JP5845500B2 - Heat resistant product and manufacturing method thereof - Google Patents

Description

The present invention relates to a heat-resistant product and a method for producing the same, and more particularly to a heat-resistant product that is white and has no water absorption and requires white thermal shock resistance and a method for producing the same.

Conventionally, a material mainly composed of cordierite is known to have excellent thermal shock resistance due to a small coefficient of thermal expansion. For this reason, various materials have been reported. For example, in Japanese Patent No. 599661 (Patent Document 1), talc, alumina, kaolin, low thermal expansion ceramics is disclosed that for the additional inclusion of Li-containing material in advance in the matrix of from 0.12 to 1.0% equivalent weight as Li ₂ O ing. Japanese Unexamined Patent Publication No. 2003-238238 (Patent Document 2) discloses a low thermal expansion porcelain obtained by mixing and firing synthetic cordierite, talc, kaolin, and alumina. Further, as an electronic material, Japanese Patent Application No. 2003-542108 (Patent Document 3) discloses an electronic circuit board using a glass ceramic composition comprising an inorganic powder such as alumina or cordierite and a glass powder.

Japanese Patent No. 5996661 JP 2003-238238 A Japanese Patent Application No. 2003-542108

However, regarding Patent Document 1, when Li-based soot is applied to a cordierite base material, depending on the raw material composition of the base material, a low thermal expansion crystal is not generated on the glaze surface in contact with the base material and cracks are generated. The problem occurs. In addition, when calcining a material mainly composed of cordierite, depending on the raw material composition of the substrate, a large amount of low-viscosity glass phase is generated, and the deformation at the time of firing increases. Or, conversely, depending on the raw material composition, a low-viscosity glass phase is hardly generated, and it is necessary to calcinate at a high temperature exceeding 1300 ° C. to make it porcelain, or it becomes porous without becoming porcelain. There was a problem.

Regarding Patent Document 2, synthetic cordierite in which talc, kaolin, and alumina are mixed and fired in advance is used as part of the raw material. It has been known that a process for the synthesis is required, and that the synthetic cordierite powder has a small firing temperature range for densification during sintering. Therefore, when synthetic cordierite powder is used as a raw material, it will not be densified if the firing temperature is slightly low, and conversely, if it becomes slightly high, a large amount of glass phase will be generated at once, deformation during firing, There arises a problem that the surface portion is highly expanded. Further, Patent Document 3 is a composition of glass and inorganic powder, which is different from the ceramic sintered body having the base layer and the glaze layer of the present invention.

Therefore, in porcelain tableware using conventional cordierite, and further in porcelain tableware using cordierite and glazed with Li, glaze is small, dense, and crack-free. It was very difficult to produce a body with a high yield and stability. Therefore, if it is only cordierite substrate, it is used as industrial parts, etc., but no porcelain heat-resistant products with glaze applied to cordierite substrate are currently manufactured and sold. Limited to those of easy petalite quality.

Accordingly, the present invention provides a cordierite-type heat-resistant product having low thermal expansion and excellent thermal shock resistance and having no thermal absorption, which is composed of a base layer and a glaze layer, in particular, white, thermal shock-resistant porcelain tableware. It is an object of the present invention to provide a method for stably producing a low thermal expansion porcelain having no cracks and excellent thermal shock resistance even when a Li-based glaze is applied.

