A process for the production of ceramic articles using a special gradual glaze slip composition for the process of sgraffito

Abstract

This invention discloses a process for preparing ceramic products using a special gradient glaze composition for the carving technique, relating to the fields of ceramic decorative materials and glazing processes. The process includes: preparing basic glaze components and high-temperature stable inorganic pigments according to weight parts, and preparing a basic glaze slurry with a solid content of 45%-50%; dividing the basic glaze slurry into at least two parts and adding high-temperature stable inorganic pigments to each part to obtain different color pastes corresponding to adjacent color areas; adjusting the interface between adjacent color pastes; applying each color paste in a layered, overlapping spray pattern to the surface of the ceramic body according to the color transition sequence, forming an overlapping transition zone between adjacent color areas; drying to a semi-dry state and then performing carving; finally, pre-firing and high-temperature firing to obtain the ceramic product. This process is suitable for preparing ceramic products combining gradient spraying and semi-dry carving.

Description

Technical Field

[0001] This invention relates to the field of ceramic decorative materials and glazing processes, specifically to a process for preparing ceramic products using a special gradient glaze composition for the shaving process. Background Technology

[0002] Traditional carved decoration typically involves applying a single-color or simply colored glaze to the ceramic body, then carving fine grooves after the glaze has reached a semi-dry state, resulting in raised and recessed textures after firing. This type of glaze pattern has relatively limited layers and struggles to achieve a multi-colored gradient visual effect.

[0003] In pursuit of thickness and a relief-like feel, Chinese patent CN102658753A proposed a method for preparing embossed glaze art porcelain by screen printing embossed decorative patterns, transferring decals, and then firing. To print the raised and bottom decorative patterns, it uses ink made from high-temperature lead-free and cadmium-free ceramic pigments and ink oil. Although the decorative layer can reach a thickness of 60–80 μm and simulate a certain texture by screen printing and decals onto the body, it is still essentially a mechanical printing and decal process, losing the texture of semi-dry micro-engraving.

[0004] On the other hand, gradient glaze effects are also used in modern ceramics. For example, Chinese patent CN106396638A discloses a low-temperature lightweight white-gray gradient glaze ceramic and its manufacturing process. This technology involves adjusting the base glaze and top glaze formulas, applying them to the body, and firing at 950–1030℃ in one firing, allowing the glaze surface to naturally form a gradient from milky white to dark gray through chemical reactions within the kiln. However, because this method relies on kiln transformation to spontaneously form the transition without actively adapting and adjusting the color slurry interface, it is difficult to obtain precise control of the gradient boundary zone; moreover, its glaze slurry is relatively brittle when dried to a semi-dry state, lacking a tough window suitable for continuous fine needle engraving; in addition, conventional low-temperature gradient glazes have extremely high fluidity at high temperatures, and if used for high-temperature firing above 1280℃, the pre-engraved micro-textures will easily be leveled and passivated.

[0005] Therefore, there is currently a lack of technology that can truly integrate gradient effects with the carving process. The industry urgently needs a dedicated gradient glaze and its process that can create a natural and controllable color transition during the spraying and overlapping stage, provide stable and chip-resistant support and toughness during the semi-dry carving stage, and maintain clear physical carving texture after high-temperature mature firing. Summary of the Invention

[0006] The purpose of this invention is to provide a process for preparing ceramic products using a special gradient glaze composition for the carving process. By combining formulation, color separation slurry preparation, interface adaptation adjustment, layered overlapping spraying, semi-dry carving, pre-firing and high-temperature firing, the problem of unnatural gradient spraying transition, easy edge chipping of semi-dry carving and easy blurring of texture after firing is solved.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a process for preparing ceramic products using a special gradient glaze composition for the carving process, comprising the following steps: S1. Prepare the basic glaze components and high-temperature stable inorganic pigments by weight. The basic glaze components include: 35-38 parts feldspar powder, 22-24 parts quartz powder, 16-17 parts kaolin, 6-7 parts dolomite powder, 5-7 parts glass frit powder, 0.8-1.2 parts clay minerals, 1.0-1.5 parts zirconium oxide, 0.2-0.5 parts rare earth oxides, 1.0-1.5 parts zirconium silicate, 0.5-0.8 parts sodium alginate, 0.3-0.5 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose. The total amount of the high-temperature stable inorganic pigments is 3-5 parts. The clay minerals are bentonite and / or palygorskite, and the rare earth oxides are cerium oxide and / or lanthanum oxide. The high-temperature stable inorganic pigments are selected from one or a combination of at least two of spinel-type inorganic pigments and zirconium-coated inorganic pigments. S2, mix the base glaze components with water, and add 0.1%-0.3% glycerol according to the total mass of the base glaze components and the high-temperature stable inorganic pigment. After ball milling or dispersion, a base glaze slurry with a solid content of 45%-50% is obtained. S3, the base glaze is divided into at least two parts, and different types and / or different contents of the high-temperature stable inorganic pigments are added to each part to obtain different color pastes corresponding to adjacent color areas; S4, add an interface adaptor to each adjacent color paste to adapt and adjust the dispersion state of the adjacent color pastes so that the viscosity difference between the adjacent color pastes at 25°C is not greater than 10% and / or the flowability difference is not greater than 5mm. The interface adaptor is selected from one or at least two of polyacrylic acid, polyacrylate, aqueous solution of polyacrylic acid or polyacrylate, and calcium chloride solution. S5, after the interface adaptation adjustment, the various color pastes are sprayed in layers on the surface of the ceramic body in the order of color transition to form a gradient glaze layer with overlapping transition areas. S6, the sprayed ceramic blank is dried so that the gradient glaze layer reaches a semi-dry state suitable for engraving. S7. When the gradient glaze layer is in a semi-dry state, a scribing tool is used to continuously scribble along a preset pattern to form micro-grooves. S8, pre-fire the ceramic blank after it has been engraved; S9 involves firing the pre-fired ceramic blank at high temperature to obtain ceramic products.

