JP2024095343A - Pottery with glaze layer - Google Patents

Abstract

To provide pottery with good performance, such as pottery that has excellent resistance to penetration and to rapid cooling and effectively prevents a glaze surface from peeling off, in spite of employing a vitreous base.SOLUTION: Pottery at least comprises a layer which comprises a vitreous base and a glaze. The thermal expansion coefficient of the vitreous base is larger than that of the glaze with the difference therebetween being in the range from 5×10-7/K to 25×10-7/K. The vitreous base contains quartz, where the maximum particle size of the quartz is 50 μm or less. The water absorption rate of the vitreous base is 0.5% or less. The pottery has excellent resistance to penetration and to rapid cooling, and effectively prevents the glaze surface from peeling off.SELECTED DRAWING: None

Description

The present invention relates to pottery with a glaze layer, and more specifically to pottery in which a glaze layer is provided on a vitreous clay base.

Ceramics such as sanitary ware and tiles basically consist of a base and a glaze layer applied to its surface, and the adhesion between the base and the glaze layer affects the durability and appearance of the final ceramic. In particular, the base shrinks and deforms during the firing process, so the combination of the base and the glaze layer is important.

JP 2002-114566 A (Patent Document 1) discloses consideration of the coefficient of thermal expansion in the combination of the base and the glaze layer. Specifically, the glaze is made to have a coefficient of thermal expansion 0-30×10 ^-7 /°C smaller than that of the base, which makes it difficult for fine cracks to occur on the glaze surface due to aging (paragraph 0022), and furthermore, it is said that the impact strength of the base, which has a coefficient of thermal expansion of 50-90× ^-7 /°C (50-600°C), is 2×10 ^-1 J/cm ² or more (paragraphs 0023 and 0024). The base disclosed in this publication is a non-vitrified base due to its composition, firing conditions, water absorption rate of 18%, etc.

In addition, from the perspective of so-called "glaze peeling," Japanese Patent Laid-Open Publication No. 6-056516 (Patent Document 2) focuses on the thermal expansion coefficients of the vitreous base and glaze when the temperature is increased, and states that it is preferable to match the thermal expansion behavior of the glaze when the temperature is increased to that of the base, and discloses a method for achieving this.

JP 2002-114566 A Japanese Patent Application Laid-Open No. 6-056516

The inventors have now discovered that by combining vitreous base and glaze that have a certain difference in their thermal expansion coefficients when heated, rather than matching them, and further controlling the form in which quartz is present, it is possible to realize pottery with good performance. Specifically, they have discovered that it is possible to realize pottery that has excellent resistance to penetration and rapid cooling, and effectively prevents the occurrence of peeling of the glaze surface.

Therefore, the object of the present invention is to provide pottery that uses a vitreous body and has good performance, for example, pottery that has excellent resistance to penetration and rapid cooling and effectively prevents the occurrence of peeling of the glaze surface.

And the pottery according to the present invention is
A pottery having at least a vitreous body and a layer of glaze,
The thermal expansion coefficient of the vitreous body is greater than that of the glaze, the difference being in the range of 5×10 ⁻⁷ /K to 25×10 ⁻⁷ /K;
The vitreous body contains quartz, and the maximum grain size of the quartz is 50 μm or less;
The vitreous clay has a water absorption rate of 0.5% or less.

The present invention provides pottery with good performance, for example, pottery that is excellent in resistance to penetration and rapid cooling and effectively prevents the occurrence of peeling of the glaze surface, using a vitreous body.

In the present invention , "ceramics" refers to sanitary ware, tiles, and other items that have a basic structure of a glaze layer on a base material. In addition, "sanitary ware" refers to ceramic products used in bathrooms, toilet spaces, dressing rooms, washrooms, kitchens, etc. Specifically, it refers to toilet bowls, urinals, toilet basins, toilet tanks, wash basins, hand basins, etc.

The pottery according to the present invention comprises at least a vitreous base and a layer made of a glaze. The thermal expansion coefficient of the base is greater than that of the glaze, and the difference is in the range of 5×10 ⁻⁷ /K to 25×10 ⁻⁷ /K. By setting the difference between the thermal expansion coefficients of the two in the above range, pottery with good properties and performance can be realized. Specifically, since the crack generation on the base surface or the glaze surface can be effectively prevented by excellent resistance to penetration, which suppresses the occurrence of penetration into the glaze surface, and excellent resistance to quenching, the occurrence of glaze skipping, i.e., peeling of the glaze surface, can be effectively prevented. As proposed in the above-mentioned Patent Document 3, matching the thermal expansion coefficient of the base with that of the glaze can effectively prevent the occurrence of peeling of the glaze surface, but it should be evaluated as a surprising fact that the thermal expansion coefficient of the base is greater than that of the glaze, and the difference is set in the above range, and thus the crack generation resistance and the quenching resistance are excellent.

