KR100390171B1 - Manufacturing process of Low temperature firing Bone China - Google Patents

Abstract

The present invention relates to a method for producing bone ash, which reduces the content of bone ash, which is expensive and import-dependent, and lowers the firing temperature, and includes 32 to 37% by weight of bone ash, 22 to 27% by weight of feldspar and 22 to clay. Pulverizing and mixing the porcelain raw material including 27 wt% and 4-6 wt% of talc, followed by dehydration and kneading to form a porcelain product, and drying the molded article after baking at a temperature of 1180 to 1200 ° C. and then glazing. By providing a manufacturing method comprising the step of applying and firing, it is possible to reduce the firing temperature and improve the physical properties such as whiteness and thermal shock resistance as compared to the conventional bone ash magnetic, and to produce expensive bone ash magnetic products at low price. Because it can be price competitive.

Description

Manufacturing process of low temperature firing bone pottery {{Manufacturing process of Low temperature firing Bone China}

The present invention relates to a method for producing bone china, and more particularly, to a method for producing bone ash which is expensive and import-dependent, and reduces the firing temperature of bone ash.

Bone ash porcelain, the most advanced product of porcelain, which is generally an important part of the diet, is mixed with water using 45-50% by weight of bone ash, 25% by weight of clay, and 25% by weight of Cornish Stone. After grinding by using a ball mill (Ball Mill) and then using a filter press (Filter-Press) to remove the moisture in the form of a cake (Cake) to form a cylindrical base using a kneader (Pug-Mill). The substrate is cut to a diameter and height suitable for the size of each product, and then molded using a spinning machine (Jiggering Press), and the molded product is manufactured by firing in a tunnel kiln (Tunnel Kiln) of the maximum temperature of 1250 ℃.

Bone ash refers to a product made from powder by calcining cow bone at about 1000 ° C, and it acts as a strong flux because it reacts with cornish stone and clay in raw materials to make a low melting point compound, and increases whiteness and light transmittance of the body. Do it. In addition, Cornish Stone refers to Stone in southwestern England, and generally refers to feldspar. Feldspar is a mineral that accounts for more than 60% of igneous rock, and does not exist in pure composition. As a representative inorganic material that melts at a high temperature of 1140 to 1280 ° C and acts as a flux to lower the softening point of other materials, it is imported from the UK.

The above-described conventional bone pottery is based on the import of bone flakes and cornish stones, which are the main raw materials, and the bone flakes are extremely expensive raw materials, which not only occupy more than 75% of the total cost of raw materials but also have a high melting point. There is this.

The present invention has been proposed to solve the above problems of the prior art, the object of the present invention is to lower the firing temperature by lowering the content of bone ash as compared to the conventional bone ash magnetic as well as to improve product properties and reduce cost It is to provide a method for producing a bone pottery magnetic.

In order to achieve the above object, the present invention provides a ceramic raw material containing 32 to 37% by weight of bone ash, 22 to 27% by weight feldspar, 22 to 27% by weight clay, 4 to 6% by weight of talc. Low temperature firing comprising the steps of forming a ceramic product by pulverizing and mixing, followed by dehydration and kneading, and baking the molded product at a temperature of 1180 to 1200 ° C. and then applying a glaze to fire. Provided is a method for manufacturing bone bone magnetic.

The present invention can be obtained by reducing the cost of more than 20% by replacing the high-quality feldspar (potash feldspar), which contains 35% of bone ash compared to the conventional bone pottery and expensive flux with low cost.

Potash feldspar, which is used as a raw material for ceramics of the present invention, can be filled with domestic water. Generally, feldspar constitutes 60% of igneous rock, and is a representative flux of inorganic material industry. It is a raw material that is absolutely necessary to magnetize the base material because it can be used in base material or glaze to help melt other poorly soluble raw materials and lower the softening temperature of the combination. In addition, the high viscosity even after the softening point can maintain the shape for a long time.

Clay is an aggregate of fine particles of natural acid, and refers to plasticity when wet, rigidity when dry, and sintering when baked at a sufficiently high temperature. In addition, the mineral characteristics of clays having these properties are mainly composed of clay minerals composed of hydrous silicates of alumina. The clay gives the plasticity of the body better, imparting molding ability, increasing strength during drying and the ability to maintain its shape during firing.

Talc is a colorless or white mineral that is a mineral produced in the form of a soft mass or plate of fine crystals with a smooth touch. The fine powder of talc has very high viscosity when it is slipped, but there is little plasticity. In ordinary porcelain, talc improves light transmittance and chromaticity and is used in small amounts as a flux.