[0008] According to a preferred embodiment of the present invention, in step S5, a first color area corresponding to the first color paste and a second color area corresponding to the second color paste are first determined on the surface of the ceramic body, and an overlapping transition area is determined between the first color area and the second color area; the first color paste is first sprayed three times in the first color area, and then atomized and sprayed two times towards the overlapping transition area, so that the spraying range of the first color paste extends to the overlapping transition area, and a gradually thinning edge layer is formed in the overlapping transition area; before the first color paste is completely dry, the second color paste is sprayed three times in the second color area, and then atomized and sprayed two times towards the overlapping transition area, so that the spraying range of the first color paste extends to the overlapping transition area, and a gradually thinning edge layer is formed in the overlapping transition area; The spraying range of the two-color paste extends to the overlapping transition area, forming a gradually thinning edge layer within the overlapping transition area, and ensuring that the edge of the second color paste at least partially covers the edge layer formed by the first color paste within the overlapping transition area; then, the overlapping transition area is sprayed with the first color paste and / or the second color paste 1-3 times in thin layers, so that the first color paste and the second color paste form a layered and overlapping color transition within the overlapping transition area; and finally, within the overlapping transition area, the amount of the first color paste sprayed gradually decreases along the direction from the first color area to the second color area, while the amount of the second color paste sprayed gradually increases along the same direction.

[0009] According to a preferred embodiment of the present invention, in step S5, a pneumatic spray gun is used for spraying. The nozzle diameter of the spray gun is 0.8-1.2mm, the atomization pressure is 0.15-0.25MPa, the distance between the nozzle and the surface of the ceramic blank is 180-250mm, the angle between the spray gun and the surface of the ceramic blank is 80°-90°, and the travel speed is 80-120mm / s.

[0010] According to a preferred embodiment of the present invention, in step S5, the thickness of the wet glaze layer formed by each spraying is 50-100 μm, the thickness of the wet glaze layer formed by thin-layer sweeping is 20-50 μm, and the total wet film thickness of the gradient glaze layer after spraying is 220-300 μm.

[0011] According to a preferred embodiment of the present invention, in step S5, the width of the overlapping transition zone is 10-30mm.

[0012] According to a preferred embodiment of the present invention, in step S5, after each coat of paint is applied, the mixture is left to stand for 30-180 seconds before the next coat is applied.

[0013] According to a preferred embodiment of the present invention, the water content of the gradient glaze layer corresponding to the semi-dry state is 20%-30%.

[0014] According to a preferred embodiment of the present invention, the pre-firing temperature is 750℃-800℃, and the holding time is 0.5-1 hour; the high-temperature firing temperature is 1280℃-1320℃, and the holding time is 2-3 hours.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention, by setting clay minerals in the glaze system and combining them with a composite organic binder system composed of sodium alginate, polyvinyl alcohol and carboxymethyl cellulose, achieves synergistic regulation of glaze slurry suspension, thixotropy and film-forming properties. This allows the glaze layer to form a relatively stable particle skeleton and organic connection structure during the drying process, thereby giving the glaze layer the toughness and support suitable for continuous scratching in a semi-dry state, reducing the occurrence of porcelain chipping, rough edges and local brittleness during scratching.

[0016] Meanwhile, by setting zirconium oxide and rare earth oxides in the glaze formula and combining them with zirconium silicate to adjust the flow behavior of the glaze layer at high temperature, this invention helps to control the leveling degree of the glaze during the firing process, thereby reducing the situation where the engraved grooves are over-filled at high temperature, and making the groove boundaries clearer and the texture more intact after firing.

[0017] In addition, by using high-temperature stable inorganic pigments and combining them with the above-mentioned glaze system, the glaze can meet the needs of gradient decoration while still taking into account the requirements of micro-scratching for the stability of the glaze edge and the preservation of the texture after firing.

[0018] 2. The glaze composition provided by the present invention includes the above-mentioned gradient glaze, glycerin and water. By controlling the solid content and the amount of glycerin added, it is beneficial to improve the dispersibility, workability and spray adaptability of the glaze, making the obtained glaze more suitable for gradient spraying on the surface of ceramic body, and providing a more stable glaze layer base for subsequent carving and engraving.

[0019] 3. This invention integrates the processes of color separation slurry preparation, gradient spraying, semi-dry engraving, and firing to preserve texture into the same process system for unified design. This allows for better coordination between the gradient color expression and the requirements of the engraving process, thereby improving the problems of existing gradient glazes such as easy chipping during the semi-dry engraving stage, uneven transition in the junction area, and dulling of texture after high-temperature firing. As a result, the ceramic products can still present a clear physical engraving texture while maintaining the gradient color transition effect. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the ceramic product preparation process of the present invention; Figure 2These are partial comparison photos of the gradient boundary area between the finished product of the embodiment of the present invention and the finished product of the prior art after the patterning and firing are completed. Among them, a is the finished product of the prior art and b is the finished product of the embodiment of the present invention. Figure 3 These are partial comparison photos of the carved edges of Example 1 and Comparative Examples 1 and 2 after glazing and drying to a semi-dry state, after carving and engraving, and before pre-firing. In the comparison photos, a is Comparative Example 1, b is Comparative Example 2, and c is Example 1. Figure 4 These are partial comparison photos of the shavings texture of Example 1 and Comparative Examples 4 and 5 after pre-firing and high-temperature firing, where a is Comparative Example 4, b is Comparative Example 5, and c is Example 1. Detailed Implementation

[0021] To make the technical solution, implementation path, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Conventional substitutions or equivalent modifications made by those skilled in the art to the types of raw materials, proportioning ranges, process parameters, and testing methods without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0022] This invention provides a process for preparing ceramic products using a special gradient glaze composition for the carving technique. This process involves continuous control over the gradient spraying overlap stage, the semi-dry carving stage, and the pre-firing and high-temperature firing stages, ensuring that the resulting glaze layer simultaneously possesses good interface transition coordination, semi-dry carving stability, and the ability to retain texture after firing.

