Fluoride-free and nitrate-free cast iron enamel high temperature ground coat and its preparation method and application

Abstract

The application discloses a cast iron enamel high-temperature ground glaze free of fluorinated salt and nitrate, a preparation method and application thereof, and belongs to the technical field of enamel. The ground glaze is prepared from quartz, zero-water borax, soda ash, potassium carbonate, barium carbonate, potassium feldspar, magnesium carbonate, copper oxide, manganese oxide, aluminum oxide and recycled ternary battery positive electrode material according to specific mass proportions. The preparation comprises raw material mixing, smelting at 1290±10 DEG C under a pure oxygen environment, and rapid cooling after wire drawing detection of the smelting state. The ground glaze completely avoids the use of fluorinated salt and nitrate, eliminates the problems of fluoride emission and environmental protection equipment blockage from the source, the fluorine content of the product is not detected, and the limit value requirement of the EU REACH regulation is met. Meanwhile, by introducing the recycled ternary battery material, the adhesion of the ground glaze is obviously enhanced, the synergistic effect between components is strengthened, other performances are promoted, and resource recycling and cost reduction are realized.

Description

Technical Field

[0001] This invention belongs to the field of enamel technology, specifically relating to a high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates, its preparation method, and its application. Background Technology

[0002] As the transition layer between the metal substrate and the top glaze, the adhesion and firing performance of enamel base glaze directly affect product quality, while its environmental friendliness impacts the industry's survival and sustainable development. Traditional enamel base glaze formulations typically include fluoride salts (such as fluorite and sodium fluorosilicate) (1-10%) as fluxes and adhesion enhancers. Fluoride salts are not optional additives in traditional enamel base glazes, but rather indispensable structural components. Through multiple synergistic effects, such as lowering melting temperature, forming an alloy layer at the corrosion interface, creating a mechanical anchoring effect, and improving opacity and wettability, they lay the foundation for a strong bond between the glaze and the metal substrate from both physical and chemical dimensions. Simply and crudely removing fluoride salts is tantamount to removing the load-bearing walls of a building; the result is not a "decrease" in performance, but the "collapse" of the entire enamel system. Any attempt at fluorine-free enamel must be based on finding or inventing a new material or process system that can completely simulate or replace these multiple functions, which remains a major technical challenge in the field of enamel processing. Therefore, the importance of fluoride salts in traditional processes cannot be overstated. However, research confirms that:

[0003] 1. Hydrogen fluoride (HF) and silicon tetrafluoride (SiF4) gases released during high-temperature melting cause harm to health and the environment.

[0004] 2. The EU REACH regulation lists fluorides as Substances of Very High Concern (SVHC). Fluoride salt products cannot meet the EU REACH regulations' requirements for fluoride, with a fluoride (F) limit of 20 mg / kg.

[0005] 3. The end-of-pipe environmental treatment equipment is blocked by fluoride crystals, which seriously restricts the normal production of enterprises.

[0006] Meanwhile, nitrates, as traditional oxidants and adhesion promoters, readily produce nitrogen oxides (NOx) during high-temperature decomposition. x Similarly, they also face environmental pressures. Currently, the removal of nitrates from enamel glazes has solved the problem of nitrogen oxide emissions (such as CN114368912B, CN114315150B, CN114315151B, etc.). Further achieving fluorine-free production and promoting the research and development of fluorine-free and nitrate-free systems is not only an inevitable choice to comply with regulations, but also a forward-looking technological layout for the future.

[0007] The replacement of fluoride salts is a major technological bottleneck at present, mainly reflected in:

[0008] (1) Strong dependence on fluoride salts and prominent environmental risks: CN119710693A (high temperature resistant enamel glaze) uses cryolite (Na3AlF6) as a flux, which improves the temperature resistance but does not solve the problem of fluorine emission; CN112342544A (low temperature acid and alkali resistant cast iron enamel) contains sodium fluorosilicate (5-7 parts) in its surface glaze formula.

[0009] (2) Non-fluorine alternatives have functional defects: CN105800935A (enamel base glaze material) attempts to enhance adhesion with lanthanide oxides, but it still requires the addition of 8% fluoride to assist melting, and the high cost of rare earth makes it difficult to promote. CN116854374A (black enamel composite glaze) adopts a cobalt-nickel base glaze system, but the explosion retardant it uses contains 8-10% fluorite powder.