Hereinafter, the present invention will be described in detail with reference to the following Examples, but the present invention is not limited to the Examples.

Grinding and mixing the raw materials of porcelain blended with bone ash, feldspar, clay, and talc. When making porcelain substrates, the raw materials must first be ground. Grinding is coarsely ground using a jaw crusher and finely ground and mixed using a ball mill. A ball mill is a machine that puts balls and raw materials in a cylinder and rotates them to pulverize them. It is usually used to make ceramic clay. Wet water is mainly used for refining or grinding ceramic raw materials, so much water is used for ceramic production. Since the water used is natural water, it contains various salts. This affects the plasticity and dry strength of the clay, which can cause dry cracking in large materials, and especially the injection molding. Before proceeding, measure the pH of the slurry in storage as a slurry and adjust the pH to 10.5-11.5. At this time, the pH is adjusted by adding hydrochloric acid or sodium silicate to adjust the pH. The average size of the raw material particles after grinding is about 5-6 탆.

The preferred content range of bone ash is 32 to 37% by weight, and when bone ash is prescribed at less than 32% by weight, the content of calcium triphosphate, which defines bone ash, is lowered to 30% or less. The preferred content range of feldspar is 22 to 27% by weight, and less than 22% by weight leads to an increase in the sintering temperature resulting in an increase in the sintering temperature. When it exceeds 27% by weight, the product collapses and crushes during sintering. The phenomenon occurs. It also becomes a factor of lowering the whiteness of the product. The preferred content range of clay is 22 to 27% by weight, and less than 22% by weight of the product lowers the molding strength, so that the product cannot be molded or shaped, and the strength of the product is significantly lowered, which causes easy breakage. . In addition, when the content of clay exceeds 27% by weight, the firing temperature is increased and the whiteness is lowered. The preferred content of talc is 4 to 6% by weight. If the product is less than 4% by weight, the firing temperature of the product increases, and if it exceeds 6% by weight, the product collapses and becomes distorted during sintering and the whiteness of the product decreases. It becomes a factor.

Next, a filter pressing step using a filter press is usually performed when grinding, so a process of dehydrating water is required. After filtration, the water content is about 18-22%. A filter press is a type of filtration device that removes water by applying pressure continuously by putting two sheets in between the filter cloths.

Next, as a step of kneading, in the case of dehydration with a filter press to make a cake, or when mixing dry raw materials into clay to which water is added, complete uniformity is insufficient and air is contained. You have to knead it accordingly. In plastic clay, these operations are generally performed using a pug mill, and in some cases kneading by hand. Vacuum extruder is one of the extruders and extrudes by removing the air of the clay by making the middle part in a vacuum state when extruded. The topsoil is made in a relaxed state for shaping (about 1.7 to 1.9 in specific gravity), or in various cylindrical diameters of different diameters for jiggering.

As a step of forming the porcelain base, the raw material powder should be filled as uniformly as possible. In other words, even if any part of the base is taken, the moisture content, chemical composition, bubble amount, or arrangement state of the particles is as uniform as possible. Any part of the molded body shall have the same packing density.

The molding method of ceramics is the spinning wheel molding and injection molding, and the spinning wheel (jiggering) is a method of forming a wheel by using a clay obtained from a vacuum grinder. In particular, the industrially used is a mechanical wheel molding, which is the most widely used method for the manufacture of tableware and containers by placing the clay on the plaster frame and rotating the spinning wheel to form between the plaster frame and the metal head. This method is a manual method other than the use of a mechanical wheel. In recent years, an automatic mechanical wheel method has been adopted that mechanizes the entire process by automating the operation from clay to complete molding.

In addition, in the injection molding, when the water is added to the clay, the clay absorbs the water and becomes moist, and when the water is continuously added, the clay becomes a soft soil that can be kneaded by hand. When more water is added, it is more fluid and can be easily transferred to another container just by tilting the container. When more water is added, the finer particles exhibit a suspended state and have a liquid-like property. When the powder exhibits such fluidity, not limited to clay, it is called Yijang, and the preparation prepared for molding is called Yijang Yi. The injection molding flows into the plaster mold to make a plaster mold-shaped product. At this time, the specific gravity of this sheet becomes important. When water is used only, the specific gravity is lowered, so that molding takes a long time and the shrinkage is severe.

Next, as a drying step, if the firing process is performed without drying the molded product, cracks and bursts occur in the product due to expansion of moisture during firing. Therefore, the molded part is dried before firing, but if it is dried too fast, cracks and torsion may occur in the product, so it is dried naturally.

