JPS5846342B2 - Ceramic ball manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing ceramic spheres.

Sintered ceramic microspheres are widely used as catalyst carriers and in various other applications due to their strength, heat resistance, and chemical resistance.

Conventionally, these microspheres have been produced mechanically or by dropping a sol into a single liquid to form a spherical shape.

However, the mechanical manufacturing method not only makes it difficult to obtain uniform or perfectly spherical balls, but also has the drawback of being a source of pollution.

In addition, the method of dropping into a single liquid requires a long liquid height to obtain a true sphere, which has the disadvantage of requiring a correspondingly large size of equipment.Also, this method produces oxides made of one type of cation such as alumina. The only target was

The present invention aims to solve the drawbacks and problems of these conventional methods, and its purpose is to use an extremely small device,
Moreover, it is an object of the present invention to provide a method for easily manufacturing a true spherical ceramic sphere.

Another object of the present invention is to provide a method for easily producing spinel balls made of double oxide.

As a result of intensive research to achieve the above object, the inventor of the present invention found that when producing ceramic balls using ceramic raw material sol such as aluminum, magnesium, and silica,
A liquid having a specific gravity lower than the sol and having a higher boiling point than water that does not mix with water, and a liquid having a specific gravity higher than the sol and not mixing with the high boiling point liquid and water, preferably and When dropped into a solution that has a gelling effect and consists of two layers with a liquid that has a lower specific gravity than the gel,
The dropped sol becomes spherical while falling through the high boiling point liquid, and then becomes a gel.

They were able to find out that when they stay on the interface between the two liquids and completely gel, they fall through the liquid below to form spherical objects, thus completing the present invention.

Examples of liquids that have a lower specific gravity than a sol, do not mix with water, and have a higher boiling point than water include 2-ethyl 1-hexanol, 2-heptatool, and the like.

Examples of liquids that do not mix with the high-boiling liquid and water and have a specific gravity higher than the sol that forms two layers therewith, and preferably have a specific gravity lower than the gel, include, for example, bromoform and carbon tetrachloride.

The upper layer liquid in the two-layer liquid, for example, 2-ethyl-1 hexanol, has a specific gravity of 0.83, and the sol to be dropped has a specific gravity of about 1.1 to 1.2.

Therefore, the dropped sol descends into the upper liquid, becomes spherical, and gels.

In this case, without the lower liquid of the two layers, e.g. bromoform,
It falls to the bottom of the container and cannot maintain its spherical shape.

The lower liquid supports the sol until the sol is completely gelled and can maintain its spherical shape, after which it falls through the lower liquid to obtain gel spheres.

Therefore, the thickness of the two-layer solution is shorter than that of the conventional method of forming a sphere by dropping it in a semi-liquid, and it has the advantage of being able to easily obtain a uniform sphere. are doing.

A small amount of surfactant may be mixed with the upper layer of high boiling point liquid in order to prevent the dropped liquid from coalescing and to disperse it well.

The surfactant may be nonionic or anionic.

The sols of ceramic raw materials such as aluminum, magnesium, silica, etc. do not need to be specific.

However, for example, the product obtained by hydrolyzing the alkoxide of the metal is pure, and a uniform and stable sol can be obtained, so even if different types of sols are mixed, a uniform and stable mixed sol can be obtained. Spinel spheres made of double oxides can also be easily obtained.

For example, when the sol is added to aluminum isopropoxide powder or benzene solution in water adjusted to pH 2 to 4 and hydrolyzed at room temperature, a stable and uniform gel consisting of alumina monohydrate (hereinafter referred to as pseudoboehmite) is obtained. It will be done.

Magnesium can also be obtained in the same manner.

All alcohols having 1 to 6 carbon atoms can be used as the metal alkoxide alcohol.

The viscosity of the dropped sol does not need to be a specific value,
A sol with appropriate thixotropy becomes spherical when dispersed in 2-ethyl-1-hexanol and immediately begins to gel.

In a sol having a spinel composition, the weight percent of spinel in the solution is preferably 0.6 to 1.5 weight percent, particularly 1.4 weight percent.

In the case of pseudo-boehmite, it is preferably 5 to 10%.

The diameter of the orifice through which the sol is dropped is 0.30 mmφ to 1.
The diameter may be about 10 mm, and the concentration of the sol is more affected by the spherical acid.

Example 1 Magnesium methoxide was produced by reacting metallic magnesium with methanol, and this was hydrolyzed to obtain blue side sil.

On the other hand, aluminum monohydrate (pseudo-boehmite) was prepared by hydrolysis of aluminum impropoxide, and boehmite sol was obtained by adding hydrochloric acid to peptize the aluminum monohydrate.

Both were mixed in a spinel composition (50:50 in molar ratio) to form a raw material sol.

Next, in a 100 cc beaker, add 0.2 cc of a nonionic surfactant (Liponox MCG) (manufactured by Lion Corporation) dissolved in 20 cc of 2-ethyl-1-hexanol and 10 cc of bromoform. A solution was formed.

The spinel composition sol is placed in the two-layer solution through an orifice diameter of 0.
．． It was dripped from an orifice with a diameter of 50 mm.

The sol dropped from the orifice reaches the bromoform surface of the lower liquid while being gelled.

When this state was maintained for a while, gelation was completed.

It is preferable to carry out this gelation under reduced pressure, for example, by placing the beaker into which the sol has been dropped into a desiccator and reducing the pressure, since gelation is promoted and deaeration is carried out at the same time.

When the gel sphere is strong enough to be handled by hand, drain the solution in the beaker and dry the gel sphere naturally in the air for 350 minutes.
Calcined spinel microspheres were obtained by firing at temperatures above ℃.

Example 2 Alumina gluli alone, produced by the method shown in Example 1, was dropped into a similar two-layer solution to form a gel sphere.
Alumina spheres were obtained by firing at ℃.

Claims (1)

[Scope of Claims] 1 A mixed sol of one or more ceramic raw material sols is mixed with a liquid having a specific gravity lower than that of the sol and having a higher boiling point than water that does not mix with water, and a liquid having a higher specific gravity than the sol and having the higher boiling point. A method for producing a ceramic sphere, which comprises dropping the ceramic sphere into a gelling solution consisting of two layers of a liquid and a liquid that does not mix with water, forming it into a sphere, and then drying and firing it. 2. The method for producing ceramic spheres according to claim 1, wherein the high boiling point liquid of the upper layer liquid is 2-ethyl-1-hexanol, 2-heptatool, or a mixture thereof with a surfactant. 3. The method for manufacturing ceramic spheres according to claim 1, wherein the liquid having a higher specific gravity than the sol of the lower liquid is a liquid having a lower specific gravity than the gel. 4. The method for producing ceramic spheres according to claim 1, wherein the lower liquid is fromoform or carbon tetrachloride. 5. The method for producing ceramic spheres according to claim 1, wherein the ceramic raw material sol is produced by hydrolysis of metal alkoxides such as aluminum, magnesium, and silicon.