Underglaze for sanitary ceramics and method of manufacturing an article using the same

Abstract

This invention relates to the field of sanitary ceramic glaze technology, and discloses a method for preparing a base glaze for sanitary ceramics and products using the same, comprising the following steps: T1) Take a completely dried sanitary ceramic blank, and evenly apply water to the surface of the blank to form a water film; T2) When the surface water film is absorbed, spray a base glaze slurry, repeating the application of the base glaze slurry twice, and let it stand to dry, thus obtaining a blank with a base glaze; T3) When the surface of the sprayed base glaze is dry, spray a top glaze slurry, repeating the application of the top glaze slurry three times, thus obtaining a blank with both a top glaze and a base glaze; T4) Firing to obtain the sanitary ceramic product; the raw materials of the base glaze include: potassium feldspar, quartz powder, kaolin for glaze, zirconium silicate, calcined talc, sodium carboxymethyl cellulose, sodium humate, and water. This method prevents defects such as pinholes, pores, and enlarged pores on the glaze surface, thereby improving the quality of the obtained sanitary ceramic product.

Description

Technical Field

[0001] This invention relates to the field of sanitary ceramic glaze technology, and more particularly to a base glaze for sanitary ceramics and a method for preparing articles using the same. Background Technology

[0002] Based on water absorption rate, sanitary ceramics include VC sanitary ware with a water absorption rate of less than 0.5% and FFC sanitary ware with a water absorption rate of 5-9%.

[0003] With the continuous development of the domestic ceramic industry, the consumption of raw materials for body is very large, and the natural high-quality raw materials are becoming increasingly scarce. The raw materials used in the current technology have high iron and titanium content, resulting in a dark black body after firing, causing the glaze of the product to be dark and have poor whiteness. On the other hand, the raw materials contain impurities such as carbonates, organic matter and mineral iron. These impurities break through the glaze during the product firing process, forming defects such as pinholes, pores and hairline defects.

[0004] Existing technologies typically employ the following methods to improve product quality: 1. Adding more zirconium silicate to the glaze formula to increase its opacity, masking the body color to increase whiteness, thus increasing production costs. 2. Reducing the amount of black clay in the body formula to decrease volatile organic compounds, inevitably resulting in lower product drying strength and higher breakage rates. 3. During kiln firing, extending the firing time of the clay body before 950℃ to enhance oxidation, thereby facilitating the oxidation and removal of volatile organic compounds and carbonates from the clay body.

[0005] During the firing process, the glaze has a certain degree of high-temperature fluidity. The glaze at the corners of the product flows to both sides, causing the glaze thickness at the corners to become thinner, the covering power to become weaker, and the base color of the body to show through, which is different from the surrounding glaze color, forming the so-called "black edge" or "yellow edge" defect. Summary of the Invention

[0006] In view of the above-mentioned shortcomings, the first objective of the present invention is to provide a method for preparing sanitary ceramics, which prevents the occurrence of uneven glaze, reduces the generation of pinholes, pores and enlarged pores, and prevents defects such as "black edges" or "yellow edges" from appearing at the edges of the product.

[0007] The second objective of this invention is to provide a method for preparing a base glaze for sanitary ceramics, so as to ensure that the base glaze has suitable drying strength and firing shrinkage properties, and to match the shrinkage of the base glaze with that of the body during the firing process.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] A method for preparing sanitary ceramics includes the following steps:

[0010] T1) Take a completely dried sanitary ceramic blank and apply water evenly to the surface of the blank to form a water film.

[0011] T2) When the surface water film is absorbed, spray the base glaze slurry, repeat and complete the spraying of the base glaze slurry twice, let it stand and dry, and obtain the clay body sprayed with base glaze.

[0012] T3) When the surface of the sprayed base glaze is dry, spray the top glaze slurry, repeat and complete the three sprayings of the top glaze slurry to obtain a clay body sprayed with both top and base glazes.

[0013] T4) The clay blanks sprayed with top glaze and bottom glaze are placed in a tunnel kiln and fired once to obtain the sanitary ceramic products.

[0014] The raw materials for the base glaze include: potassium feldspar, quartz powder, kaolin for glaze, zirconium silicate, calcined talc, sodium carboxymethyl cellulose, sodium humate, and water.

