JP2007039314A - Raw material for ceramic and ceramic fired article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base material for a ceramic which can basically suppress the softening of a formed body while firing, and does not cause the lack of the strength of a fired article. <P>SOLUTION: The base material for ceramic comprises 3 components of a plastic clay where feldspars and quartz containing an alkali component are removed by classification, lime and a magnesia component and an alumina component. The base material for ceramic contains each component by at least 10 wt.% or more relative to 100% of the total weight. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ceramic substrate and a ceramic fired body using the substrate.

  Table 1 shows the composition and firing temperature of the base material in the ceramic (see Non-Patent Document 1). As is apparent here, the main firing is usually performed at 1000 ° C. or higher. The purpose is to place importance on the strength of the fired body. As a result, the structure of the fired body becomes dense and tends to be composed of many glass phases and crystal phases.

Conventional ceramics in Japan are made up of three components: kaolinite and porcelain clay, feldspar, and quartz (silica), and because of their good plasticity, they can be molded using various molding methods. ing. In order to impart strength and aesthetic translucency to the fired body after the firing, a reaction for solubilizing mainly quartz and feldspar is required during firing, and a high temperature of at least 1150 ° C. is required. In the case of an excessively pulverized substrate, it is often softened (including melting phenomenon) by firing at around 1100 ° C., and it is usually said that the firing width is narrow in the ceramic industry.
On the other hand, as shown in Table 1, lime and bitter earth bases were industrialized as lime / white cloud ceramics by firing at 1100 ± 50 ° C. Furthermore, the desire to make porcelain became stronger in the 1960s, A substrate preparation test aimed at porcelain was conducted. However, it has been judged that industrialization is difficult because a melt (glass phase) is suddenly generated in a molded body that has received a heat quantity exceeding the firing width, and the softening / deformation distortion of the fired body proceeds greatly. (Non-patent documents 2 to 4).

Ceramic Engineering Handbook Volume 5 Ceramics (1989) Seizo Kawamura and Toshikazu Kurokawa “Studies on the porcelainization of kaolin-limestone bodies” Journal of the Ceramic Industry Association (88) 703-712 (1980) Seizo Kawamura and Toshikazu Kurokawa “Structure and Mechanical Strength of Kaolin-Limestone Base” Nagoya Industrial Technology Laboratory (31) 111-116 (1982) Masami Ito, Masahiro Nawa, Tsuyoshi Yano, Harukatsu Sakakibara, and Aizo Tanaka “Application of calcareous materials” Report from Aichi Prefectural Seto Ceramics Technology Center (15) 28-34 (1986)

  In the conventional ceramic substrate, quartz in the component material functions as an aggregate and a glass forming agent, and feldspar functions as a solvent, respectively. In addition, the reaction between the alkaline earth component or atmospheric gas and quartz rapidly proceeds at around 1100 ° C., and a large amount of the reaction product melt is formed, and the fired body is softened due to the melting phenomenon. As a result, deformation and distortion of the fired body are increased. The commercial ceramics listed in Table 1 are also fired at ± 50 ° C centering on the optimum firing temperature. However, if it is too low, the strength is insufficient, and if it is too high, it is softened by melting of the fired body (crushed). There was a problem. In order to prevent this softening and increase the heat resistance, a measure of adding an alumina component has also been taken, but it has not yet sufficiently suppressed softening.

  Therefore, the present invention fundamentally suppresses softening of the molded body during combustion without causing insufficient strength in the fired body, and has a high-heat-resistant ceramic substrate and a high-strength ceramic using the ceramic substrate. The object is to provide a fired body.

First, in order to fundamentally suppress the softening of the molded body during firing, the inventor avoids the presence of quartz and feldspar, which are melt forming agents, in the material constituting the substrate as much as possible. We focused on the fact that it is effective to increase the similar components.
This is because the melting point of the crystalline phase of Al ₂ O ₃ -CaO (MgO) -SiO ₂ composition system without alkali component is relatively high, and used for purification and removal of quartz in plastic clay By the reaction under the coexistence of alkaline earth from the bittern of the flocculant used to collect the minute amount of alkali in the water glass (added amount: 3% by weight 1000%) of the dispersed dispersant and the dispersed clay particles This is based on the knowledge that a large amount of melt is not formed during firing.

