KR20130062597A - Eco-friendly castable ceramic composition and the manufacturing method of castable ceramics - Google Patents

Abstract

PURPOSE: An environmentally-friendly cast table ceramic composition is provided to keep forming the strength by adding alumina cement as a binder and alkali-free glass powder as a sintering gradient material. CONSTITUTION: An environmentally-friendly cast table ceramic composition comprises 55-90 parts by weight of ceramic powder, 10-20 parts by weight of alumina cement, and 2-30 parts by weight of alkali-free glass powder. The ceramic powder is at least alumina, zirconia, and magnesia. The environmentally-friendly cast table ceramic composition comprises the following steps. 55-90 parts by weight of ceramic powder, 10-20 parts by weight of alumina cement, and 2-30 parts by weight of alkali-free glass powder are mixed to manufacture a mixture for a cast table ceramic composition. The mixture is mixed with water and carried out in a molding and forming process. The mixture is sintered. [Reference numerals] (AA) Combining agent; (BB) Alumina cement; (CC) Ceramic powder; (DD) Alumina, zirconia, magnesia; (EE) Sintering manufacture; (FF) Alkali-free glass powder; (GG) Dry mixing; (HH) Water; (II) Additive; (JJ) Water reducing agent, dispersant, defoaming agent; (KK) Slurry manufacturing; (LL) Injection molding; (MM) Hardening by hydration; (NN) Demolding; (OO) Drying; (PP) Sintering

Description

Eco-friendly castable ceramic composition and method of manufacturing environmentally-friendly castable ceramics using the same {Eco-friendly castable ceramic composition and the manufacturing method of castable ceramics}

In the present invention, in the production of large-scale ceramics of complex shape, alumina cement is used as a binder in ceramic powder, and an alkali-free glass is added as a sintering aid, and the composition is mixed with water and castable in a mold. The present invention relates to an environment-friendly castable ceramic composition that can be densely sintered and a method for producing an environment-friendly castable ceramics using the composition.

To this end, the present invention is an environmentally-friendly castable ceramic composition which maintains the molding strength by adding an appropriate amount of alumina cement as a binder, and is environmentally friendly by reacting without volatilization in the sintering process, and by increasing the densification by adding an appropriate amount of alkali-free glass powder as a sintering aid and It provides a method for producing environmentally friendly castable ceramics using the composition.

 Due to its characteristics, ceramics are hard to change shape due to high strength and brittleness after sintering. Therefore, ceramics are usually given a certain shape in the molding process. The general method of such molding process is pressing, casting, and plasticity. Plastic forming and tape forming.

Among them, casting is to prepare a flexible suspension by dispersing the ceramic powder in a solvent to prepare a fluid suspension, and injecting the suspension into a mold such as gypsum to absorb the solvent portion by the mold, thereby preparing a ceramic molded body by a curing method. That's how. However, the suspension should preferably be dispersed so that the density gradient of the molded body and the sintered body does not occur, but it is difficult to control such dispersion conditions, so that the powder dispersed in the suspension after being injected into the mold is settled by gravity, Due to the non-uniform dispersion, the difference in water absorption occurs depending on the upper and lower positions of the suspension in the framework such as gypsum.

Even though the molded article manufactured by the incomplete process is planned and molded, a thickness difference occurs according to the point of the molded article, and a local density gradient occurs, causing cracking and deformation in the firing process.

Above all, ceramic powders other than clay are difficult to handle because of the low strength of the molded body even after molding, and a binder is used to maintain a constant molding strength, and the binder is mainly composed of a polymer such as polyvinyl alcohol (PVA). Although such a polymer is decomposed and volatilized in the calcination or sintering process, if the control of the calcination or sintering conditions is not smooth, the decomposition or volatilization adversely affects the molded body or the sintered body. Pollution of the atmospheric environment is becoming a problem such as the production of carbon dioxide by combining with oxygen in the atmosphere.

