KR20180068404A - Manufacturing method of ceramic hollow sphere - Google Patents

Abstract

The present invention relates to a method for manufacturing ceramic hollow body powders comprising the steps of: mixing water glass and at least one kind of water-soluble polymer selected from a group comprising polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose and polyvinylpyrrolidone; obtaining powders by performing a spray drying process for raw materials in which the water glass and the water-soluble polymer are mixed; and heat-treating the powders to obtain ceramic hollow body powders. The present invention can manufacture ceramic hollow body powders which are uniform in terms of particle sizes, have a smooth surface, a low thermal conductivity, an excellent thermal and chemical stability, excellent mechanical properties such as strength or the like, are lightweight and fireproof, have an excellent insulating efficiency, and can be used as insulating materials of buildings. Moreover, manufacturing costs are low and a manufacturing process is simple.

Description

Technical Field [0001] The present invention relates to a manufacturing method of ceramic hollow spheres,

The present invention relates to a method for producing a ceramic hollow powder having uniform particle size and smooth surface, and more particularly to a method for producing a ceramic hollow powder having uniform particle size, smooth surface, low thermal conductivity, excellent thermal and chemical stability, The present invention relates to a method for producing a ceramic hollow body powder which is excellent in fire resistance and heat insulation efficiency and which can be used as a heat insulating material for a building, and which has a low manufacturing cost and a simple manufacturing process.

It is very important to develop energy saving technology in the domestic reality that the ratio of new and renewable energy is less than 0.5% of total energy except hydraulic power.

Households, industrial sites, and other buildings account for more than 30% of the total heat loss, and a 10% reduction in energy consumption can save US $ 1 billion in annual energy consumption and 50 million tons of carbon dioxide emissions annually.

It is required to develop a coating type product which can be easily applied to the inside and outside of the building by the general public at a low cost without additional work in the existing building.

Unlike existing organic insulation materials (styrofoam), which are vulnerable to fire, heat resistant materials resistant to fire are required to be resistant to fire in the fireproofing process, and it is necessary to develop ceramic insulation materials having chemical durability that can be used in various industrial fields.

Currently, high-temperature insulation materials are harmful to human body because they have fiber or flake form, and they are regulated as construction materials when they are not. Therefore, it is necessary to develop a sphere-environmentally friendly ceramic insulating material.

In spite of its excellent performance, inorganic insulation has been neglected in the construction market due to its relatively high price compared to organic insulation.

In the case of inorganic insulation materials, the process of synthesizing ceramic particles in the form of a hollow body having a high cost of ceramic synthetic raw materials and excellent thermal insulation is very complicated and causes a rise in price.

Korean Patent Registration No. 10-0270779

A problem to be solved by the present invention is to provide a ceramic hollow body having uniform particle size, smooth surface, low thermal conductivity, excellent thermal and chemical stability, excellent strength, light weight, excellent fire resistance and heat insulation efficiency, And a method of manufacturing a ceramic hollow powder having a low manufacturing cost and a simple manufacturing process.

(A) a water-soluble polymer selected from the group consisting of polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose and polyvinylpyrrolidone, and a water-soluble polymer selected from the group consisting of polyvinylpyrrolidone, (B) spray-drying a mixture of the water glass and the water-soluble polymer to obtain a powder; and (c) heat-treating the powder to obtain a ceramic hollow powder, To obtain a ceramic hollow body powder.

The silica sol may be further mixed in the step (a).

The content of the solid content of the silica sol may be 10 to 50%, and the silica sol may be mixed so that the solid content of the silica sol is 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the water glass.

The water glass may include an aqueous solution of sodium silicate (Na ₂ SiO ₃ ) as a water glass.

The water-based water glass preferably has a solid content of 15 to 40%.

The water-soluble polymer is preferably mixed with 5 to 40 parts by weight based on 100 parts by weight of the solid content contained in the water glass.

The spray drying process is preferably performed under the conditions of an inlet temperature of 150 to 250 ° C, a gas flow rate of 300 to 900 l / hour, and a feed flow rate of 10 to 50%.

The heat treatment is preferably performed at a temperature of 500 to 600 캜.

The heat treatment is preferably performed for 3 to 12 hours.