[0015] Specifically, the raw material composition of the base glaze, calculated by weight percentage, includes: 15-25 wt% potassium feldspar, 30-38 wt% quartz powder, 2-4 wt% wollastonite, 20-30 wt% kaolin for glaze, 3-7 wt% calcined alumina, 5-11 wt% zirconium silicate, and 5-9 wt% calcined talc.

[0016] And the weights of sodium carboxymethyl cellulose, sodium humate, and water, respectively, are 0.4-0.7 wt%, 0.4-0.7 wt%, and 80-90 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc.

[0017] Preferably, in step T2), the thickness of each application of the base glaze slurry is 0.05-0.08 mm;

[0018] The drying time is 16-24 hours.

[0019] Preferably, in step T3), the thickness of each top glaze spray is 0.2-0.3 mm.

[0020] Preferably, in step T4), the firing temperature is 1200-1208℃ and the firing cycle is 15-17 hours.

[0021] Furthermore, the present invention proposes a method for preparing a base glaze for sanitary ceramics, wherein the base glaze is used in the above-described method for preparing sanitary ceramics, comprising the following steps:

[0022] S1) Weigh the raw materials for the base glaze according to the formula, mix potassium feldspar, quartz powder, wollastonite, glaze kaolin, calcined alumina, zirconium silicate and calcined talc evenly and add them to a ball mill, add sodium humate, then add some water, dispersant and a small amount of sodium carboxymethyl cellulose and ball mill together. After testing the fineness, particle size and specific gravity of the first glaze slurry to be qualified, the first glaze slurry is obtained.

[0023] S2) After sieving to remove iron, add the remaining sodium carboxymethyl cellulose, water and dispersant to the first glaze slurry, stir and mix evenly, test the specific gravity, fluidity and drying time of the glaze slurry to ensure they are qualified, then age for 12 hours, sieve, and the base glaze is obtained.

[0024] Preferably, in step S1), the sodium carboxymethyl cellulose, water, and dispersant added are 0.1 wt%, 50-60 wt%, and 0.05-0.10 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc, respectively.

[0025] Preferably, in step S1), the qualified parameters for the fineness, particle size and specific gravity of the glaze slurry are: 0.5-1.2% residue on a 325-mesh sieve, 56-60% residue on a 10-mesh sieve and 1.68-1.72 g / ml, respectively.

[0026] Preferably, in step S2), the stirring time is 30-40 min; the qualified parameters for the specific gravity of the glaze slurry, the fluidity of the glaze slurry, and the drying time of the glaze slurry are 1.40-1.46 g / ml, 270°-310°, and 35-45 min, respectively.

[0027] The beneficial effects of the technical solution of the present invention are as follows: The preparation method of the sanitary ceramics first involves applying a water film to the surface of the clay blank to remove surface dust, fill the surface micropores, increase the surface wettability of the clay blank, and slow down the water absorption rate of the clay blank, thereby facilitating the adhesion of the glaze layer to the green body; then, a base glaze containing kaolin, sodium carboxymethyl cellulose, and sodium humate is used to improve the bonding force and covering effect of the base glaze to the clay blank. This prevents impurities and volatiles in the blank from affecting the glaze surface and avoids the formation of pore defects; it covers the small pores on the blank surface, preventing the glaze material from being absorbed into the pores and causing uneven glaze surface, and preventing air bubbles in the pores from breaking through the surface glaze and generating pinhole defects; and through the multi-stage spraying of the base glaze, it avoids the formation of small holes when air bubbles trapped in the base glaze slurry are expelled, and avoids the formation of pinholes and "watermarks" defects when spraying the surface glaze, thereby improving the quality of the sanitary ceramic products.

[0028] In addition, the present invention adds an appropriate amount of kaolin for glaze to ensure that the base glaze has suitable drying strength and firing shrinkage rate, so that the shrinkage of the base glaze and the body is matched during firing, and the shrinkage defect of the product edge is avoided. Adding an appropriate amount of zirconium silicate can improve the covering effect of the base glaze, ensure that the color of the body does not affect the product quality, and at the same time solve the defects of "black edge" or "yellow edge" at the corner.