[0010] (3) In the ceramics field, there are fluorine-free solutions, but they are difficult to transfer and apply: CN110885189A relates to zirconium-free mutton fat glaze and positioning crystal flower ceramic tiles made using it; CN115626774A relates to soft-light skin-feel ceramic slabs and their preparation methods; CN112979271A relates to the preparation method of lightweight, high-strength, pure-color polished glazed tiles; CN118754723A relates to a hydrophilic self-cleaning antique tile based on phase separation and its preparation method. Although the above-mentioned prior art does not involve the use of fluoride salts, its technical essence belongs to the category of building ceramic glazes, which is a different technical field from enamel base glazes. Ceramic glazes and metal-based enamel glazes have essential differences in thermal expansion coefficients (the two expansion coefficients differ by an order of magnitude), firing temperatures (the firing temperature of ceramic glazes is more than 200℃ higher than that of enamel glazes), and bonding mechanisms (the base of ceramic glazes is porcelain clay, while the base of enamel glazes is metal), thus they cannot be directly transferred and applied to the field of metal-based enamel.

[0011] In summary, addressing the issue of fluoride removal on the basis of nitrate removal, while simultaneously improving the quality of enamel products, is of great practical significance for promoting the green, low-carbon, and high-quality development of the enamel industry. Summary of the Invention

[0012] In response to the technical problems of excessive fluoride emissions during the existing enamel glaze production process, which cause harm to health and the environment, the inability of fluoride-containing salt products to meet the fluoride requirements of the EU REACH regulation, and the clogging of environmental protection facilities by emitted fluoride salts, which seriously restricts the normal production of enterprises, this invention provides a high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates, as well as its preparation method and application.

[0013] The high-temperature base glaze for cast iron enamel, which is free of fluoride salts and nitrates, is formulated with the following components in parts by weight: 24-28 parts quartz, 23-26 parts anhydrous borax, 7.5-10.0 parts soda ash, 4-5 parts potassium carbonate, 4-6 parts barium carbonate, 7-8 parts calcium carbonate, 21-23 parts potassium feldspar, 1.2-1.6 parts magnesium carbonate, 0.5-0.6 parts copper oxide, 1.2-1.4 parts manganese oxide, 0.9-1.0 parts aluminum oxide, and 2.2-3.4 parts recycled ternary lithium battery cathode material, wherein the recycled ternary lithium battery cathode material is a powder material containing lithium, nickel, cobalt, and manganese obtained by recycling waste ternary lithium battery cathode material.

[0014] Further, the composition includes 25-28 parts quartz, 23-25 ​​parts anhydrous borax, 8-9 parts soda ash, 4-4.5 parts potassium carbonate, 5-6 parts barium carbonate, 7-7.5 parts calcium carbonate, 21-22.5 parts potassium feldspar, 1.2-1.4 parts magnesium carbonate, 0.5-0.6 parts copper oxide, 1.2-1.3 parts manganese oxide, 0.9-1.0 parts aluminum oxide, and 2.8-3.4 parts recycled ternary battery cathode material.

[0015] Furthermore, the mass percentage of SiO2 in quartz is ≥99%, the mass percentage of SiO2 in potassium feldspar is ≥71%, and the mass percentage of K2O+Na2O is ≥11%. In the recycled ternary battery cathode material, based on the percentage of metal mass to the total mass of the material, Co ≥12.5wt%, Ni ≥30.2wt%, Mn ≥12.2wt%, Li ≥5.9wt%, and other raw materials are of industrial grade purity.

[0016] Furthermore, the recycled ternary battery cathode material is a commercially available material that meets the aforementioned percentage content of lithium, nickel, cobalt, and manganese. Other impurities will not affect the performance and use of the base glaze.

[0017] The preparation method of the above-mentioned high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates includes the following steps:

[0018] (1) Weigh each component raw material according to the above mass proportions;

[0019] (2) Stir and mix the raw materials described in step (1) until they are evenly mixed;

[0020] (3) Add the mixed material into the melting furnace for melting. The melting furnace is in a pure oxygen environment and the temperature is controlled at 1290±10℃.

[0021] (4) After the material described in step (3) is completely melted, a borosilicate glass body is obtained. The molten borosilicate glass body is then drilled and quickly drawn into a glass wire of 1.2 to 1.5 meters for testing. The testing requirement is that the glass wire is completely melted within 1 meter.

[0022] (5) The molten borosilicate glass body is rapidly cooled to obtain the product.

[0023] Furthermore, in step (5), the rapid cooling is achieved by water quenching or tableting.

[0024] The above-mentioned high-temperature base glaze for cast iron enamel, which is free of fluoride salts and nitrates, is applied to blanks with cast iron as the base material. The firing temperature of the finished product is 790-820℃, excluding the endpoint value of 790℃.

[0025] This invention introduces recycled ternary battery cathode material into the high-temperature base glaze formula of cast iron enamel, which not only significantly enhances the adhesion of the base glaze, but also strengthens the synergistic effect between components, promoting the improvement of the base glaze's surface, gloss, and other properties.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) Achieve ultra-low emission standards for fluorides;

[0028] (2) The product was tested by SGS and the fluoride test results showed that it was not detected, which meets the EU REACH regulation's limit requirements for SVHC (substances of very high concern).

