Underglaze color bone china and preparation method thereof

Abstract

The invention relates to the field of porcelain preparation, in particular to underglaze color bone china and a preparation method thereof. The preparation method comprises the following steps of green body preparation, pattern application, biscuit firing, glazing, glaze firing, cooling and inspection. The under-glaze color bone china prepared by the method is not easy to deform and discolor, small in color difference, stable in color and uniform in glaze surface, the high-temperature firing frequency is reduced by optimizing the process, toxic gas and excessive heavy metal cannot be generated in the whole process, and the requirements of energy conservation and environmental protection are met.

Description

Technical Field

[0001] The present invention relates to the technical field of porcelain crafts, and in particular to underglaze colored bone porcelain and a preparation method thereof. Background Art

[0002] Underglaze painting, a ceramic decoration technique with a long history and immense artistic value, involves meticulously painting a pattern on the surface of a ceramic body, then applying a layer of glaze and firing it at high temperatures until the pattern is completely covered. This unique process not only ensures wear and corrosion resistance, but also ensures that its color remains stable over time, making it widely used in the decoration of various ceramic products.

[0003] Bone china, a high-end ceramic material, holds a significant position in the market due to its unique performance advantages. Its exceptional whiteness provides a pure, bright base for decorative patterns. Its exceptional light transmittance imparts an elegant, soft texture to finished products, revealing a unique artistic beauty under light. Furthermore, its high strength allows it to withstand both daily use and external impact. Due to these exceptional properties, bone china is often used in high-end ceramic products such as fine tableware and art pieces, and is highly sought after by consumers.

[0004] However, traditional underglaze coloring techniques face numerous technical challenges when applied to bone porcelain. During the high-temperature firing process, patterns are easily deformed, blurring and distorting the delicate patterns. Furthermore, the chemicals in the pigments can undergo complex reactions at high temperatures, causing color distortion and failing to achieve the desired decorative effect. Furthermore, the physical and chemical incompatibility between the glaze and the bone porcelain body can lead to cracking of the glaze during the firing and cooling process, forming noticeable fissures that severely impact the product's appearance. The glaze can even peel off during use, reducing the product's lifespan and quality.

[0005] Currently, the existing technology lacks an underglaze-painted production method specifically optimized for the material properties of bone china, which is unable to effectively address the aforementioned technical issues. These technical bottlenecks have significantly limited the promotion and application of underglaze-painted bone china products in the high-end market, making it difficult to meet consumers' growing demand for high-quality, artistically valuable ceramic products. Therefore, it is urgent to develop an improved underglaze-painted bone china production method to overcome the limitations of existing technology. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an underglaze colored bone porcelain and a preparation method thereof, which can achieve the fidelity of the pattern of underglaze colored bone porcelain, small color difference, and uniform glaze surface, while taking into account the production cost and the quality of bone porcelain underglaze colored process products.

[0007] In one aspect, the present invention provides a method for preparing underglaze colored bone porcelain, comprising the following steps:

[0008] Green billet preparation: mixing green billet raw materials to prepare the required bone green billet;

[0009] Pattern drawing: drawing underglaze colored patterns on the surface of the bone green blank;

[0010] Bisque firing: bisque firing the green clay with underglaze patterns;

[0011] Glazing: applying glaze to the bisque-fired body, wherein the deviation of the thermal expansion coefficient between the glaze and the body is ≤5%;

[0012] Glaze firing: glaze firing the glazed body;

[0013] Cooling and inspection.

[0014] Furthermore, based on 100% by mass of the glaze raw materials, the glaze raw materials include 60-65% SiO2, 15-20% Al2O3, 5-10% CaO and 3-5% K2O, and the rest is water.

[0015] Furthermore, the thermal expansion coefficient of the glaze is (4.8-5.2)×10⁻ 6 / ℃, the thermal expansion coefficient of the blank is (4.7-5.3)×10⁻ 6 / ℃.

[0016] Furthermore, the bone green blank raw material comprises, based on the raw material mass percentage as 100%, 40% to 50% bone ash, 30% to 50% kaolin, 15% to 20% feldspar, and 5% to 10% quartz. The bone green blank raw material of the present invention contains no chemical additives, is recyclable, and waste blanks can be crushed and re-mixed.

