JPH09295856A - Ceramic material composition and production of ceramic molded product therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic material composition with good moldability, and to obtain a ceramic molded product excellent in physical properties including mechanical properties at relatively low cost by using the above composition. SOLUTION: This ceramic material composition comprises coal ash, aluminum primary phosphate and a curing regulator such as alumina, and essentially contains no water. The weight ratios of the coal ash to aluminum primary phosphate and of the coal ash to curing regulator are (10:100) to (100:10) and (100:1) to (100:50), respectively. The other objective ceramic molded product excellent in physical properties including mechanical, properties is obtained at relatively low cost by heating the above composition under pressure to carry out molding and then, according as necessary, by conducting a postbaking at 200-600 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ceramic raw material composition and a method for producing a ceramic molded product from the composition, and more particularly to coal ash discharged in large quantities as industrial waste. The present invention relates to a raw material composition which can effectively utilize the above-mentioned material and gives a ceramic molded product excellent in heat resistance, mechanical properties and the like, and a method for producing the ceramic molded product from the composition at low cost.

[0002]

2. Description of the Related Art A large amount of coal is used as an energy source for thermal power generation, and a large amount of coal ash, which is the slag, is also discharged.

Of the coal ash, there are particularly fine fly ash. Fly ash is produced when pulverized coal is burned at a thermal power plant, etc., where coal ash is melted and rapidly cooled while being transported to the flue along with high-temperature combustion gas. It has become particles.
Since this has a self-hydrating action, some fly ash is used as fly ash cement.

[0004] Like flyland cement, fly ash cement sets by a hydration reaction. However, when heated to 500 ° C. or higher, the water of crystallization in the cement condensate is released, resulting in a marked decrease in mechanical strength.

[0005] On the other hand, it is also known that coal ash is mixed with an inorganic binder such as Portland cement or water glass or an organic binder such as polyvinyl alcohol, and then sintered at a high temperature to obtain a ceramic-like molded product. Since this method requires a high sintering temperature, disadvantages in terms of energy are inevitable.

[0006]

Therefore, the present inventors firstly mixed coal ash such as fly ash with a curing modifier such as monoaluminum phosphate, water and aluminum oxide, and molded and dried. Then, a method for producing a ceramic molded article having excellent heat resistance and mechanical properties by firing at a relatively low temperature of 150 to 600 ° C. was proposed (Japanese Patent Application No. 7-254898).

[0007] This method requires the use of water. However, when water is used, it is necessary to sufficiently dry it at any stage before firing, so that this process takes time, and If the drying conditions are unsuitable, there is a problem that "cracking" or the like occurs at the firing stage.

As a result of intensive studies to solve this problem, the present inventors have found that when a mixture of coal ash, an inorganic binder containing aluminum phosphate monobasic as a main component and a curing modifier is used, the mixture is It has been found that if molding is performed under heating and pressurization, it is possible to mold satisfactorily even in the absence of water substantially, and the firing process can be carried out smoothly, and a dense ceramic molded product can be obtained. The invention was reached.

Thus, the main object of the present invention is to provide a method for producing a good ceramic molded product from a system substantially free of water and a raw material composition suitable for the method.

[0010]

A ceramic raw material composition for solving the problems of the present invention contains a coal ash, an inorganic solidifying agent containing monobasic aluminum phosphate as a main component, and a hardening modifier, and substantially Is a ceramic raw material composition characterized by containing no water, and the weight ratio of each component in the composition is preferably 10/100 to 100/10 (especially, coal ash / primary aluminum phosphate). 100 / 100-1
00/20) and the coal ash / curing control agent is 100/1
-100/50 (particularly 100 / 1-100 / 30).

As the above-mentioned curing modifier, an oxide or hydroxide of at least one metal selected from aluminum, magnesium, zinc, boron and calcium is preferably used.

This ceramic raw material composition is composed of coal ash,
In addition to the respective components of the inorganic solidifying agent and the curing control agent containing the primary aluminum phosphate as a main component, it is possible to further include a reinforcing fiber. In addition, the above ceramic raw material composition,
It may be used after heating at 30 to 180 ° C. for 5 minutes to 30 hours to form a preceramic.