According to a preferred embodiment of the present invention, the range of the difference between the thermal expansion coefficient of the base and the thermal expansion coefficient of the glaze has a lower limit of preferably 6×10 ⁻⁷ /K, more preferably 10×10 ⁻⁷ /K, and an upper limit of preferably 22×10 ⁻⁷ /K, more preferably 20×10 ⁻⁷ /K. Having the difference within these preferred ranges provides greater advantages in terms of resistance to penetration or quenching.

In the present invention, the vitreous body contains quartz, and the maximum grain size of this quartz is 15 μm or more and 50 μm or less. In a preferred embodiment, the maximum grain size of the quartz is 17 μm or more and 48 μm or less, more preferably 19 μm or more and 46 μm or less. By having the maximum grain size of quartz within the above range, pottery with good properties and performance can be realized, specifically pottery with excellent resistance to penetration and quenching can be realized.

In addition, according to a preferred embodiment of the present invention, the quartz content is 22% by weight or less. In a preferred embodiment, the quartz content is 8-22% by weight, more preferably 10-20% by weight.

In the present invention, the water absorption rate of the vitreous clay is 0.5% or less, preferably 0.48% or less, and more preferably 0.46% or less.

According to a preferred embodiment of the present invention, the thermal expansion coefficient of the vitreous body itself is preferably 63×10 ⁻⁷ /K to 75×10 ⁻⁷ /K, and more preferably 64×10 ⁻⁷ /K to 5874×10 ⁻⁷ /K.

According to a preferred embodiment of the present invention, the thermal expansion coefficient of the glaze itself is preferably about 50×10 ⁻⁷ /K to 58×10 ⁻⁷ /K, and more preferably 51×10 ⁻⁷ /K to 57×10 ⁻⁷ /K.

Vitrification The vitrification of the pottery according to the present invention means a body that has a dense and homogeneous structure and is fired until it has few or no open pores. Here, "vitrification" refers to the phenomenon in which the body particles melt during firing to produce a glass phase, which becomes fluid at high temperatures and fills the gaps between the body particles that did not melt. The distinction between particles that melt and particles that do not melt is determined by the difference in melting point due to the type of crystal that constitutes the particle, the combination of the crystals (even if a crystal has a high melting point by itself, the melting point may be lowered by the presence of other crystals), and the firing temperature and time. Examples of raw materials that melt include feldspars that act as melting agents and clays that give plasticity to the body during molding, and examples of raw materials that do not melt include quartz. However, quartz does not necessarily not melt at all, but may have a structure in which a part of it melts and dissolves into the glass phase, and a part of it remains as crystals.

Examples of clays that can be used as raw materials for the vitreous clay body in the present invention include clay minerals such as kaolinite, halloysite, metahalloysite, dickite, and pyrophyllite, and clay-like micas such as sericite and illite. These minerals are abundantly contained in clay raw materials such as frog-eye clay, kibushi clay, kaolin, ball clay, and china clay, as well as in various pottery stones, and are also contained in part in feldspar raw materials. Of these clays, kaolinite and halloysite are particularly excellent at improving plasticity during molding, and sericite is highly effective in lowering the firing temperature of the body. These clay minerals melt during firing to form a glass phase, but some may remain unmelted as crystals.

In addition, examples of feldspars that are raw materials for the vitreous body that can be used in the present invention include feldspar minerals such as potassium feldspar, soda feldspar, and anorthite, nephelite, natural glass, frit, etc. These raw materials are abundantly contained in various feldspar raw materials, nepheline syenite, Cornish stone, mackerel, glassy volcanic rocks, and various pottery stones, and are also partially contained in clay raw materials. As these feldspars, those that are rich in K ₂ O and Na ₂ O as alkaline components are particularly preferable, and examples thereof include potassium feldspar, soda feldspar, and nepheline. In addition, nepheline syenite, which does not substantially contain any quartz in its composition, can also be used. These feldspar minerals melt during firing to form a glass phase, but some may remain unmelted as crystals.