[0023] The gradient glaze composition for the special glaze process used in this invention comprises, by weight, the basic glaze components as follows: 35-38 parts feldspar powder, 22-24 parts quartz powder, 16-17 parts kaolin, 6-7 parts dolomite powder, 5-7 parts glass frit powder, 0.8-1.2 parts bentonite and / or palygorskite, 1.0-1.5 parts zirconium oxide, 0.2-0.5 parts cerium oxide and / or lanthanum oxide, 1.0-1.5 parts zirconium silicate, 0.5-0.8 parts sodium alginate, 0.3-0.5 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose; the total amount of high-temperature stable inorganic pigment is 3-5 parts; based on the total mass of the basic glaze components and the high-temperature stable inorganic pigment, the amount of glycerin added is 0.1%-0.3%, and the solid content of the glaze is 45%-50%. When rare earth oxides are used in combination with cerium oxide and lanthanum oxide, the amount of rare earth oxides used is the total amount of both.

[0024] In the aforementioned system, feldspar powder, quartz powder, kaolin, dolomite powder, and glass frit powder collectively constitute the basic inorganic glaze skeleton, providing a suitable firing foundation, melting behavior, and body-glaze matching relationship. Bentonite and / or palygorskite enhance the particle skeleton support capacity of the glaze layer during the drying stage after spraying, facilitating the formation of a structural foundation suitable for continuous needle engraving in a semi-dry state. The composite organic binder system composed of sodium alginate, polyvinyl alcohol, and carboxymethyl cellulose improves the toughness, film-forming properties, and local stress transmission characteristics of the glaze layer in a semi-dry state, making it less prone to chipping, burrs, and breakage during engraving. Zirconia, zirconium silicate, and cerium oxide and / or lanthanum oxide synergistically regulate the melt flow behavior of the glaze layer during the high-temperature firing stage, mitigating excessive leveling and edge blunting of pre-formed microgrooves at high temperatures. High-temperature stable inorganic colorants ensure the color stability of gradient color areas after high-temperature firing. Interface compatibility modifiers are used to improve the dispersion coordination and interface transition state of adjacent color pastes during overlapping spraying, and to reduce water lines, abrupt changes and uneven local particle distribution in the overlap area.

[0025] The interface compatibility modifier described in this invention is preferably one or at least two of polyacrylic acid, polyacrylate, an aqueous solution of polyacrylic acid or polyacrylate, and calcium chloride solution. Preferably, the amount of the interface compatibility modifier added to each color paste is 0.03%-0.30% of the corresponding color paste mass, more preferably 0.05%-0.20%. By adjusting the compatibility of adjacent color pastes separately, the viscosity difference between adjacent color pastes measured by a rotational viscometer at 25°C can be controlled within 10%, preferably within 8%; or the flowability difference between adjacent color pastes can be controlled within 5 mm, preferably within 3 mm. This control helps to form a more continuous and smooth overlap transition zone during overlapping spraying.

[0026] In this invention, the gradient spraying step is completed by layering and overlapping adjacent color pastes. Before spraying, a preset color transition direction is determined according to the decorative area on the surface of the ceramic body, and the color area corresponding to each color paste and the overlapping transition area between adjacent color areas are determined in this direction.

[0027] During spraying, for any two adjacent color pastes, first spray one color paste onto the corresponding color area and atomize it at least two times towards the overlapping transition area, extending its spray range to the overlapping transition area and forming a gradually thinning edge layer within the overlapping transition area; before the first sprayed color paste is completely dry (meaning the surface of the wet glaze layer formed by the first sprayed color paste has not completely lost water and can still form a wet adhesion or interlayer stacking with the subsequently sprayed color paste), spray the other color paste onto the corresponding other color area and atomize it at least two times towards the overlapping transition area, extending the spray range of the other color paste to the overlapping transition area and ensuring that the edge of the other color paste at least partially covers the edge layer formed by the first sprayed color paste within the overlapping transition area; then use at least one of the two adjacent color pastes to perform 1-3 thin-layer sweeping sprays on the overlapping transition area, so that the two adjacent color pastes form a layered overlapping color transition within the overlapping transition area.

[0028] Ultimately, within the transition zone, the amount of one of the two adjacent color pastes applied gradually decreases from one color zone to another, while the amount of the other color paste applied gradually increases in the same direction. This gradual transition is not achieved by directly stirring different color pastes on the surface of the body, but rather through a combination of varying application amounts of adjacent color pastes within the transition zone, edge layer coverage, thin-layer sweeping, layering of wet glazes, and rheological matching after interface adaptation adjustments.

[0029] Spraying can be completed using a pneumatic spray gun. The nozzle diameter can be 0.8-1.2mm, the atomization pressure can be 0.15-0.25MPa, the distance between the nozzle and the ceramic body surface can be 180-250mm, the angle between the spray gun and the ceramic body surface can be 80°-90°, and the travel speed can be 80-120mm / s. The thickness of the wet glaze layer formed by each spray can be 50-100μm, and the thickness of the wet glaze layer formed by thin-layer sweeping spray can be 20-50μm. The total wet film thickness of the gradient glaze layer after spraying can be 220-300μm. The width of the overlap transition zone can be 10-30mm. After each spray, it can be left to stand for 30-180s to allow the surface of the previous wet glaze layer to stabilize before applying the next spray.

[0030] The semi-dry state described in this invention is preferably a gradient glaze layer with a moisture content of 20%-30%, more preferably 22%-28%, and even more preferably 24%-26%. Within this window range, the glaze layer will not experience backflow, edge collapse, or dragging during scribing due to excessive moisture content, nor will it experience brittleness, edge chipping, or flaking due to excessive moisture content.

[0031] The preferred pre-firing temperature of this invention is 750℃-800℃, with a holding time of 0.5-1 hour; the preferred high-temperature firing temperature is 1280℃-1320℃, with a holding time of 2-3 hours. Through the staged treatment of pre-firing and high-temperature firing, the outline of the grooves formed after carving can be initially fixed and organic components can be removed, allowing the glaze to maintain good texture boundaries while maturing and developing color.

[0032] The present invention will be further illustrated below through examples, comparative examples, and test cases.

[0033] Example 1 This embodiment provides a blue gradient glaze with a carved pattern and its preparation and application process. The ceramic body used in this embodiment is a bisque-fired porcelain body with a water absorption rate of 8%-12%. The actual water absorption rate of the bisque-fired porcelain body used in this embodiment is approximately 10.2%. The water absorption rate was determined by immersion weighing. Based on a total of 100.0 parts, the solid glaze formula is as follows: 37.0 parts feldspar powder, 24.0 parts quartz powder, 17.0 parts kaolin, 7.0 parts dolomite powder, 6.0 parts glass frit powder, 1.0 part bentonite, 1.3 parts zirconium oxide, 0.2 parts lanthanum oxide, 4.0 parts cobalt aluminum spinel blue inorganic pigment, 1.3 parts zirconium silicate, 0.6 parts sodium alginate, 0.4 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose.