[0029] Furthermore, in the proposed method for preparing the base glaze for sanitary ceramics, most of the sodium carboxymethyl cellulose, water, and dispersant are added after ball milling to avoid the breakage of the sodium carboxymethyl cellulose molecular chains at high temperatures, thereby ensuring that the moisturizing performance of the base glaze meets the quality requirements. Detailed Implementation

[0030] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0031] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0033] A method for preparing sanitary ceramics includes the following steps:

[0034] T1) Take a completely dried sanitary ceramic blank and apply water evenly to the surface of the blank to form a water film.

[0035] T2) When the surface water film is absorbed, spray the base glaze slurry, repeat and complete the spraying of the base glaze slurry twice, let it stand and dry, and obtain the clay body sprayed with base glaze.

[0036] T3) When the surface of the sprayed base glaze is dry, spray the top glaze slurry, repeat and complete the three sprayings of the top glaze slurry to obtain a clay body sprayed with both top and base glazes.

[0037] T4) The clay blanks sprayed with top glaze and bottom glaze are placed in a tunnel kiln and fired once to obtain the sanitary ceramic products.

[0038] The raw materials for the base glaze include: potassium feldspar, quartz powder, kaolin for glaze, zirconium silicate, calcined talc, sodium carboxymethyl cellulose, sodium humate, and water.

[0039] Kaolin used in glazes can improve the plasticity and suspension of glazes, enhance their strength, and better match the shrinkage properties of the clay body during firing. This improves the bonding performance between the clay body and the base glaze, preventing cracking of the base glaze at the edges and corners of the product and avoiding glaze shrinkage.

[0040] Sodium carboxymethyl cellulose has thickening, suspending, moisturizing, adsorption and decoction effects. It can improve the surface activity of glaze, improve the dispersibility of each component in the glaze slurry, and keep the glaze slurry in a stable dispersion state. It can effectively improve the water retention of the base glaze slurry, prevent the water in the base glaze slurry from rapidly diffusing into the clay body, and avoid cracking of the clay body due to excessive moisture content. It can effectively regulate the rheological properties of the base glaze slurry, significantly improve the glaze surface strength, prevent the base glaze surface from peeling off, and avoid glaze flow on vertical surfaces, which can lead to glaze accumulation and glaze run-off.

[0041] Sodium humate has degumming and plasticizing properties. Sodium humate molecules combine with clay particles in the clay body through chemical adsorption, which can improve the strength and adhesion of the glaze after glazing, improve the bonding performance of the body and glaze, prevent the body and glaze from separating, and prevent the air bubbles in the pores of the clay body from breaking through the base glaze slurry and forming a "fuzzy" phenomenon during firing, thus avoiding the shrinkage of the base glaze.

[0042] The zirconium silicate it contains has whitening and opacifying properties, which can increase the hiding power of the base glaze.

[0043] Dispersants are used to disperse glaze slurries, dilute the concentration of glaze slurries, reduce the viscosity of glaze slurries, and improve the fluidity of glaze slurries.

[0044] Specifically, the raw material composition of the base glaze, calculated by weight percentage, includes: 15-25 wt% potassium feldspar, 30-38 wt% quartz powder, 2-4 wt% wollastonite, 20-30 wt% kaolin for glaze, 3-7 wt% calcined alumina, 5-11 wt% zirconium silicate, and 5-9 wt% calcined talc.

[0045] And the weights of sodium carboxymethyl cellulose, sodium humate, and water, respectively, are 0.4-0.7 wt%, 0.4-0.7 wt%, and 80-90 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc.

[0046] The base glaze formula contains at least 20% kaolin, 0.4-0.7% sodium carboxymethyl cellulose, and 0.4-0.7% sodium humate. This allows the base glaze to cover the small pores on the body surface, preventing pinhole defects. It also prevents bubbles formed by volatiles in the body from escaping from the glaze surface, avoiding pore defects. The resulting base glaze has strong adhesion to the body, preventing glaze cracking at the edges of the body during drying and avoiding glaze shrinkage defects on the surface glaze.

[0047] In addition, the base glaze has high refractoriness and covering power, which can prevent the glaze at the corners of the product from flowing at high temperatures, thus avoiding the phenomenon of "black edges" or "yellow edges".

[0048] Preferably, in step T2), the thickness of each application of the base glaze slurry is 0.05-0.08 mm;

[0049] The drying time is 16-24 hours.