As the final firing step, firing can be broadly divided as follows. That is, biscuit fire, gloss fire, and decoration fire.

Biscuit firing is called the first bulb, and it is mainly used in the manufacture of porcelain. It is baked at 1180 ~ 1200 ℃ for easy and safe handling such as painting or glazing on the base material. It is a firing aimed at producing a product by having a mechanical strength and then glazing with a low melting point and then baking at a low temperature.

Gloss firing is a glaze ball that is coated with biscuit firing and has a low melting point glaze to be baked at a relatively low temperature to give gloss. In general, the glaze roasting temperature is generally about 100 ℃ lower than the biscuit firing temperature.

Decoration firing is a baking in which the pigment is baked to decorate a gloss roasted product or transferred to a transfer paper, and then calcined at low temperature in an electric furnace to fuse the pigment. The temperature of this roast is usually 700 to 900 ° C.

Table 1 shows the physical properties of bone bone magnetic (Example 1) according to the present invention and the physical properties of conventional bone magnetic (Comparative Example 1).

Comparative Example 1 Example 1 Raw material Bones 45% Cornish Stone (CF-11) 25% P- Clay 12.5% G- Clay 12.5% Ball Clay 2.5% Bentonite 0.5% Ash 36% feldspar 25% clay 35% talcum 4% Dry shrinkage (%) 3 2.7 ± 0.3 Molding strength (㎏ / ㎠) 28.4 ± 1.2 27.7 ± 2.8 Plastic shrinkage (%) 9.8 ± 0.1 9.2 ± 0.3 Plastic strength (㎏ / ㎠) 1319.0 ± 11.0 1258.0 ± 58 Whiteness (100 [pure white] standard) 86.5 90.5 Thermal expansion coefficient (/ ℃) 8.4 × 10 ^-6 7.5 × 10 ^-6 Crack resistance (difference in temperature quenching) 130 ℃ difference 170 ℃ difference Autoclave 12 atmospheres-1 hour pass pass Sintering Temperature (Maximum Temperature) 1240 ± 10 ℃ 1190 ± 10 ℃

From the results of Table 1, it can be seen that the molding strengths of Example 1 and Comparative Example 1 are equivalent. If the molding strength is weak, there is a high risk of damage to the product during the transfer and shaping. In addition, the plastic strength, which greatly affects the strength of the finished product, is on par with existing products.

The whiteness, which can be said to determine the quality of the bone magnetic product, shows that the whiteness of Example 1 is superior to that of Comparative Example 1.

The thermal shock resistance can be evaluated by the crack resistance. The important factors of the thermal shock resistance are the coefficient of thermal expansion and the thickness of the substrate. In other words, the coefficient of thermal expansion is the most important factor when the thickness of the substrate is constant. In Example 1, the thermal expansion coefficient is about 1.0 ± 10 ⁻⁶ / ° C. lower than that of Comparative Example 1, but the smaller the thermal expansion coefficient, the higher the thermal shock resistance. The thermal shock resistance of bone ceramics according to the present invention shows an increase in the thermal shock resistance of 30 ~ 60 ℃ than conventional bone ceramics, which is sufficient to compensate for the breakage of the product by increasing the temperature difference when containing hot or hot materials It can be said.

Therefore, according to the present invention, by optimizing the chemical composition, the sintering temperature and the atmosphere, the whiteness, light transmittance, and strength, which are the characteristics of the conventional bone ash magnetic products, can be improved or the same. By lowering the sintering temperature by 50 to 100 ° C., the production cost can be reduced by reducing fuel consumption and extending the life of various refractory materials during the firing process. In addition, by reducing the content of bone ash having a high coefficient of thermal expansion lower the thermal expansion coefficient than conventional bone magnetic products can improve the thermal shock resistance of the defects of bone ceramic products.

As described above, according to the present invention, by reducing the content of expensive bone ash used in conventional bone magnetic products and replacing porcelain raw materials such as cornish stone with high quality and low cost feldspar, the firing temperature is reduced and product properties are improved. In addition to being able to produce expensive bone ash products at low prices, it can be price competitive.

Claims (1)

In the manufacture of bone pottery, ceramic raw materials including 32 to 37% by weight of bone ash, 22 to 27% by weight of feldspar, 22 to 27% by weight of clay, and 4 to 6% by weight of talc are pulverized and mixed, followed by dehydration and kneading. Forming a product, and after drying the molded product and calcined at a temperature of 1180 ~ 1200 ℃ and then applying a glaze to the firing method comprising the step of baking.