Durable earthen pot glaze slurry and earthen pot glazing and firing method

Abstract

The invention discloses durable earthenware pot glaze slurry and an earthenware pot glazing and firing method. The earthenware pot glaze slurry is prepared from dihydrogen phosphate intercalated hydrotalcite, kaolin, potassium feldspar, borax, magnesium oxide and water. According to the invention, dihydrogen phosphate intercalated hydrotalcite is used as a main material for preparing the earthen pot glaze for the first time, and a compact and smooth specially-made glaze surface is prepared by utilizing the bonding assisting effect of an aluminum dihydrogen phosphate binder in the sintering process and specially-made acidic pores in the sintering process and matching with a specially-made salt boiling process; the glaze is soft and moist in color, smooth and compact in hand feeling, durable and resistant to dry burning, has the dry burning resistance and health care value of a marmite, and has wide market application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic casserole manufacturing, in particular to a durable casserole glaze slurry and a casserole glazing and firing method. Background Art

[0002] Traditional casserole glaze slurries usually use quartz, feldspar, etc. as the main raw materials. Although they can provide certain surface protection and aesthetic effects, they still have the following shortcomings:

[0003] The color is dark yellow, lacking softness and polish;

[0004] The feel is not smooth enough and the user experience is poor;

[0005] The durability is low and the glaze is prone to peeling or wear after long-term use;

[0006] It lacks health-care functions and cannot meet the needs of modern consumers for health-preserving casseroles. Summary of the Invention

[0007] The purpose of the present invention is to solve the shortcomings of the prior art and to improve the durability, appearance, texture and health care function of the casserole, and to propose a durable casserole glaze slurry and a casserole glaze firing method.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a durable casserole glaze slurry comprises the following steps:

[0010] S1. Raw material pretreatment:

[0011] Dihydrogen phosphate intercalated hydrotalcite, kaolin, potassium feldspar and borax were sieved through 50 meshes to remove large particles of impurities;

[0012] S2. Mixing and stirring:

[0013] Add the above raw materials into the blender according to the proportion, add appropriate amount of water, and stir until uniform;

[0014] S3, Filtering:

[0015] Filter the stirred glaze slurry through a 150-mesh sieve to remove easily sedimentable impurities;

[0016] S4. Adjust viscosity and color:

[0017] Adjust the viscosity of the glaze slurry as needed to ensure it is suitable for glazing operations;

[0018] Colorants can be added to adjust the color to obtain a durable casserole glaze slurry product.

[0019] Preferably, the colorant includes one or more of iron oxide, manganese oxide, copper oxide and chromium oxide.

[0020] The present invention first proposes a durable casserole glaze slurry, comprising the following components in parts by weight:

[0021] 20-30 parts of dihydrogen phosphate intercalated hydrotalcite;

[0022] 30-40 parts of kaolin;

[0023] 15-25 parts of potassium feldspar;

[0024] 5-10 parts of borax;

[0025] 3-8 parts of magnesium oxide;

[0026] The rest is water, which is used to adjust the viscosity of the glaze; by adjusting the formula, the surface color of the casserole is changed from the traditional dark yellow to light yellow, and the visual effect is softer and more moist.

[0027] Hydrotalcite: The addition of talcum powder not only improves the fluidity of the glaze slurry, but also gives the surface of the casserole a smoother feel, while enhancing the polishing effect of the glaze; at the same time, the introduction of magnesium in talcum powder enhances the chemical stability of the glaze and gives the casserole certain health functions, such as releasing trace magnesium ions, which helps to improve cooking effects and health functions; at the same time, quartz and feldspar are removed: by removing quartz and feldspar in the traditional formula, the brittleness of the glaze is reduced and the durability of the casserole is improved.

[0028] The preparation process of the dihydrogen phosphate intercalated hydrotalcite is as follows:

[0029] 1) Preparation of hydrotalcite (MgAl-COy-LDHs) precursor:

[0030] Weigh Mg(NO3)2·6H2O and Al(NO3)·9H2O, dissolve them in deionized water to prepare a mixed salt solution, and dissolve Na2CO3 and NaOH in deionized water to prepare a mixed alkaline solution with the same volume as the mixed salt solution;

[0031] The mixed salt solution and the mixed alkali solution were added to the rotating liquid film reactor at the same speed for nucleation, and then the nucleation slurry was crystallized at reflux temperature for 6 hours;

[0032] The solid precipitate obtained was centrifuged and then washed with deionized water until the pH value was 7 to obtain a wet cake, i.e., a hydrotalcite precursor;

[0033] 2) Dihydrogen phosphate intercalation treatment:

[0034] The wet filter cake obtained in 1) and deionized water were mixed in a weight ratio of 1:2 to form a slurry. Under nitrogen protection and stirring, a NaH2PO4·2H20 aqueous solution was slowly added to the slurry. The pH of the system was adjusted to 4.5±0.5 with a dilute HNO3 solution and refluxed for 1 hour. The product was thoroughly washed with deionized water to a pH of 7, and then dried to obtain a dihydrogen phosphate intercalated hydrotalcite product (MgAl-H2PO4-LDHs).