According to the present invention, it is possible to obtain a ceramic hollow body powder having low thermal conductivity, excellent thermal and chemical stability, excellent strength, light weight, excellent fire resistance and heat insulation efficiency, and being used as a heat insulating material for buildings.

The ceramic hollow body powder produced by the present invention has a uniform particle size and a smooth surface.

According to the present invention, the manufacturing cost is low and the manufacturing process is simple.

FIG. 1 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder before a heat treatment step after spray drying according to Experimental Example 2. FIG.
FIG. 2 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder after heat treatment at 500 ° C according to Experimental Example 2. FIG.
FIG. 3 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder after heat treatment at 550 ° C. according to Experimental Example 2. FIG.
4 is a scanning electron microscope (SEM) photograph showing a cross section of a ceramic hollow body powder after heat treatment at 500 ° C according to Experimental Example 2. FIG.
5 is a scanning electron microscope (SEM) photograph showing a cross-section of a ceramic hollow powder after heat treatment at 550 ° C according to Experimental Example 2. FIG.
6 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder prepared by heat treatment in a box furnace according to Experimental Example 3. FIG.
7 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder produced by heat treatment in a rotary kiln according to Experimental Example 3;
8 is a scanning electron microscope (SEM) photograph of a ceramic hollow powder obtained by performing heat treatment for 30 minutes according to Experimental Example 4. FIG.
9 is a scanning electron microscope (SEM) photograph of a ceramic hollow powder obtained by performing heat treatment for 1 hour according to Experimental Example 4. FIG.
10 is a scanning electron microscope (SEM) photograph of a ceramic hollow powder obtained by performing heat treatment for 3 hours according to Experimental Example 4. FIG.
11 is a scanning electron microscope (SEM) photograph of a ceramic hollow powder obtained by performing heat treatment for 5 hours according to Experimental Example 4. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

A method for preparing a ceramic hollow powder according to a preferred embodiment of the present invention includes the steps of (a) mixing a mixture of polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, and polyvinylpyrrolidone (B) spray-drying a mixture of the water glass and the water-soluble polymer to obtain a powder; and (c) mixing the water-soluble polymer and the water- (c) heat-treating the powder to obtain a ceramic hollow powder.

The silica sol may be further mixed in the step (a).

The content of the solid content of the silica sol may be 10 to 50%, and the silica sol may be mixed so that the solid content of the silica sol is 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the water glass.

The water glass may include an aqueous solution of sodium silicate (Na ₂ SiO ₃ ) as a water glass.

The water-based water glass preferably has a solid content of 15 to 40%.

The water-soluble polymer is preferably mixed with 5 to 40 parts by weight based on 100 parts by weight of the solid content contained in the water glass.

The spray drying process is preferably performed under the conditions of an inlet temperature of 150 to 250 ° C, a gas flow rate of 300 to 900 l / hour, and a feed flow rate of 10 to 50%.

The heat treatment is preferably performed at a temperature of 500 to 600 캜.

The heat treatment is preferably performed for 3 to 12 hours.

Hereinafter, a method for producing a ceramic hollow body powder according to a preferred embodiment of the present invention will be described in more detail.

As shown in FIGS. 4 and 5, etc., the hollow spheres have a spherical structure in which the inside of the particles is empty. Unlike conventional materials, hollow bodies have physical properties such as relatively low density, large specific surface area, high porosity and permeability. The ceramic hollow body has a very low thermal conductivity and excellent thermal and chemical stability because the interior of the ceramic outer wall structure is empty. Particularly, silica-based hollow bodies are attracting much attention for use as insulation materials used in buildings.

When a ceramic hollow body is prepared from TEOS (tetraethyl orthosilicate) and an alkoxide, homogeneous powders having a size of several tens of nanometers can be produced, and some commercialized products are also being produced. However, the starting material is very expensive, and the yield of the final powder is low, so it is used only for special purposes.

In the present invention, a ceramic hollow powder is prepared using sodium silicate as an inexpensive raw material instead of expensive TEOS (tetraethyl orthosilicate) and alkoxide.

