Non-fluoride and non-nitrate steel plate enamel for medium temperature and its preparation method and application

Abstract

The application discloses a steel plate enamel medium-temperature pearlescent glaze free of fluorinated salt and nitrate, a preparation method and application thereof, and belongs to the technical field of enamel. The pearlescent glaze is composed of quartz, zero-water borax, titanium dioxide, magnesium carbonate, sodium tripolyphosphate, potassium carbonate, lithium carbonate, potassium feldspar, zinc oxide and V-26 in a specific mass ratio. The preparation comprises the steps of raw material mixing, high-temperature smelting under pure oxygen condition, wire drawing detection and rapid cooling. The pearlescent glaze is completely free of fluorinated salt and nitrate, avoids fluorine emission and environmental protection equipment blockage problems from the source, the fluorine content of the product is not detected through detection, meets the requirements of the EU REACH regulation, has good porcelain surface, luster and medium-temperature firing adaptability, is suitable for a steel plate substrate, has a firing temperature of 800-830 DEG C, and can be used for the production of green and environmentally-friendly enamel products.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of enamel, and particularly relates to a steel plate enamel medium-temperature pearlescent glaze free of fluorinated salt and nitrate salt and a preparation method and application thereof. BACKGROUND

[0002] The steel plate enamel medium-temperature pearlescent glaze needs to meet four core indexes of high brightness of the enamel surface, keeping the original color of the pearlescent pigment (i.e. not dissolving the pearlescent pigment), good opalescence and medium-temperature firing (800-830 DEG C). The traditional formula relies on fluorinated salt (fluorite / fluorosilicate accounts for 1-12%) to achieve fluxing, improve opalescence and the like. The fluorinated salt in the traditional enamel face glaze is not an "optional" additive, but an "indispensable" skeleton component. Since the fluorinated salt has multiple synergies of reducing the melting temperature, improving the opalescence and wettability and the like, simply and roughly removing the fluorinated salt is equivalent to removing the load-bearing wall of the mansion, which leads to not "decrease" in performance, but "collapse" of the entire enamel system. Any fluorine-free attempt must be based on finding or inventing a new substance or new process system that can completely simulate or replace the above multiple functions, and this is still a major technical challenge in the field of enamel technology. Therefore, the importance of fluorinated salt in the traditional process cannot be overemphasized. However, research has confirmed that:

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

[0004] 2. The European Union REACH regulation lists fluorides as a high-concern substance (SVHC), and fluorinated salt products cannot meet the EU REACH regulation requirements for fluorine, with a fluorine (F) limit of 20 mg / kg.

[0005] 3. End environmental management equipment is blocked due to fluorinated salt crystallization, which seriously restricts normal production of enterprises.

[0006] At the same time, nitrate salt as a traditional oxidizing agent and close-together promoting component is prone to produce nitrogen oxides (NO x ) in the high-temperature decomposition process, which also faces environmental pressure. Currently, the denitration of enamel glaze has solved the problem of nitrogen oxide emission (such as CN114368912B, CN114315150B, CN114315151B and the like), and further implementation of fluorine-free, promotion of fluorine-free and nitrate-free system research and development is not only a necessary choice to respond to regulations, but also a forward-looking technical layout for the future.

[0007] The replacement of fluorinated salt is a major technical 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 (medium temperature pearlescent enamel glaze for steel plate) 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 medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates, as well as its preparation method and application.

[0013] The present invention provides a medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates. The formulation consists of the following components in parts by weight: 40-45 parts quartz, 18-25 parts anhydrous borax, 10-16 parts titanium dioxide, 1-2 parts magnesium carbonate, 2-6 parts sodium tripolyphosphate, 3-5 parts potassium carbonate, 2-3 parts lithium carbonate, 2-3 parts potassium feldspar, 1-2 parts zinc oxide, and 2-10 parts V-26, wherein V-26 is a flux comprising soda ash, rutile, potassium carbonate, and anhydrous borax.

[0014] Further, the composition includes 41-44 parts quartz, 22-25 parts anhydrous borax, 12-16 parts titanium dioxide, 1.5-2 parts magnesium carbonate, 2.5-6 parts sodium tripolyphosphate, 3.5-5 parts potassium carbonate, 2.5-3 parts lithium carbonate, 2.5-3 parts potassium feldspar, 1-1.6 parts zinc oxide, and 4-10 parts V-26.

[0015] Furthermore, V-26 is composed of the following components by weight percentage:

[0016] Soda ash 10%–30%, rutile (titanium dioxide) 5%–15%, potassium carbonate 10%–40%, anhydrous borax 20%–60%, the remainder being unavoidable impurities.

[0017] Furthermore, the preparation method of V-26 includes: mixing the flux components evenly, melting at 1280℃±10℃ for 2 to 2.2 hours, and then cooling to room temperature to obtain a glassy flux. This flux is mainly used to lower the melting temperature of other ceramic enamels and improve fluidity and gloss.