In particular, in the manufacture of large-sized and large-sized ceramics, it is difficult to set such dispersion conditions, uniform absorption rate, uniform dispersion of molded body density, and quantitative control of decomposition volatilized binder. .

On the other hand, castables are used in the manufacture of irregularly shaped refractory materials that have a non-uniform shape, meaning "flowable fluidity", and such irregularly refractory materials include binders such as alumina cement in particle size controlled refractory aggregates. It is prepared by adding 10 to 30% by weight and adding a small amount of additive to adjust workability and curing time. Binders used herein include aluminum phosphate, sodium silicate and polymer resins in addition to alumina cement. However, even in this case, there are still problems such as melt deformation due to phosphorus, soda, etc., which are components included in the binder, and decomposition volatilization of the polymer resin.

In addition, ceramics are core components applied to various industries, and need to be enlarged and complicated in accordance with the trend of large-scale production, but in the case of applying a method other than injection molding, expensive equipment and complicated processes were required for this purpose. Since the unit price is also increased, a simple and efficient molding method is urgently required without expensive equipment.

Therefore, the inventors insist on the injection molding method in the production of complex large-scale ceramics, using alumina cement as a binder in ceramic powders, for example, alumina, zirconia and magnesia powder, and using an alkali-free glass powder as a sintering aid. The composition was prepared by adding the composition, and the composition was mixed with water, castable in a mold, and then cured and sintered to produce a dense ceramic.

The present invention has been made to solve the problems as described above, the object of the present invention is to add an appropriate amount of alumina cement as a binder instead of a polymeric binder, there is no particle size separation and therefore there is no density gradient of the molded body, Large molding strength makes it easy to manufacture large molded products, eco-friendly by reacting without volatilization during sintering process. Unlike castable refractory materials, eco-friendly castable ceramic composition that enhances densification and strength by adding appropriate amount of alkali-free glass powder as sintering aid And it provides a method for producing environmentally friendly castable ceramics prepared from the composition.

In order to achieve the above object, the present invention provides a castable ceramic composition shaped by curing, wherein the composition is 55 to 90 parts by weight of ceramic powder relative to the composition weight, 10 to 20 parts by weight of alumina cement as a binder, and sintered. It provides an environmentally friendly castable ceramic composition prepared by adding 2 to 30 parts by weight of an alkali free glass as a preparation.

The ceramic powder is preferably at least one of alumina, zirconia, and magnesia.

In addition, the present invention comprises the steps of preparing a mixture for producing a castable ceramic by mixing 55 to 90 parts by weight of ceramic powder, 10 to 20 parts by weight of alumina cement as a binder, and 2 to 30 parts by weight of alkali-free glass as a sintering aid; Hardening while adding water to the mixture to form a shape; And the step of sintering the cured mixture.

In the step of hardening while being cured, it is preferable to add 0.5 to 5 parts by weight of an additive including a water reducing agent, a dispersant and an antifoaming agent to 100 parts by weight of the mixture in order to improve moldability of the castable ceramics.

In the step of adding water, it is preferable to add water to 22 to 27 parts by weight based on the weight of the composition.

Eco-friendly castable ceramic composition according to the present invention and a method for producing environmentally-friendly castable ceramics from the composition, in the production of large-scale ceramics of complex shape, using alumina cement in the ceramic powder as a binder in the molding process and an alkali-free glass powder Is prepared as a sintering aid, and the composition is mixed with water, castable in a mold, and then compactly sintered to produce eco-friendly castable ceramics. Not only can it be manufactured, it is also expected to be applied as a key member of high-tech industries such as LCD, electronics, chemical and steel industries as well as eco-friendly members such as beds and kitchen tables.

1 is a manufacturing process diagram of the environment-friendly castable ceramics according to an embodiment of the present invention,
2 is an X-ray diffraction graph of an environmentally friendly castable ceramic according to an embodiment of the present invention;
Figure 3 is a photograph of the castable ceramics for each process prepared according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

The following examples are only examples, the present invention should not be limited by the examples.