[0050] To increase the moisture retention of the base glaze, a large amount of sodium carboxymethyl cellulose is added to the base glaze. The good moisture retention of the base glaze makes the surface of the clay body with the base glaze absorb water slowly. If the top glaze is sprayed immediately after the base glaze is applied, the "glaze run" defect is likely to occur.

[0051] Let the clay blank with the base glaze stand and dry for 16-24 hours to allow the surface of the clay blank with the base glaze to dry. When the top glaze is sprayed, the moisture in the top glaze can be quickly absorbed into the clay blank, preventing the "glaze run" defect from occurring when the top glaze is sprayed.

[0052] Process parameters for base glaze spraying: glaze tank pressure is 0.3 MPa, spraying pressure is 0.1-0.15 MPa, and spraying flow rate is 230-270 ml / 30 sec.

[0053] Preferably, in step T3), the thickness of each top glaze spray is 0.2-0.3 mm.

[0054] Because spray glaze atomizes the glaze using high-pressure air, a large amount of air is trapped in the glaze slurry. If the glaze is sprayed to the specified thickness in one go, the air bubbles in the glaze cannot be expelled in time, resulting in dense small pores in the glaze. If the melting time is insufficient during firing, the glaze will solidify before it can fill the small pores, leaving many "pinholes" on the glaze surface.

[0055] In addition, if the glaze is sprayed to the specified thickness in one go, the undried glaze will produce water ripples under the blowing of compressed air from the nozzle, which will also cause uneven glaze surface defects in the fired product.

[0056] The raw material composition of the glaze, calculated by weight percentage, is as follows: potassium feldspar 22-26 wt%, quartz powder 26-32 wt%, calcined zinc oxide 2-4 wt%, calcite 8-10 wt%, dolomite 2-3 wt%, wollastonite 9-12 wt%, glaze kaolin 2-5 wt%, calcined kaolin 0-5 wt%, calcined alumina 2-4 wt%, zirconium silicate 7-13 wt%, barium carbonate 0-1 wt%, frit 2-3 wt%, Jiangxi lithium porcelain stone 0-5 wt%, and calcined talc 0-2 wt%.

[0057] Process parameters for surface glaze spraying: glaze tank pressure is 0.3 MPa, glaze spraying pressure is 0.3-0.45 MPa, and glaze spraying flow rate is 540-580 ml / 30 sec.

[0058] In practical applications, existing surface glazes can be used as the surface glaze, and it can be applied by following the above operating steps and process parameters.

[0059] Preferably, in step T4), the firing temperature is 1200-1208℃ and the firing cycle is 15-17 hours.

[0060] It should be noted that the firing temperatures mentioned above refer to the maximum temperature of the kiln.

[0061] Furthermore, the present invention proposes a method for preparing a base glaze for sanitary ceramics, wherein the base glaze is used in the above-described method for preparing sanitary ceramics, comprising the following steps:

[0062] S1) Weigh the raw materials for the base glaze according to the formula, mix potassium feldspar, quartz powder, wollastonite, glaze kaolin, calcined alumina, zirconium silicate and calcined talc evenly and add them to a ball mill, add sodium humate, then add some water, dispersant and a small amount of sodium carboxymethyl cellulose and ball mill together. After testing the fineness, particle size and specific gravity of the first glaze slurry to be qualified, the first glaze slurry is obtained.

[0063] S2) After sieving to remove iron, add the remaining sodium carboxymethyl cellulose, water and dispersant to the first glaze slurry, stir and mix evenly, test the specific gravity, fluidity and drying time of the glaze slurry to ensure they are qualified, then age for 12 hours, sieve, and the base glaze is obtained.

[0064] During the ball milling process of the base glaze, only a portion of sodium carboxymethyl cellulose should be added; otherwise, the grinding efficiency will be affected, and the ball milling time will need to be increased.

[0065] In addition, adding a large amount of sodium carboxymethyl cellulose will make the glaze slurry viscous, have poor dispersibility, and cause severe heat generation; and the molecular chains of sodium carboxymethyl cellulose will break at high temperatures, which will lead to the loss of the moisturizing properties of the glaze.

[0066] Preferably, in step S1), the sodium carboxymethyl cellulose, water, and dispersant added are 0.1 wt%, 50-60 wt%, and 0.05-0.10 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc, respectively.

[0067] In the above steps, sodium polyacrylate dispersant can be added appropriately to dilute the concentration of the glaze slurry, reduce its viscosity, and improve its fluidity.