[0035] Preferably, in 1), the molar ratio of Mg to Al in the mixed salt solution is 2:1, the molar ratio of Na2CO3 to Al(NO3)·9H2O in the mixed alkali solution is 1:1, and the molar ratio of NaOH to Al(NO3)·9H2O is 1.6:1.

[0036] Preferably, the weight concentration of the NaH2PO4·2H20 aqueous solution in 2) is 12 wt%.

[0037] The present invention also proposes the aforementioned

[0038] The present invention also provides a method for glazing and firing a casserole, wherein the durable casserole glaze slurry product prepared by the above-mentioned preparation method comprises the following steps:

[0039] a. Glazing process:

[0040] ① Clean the surface of the casserole: Make sure there is no oil or dust on the surface of the casserole;

[0041] ②Multi-layer glazing: Use dipping or spraying method to apply glaze slurry in 2-3 times, and let it dry after each application;

[0042] ③ Drying: Place the glazed casserole in a ventilated place to dry naturally or in a low-temperature oven;

[0043] b. Firing process:

[0044] ④ Preheating stage: Heat to 150℃ at a heating rate of 5℃ / min and keep warm for 30 minutes; at around 150℃, dihydrogen phosphate reacts with aluminum hydroxide in the hydrotalcite structure to produce aluminum dihydrogen phosphate with bonding effect;

[0045] ⑤ Holding stage: Heating at a rate of 100℃ / h to 400℃ and holding for 2h; at around 400℃, aluminum dihydrogen phosphate melts and penetrates into all parts of the glaze and the pores of the casserole, forming a continuous phosphate film, which makes the glaze and the casserole tightly bonded and makes the glaze structure denser, making it less likely to stick to the pot;

[0046] Firing stage: The temperature is raised to 1100°C at a rate of 150°C / h and held at this temperature for 2 hours. After reaching 1100°C, the components are dehydrated, and in particular, the phosphate membrane connecting the components is sintered, producing an acidic porous glaze with a high phosphorus content (possibly phosphorus oxides of various valence states, accounting for 3.2-4.5% of the total weight of the glaze). These acidic pores have the function of adsorbing alkalis, salts, and various metal ions, especially sodium and potassium ions. They have high adsorption capacity and can be used in conjunction with the casserole pot opening process to produce high-melting-point components such as sodium hydrogen phosphate or potassium hydrogen phosphate, thereby improving the pot's structural strength.

[0047] ⑦ Cooling stage: Cool naturally to room temperature to ensure that the glaze is tightly bonded to the casserole body to obtain a glazed casserole product.

[0048] Based on the acidic pore characteristics of the glazed casserole product obtained by the aforementioned casserole glazing and firing method, the present invention also provides a method for opening a special casserole, comprising the following steps:

[0049] c. Acid immersion: The glazed casserole product is completely immersed in a white vinegar solution having an acetic acid concentration of 15-20wt% by weight for 2-3h;

[0050] d. Cook with salt: After soaking, add a casserole with a weight concentration of 15-20wt% sodium chloride solution, open the lid and bring to a boil over high heat (large, medium and low heat on a household gas stove, for example), close the lid, and simmer for 2-3h;

[0051] e. Fire baking: Pour out the sodium chloride solution in the casserole and dry bake the casserole with a high flame (high-fire stove in a restaurant) or acetylene-air combustion flame. Salt particles will adhere to the inner wall of the casserole, gradually melt, and eventually be completely absorbed by the glaze.

[0052] f. Water Washing: When no salt particles or molten salt are visible, cool the casserole, add water, bring to a boil, discard the water, add water again, bring to a boil, discard the water, and then cool to dry. This will create a dry-burning, self-opening casserole. By utilizing the pores of sodium chloride and acidic phosphoric acid, high-melting-point sodium hydrogen phosphate or sodium phosphate is produced under high-temperature flame burning. This structure further densifies the glaze surface and allows it to penetrate into the sand mold structure, improving the structural stability of the casserole.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. This invention uses dihydrogen phosphate intercalated hydrotalcite as the main ingredient for preparing casserole glaze slurry for the first time. The auxiliary bonding effect of the aluminum dihydrogen phosphate binder during the sintering process, the specially prepared acidic pores during the sintering process, and the special salt boiling process can produce a dense and smooth special glaze surface, significantly improving the dry-burning resistance of the casserole.

