JP2003238266A - Adhesive for microwave sintering furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive suitable for bonding a ceramic fiber molding by the irradiation with microwave. <P>SOLUTION: The adhesive is suitable to be applied for a microwave sintering furnace for sintering a material to be sintered with self-heating by the irradiation with microwave. The adhesive comprises an inorganic fiber, an inorganic powder and an inorganic binder. The inorganic binder in a dry state is formed into a small drop-like shape and the small drops of the inorganic binder are separated from each other. The adhesive is made from the same material as a refractory heat insulating material. The inorganic powder has a similar composition to the refractory heat insulating material and can be used if it hardly generates heat by the microwave. For example, the inorganic powder is mainly made up of alumina or silica. It is preferable that the inorganic binder has heat resistance and strong adhesive property. As the example of the inorganic binder, water glass, colloidal silica or colloidal alumina is illustrated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive suitable for use in a sintering furnace for sintering a ceramic material, a fine ceramics material or the like by microwaves by self-heating. .

[0002]

2. Description of the Related Art Conventionally, an electric furnace or a gas furnace has been generally used for sintering a material to be sintered.

However, in the case of such sintering by heating from the outside, the temperature inside the furnace can be gently increased so that the temperature difference between the surface and the inside of the object to be sintered does not become large. Was needed. Therefore, there is a problem that the sintering time becomes long.

Therefore, in order to solve such a problem, a method of sintering a material to be sintered by microwave has been proposed (for example, Japanese Patent Laid-Open No. 6-87663). This method is excellent in shortening the sintering time and controlling the atmosphere,
Together with demands for reduction of environmental load, it is attracting attention as a future sintering method.

In the case of microwave sintering, microwaves are absorbed by the material to be sintered and the material to be sintered self-heats, so that the temperature difference between the surface and the inside of the material to be sintered becomes small. Therefore,
The sintering time can be shortened, and at the same time, the material to be sintered can be uniformly sintered.

[0006] Further, in the sintering of the material to be sintered by microwaves by self-heating, the material to be sintered is surrounded by a refractory heat insulating material,
It has been found that by suppressing the generation of a temperature gradient due to radiative cooling of the material to be sintered, the material to be sintered can be more uniformly sintered.

[0007]

A furnace for microwave sintering has a structure in which a refractory heat insulating material is arranged inside a furnace shell, and a material to be sintered is surrounded by the fire resistant heat insulating material. In this structure, there is a space between the furnace shell and the refractory insulation except for the bottom. Here, as the fireproof heat insulating material, a molded product integrally formed by using ceramic fibers as a main component has been used.

However, as the furnace becomes larger, it becomes difficult to integrally form the fireproof heat insulating material. Therefore, it came to be divided and manufactured. The divided refractory heat insulating material needs to be bonded when it is installed in the furnace. Also, an adhesive is required when repairing the refractory insulation.

It is an object of the present invention to provide an adhesive material which generates little heat even when irradiated with microwaves and is suitable for bonding ceramic fiber molded products.

[0010]

When the solution means of the present invention is exemplified, it is an adhesive material as described in claims 1 and 2.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The adhesive material of the present invention is preferably
It consists of inorganic fibers, inorganic powder and inorganic binder. When the adhesive is dry, the inorganic binder is in the form of droplets and they exist in a discrete state.

The adhesive is preferably made of the same material as the refractory heat insulating material. This is because if the materials are similar, the characteristics are similar, reaction does not easily occur, and deterioration of the fireproof heat insulating material is small.

The inorganic powder used in the adhesive of the present invention can be used as long as it has a composition similar to that of the refractory heat insulating material and is relatively resistant to heat generation by microwaves. For example, it is preferable to use alumina or silica as the main component. The reason for this is that the ceramic fibers used for the refractory insulation are usually made of alumina-silica. Specific examples of such an inorganic powder include alumina powder, silica powder, and mullite powder.

Further, in order to make the adhesive material exhibit spalling resistance, it is desirable to include an inorganic fiber as a reinforcing material. In microwave sintering, heating in a short time,
Since it is cooled, it is required to withstand thermal spalling. Using inorganic fibers as a reinforcing material
It is effective in developing spalling resistance.

Further, since the refractory heat insulating material is fibrous, it is effective to contain the inorganic fiber in order to improve compatibility with the fire resistant heat insulating material.

As such an inorganic fiber, for example, alumina silica fiber, alumina fiber, or mullite fiber can be used.

The inorganic binder used in the present invention preferably has heat resistance and strong adhesive strength. Examples of such inorganic binders include water glass, colloidal silica and colloidal alumina. One or more kinds of these inorganic binders may be used.

The inorganic binder is in the form of droplets in a dried state, and many of them are dispersed.

The present inventor has discovered that the amount of heat generated is reduced by making the structure of the adhesive a "droplet-discrete" structure even if the constituents of the adhesive are the same.

FIG. 1 shows a scanning electron microscope photograph of the microstructure of the adhesive material which generates little heat, and FIG. 2 shows a schematic view of the microstructure.

In the microstructure of the adhesive that generates little heat, the inorganic binder 1 is in the form of droplets as shown in FIGS. 1 and 2, and a large number of droplet-like binders 1 are present. The adhesive is spread evenly throughout the adhesive. And
The binding of the inorganic powder 2 or the inorganic fibers 3 by the inorganic binding material 1 is partial.

The adhesive material having such a "small droplet dispersion" structure hardly raises the temperature even when irradiated with microwaves.