Examples of quartz, which is a raw material for the vitreous clay that can be used in this invention, include raw materials that are almost entirely made of quartz, such as silica sand and silica stone, and also include the various pottery stones mentioned above, saba, feldspathic raw materials, and clayey raw materials, and these can also be used because quartz is contained in these raw materials.

The vitreous body that can be used in the present invention can contain α-alumina.

According to a preferred embodiment of the present invention, the body constituting the pottery according to the present invention has the following composition:
_SiO2 60 to 75% by weight, preferably 65 to 72.5% by weight,
Al ₂ O ₃ 20 to 30% by weight, preferably 22.5 to 27.5% by weight,
_{Fe2O3 0.4-1.5} wt%, preferably 0.5-1.4 wt%,
CaO: 0.1 to 2.0% by weight, preferably 0.2 to 1.5% by weight;
0.1 to 1.5% by weight, preferably 0.2 to 1.2% by weight, of MgO;
K ₂ O: 0.8-5.0 wt %, preferably 1.0-4.0 wt %, and Na ₂ O: 0.4-4.0 wt %, preferably 0.8-3.0 wt %.
including.

Glaze The glaze for forming the glaze layer of the pottery according to the present invention is not particularly limited, and various glazes can be used, and further, glazes of various colors can be used.

In the present invention, the glaze may be a mixture of natural mineral particles such as silica sand, feldspar, and limestone and/or an amorphous glaze to which a pigment and/or an opacifier have been added. For example, the composition of the glaze is SiO ₂ : 52 to 80 parts by weight, Al ₂ O ₃ : 5 to 14 parts by weight, CaO: 6 to 17 parts by weight, MgO: 0.5 to 4.0 parts by weight, ZnO: 1 to 11 parts by weight, K ₂ O: 1 to 5 parts by weight, Na ₂ O: 0.5 to 2.5 parts by weight, opacifier: 0.1 to 15 parts by weight, pigment: 0.001 to 20 parts by weight. The glaze may further contain a paste, a dispersant, a preservative, an antibacterial agent, etc. Examples of the pigment include a cobalt compound and an iron compound. Examples of the opacifier include zircon and tin oxide. The amorphous glaze refers to a glaze obtained by melting a glaze raw material consisting of a mixture of the above-mentioned natural mineral particles at a high temperature and vitrifying it, and for example, a frit glaze can be suitably used.

The colors of the glazes that can be used in the present invention include colors expressed as white, ivory, gray, pink, and brown, or colors expressed as white, pastel ivory, white gray, pastel pink, and harvest brown. White, ivory, gray, pink, and brown are, for example, colors that are similar to N8.6, 3.0Y 8.7/0.9, 1.4Y 7.8/0.5, 0.9YR8.2/1.9, and 8.3YR7.1/1.2, respectively, when expressed in Munsell values, and colors that are similar to LN93, L19-92B, LN-80, L09-80D, and L19-70B, respectively, when expressed in standard paint colors of the Japan Paint Manufacturers Association.

According to one aspect of the invention, the glaze layer can be a transparent glaze layer on top of a colored glaze layer.

The pottery according to the present invention may be manufactured by appropriately determining the firing conditions in consideration of the composition of the base and the glaze. For example, after applying the glaze to the base, the pottery is fired at a temperature of 1100 to 1300° C. for 2 to 2.5 hours with a temperature rise rate of about 1.2 to 25° C./min, thereby sintering the molded base and fixing the glaze layer.

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

Test 1: Preparation of Vitreous Body Test Pieces Vitreous bodies 1 to 3 having the compositions shown in Table 1 were obtained as follows. As raw materials, 8 to 45% by weight of sericite pottery stone and kaolin pottery stone, or silica stone as a skeleton forming material, 28 to 65% by weight of china clay (powder) and ball clay (powder) as a plastic material, about 10 to 35% by weight of feldspar as a main sintering aid, and 1 to 4% by weight of dolomite were weighed out, and water and an appropriate amount of sodium silicate as a peptizing agent were added and placed in a ball mill. The mixture was wet-ground until the particle size measurement result of the ground slurry after grinding using a laser diffraction particle size distribution analyzer showed that 52 to 60% of the particles were 10 μm or less and the 50% average particle size (D50) was about 7 to 9 μm, to obtain a ceramic base material. The obtained ceramic base material was molded by a slip casting molding method using a plaster mold to obtain a molded body. The obtained molded body was fired in an electric furnace to obtain vitreous bodies 1 to 3 shown in Table 1. The maximum temperature of the heat curve was about 1200°C.