Therefore, in order to achieve the above object, the invention according to claim 1 is characterized in that a plastic clay from which feldspar and quartz containing alkali components are removed by classification, lime and a bitter earth component, and an alumina component. The ceramic substrate is composed of components and each component is contained at least 10% by weight or more with respect to 100% of the total weight.
In addition to the object of claim 1, the invention described in claim 2 is for ceramics to which an alkaline slurry adjusting agent is added at 3% by weight or less of 1000% of the total weight of the substrate to further improve heat resistance. It is a basic material.

Moreover, in order to achieve the said objective, invention of Claim 3 is a ceramic body of Claim 1 or 2, after shaping | molding and drying, it bakes at the temperature selected within the range of 600 to 1400 degreeC. The ceramic fired body has a bending strength of about 20 Mpa or more and a firing shrinkage rate of about 18% or less.
In addition to the object of claim 3, the invention described in claim 4 is characterized in that metakaolin, CaO, MgO, porous − Al ₂ O ₃ , α-Al ₂ O ₃ , Mullite Ca ₃ Al ₂ Si ₃ O ₁₂ , CaAl ₂ Si ₂ O ₈ , Ca ₂ Al ₂ SiO ₇ , CaAl ₂ O ₄ , Ca ₁₂ Al ₁₄ O ₃₃ , Ca ₃ The ceramic fired body contains Al ₂ O ₆ , an alumina cement-based crystal, and one or more crystals in which the MgO component is dissolved in the crystal, and contains a small amount of glass phase.

According to the ceramic substrate of claim 1, it is possible to industrially produce a heat-resistant ceramic with a wide firing temperature range, a small firing shrinkage rate, and without causing insufficient strength in the fired body. .
According to the ceramic substrate of the second aspect, in addition to the effect of the first aspect, a further improvement in strength can be expected by adding an alkaline slurry adjusting agent.
According to the ceramic fired body of claim 3, by using the ceramic substrate of claim 1 or 2, good characteristics in bending strength and firing shrinkage can be obtained. In particular, here, since the fine structure is a homogeneous porous body, it has excellent thermal shock resistance and is useful in a wide range of industrial fields such as lightweight aggregates and filters.
According to the ceramic fired body of the fourth aspect, a high-strength fired body having higher heat resistance is obtained due to the presence of a crystalline phase having a high melting point.

《Analysis of plastic clay》
The plastic clay used in the present invention is selected from at least one selected from Kibushi clay, Sasame clay, Kaolinite clay, bauxite clay, porcelain clay, and various artificial clays.
As an example, X-ray diffraction pattern of plastic clay powder of Kibushi clay, Sasame clay, Japanese name black mud produced in Dongshan, Guangdong Province, China, which is a variety of clay clays industrially mined in the Seto district of Aichi Prefecture. Figure 1 (Extracted from the joint research report of Nagoya Institute of Industrial Science and Shenyang Non-Metal Mining Research Institute "Study on the Effective Use of Clay Minerals in China-Evaluation of Porcelain for Ceramics, Evaluation of Clay and Categorization" (1990.3)) The same applies to FIGS. Along with the figures, Kibushi clay is abbreviated as (K), Sasame clay as (G), and Black mud as (B). As is apparent here, the main components kaolinite and quartz (Qtz) coexist, and the remaining amount of quartz (Qtz) has a relationship of G ≧ K> B.
In Japan (K, G) produced in temperate zone, no crystal phase other than the above kaolinite and quartz is observed, but in subtropical (B), gypsite (Al (OH) ₃ ) and Ca and Al -There was a trace of montmorillonite (m).
Furthermore, from the powder X-ray diffraction pattern of the detailed orientation data shown in FIG. 2, in comparison between (K) and (B), the water glass used for water tank (illustrated by Wg) and the gypsite (illustrated by g) ) Was confirmed. The difference between the origin of this from plastic in the clay, the weathering progresses, bauxite clay that alkali content and the SiO ₂ component of the host rock exists many leaching to alumina component (corresponding to B), Kaori It can be judged that knightly clay (equivalent to K and G) is widely used in the ceramic industry.