[0068] Preferably, in step S1), the qualified parameters for the fineness, particle size and specific gravity of the glaze slurry are: 0.5-1.2% residue on a 325-mesh sieve, 56-60% residue on a 10-mesh sieve and 1.68-1.72 g / ml, respectively.

[0069] The particle size of the glaze slurry was determined using a laser particle size analyzer.

[0070] Preferably, in step S2), the stirring time is 30-40 min; the qualified parameters for the specific gravity of the glaze slurry, the fluidity of the glaze slurry, and the drying time of the glaze slurry are 1.40-1.46 g / ml, 270°-310°, and 35-45 min, respectively.

[0071] Aging and sieving: The glaze slurry is aged for 12 hours to dissolve the sodium carboxymethyl cellulose particles in the glaze slurry and fully homogenize it, and then it is sieved through a 140-160 mesh sieve.

[0072] After the glaze slurry is sieved, its parameters are tested and found to be qualified. When packaging, it is sealed with plastic film to prevent moisture evaporation and stored in an air-conditioned room at 21-25℃ until use.

[0073] This invention uses a 100ml specific gravity bottle, a torsion viscometer, and a 50mm diameter stainless steel ring to determine the specific gravity, fluidity, and drying time of the glaze slurry.

[0074] Sanitary ware has a complex, multi-faceted, three-dimensional structure. When spraying a flat area, glaze particles in the excessively atomized edges can drift to other areas. The moisture in these glaze particles is quickly absorbed by the completely dried clay body, causing powdering and creating a "false spray" phenomenon. When the base glaze is sprayed onto these areas, the powdery glaze particles prevent the sprayed glaze from adhering to the surface of the clay body, resulting in glaze separation and, after firing, glaze shrinkage defects. This necessitates that the base glaze has excellent moisture retention properties, preventing the moisture in the glaze particles in these excessively atomized edges from quickly diffusing into the clay body, thus keeping the surface of the glaze particles moist and preventing powdering.

[0075] This invention uses the glaze slurry drying time index to represent this aspect of the performance of the base glaze slurry. It refers to the time taken from the application of the glaze slurry to the surface of the clay body until the water film on the glaze slurry surface dries under specified experimental conditions. The specific method for determining the drying time is as follows: a 50mm diameter stainless steel ring is placed on the dried experimental clay body, and 5ml of glaze slurry is injected into the central area of ​​the ring using a syringe. The time it takes for the surface water film in the central area of ​​the ring to completely dry is observed.

[0076] Examples 1-3 and Comparative Examples 1-4

[0077] 1. Based on the raw material ratios listed in Table 1, the base glazes for each embodiment and comparative example were prepared according to the following process parameters and steps:

[0078] S1) Weigh the raw materials for the base glaze according to the formula, mix potassium feldspar, quartz powder, wollastonite, glaze kaolin, calcined alumina, zirconium silicate and calcined talc evenly and add them to a ball mill, add sodium humate, then add some water, dispersant and a small amount of sodium carboxymethyl cellulose and ball mill together. After testing the fineness, particle size and specific gravity of the first glaze slurry to be qualified, the first glaze slurry is obtained.

[0079] S2) After sieving to remove iron, add the remaining sodium carboxymethyl cellulose, water and dispersant to the first glaze slurry, stir and mix evenly, test the specific gravity, fluidity and drying time of the glaze slurry to ensure they are qualified, then age for 12 hours, sieve, and the corresponding example or comparative example of the base glaze is obtained.

[0080] In step S1), the sodium carboxymethyl cellulose, water, and dispersant added are 0.1 wt%, 50-60 wt%, and 0.05-0.10 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc, respectively.

[0081] In step S1), the acceptable parameters for the fineness, particle size, and specific gravity of the glaze slurry are as follows: 0.5-1.2% residue on a 325-mesh sieve, 56-60% residue on a 10-mesh sieve, and 1.68-1.72 g / ml, respectively.

[0082] In step S2), the stirring time is 30-40 min; the qualified parameters for the specific gravity of the glaze slurry, the fluidity of the glaze slurry, and the drying time of the glaze slurry are 1.40-1.46 g / ml, 270°-310°, and 35-45 min, respectively.