On the other hand, the production method of the present invention is characterized in that the above ceramic raw material composition is used as it is or after it is made into a preceramic material, then pressure-molded and then fired at 150 to 600 ° C. Is.

In this pressure molding, the above-mentioned ceramic raw material composition is filled in a mold for molding to obtain 1 to 500 Kg / c.
It is suitable for molding at a pressure of m ^2, in particular, a ceramic material composition, in a mold for molding, 1～500K
When molding at a pressure of g / cm ² , it is preferable to heat to 100 to 300 ° C.

Therefore, in the method of the present invention, the ceramic raw material composition is put into a mold for molding and heated at 100 to 300 ° C. and molded at a pressure of 1 to 500 Kg / cm ² ,
Remove from mold, 200-600 ° C, preferably 25
After heating to 0 to 600 ° C. and firing, or after molding,
200 to 600 ° C., preferably 250 while still in the mold
A method of heating to ˜600 ° C. and firing is suitably adopted.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As the coal ash used in the method of the present invention, coal ash discharged from a thermal power plant or other factory is used. Among these coal ash, uniform and fine coal ash called “fly ash” is preferably used. This fly ash melts coal ash generated when pulverized coal is burned at a thermal power plant, and is rapidly cooled while being transported to the flue with high-temperature combustion gas. It became fine particles.

On the other hand, as the inorganic binding agent (binder), there is used monoaluminum phosphate or one mainly composed of this.

The first aluminum phosphate has the chemical formula Al
₂ O ₃ · 3P ₂ 0 ₃ 6H ₂ O [that is, Al (H ₂
P0 ₄₎ a water-soluble acid phosphate salt represented by _3],
In most cases, it is commercially available as an aqueous solution, but in the present invention, as the first aluminum phosphate, a solid-phase first aluminum phosphate containing substantially no water other than bound water (crystal water), preferably Powdered aluminum monophosphate is used. This solid phase monoaluminum phosphate has a function of expressing the hardening bondability of the coal ash by reacting with the coal ash and condensation by heating in the mixed composition, and converting the mixed composition into a ceramic.

In the present invention, in addition to the above-mentioned monoaluminum phosphate, a small amount of other inorganic binders such as water glass and Portland cement may be added.

Further, in the present invention, a curing regulator (solidification accelerator) is used in addition to the coal ash and the first aluminum phosphate binder. As the curing regulator, oxides such as aluminum, magnesium, iron, zinc, boron, and calcium are suitable, and among them, alumina powder is particularly effective. Further, hydroxides such as aluminum hydroxide and calcium hydroxide are also preferably used, and carbonates such as calcium, sodium and magnesium can also be used.

Generally, the mixing ratio (weight ratio) of each of the above components in the mixed composition for forming ceramics is coal ash =
When FA, monoaluminum phosphate = P, and curing control agent (solidification accelerator) = C, the following ranges are suitable.

FA / P = 100/10 to 10/100 (preferably 100/20 to 20/100) FA / C = 100/1 to 100/50 (preferably 100/5 to 100/30) In the invention, short fibers for reinforcement, whiskers and the like may be mixed, if necessary, in addition to the above components. As the reinforcing fiber, glass fiber, carbon fiber, SiC fiber,
Aramid fiber, high molecular weight polyethylene fiber and the like are suitable. In addition, inorganic lightweight particles such as glass bubbles can be mixed to reduce the weight. The proportions of these additives are coal ash (FA) and primary aluminum phosphate (P).
2 with respect to the total weight (A + P + C) of the curing control agent (C)
0% by weight or less is appropriate.

In order to mix the above-mentioned components, the above-mentioned components are usually well mixed in a dry manner. The presence of water in the mixing step is not preferable because not only drying before molding is necessary, but also cracking is likely to occur in the subsequent firing step, and the compactness of the obtained molded article decreases.

This raw material composition contains 30 to 180
It is also possible to use it by heating it at 5 ° C., preferably 80 to 100 ° C. for 5 minutes to 30 hours to form a preceramic.
The form of the preceramic may be a powder or a pellet.