《Baking test of plastic clay》
The above-mentioned B, G, K, and S (Kinashiki clay from Aichi Prefecture) were pressed and then fired at temperatures from 900 ° C. to 50 ° C. to 1350 ° C. The total firing shrinkage is shown in FIG. The vertical axis represents the firing shrinkage rate, and the horizontal axis represents the firing temperature (° C.). The firing time of the compact was performed at a set temperature of 2 hours. As is clear from this, (B) is different from plastic clay made in Japan, and it is understood that the firing shrinkage is small and the fire resistance is good. As shown in FIG. 1, the cause of this improvement in fire resistance is a small amount of quartz, while Al (OH) ₃ and Ca and Al-montmorillonite contain a large amount of alumina components centered on kaolinite. It can be inferred that it is kaolinite clay (commonly called bauxite clay).

Therefore, in the ceramic substrate of the present invention, feldspar and quartz containing an alkali component and, if necessary, mica are removed from the plastic clay using a water tank or an industrial centrifuge. As shown in FIG. 1, quartz remains in industrial Minamata clay, but it is possible to remove quartz if the degree of classification is increased by centrifugation after peptization and dispersion in the laboratory. It is known that there is. This can be easily understood from the graph of FIG. FIG. 4 is a graph showing the relationship between the SiO ₂ / Al ₂ O ₃ molar ratio and the degree of classification in laboratory classification of industrially dredged Kibushi clay (K) and Sasame clay (G) ( Ikuo Shibazaki and Takehisa Maeda "Existence of Impurities (Iron, Titanium) in Minamata Kibushi Clay and Sasame Clay" (Nagoya Industrial Technology Laboratory Report 28 (8) 270-274 (1979)) This represents an ideal kaolinite composition SiO ₂ / Al ₂ O ₃ molar ratio of 2.
FIG. 5 shows ignition loss (Ig.loss), thickness of kaolinite crystal (t), peak ratio of kaolinite to quartz (Hk / Hg) and specific surface area S (m ² / g) in powder X-ray diffraction. ) (Takehisa Maeda, Shinji Watamura, Hiroyuki Mizuta, Ikuo Shibazaki “Examination of quality evaluation method by loss of ignition of ceramic clay materials” Clay Science, 27 (3) 135-146 (1987) (Excerpt) Kaolinite's ideal Ig.loss is 13.98%, but organic matter (humus) exists in both. Furthermore, the Ig.loss of Al (OH) ₃ in black mud is 34.6%, so the Ig.loss curve in Fig. 5-a appears more frequently than that of kaolinitic clay (Fig. 5-b). Yes.

Next, an alumina component is used in the ceramic substrate of the present invention. The alumina component may be one or more selected from porous Al ₂ O ₃ , hydroxide, a salt composed of a carbonate group / ammonium group / hydroxyl group and a double salt.
However, it is desirable to use raw materials with few alkali components such as Na ions as a measure for improving the fire resistance. For example, industrial waste Al (OH) ₃ sludge from the sash factory can be used as the alumina component, but since this Al (OH) ₃ contains a lot of alkaline components such as Na ions, the pH is set to 8. Use water that has been thoroughly washed.

A base composition is prepared by containing 10% by weight or more of the plastic clay thus obtained, an alumina component, and lime and a clay component (these hydroxides, carbonates, and double salts may be used). To do. Preferably, the plastic clay is selected from 10 to 60% by weight based on the base composition, the alumina component is selected from 10 to 60% by weight based on the base composition, and the lime and the clay component are selected from 10 to 40% by weight. To be 100% by weight. If necessary, water glass or the like may be added as an alkaline sludge adjusting agent at 3% by weight or less of 1000% of the total weight of the substrate.
And after shape | molding the ceramic base | substrate prepared into an arbitrary shape and making it dry, it calcinates by selecting a calcination temperature in the range of 600 to 1400 degreeC. During firing, metakaolin and mullite (3Al ₂ O ₃ · 2SiO ₂ ) produced by the thermal decomposition of kaolinite and trace amounts of alkali components that react immediately with the SiO ₂ component of the decomposition products Then, the CaO and MgO components react with the alumina component to suppress the generation of the liquid phase as much as possible, and generate many crystal phases having a relatively high melting point.