[0034] Combination Figure 1 The process flow shown below includes the following specific preparation and application steps: S1. Prepare solid components other than blue inorganic pigment and interface compatibility modifier, and add each component into the ball mill; S2. Add 0.2% glycerol and an appropriate amount of water according to the total mass of solids, and mix by ball milling to obtain a basic glaze slurry with a solid content of 45%. S3. Divide the base glaze into two parts. Add 1.5 parts of cobalt aluminum spinel blue inorganic pigment to one part to make a light blue glaze. Add 2.5 parts of cobalt aluminum spinel blue inorganic pigment to the other part to make a dark blue glaze. S4. Using a 10% (w / w) aqueous solution of polyacrylic acid as an interface compatibility modifier, 0.10% (w / w) of the aqueous solution of polyacrylic acid was added to both the light blue and dark blue pastes. After stirring evenly, the mixture was allowed to stand to defoam. Rheological tests were then performed on the two pastes after adjustment. At 25°C, the viscosity of the light blue paste was 820 mPa·s, and the viscosity of the dark blue paste was 860 mPa·s, with a viscosity difference of approximately 4.9%. Before adjustment, the corresponding viscosities were 760 mPa·s and 930 mPa·s, with a viscosity difference of approximately 22.4%. Flowability tests were conducted using flow cups with the same orifice diameter. Before adjustment, the difference in the flow endpoint diameter between the two pastes was 8 mm, which decreased to 2 mm after adjustment. This indicates that interface compatibility adjustment can significantly improve the rheological matching of adjacent pastes. S5. Glazing is done by a pneumatic spray gun. The spray gun is a gravity-type pneumatic spray gun with a nozzle diameter of 1.0mm, an atomization pressure of 0.20MPa, a distance of about 200mm between the nozzle and the surface of the ceramic body, an angle of 80°-90° between the spray gun and the surface of the ceramic body, and a travel speed of about 100mm / s. First, determine the light blue area, dark blue area, and the overlapping transition area between the light blue area and the dark blue area on the surface of the ceramic body. The width of the overlapping transition area is about 20mm. First, spray a light blue paste. Spray the light blue paste three times in the light blue area, and then spray two more atomized coats towards the overlapping transition area to extend the spray range to the overlapping transition area. On the side close to the dark blue area, increase the gun speed and use the edge of the spray to sweep the light blue paste to form a gradually thinning edge layer in the overlapping transition area. Before the light blue paste is completely dry, spray the dark blue paste. Spray the dark blue paste three times in the dark blue area and then spray two more times towards the overlapping transition area, so that the spraying range extends to the overlapping transition area and the edge of the dark blue paste at least partially covers the edge layer formed by the light blue paste in the overlapping transition area. In particular, on the side close to the light blue area, by increasing the gun speed and using the edge of the spray pattern to sweep across, the dark blue paste forms a gradually thinning edge layer in the overlapping transition area. Subsequently, light blue and / or dark blue pigments are applied to the overlapping transition area 1-3 times in thin-layer sweeping sprays. Each spray coat forms a wet glaze layer with a thickness of approximately 50-100 μm. The thickness of the wet glaze layer formed by the thin-layer sweeping spray is approximately 20-50 μm. After each spray coat, the area is left to stand for approximately 60 seconds before the next spray coat is applied. During spraying, the overlap between adjacent spray coats is approximately 30%-50%. After spraying, the total wet film thickness of the gradient glaze layer is approximately 220-260 μm. By gradually thinning the light blue pigment from the light blue area to the dark blue area in the overlapping transition area, and by gradually thinning the dark blue pigment from the dark blue area to the light blue area in the overlapping transition area, combined with thin-layer sweeping spraying, a continuous color transition from light blue to dark blue is formed in the overlapping transition area. S6. Place the sprayed blank in a naturally ventilated environment with a temperature of 20-30℃ and a relative humidity of 50%-70% to dry slowly. During the drying process, take a sample every 5-10 minutes or use a moisture meter to test the moisture content of the glaze layer. When the moisture content of the gradient glaze layer reaches about 25%, proceed to the scribing step. S7. When the gradient glaze is in a semi-dry state, use a hard alloy scribing needle with a tip angle of 30° to continuously scribble out fine grooves along the preset pattern. S8. The engraved blank is sent into the kiln and pre-fired at 780℃ for 0.8 hours. S9. Then, the temperature is raised to 1300℃ and held for 2.5 hours for high-temperature firing. After natural cooling, the finished product is obtained.

[0035] Tests showed that this embodiment performed well in terms of gradient transition, semi-dry scribing stability, and post-firing texture retention. For specific test results, please refer to the test examples described below.

[0036] Example 2 This embodiment provides a green gradient glaze with a carved pattern. Based on a total of 100.0 parts, the solid glaze formula is as follows: 37.0 parts feldspar powder, 22.8 parts quartz powder, 16.0 parts kaolin, 6.0 parts dolomite powder, 7.0 parts glass frit powder, 1.2 parts palygorskite, 1.5 parts zirconium oxide, 0.5 parts cerium oxide, 5.0 parts chromium aluminum spinel green inorganic pigment, 1.5 parts zirconium silicate, 0.8 parts sodium alginate, 0.5 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose. When preparing the glaze slurry, 0.3% glycerol is added according to the total mass of the above solid glaze, and water is added to adjust the solid content of the glaze slurry to 50%. During color separation slurry preparation, the base glaze slurry is divided into two parts. One part is mixed with 2.0 parts chromium aluminum spinel green inorganic pigment to obtain a light green slurry; the other part is mixed with 3.0 parts chromium aluminum spinel green inorganic pigment to obtain a dark green slurry.