[0017] Furthermore, the bone ash is cattle bone ash with a Ca3(PO4)2 content of ≥95%. During the high-temperature brick-firing process, Ca3(PO4)2 reacts with silica and alumina in the raw materials to generate a fine and uniform crystal phase structure with uniform refractive index and chemical stability. At the same time, the high-purity cattle bone ash has an extremely low impurity content, which avoids color deviation caused by selective absorption of light by impurity elements and improves the whiteness of the bone porcelain body; and the formed fine and uniform crystal structure reduces scattering loss, allowing light to pass through the porcelain body smoothly, and after the Ca3(PO4)2 in the cattle bone reacts with other raw materials, it will form a glass phase inside the porcelain body and fill the space between the crystals, forming a good light-transmitting channel, which significantly improves the transmittance of the bone porcelain; it can ensure that the whiteness of the bone porcelain ligand obtained is ≥90% and the transmittance is ≥30%.

[0018] Furthermore, the green blank is formed by slip injection molding or pressing, and the density of the green blank is 2.3~2.5 g / cm³; controlling the density of the green blank can improve the strength of the green blank, and its flexural strength can reach more than 100Mpa, which is convenient for subsequent processes.

[0019] Furthermore, the underglaze pattern is hand-painted or printed. Compared to traditional hand-appliqué techniques, hand-painting can be performed directly on the green clay, eliminating one high-temperature firing step and reducing porcelain production costs. Furthermore, compared to hand-appliqué techniques, which rely on PET film, hand-painted or printed underglaze patterning techniques do not release toxic gases such as carbon monoxide and VOCs during firing, making them more environmentally friendly.

[0020] Furthermore, the printing method is digitally controlled inkjet printing, using ceramic-to-water based ink.

[0021] Furthermore, before drawing the underglaze pattern, the bone greenware is pretreated by spraying a 5-10 μm thick layer of water glass on its surface. This pretreatment enhances the adhesion of subsequent colorants to the greenware, significantly reducing pattern deformation and shedding during firing.

[0022] Furthermore, the pigments used to create the underglaze patterns are oxide-based pigments, including at least one of 20-30% cobalt oxide, 30-40% iron oxide, and 10-20% chromium oxide, with a particle size of 1-5 μm. The present invention utilizes high-temperature-resistant oxide pigments and controls the particle size within a relatively small range, ensuring that the underglaze patterns are delicate and fade-resistant even at high temperatures.

[0023] Furthermore, the bisque firing is carried out in an atmosphere with an oxygen volume ratio of 20% to 25%, the firing temperature is 1050 to 1250°C, the heating rate is 5°C / min, and the temperature is kept at 1250°C for 1 to 2 hours. The oxygen volume in the present invention refers to the volume of oxygen at standard atmospheric pressure.

[0024] Furthermore, the glaze firing temperature is 1080-1120°C, the heating rate is 4-6°C / min, after firing for 3-4 hours, the glaze is kept warm for 1-2 hours, and then naturally cooled to room temperature.

[0025] Another aspect of the present invention further provides an underglaze colored bone porcelain, which is prepared by the above method.

[0026] The present invention has the following beneficial effects: By optimizing the conventional bone china underglaze production process, the present method allows for the direct creation of underglaze patterns on the green base, making complex designs easy and simple while reducing the need for a single high-temperature firing step. Furthermore, the present method improves the thermal expansion coefficient matching between the glaze and the bone china base, resulting in a faithful, minimally chromatic, and uniform glaze surface after firing. This method achieves both high product quality and cost-effectiveness for bone china underglaze production. The method eliminates the introduction of impurities and the generation of toxic gases, ensuring environmental friendliness and meeting national standards for heavy metal content. Color difference ΔE ≤ 1.5, deformation ≤ 0.5%, glaze bubble rate ≤ 0.1%, and cracking ≤ 0.2% are achieved, reducing overall costs by 40% compared to decal production. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions of the present invention in conjunction with specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing underglaze colored bone porcelain, comprising the following steps:

[0030] (1) Preparation of green slab: Based on 100% raw material mass, 45% of cattle bone ash, 30% of kaolin, 15% of feldspar and 10% of quartz powder are mixed, and water accounting for 23% of the raw material mass is added and stirred thoroughly to form green slab wet material. The green slab of the designed style is formed by slip casting;

[0031] (2) Pattern drawing: First, prepare underglaze color pigments with a mass ratio of 10% cobalt oxide, 88% feldspar + quartz + kaolin mixed powder and 2% cellulose, and directly draw the traditional dragon design pattern on the surface of the above green clay;