Table 2 shows typical constituent minerals, analytical values, and norm calculation values based on them. The term of the heat-resistant ceramic at the right end corresponds to the ceramic substrate of the present invention. As can be seen from the norm calculation value, it can be calculated that the SiO ₂ component is almost zero in the fired body, and it can be estimated that there is no formation of SiO ₂ glass (melt).

  Examples of the present invention will be described below.

<< Composition and firing of limestone base and its evaluation >>
The ceramic base was prepared with 16% by weight of limestone, 47% by weight of Al (OH) ₃ and 37% by weight of kaolinitic clay, and water glass was added at 3.0% by weight based on the total weight of the base body of 1000. Five crucibles (height 70 mm × diameter 81.5 mm) and rod-shaped specimens (10 cm × diameter 2 cm) were prepared from the slurry by a casting method. This was air-dried, installed in an electric furnace, heated to 300 ° C. and held for 1 hour as shown in the firing curve shown in FIG. 6, and further heated to reach the set temperature and maintained for 1 hour. It baked at each temperature for every 50 degreeC to 600 degreeC-1400 degreeC in the form to cool. As a result, the crucible shape of the fired body was sufficiently maintained up to 1400 ° C. as shown in FIG. In addition, the crucible fired at 1200 ° C. was heated to red with a burner and immediately dropped in water (room temperature), but there was no change.

  The average firing shrinkage ratio of the five fired bodies at each temperature of the rod-shaped specimen was 6% to 17.6% as shown in FIG.

  Further, the average value of the three-point bending strength at each temperature of the five rod-shaped specimens was as shown in the graph of FIG. Further, when the firing time was extended to 2 hours, the fired body strength at 700 ° C. was 20 Mpa, and the fired body strength at 800 ° C. was 35 Mpa.

  FIGS. 10 and 11 illustrate powder X-ray diffraction patterns of the 900 ° C. and 1200 ° C. fired bodies. Table 4 shows the crystal phases identified from the powder X-ray diffraction pattern of the fired body fired at each temperature.

From Table 4, if the reaction during calcination is estimated, dehydration of kaolinite and decomposition products such as metakaolin are generated at a temperature of 600 ° C. or lower, alumina hydroxide Al (OH) ₃ is decomposed, and porous Al ₂ O ₃ (Other than α-Al ₂ O ₃ ) is formed, and calcium carbonate decomposes before 800 ° C. Next, under the formation of porous CaO, an Al ₂ O ₃ —SiO ₂ -based SiO ₂ component of the decomposition product of kaolinite, and an alkali (water glass of a dispersant) of 3/1000% by weight or less, The reaction starts. It shows that a large amount of Ca ₂ Al ₂ SiO ₇ is produced at 850 ° C., and subsequently CaAl ₂ SiO ₈ is produced.
It can be presumed that the solid-phase sintering reaction proceeds as the temperature rises, and that the excess Al ₂ O ₃ component itself becomes α-Al ₂ O ₃ and at the same time CaAl ₁₂ O ₁₉ is produced by reaction with CaO.
In terms of the mixing ratio, if Al (OH) ₃ is decreased, the amount of α-Al ₂ O ₃ produced decreases, and crystal phases such as Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₁₂ O6 with a large amount of CaO component are present. It is assumed that crystal phases such as Ca ₃ Al ₂ Si ₃ O ₁₂ are precipitated if kaolinite clay is increased.

《Preparation, firing and evaluation of dolomite-based (dolomite standing) substrate》
A slurry prepared by adding 16% by weight of dolomite, 47% by weight of Al (OH) ₃ , 37% by weight of kaolinite clay and adding 3.0% by weight of water glass to 1000% of the total weight of the substrate. Was molded into the same rod-shaped test body as in Example 1 by a casting method. This was air-dried and then placed in an electric furnace and baked to 600 ° C. to 1400 ° C. in the same manner as in Example 1. As shown in FIG. 12, the firing shrinkage ratio of the fired body was 7.3% or less, which was smaller than the limestone base material.