[0055] 2. In addition to the optimization of ingredients, the present invention also has the following advantages in terms of process:

[0056] 1) The glaze slurry preparation process was optimized, including raw material pretreatment, mixing, and filtration steps to ensure the uniformity and stability of the glaze slurry.

[0057] 2) The glazing method has been improved, and multi-layer glazing technology has been adopted to ensure that the glaze surface is evenly covered and has moderate thickness.

[0058] 3) The firing process has been optimized, and through segmented temperature control, the glaze is ensured to be closely integrated with the casserole body, thereby improving durability.

[0059] 4) By utilizing the acidic pores formed by firing dihydrogen phosphate intercalated hydrotalcite, combined with an open-pot process of acid leaching, salt boiling, fire roasting, and water washing, and utilizing the pores of sodium chloride and acidic phosphoric acid, high-melting-point sodium hydrogen phosphate or sodium phosphate is produced under high-temperature flame burning. This structure can further densify the glaze surface and can penetrate into the sand mold structure of the casserole, thereby improving the structural stability of the casserole.

[0060] 3. The present invention uses a glaze slurry formula and preparation process, and combines it with the glaze firing and pot opening process to produce a new type of glazed sand pot with soft color, smooth and dense feel, durability and resistance to dry firing. It has both the performance and added value of a sand pot and has broad market application prospects. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0062] 1. Preparation of a durable casserole glaze slurry

[0063] 1. Preparation of dihydrogen phosphate intercalated hydrotalcite:

[0064] 1) Preparation of hydrotalcite (MgAl-COy-LDHs) precursor:

[0065] Weigh Mg(NO3)2·6H2O and Al(NO3)·9H2O, dissolve them in deionized water to prepare a mixed salt solution, and dissolve Na2CO3 and NaOH in deionized water to prepare a mixed alkaline solution with the same volume as the mixed salt solution;

[0066] The mixed salt solution and the mixed alkali solution were added to the rotating liquid film reactor at the same speed for nucleation, and then the nucleation slurry was crystallized at reflux temperature for 6 hours;

[0067] The solid precipitate obtained was centrifuged and then washed with deionized water until the pH value was 7 to obtain a wet cake, i.e., a hydrotalcite precursor;

[0068] 2) Dihydrogen phosphate intercalation treatment:

[0069] The wet filter cake obtained in 1) and deionized water were mixed in a weight ratio of 1:2 to form a slurry. Under nitrogen protection and stirring, a NaH2PO4·2H20 aqueous solution was slowly added to the slurry. The pH of the system was adjusted to 4.5±0.5 with a dilute HNO3 solution and refluxed for 1 hour. The product was thoroughly washed with deionized water to a pH of 7, and then dried to obtain a dihydrogen phosphate intercalated hydrotalcite product (MgAl-H2PO4-LDHs).

[0070] 1), the molar ratio of Mg to Al in the mixed salt solution is 2:1, the molar ratio of Na2CO3 to Al(NO3)·9H2O in the mixed alkali solution is 1:1, and the molar ratio of NaOH to Al(NO3)·9H2O is 1.6:1.

[0071] 2) The weight concentration of the NaH2PO4·2H20 aqueous solution is 12 wt%.

[0072] 2. Glaze slurry preparation:

[0073] S1. Raw material pretreatment:

[0074] Dihydrogen phosphate intercalated hydrotalcite, kaolin, potassium feldspar and borax were sieved through 50 meshes to remove large particles of impurities;

[0075] S2. Mixing and stirring:

[0076] Add the above raw materials into the blender according to the proportion, add appropriate amount of water, and stir until uniform;

[0077] S3, Filtering:

[0078] Filter the stirred glaze slurry through a 150-mesh sieve to remove easily sedimentable impurities;

[0079] S4. Adjust viscosity and color:

[0080] Adjust the viscosity of the glaze slurry as needed to ensure it is suitable for glazing operations;

[0081] Colorant (accounting for 3% of the total weight of the slurry) can be added to adjust the color to obtain a durable casserole glaze slurry product.

[0082] The colorant includes one or more of iron oxide, manganese oxide, copper oxide and chromium oxide.

