JP6873427B2 - Manufacturing method of porous ceramics - Google Patents

Description

The present invention relates to porous ceramics having a small firing shrinkage rate and firing deformation amount.

Porous ceramics are produced by various methods.
For example, "a method in which a spherical hollow resin powder composed of single pores is added, plastically molded, and a hollow synthetic resin substance that disappears during firing is mixed with a ceramic raw material, molded into a desired shape, and then fired. (See, for example, Patent Document 1).
However, this method has a problem that the glass in the sintered body increases as the firing temperature rises and the sintering proceeds, so that the voids generated by the decomposition or burning of the resin portion decrease. Another problem is that the firing shrinkage progresses as the firing temperature rises and the firing deformation amount increases.

Further, "a clay containing 27 to 80% by mass of aluminum oxide, 15 to 70% by weight of feldspar, and 3 to 40% by weight of a calcareous raw material is slurried, impregnated into a vanishing porous body, dried, and dried at 1230 to 1450 ° C. A ceramic porous body having a linear shrinkage rate of 1% or less by firing to obtain the burnt-out porous body by burning and precipitating feldspar during the firing. ”(See, for example, Patent Document 2). ) Is proposed.

Further, it is a method in which an aggregate such as silica stone is crushed into coarse particles, molded with a small amount of flux, and fired at a temperature at which the gap between the aggregates is not closed by glass. As a similar technique, there is also a proposal of a method of forming voids by combining plate-like particles and granular particles (see, for example, Patent Document 2 and Patent Document 3).

In these methods as well, since the adhesion between the aggregates is based on the glass, the aggregates gradually melt into the glass as the firing temperature rises, the amount of glass in the sintered body increases, and the sintering proceeds. Further, since the voids of the sintered body, the firing shrinkage rate, and the firing deformation amount depend on the firing temperature, if the firing temperature is lowered to secure the voids, the bonding between the aggregates becomes weak and the strength of the porous ceramics decreases. Causes the problem.
There is also a method of mixing a volatile component that decomposes at high temperature or a raw material for foamable glass in a ceramic composition and then firing the ceramic composition to generate pores in the tissue by volatilizing the volatile component that decomposes at high temperature or foaming foamable glass. For example, see Patent Document 4).

However, in this method, since the hollow resin has a smaller specific gravity than the cup soil, it is necessary to prepare the clay by kneading, so that it is possible to perform rotary molding such as slurry, rolling, extrusion, and plastic molding such as injection. Cast molding, which is one of the main molding methods for ceramics, has a problem that it cannot be carried out because the hollow resin floats and separates during slurry preparation, so the product shape must be limited.
Further, since the organic additive disappears at a low temperature and shrinkage and densification proceed in the subsequent sintering stage, there is also a problem that it is difficult to effectively form voids.

There is also a method of obtaining porous ceramics by foaming glass in a sintering process. For example, "Amorphous slag produced during the production of ductile cast iron products is crushed and sieved and granulated into a particle size range of 0.25 to 2.0 mm, and the individual particles are wrapped with plastic clay. By heating the composition in a temperature range of 900 to 1000 ° C., individual slag particles are individually foamed and sintered with each other. , A ceramic porous body characterized by having continuous penetrating pores. ”(See, for example, Patent Document 5). However, this method has a problem that the dimensional change due to firing is large as shown by the expression "from the dried raw plate, a well-shaped ceramic porous body having a volume expanded about 3 times" is shown.

Further, "a clay containing 20 to 80% by mass of aluminum oxide, 15 to 70% by weight of feldspar, and 3 to 40% by weight of a calcareous raw material is slurried, impregnated into a vanishing porous body, dried, and dried at 1230 to 1450 ° C. A ceramic porous body having a linear shrinkage of 1% or less by firing to obtain the burnt-out porous body by burning and precipitating feldspar during the firing. ”(See, for example, Patent Document 4). ) Is proposed. However, when feldspar, which is a flux, is blended in an amount of 15% or more, the firing deformation is large, and it is difficult to produce a plate-like shape other than the one shown in the examples with high accuracy.
Another problem is that the organic additive is burned off at a low temperature, and shrinkage and densification proceed in the subsequent sintering stage, so that it is difficult to effectively form voids.
As a solution to this problem, for example, there is a proposal of "a method of firing a mixture containing granular particles / plate-shaped particles in a predetermined ratio" (see, for example, Patent Document 2). However, this method has a problem that the raw material powder needs to be classified and the process is complicated.