[0018] Furthermore, the mass percentage of SiO2 in quartz is ≥99%, the mass percentage of TiO2 in titanium dioxide is ≥99%, the mass percentage of SiO2 in potassium feldspar is ≥71%, K2O+Na2O is ≥11%, and zinc oxide is obtained by oxidation after distillation of metallic zinc, with a mass purity of ≥99.7%.

[0019] The preparation method of the above-mentioned medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates includes the following steps:

[0020] (1) Weigh each component raw material according to the above mass proportions;

[0021] (2) Stir and mix the raw materials described in step (1) until they are evenly mixed;

[0022] (3) Add the mixed material into the melting furnace and melt it under pure oxygen conditions. The melting temperature is controlled at 1300±10℃.

[0023] (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 melted without knots within 1 meter for 2-5 minutes to complete the melting process.

[0024] (5) The molten borosilicate glass body is rapidly cooled to obtain the product.

[0025] Furthermore, in step (5), the rapid cooling is achieved by water quenching or tableting.

[0026] The above-mentioned application of medium-temperature pearlescent enamel for steel plates, which is free of fluoride salts and nitrates, is applied to blanks with steel plates as the base material. The firing temperature of the finished product is 800-830℃, excluding the endpoint value of 800℃.

[0027] This invention introduces zinc oxide into the medium-temperature pearlescent enamel formulation of steel plate enamel, which works synergistically with titanium dioxide in titanium dioxide. The ZnO / TiO2 ratio reduces the liquid phase viscosity and accelerates ion and bubble diffusion. Increasing the amount of phosphate provides [PO4] on the one hand. 3- The functional groups promote feldspar nucleation, and on the other hand, they form a eutectic composite fluxing system of "multi-carbonate + phosphate + borate" which, together with the V-26 flux, enhances fluxing. The synergistic effect of each component promotes the improvement of various properties such as glaze gloss, pearlescent pigment color development, opacity, and firing performance.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) Achieve ultra-low emission standards for fluorides;

[0030] (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).

[0031] (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.

[0032] (4) Good adaptability to medium temperature firing: The low eutectic composite flux system (multi-carbonate + phosphate + borate) interacts with other components to keep the firing temperature stable at 800-830℃, and the porcelain surface has good leveling properties.

[0033] (5) Increase the amount of phosphate used. Phosphate provides [PO4] 3-The group promotes feldspar nucleation; the addition of zinc oxide and ZnO / TiO2 reduces liquid phase viscosity and accelerates ion diffusion; the addition of V-26 flux reduces liquid phase viscosity; and the synergistic effect with other components improves the surface gloss and color development of pearlescent pigments, increases the opacity of the glaze, and lowers the firing temperature of the glaze. Attached Figure Description

[0034] Figure 1 This is a photograph of the product obtained in Embodiment 1 of the present invention applied to a porcelain enamel plate made of steel plate enamel. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0036] The equipment used in this embodiment of the invention is:

[0037] 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.

[0038] Melting: An automatic feeding system, an automatic pure oxygen combustion control system, and an automatic discharging system are adopted.

[0039] Packaging: An automated packaging system is used.

[0040] The purity of the raw materials used in the embodiments of this invention meets the requirements of industrial grade.

[0041] Example 1

[0042] (1) Weigh the raw materials according to the following mass parts of each component:

[0043] Quartz 45 parts, anhydrous borax 20 parts, titanium dioxide 15 parts, magnesium carbonate 2 parts, sodium tripolyphosphate 3.8 parts, potassium carbonate 4.5 parts, lithium carbonate 2.2 parts, potassium feldspar 2.5 parts, zinc oxide 2 parts, V-26 3 parts;

[0044] V-26 is composed of the following components by weight percentage:

[0045] Soda ash 20%, rutile (titanium dioxide) 12%, potassium carbonate 25%, anhydrous borax 40%, the remainder being unavoidable impurities;

[0046] The mass percentage of SiO2 in quartz is ≥99%, the mass percentage of TiO2 in titanium dioxide is ≥99%, the mass percentage of SiO2 in potassium feldspar is ≥71%, and the mass percentage of K2O+Na2O is ≥11%. Zinc oxide is obtained by oxidation after distillation of metallic zinc, and its mass purity is ≥99.7%.

[0047] (2) Mix the above raw materials evenly.

[0048] (3) Add the mixed material into the melting furnace and melt it under pure oxygen conditions. The melting temperature is controlled at 1300±10℃.

[0049] (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: the glass wire is melted for 5 minutes without any knots within 1 meter to complete the melting.

[0050] (5) The molten borosilicate glass body is rapidly cooled (water quenched) to obtain the product.

[0051] A photograph of the product obtained in Example 1 applied to a porcelain enamel plate made of steel plate is shown below. Figure 1 As shown, the medium-temperature pearlescent enamel on the steel plate, which is free of fluoride salts and nitrates, has a smooth and delicate surface with no obvious defects in appearance. It has excellent gloss and color performance, and the product quality meets the enterprise's standard requirements.