The present invention was created to solve the above problems. First, a ceramic sintered body having a base layer and a glaze layer, the base layer comprising a cordierite base. The glaze layer is characterized in that crystals with low expansion are formed. Thus, a ceramic sintered body having high thermal shock resistance can be obtained by applying a glaze layer in which crystals having low thermal expansion are stably formed on a cordierite substrate. The Second, the lithium element to the substrate layer, by that it contains 1.1 wt% to 2.8 wt% of Na ₂ O + K ₂ O, and characterized in that porcelain of the firing 1200 to 1300 ° C. To do. Thus, both the lithium element contained in the substrate and the alkali component of Na ₂ O + K ₂ O greatly affect the porcelainization of the substrate. Especially when Na ₂ O + K ₂ O having a large content is less than 1.1% by weight, it does not become porcelain. On the other hand, when Na ₂ O + K ₂ O exceeds 2.8% by weight, it becomes porcelain, but Na ₂ O and K ₂ O inhibit the precipitation of low thermal expansion crystals in the soot, so that the glaze is not reduced and cracking occurs. Occur. Furthermore, a large amount of low-viscosity glass phase is produced, so that deformation during firing increases. Thus, the novelty of the present invention is that it has been found that it is important that the amount of Na2O + K2O is within an appropriate range together with the lithium element in the substrate in order to stably produce porcelain without cracking. is there. Thirdly, the cordierite substrate is produced by mainly reacting talc, kaolin and alumina, which are blended as raw materials. Unlike synthetic cordierite, cordierite is produced while talc, kaolin and alumina react during firing, so that a stable ceramic sintered body can be obtained with a wide firing temperature range. Fourth, the glaze layer is characterized by containing a low expansion crystal which is considered to be a lithium aluminosilicate. When the glaze layer contains a low-expansion crystal that is considered to be a lithium aluminosilicate, a low-thermal-expansion glaze that matches the thermal expansion of cordierite, which is the base material, can be obtained. Fifth, a lithium element-containing material, which is a raw material containing lithium element, is blended as a raw material for the base layer and a raw material for the glaze layer, and Na ₂ O + K ₂ O is contained in the base layer in an amount of 1.1 wt% to The inclusion of 2.8% by weight stabilizes the low expansion crystal in the glaze layer due to the action of lithium element in the lithium element-containing material and Na ₂ O and K ₂ O during firing at 1200 ° C to 1300 ° C. It is characterized by being generated. Raw material for the substrate layers and, by the action of lithium element-containing material which is blended as a raw material of the glaze layer, the low expansion of crystal is produced glaze layer, when this time Na ₂ O + K ₂ O content exceeds 2.8 wt% Although the substrate becomes porcelain, Na ₂ O and K ₂ O are thought to inhibit the precipitation of low thermal expansion crystals in the soot, and the glaze is not reduced and cracks occur. On the contrary, if the amount of Na ₂ O + K ₂ O is less than 1.1% by weight, the substrate is not sufficiently porcelain, and only a sintered body having water absorption can be obtained. On the other hand, if the amount of Na ₂ O + K ₂ O is 1.1% to 2.8% by weight, a substrate having no water absorption is obtained, and a low-expansion crystal is sufficiently formed in the glaze layer, and there is no crack. It becomes a sintered body. Sixth, the thermal expansion coefficient of the base layer is 3.8 × 10 ⁻⁶ or less. Raw materials such as talc, kaolin, and alumina react during firing to produce cordierite, thereby obtaining a substrate having a thermal expansion coefficient of 3.8 × 10 ⁻⁶ or less. However, when K ₂ O + Na ₂ O exceeds 2.8 in terms of weight%, thermal expansion increases, and cracking occurs due to inhibition of precipitation of low thermal expansion crystals in the soot.

By adopting the above configuration, it is possible to stably produce unprecedented high-temperature-resistant porcelain heat-resistant products by applying a glaze layer with low thermal expansion crystals formed on the cordierite substrate. It becomes. Since the heat-resistant product of the present invention is a product having a thermal expansion coefficient of 3.8 × 10 ⁻⁶ or less, it has a high thermal shock that can withstand a temperature difference of 280 ° C. Therefore, it can be used for microwave ovens as well as microwave ovens. Moreover, by using talc, which is relatively inexpensive, as the main raw material instead of petalite, which has a high raw material price, not only a low thermal expansion porcelain with reduced raw material costs can be obtained, but also by adjusting the raw material composition of the base 1200 In a wide range of firing temperatures from as low as 1 ° C. to 1300 ° C., a porcelain heat-resistant product having no water absorption can be obtained. Furthermore, since the petalite-type thermal shock resistant tableware has water absorbency, water including food is absorbed and accumulated every time it is used, and remains as a stain. For this reason, only tableware with black or brown glaze can be produced so that the stains are not noticeable. In contrast, the product of the present invention is characterized by low thermal expansion and excellent thermal shock resistance, as well as a porcelain product having no water absorption, which is not present in current heat-resistant products. For this reason, white porcelain dishes that are similar to general tableware, or white porcelain with a background, which could not be made with conventional heat resistant products, can be commercialized as heat resistant products. In other words, it can be used in any of a freezer, an oven, a steam oven, and a microwave oven in a state where the cooked food is served. It can be stored and heated in a steam oven or microwave oven before meals and served directly on the table.

It is a figure which shows the X-ray-diffraction result in the base sintered compact of the Example which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to Tables 1 to 3 and FIG.

