Fluoride-free and nitrate-free cast iron enamel zircon white glaze, its preparation method and application

Abstract

The application discloses a cast iron enamel zirconium white glaze free of fluorinated salt and nitrate, and a preparation method and application thereof, and belongs to the technical field of enamel. The zirconium white glaze is composed of quartz, borax pentahydrate, magnesium carbonate, potassium carbonate, potassium feldspar, zinc oxide, aluminum hydroxide, calcium carbonate, zirconium silicate, sodium tripolyphosphate and lithium carbonate 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 zirconium white 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 requirement of the EU REACH regulation, has good porcelain surface, gloss and firing adaptability, is suitable for a cast iron base, has a firing temperature of 740-760 DEG C, and can be used for the production of green and environmentally-friendly enamel products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of enamel and specifically relates to a cast iron enamel zirconium white glaze free of fluorinated salt and nitrate salt as well as a preparation method and application thereof. BACKGROUND

[0002] The cast iron enamel zirconium white glaze needs to meet core indexes such as whiteness (≥80), high opacity (milk performance) and low-temperature firing (740-760℃). The traditional formula relies on fluorinated salt (fluorite / fluorosilicate accounts for 1-12%) to realize fluxing, improve the milk performance and the like. The fluorinated salt is not an "optional" additive in the traditional enamel face glaze, but an "indispensable" skeleton component. Since the fluorinated salt has multiple synergies such as reducing the melting temperature, improving the opacity and wettability, simply and roughly removing the fluorinated salt is equivalent to removing the load-bearing wall of the mansion, which does not cause the "decrease" of performance, but the "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 enamel process field. 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 20mg / 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-promoting component, is prone to produce nitrogen oxides (NO x ) during high-temperature decomposition, also facing environmental pressure. Currently, the denitration of enamel glaze has solved the problem of nitrogen oxide emission (such as CN114368912B, CN114315150B, CN114315151B, etc.), and further realizing fluorine-free, promoting the research and development of fluorine-free and nitrate-free system 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) Fluorinated salt dependence is strong, and environmental risk is prominent: CN119710693A (high-temperature-resistant enamel glaze) uses cryolite (Na3AlF6) as a fluxing agent, although it improves temperature resistance, but does not solve the problem of fluorine emission; CN112342544A (low-temperature acid and alkali resistant cast iron enamel) contains sodium fluoride (5-7 parts) in the face glaze formula.

[0009] (2) Non-fluorine substitution scheme has functional defects: CN105800935A (enamel underglaze material) attempts to use lanthanide oxides to enhance adhesion, but it still needs to add 8% fluorine to assist melting, and the high cost of rare earth makes it difficult to promote. CN116854374A (black enamel composite glaze) uses a cobalt-nickel underglaze system, but the anti-explosive agent used contains 8-10% fluorite powder.

[0010] (3) The field of ceramics involves fluorine-free schemes, but it is difficult to apply: CN110885189A relates to a zirconium-free lanolin enamel and a positioning crystal flower ceramic tile made using the same, CN115626774A relates to a soft light skin ceramic rock plate and a method for preparing the same, CN112979271A relates to a method for preparing a light-weight high-strength pure-color glaze tile, and CN118754723A relates to a hydrophilic self-cleaning antique tile based on phase separation and a method for preparing the same. Although the above-mentioned prior art does not involve the use of fluorinated salt, its technical essence belongs to the field of building ceramic glaze, which is different from the field of enamel underglaze. There are essential differences between ceramic glaze and metal-based enamel glaze in terms of thermal expansion coefficient (the difference in expansion coefficient between the two is one order of magnitude), firing temperature (the firing temperature of ceramic glaze is higher than that of enamel glaze by more than 200°C), and bonding mechanism (the body of ceramic glaze is porcelain clay, while the body of enamel glaze is metal), thus it cannot be directly applied to the field of metal-based enamel.

[0011] In summary, on the basis of denitrification, the problem of defluorination is solved, and the quality of enamel products is improved, which has very important practical significance for promoting the green, low-carbon and high-quality development of the enamel industry. SUMMARY

[0012] In view of the excessive emission of fluorides in the production process of existing enamel glaze, which causes damage to health and the environment, the fluorinated salt-containing products cannot meet the requirements of the EU REACH regulation on fluorine, and the emitted fluorinated salt blocks environmental management facilities, which seriously restricts the normal production of enterprises, the present application provides a cast iron enamel zirconium white glaze without fluorinated salt and nitrate, as well as a preparation method and application thereof.