[0083] The specific formula is shown in Table 1 below:

[0084] Table 1. Durable casserole glaze slurry formulation

[0085]

[0086] 2. Firing:

[0087] The present invention also provides a method for glazing and firing a casserole, using the durable casserole glaze slurry products obtained in Examples 1-7 and Comparative Example 1, comprising the following steps:

[0088] a. Glazing process:

[0089] ① Clean the surface of the casserole: Make sure there is no oil or dust on the surface of the casserole;

[0090] ②Multi-layer glazing: Use dipping or spraying method to apply glaze slurry in 2-3 times, and let it dry after each application;

[0091] ③ Drying: Place the glazed casserole in a ventilated place to dry naturally or in a low-temperature oven;

[0092] b. Firing process:

[0093] ④ Preheating stage: Heat to 150℃ at a heating rate of 5℃ / min and keep warm for 30 minutes; at around 150℃, dihydrogen phosphate reacts with aluminum hydroxide in the hydrotalcite structure to produce aluminum dihydrogen phosphate with bonding effect;

[0094] ⑤ Holding stage: Heating at a rate of 100℃ / h to 400℃ and holding for 2h; at around 400℃, aluminum dihydrogen phosphate melts and penetrates into all parts of the glaze and the pores of the casserole, forming a continuous phosphate film, which makes the glaze and the casserole tightly bonded and makes the glaze structure denser, making it less likely to stick to the pot;

[0095] Firing stage: The temperature is raised to 1100°C at a rate of 150°C / h and held at this temperature for 2 hours. After reaching 1100°C, the components are dehydrated, and in particular, the phosphate membrane connecting the components is sintered, producing an acidic porous glaze with a high phosphorus content (possibly phosphorus oxides of various valence states, accounting for 3.2-4.5% of the total weight of the glaze). These acidic pores have the function of adsorbing alkalis, salts, and various metal ions, especially sodium and potassium ions. They have high adsorption capacity and can be used in conjunction with the casserole pot opening process to produce high-melting-point components such as sodium hydrogen phosphate or potassium hydrogen phosphate, thereby improving the pot's structural strength.

[0096] ⑦ Cooling stage: Cool naturally to room temperature to ensure that the glaze is tightly bonded to the casserole body to obtain a glazed casserole product.

[0097] 3. Open the pot:

[0098] Example 8:

[0099] The glazed casserole prepared in Example 2 is opened, comprising the following steps:

[0100] c. Acid immersion: The glazed casserole product is completely immersed in a white vinegar solution having an acetic acid concentration of 15-20wt% by weight for 2-3h;

[0101] d. Cook with salt: After soaking, add a casserole with a weight concentration of 15-20wt% sodium chloride solution, open the lid and bring to a boil over high heat (large, medium and low heat on a household gas stove, for example), close the lid, and simmer for 2-3h;

[0102] e. Fire baking: Pour out the sodium chloride solution in the casserole and dry bake the casserole with a high flame (high-fire stove in a restaurant) or acetylene-air combustion flame. Salt particles will adhere to the inner wall of the casserole, gradually melt, and eventually be completely absorbed by the glaze.

[0103] f. Water Washing: When no salt particles or molten salt are visible, cool the casserole, add water, bring to a boil, discard the water, add water again, bring to a boil, discard the water, and then cool to dry. This will create a dry-burning, self-opening casserole. By utilizing the pores of sodium chloride and acidic phosphoric acid, high-melting-point sodium hydrogen phosphate or sodium phosphate is produced under high-temperature flame burning. This structure further densifies the glaze surface and allows it to penetrate into the sand mold structure, improving the structural stability of the casserole.

[0104] Examples 1-8 and Comparative Example 1 were subjected to a dry-firing test: 15% ethyl cellulose was prepared into an aqueous solution, dried at a medium heat of 200°C, and then dried at a high heat of 500°C. The cracking time of the glaze of the casserole was tested, as shown in Table 2:

[0105] Table 2. Dry burning resistance of casserole

[0106] Example Glaze cracking time / h Example 1 78.9 Example 2 83.3 Example 3 81.5 Comparative Example 1 45.0 Example 4 81.3 Example 5 84.1 Example 6 82.5 Example 7 86.2 Example 8 108.5

[0107] As shown in Table 2, the hydrotalcite treated with dihydrogen phosphate intercalation significantly improves the glaze durability, and the salt boiling process further promotes the durability.