[0037] The preparation process is basically the same as in Example 1. The spraying step adopts the same pneumatic spray gun spraying method as in Example 1. The light green paste and dark green paste are sprayed in layers in the order of color transition from light to dark. The difference is that the interface adaptant is calcium chloride solution, and the amount of each color paste added is 0.06% of the corresponding color paste mass. The semi-dry state is controlled with a moisture content of 28%. The pre-firing temperature is 750℃ and held for 1 hour. The high-temperature firing temperature is 1280℃ and held for 3 hours.

[0038] Tests showed that this embodiment also exhibited good gradient transition effect, scratch stability and post-firing texture retention in the application of green gradient glaze. For specific test results, please refer to the test examples described below.

[0039] Example 3 This embodiment provides a purple-blue composite gradient glaze. Based on a total of 100.0 parts, the solid glaze formula is as follows: 38.0 parts feldspar powder, 24.0 parts quartz powder, 17.0 parts kaolin, 7.0 parts dolomite powder, 6.5 parts glass frit powder, 0.8 parts bentonite, 1.0 part zirconium oxide, 0.1 part cerium oxide, 0.1 part lanthanum oxide, 3.5 parts cobalt-aluminum and manganese-aluminum composite spinel inorganic colorant, 1.0 part zirconium silicate, 0.5 parts sodium alginate, 0.3 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose. 0.1% glycerol is added based on the total solid mass, and water is used to adjust the solid content to 48%. In this embodiment, 0.1 parts cerium oxide and 0.1 parts lanthanum oxide are used together as rare earth oxides, with a total rare earth oxide content of 0.2 parts. During the color separation process, the base glaze slurry is divided into two parts. One part is mixed with 1.4 parts of cobalt aluminum and manganese aluminum composite spinel inorganic pigment to obtain a light purple-blue slurry; the other part is mixed with 2.1 parts of cobalt aluminum and manganese aluminum composite spinel inorganic pigment to obtain a dark purple-blue slurry.

[0040] The preparation process is basically the same as in Example 1. The light purple-blue paste and the dark purple-blue paste are sprayed using the layered overlapping spraying method described in Example 1, with the following differences: the semi-dry state is controlled at a moisture content of 22%; the pre-firing temperature is 800℃ and held for 0.5 hours; and the high-temperature firing temperature is 1320℃ and held for 2 hours. This example verifies that when using compound pigments, the system of the present invention can still form a relatively continuous color transition and a relatively stable semi-dry engraving texture.

[0041] Tests showed that this embodiment still exhibits good gradient boundary coordination, semi-dry scratch stability, and post-firing texture retention under the compound pigment system. For specific test results, please refer to the test examples described below.

[0042] Example 4 This embodiment provides a warm brown gradient glaze. Based on a total of 100.0 parts, the solid glaze formula is as follows: 37.8 parts feldspar powder, 23.5 parts quartz powder, 16.8 parts kaolin, 6.8 parts dolomite powder, 6.2 parts glass frit powder, 0.9 parts bentonite, 1.2 parts zirconium oxide, 0.3 parts lanthanum oxide, 4.2 parts iron-chromium brown inorganic pigment, 1.2 parts zirconium silicate, 0.6 parts sodium alginate, 0.3 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose. 0.2% glycerol is added based on the total solid mass. The remaining preparation and application conditions are similar to those in Example 1. During color separation and slurry preparation, the base glaze slurry is divided into two parts. One part is mixed with 1.6 parts of iron-chromium brown inorganic pigment to obtain a light brown slurry; the other part is mixed with 2.6 parts of iron-chromium brown inorganic pigment to obtain a dark brown slurry. Light brown paste and dark brown paste were sprayed using the overlapping spraying method of adjacent color pastes as described in Example 1.

[0043] This embodiment demonstrates that the system of the present invention is also applicable to warm-colored gradient glazes, and can achieve a more natural color transition in the overlapping area, while maintaining a clearer texture boundary after firing.

[0044] Example 5 This embodiment uses the same gradient glaze formula and slurry preparation steps as Example 1. The difference lies in the selection of a dense porcelain body with a water absorption rate of 1.0%-3.0% as the substrate. In this embodiment, the actual water absorption rate of the dense porcelain body used is approximately 2.1%. As a control, the water absorption rate of the bisque-fired porcelain body used in Example 1 is 8%-12%, and the actual water absorption rate is approximately 10.2%. The water absorption rate was determined by immersion weighing. Since the water absorption rate of the dense porcelain body is lower than that of the bisque-fired porcelain body used in Example 1, the ambient wind speed is controlled at a lower level during the drying step in this embodiment, and the standing time is extended until the glaze moisture content reaches approximately 25% before scratching. The remaining color separation slurry preparation, layered overlapping spraying, scratching, and firing conditions are the same as in Example 1. The color separation method in this embodiment is the same as in Example 1, that is, 1.5 parts of cobalt aluminum spinel blue inorganic pigment are added to the light blue slurry, and 2.5 parts of cobalt aluminum spinel blue inorganic pigment are added to the dark blue slurry.

[0045] This embodiment demonstrates that by adapting the drying process, the system of the present invention can also be applied to low water absorption ceramic substrates, and can still obtain relatively stable scratch quality and good post-firing texture retention effect.

[0046] Example 6 This embodiment uses a gradient glaze formulation similar to that of Example 2. The difference lies in dividing the base glaze into three parts: light, medium, and dark. During the spraying stage, adjacent color pastes are sprayed in an overlapping manner to form two overlapping transition zones. When preparing the color pastes, 1.2 parts of chromium aluminum spinel green inorganic pigment are added to the light green paste, 1.6 parts to the medium green paste, and 2.2 parts to the dark green paste, for a total of 5.0 parts. During spraying, the light green paste is sprayed with the medium green paste, and the medium green paste is sprayed with the dark green paste using the overlapping spraying method described in Example 1. The remaining drying, marking, and firing conditions are similar to those in Example 2.

[0047] This embodiment verifies the applicability of the formulation and process of the present invention in multi-segment gradient scenarios, indicating that the present invention is not limited to a two-color gradient system.