The water glass may be a low-priced water-based water glass, and the solid content of the water glass is preferably about 10 to 60%, more preferably about 15 to 40%. As the solid content increases, The thickness of the shell tends to increase. It is preferable to determine the solid content of the water glass in consideration of the thickness of the shell of the ceramic hollow body, the ease of the spray drying process to be described later, and the like. An example of the aqueous water glass is an aqueous solution of sodium silicate (Na ₂ SiO ₃ ). The water glass becomes the main raw material of the silica (SiO ₂ ) -based ceramic hollow powder.

The hollow body can be manufactured by various methods such as self assembly, core-shell, smelting, spray drying and the like. The core-shell or self-assembly method forms a shell on the surface of the core and obtains a hollow body by removing the core. Melted foaming is a method in which glass having a composition containing a foaming agent is foamed while melting at a high temperature. The spray drying method is a method in which a liquid sample is sprayed to make fine droplets, and then the water or the organic solvent is quickly evaporated by using heat to change into a dry powder form. The spray drying process is the most effective and economical method for manufacturing (synthesizing) the ceramic hollow powder by preparing a dry powder through solvent evaporation. Such a spray drying method is advantageous in that it can be produced at a relatively low temperature as compared with other manufacturing methods and can be manufactured quickly.

In the present invention, a ceramic hollow powder is synthesized from a low-priced water glass using a spray dryer process. It is possible to produce a large amount of ceramic hollow powder having a micro size (for example, 1 to 300 탆) by using a spray drying process using water glass, and it is possible to manufacture economical and environmentally friendly ceramic hollow bodies.

The water glass is mixed with at least one water-soluble polymer selected from the group consisting of polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, and polyvinylpyrrolidone to form a ceramic hollow body It is preferable to use it as a raw material for synthesis of powder. By mixing the water-soluble polymer, it is possible to obtain an effect of increasing the viscosity of the solution and lowering the surface tension, and the hollow particle size becomes more uniform and the particle surface becomes smoother. The water-soluble polymer is preferably mixed with 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the solid content contained in the water glass. If the content of the water-soluble polymer is low, the above-mentioned improvement effects can not be obtained. If the content of the water-soluble polymer is high, the above-mentioned improvement effects can be obtained, but the cost of the raw material may be high.

Since the ceramic hollow body (silica-based hollow body) powder synthesized from water glass is partially soluble in water and is limited in use for applications requiring fire resistance at high temperatures, silica sol (SiO ₂ sol) is mixed It is preferable to use them. The strength and refractoriness of the ceramic hollow body can be improved by mixing the silica sol. The silica sol may have a solid content of 5 to 60%, more preferably 10 to 50%, and the solid content of the silica sol may be 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the water glass. It is preferable to mix the sol. As the content of the silica sol increases, the mechanical properties and the like of the ceramic hollow body powder to be synthesized can be improved. However, since the silica sol is expensive compared to the water glass, it is preferable to determine the mixing amount in view of economical aspects and the like. Also, as the content of silica sol increases, the thickness of the ceramic hollow shell tends to increase.

A ceramic hollow body powder having excellent thermal and chemical stability can be synthesized through a spray drying process and a heat treatment process using a raw material in which the water-soluble polymer is mixed with water glass.

The spray drying process is preferably performed under the conditions of an inlet temperature of 150 to 250 ° C, a glass flow rate of 300 to 900 L / hour, and a feed flow rate of 10 to 50%.

Powder obtained through spray drying requires a heat treatment process because of its low strength. Through the heat treatment process, the powder is further swollen to form voids in the inside. As the heat treatment process, a box, a rotary kiln, or the like may be used. The heat treatment process may include maintaining the temperature at 450 to 650 ° C, more preferably 500 to 600 ° C, for 30 minutes to 12 hours, and more preferably 3 to 12 hours. If the temperature of the heat treatment is lower than 450 ° C., the effect of improving the strength may be insufficient. If the temperature of the heat treatment is higher than 650 ° C., the surface of the ceramic hollow powder may melt, The particle surface may melt or the particle size may increase, which may result in lower strength, energy consumption, and is uneconomical. When the heat treatment time is short, the surface roughness of the ceramic hollow body is high, and when the heat treatment time is 3 hours or more, the shell part is partially melted, but the surface is smooth and densified.