Porous ceramics are produced by various methods. For example, "a method in which a spherical hollow resin powder composed of single pores is added, plastically molded, and a hollow synthetic resin substance that disappears during firing is mixed with a ceramic raw material, molded into a desired shape, and then fired. (See, for example, Patent Document 1).
However, this method requires the treatment of extra gas generated from the resin moiety for pore formation.

Further, "a refractory SK05a which is composed of cement and siliceous fine sand and has a chemical composition of 10% to 30% by weight of calcium oxide, 10% by weight to 15% by weight of aluminum oxide, and 50% by weight to 75% by weight of silicon dioxide. A sintered body of a molded product obtained by curing a slurry-like mixture consisting of a low refractory mortar composition of SK5a, a highly refractory aggregate having a refractory of SK12 to 18 and water by a hydration reaction, and having a low refractory. The refractory mortar composition has a structure in which highly refractory aggregates are joined to each other by a molten layer. ”By adjusting the particle size of the highly refractory aggregate, it can be made into a dense body with pores” (for example, patent). There is a proposal (see Reference 2).

Further, the average particle size of the heat-melted resin beads is 30 to 500 μm, the average particle size of the ceramic granules is 0.3 to 3.0 times the average particle size of the heat-melted resin beads, and the respective particle sizes. A ceramic raw material for pressure molding, wherein the distribution is contained in an amount of 60% by weight or more within a range of ± 50% of the average particle size. (See, for example, Patent Document 3).

In addition, "Amorphous slag produced during the production of ductile cast iron products was crushed and sieved and sized to a particle size range of 0.25 to 2.0 mm, and the individual particles were wrapped with plastic clay. The composition is molded to be in a state, and by heating the composition in a temperature range of 900 to 1100 ° C., individual slag particles are individually foamed and sintered with each other. There is a proposal of "a ceramic porous body having continuous penetrating pores." (See, for example, Patent Document 4).

Further, "a clay containing 20 to 80% by weight of aluminum oxide, 15 to 70% by weight of feldspar, and 3 to 40% by weight of a calcareous raw material is slurried, impregnated into a burnt-out porous body, dried, and dried at 1230 to 1450 ° C. A ceramic porous body having a linear shrinkage of 1% or less by firing to obtain the burnt-out porous body by burning and precipitating feldspar during the firing. ”(See, for example, Patent Document 5). ) Is proposed.

However, this method requires a step of impregnating the porous body, and has a problem that voids generated by decomposition or burning of the resin portion are reduced, and firing shrinkage progresses as the firing temperature rises, resulting in firing deformation. Increasing the amount is also a problem.

Further, Patent Document 5 discloses a porous ceramic having a skeletal structure having a linear shrinkage rate of 1% or less due to precipitation of anorthite during firing.
However, in the ceramic composition containing 15 to 70% by weight of feldspar as a binder, the amount of calcination deformation is large as expected from the comparative examples of the present invention, and the shape other than the plate shape mentioned in the examples is high. It is considered difficult to manufacture with precision.

Patent No. 3273310 JP-A-4-16570 JP-A-2002-47075 Patent No. 39979929

An object of the present invention is to provide porous ceramics having a small firing shrinkage rate and firing deformation amount.

The subject of the present invention is to remove unavoidable impurities, and to remove unavoidable impurities, based on oxides, aluminum oxide 30 to 54% by mass, calcium oxide 5 to 30% by mass, alkali metal oxide 1 to 3% by mass, silicon dioxide 15 to 56% by mass. The compounding ratio of the above components to all the components is 98% by mass or more, the molar ratio of aluminum oxide to calcium oxide is 0.9 times or more, and 15 to 35% by mass of aluminum oxide as an aluminum oxide source. A raw material composition containing 10 to 40% by mass of a calcareous raw material as a calcium oxide source and 34% by mass or less of quartz particles as a silicon dioxide source, and the total aggregate content of aluminum oxide and quartz particles is 30% by mass or more. Can be solved by a method for producing porous ceramics, which is characterized by firing at 1200 ° C to 1300 ° C.
Further, lime or wollastonite can be used as the calcareous raw material.