There are few particles (particles or fibers) bonded to each other which form the adhesive, and the binder 1 becomes a droplet.
When a large number of droplet-shaped binders 1 are dispersed, the heat generated by the adhesive is small, and deterioration of the fireproof heat insulating material can be prevented. Furthermore, microwave energy is rarely used in the adhesive material, and energy-efficient sintering can be achieved.

The "droplet discrete" structure of such an adhesive is
For example, a method of using two kinds of binders with different charges,
It can be formed by a method of adjusting the water content of the adhesive at the time of adhesion.

As the refractory heat insulating material used for microwave sintering, a material capable of transmitting microwaves and having a high heat insulating property can be preferably used. If the microwave is absorbed by the refractory heat insulating material and energy is consumed, as a result, the amount of energy required for sintering the material to be sintered is significantly increased.

Further, in order to prevent a temperature drop due to radiative cooling, it is desirable that the refractory heat insulating material has a high heat insulating property.
Further, it is desirable for the refractory insulation to have high spalling resistance properties.

To satisfy such characteristics, for example,
A ceramic fiber board whose main component is alumina-silica fiber is used as a fireproof heat insulating material. The ceramic fiber board is capable of transmitting microwaves, has excellent heat insulation and fire resistance, and has high spalling resistance, and thus can be particularly preferably used.

The adhesive of the present invention is particularly suitable for adhering such an inorganic fiber fireproof heat insulating material.

[0029]

EXAMPLES Next, the present invention will be described more specifically by showing Example 1 and Comparative Example 1. This is merely an example and is not a limitation of the present invention.

Example 1 100 parts by weight of alumina powder, 8 parts by weight of alumina silica fiber, 0.8 parts by weight of carboxymethyl cellulose, 1.0 part by weight of inorganic thickener, 6 parts by weight of colloidal silica having a (-) charge, 6 parts by weight of colloidal alumina having a (+) charge and 50 parts by weight of water were mixed.

Next, using this mixture as an adhesive, 1 is applied to the surface of a ceramic fiber board having a thickness of 40 mm (FMX-17SR manufactured by Toshiba Monoflux Co., Ltd.).
It was applied in a thickness of mm, the same ceramic fiber board was overlaid thereon, and two ceramic fiber boards were adhered to each other. The application method may be trowel application, brush application, spraying, or the like.

After that, the two ceramic fiber boards bonded with the adhesive material are dried at 100 ° C. for 3 hours, and then dried.
It was fired at 00 ° C for 1 hour to obtain a fireproof heat insulating material.

Next, a closed space was created using this fireproof heat insulating material.

As a material to be sintered, a coffee cup-shaped pottery clay container was prepared. This pottery clay container was placed in a closed space formed of a fireproof heat insulating material, irradiated with microwaves having a frequency of 2.45 GHz, and fired.

After firing, the refractory heat insulating material was observed, but it was firmly adhered and there was no deterioration due to heat generation of the adhesive material.
The microstructure of the adhesive material was, as shown in FIG. 1, a state in which the binding material was in the form of droplets and many droplet-shaped binding materials were dispersed.

Comparative Example 1 100 parts by weight of alumina powder, 8 parts by weight of alumina silica fiber, 0.8 part by weight of carboxymethyl cellulose, 1.0 part by weight of inorganic thickener, 12 parts by weight of water glass, and 5 parts of water.
An adhesive was made by mixing 0 parts by weight.

When this adhesive was used in the same manner as in Example 1, remarkable heat generation was observed in the adhesive. In addition, deterioration of the refractory insulation was observed due to this heat generation.

When the microstructure of the adhesive of Comparative Example 1 was examined, the binder was not in the form of droplets due to the low water content of the adhesive.

Comparing Example 1 with Comparative Example 1, it can be understood that there is a difference in the use of the binder, and this difference was a significant difference in structure.

[0040]

Since the adhesive of the present invention does not easily absorb microwaves, the heat generated by the adhesive is small and the fireproof heat insulating material is not deteriorated. Therefore, it is possible to safely bond the fireproof heat insulating material surrounding the material to be sintered, and it is possible to easily manufacture a large-scale microwave sintering furnace.

Further, the use of the adhesive of the present invention makes it possible to easily repair damage to the fireproof heat insulating material. Furthermore, the adhesive of the present invention absorbs a small amount of microwaves, and thus has high energy efficiency.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing the microstructure of an adhesive material.

FIG. 2 is a schematic diagram showing a microstructure of an adhesive material.

[Explanation of symbols]

1 Inorganic binder 2 Inorganic powder 3 inorganic fibers

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuo Misu             4-4 Nihonbashi Hisamatsucho, Chuo-ku, Tokyo Itoshige             Building Toshiba Monoflux Co., Ltd. F-term (reference) 4G026 BA01 BB01 BF01 BH13

Claims (2)

[Claims] 1. An adhesive material suitable for use in a microwave sintering furnace for sintering a material to be sintered by microwave irradiation with self-heating, the inorganic fiber, the inorganic powder, and the inorganic binder. The adhesive material is characterized in that the inorganic binding material is in the form of droplets in a dried state, and the droplet-shaped inorganic binding material is dispersed. 2. An adhesive material suitable for use in a microwave sintering furnace for sintering a material to be sintered by self-heating by irradiation of microwaves, which comprises an inorganic powder and an inorganic binder. In the dry state, the inorganic binder is in the form of droplets,
Moreover, the adhesive material is characterized in that the droplet-like inorganic binder is dispersed.