[0032] (3) Bisque firing: The green blank with the pattern drawn is placed in a kiln for bisque firing. The thermal expansion coefficient of the green blank is 5.3×10⁻ 6 / ℃; control the volume percentage of oxygen in the kiln to 22%, the biscuit firing temperature to 1050~1250℃, the heating rate to 5℃ / min, and after the temperature reaches 1250℃, keep it warm for 1.5 hours;

[0033] (4) Glazing: Prepare the glaze by mixing 60% SiO2, 20% Al2O3, 10% CaO and 5% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 5.2×10⁻ 6 / ℃; evenly apply the prepared glaze on the surface of the green body;

[0034] (5) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C with a heating rate of 5°C / min. After heating to 1120°C, keep the temperature for 2 hours.

[0035] (6) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0036] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0037] Example 2

[0038] A method for preparing underglaze colored bone porcelain, comprising the following steps:

[0039] (1) Preparation of green blank: 40% of cattle bone ash, 35% of kaolin, 20% of feldspar and 5% of quartz powder are mixed, and 20% of water is added to the raw materials. The mixture is stirred thoroughly to form green blank wet material, and the green blank of the designed style is formed by slip casting;

[0040] (2) Spraying a 10 μm thick water glass layer on the surface of the green blank;

[0041] (3) Pattern drawing: First, prepare underglaze color pigments according to the weight ratio of 10% cobalt oxide, 87% feldspar + quartz + kaolin mixed powder and 3% cellulose, and directly draw the traditional dragon design pattern on the surface of the above green clay;

[0042] (4) Bisque firing: The green blank with the pattern painted on it is placed in a kiln for bisque firing. The thermal expansion coefficient of the green blank is 4.7×10⁻ 6 / ℃; control the volume proportion of oxygen in the kiln to 20%, the biscuit firing temperature to 1050~1250℃, the heating rate to 5℃ / min, and keep the temperature at 1250℃ for 1 hour;

[0043] (5) Glazing: Prepare the glaze by mixing 65% SiO2, 20% Al2O3, 5% CaO and 3% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 4.8×10⁻ 6 / ℃; evenly apply the prepared glaze on the surface of the green body;

[0044] (6) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C with a heating rate of 6°C / min. After heating to 1120°C, keep the temperature for 1 hour.

[0045] (7) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0046] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0047] Example 3

[0048] A preparation method of underglaze colored bone porcelain, the specific steps are as follows:

[0049] (1) Preparation of green blank: 50% of cattle bone ash, 20% of kaolin, 20% of feldspar and 10% of quartz powder are mixed, and water accounting for 25% of the raw material weight is added and stirred thoroughly to form green blank wet material, and the green blank of the designed style is formed by slip casting;

[0050] (2) Spraying a 10 μm thick water glass layer on the surface of the green blank;

[0051] (3) Pattern drawing: First, prepare underglaze color pigments with a mass ratio of 10% cobalt oxide, 88% feldspar + quartz + kaolin mixed powder and 2% cellulose, and directly draw the traditional dragon design pattern on the surface of the above green clay;

[0052] (4) Bisque firing: The green blank with the pattern drawn is placed in a kiln for bisque firing. The thermal expansion coefficient of the green blank is 5.1×10⁻ 6 / ℃, control the volume proportion of oxygen in the kiln to 25%, the biscuit temperature is 1050~1250℃, the heating rate is 5℃ / min, and after the temperature rises to 1250℃, keep it warm for 2 hours;

[0053] (5) Glazing: Prepare the glaze by mixing 60% SiO2, 20% Al2O3, 10% CaO and 3-5% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 5.1×10⁻ 6 / ℃; evenly apply the prepared glaze on the surface of the green body;

[0054] (6) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C, the heating rate is 4°C / min, and the temperature is heated to 1120°C and kept at this temperature for 2 hours.

[0055] (7) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0056] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0057] Comparative Example 1

[0058] An underglaze colored bone porcelain is prepared by the following method:

[0059] (1) Preparation of green billet: The raw materials are 45% of cattle bone ash, 30% of kaolin, 15% of feldspar and 10% of quartz powder, and water accounting for 23% of the raw materials is added and stirred thoroughly to form green billet wet material. The green billet of the designed style is formed by slip casting. The thermal expansion coefficient of the green billet is 5.3×10⁻ 6 / ℃;

[0060] (2) High-temperature biscuit firing: The green blank is subjected to high-temperature biscuit firing at a temperature of 1250°C for 1.5 hours;

[0061] (3) Painting the bisque-fired body to draw a dragon pattern. The painting pigment is made of the following mass components in percentage by mass: 10% cobalt oxide, 88% feldspar + quartz + kaolin mixed powder and 2% cellulose.