The composition ratio of the eco-friendly castable ceramic composition according to the present invention is a mixture of 55 to 90 parts by weight of ceramic powder, 10 to 20 parts by weight of alumina cement as a binder, and 2 to 30 parts by weight of alkali-free glass as a sintering aid. to be.

55 parts by weight of ceramic powder or less 20 parts by weight or more of alumina cement 30 parts by weight or more of alkali-free glass has a lower sintering temperature, but drops sharply in strength characteristics. The sinter density decreases and the porosity increases. In addition, less than 10 parts by weight of alumina cement, there is a problem that the molded body is damaged by the reduced molding strength when demolding due to failure to secure sufficient molding strength during the hydration curing process, the weight ratio of the above components have a critical significance.

In the eco-friendly castable ceramic composition of the present invention, an appropriate amount of alumina cement (alumina content of about 80% by weight), which is a hydraulic binder, is added to a viscous ceramic powder such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), and magnesia (MgO). And an alkali free glass (pyrex glass, LCD glass, etc.) powder is added in an appropriate amount as a sintering aid for densification.

Here, the hydraulic binders include gypsum and general cement, such as Portland, in addition to alumina cement, but the present invention is proposed to emphasize eco-friendliness, and physical properties such as sintering and strength may be reduced due to impurities or unwanted components. Because it can be used in part according to the purpose, but in the present invention, in consideration of purity, avoiding general cement, gypsum, etc., high purity alumina cement was used.

In addition, in the case of the glass powder added as a sintering aid, general window glass or bottle glass powder may be used, but since it contains a large amount of alkaline components, physical properties such as sintering and strength may be degraded, but some of the glass powder may be used depending on the purpose. LCD glass powder with uniform composition and eco-friendly was used. LCD glass powder is preferably used LCD waste glass. Although LCD waste glass is waste glass, it is the same as LCD glass in terms of purity, and it can be said to be environmentally friendly in terms of recycling LCD waste glass that is discarded without being recycled.

Such a composition of the present invention can be easily produced castable ceramics by a simple and general method as shown in FIG.

First, as an example of ceramic powder, alumina (Al ₂ O ₃ ) is weighed at a constant fraction with an alumina cement as a binder and an LCD glass powder as a sintering aid, and mixed and pulverized for 12 hours using an alumina ball mill and castable. Ceramic compositions were prepared. The combined composition is mixed with water to prepare a fluid slurry, poured into a plastic mold, and cured for about one day, and then demolded to form a molded body. At this time, it is necessary to add a small amount of a dispersant or a water reducing agent in order to reduce the amount of water to produce a compact molded body, it is preferable to add a small amount of antifoaming agent in order to remove bubbles generated during mixing. The molded specimens were dried in an oven at 120 ° C. for 12 hours to evaporate residual moisture, and then sintered at an temperature of 1400 to 1625 ° C. for 2 hours using an electric furnace to evaluate sinterability.

As described above, the alumina cement is added as a binder instead of the polymer binder in an appropriate amount so that there is no particle size separation. Therefore, the density gradient of the molded body does not exist, and the molding strength due to curing is easy to manufacture a large molded product. In the process, it is eco-friendly by reacting without volatilization, and unlike castable refractory materials, it is an invention that enhances densification and strength by adding an appropriate amount of alkali-free glass powder as a sintering aid.

This is because in the preparation of the castable ceramic mixture, first, the sedimentation of sedimentation due to high viscosity is minimized by using alumina cement as a binder, and second, the sedimentation of the mixture is less because of the short time of hydration curing after injection molding. Therefore, there is no density gradient of the molded body. In general injection molding, a binder is used as a crosslinking agent, and the binder itself does not have a role of hydration hardening, and the latter settles the mixture because it is faster in the latter case when the drying rate of the binder is compared with that of the alumina cement. This is less.

