POTTERY GREENWARE MATERIAL

Abstract

Disclosed is a pottery greenware material by which a pottery having both productivity and quality can be produced with a high degree of freedom depending on an intended use thereof. The pottery greenware material includes a first greenware material and a second greenware material; both the first greenware material and the second greenware material including, as chemical species, SiO.sub.2, Al.sub.2O.sub.3, and either one or both of K.sub.2O and Na.sub.2O; and an average particle diameter (D2) of the second greenware material being smaller than an average particle diameter (D1) of the first greenware material.

Claims

1. A pottery greenware material comprising a first greenware material and a second greenware material, wherein both the first greenware material and the second greenware material comprise, as chemical species, SiO.sub.2, Al.sub.2O.sub.3, and either one or both of K.sub.2O and Na.sub.2O; and an average particle diameter (D2) of the second greenware material is smaller than an average particle diameter (D1) of the first greenware material.

2. The pottery greenware material according to claim 1, wherein the first greenware material comprises materials derived from pottery stone as a skeleton material, and the second greenware material comprises materials derived from silica stone and a-alumina as a skeleton material.

3. The pottery greenware material according to claim 1, wherein the first greenware material comprises materials derived from a stone-based raw material as a main component, and the second greenware material comprises a material derived from a powdered raw material as a main component.

4. The pottery greenware material according to claim 1, wherein the first greenware material comprises a mixture obtained by grinding a first greenware raw material, and the second greenware material comprises a mixture obtained by stirring a second greenware raw material.

5. The pottery greenware material according to claim 4, wherein the first greenware raw material comprises pottery stone, clay (powder), and feldspar as main components, and the second greenware raw material comprises silica stone (powder), a-alumina (powder), clay (powder), and feldspar (powder) as main components.

6. The pottery greenware material according to claim 1, wherein a deformation quantity by firing is in the range of 4 mm to 13 mm.

7. The pottery greenware material according to claim 1, wherein a firing shrinkage rate by firing is in the range of 2.5 to 7.0%.

8. The pottery greenware material according to claim 1, wherein a coefficient of water absorption rate is in the range of 4 to 10%.

9. A method for producing a pottery greenware material, comprising the steps of: mixing a first greenware raw material to prepare a first greenware material having a first average particle diameter (D1.sub.0), mixing a second greenware raw material to prepare a second greenware material having a second average particle diameter (D2.sub.0), and mixing the first greenware material with the second greenware material; wherein both the first greenware material and the second greenware material comprise, as chemical species, SiO.sub.2, Al.sub.2O.sub.3, and either one or both of K.sub.2O and Na.sub.2O, and after the first greenware material and the second greenware material are mixed, an average particle diameter (D2) of the second greenware material is smaller than an average particle diameter (D1) of the first greenware material.

10. The method according to claim 9, wherein the first greenware raw material comprises pottery stone, and the second greenware raw material comprises silica stone and a-alumina.

11. The method according to claim 9, wherein the first greenware raw material comprises a stone-based raw material as a main component, and the second greenware raw material comprises a powdered raw material as a main component.

12. The method according to claim 9, wherein the first greenware raw material comprises pottery stone, clay (powder), and feldspar as main components, and the second greenware raw material comprises silica stone (powder), a-alumina (powder), clay (powder), and feldspar (powder) as main components.

13. The method according to claim 9, wherein the first greenware raw materials are mixed by a grinding/mixing method to prepare the first greenware material, and the second greenware raw materials are mixed by a stirring/mixing method to prepare the second greenware material.

Description

EXAMPLES

[0086] The present invention will be specifically described on the basis of the Examples described below, but the scope of the present invention is not at all limited to these Examples.

[0087] Preparation of First Greenware Material

[0088] About 48% by weight of sericite pottery stone and kaolin pottery stone which are the skeleton-forming materials, about 35% by weight of China clay (powder) and ball clay (powder) which are the plasticizing materials, about 15% by weight of feldspar which is the main sintering assisting agent, and about 2% by weight of dolomite, as well as appropriate amounts of water and of sodium silicate which is the deflocculant were altogether put into a ball mill, and were subjected to wet grinding so that the particle size of particles grinded in a greenware slurry obtained, which is measured with a laser diffraction particle size distribution analyzer, is characterized in that the percentage of particles having the particle diameter of 10 μm or less is about 58% and that the median particle diameter (D50) is about 8.0 μm, to obtain the first greenware material.