[0083] 2. Using the base glazes obtained in the above-described embodiments or comparative examples, prepare the corresponding sanitary ceramics according to the following steps:

[0084] T1) Take a completely dried sanitary ceramic blank and apply water evenly to the surface of the blank to form a water film.

[0085] T2) When the surface water film is absorbed, spray the base glaze slurry, repeat and complete the spraying of the base glaze slurry twice, let it stand and dry, and obtain the clay body sprayed with base glaze.

[0086] T3) When the surface of the sprayed base glaze is dry, spray the top glaze slurry, repeat and complete the three sprayings of the top glaze slurry to obtain a clay body sprayed with both top and base glazes.

[0087] T4) The clay blanks sprayed with top glaze and bottom glaze are placed in a tunnel kiln and fired once to obtain the sanitary ceramic products.

[0088] In step T2), the thickness of each application of the base glaze slurry is 0.05-0.08 mm;

[0089] Process parameters for base glaze spraying: glaze tank pressure is 0.3 MPa, spraying pressure is 0.1-0.15 MPa, spraying flow rate is 230-270 ml / 30 sec; drying time is 16-24 hours.

[0090] In step T3), the thickness of each top glaze spray is 0.2-0.3 mm; the process parameters for top glaze spraying are: glaze tank pressure is 0.3 MPa, glaze spraying pressure is 0.3-0.45 MPa, and glaze spraying flow rate is 540-580 ml / 30 sec.

[0091] The raw material composition of the glaze, calculated by weight percentage, is as follows: potassium feldspar 25wt%, quartz powder 28wt%, calcined zinc oxide 2wt%, calcite 8wt%, dolomite 2wt%, wollastonite 9wt%, glaze kaolin 2wt%, calcined kaolin 5wt%, calcined alumina 2wt%, zirconium silicate 7wt%, barium carbonate 1wt%, frit 2wt%, Jiangxi lithium porcelain stone 5wt%, and calcined talc 2wt%.

[0092] In step T4), the firing temperature is 1200-1208℃ and the firing cycle is 15-17 hours.

[0093] 3. The appearance quality of the base glaze and top glaze surfaces of each embodiment and comparative example was inspected by visual inspection to observe whether there were defects such as uneven glaze surface, pores, "powdering", "water marks", glaze shrinkage or pinholes. The inspection results are shown in Table 1.

[0094] Table 1. Raw material ratios and test results for each embodiment and comparative example.

[0095]

[0096]

[0097] As can be seen from the table above, using the base glaze slurry of this technical solution in Examples 1-3 can reduce glaze defects and improve the quality of sanitary ceramic products.

[0098] By comparing Examples 1-3 and Comparative Examples 1-4, it can be seen that: when the content of kaolin in the raw material components exceeds the range specified in the technical solution, the base glaze will have uneven surface, pinholes, edge shrinkage, and "watermark" defects due to excessive strength and shrinkage; when the content of sodium carboxymethyl cellulose in the raw material components exceeds the range specified in the technical solution, the base glaze will have "powdering" due to insufficient moisture retention, resulting in glaze shrinkage defects; when the content of sodium humate in the raw material components exceeds the range specified in the technical solution, the base glaze will have uneven surface, "fuzzing" defects, resulting in pinholes and glaze shrinkage defects.

[0099] In summary, the preparation method of the sanitary ceramics of the present invention involves first applying a water film to the surface of the clay blank to remove surface dust, fill tiny pores, increase surface wettability, and slow down water absorption, thus facilitating glaze adhesion. Then, a base glaze containing kaolin, sodium carboxymethyl cellulose, and sodium humate is used to enhance its adhesion and covering effect on the clay blank. This prevents impurities and volatiles in the blank from affecting the glaze surface, avoiding pore defects; it covers small air bubbles on the blank surface, preventing glaze from being absorbed into these pores and causing unevenness; it also prevents air bubbles in the pores from breaking through the surface glaze, resulting in pinhole defects. Furthermore, the multi-stage spraying of the base glaze prevents air bubbles trapped in the glaze slurry from forming small holes during expulsion, thus avoiding pinholes and "watermarks" during the application of the surface glaze, thereby improving the quality of the resulting sanitary ceramic products.