[0048] To facilitate comparison with Example 1, unless otherwise specified, Comparative Examples 1-5 and Comparative Example 7 all adopted the same color separation method as Example 1, that is, 1.5 parts of cobalt aluminum spinel blue inorganic pigment were added to the light blue paste, and 2.5 parts of cobalt aluminum spinel blue inorganic pigment were added to the dark blue paste; the spraying, drying, scratching, pre-firing and high-temperature firing conditions were the same as those in Example 1, wherein the spraying method adopted the method of overlapping spraying of adjacent color pastes.

[0049] Comparative Example 1: The formulation and process were the same as in Example 1, but bentonite was not added, and the missing amount was supplemented by feldspar powder. All other conditions remained the same.

[0050] Comparative Example 2: The formulation and process were the same as in Example 1, but sodium alginate and polyvinyl alcohol were not added; only carboxymethyl cellulose was retained as the single component, and the missing portion was supplemented by feldspar powder. All other conditions remained the same.

[0051] Comparative Example 3: The formulation and process were the same as in Example 1, but no interface compatibility modifier was added to the two color pastes after color separation and slurry preparation; instead, they were directly overlapped and sprayed. All other conditions remained the same.

[0052] Comparative Example 4: The formulation and process were the same as in Example 1, but zirconium oxide was not added, and the missing amount was supplemented by feldspar powder. All other conditions remained the same.

[0053] Comparative Example 5: The formulation and process were the same as in Example 1, but lanthanum oxide was not added, and the missing amount was supplemented by feldspar powder. All other conditions remained the same.

[0054] Comparative Example 6: A conventional high-temperature gradient glaze system was used. For ease of comparison, the total amount of pigment remained 4.0 parts, with 1.5 parts of cobalt aluminum spinel blue inorganic pigment added to the light blue paste, and 2.5 parts of cobalt aluminum spinel blue inorganic pigment added to the dark blue paste; however, bentonite and / or palygorskite, sodium alginate, polyvinyl alcohol, and carboxymethyl cellulose, zirconium oxide and lanthanum oxide were not added to the formula, and no interface adaptation adjustment was performed during the process. The remaining basic inorganic components were supplemented by feldspar powder. After spraying, the glaze was scratched in a surface-dry state and fired according to a firing regime similar to that of Example 1.

[0055] Comparative Example 7: The formulation and process were the same as in Example 1, but zirconium silicate was not added, and the missing amount was supplemented by feldspar powder. All other conditions remained the same.

[0056] Observation revealed that Comparative Example 7 exhibited more pronounced rounding and passivation at the groove edges during the firing stage, with a reduction in local groove depth. This indicates that the introduction of zirconium silicate helps to further regulate high-temperature flow behavior and synergistically improves the ability to retain texture after firing.

[0057] In the following test examples, the spraying and scratching processes during sample preparation were completed according to the aforementioned procedures. Moisture content testing, viscosity testing, flowability testing, color difference testing, scratch resistance testing, and three-dimensional morphology testing were all performed using appropriate testing equipment.

[0058] The moisture content of the glaze layer is measured by weighing or by a moisture meter. When using the weighing method, take a glaze layer sample from the same area, record the wet weight m1, dry it at 105℃ to constant weight, and record the dry weight m2. The moisture content is calculated as (m1-m2) / m1×100%.

[0059] The viscosity of adjacent color pastes was measured using a rotational viscometer at 25°C. Before testing, the color pastes were allowed to stand to defoam and then stirred thoroughly. Flowability was tested using flow cups or flow plates with the same orifice diameter, and the diameter of the flow endpoint was recorded.

[0060] The statistical method for the frequency of porcelain chipping is as follows: At least three samples are selected for each group, and five continuous scribing lines are selected for each sample. The statistical length of each scribing line is 100 mm. Under magnified observation conditions, the number of chipping, gaping, or blocky peeling points with an edge length or width of 0.2 mm or more is counted. The frequency of porcelain chipping is calculated using the following formula: Frequency of porcelain chipping = Total number of chipped points / Total statistical length (cm) × 10, in units of times / 10cm.

[0061] The depth-to-width ratio of the grooves after firing was measured using a three-dimensional topography instrument. At least 10 representative grooves were randomly selected from each sample group, and at least 3 cross-sections were taken from each groove. The average depth and average width of the grooves were measured, and the depth-to-width ratio was calculated.

[0062] The maximum abrupt change value of the overall color difference was measured at equal intervals along the overlap transition zone using a colorimeter. The distance between adjacent sampling points was 2 mm. The overall color difference change value of adjacent sampling points was recorded, and the maximum value among them was taken as the maximum abrupt change value of the overall color difference.

[0063] Test Example 1: Verification of Semi-Dry Moisture Content Window To verify the rationality of the semi-dry moisture content window setting, based on the formulation and spraying conditions of Example 1, scribing comparisons were conducted under different moisture content conditions using the same preform, the same cemented carbide scribing needle, the same scribing method, the same load range of 0.8-1.2N, and the same linear velocity range of 25-35mm / s. Each group of samples was tested in triplicate, and the average value was taken. The results are as follows: 1. When the glaze moisture content is about 15%, the resistance to needle insertion increases significantly during the scratching process, and the edges are prone to brittle cracking and blocky chipping, with a chipping frequency of about 3.6 times / 10cm. 2. When the glaze moisture content is about 20%, the engraving condition is significantly improved, but slight dry cracking is still visible in some areas, and the frequency of porcelain chipping is about 0.9 times / 10cm. 3. When the glaze moisture content is about 25%, the scratching resistance is relatively stable, the edge of the groove is relatively neat, and the frequency of porcelain chipping is about 0.3 times / 10cm. 4. When the glaze moisture content is about 30%, continuous scratching can still be performed, but some fine lines will begin to show slight soft collapse in the turning areas, with the frequency of chipping about 0.5 times / 10cm. 5. When the moisture content of the glaze layer is about 35%, the edges of the grooves are prone to backflow during the engraving process, resulting in localized smudging and edge collapse, and a significant deterioration in the preservation of details.

[0064] The above results indicate that controlling the moisture content of the glaze layer during engraving within the range of 20%-30%, especially within the range of 22%-28%, is more conducive to balancing needle insertion stability, edge neatness, and groove retention.