[0062] (4) High temperature color firing: The painted product is subjected to high temperature color firing at a temperature of 1200°C;

[0063] (5) Glazing: Prepare the glaze by mixing 65% SiO2, 20% Al2O3, 5% CaO and 3% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 5.2×10⁻ 6 / ℃; apply the prepared glaze evenly on the surface of the body;

[0064] (6) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C with a heating rate of 6°C / min. After heating to 1120°C, keep the temperature for 1 hour.

[0065] (7) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0066] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0067] Comparative Example 2

[0068] A method for preparing underglaze colored bone porcelain, comprising the following steps:

[0069] (1) Preparation of green billet: The raw materials are 45% of cattle bone ash, 30% of kaolin, 15% of feldspar and 10% of quartz powder, and water accounting for 23% of the raw materials is added and stirred thoroughly to form green billet wet material. The green billet of the designed style is formed by slip casting. The thermal expansion coefficient of the green billet is 6.1×10⁻ 6 / ℃;

[0070] (2) Pattern drawing: First, prepare underglaze color pigments with a mass ratio of 10% cobalt oxide, 88% feldspar + quartz + kaolin mixed powder and 2% cellulose, and directly draw the traditional dragon design pattern on the surface of the above green clay;

[0071] (3) Bisque firing: Place the green blank after the pattern is drawn in the kiln for bisque firing. The volume of the blank in the kiln is controlled to be 22%. The bisque firing temperature is 1050-1250℃, and the heating rate is 5℃ / min. After the temperature rises to 1250℃, keep it warm for 1.5 hours.

[0072] (4) Glazing: Prepare the glaze by mixing 60% SiO2, 20% Al2O3, 10% CaO and 5% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 5.7×10⁻ 6 / ℃; evenly apply the prepared glaze on the surface of the green body;

[0073] (5) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C with a heating rate of 5°C / min. After heating to 1120°C, keep the temperature for 2 hours.

[0074] (6) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0075] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0076] Comparative Example 3

[0077] A method for preparing underglaze colored bone porcelain, comprising the following steps:

[0078] (1) Preparation of green slab: Based on 100% raw material mass, 45% of cattle bone ash, 30% of kaolin, 15% of feldspar and 10% of quartz powder are mixed, and water accounting for 23% of the raw material mass is added and stirred thoroughly to form green slab wet material. The green slab of the designed style is formed by slip casting;

[0079] (2) Pattern printing: First, the traditional dragon pattern design is printed on the heat transfer decal paper by digital printing, the dragon pattern is cut, and pressed on the green body at 180~220℃ and dried naturally;

[0080] (3) Bisque firing: The green blank with the pattern drawn is placed in a kiln for bisque firing. The thermal expansion coefficient of the green blank is 5.3×10⁻ 6 / ℃; control the volume percentage of oxygen in the kiln to 22%, the biscuit firing temperature to 1050~1250℃, the heating rate to 5℃ / min, and after the temperature reaches 1250℃, keep it warm for 1.5 hours;

[0081] (4) Glazing: Prepare the glaze by mixing 60% SiO2, 20% Al2O3, 10% CaO and 5% K2O, with the remainder being water. The thermal expansion coefficient of the glaze is 5.2×10⁻ 6 / ℃; evenly apply the prepared glaze on the surface of the green body;

[0082] (5) Glaze firing: Place the glazed body in a kiln for glaze firing. The temperature is controlled at 1080-1120°C with a heating rate of 5°C / min. After heating to 1120°C, keep the temperature for 2 hours.

[0083] (6) Cooling and testing: Cool naturally to room temperature to prepare underglaze colored bone porcelain; test the prepared underglaze colored bone porcelain.

[0084] The color difference, deformation rate, glaze bubble rate, crack rate and heavy metal lead (Pb) and cadmium (Cd) of underglaze colored bone porcelain are tested.

[0085] Detection method:

[0086] A sample size of 50 pieces was randomly selected from the underglaze colored bone porcelain products prepared in Examples 1-3 and Comparative Examples 1-2, and performance tests were performed. The test indicators were color difference, deformation rate, glaze bubble rate, and crack rate. The average value of each indicator was taken as the test result of the present invention. The test results are shown in Table 1.