[0013] The cast iron enamel zirconium white glaze without fluorinated salt and nitrate of the present application is prepared from the following components by mass fraction: quartz 18-24 parts, borax pentahydrate 14-18 parts, magnesium carbonate 1-4 parts, potassium carbonate 4-8 parts, potassium feldspar 2-5 parts, zinc oxide 4-7 parts, aluminum hydroxide 14-18 parts, calcium carbonate 10-14 parts, zirconium silicate 15-18 parts, sodium tripolyphosphate 3-5 parts, and lithium carbonate 0.1-0.5 parts.

[0014] Further, the mass fraction of SiO2 in quartz is ≥99%, the mass fraction of SiO2 in potassium feldspar is ≥71%, K2O+Na2O is ≥11%, and the zinc oxide is prepared by distillation of metallic zinc followed by oxidation, with a mass purity ≥99.7%.

[0015] Further, the mass fraction of SiO2 in quartz is ≥99%, the mass fraction of SiO2 in potassium feldspar is ≥71%, K2O+Na2O is ≥11%, and the zinc oxide is prepared by distillation of metallic zinc followed by oxidation, with a mass purity ≥99.7%.

[0016] The preparation method of the cast iron enamel zirconium white glaze without fluorinated salt and nitrate comprises the following steps:

[0017] (1) The raw materials are weighed according to the above mass fraction;

[0018] (2) The raw materials in step (1) are stirred and mixed uniformly;

[0019] (3) The uniformly mixed material is added to a melting furnace, and melting is carried out under pure oxygen conditions, with the melting temperature controlled at 1300±10℃;

[0020] (4) After the material in step (3) is completely melted, a borosilicate glass body is obtained, the molten borosilicate glass body is tapped, and is quickly drawn into a 1.2-1.5 meter glass filament for testing, with the testing requirement being that no node continues to melt for 2-5 minutes within 1 meter of the glass filament, and the melting is complete;

[0021] (5) The molten borosilicate glass body is rapidly cooled to obtain the product.

[0022] Further, in step (5), the rapid cooling is carried out by water quenching or tabletting process.

[0023] The cast iron enamel zirconium white glaze without fluorinated salt and nitrate is applied to a blank with a cast iron base, and the firing temperature of the finished product is 740-760℃.

[0024] The specific proportion of zinc oxide, calcium carbonate and zirconium silicate in the cast iron enamel zirconium white glaze formula of the present application synergistically acts to improve whiteness and opalescence, and increase the amount of phosphate, which on the one hand promotes feldspar nucleation by providing [PO4] 3- groups, and on the other hand forms a eutectic complex fluxing system of “multinary carbonate + phosphate + borate” to strengthen fluxing, so that the components jointly act to improve the comprehensive performance of the enamel surface gloss, whiteness, opacity (opalescence performance) and firing performance.

[0025] The present application has the following beneficial effects:

[0026] (1) Fluoride is discharged at an ultra-low standard;

[0027] (2) The product is detected by SGS, and the fluoride detection result shows that it is not detected, which meets the limit value requirement of the SVHC (substance of very high concern) of the EU REACH regulation.

[0028] (3) The problem of clogging of the end environmental protection equipment is solved: by completely removing fluorides (fluorite, sodium fluorosilicate, etc.), the present application eliminates the fluorine salt crystallization source from the source, and solves the problem of clogging of the end environmental protection equipment. According to the actual measurement of the production line, the continuous operation cycle of the equipment is prolonged from the original 10-15 days to more than 180 days, and the maintenance cost is significantly reduced.

[0029] (4) Good low-temperature firing adaptability: the eutectic complex fluxing system (multinary carbonate + phosphate + borate) interacts with other components to stably control the firing temperature at 740-760℃, and the enamel surface has good leveling property.

[0030] (5) The specific proportion of zinc oxide, calcium carbonate and zirconium silicate synergistically acts to improve whiteness and opalescence, and the components jointly act to improve the comprehensive performance of the enamel surface gloss, whiteness, opacity (opalescence performance) and firing performance. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The photo of the enamel panel made of cast iron using the product obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below in conjunction with specific examples, but the present application is not limited thereto.

[0033] The equipment used in the examples of the present application is as follows:

[0034] Batching: a full-automatic batching and mixing system is used. The system is fully automated and computer controlled, and has the characteristics of accurate weighing, uniform mixing and high batching efficiency.

[0035] Melting: an automatic feeding system, an automatic pure oxygen combustion control system and an automatic discharging system are used.

[0036] Packaging: Automatic packaging system is adopted.

[0037] The purity of the raw materials used in the embodiments of the present application meets the requirements of industrial grade.