[0065] Test Example 2: Verification of Interface Adaptation and Adjustment Effects To verify the effectiveness of the interface adaptation adjustment steps, Examples 1 and 3 were used as controls. Samples were prepared under the same environmental conditions: a nozzle diameter of 1.0 mm, atomization pressure of 0.20 MPa, a nozzle-to-green surface distance of approximately 200 mm, a gun travel speed of approximately 100 mm / s, an overlap transition zone width of approximately 20 mm, and the viscosity difference, flowability difference, and maximum abrupt change in overall color difference of adjacent color pastes in the overlap zone were tested. Each group of samples was tested in triplicate, and the average value was taken.

[0066] The results show that: 1. Without interface adaptation adjustment, the viscosity difference between adjacent color pastes is about 22.4%, the fluidity difference is about 8mm, and the maximum abrupt change value of the overall color difference in the overlapping area is 0.82. 2. After interface adaptation adjustment, the viscosity difference between adjacent color pastes decreased to 4.9%, the fluidity difference decreased to 2mm, and the maximum abrupt change value of the overall color difference in the overlapping area decreased to 0.12.

[0067] Meanwhile, the overlap area of ​​the unadjusted sample was more prone to visually identifiable water lines and abrupt local transitions, while the overlap area of ​​the adjusted sample showed a more natural transition. These results indicate that the interface adaptation adjustment step helps improve the transition coordination between adjacent pigments during overlapping spraying.

[0068] Test Example 3: Verification of Texture Retention Before and After Burning To verify the improvement effect of this invention on the post-firing texture retention capability, Examples 1, 4, 5, and 7 were used as subjects. The aspect ratio of the grooves before firing and after high-temperature firing were tested for each sample. Ten representative grooves were randomly selected from each group of samples, and three cross-sections were selected from each groove. The average depth and average width of each cross-section were measured using a three-dimensional profilometer, and the groove aspect ratio was calculated and the average value was taken. The texture retention rate was calculated by the following formula: Texture retention rate = Post-firing groove aspect ratio / Pre-firing groove aspect ratio × 100%.

[0069] The test results are as follows: 1. Example 1: Before firing, the groove depth-to-width ratio was 0.81; after firing, the groove depth-to-width ratio was 0.65; the texture retention rate was approximately 80.2%. 2. Comparative Example 4: Before firing, the groove depth-to-width ratio was 0.79; after firing, the groove depth-to-width ratio was 0.30; the texture retention rate was approximately 38.0%. 3. Comparative Example 5: Before firing, the groove depth-to-width ratio was 0.80; after firing, the groove depth-to-width ratio was 0.42; the texture retention rate was approximately 52.5%. 4. Comparative Example 7: Before firing, the groove depth-to-width ratio was 0.80, and after firing, the groove depth-to-width ratio was 0.48, with a texture retention rate of approximately 60.0%.

[0070] The above results indicate that zirconium oxide, rare earth oxides, and zirconium silicate have a synergistic effect on improving texture retention at high temperatures.

[0071] Test Example 4: Comprehensive Performance Test of Representative Samples To objectively evaluate the overall performance of the embodiments and comparative examples of the present invention, Examples 1-3 and Comparative Examples 1-7 were selected as representative samples for testing. Each group of samples was tested in parallel at least three times, preferably five times. The test samples used the same batch of blanks, the same spraying environment, the same scribing tool, the same scribing load, and the same firing regime, and were completed within the same batch. The test results were averaged, and the standard deviation could be recorded simultaneously if necessary. The test items included: 1. Chipping Frequency Test: Under a load of 0.8-1.2N and a linear velocity of 25-35mm / s, continuous scratching is performed in a semi-dry state. At least 3 samples are selected for each group, and 5 continuous scratch lines are selected for each sample. The statistical length of each scratch line is 100mm. Under magnified observation, the number of chipping, notches, or blocky peeling points with an edge length or width of 0.2mm or more is counted. The chipping frequency is calculated as "total number of chipped points / total statistical length (cm) × 10", with the unit being times / 10cm. 2. Scribing resistance difference test: Connect or pre-calibrate a force sensor to the scribing tool, record the dynamic resistance of the scribing needle as it continuously travels across the gradient boundary zone, collect the peak and valley values ​​of resistance within the stable scribing section, and calculate the difference between the two. 3. Post-firing groove depth-to-width ratio test: After the finished product is fired, the cross-section of the groove is measured using a three-dimensional morphology instrument, and the ratio of average depth to average width is calculated; 4. Test for maximum abrupt change in overall color difference: Use a colorimeter to measure the overall color difference between adjacent sampling points at equal intervals along the overlap area path, and record the maximum local color difference step change value.

[0072] The test results are summarized in the table below:

[0073] Based on the above test data and accompanying drawings, the technical effects of the present invention will be specifically explained as follows: Comparative Example 1 with Comparative Example 3 and Comparative Example 6, and in combination Figure 2 . Figure 2 Figure a (Comparative Example 6 process) shows obvious water lines and uneven transition in the gradient boundary area. The data table shows that its color difference abrupt change value is high (0.88). Figure 2 Figure b (process of Example 1) shows a smooth transition with a color difference abrupt change value of 0.12. This result indicates that the interface adaptation adjustment step helps improve the dispersion coordination of adjacent pigments in the overlap area and reduces the problems of water lines and abrupt transitions at the spraying interface.

[0074] Comparative Example 1 with Comparative Example 1 and Comparative Example 2, and in combination Figure 3 During the semi-dry characterization stage, Figure 3 In Figure a (Comparative Example 1, missing bentonite), blocky flaking debris appears at the edge of the trench; Figure 3 In Figure b (Comparative Example 2, lacking sodium alginate and polyvinyl alcohol), the etched edges have many burrs and the etched resistance is extremely poor (0.24N) with significant fluctuations. Figure 3 Figure c (Example 1) shows a smoother etched edge, a reduced chipping frequency of 0.3 times / 10cm, and stable needle insertion resistance. These results indicate that the combination of structure-regulating clay and the composite organic binder system helps improve the stability of semi-dry etched edges and reduces chipping and burrs.