According to the method of the present invention, this ceramic raw material composition is further subjected to pressure molding and then at 150 to 600 ° C.
Preferably 200-600 ° C, more preferably 250
By firing at a temperature of up to 600 ° C., it is possible to obtain a ceramic molded product that is tough and has excellent heat resistance, and this ceramic raw material composition is put into a mold for molding at 1 to 500 Kg / cm ² , preferably Is 10 to 500 kg
A ceramic molded product can also be obtained by pressure-heating molding at a pressure of / cm ² , but it is generally preferable to use both means in combination. That is, the ceramic raw material composition is put in a mold for molding and the amount is 1 to 500 kg / cm ²
A method of heating to 100 to 300 ° C. at the time of molding under pressure is preferably adopted. Then, it is more preferable to further perform firing after this (sometimes referred to as “post-firing” in the present invention). For example, a ceramic raw material composition
Put in a mold for molding and heat to 100-300 ° C
After molding at a pressure of 500 Kg / cm ² , the molded product is taken out of the mold or left in the mold for further 200 to 600
By heating to ℃, preferably 250 to 600 ℃, it is possible to produce a good ceramics molded product having further improved mechanical properties and heat resistance.

In this molding, a known compression molding technique can be applied. That is, by using a mold having a desired shape and dimensions, applying pressure using a known mold clamping machine, and maintaining the pressure of the pressed mold at the above temperature by internal heating or external heating, the target ceramic molding You can get things.

It is appropriate that this pressure heating is carried out for at least 10 minutes, preferably for 30 minutes to 3 hours.

The post-baking in the present invention may be carried out in the mold or after taking out the molded product from the mold. The post-baking does not necessarily have to be carried out under pressure, but it may be carried out while maintaining the pressurization in the mold. The post-baking time varies depending on the post-baking temperature, but generally, 30 minutes to 30 hours is suitable at 200 to 600 ° C.

The composition of the present invention can be made into a tough ceramic molded product even if it is formed after firing at a relatively low temperature, unlike the conventional production of a ceramic molded product.
The temperature is gradually raised from about 100 ° C, and the final temperature reaches 200 ~.
0.5 to 30 at 600 ° C, preferably 250 to 400 ° C
By holding for a long time, a particularly good ceramic molded product is manufactured. The atmosphere for this post-baking may be air or an inert gas. Thus, the above ceramic raw material composition becomes a ceramic molded product that is tough and has good heat resistance even when molded / fired at such a relatively low temperature.

In the present invention, the physical properties of the obtained ceramic molded article can be changed by appropriately selecting the preparation conditions and firing conditions of the mixed composition. For example, the pressure of the pressure press is low (for example, 10 Kg / cm ²
By the following, it is possible to obtain a relatively lightweight ceramic molded product having an apparent specific gravity of about 1.0 to 1.6, and particularly 250 to 30 at a high pressure (for example, 300 Kg / cm ² or more).
When molded at a high temperature such as 0 ° C, the apparent density is 1.6 ~
It is possible to obtain a dense and high-density ceramic molded product of about 2.0.

After the production of this molded product, if necessary, coating,
Processing such as polishing and cutting may be performed.

[0032]

EXAMPLES Next, examples and comparative examples of the method of the present invention will be described, but these are intended to help the understanding of the present invention, and are not intended to limit the scope of the present invention. In addition, "part" in an example means a weight part unless there is particular notice.

[Example 1] 100 parts of fly ash obtained as coal ash of a thermal power plant was mixed with a powdery first aluminum phosphate-based inorganic binder ("first aluminum phosphate 100P" manufactured by Taki Chemical Co., Ltd.). ) 100 parts and 10 parts of alumina powder as a curing modifier were mixed to obtain a homogeneous ceramic raw material composition.

This raw material composition was prepared to have an inner size of 125 mm × 15.
It was placed in a 0 mm mold and held at a surface pressure of 300 Kg / cm ² for 120 minutes by a mold clamping machine heated to 300 ° C. to perform thermocompression molding.

After cooling, the panel-shaped ceramic molded product (molded plate) obtained by removing from the mold had an apparent specific gravity of 1.78 and a bending strength (three-point bending) of 248 Kg / c.
The m ² and the flexural modulus were 214 Ton / cm ² , showing extremely good mechanical properties.