First, the raw material used for the substrate layer, and kaolin, talc, alumina, feldspar and, petalite powder was each chemical _{analysis, SiO 2, Al 2 O 3} , MgO, CaO, K 2 O, Na 2 O, Li 2 Measure the amount of O. From each measurement result, after blending calculation is performed , the raw materials are weighed and mixed in a predetermined ratio. At this time, the composition is calculated and weighed so that the composition after sintering contains lithium element and Na ₂ O + K ₂ O is contained in an amount of 1.1 wt% to 2.8 wt%. At this time, when lithium element is contained in the substrate, low expansion crystals are precipitated in the glaze layer during firing. The amount of lithium may be 0.12% by weight to 1.0% by weight, but more preferably 0.3% by weight to 0.8% by weight, as Li ₂ O by blending calculation . However, even in the case of containing lithium element in this way, it is necessary to obtain a sintered body without cracks because it is porcelain that Na ₂ O + K ₂ O is contained in 1.1% to 2.8% by weight in the compounding calculation. It becomes a condition. When Na ₂ O + K ₂ O is less than 1.1% by weight, the substrate cannot be sufficiently melted, and only a porous sintered body having water absorption can be obtained. On the other hand, when Na ₂ O + K ₂ O exceeds 2.8% by weight, the substrate is obtained with no water absorption, but in the glaze layer, it is thought to inhibit the formation of low expansion crystals, and cracks occur after firing. End up. A more preferable amount of Na ₂ O + K ₂ O in the blending calculation is 1.5% by weight to 2.5% by weight.

By such blending calculation, blending of A-1 to A-3 shown in Table 1 was performed.
In other words, A-1 contains 8.5% by weight of kaolin, 39.6% by weight of talc, 17.1% by weight of alumina, 25.7% by weight of feldspar, and 9.1% by weight of petalite. And finely pulverize until the average particle size is 5 μm or less. Similarly, A-2 contains 16.5% by weight of kaolin, 39.6% by weight of talc, 17.1% by weight of alumina, 17.7% by weight of feldspar, and 9.1% by weight of petalite. And finely pulverize until the average particle size is 5 μm or less. Similarly, A-3 contains 28.5 wt% kaolin, 39.6 wt% talc, 17.1 wt% alumina, 5.7 wt% feldspar, and 9.1 wt% petalite. And finely pulverize until the average particle size is 5 μm or less. At this time, if the raw material is not sufficiently pulverized and the average particle diameter exceeds 5 μm, sintering does not proceed and only a sintered body having water absorption can be obtained. On the other hand, when pulverized until the average particle size becomes 5 μm or less, talc, kaolin, and alumina sufficiently react during firing, so that cordierite is generated and a dense ceramic sintered body is obtained.

The composition of the green body sintered bodies of A-1 to A-3 are all SiO ₂ : 50 to 55, Al ₂ O ₃ : 25 to 35, MgO: 10 to 15, CaO: 0 to ₂ by weight%. , K ₂ O + Na ₂ O: 1.1 to 2.8, Li ₂ O: 0.12 to 1.0. After pulverization by the ball mill, the dehydration process is performed by a filter press in the same manner as a normal method for producing ceramic products, and the columnar raw material is processed by a vacuum kneader. Using this raw material, a test body having a size of 10 mm × 70 mm × 4 mm is formed by casting, and unbaked at 900 ° C. in an electric furnace. A comparison was made by placing the unbaked sample on a refractory brick with a groove having an inclination of 60 ° and measuring the angle (curvature) curved by firing. The water absorption was measured by the Archimedes method after cutting out the sintered body. Further, for thermal expansion measurement, a round bar having a diameter of 5 mm and a length of 20 mm was cut out from the sintered body, measured from room temperature to 950 ° C., and a thermal expansion coefficient at 700 ° C. was calculated. For comparison, a similar sample was prepared for ordinary porcelain using Amakusa porcelain clay, and the above measurement was performed. The measurement results are shown in Table 2.

All of A-1 to A-3 are dense porcelain sintered bodies having a water absorption rate of 0.1% or less. This is due to the fact that Na ₂ O + K ₂ O, which is necessary for densification by promoting sintering, is a sufficient raw material blend, and that the raw material is finely pulverized to an average particle size of 5 μm or less. Is sufficiently reacted without remaining unreacted. It can also be seen that the value of the degree of curvature, which indicates the ease of deformation by firing, is smaller than the ordinary porcelain used for comparison and is not easily deformed. In other words, the amount of Na ₂ O and K ₂ O necessary for densification is promoted, so that an excessive glass layer that tends to soften more than necessary is not generated, and the degree of curvature does not become too high. . Furthermore, a sintered body having a low thermal expansion coefficient of 3.8 × 10 ⁻⁶ or less can be obtained by sufficiently reacting kaolin, talc and alumina to produce cordierite. Here, the result of having partially pulverized the sintered body of A-2 and identifying the crystal phase using an X-ray diffractometer is shown in FIG. From FIG. 1, it was confirmed that the substrate was cordierite.