[0087] Color difference is measured using a colorimeter: a colorimeter is used to measure the color of the painted pattern on the porcelain against the color on a standard color chart. The difference between the two values ​​is the color difference. The specific method involves calibrating the colorimeter. Then, multiple measurement points (generally no less than 5) are selected on the surface of the bone china sample and their color parameters are measured separately. Finally, the measured data is compared with a standard sample or a specified color range, and the ΔE value is calculated using a built-in formula.

[0088] Deformation rate: The graphic images before and after firing are imported into professional image analysis software. Through image registration technology, the graphics of the two images are made to completely overlap. The software calculates the size changes of each part of the graphic through pixel analysis to obtain the deformation rate value.

[0089] Glaze bubble rate: If industrial CT is used, the scanned images are analyzed by software to automatically identify and count bubbles.

[0090] Cracking rate: First, use the visual method to comprehensively observe the bone china glaze surface under sufficient lighting conditions using a magnifying glass (generally 10-20 times) and mark the areas where cracks are present. Then, use a high-definition camera to photograph the marked areas, import the images into image analysis software, and use the software to calculate the area of ​​the cracked areas. Finally, the cracking rate is calculated according to the formula "Cracking rate = (cracked area ÷ total inspection area) × 100%."

[0091] Table 1

[0092]

[0093] As shown in Table 1, the underglaze colored bone porcelain produced in Examples 1-3 of the present invention strictly complies with the national standard GB / T13522-2024 in key indicators such as color difference (ΔE ≤ 1.5), deformation rate (≤ 0.5%), glaze bubble rate (≤ 0.1%), and cracking rate (≤ 0.2%). Compared with Comparative Examples 1-3, this process significantly improves pattern fidelity, reduces color difference, and ensures glaze uniformity. Furthermore, through technical optimization, this process reduces overall costs by over 40% compared to traditional processes, breaking through the bottleneck of balancing quality and cost. The production process eliminates impurities and produces no toxic gases, meeting environmental protection requirements. This further broadens its application in various fields, such as tableware and handicrafts, demonstrating significant technical and market advantages.

[0094] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing underglaze colored bone porcelain, characterized in that: The following steps are involved: Green billet preparation: mixing green billet raw materials to prepare the required bone green billet; Pattern drawing: drawing underglaze colored patterns on the surface of the bone green blank; Bisque firing: bisque firing the green clay with underglaze patterns; Glazing: applying glaze to the bisque-fired body, wherein the deviation of the thermal expansion coefficient between the glaze and the body is ≤5%; Glaze firing: glaze firing the glazed body; Cooling and inspection.

2. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: Based on the mass percentage of the glaze raw materials being 100%, the glaze raw materials include 60-65% SiO2, 15-20% Al2O3, 5-10% CaO and 3-5% K2O, and the rest is water.

3. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: described The thermal expansion coefficient of the glaze is (4.8-5.2)×10⁻ 6 / ℃, the thermal expansion coefficient of the green billet is (4.7-5.3)×10⁻ 6 / ℃.

4. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: Based on the raw material mass being 100%, the bone green blank raw material includes 40% to 50% bone ash, 20% to 35% kaolin, 15% to 20% feldspar and 5% to 10% quartz.

5. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: The underglaze color pattern is hand-painted or printed.

6. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: Before drawing the underglaze color pattern, the method further includes spraying a 5-10 μm thick water glass layer on the surface of the bone green blank.

7. The method for preparing underglaze colored bone china according to claim 1, characterized in that: The color pigment used to draw the underglaze color pattern adopts an oxide-based pigment, and the pigment particle size is 1-5 μm.

8. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: The bisque firing is carried out in an atmosphere with an oxygen volume ratio of 20% to 25%, a firing temperature of 1050 to 1250°C, a heating rate of 5°C / min, and after heating to 1250°C, the temperature is kept at 1 to 2 hours.

9. The method for preparing underglaze colored bone porcelain according to claim 1, characterized in that: The glaze firing temperature is 1080-1120°C, the heating rate is 4-6°C / min, after firing for 3-4 hours, the glaze is kept warm for 1-2 hours, and then cooled naturally to room temperature.

10. An underglaze colored bone porcelain, characterized in that: The underglaze colored bone porcelain is prepared by the preparation method according to any one of claims 1 to 9.

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