the respective compounding ratios and indicate parts by weight.) A and N are compositions with moderate moisture content and flexibility, and are suitable for troweling, manual construction, or press dehydration molding. The composition is

C.2 is a slurry-like composition for pouring with a high water content,
This composition is suitable for vacuum forming and casting methods.

E is a hard composition with a low moisture content, similar to plastic refractories, and can be press-molded.

In the reference example, colloidal silica coagulation was insufficient due to insufficient amount of higher fatty acid emulsion added, and migration of colloidal silica occurred when drying the composition.
Although the surface was hardened, the inside became a soft molded body.

In Reference Example G, since the amount of thickener added was insufficient, a homogeneous composition was not formed, and the fibers and the aqueous solution were easily separated.

In Reference Example 1, the amount of colloidal silica added was insufficient, so it did not have the effect of binding fibers and fine particles, and these easily separated from the aqueous solution and did not form a homogeneous composition.

In the case of A22B, H2, and E of the present invention, the fibers and aqueous solution do not separate and combine with the fibers and fine particles to form a homogeneous composition and do not cause migration. , which creates a dry body with uniform hardness.

Claims (2)

[Claims] (1) Ceramic fiber bulk fiber 100
50 parts or more of water per 100 parts of water, 0.5 to 10 parts of one or more thickeners such as methyl cellulose, starch, PVA, etc. per 100 parts of water, and alumina, mullite, clay per 100 parts of bulk fiber. , silica, zircon, zirconia, silicon carbide, silicon nitride, etc., in an amount of 1000 parts or less of one or more types of refractory fine powder, bulk fiber, and 100 parts of the refractory fine powder, colloidal silica or colloidal A composition comprising 5 to 50 parts of a 40% suspension of alumina and 0.1 part or more of a higher fatty acid emulsion per 100 parts of a colloidal alumina or colloidal silica suspension, and optionally 100 parts of the water. In contrast, an inorganic fibrous amorphous heat insulating and refractory material composition characterized in that 3 parts or less of glycerin or/and 10 parts or less of a wax emulsion is added to 100 parts of a suspension of colloidal silica or colloidal alumina. (2) Ceramic fiber bulk fiber 100
50 parts or more of water per part, and one or more thickeners such as methyl cellulose, starch, PVA, etc. per 100 parts of water.
．． 5 to 10 parts and 100 parts of bulk fiber, alumina, mullite, clay, silica, zircon, zirconia,
A 40% suspension of colloidal silica or colloidal alumina based on 100 parts or less of one or more types of refractory fine powder such as silicon carbide and silicon nitride, and 100 parts of the bulk fiber and the refractory fine powder. 5 to 50 parts and 0.1 part or more of higher fatty acid emulsion per 100 parts of colloidal alumina or colloidal silica suspension, and if necessary, 3 parts or less of glycerin per 100 parts of water. and/or an inorganic fibrous heat-insulating and refractory molded article obtained by dehydrating, molding, drying or firing a composition in which 10 parts or less of a wax emulsion is added to 100 parts of a suspension of colloidal silica or colloidal alumina.