[0100] In addition, the present invention adds an appropriate amount of kaolin for glaze to ensure that the base glaze has suitable drying strength and firing shrinkage rate, so that the shrinkage of the base glaze and the body is matched during firing, and the shrinkage defect of the product edge is avoided. Adding an appropriate amount of zirconium silicate can improve the covering effect of the base glaze, ensure that the color of the body does not affect the product quality, and at the same time solve the defects of "black edge" or "yellow edge" at the corner.

[0101] Furthermore, in the preparation method of the base glaze for sanitary ceramics proposed in this invention, most of the sodium carboxymethyl cellulose, water, and dispersant are added after ball milling to avoid the breakage of the molecular chains of sodium carboxymethyl cellulose at high temperatures, thereby ensuring that the moisturizing performance of the base glaze meets the quality requirements.

[0102] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing sanitary ceramics, characterized in that, Includes the following steps: T1) Take a completely dried sanitary ceramic blank and apply water evenly to the surface of the blank to form a water film. T2) When the surface water film is absorbed, spray the base glaze slurry, repeat and complete the spraying of the base glaze slurry twice, let it stand and dry, and obtain the clay body sprayed with base glaze. T3) When the surface of the sprayed base glaze is dry, spray the top glaze slurry, repeat and complete the three sprayings of the top glaze slurry to obtain a clay body sprayed with both top and base glazes. T4) The clay blanks sprayed with top glaze and bottom glaze are placed into a tunnel kiln and fired once to obtain the sanitary ceramic products. The raw material composition of the base glaze, calculated by weight percentage, includes: 15-25 wt% potassium feldspar, 30-38 wt% quartz powder, 2-4 wt% wollastonite, 20-30 wt% kaolin for glaze, 3-7 wt% calcined alumina, 5-11 wt% zirconium silicate, and 5-9 wt% calcined talc; And the weights of sodium carboxymethyl cellulose, sodium humate, and water, respectively, are 0.4-0.7 wt%, 0.4-0.7 wt%, and 80-90 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc.

2. The method for preparing sanitary ceramics according to claim 1, characterized in that, In step T2), the thickness of each application of the base glaze slurry is 0.05-0.08 mm; The drying time is 16-24 hours.

3. The method for preparing sanitary ceramics according to claim 1, characterized in that, In step T3), the thickness of each top glaze spray is 0.2-0.3 mm.

4. The method for preparing sanitary ceramics according to claim 1, characterized in that, In step T4), the firing temperature is 1200-1208℃ and the firing cycle is 15-17 hours.

5. A method for preparing a base glaze for sanitary ceramics, characterized in that, The base glaze is used in the preparation method of the sanitary ceramics according to any one of claims 1-4, comprising the following steps: S1) Weigh the raw materials for the base glaze according to the formula, mix potassium feldspar, quartz powder, wollastonite, glaze kaolin, calcined alumina, zirconium silicate and calcined talc evenly and add them to a ball mill, add sodium humate, then add some water, dispersant and a small amount of sodium carboxymethyl cellulose and ball mill together. After testing the fineness, particle size and specific gravity of the first glaze slurry to be qualified, the first glaze slurry is obtained. S2) After sieving to remove iron, add the remaining sodium carboxymethyl cellulose, water and dispersant to the first glaze slurry, stir and mix evenly, test the specific gravity, fluidity and drying time of the glaze slurry to ensure they are qualified, then age for 12 hours, sieve, and the base glaze is obtained.

6. The method for preparing the base glaze for sanitary ceramics according to claim 5, characterized in that, In step S1), the sodium carboxymethyl cellulose, water, and dispersant added are 0.1 wt%, 50-60 wt%, and 0.05-0.10 wt% of the total weight of potassium feldspar, quartz powder, wollastonite, kaolin for glaze, calcined alumina, zirconium silicate, and calcined talc, respectively.

7. The method for preparing the base glaze for sanitary ceramics according to claim 5, characterized in that, In step S1), the qualified parameters for the fineness, particle size and specific gravity of the glaze slurry are as follows: 0.5-1.2% residue on 325 mesh sieve, 56-60% on 10u sieve and 1.68-1.72 g / ml.

8. The method for preparing the base glaze for sanitary ceramics according to claim 5, characterized in that, In step S2), the stirring time is 30-40 min; the qualified parameters for the specific gravity of the glaze slurry, the fluidity of the glaze slurry, and the drying time of the glaze slurry are 1.40-1.46 g / ml, 270°-310°, and 35-45 min, respectively.

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