Physical property evaluation The following items and methods were measured for the obtained vitreous bodies 1 to 3. The results were as shown in Table 1 above.

Ink penetration: Measured according to JIS A5207.

Water absorption rate Water absorption rate was measured according to JIS A1509-3. A sintered sample of the base material was dried at 110°C for 24 hours, cooled, and then the mass W1 was measured. Next, the sample was immersed in water in a desiccator and held in a vacuum for 1 hour to forcibly saturate the open pores with water, and the mass W2 at this time was measured. The water absorption rate was calculated using the following formula.
Water absorption rate = (W2 - W1) / W1 x 100 (%)

The amount of each crystal phase of quartz and mullite present as crystal phases was quantified by an X-ray diffractometer based on a calibration curve of a standard substance and expressed as weight percent. Quartz was observed under an electron microscope, and the average and maximum grain sizes were determined by analyzing the images.

Thermal expansion coefficient: Using a sintered test piece having a diameter of 5 mm and a length of 20 mm, the linear thermal expansion coefficient was determined by a differential dilatometer using a compressive load method in a measurement temperature range of 50 to 600° C., and this was taken as the thermal expansion coefficient.

Test 2: Preparation of glazes Glazes 1 to 8 having the compositions shown in Table 2 were obtained as follows. 2 kg of the glaze raw materials, 1 kg of water, and 4 kg of spheres were placed in a 6-liter ceramic pot, and crushed in a ball mill so that the particle size measurement results of the colored glaze slurry after crushing using a laser diffraction particle size distribution analyzer showed that 65% of the particles were 10 μm or less and the 50% average particle size (D50) was about 6.0 μm, to obtain glazes. The color of the glaze was adjusted so that the color of the glaze layer after firing was white.

Thermal expansion coefficient The thermal expansion coefficient of the obtained glazes 1 to 8 was measured as follows. After pouring the glaze into the engraved refractory material and firing it, the glaze part was cut out and processed into a test piece with a diameter of 5 mm and a length of 20 mm. The linear thermal expansion coefficient was measured by a differential dilatometer using a compression load method in a measurement temperature range of 50 to 600°C, and this was taken as the thermal expansion coefficient.

Test 3: Pottery production: Molded bodies corresponding to vitreous bodies 1 to 3 were obtained by the same method as in Test 1, and the glazes 1 to 8 obtained in Test 2 were applied to these molded bodies and fired to obtain pottery. The firing conditions were appropriately determined in consideration of the composition of the pottery body and the glaze. For example, after applying the glaze to the pottery body, the molded body was sintered and the glaze layer was fixed by firing at a temperature of 1100 to 1300°C for 2 to 25 hours with a temperature rise rate of about 1.2 to 25°C/min.

Evaluation of Physical Properties The pottery obtained by combining the obtained vitreous bodies 1 to 3 and the obtained glazes 1 to 8 was subjected to the following tests.

The penetration resistance was tested according to JIS A 5207 8.1.1 c).

The quench resistance test was conducted in accordance with JIS A 5207 8.1.1 b). Products that were able to suppress cracks on the base surface and glaze surface were rated as "Good", products that had cracks in some parts of the product were rated as "Good", and products that had cracks all over the product were rated as "Poor".

The pottery obtained by the glaze-skimming firing was visually inspected for the appearance of the pottery surface and the glaze surface to check for the occurrence of glaze peeling. Then, products that had been able to suppress glaze peeling on the glaze surface were rated as "Good", products that had glaze peeling in some parts of the product were rated as "Good", products that had glaze peeling over the entire product were rated as "Poor", and products that had glaze peeling over the entire product were rated as "Poor".

The results are shown in Tables 3 to 5 below.

The results shown in Tables 3 to 5 above show that the thermal expansion coefficient of the base is greater than that of the glaze, with the difference being in the range of 5×10 ⁻⁷ /K to 25×10 ⁻⁷ /K, which results in excellent resistance to penetration and quenching and prevents the glaze surface from peeling.