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited by the following experimental examples.

<Experimental Example 1>

Water-based water glass was prepared. Sodium silicate (Na ₂ SiO ₃ ) (product of Sigma Aldrich) having a solid content of 15 to 40% was used as the water glass.

The optimum process conditions were defined as shown in the following Table 1 through experiments of changing the inlet temperature, the glass flow rate and the feed flow rate with the spray drying process parameters.

Process parameters Inlet Temperature (℃) 180 Gas flow rate (l / h) 600 Feed flow rate (%) 20 Aspiration rate (%) 100

The sodium silicate solution was spray dried and heat treated to synthesize a ceramic hollow powder. Spray Dryer Depending on the type of spray dryer, the spray drying process is fluid. The spray drying process was carried out using a spray drying equipment (Mini Spray Dryer B-290, Buchi). The inlet temperature was 180 ° C., the glass flow rate was 600 l / hour, 20%, and an aspiration rate of 100%. The powders formed through the above spray drying process were heat-treated using a box or a rotary kiln since the strength was weak, and finally a ceramic hollow powder was synthesized. The heat treatment was carried out at 500 to 600 ° C for 30 minutes. Through the heat treatment process, the powder swells up to form voids in the inside.

Experiments were carried out with varying solids content of sodium silicate ranging from 15 to 40%. As the solids content increased, the thickness of the ceramic hollow shell tended to increase.

<Experimental Example 2>

Water-based water glass was prepared. A sodium silicate solution (Na ₂ SiO ₃ ) (product of Sigma-Aldrich) having a solid content of 26% was used as the water glass.

The sodium silicate solution was spray dried and heat treated to synthesize a ceramic hollow powder. The spray drying process was carried out using a spray drying equipment (Mini Spray Dryer B-290, Buchi). The inlet temperature was 180 ° C., the glass flow rate was 600 l / hour, 20%, and an aspiration rate of 100%. The powders formed through the spray drying process were heat-treated in a box furnace because the strength was weak, and finally, a ceramic hollow powder was synthesized. The heat treatment was performed to maintain the temperature at 500 DEG C for 30 minutes or at 550 DEG C for 30 minutes.

FIG. 1 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder before a heat treatment step after spray drying according to Experimental Example 2, FIG. 2 is a photograph of a ceramic hollow after heat- FIG. 3 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder after heat treatment at 550 ° C. according to Experimental Example 2, FIG. 4 is a scanning electron microscope (SEM) FIG. 5 is a scanning electron microscope (SEM) image showing a cross-section of a ceramic hollow body powder after heat treatment at 500 ° C. FIG. 5 is a scanning electron microscope (SEM) ) It is a photograph.

Referring to FIGS. 1 to 5, the powders before heat treatment showed various particle sizes due to the characteristics of spray drying. As a result of heat treatment at 550 ° C., small particles were melted and adhered to large particles. Melting did not occur at 500 ℃. Some voids were found in some broken hollow bodies. The shell thickness of the hollow body was confirmed to be about 1 탆.

<Experimental Example 3>

Water-based water glass was prepared. A sodium silicate solution (Na ₂ SiO ₃ ) (product of Sigma-Aldrich) having a solid content of 26% was used as the water glass.

The sodium silicate solution was mixed with polyethylene glycol (PEG) to form a mixture. The sodium silicate solution and the PEG were mixed in a weight ratio of 95: 5. By adding the PEG, the effect of increasing the viscosity of the solution and lowering the surface tension can be obtained, and the hollow particle size becomes more uniform and the particle surface becomes smoother.

The mixture was spray dried and heat treated to synthesize a ceramic hollow powder. The spray drying process was carried out using a spray drying equipment (Mini Spray Dryer B-290, Buchi). The inlet temperature was 180 ° C., the glass flow rate was 600 l / hour, 20%, and an aspiration rate of 100%. The powders formed through the above spray drying process were heat-treated using a box or a rotary kiln since the strength was weak, and finally a ceramic hollow powder was synthesized. The heat treatment was performed to maintain the temperature at 500 DEG C for 30 minutes.