[0089] Preparation of Second Greenware Material

[0090] About 64% by weight of silica stone and a-alumina which are the skeleton-forming materials, about 32% by weight of China clay (powder) and ball clay (powder) which are the plasticizing materials, and about 4% by weight of feldspar which is the sintering assisting agent, as well as appropriate amounts of water and of sodium silicate which is the deflocculant were altogether put into Eirich Intensive Mixer (manufactured by Maschinenfabrik Gustav Eirich GmbH & Co KG), and were subjected to mixing with stirring so that the particle size of particles stirred in a greenware slurry obtained, which is measured with a laser diffraction particle size distribution analyzer, is characterized in that the percentage of particles having the particle diameter of 10 μm or less is about 75% and that the median particle diameter (D50) is about 5.0 μm, to obtain the second greenware material.

[0091] Preparation of Pottery Greenware Material

[0092] The first greenware material and the second greenware material were mixed with each other at the mixing ratio as shown in Table 4 to obtain four kinds of pottery greenware materials. The mixing was carried out by the stirring/mixing method.

[0093] Preparation of Molded Body

[0094] The pottery greenware materials thus obtained were molded by a slurry-cast molding method using a gypsum mold to obtain molded bodies.

[0095] Preparation of Fired Body

[0096] The molded bodies thus obtained were fired in an electric furnace to obtain fired bodies. The maximum temperature in the heat curve was about 1200° C. The fired bodies thus obtained were evaluated as follows.

[0097] The chemical composition of all components in the entirety of the respective pottery greenware materials fired; as well as the chemical composition of the vitreous phases and of the crystal phases in the pottery greenware materials fired were as shown in Table 4.

[0098] Evaluation

[0099] Properties of the four kinds of pottery greenware materials were measured as described below. The results thereof were shown in Table 4.

[0100] Water Absorption Percentage

[0101] The water absorption percentages were measured on the basis of JIS A1509-3. The fired body samples of the greenware materials were dried at 110° C. for 24 hours, and then were cooled, and thereafter, the mass W1 of the respective samples were measured. Next, the samples were soaked in water in a desiccator, and then were kept under a vacuum state for 1 hour so as to forcibly saturate the open pores thereof with water; then, the mass W2 of the respective samples at this time were measured. The water absorption percentages were obtained by the following equation.

Water absorption percentage=(W2-W1)/W1×100 (%)

[0102] Deformation Quantity by Firing

[0103] The deformation quantity by firing was obtained as follows. The unfired specimens each having the width of 30 mm, the thickness of 15 mm, and the length of 260 mm were supported with the span of 200 mm during the period of firing, then, the deflection quantity and the thickness of the specimens after firing were measured. Because the deflection quantity is inversely proportional to the square of the thickness of the specimen after firing, the deflection quantity in terms of the converted value to the thickness of 10 mm was obtained from the following equation as the deformation quantity by firing.

[0104] Deformation quantity by firing=(the value of the deflection quantity measured) x (the thickness of the specimen after firing).sup.2/10.sup.2

[0105] Shrinkage Percentage by Firing

[0106] The shrinkage percentage by firing was defined by the shrinkage percentage by firing of the fired body test pieces of the greenware materials in a longitudinal direction, wherein the fired body test pieces having the width of 25 mm, the thickness of 5 mm, and the length of 230 mm were heated up to the temperature of 1000° C. in 4 hours, and were further heated up to 1200° C. in 2 hours, and were further kept at 1200° C. for 1 hour; and thereafter, the resulting test pieces were naturally cooled down to room temperature.

[0107] Strength

[0108] The strength was measured as follows. the fired body test pieces of the greenware materials having the size of 11)13×130 mm were provided, and the 3-point bending test was carried out to the test pieces under the condition of the span of 100 mm and the crosshead speed of 2.5 mm/min with an autograph.

[0109] Thermal Shock Resistance (Resistance to Quick Cooling)

[0110] The thermal shock resistance was evaluated as follows: the fired body test pieces having the width of 25 x thickness of 10 x length of 110 mm were kept at a given temperature for 30 minutes or longer, and then were quickly cooled by throwing into water to check whether a crack was generated or not. Then, the quick cooling temperature was raised by 10° C. repeatedly; then, the maximum difference between the initial temperature and the temperature at which a crack was generated was evaluated as the thermal shock resistance.

[0111] Thermal Expansion

[0112] The thermal expansion was evaluated by measuring the coefficient of linear thermal expansion of the fired body test pieces having the diameter of 5 mm and the length of 20 mm, by a compressive load method and under the measurement temperature of 50 to 600° C., using a differential expansion measurement instrument.