In the fired body according to the present invention, when feldspar and macicobite contained in Amakusa pottery stone, which are fluxes at the time of firing, are melted to form glass, they react with the surrounding calcareous raw material and aluminum oxide, and promptly annoy from the glass. High-temperature stable crystals such as sight (Ca (Al ₂ Si ₂ O ₈ )) and feldspar (Ca ₂ Al ₂ (SiO ₇ )) crystallize. As a result, aluminum oxide and quartz, which are fire-resistant aggregates in clay, are crystallized. It becomes a new aggregate that is intricately entwined with, etc. At the same time, it prevents the increase of glass, so that the glass does not fill the space between the aggregates, so that the firing shrinkage rate is small and the amount of firing deformation is small. In addition, the intricately intertwined aggregate structure realizes a high pore ratio and the aggregates do not move easily, which contributes to the improvement of the mechanical strength of the porous ceramics.

FIG. 1 is a side view illustrating a support base used for firing the porous ceramics of the present invention and a sample mounting device. FIG. 2 is a diagram illustrating a measurement point of the firing deformation amount.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples of the present invention.
As shown in Table 1, the porous ceramic fired body of the present invention excludes unavoidable impurities and contains 30 to 54% by mass of aluminum oxide, 5 to 30% by mass of calcium oxide, and 1 to 3 by mass of alkali metal oxide on an oxide basis. It contains% by mass and 15 to 56% by mass of silicon dioxide, and the blending ratio of the above components to all the components is 98% by mass or more.
Further, it is a ceramic having a molar ratio of aluminum oxide to calcium oxide of 0.9 times or more.
It contains 15 to 35% by mass of aluminum oxide as an aluminum oxide source, 10 to 40% by mass of a calcareous raw material as a calcium oxide source, and up to 34% by mass of quartz particles as a silicon dioxide source. ing.

The porous ceramics sintered body of the present invention can be produced by firing a dough prepared from a cup clay having a content of refractory aggregates such as aluminum oxide and quartz particles of 30% by mass or more. Further, this clay can be made into porcelain clay having appropriate moldability by mixing water. The prepared porcelain clay is formed into a desired shape by an arbitrary molding method such as casting molding, rokuro molding, press molding, and then dried.

Then, after drying, firing is performed at 1150 ° C. to 1350 ° C. to obtain porous ceramics having a small firing shrinkage rate and firing deformation amount.
Further, it may be fired at 600 to 1350 ° C. and then fired for decoration with paint or glaze. If the calcination temperature is too low, the strength of the substrate will be insufficient, so it is preferable to adjust the calcination temperature as appropriate.
Further, the porous ceramics after the main firing can be produced by undergoing an overpainting firing step after being decorated by transfer or the like.
A more preferable main firing temperature is 1200 ° C to 1300 ° C. If the calcination temperature is too low, stable crystals at high temperatures such as _{anorthite (Ca (Al 2} Si ₂ O ₈ )) and guerenite (Ca ₂ Al ₂ (SiO ₇ ) (Ca ₂ Al ₂ (SiO _{7)) will not crystallize.} Since it is sufficient, the strength of the substrate is lowered. On the other hand, if the main firing temperature is too high, the aggregate crystals start to melt and the amount of firing deformation becomes large, which is not preferable.

Example 1
100 parts by mass of the raw material shown in Table 1, 0.2 parts by mass of the dispersant A-6012 (manufactured by Toa Synthetic Co., Ltd.) and 27 parts by mass of water were mixed by a ball mill to obtain a slurry.
Next, a plate-shaped sample dough having a size of 20 mm × 7 mm × 125 mm was prepared by casting and molding using the prepared slurry, and then air-dried.
As shown in FIG. 1, the prepared plate-shaped sample was placed on a support base having a span of 100 mm and calcined at 1300 ° C. in an electric furnace to prepare a test piece.

Using the prepared test piece, a test was conducted by the following test method and shown in Table 2.
1. Firing shrinkage rate After measuring the width of the casting mold and the width of the sample, it was calculated by the following formula.
Firing shrinkage = (sample width) / (mold width) x 100

2. Amount of calcination deformation The amount of calcination deformation was evaluated by the maximum amount of deformation shown in FIG.
3. 3. Porosity The porosity was measured by the mercury intrusion method using a pore distribution measuring device (Autopore IV9520 manufactured by Micromeritic Co., Ltd.).