This molded product was placed in a furnace at 1000 ° C. for 1 hour.
After standing for 2 hours, no abnormality such as bending or cracking was observed.

[Example 2] To 100 parts of fly ash,
70 parts of the powdered first aluminum phosphate-based solidifying agent (“first aluminum phosphate 100P” manufactured by Taki Chemical Co., Ltd.) and 10 parts of alumina powder were homogeneously mixed, and the obtained raw material composition was used as Example 1. Thermocompression molding was performed by using the mold clamping machine heated to 300 ° C. in the same mold and maintaining the surface pressure at 100 Kg / cm ² for 180 minutes.

After cooling, the apparent specific gravity of the panel-shaped ceramic molded product obtained by taking it out of the mold was 1.71.
The bending strength (3-point bending) was 273 Kg / cm ² , and the bending elastic modulus was 193 Ton / cm ² , which were extremely good.

This molded product was placed in a furnace at 1000 ° C. for 1 hour.
After standing for 2 hours, no abnormality such as bending or cracking was observed.

[Example 3] To 100 parts of fly ash,
A powdery first aluminum phosphate-based solidifying agent (“first aluminum phosphate 100P” manufactured by Taki Chemical Co., Ltd.) and 10 parts of alumina were homogeneously mixed, and the resulting raw material composition was prepared using the same gold as in Example 1. Using a mold clamping machine which was placed in a mold and heated to 300 ° C., the surface pressure was kept at 50 Kg / cm ² for 90 minutes to carry out thermocompression molding.

After cooling, the apparent specific gravity of the panel-shaped ceramic molded product obtained by removing from the mold was 1.66,
The bending strength (3-point bending) was 229 Kg / cm ² , and the bending elastic modulus was 171 Ton / cm ² , which were extremely good.

Further, this panel-shaped ceramic molded product was held in an electric furnace heated to 400 ° C. for 1 hour for post-baking. The apparent specific gravity of the ceramic molded product after firing was 1.72, the bending strength was 268 Kg / cm ² , and the bending elastic modulus was 186 Ton / cm ² .

This molded product was placed in a furnace at 1000 ° C. for 1 hour.
After standing for 2 hours, no abnormality such as bending or cracking was observed.

[Example 4] 100 parts of fly ash, 100 parts of powdery aluminum monophosphate-based solidifying agent ("Aluminum aluminum phosphate 100P" manufactured by Taki Chemical Co., Ltd.) and hydroxylation as a curing accelerator 10 parts of aluminum (“Hijilite” manufactured by Showa Denko KK) were mixed at room temperature for 10 minutes to obtain a ceramic raw material composition.

This raw material composition was prepared to have an internal size of 150 mm × 60.
mm mold, and using a mold clamping machine, surface pressure 346K
While pressurizing to g / cm ² , stepwise at 100 ° C, 200
C., 250.degree. C. and 300.degree. C. were held for 1 hour each. Next, the molded product taken out of the mold was transferred to an electric furnace at 300 ° C., held for 1 hour and post-baked to obtain a cured panel-shaped molded product.

The apparent specific gravity of the thus obtained molded product is 1.68, the bending strength 300 Kg / cm ^2, a flexural modulus of 112Ton / cm ^2.

This molded product was placed in a furnace at 1000 ° C. for 1 hour.
Apparent specific gravity after standing for 2 hours is 1.20, bending strength is 120 Kg / cm ² , and bending elastic modulus is 74 Ton / cm ^2.
Met. Moreover, no abnormality such as bending or cracking was observed.

Example 5 A molded plate was manufactured in the same manner as in Example 4 except that alumina (“Baicalox” manufactured by Maruto Co., Ltd.) was used in place of the aluminum hydroxide used in Example 4. Has an apparent specific gravity of 1.
55, flexural strength 225 Kg / cm ² , flexural modulus 8
It was 1 Ton / cm ² .