[0029] (3) The problem of clogging in end-of-line environmental protection equipment is solved: This invention completely removes fluorides (fluorite, sodium fluorosilicate, etc.), eliminating the source of fluoride salt crystallization from the source, thus solving the problem of clogging in end-of-line environmental protection equipment. According to actual production line tests, the continuous operation cycle of the equipment has been extended from the original 10-15 days to more than 180 days, and the maintenance cost has been significantly reduced.

[0030] (4) Maintain the core performance of the base glaze without degradation: By recycling the positive electrode material of ternary battery to replace the adhesion enhancement effect of fluoride, the adhesion level is tested to be 2-3 (the traditional high temperature fluorine-containing base glaze is 2-3).

[0031] (5) Good firing adaptability: The low eutectic composite flux system (multi-carbonate + borate) interacts with other components to keep the firing temperature stable at 790-820℃. The leveling properties and bubble elimination rate of the ceramic layer are comparable to those of fluorine-containing base glaze.

[0032] (6) Resource recycling and cost optimization: Using recycled ternary battery cathode materials reduces the cost of cobalt, nickel and lithium raw materials by more than 25% and avoids pollution from heavy metal waste. Attached Figure Description

[0033] Figure 1 This is a photograph of the product obtained in Embodiment 1 of the present invention applied to a ceramic enamel plate made of cast iron. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0035] The equipment used in this embodiment of the invention is:

[0036] Ingredient preparation: A fully automated batching and mixing system is used. This system is fully automated and computer-controlled, featuring accurate weighing, uniform mixing, and high batching efficiency.

[0037] Melting: An automatic feeding system, an automatic pure oxygen combustion control system, and an automatic discharging system are adopted.

[0038] Packaging: An automated packaging system is used.

[0039] Apart from the recycled ternary battery cathode material, the purity of the raw materials used in the embodiments of this invention meets the requirements of industrial grade.

[0040] Example 1

[0041] (1) Weigh the raw materials according to the following mass parts of each component:

[0042] Quartz 24 parts, anhydrous borax 26 parts, soda ash 7.5 parts, potassium carbonate 4 parts, calcium carbonate 8 parts, barium carbonate 4 parts, potassium feldspar 21 parts, magnesium carbonate 1.6 parts, copper oxide 0.5 parts, manganese oxide 1.4 parts, aluminum oxide 1 part, and recycled ternary battery cathode material 2.2 parts.

[0043] The mass percentage of SiO2 in quartz is ≥99%, the mass percentage of SiO2 in potassium feldspar is ≥71%, and the mass percentage of K2O+Na2O is ≥11%. In the recycled ternary battery cathode material, based on the percentage of metal mass to the total mass of the material, Co ≥12.5wt%, Ni ≥30.2wt%, Mn ≥12.2wt%, and Li ≥5.9wt%, and other raw materials are of industrial grade purity.

[0044] (2) Mix the above raw materials evenly.

[0045] (3) Add the mixed material into the melting furnace for melting. The melting furnace is in a pure oxygen environment and the temperature is controlled at 1290±10℃.

[0046] (4) After the above materials are completely melted, a borosilicate glass body is obtained. The molten borosilicate glass body is drilled and quickly drawn into a glass wire of 1.2 to 1.5 meters for testing. The testing requirement is that the glass wire is completely melted within 1 meter.

[0047] (5) The molten borosilicate glass body is quenched with water to obtain the product.

[0048] A photograph of the product obtained in Example 1 applied to a ceramic enamel plate made of cast iron is shown below. Figure 1As shown, the high-temperature base glaze of cast iron enamel, which is free of fluoride salts and nitrates, has a smooth and delicate surface, excellent high-temperature firing performance and adhesion performance, and is widely used in cast iron enameled products.

[0049] Example 2

[0050] The preparation process of this embodiment is basically the same as that of Example 1, except that the mass parts of each component in step (1) are: 26 parts of quartz, 23 parts of anhydrous borax, 10 parts of soda ash, 5 parts of potassium carbonate, 7 parts of calcium carbonate, 4.8 parts of barium carbonate, 22 parts of potassium feldspar, 1.2 parts of magnesium carbonate, 0.5 parts of copper oxide, 1.2 parts of manganese oxide, 0.9 parts of aluminum oxide, and 2.4 parts of recycled ternary battery cathode material.

[0051] Example 3

[0052] The preparation process of this embodiment is basically the same as that of Example 1, except that the mass parts of each component in step (1) are: 25 parts of quartz, 23.3 parts of anhydrous borax, 8 parts of soda ash, 4.5 parts of potassium carbonate, 7.5 parts of calcium carbonate, 5 parts of barium carbonate, 22.5 parts of potassium feldspar, 1.4 parts of magnesium carbonate, 0.6 parts of copper oxide, 1.3 parts of manganese oxide, 0.9 parts of aluminum oxide, and 2.8 parts of recycled ternary battery cathode material.