<Examples>

Ceramic powder is composed of alumina cement (union cement, UAC80N), which combines alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ) and magnesia (MgO) with a purity of 99% or higher, and LCD glass powder (corning glass, eagle glass) ) And Table 1 and Table 2, respectively, were weighed at a constant fraction, and mixed and ground for 12 hours by dry using an alumina ball mill to prepare a castable ceramic composition.

In order to evaluate the sinterability of the prepared composition, a circular metal mold having a diameter of 15 mm was formed into a disc at a pressure of 100 MPa and sintered at an electric furnace for 1 hour at a temperature of 1400 to 1625 ° C., followed by Archimedes It was measured using the method.

The measurement results are as shown in Table 1 and Table 2.

In addition, in order to determine the castable properties of the composition, a fluid slurry was prepared by mixing with water, poured into a rectangular plastic container, cured for about one day, and demolded to form a rectangular parallelepiped shaped body. At this time, 0.5 to 1% by weight of the dispersant (Noffco Korea 568CF) was added to the composition to reduce the amount of water and improve fluidity, and an antifoaming agent (Novco SN485) was added to the composition to remove bubbles generated during mixing. It was prepared by adding about 0.5 to 1% by weight.

The molded specimens were dried in an oven at 120 ° C. for 12 hours in order to evaporate residual moisture, and then sintered at 1400 to 1625 ° C. for 2 hours using an electric furnace to evaluate the sintered state.

 Properties of Alumina Castable Ceramic Compositions number
Alumina Cement (wt%)
Glass powder (wt%)
Alumina
(wt%)
Sintering temperature
(℃)
Relative density
(%)
Porosity
(%)
Remarks
Example 1
10
0
90
1625
91.0
6.0
Example 2
10
2
88
1600
99.4
0.5
Example 3
10
3
87
1600
99.5
0.3
Example 4
10
4
86
1600
99.3
0.5
Example 5
10
5
85
1550
96.2
0.6
Example 6
15
0
85
1550
82.9
12.5
Example 7
15
5
80
1550
96.9
0.5
Example 8
15
10
75
1550
95.2
0.7
Example 9
15
20
65
1450
94.8
0.8
Example 10
15
30
55
1400
92.0
0.6
Example 11
20
5
75
1550
95.6
0.3

Looking at the properties of the alumina castable ceramic composition shown in Table 1, it can be seen that the glass powder as a sintering aid sharply improves the sinterability even by adding a small amount, thereby increasing the sintering density, decreasing the porosity, and lowering the sintering temperature. However, when a large amount of glass powder is added, a large amount of liquid is formed during the sintering process, thereby facilitating densification, but after sintering, the density and strength are reduced due to the inclusion of anosite (CaAl ₂ Si ₂ O ₈ ) and the formation of anosite. It was found that it is preferable to use within a part. However, ananosite It is allowed to be formed to some extent, and the level of commercialization is that the glass powder can be added in the range of 2 to 30 parts by weight based on the weight of the composition.

On the other hand, alumina cement as a binder is only a binder for maintaining the molding strength, but does not significantly reduce the sintering characteristics, but acts as an impurity to the base material to form calcium aluminate (CaAl ₁₂ O ₁₉ ), thereby reducing the characteristics such as strength. Therefore, it is desirable to reduce the content to within 15 parts by weight. Like the above anosite, calcium aluminate is allowed to be formed to some extent, and the level of commercialization is that alumina cement can be added in the range of 10 to 20 parts by weight based on the weight of the composition.