[0052] Example 2

[0053] The preparation process in this embodiment is basically the same as that in Example 1, except that:

[0054] The mass fractions of each component in step (1) are: 40 parts quartz, 18 parts anhydrous borax, 10 parts titanium dioxide, 1 part magnesium carbonate, 2 parts sodium tripolyphosphate, 3 parts potassium carbonate, 2 parts lithium carbonate, 2 parts potassium feldspar, 2 parts zinc oxide, and 2 parts V-26.

[0055] In step (5), the molten borosilicate glass body is rapidly cooled by pressing.

[0056] Example 3

[0057] The preparation process in this embodiment is basically the same as that in Example 1, except that:

[0058] The mass fractions of each component in step (1) are: 44 parts quartz, 22 parts anhydrous borax, 12 parts titanium dioxide, 1.5 parts magnesium carbonate, 2.5 parts sodium tripolyphosphate, 3.5 parts potassium carbonate, 2.5 parts lithium carbonate, 2.5 parts potassium feldspar, 1.6 parts zinc oxide, and 10 parts V-26.

[0059] Example 4

[0060] The preparation process in this embodiment is basically the same as that in Example 1, except that:

[0061] The mass fractions of each component in step (1) are: 41 parts quartz, 25 parts anhydrous borax, 16 parts titanium dioxide, 2 parts magnesium carbonate, 6 parts sodium tripolyphosphate, 5 parts potassium carbonate, 3 parts lithium carbonate, 3 parts potassium feldspar, 1 part zinc oxide, and 4 parts V-26.

[0062] Comparative Example 1

[0063] The rest is the same as in Example 1, except that the mass parts of each component in step (1) are: 45 parts of quartz, 24 parts of anhydrous borax, 15 parts of titanium dioxide, 8 parts of sodium fluorosilicate, 2.5 parts of potassium feldspar, 2.2 parts of lithium carbonate, 2 parts of magnesium carbonate, and 1.6 parts of sodium tripolyphosphate.

[0064] The test results of the products obtained from the above embodiments and comparative examples are shown in Table 1 below.

[0065] Table 1. Test results of products obtained from each embodiment and comparative example.

[0066]

[0067] The above embodiments and test results demonstrate that the medium-temperature pearlescent enamel for steel plates produced by the method of the present invention, which is free of fluoride salts and nitrates, produces no fluorides during the preparation process. The various properties of the resulting product (gloss, pearlescent pigment color development, opacity, firing temperature) all meet the requirements for medium-temperature pearlescent enamel for steel plates. The fluoride test results show that no fluoride was detected, which meets the EU REACH regulation's limit requirements for SVHCs (substances of very high concern). This fundamentally solves the technical problems of existing medium-temperature pearlescent enamels for steel plates generating fluoride gas emissions that pollute the environment and the emitted fluoride salts that clog environmental protection facilities during the production process.

Claims

1. A medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates, characterized in that, Its formula consists of the following components by weight: quartz 40-45 parts, anhydrous borax 18-25 parts, titanium dioxide 10-16 parts, magnesium carbonate 1-2 parts, sodium tripolyphosphate 2-6 parts, potassium carbonate 3-5 parts, lithium carbonate 2-3 parts, potassium feldspar 2-3 parts, zinc oxide 1-2 parts, and V-26 2-10 parts. The V-26 is a flux including soda ash, rutile, potassium carbonate, and anhydrous borax. V-26 consists of the following components by weight percentage: soda ash 10%-30%, rutile 5%-15%, potassium carbonate 10%-40%, anhydrous borax 20%-60%, and the remainder being unavoidable impurities.

2. The medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in claim 1, characterized in that, Quartz 41-44 parts, anhydrous borax 22-25 parts, titanium dioxide 12-16 parts, magnesium carbonate 1.5-2 parts, sodium tripolyphosphate 2.5-6 parts, potassium carbonate 3.5-5 parts, lithium carbonate 2.5-3 parts, potassium feldspar 2.5-3 parts, zinc oxide 1-1.6 parts, V-26 4-10 parts.

3. The medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, The preparation method of V-26 includes mixing the components of the flux evenly, melting it at 1280℃±10℃ for 2 to 2.2 hours, and then cooling it to room temperature to obtain a glassy flux.

4. The medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, The mass percentage of SiO2 in quartz is ≥99%, and the mass percentage of TiO2 in titanium dioxide is ≥99%.

5. The medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, The mass percentage of SiO2 in potassium feldspar is ≥71%, and the mass percentage of K2O+Na2O is ≥11%.

6. The medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, Zinc oxide is obtained by oxidizing metallic zinc after distillation, and its purity is ≥99.7%.

7. The method for preparing a medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in any one of claims 1 to 6, 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 and melt it under pure oxygen conditions. The melting temperature is controlled at 1300±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 melted without knots within 1 meter for 2-5 minutes to complete the melting process. (5) The molten borosilicate glass body is rapidly cooled to obtain the product.

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

9. The application of the medium-temperature pearlescent enamel for steel plates that is free of fluoride salts and nitrates as described in any one of claims 1 to 6, characterized in that, It is applied to blanks with steel plates as the base material, and the firing temperature of the finished product is 800-830℃, excluding the endpoint value of 800℃.

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