[Example 6] A molded plate was produced in the same manner as in Example 4 except that zinc oxide (Kanto Chemical Co., Inc., reagent grade) was used in place of the aluminum hydroxide used in Example 4. The molded plate has an apparent specific gravity of 1.82, a bending strength of 268 Kg / cm ² , and a bending elastic modulus of 133 Ton.
/ Cm ² .

Example 7 A molded plate was produced in the same manner as in Example 4, except that the ceramic raw material composition in Example 4 was mixed for 60 minutes instead of 10 minutes. The obtained molded plate has an apparent specific gravity of 1.98, a bending strength of 207 Kg / cm ² , and a bending elastic modulus of 172 Ton.
/ Cm ² .

[Embodiment 8] In Embodiment 4, except that the ceramic molded plate is fired in an electric furnace of 500 ° C. instead of being placed in the electric furnace of 300 ° C. and then fired.
A molded plate was manufactured in the same manner as in. The obtained molded plate has an apparent specific gravity of 1.74 and a bending strength of 236 Kg / cm ² ,
The flexural modulus was 121 Ton / cm ² .

[Example 9] 100 parts of fly ash, 100 parts of powdery aluminum monophosphate-based solidifying agent ("Aluminum aluminum phosphate 100P" manufactured by Taki Chemical Co., Ltd.) and hydroxylation as a curing accelerator. 30 parts of aluminum is homogeneously mixed, the obtained ceramic raw material composition is filled in a mold having an inner size of 150 mm × 60 mm, and a surface pressure of 346.7 Kg / cm ² is applied by a mold clamping machine, To 1
It was kept at 00 ° C, 200 ° C, 250 ° C, and 300 ° C for 1 hour each.

The molded product thus obtained had an apparent specific gravity of 1.53, a bending strength of 202 Kg / cm ² , and a bending elastic modulus of 92 Ton / cm ² .

[Example 10] 100 parts of fly ash,
100 parts of powdery aluminum monophosphate (reagent grade) powder and 10 parts of aluminum hydroxide were homogeneously mixed to obtain a ceramic raw material composition. This raw material composition was heated in a dryer at 150 ° C. for 6 hours to obtain powdery preceramics. Then, this pre-ceramics is 150m inside dimension
It was placed in a m × 60 mm mold and kept at a surface pressure of 400 Kg / cm ² for 3 hours using a mold clamping machine heated to 300 ° C.
Hot pressure was applied.

The molded product thus obtained had good apparent specific gravity of 1.80, flexural strength of 251 Kg / cm ² , and flexural modulus of 181 Ton / cm ² .

[Embodiment 11] 100 parts of fly ash,
100 parts of powdery aluminum phosphate-based solidifying agent ("Aluminum phosphate 100P" manufactured by Taki Chemical Co., Ltd.) and 10 parts of alumina powder as a curing accelerator were homogeneously mixed to obtain a raw material composition. Was placed in a 25 mm x 100 mm mold, and the surface pressure was 30 using a mold clamper heated to 300 ° C.
It was kept at 0 Kg / cm ² for 1 hour and subjected to hot pressing to obtain a molded plate.

The molded product had an apparent specific gravity of 1.77, a bending strength of 210 Kg / cm ² , and a bending elastic modulus of 120 Ton.
It was as good as / cm ² .

[Example 12] The amount of the powdery aluminum monophosphate-based solidifying agent ("Aluminum monophosphate 100P" manufactured by Taki Chemical Co., Ltd.) used in Example 11 was changed to 3
A ceramic molded plate was manufactured in the same manner as in Example 11 except that the content was changed to 0 part.

The apparent specific gravity of the obtained molded plate was 1.49,
Flexural strength 132 Kg / cm ² , flexural modulus 128T
on / cm ² .

[Example 13] 100 parts of fly ash,
100 parts of a powdery aluminum phosphate-based solidifying agent (“Aluminum phosphate 100P” manufactured by Taki Chemical Co., Ltd.) and 10 parts of alumina were homogeneously mixed, and the same mold as that used in Example 11 was obtained. After putting in and holding the surface pressure at 50 kg / cm ² for 90 minutes using a mold clamping machine heated to 300 ° C., hot pressing was performed to obtain a molded plate.