Next, in order to confirm the compatibility with the glaze, the base material of A-1 to A-3 and the same pulverization treatment as a comparative example, the base having an Na ₂ O + K ₂ O amount of 3.0% by weight Using the raw material, a dish-shaped test specimen was molded by mechanical rocking. After drying, baking is performed at 900 ° C., and in mol%, SiO ₂ : 75 to 80, Al ₂ O ₃ : 8 to 11, MgO: 0 to 7, CaO: 1 to 5, K ₂ O: 0 to 2, After applying a glaze composed of Na ₂ O: 0 to 1, Li ₂ O: 0 to 8, it was fired at 1250 ° C. If the composition of the base is within the range of the present invention, a low-expansion crystal which is considered to be a lithium aluminosilicate system is stably formed in the soot by firing. The sintered body after firing is designated as S-1 to S-3, and the presence or absence of cracks is shown in Table 3.

In the dish-shaped sintered bodies S-1 to S-3 composed of the base layer and the glaze layer, sintered bodies without cracks were obtained. However, in the composition of the substrate, the amount of Na ₂ O + K ₂ O exceeds 2.8% by weight, and in the case of 3.0% by weight, cracking occurs because Na ₂ O + K ₂ O inhibits the formation of low expansion crystals in the glaze layer Was confirmed. On the contrary, if the amount of Na ₂ O + K ₂ O is decreased and the amount is less than 1.1% by weight, the substrate is not sufficiently sintered, and only a sintered body having water absorption can be obtained. In other words, if the amount of Na ₂ O + K ₂ O is 1.1 wt% to 2.8 wt%, a substrate having no water absorption can be obtained, and a low expansion crystal can be stably formed in the glaze layer, and there is no cracking. A knot is obtained. As described above, according to the present invention, a cordierite porcelain product having a low thermal expansion, which has been difficult to produce a ceramic sintered body having no water absorption and having no cracks with a high yield, has been obtained. It becomes possible to manufacture stably. For this reason, the current mainstream price of raw materials is high, but instead of petalite-type thermal shock-resistant tableware that is easy to manufacture and has good yield, the production of cordierite-type thermal shock-resistant tableware with low raw material prices is the mainstream. It is thought to become. In addition, since the petalitic thermal shock resistant tableware absorbs water, it absorbs and accumulates water containing food every time it is used, and remains as a stain. For this reason, only tableware with black or brown glaze can be produced so that the stains are not noticeable. On the other hand, since the product of the present invention is a porcelain product with low thermal expansion, excellent thermal shock resistance and no water absorption, white porcelain tableware or white porcelain with a sketch can be commercialized.

Therefore, in the case of the conventional petalite product, after heating the food on it, it was transferred to white general tableware and used for the table, but it is possible to save the trouble of the transfer. In other words, it can be used in any of a freezer, an oven, a steam oven, and a microwave oven in a state where the cooked food is served. It can be stored and heated in a steam oven or microwave oven before meals and served directly on the table. Further, after the meal, the sintered body can be washed with an automatic washing machine and dried with a hot air drier. In addition, although the said sintered compact was demonstrated as being tableware which exhibits a dish shape, the tableware which exhibits shapes other than a dish shape may be sufficient, and also heating cookers other than tableware may be sufficient. In addition, regarding the raw material, the raw material of the base layer and the raw material of the glaze layer have been described using petalite as a raw material having a lithium element. .

The low thermal expansion porcelain obtained by the present invention has a possibility of being used for various purposes other than tableware. For example, it can be sufficiently used as a microwave oven, a steam oven, a gas oven tray, an oven toaster tray, or the like that is currently made of metal. Furthermore, there is a possibility that it can be used for an inner pot for a rice cooker or a diaper for storing cooked rice.

C Cordierite

Claims (2)

In a heat-resistant product having a base layer and a glaze layer, the base layer is composed of cordierite-like porcelain, and the composition of the cordierite is equivalent to 0.12% by weight to 1.0% by weight as Li ₂ O in the blending calculation. resistant products and lithium element comprises Na ₂ O + K ₂ O of 1.1 wt% to 2.8 wt%, the glaze layer is characterized by comprising a low-expansion crystallized is formed. As a raw material for the base layer and the glaze layer, a lithium element-containing material, which is a raw material having lithium element, is blended, and the average particle size of the base layer raw material is pulverized to 5 μm or less and fired at 1200 ° C. to 1280 ° C. The method for producing a heat-resistant product according to claim 1, wherein the heat-resistant product is made porcelain.