Preferred aspects of the present invention
Preferred aspects of the present invention are as follows.
(1) Pottery comprising at least a vitreous clay body and a layer of glaze,
The thermal expansion coefficient of the base is greater than the thermal expansion coefficient of the glaze, the difference being in the range of 5×10 ⁻⁷ /K to 25×10 ⁻⁷ /K;
The vitreous body contains quartz, and the maximum grain size of the quartz is 50 μm or less;
The ceramic ware is characterized in that the water absorption rate of the vitreous clay is 0.5% or less.
(2) The pottery according to (1), wherein the difference between the thermal expansion coefficient of the vitreous clay and the thermal expansion coefficient of the glaze is 6×10 ⁻⁷ /K or more.
(3) The pottery according to (1) or (2), wherein the difference between the thermal expansion coefficient of the vitreous clay and the thermal expansion coefficient of the glaze is 22×10 ⁻⁷ /K or less.
(4) The ceramic according to any one of (1) to (3), wherein the thermal expansion coefficient of the vitreous clay is 63×10 ⁻⁷ /K to 75×10 ⁻⁷ /K.
(5) The ceramic according to any one of (1) to (4), wherein the thermal expansion coefficient of the vitreous clay is 50×10 ⁻⁷ /K to 58×10 ⁻⁷ /K.
(6) The pottery according to any one of (1) to (5), wherein the vitreous body contains 22% by weight or less of quartz, and the maximum grain size of the quartz is 15 μm or more and 50 μm or less.
(7) The composition of the vitreous clay is
_SiO2 60 to 75% by weight, preferably 65 to 72.5% by weight,
Al ₂ O ₃ 20 to 30% by weight, preferably 22.5 to 27.5% by weight,
_{Fe2O3 0.4-1.5} wt%, preferably 0.5-1.4 wt%,
CaO 0.1 to 2.0% by weight, preferably 0.2 to 1.5% by weight,
MgO 0.1 to 1.5% by weight, preferably 0.2 to 1.2% by weight,
K ₂ O: 0.8-5.0 wt %, preferably 1.0-4.0 wt %, and Na ₂ O: 0.4-4.0 wt %, preferably 0.8-3.0 wt %.
The pottery according to any one of (1) to (6),
(8) The ceramic according to any one of (1) to (7), which is sanitary ware or tile.

Claims (8)

A pottery having at least a vitreous body and a layer of glaze,
The thermal expansion coefficient of the base is greater than the thermal expansion coefficient of the glaze, the difference being in the range of 5×10 ⁻⁷ /K to 25×10 ⁻⁷ /K;
The vitreous body contains quartz, and the maximum grain size of the quartz is 50 μm or less;
The ceramic ware is characterized in that the water absorption rate of the vitreous clay is 0.5% or less. 2. The pottery according to claim 1, wherein the difference between the thermal expansion coefficient of said vitreous body and the thermal expansion coefficient of said glaze is 6×10 ⁻⁷ /K or more. 3. The pottery according to claim 1, wherein the difference between the thermal expansion coefficient of said vitreous body and the thermal expansion coefficient of said glaze is 22×10 ⁻⁷ /K or less. 3. The ceramic according to claim 1, wherein the thermal expansion coefficient of the vitreous clay is 63×10 ⁻⁷ /K to 75×10 ⁻⁷ /K. 3. The ceramic according to claim 1, wherein the thermal expansion coefficient of the vitreous clay is 50×10 ⁻⁷ /K to 58×10 ⁻⁷ /K. The pottery according to claim 1 or 2, wherein the vitreous body contains 22% or less by weight of quartz, and the maximum grain size of the quartz is 15 μm or more and 50 μm or less. The composition of the vitreous clay is
_SiO2 60 to 75% by weight, preferably 65 to 72.5% by weight,
Al ₂ O ₃ 20 to 30% by weight, preferably 22.5 to 27.5% by weight,
_{Fe2O3 0.4-1.5} wt%, preferably 0.5-1.4 wt%,
CaO 0.1 to 2.0% by weight, preferably 0.2 to 1.5% by weight,
MgO 0.1 to 1.5% by weight, preferably 0.2 to 1.2% by weight,
K ₂ O: 0.8-5.0 wt %, preferably 1.0-4.0 wt %, and Na ₂ O: 0.4-4.0 wt %, preferably 0.8-3.0 wt %.
The pottery according to claim 1 or 2. The ceramic according to claim 1 or 2, which is sanitary ware or tile.