[0075] Comparative Example 1 with Comparative Examples 4 and 5, and in combination Figure 4 After being fired at high temperatures, Figure 4 In Figure a (Comparative Example 4, missing zirconia), the grooves show a more obvious leveling and shallowing phenomenon, with the aspect ratio decreasing to 0.30; Figure 4 In Figure b (Comparative Example 5, lacking lanthanum oxide), the texture boundaries show passivation, and the aspect ratio drops to 0.42; Figure 4 In Figure c (Example 1), the grooves are well preserved, with an aspect ratio of 0.65. This indicates that the combination of zirconium oxide and rare earth oxides helps to reduce excessive leveling during the high-temperature stage, thereby improving the ability to retain texture after firing.

[0076] As can be seen from the comparison between Example 1 and Comparative Example 6, the present invention does not optimize a single component, but improves the key issues of the three stages of gradient transition, semi-dry engraving and post-firing texture preservation through the synergistic combination of the formulation system and process steps.

[0077] The ceramic product preparation process provided by this invention, through the coordinated design of three continuous process stages—gradient spraying overlap, semi-dry scratching, and firing to preserve texture—can better balance the gradient color transition effect, scratching stability, and post-firing texture clarity, and is suitable for gradient spraying and scratching decoration processing on the surface of ceramic blanks.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make various modifications and equivalent substitutions to the technical solutions of the present invention, and such modifications and equivalent substitutions should not depart from the spirit and scope of protection of the present invention.

Claims

1. A process for preparing ceramic products using a special gradient glaze composition for the carving process, characterized in that, Includes the following steps: S1. Prepare the basic glaze components and high-temperature stable inorganic pigments by weight. The basic glaze components include: 35-38 parts feldspar powder, 22-24 parts quartz powder, 16-17 parts kaolin, 6-7 parts dolomite powder, 5-7 parts glass frit powder, 0.8-1.2 parts clay minerals, 1.0-1.5 parts zirconium oxide, 0.2-0.5 parts rare earth oxides, 1.0-1.5 parts zirconium silicate, 0.5-0.8 parts sodium alginate, 0.3-0.5 parts polyvinyl alcohol, and 0.2 parts carboxymethyl cellulose. The total amount of the high-temperature stable inorganic pigments is 3-5 parts. The clay minerals are bentonite and / or palygorskite, and the rare earth oxides are cerium oxide and / or lanthanum oxide. The high-temperature stable inorganic pigments are selected from one or a combination of at least two of spinel-type inorganic pigments and zirconium-coated inorganic pigments. S2, mix the base glaze components with water, and add 0.1%-0.3% glycerol according to the total mass of the base glaze components and the high-temperature stable inorganic pigment. After ball milling or dispersion, a base glaze slurry with a solid content of 45%-50% is obtained. S3, the base glaze is divided into at least two parts, and different types and / or different contents of the high-temperature stable inorganic pigments are added to each part to obtain different color pastes corresponding to adjacent color areas; S4, add an interface adaptor to each adjacent color paste to adapt and adjust the dispersion state of the adjacent color pastes so that the viscosity difference between the adjacent color pastes at 25°C is not greater than 10% and / or the flowability difference is not greater than 5mm. The interface adaptor is selected from one or at least two of polyacrylic acid, polyacrylate, aqueous solution of polyacrylic acid or polyacrylate, and calcium chloride solution. S5, after the interface adaptation adjustment, the various color pastes are sprayed in layers on the surface of the ceramic body in the order of color transition to form a gradient glaze layer with overlapping transition areas. S6, the sprayed ceramic blank is dried so that the gradient glaze layer reaches a semi-dry state suitable for engraving. S7. When the gradient glaze layer is in a semi-dry state, a scribing tool is used to continuously scribble along a preset pattern to form micro-grooves. S8, pre-fire the ceramic blank after it has been engraved; S9 involves firing the pre-fired ceramic blank at high temperature to obtain ceramic products.

2. The process according to claim 1, characterized in that, In step S5, a first color area corresponding to the first color paste and a second color area corresponding to the second color paste are first determined on the surface of the ceramic body, and an overlapping transition area is determined between the first color area and the second color area. The first color paste is first sprayed three times in the first color area, and then atomized and sprayed twice towards the overlapping transition area, extending the spraying range of the first color paste to the overlapping transition area and forming a gradually thinning edge layer within the overlapping transition area. Before the first color paste is completely dry, the second color paste is sprayed three times in the second color area, and then atomized and sprayed twice towards the overlapping transition area, extending the spraying range of the second color paste to the overlapping transition area. The coating extends to the overlapping transition area and forms a gradually thinning edge layer within the overlapping transition area, with the edge of the second color paste at least partially covering the edge layer formed by the first color paste within the overlapping transition area; then, the overlapping transition area is sprayed with the first color paste and / or the second color paste 1-3 times in thin layers, so that the first color paste and the second color paste form a layered and overlapping color transition within the overlapping transition area; and finally, within the overlapping transition area, the amount of the first color paste sprayed gradually decreases along the direction from the first color area to the second color area, while the amount of the second color paste sprayed gradually increases along the same direction.

3. The process according to claim 1, characterized in that, In step S5, a pneumatic spray gun is used for spraying. The nozzle diameter is 0.8-1.2mm, the atomization pressure is 0.15-0.25MPa, the distance between the nozzle and the surface of the ceramic body is 180-250mm, the angle between the spray gun and the surface of the ceramic body is 80°-90°, and the travel speed is 80-120mm / s.

4. The process according to claim 1, characterized in that, In step S5, the thickness of the wet glaze layer formed by each spray is 50-100μm, the thickness of the wet glaze layer formed by thin-layer sweeping is 20-50μm, and the total wet film thickness of the gradient glaze layer after spraying is 220-300μm.

5. The process according to claim 1, characterized in that, In step S5, the width of the overlapping transition zone is 10-30mm.

6. The process according to claim 1, characterized in that, In step S5, after each coat of paint, let it stand for 30-180 seconds before applying the next coat.

7. The process according to claim 1, characterized in that, The gradient glaze layer in the semi-dry state has a moisture content of 20%-30%.

8. The process according to claim 1, characterized in that, The pre-firing temperature is 750℃-800℃, and the holding time is 0.5-1 hour; the high-temperature firing temperature is 1280℃-1320℃, and the holding time is 2-3 hours.

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