4. Water absorption rate The water absorption rate was measured by the boiling method using ASTMC373-88 (Japanese translation name, water absorption rate of pottery products, density, apparent porosity, and apparent specific gravity standard test method), and is shown in Table 2.
5. Crystal phase identification The crystal phase was identified by crushing the test piece, measuring it with an X-ray diffractometer (XPertPRO manufactured by PANalitical), and showing it in Table 2.
6. Composition analysis The composition analysis of the raw material was measured by a calibration curve method using a glass bead with a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Co., Ltd.). Table 2 shows the compounding ratio of the components of the base material and the molar ratio of aluminum oxide to calcium oxide calculated from the chemical analysis values of the raw materials and the compounding ratio.

7. Fire-resistant aggregate content The chemical composition of the raw material Amakusa clay is confirmed by a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Co., Ltd.), and the crystal phase is confirmed by an X-ray diffractometer (XPertPRO manufactured by PANalitical), and the minimum norm method is used. When the mineral composition in Amakusa pottery clay was calculated, it was 56% quartz, 12% kaolin, and 32% masicobite.
In addition, 56% of the Amakusa pottery clay content shown in Table 1 is used as the quartz content in the raw clay, and by adding the aluminum oxide content to this, the content of refractory aggregate in the clay is shown in the table. Shown in 2.
As shown in Table 2, in Example 1, the firing shrinkage rate was −0.3%, the firing deformation amount was 0.6 mm, and the porosity was 35.4%.

Examples 2-19
As a result of measuring the sample prepared in the same manner as in Example 1 in the same manner as in Example 1 except that the conditions shown in each Example in Table 1 were changed instead of the test conditions in Example 1, the calcination shrinkage ratio was found. , -2.9 to 2.1%. The amount of calcination deformation was 0 to 2.9 mm. The porosity was 11.8 to 45.2%.

Comparative Examples 1-2
Samples prepared in the same manner as in Example 1 were measured in the same manner as in Example 1 except that the conditions shown in Comparative Examples 1 and 2 in Table 1 were used instead of the test conditions in Example 1.
In Comparative Example 1 in which the molar ratio of aluminum oxide to calcium oxide was 0.79 times, which was less than 0.9, the amount of calcination deformation increased significantly to 21.5 mm.
Further, in Comparative Example 2, a sample prepared in the same manner as in Example 1 was measured in the same manner as in Example 1 except that the conditions described in the table were met.
In Comparative Example 2 in which the content of the refractory aggregate was 25.6%, which was less than 30%, the amount of firing deformation was significantly increased to 13 mm.

Further, the porous ceramics of the present invention are produced mainly containing aluminum oxide, calcium oxide, alkali metal oxide and silicon dioxide.
Specifically, (a) aluminum oxide is 30 to 55% by mass, (b) calcium oxide is 5 to 30% by mass, (c) alkali metal oxide is 1 to 3% by mass, and (d) silicon dioxide is 15 to 56% by mass. Contains%. Further, the total blending ratio of each component of (a) aluminum oxide, (b) calcium oxide, (c) alkali metal oxide, and (d) silicon dioxide to all components is 98% by mass or more.

The preferable blending ratio of aluminum oxide with respect to all the components is 31 to 54% by mass. Aluminum oxide is derived from aluminum oxide, clay minerals, kaolin minerals, pottery stones and flux. By blending 13 to 37% by mass, preferably 15 to 35% by mass of aluminum oxide as a part of the aluminum oxide source, the amount of firing deformation becomes smaller than 3 mm.
When the blending ratio of aluminum oxide is less than 13% by mass, the amount of calcination deformation cannot be sufficiently suppressed.

On the other hand, when the blending ratio of aluminum oxide is larger than 37% by mass, the blending ratio of calcareous raw materials, clay minerals, kaolin minerals, and pottery clay minerals becomes relatively small. When the blending ratio of the calcareous raw material becomes small, the amount of calcination deformation becomes insufficient due to insufficient crystallization of stable crystals at high temperature such as _{anorthite (Ca (Al 2} Si ₂ O ₈ )) and guerenite (Ca ₂ Al (AlSiO _7)). If the mixing ratio of clay mineral, kaolin mineral, and limestone clay mineral is small, the moldability is deteriorated and the yield is lowered.