[0053] Example 4

[0054] The preparation process of this embodiment is basically the same as that of Example 1, except that the mass parts of each component in step (1) are: 28 parts of quartz, 25 parts of anhydrous borax, 9 parts of soda ash, 4 parts of potassium carbonate, 7 parts of calcium carbonate, 6 parts of barium carbonate, 23 parts of potassium feldspar, 1.2 parts of magnesium carbonate, 0.5 parts of copper oxide, 1.2 parts of manganese oxide, 0.9 parts of aluminum oxide, and 3.4 parts of recycled ternary battery cathode material.

[0055] Comparative Example 1

[0056] The rest is the same as in Example 1, except that the mass parts of each component in step (1) are: quartz 24.0 parts, anhydrous borax 20 parts, soda ash 7.5 parts, barium carbonate 8.8 parts, fluorite 7.7 parts, magnesium carbonate 1.4 parts, potassium feldspar 22.0 parts, aluminum oxide 0.9 parts, manganese oxide 1.3 parts, cobalt oxide 0.5 parts, nickel oxide 1.3 parts, and copper oxide 0.6 parts.

[0057] The test results of the products obtained from the above embodiments and comparative examples are shown in Table 1 below.

[0058] Table 1. Test results of products obtained from each embodiment and comparative example.

[0059]

[0060] The above embodiments and test results demonstrate that the high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates produced by the method of the present invention produces no fluorides during the preparation process. The various properties of the resulting product (ceramic surface, gloss, adhesion, firing temperature) meet the requirements of high-temperature base glaze for cast iron enamel. The fluoride test results show that no fluoride was detected, which meets the limit requirements of the EU REACH regulation for SVHC (substances of very high concern). This fundamentally solves the technical problems of existing high-temperature base glazes for cast iron enamel generating fluoride gas emissions that pollute the environment and the fluoride salts emitted that clog environmental protection facilities during the production process.

Claims

1. A high-temperature base enamel for cast iron that is free of fluoride salts and nitrates, characterized in that, The formula consists of the following components by weight: 24-28 parts quartz, 23-26 parts anhydrous borax, 7.5-10.0 parts soda ash, 4-5 parts potassium carbonate, 4-6 parts barium carbonate, 7-8 parts calcium carbonate, 21-23 parts potassium feldspar, 1.2-1.6 parts magnesium carbonate, 0.5-0.6 parts copper oxide, 1.2-1.4 parts manganese oxide, 0.9-1.0 parts aluminum oxide, and 2.2-3.4 parts recycled ternary battery cathode material, which is a powder material containing lithium, nickel, cobalt, and manganese obtained by recycling waste ternary lithium battery cathode material.

2. The high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in claim 1, characterized in that, Quartz 25-28 parts, anhydrous borax 23-25 ​​parts, soda ash 8-9 parts, potassium carbonate 4-4.5 parts, barium carbonate 5-6 parts, calcium carbonate 7-7.5 parts, potassium feldspar 21-22.5 parts, magnesium carbonate 1.2-1.4 parts, copper oxide 0.5-0.6 parts, manganese oxide 1.2-1.3 parts, aluminum oxide 0.9-1.0 parts, and recycled ternary battery cathode material 2.8-3.4 parts.

3. The high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in claim 1, characterized in that, In the recycling of ternary battery cathode materials, the percentage of metal mass in the total mass of the material is as follows: Co≥12.5wt%, Ni≥30.2wt%, Mn≥12.2wt%, and Li≥5.9wt%.

4. The high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in claim 1, characterized in that, The mass percentage of SiO2 in quartz is ≥99%.

5. The high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in claim 1, characterized in that, The mass percentage of SiO2 in potassium feldspar is ≥71%, and the mass percentage of K2O+Na2O is ≥11%.

6. The method for preparing a high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Weigh the raw materials of each component; (2) Stir and mix the raw materials described in step (1) until they are evenly mixed; (3) Add the mixed material into the melting furnace for melting. The melting furnace is in a pure oxygen environment and the temperature is controlled at 1290±10℃. (4) After the material described in step (3) is completely melted, a borosilicate glass body is obtained. The molten borosilicate glass body is then drilled and quickly drawn into a glass wire of 1.2 to 1.5 meters for testing. The testing requirement is that the glass wire is completely melted within 1 meter. (5) The molten borosilicate glass body is rapidly cooled to obtain the product.

7. The preparation method according to claim 6, characterized in that, In step (5), the rapid cooling is achieved by water quenching or tableting.

8. The application of the high-temperature base glaze for cast iron enamel that is free of fluoride salts and nitrates as described in any one of claims 1 to 5, characterized in that, It is applied to blanks with cast iron as the base material, and the firing temperature of the finished product is 790-820℃, excluding the endpoint value of 790℃.

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