[0113] Crazing Resistance

[0114] The samples were prepared by applying a Bristol glaze, which is generally used for the sanitary ware, to the greenware material with a spraying method, followed by firing the resulting products. Next, penetration test was conducted using an autoclave in accordance with JIS A 5207; then, the fired body samples were soaked in red ink to evaluate the occurrence of the penetration by visual inspection.

TABLE-US-00004 TABLE 4 Pottery greenware material according to the present invention (Mixture of first greenware material and second greenware material) Second Second Second Second Second greenware greenware:First greenware:First greenware:First greenware:First First greenware material greenware greenware greenware greenware material (stirring/mixing) 80:20 70:30 60:40 50:50 (grinding/mixing) Composition of L.O.I 0.4 0.4 0.4 0.4 0.4 0.4 all components SiO2 26.5 34.9 39.1 43.3 47.5 68.9 in the entirety Al2O3 70.7 61.3 56.7 52.1 47.6 24.1 of fired greenware TiO2 0.4 0.3 0.3 0.3 0.3 0.2 (% by weight) Fe2O3 0.4 0.5 0.5 0.6 0.6 0.8 CaO 0.1 0.3 0.4 0.5 0.6 1.2 MgO 0.1 0.3 0.3 0.3 0.3 0.6 K2O 1.2 1.4 1.5 1.6 1.8 2.4 Na2O 0.4 0.6 0.7 0.8 0.8 1.3 Li2O 0.0 0.0 0.0 0.0 0.0 0.0 B2O3 0.0 0.0 0.0 0.0 0.0 0.0 BaO 0.0 0.0 0.0 0.0 0.0 0.0 TOTAL 100 100 100 100 100 100 Vitreous phase (% by weight) 30 38 42 46 49 67 Crystal phase (% by weight) 70 62 53 54 51 33 Composition of SiO2 55.0 60.2 61.6 63.4 65.7 73.0 all components Al2O3 35.5 29.8 28.4 26.5 24.3 16.5 in vitreous phase TiO2 1.2 0.9 0.8 0.7 0.6 0.4 (% by weight) Fe2O3 1.2 1.3 1.2 1.2 1.2 1.3 CaO 0.3 0.8 1.0 1.2 1.3 1.8 MgO 0.2 0.7 0.8 0.8 0.7 0.9 K2O 3.9 3.6 3.6 3.6 3.6 3.6 Na2O 1.2 1.6 1.6 1.7 1.7 1.9 Li2O 0.0 0.0 0.0 0.0 0.0 0.0 B2O3 0.0 0.0 0.0 0.0 0.0 0.0 BaO 0.0 0.0 0.0 0.0 0.0 0.0 TOTAL 99 99 99 99 99 99 K2O + Na2O 5.1 5.3 5.2 5.3 5.3 5.5 Composition of main α-Alumina 55 42 37 31 26 0 component in Quartz 8 9 10 11 12 15 Crystal phase Mullite 7 10 11 12 13 18 (% by weight) TOTAL 70 62 58 54 51 33 Composition of main Clay 32 33 33 33 34 35 component in Feldspar* 4 7 8 9 11 17 greenware raw material α-Alumina 58 46 41 35 29 0 (% by weight) Silica stone 6 5 4 4 3 0 Pottery stone 0 10 14 19 24 48 TOTAL 100 100 100 100 100 100 Properties Deformation 3.7 mm 5 mm 7 mm 9 mm 11 mm 21 mm quantity by Firing Shrinkage 2.30% 3.00% 3.50% 4.50% 5.50% 9.70% percentage by Firing Strength 93 MPa 92 MPa 92 MPa 92 MPa 92 MPa 90 MPa Thermal shock 150° C. 150° C. 150° C. 150° C. 150° C. 150° C. resistance difference difference difference difference difference difference Water absorption 9.30%   9%   8%   7%   5% 0.20% percentage Thermal 70 × 70 × 70 × 70 × 70 × 70 × expansion 10.sup.−7/° C. 10.sup.−7/° C. 10.sup.−7/° C. 10.sup.−7/° C. 10.sup.−7/° C. 10.sup.−7/° C. Crazing No No No No No No resistance penetration penetration penetration penetration penetration penetration *As feldspar which is the main component of the greenware raw material of the first greenware material, total amount (17% by weight) of feldspar (approx. 15% by weight) and dolomite (approx. 2% by weight) is shown.