The molded product had an apparent specific gravity of 1.65 and a bending strength of 228 Kg / cm ^2. [Example 14] The powdery aluminum monophosphate-based solidifying agent used in Example 13 (Taki Chemical Co., Ltd.). "1st aluminum phosphate 100P" manufactured by the company, the usage amount (100 parts) is 5
A ceramic molded plate was manufactured in the same manner as in Example 13 except that the content was changed to 0 part.

The apparent specific gravity of the obtained molded plate was 1.25,
The bending strength was 50 Kg / cm ² .

[Example 15] 100 parts of fly ash,
25 parts of powdery aluminum phosphate-based solidifying agent ("Aluminum phosphate 100P" manufactured by Taki Chemical Co., Ltd.) and 6 parts of alumina were homogeneously mixed and put in the same mold as in Example 11 at 270 ° C. Surface pressure of 50K using a mold clamping machine heated to
It was kept at g / cm ² for 40 minutes and subjected to hot pressing to obtain a molded plate.

The apparent specific gravity of this molded product was 1.17, and the bending strength was 93 Kg / cm ² .

[0065]

According to the present invention as described above, it is possible to obtain a ceramic molded product which is tough and has excellent heat resistance.
In particular, it is possible to produce a heat-resistant ceramic molded product that can withstand 1000 ° C. even in a relatively low firing temperature range as described above.

Further, compared to the case where water is contained in the ceramics forming raw material composition, it is possible to obtain a formed product which is dense and has excellent mechanical properties, and a drying step is unnecessary, so that the manufacturing cost is reduced. It can be reduced.

Therefore, the ceramic molded article of the present invention is
Utilizing its characteristics, for example, in a wide range of applications such as construction materials for construction, finishing materials, construction materials such as decorative materials, road pavement materials, side walls, civil engineering fields such as water pipes, exterior members, electrical insulation members, etc. It can be used effectively.

Claims (10)

[Claims] 1. A ceramic raw material composition containing coal ash, an inorganic solidifying agent containing monobasic aluminum phosphate as a main component, and a curing regulator, and containing substantially no water. 2. The weight ratio of coal ash to monoaluminum phosphate is 10/100 to 100/10, and the weight ratio of coal ash to curing modifier is 100/1 to 100/50. The ceramic raw material composition according to claim 1, wherein 3. The curing modifier is an oxide or hydroxide of at least one metal selected from aluminum, magnesium, zinc, boron and calcium. The ceramic raw material composition described. 4. The reinforcing fiber is further contained in addition to the coal ash, the inorganic solidifying agent containing monobasic aluminum phosphate as a main component, and the curing control agent, and the reinforcing fiber is further contained. Alternatively, the ceramic raw material composition according to claim 3. 5. A ceramic material obtained by heating the ceramic raw material composition according to any one of claims 1 to 5 at 30 to 180 ° C. for 5 minutes to 30 hours to form a preceramic. Raw material composition. 6. 150 to 6 after pressure-molding the ceramic raw material composition according to any one of claims 1 to 5.
A method for producing a ceramic molded article, which comprises firing at 00 ° C. 7. The ceramic raw material composition according to any one of claims 1 to 5 is placed in a mold for molding 5 to 5.
A method for producing a ceramic molded article, which comprises press-molding at a pressure of 500 Kg / cm ² . 8. When the ceramic raw material composition is put into a mold for molding and molded at a pressure of 1 to 500 Kg / cm ² ,
Heating to 100-300 degreeC is characterized by the above-mentioned.
A method for producing a ceramic molded article as described above. 9. The ceramic raw material composition is put into a mold for molding and heated at 100 to 300 ° C. to 1 to 500 Kg.
After molding at a pressure of / cm ² , remove from the mold and
The method for producing a ceramic molded article according to claim 8, which comprises heating to 0 to 600 ° C. and firing. 10. The ceramic raw material composition is placed in a molding die and heated to 100 to 300 ° C. to 1 to 500 K.
After molding with a pressure of g / cm ² , leave it in the mold for 20
The method for producing a ceramic molded article according to claim 8, wherein the ceramic molded article is heated to 0 to 600 ° C. and fired.