Properties of Zirconia and Magnesia Castable Ceramic Compositions number
Alumina cement
(wt%)
Glass powder (wt%)
Zirconia (wt%)
Magnesia (wt%)
Sintering temperature (℃)
Relative density
(%)
Porosity
(%)
Remarks
Example 12
15
0
85
0
1450
91.9
4.1
Example 13
15
5
80
0
1450
98.5
0.3
Example 14
15
10
75
0
1450
97.2
0.4
Example 15
15
20
65
0
1400
96.6
0.4
Example 16
15
0
0
85
1500
91.4
3.3
Example 17
15
5
0
80
1500
95.2
0.7
Example 18
15
10
0
75
1450
96.9
0.4

Looking at the properties of the zirconia and magnesia castable ceramic composition shown in Table 2, it can be seen that the addition of glass powder, a sintering aid, to sharply improve the sintering properties to increase the sintering density, decrease the porosity, and lower the sintering temperature. However, when a large amount of glass powder is added, densification is promoted due to the formation of a liquid phase in the sintering process, but the density and strength are reduced due to the intercalation of the liquid phase and the phase transformation of zirconia after sintering. . However, as described above, the amount of the liquid and phase transformation of zirconia may be acceptable, so that the glass powder may be added in the range of 2 to 30 parts by weight based on the weight of the composition.

On the other hand, as can be seen in the X-ray diffraction analysis of FIG. 2, it can be seen that in the case of magnesia, spinel (MgAl ₂ O ₃ ) is formed by reacting with alumina cement as a binder during the sintering process.

Based on these results, the bending strengths of Examples 7 and 13 were measured. As a result, it was found that excellent strength characteristics were expressed in the composition of the present invention at 330 Mpa and 380 Mpa, respectively.

Through experiments for evaluating castable molding and firing characteristics of the environment-friendly castable ceramic composition according to the present invention, if the water content is large, pores are formed therein, and if the residual moisture is high after curing, cracking occurs during the sintering process.

Therefore, the composition is well mixed and homogenized according to the process shown in FIG. 1 to minimize the amount of water by adding an appropriate amount of additives such as a dispersing agent, a water reducing agent, and an antifoaming agent, and after removing the residual moisture through a drying process after hydration curing and baking, It is possible to produce a dense and excellent environmentally-friendly castable ceramics as shown in.

If the water content is 27% by weight or more in 100 parts by weight of the ceramic mixture, pores are formed in the interior, and a lot of residual moisture remains in the interior after curing, which may take a long time to dry and may be affected by cracking during firing. In addition, if the water content is 22% by weight or less, it is not easy to mix the ceramic mixture and water at the time of mixing.

As described above, the present invention has been described based on the preferred embodiments, which are only examples, and the scope of the present invention should not be construed as being limited by the above embodiments, and the protection scope of the present invention is defined by the claims. It must be interpreted.

Claims (5)

In the castable ceramic composition shaped by curing,
The composition is an environmentally-friendly castable ceramic composition, characterized in that prepared by adding 55 to 90 parts by weight of ceramic powder, 10 to 20 parts by weight of alumina cement as a binder, and 2 to 30 parts by weight of alkali-free glass as a sintering aid. . The method of claim 1,
The ceramic powder is an environmentally friendly castable ceramic composition, characterized in that at least one of alumina, zirconia, magnesia. Preparing a mixture for preparing castable ceramics by mixing 55 to 90 parts by weight of ceramic powder, 10 to 20 parts by weight of alumina cement as a binder, and 2 to 30 parts by weight of alkali-free glass with a sintering aid;
Hardening while adding water to the mixture to form a shape; And
Sintering the cured mixture;
Manufacturing method of eco-friendly castable ceramics, characterized in that comprising a. The method of claim 3, wherein
In the curing and curing step, 0.5 to 5 parts by weight of an additive including a reducing agent, a dispersant, and an antifoaming agent is added to 100 parts by weight of the mixture to improve moldability of the castable ceramics. Manufacturing method. The method of claim 3, wherein
In the step of adding water, the method of producing eco-friendly castable ceramics, characterized in that the water is added 22 to 27 parts by weight based on the weight of the composition.

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