The preferable blending ratio of calcium oxide with respect to all the components is 9 to 25% by mass.
By blending 10 to 40% by mass, preferably 15 to 35% by mass of a calcareous raw material such as lime or wollastonite as a calcium oxide source, the amount of calcination deformation becomes smaller than 3 mm, and the calcination shrinkage rate is also 2.9 to 2 It is in the range of 1%. If the blending ratio of the calcareous raw material is smaller than 10% by mass, the crystallization of high-temperature stable crystals such as _{anorthite (Ca (Al 2} Si ₂ O ₈ )) and guerenite (Ca ₂ Al (AlSiO _{7)) becomes insufficient, resulting in calcination deformation.} As the amount increases, the porosity decreases. On the other hand, when the blending ratio of the calcareous raw material is larger than 40% by mass, the content of fire-resistant aggregates such as quartz and aluminum oxide contained in anorthite is relatively high. It becomes too small and the amount of firing deformation becomes large.

The alkali metal oxide is derived from a flux, feldspar, clay mineral, etc., and the preferable blending ratio of the alkali metal oxide to all the components is 1 to 2.6% by mass. If the content of the alkali metal oxide is too low, it will not produce a sufficient amount of glass matrix for crystallization of _{anorthite (Ca (Al 2} Si ₂ O ₈ )) and gerenite (Ca ₂ Al (AlSiO _7)). Therefore, the strength is reduced.
On the other hand, if the content of the alkali metal oxide is too large, the amount of calcination deformation becomes large.

The porous ceramics of the present invention preferably have a blending ratio of 16 to 55% by mass with respect to all the components of silicon dioxide. If the content of silicon dioxide is too small, the _{silicon dioxide required for crystallization of anorthite (Ca (Al 2} Si ₂ O ₈ ), galenite (Ca ₂ Al (AlSiO ₇ ), etc.) will be insufficient, while silicon dioxide will be insufficient. If the content is too large, the amount of glass increases and the amount of firing deformation increases.

The molar ratio of aluminum oxide to calcium oxide is preferably 1x or more. When the molar ratio of aluminum oxide to calcium oxide is less than 0.9 times, more aluminum oxide is consumed by crystallization of _{anorsite (Ca (Al 2} Si ₂ O ₈ )) and gerenite (Ca ₂ Al (AlSiO _7)). , The residual amount of aluminum oxide, which is a fire-resistant aggregate contained in the fired body, is relatively reduced, and the amount of fired deformation is increased.
Further, the total content of the refractory aggregate contained in the clay is 30% by mass or more, which is the sum of aluminum oxide, which is a refractory aggregate, and quartz particles. When the content of the refractory aggregate is smaller than 30%, the refractory aggregate is insufficient at the time of firing and the amount of firing deformation becomes large.

Table 2 shows the shrinkage rate, the amount of calcination deformation, and the porosity together with the chemical compositions of each example and comparative example.

The porous ceramics of the present invention have a small firing shrinkage rate and a small amount of firing deformation, and can produce porous ceramics having various shapes. Therefore, a filter medium, an adsorbent, a scatter cylinder, a bioreactor carrier, a fuel cell electrode, etc. , Porous ceramics can be used in a wide range of applications.

1 ... Sample of the present invention 2 ... Sample support 3 ... Amount of deformation due to firing

Claims (1)

Excluding unavoidable impurities, it contains 30 to 54% by mass of aluminum oxide, 5 to 30% by mass of calcium oxide, 1 to 3% by mass of alkali metal oxide, and 15 to 56% by mass of silicon dioxide on an oxide basis. The compounding ratio to all the components of is 98% by mass or more, the molar ratio of aluminum oxide to calcium oxide is 0.9 times or more, 15 to 35% by mass of aluminum oxide as an aluminum oxide source, and 10 to 10 by mass as a calcium oxide source. A raw material composition containing 40% by mass of calcareous raw material and 34% by mass or less of quartz particles as a silicon dioxide source, and having an aggregate content of 30% by mass or more in total of aluminum oxide and quartz particles is produced at 1200 ° C to 1300 ° C. A method for producing porous ceramics, which is characterized by firing in.

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