  As a result, it is presumed that the precipitation control of the crystal phase is possible without forming a large amount of glass phase even in the fired body composed of the crystal phase containing the MgO component in the crystal phase containing the CaO component.

Al (OH) ₃ , Sakaime clay, and limestone were mixed at a ratio of 6 patterns 001 to 006 shown in Table 5 and molded into a rod-like test body similar to that of Example 1 by a mud casting method. This was air-dried, placed in an electric furnace, and fired at temperatures of 700 ° C., 900 ° C., and 1100 ° C. Table 6 shows the measurement results of the shrinkage rate and water absorption rate of each fired body and the results of the thermal shock test.

  From Table 6, as for the shrinkage rate, 001, 002, 005, 006 are all less than 10% at each temperature, and in particular, at 001,005, they are 8% or less at each temperature. With regard to 001,003,004,006, the performance may be lower than others depending on the firing temperature, but the formulation itself can be said to be a practical range.

As described above, according to the ceramic substrate of the present embodiment, even when a part of the three components is blended at 10% by weight, the firing shrinkage rate of the fired body is small, the firing width is wide, and the heat resistance is high. Various ceramics can be made industrially.
Further, according to the ceramic fired body of the present embodiment, good characteristics in bending strength and firing shrinkage can be obtained by using the ceramic substrate. In particular, a porous structural skeleton is formed by active porous Al ₂ O ₃ produced by decomposition at 500 ° C. or lower and metakaolinite, which is a decomposition product of kaolinite. Therefore, it has excellent thermal shock resistance and is useful in a wide range of industrial fields such as lightweight aggregates and filters. Incidentally, it was confirmed that a specific surface area of 30 m ² / g or more was obtained for the 900 ° C. fired body of each example. Thereby, it can be said that the fired body obtained in each example has a sufficient pore specific surface area as a ceramic filter.

It is a powder X-ray diffraction pattern of industrially drowned black mud, Kibushi, and Sasame clay. It is a powder X-ray diffraction pattern of an oriented sample of industrially watered black mud) and Kibushi clay. It is a baking shrinkage | contraction rate (%) curve of the clay laid industrially. Is a graph showing the industrially elutriation was kibushi clay, classification of the relationship between the molar ratio of SiO ₂ / Al ₂ O ₃ in the laboratory classification gairome clay. It is a graph which shows the relationship between the ignition loss, the thickness of a kaolinite crystal, the peak ratio of kaolinite and quartz and the specific surface area in powder X-ray diffraction. It is a graph which shows the baking curve of a limestone base. It is a schematic diagram of the sintered body at each temperature of a molded object (crucible) from a limestone base. It is a graph which shows the baking shrinkage rate of a limestone base. It is a graph which shows the bending strength of the sintered body of a limestone base. It is a powder X-ray diffraction pattern of the calcination body (900 ° C) of a limestone system base. It is a powder X-ray diffraction pattern of the calcination body (1200 ° C) of a limestone base. It is a graph which shows the baking shrinkage rate of a dolomite base.

Claims (4)

  It is composed of three components: a plastic clay from which feldspar and quartz containing alkali components are removed, lime and a bitter earth component, and an alumina component, and each component is at least 10% with respect to 100% of the total weight. A ceramic substrate containing at least%.   2. The ceramic substrate according to claim 1, wherein an alkaline sludge adjusting agent is added at 3/1000% by weight or less of the total weight of the substrate.   A ceramic fired body obtained by molding and drying the ceramic substrate according to claim 1 at a temperature selected within a range of 600 ° C to 1400 ° C, having a bending strength of approximately 20 Mpa or more and a firing shrinkage ratio. A ceramic fired body characterized by being about 18% or less. The crystalline phase, metakaolin, CaO, MgO, porous _{-Al 2 O 3, α-Al} 2 O 3, mullite _{Ca 3 Al 2 Si 3 O 12} , CaAl 2 Si 2 O 8, Ca 2 Al 2 SiO 7, The glass phase contains CaAl ₂ O ₄ , Ca ₁₂ Al ₁₄ O ₃₃ , Ca ₃ Al ₂ O ₆ , an alumina cement crystal and one or more crystals in which the MgO component is dissolved in the crystal, and a glass phase is present in a trace amount. The ceramic fired body described in 1.

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