FIG. 6 is a scanning electron microscope (SEM) photograph of the ceramic hollow body powder prepared by heat treatment in a box furnace according to Experimental Example 3, and FIG. 7 is a scanning electron micrograph It is an electron microscope (SEM) photograph.

6 and 7, the surface of the particles was smooth when heated in a rotary kiln, and small particles different from the sample were not dissolved in the large particles. It was confirmed that heat treatment using a rotary kiln was more efficient in the manufacture of a hollow body.

It was confirmed that the particle size of the hollow body was more uniform when PEG was added. Also, the hollow particle surface was smoother. When PEG was added, the color changed from white to gray after heat treatment. In the application field where color is not a problem, it is considered that the manufacturing of a hollow body by adding PEG is more advantageous for shape control.

<Experimental Example 4>

Water-based water glass was prepared. A sodium silicate solution (Na ₂ SiO ₃ ) (product of Sigma-Aldrich) having a solid content of 26% was used as the water glass.

The sodium silicate solution was mixed with polyethylene glycol (PEG) to form a mixture. The sodium silicate solution and the PEG were mixed in a weight ratio of 95: 5.

The mixture was spray dried and heat treated to synthesize a ceramic hollow powder. The spray drying process was carried out using a spray drying equipment (Mini Spray Dryer B-290, Buchi). The inlet temperature was 180 ° C., the glass flow rate was 600 l / hour, 20%, and an aspiration rate of 100%. The powders formed through the spray drying process were heat-treated using a rotary kiln because the strength thereof was weak, and finally a ceramic hollow powder was synthesized. The heat treatment was performed at 500 &lt; 0 &gt; C while changing the holding time.

FIG. 8 is a scanning electron microscope (SEM) photograph of the ceramic hollow body powder in the case of performing heat treatment for 30 minutes in Experimental Example 4, and FIG. 9 is a SEM photograph of the ceramic hollow powder 10 is a scanning electron microscope (SEM) photograph of a ceramic hollow body powder obtained by performing heat treatment for 3 hours according to Experimental Example 4, and FIG. 11 is a scanning electron microscopic (SEM) (SEM) photograph of the ceramic hollow powder obtained by heat treatment for 5 hours.

Referring to FIGS. 8 to 11, although the change of the shape according to the heat treatment holding time did not appear much, a smooth surface was observed even in the portion where the particles aggregated when the heat treatment was performed for 30 minutes. It was confirmed that the surface roughness of the particles changed in more than 30 minutes. The roughness increased with the heat treatment and it tended to be smooth again after 3 hours. And the process of melting and densifying the shell part according to the heat treatment. Therefore, it was judged that it was desirable to maintain the maximum temperature for more than 3 hours.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, This is possible.

Claims (9)

(a) mixing water glass with at least one water-soluble polymer selected from the group consisting of polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, and polyvinylpyrrolidone; ;
(b) performing a spray drying process on the raw material in which the water glass and the water-soluble polymer are mixed to obtain a powder; And
(c) heat-treating the powder to obtain a ceramic hollow powder.
The method of manufacturing a ceramic hollow powder according to claim 1, wherein the silica sol is further mixed in the step (a).
The method of claim 2, wherein the silica sol has a solid content of 10 to 50%
Wherein the silica sol is mixed so that the solid content of the silica sol is 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the water glass.
The method according to claim 1, wherein the water glass comprises an aqueous solution of sodium silicate (Na ₂ SiO ₃ ) as a water glass.
The method of manufacturing a ceramic hollow fiber powder according to claim 4, wherein the water glass has a solid content of 15 to 40%.
The method according to claim 1, wherein 5 to 40 parts by weight of the water-soluble polymer is mixed with 100 parts by weight of the solid content contained in the water glass.
The method of claim 1, wherein the spray drying process is performed under conditions of an inlet temperature of 150 to 250 ° C, a gas flow rate of 300 to 900 l / hour, and a feed flow rate of 10 to 50% Wherein the ceramic hollow body powder is produced by a method comprising the steps of:
The method of manufacturing a ceramic hollow body powder according to claim 1, wherein the heat treatment is performed at a temperature of 500 to 600 캜.
The method of manufacturing a ceramic hollow body powder according to claim 8, wherein the heat treatment is performed for 3 to 12 hours.

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