[0108] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A durable casserole glaze slurry, characterized in that: It comprises the following components in parts by weight: 20-30 parts of dihydrogen phosphate intercalated hydrotalcite; 30-40 parts of kaolin; 15-25 parts of potassium feldspar; 5-10 parts of borax; 3-8 parts of magnesium oxide; The rest is water, which is used to adjust the viscosity of the glaze slurry; The preparation process of the dihydrogen phosphate intercalated hydrotalcite is as follows: 1) Preparation of hydrotalcite precursor: Weigh Mg(NO3)2·6H2O and Al(NO3)·9H2O, dissolve them in deionized water to prepare a mixed salt solution, and dissolve Na2CO3 and NaOH in deionized water to prepare a mixed alkaline solution with the same volume as the mixed salt solution; The mixed salt solution and the mixed alkali solution were added to the rotating liquid film reactor at the same speed for nucleation, and then the nucleation slurry was crystallized at reflux temperature for 6 hours; The solid precipitate obtained was centrifuged and then washed with deionized water until the pH value was 7 to obtain a wet cake, i.e., a hydrotalcite precursor; 2) Dihydrogen phosphate intercalation treatment: The wet filter cake obtained in 1) and deionized water were mixed in a weight ratio of 1:2 to form a slurry. Under nitrogen protection and stirring, a NaH2PO4·2H20 aqueous solution was slowly added to the slurry. The pH value of the system was adjusted to 4.5±0.5 with a dilute HNO3 solution, and refluxed for 1 hour. The product was thoroughly washed with deionized water without CO2 to a pH of 7, and then dried to obtain a dihydrogen phosphate intercalated hydrotalcite product.

2. The durable casserole glaze slurry according to claim 1, characterized in that: In the above 1), the molar ratio of Mg to Al in the mixed salt solution is 2:1, the molar ratio of Na2CO3 to Al(NO3)·9H2O in the mixed alkali solution is 1:1, and the molar ratio of NaOH to Al(NO3)·9H2O is 1.6:

1.

3. The durable casserole glaze slurry according to claim 1, characterized in that: The weight concentration of the NaH2PO4·2H20 aqueous solution in the above 2) is 12 wt%.

4. The method for preparing a durable casserole glaze slurry according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Raw material pretreatment: Dihydrogen phosphate intercalated hydrotalcite, kaolin, potassium feldspar and borax were sieved through 50 meshes to remove large particles of impurities; S2. Mixing and stirring: Add the above raw materials into the blender according to the proportion, add appropriate amount of water, and stir until uniform; S3, Filtering: Filter the stirred glaze slurry through a 150-mesh sieve to remove easily sedimentable impurities; S4. Adjust viscosity and color: Adjust the viscosity of the glaze slurry as needed to ensure it is suitable for glazing operations; Add pigments and adjust the color to obtain a durable casserole glaze slurry product.

5. The method for preparing a durable casserole glaze slurry according to claim 4, characterized in that: The colorant includes one or more of iron oxide, manganese oxide, copper oxide and chromium oxide.

6. A method for glazing and firing a clay pot, wherein the durable clay pot glaze slurry product is prepared by the preparation method according to claim 4, characterized in that: The following steps are involved: a. Glazing process: ① Clean the surface of the casserole: Make sure there is no oil or dust on the surface of the casserole; ②Multi-layer glazing: Use dipping or spraying method to apply glaze slurry in 2-3 times, and let it dry after each application; ③ Drying: Place the glazed casserole in a ventilated place to dry naturally or in a low-temperature oven; b. Firing process: ④ Preheating stage: Heat to 150℃ at a heating rate of 5℃ / min and keep warm for 30 minutes; at around 150℃, dihydrogen phosphate reacts with aluminum hydroxide in the hydrotalcite structure to produce aluminum dihydrogen phosphate with bonding effect; ⑤ Holding stage: heating to 400℃ at a heating rate of 100℃ / h and holding for 2h; ⑥ Firing stage: heating to 1100℃ at a heating rate of 150℃ / h and keeping warm for 2h; ⑦ Cooling stage: Cool naturally to room temperature to ensure that the glaze is tightly bonded to the casserole body to obtain a glazed casserole product.

7. The method for opening the glazed casserole product obtained by the glazing and firing method of casserole according to claim 6, characterized in that: The following steps are involved: c. Acid immersion: The glazed casserole product is completely immersed in a white vinegar solution having an acetic acid concentration of 15-20wt% by weight for 2-3h; d. Cook with salt: After soaking, add a 15-20wt% sodium chloride solution to the casserole, bring to a boil over high heat with the lid open, then simmer for 2-3h over low heat after closing the lid; e. Fire baking: Pour out the sodium chloride solution in the casserole and dry bake the casserole with high heat or acetylene air combustion flame. Salt particles will adhere to the inner wall of the casserole, gradually melt, and eventually be completely absorbed by the glaze; f. Water washing: When there are no obvious salt particles or molten salt, cool the casserole, add water, boil it, pour out the water, add water again, boil it, pour out the water, dry the water and cool it down to obtain a casserole product that is resistant to dry burning and prevents self-opening.

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