[0038] Example 1

[0039] (1) The raw materials are weighed according to the mass parts of each component as follows:

[0040] Quartz 24 parts, borax pentahydrate 14 parts, magnesium carbonate 1 part, potassium carbonate 4 parts, potassium feldspar 2 parts, zinc oxide 7 parts, aluminum hydroxide 14 parts, sodium tripolyphosphate 3 parts, lithium carbonate 0.5 parts, calcium carbonate 10 parts, zirconium silicate 18 parts.

[0041] The mass percentage of SiO2 in quartz is ≥99%, the mass percentage of SiO2 in potassium feldspar is ≥71%, K2O+Na2O is ≥11%, and the mass purity of zinc oxide prepared by distillation of metallic zinc and oxidation is ≥99.7%.

[0042] (2) The above raw materials are stirred and mixed uniformly.

[0043] (3) The uniformly mixed material is added to a melting furnace, and melting is carried out under pure oxygen conditions, with the melting temperature controlled at 1300±10℃.

[0044] (4) After the above material is completely melted, a borosilicate glass body is obtained, the molten borosilicate glass body is drilled, and is quickly drawn into a glass filament of 1.2-1.5 meters for detection, with the detection requirement being that no knot continues to melt for 5 minutes within 1 meter of the glass filament.

[0045] (5) The melted borosilicate glass body is rapidly cooled (water quenching), and the product is obtained.

[0046] The product obtained in Example 1 of the present application is applied to a porcelain enamel plate made of cast iron, as shown in Figure 1 The cast iron enamel zircon white enamel surface of the product obtained in Example 1 of the present application is flat, has high gloss, excellent color development performance, has a high expansion coefficient, and is suitable for enameling of cast iron blanks.

[0047] Example 2

[0048] The preparation process of this embodiment is basically the same as that of Example 1, except that:

[0049] The mass parts of each component in step (1) are: quartz 18 parts, borax pentahydrate 18 parts, magnesium carbonate 4 parts, potassium carbonate 8 parts, potassium feldspar 5 parts, zinc oxide 4 parts, aluminum hydroxide 18 parts, sodium tripolyphosphate 5 parts, lithium carbonate 0.1 parts, calcium carbonate 14 parts, and zirconium silicate 15 parts.

[0050] In step (5), the borosilicate glass body melted is rapidly cooled by a tabletting process.

[0051] Example 3

[0052] The preparation process of this example is basically the same as that of Example 1, except that:

[0053] In step (1), the mass parts of each component are: quartz 23 parts, borax pentahydrate 15 parts, magnesium carbonate 2 parts, potassium carbonate 4.6 parts, potassium feldspar 4.5 parts, zinc oxide 4.5 parts, aluminum hydroxide 14.8 parts, sodium tripolyphosphate 3.5 parts, lithium carbonate 0.2 parts, calcium carbonate 10.5 parts, and zirconium silicate 16 parts.

[0054] Example 4

[0055] The preparation process of this example is basically the same as that of Example 1, except that:

[0056] In step (1), the mass parts of each component are: quartz 19 parts, borax pentahydrate 17 parts, magnesium carbonate 3 parts, potassium carbonate 6.6 parts, potassium feldspar 3.0 parts, zinc oxide 6 parts, aluminum hydroxide 16.8 parts, sodium tripolyphosphate 4.5 parts, lithium carbonate 0.4 parts, calcium carbonate 12.5 parts, and zirconium silicate 17.5 parts.

[0057] Comparative Example 1

[0058] The rest is the same as Example 1, except that in step (1), the mass parts of each component are: quartz 23.2 parts, borax pentahydrate 17.8 parts, magnesium carbonate 2 parts, potassium feldspar 2.5 parts, aluminum hydroxide 12.8 parts, cryolite 7 parts, sodium tripolyphosphate 1.6 parts, calcium carbonate 10.5 parts, and zirconium silicate 17.3 parts.

[0059] The test results of the products obtained in the above examples and comparative examples are shown in Table 1 below.

[0060] Table 1 Test results of products obtained in each example and comparative example

[0061]

[0062] The above examples and test results prove that the cast iron enamel zirconium white glaze produced by the method of the present application does not contain fluorinated salt and nitrate, no fluorinated compound is generated in the preparation process, and the performance (gloss, whiteness, opacity, firing temperature) of the obtained product meets the requirements of cast iron enamel zirconium white glaze, the fluorinated compound test result of the product shows no detection, which meets the limit requirements of SVHC (substance of very high concern) of the EU REACH regulation, and fundamentally solves the technical problems of environmental pollution caused by fluorinated compound gas emission and fluorinated salt emission during the production process of existing cast iron enamel zirconium white glaze.

Claims

1. A cast iron enamel zirconium white glaze that is free of fluoride salts and nitrates, characterized in that, Its formula consists of the following components by weight: quartz 18-24 parts, borax pentahydrate 14-18 parts, magnesium carbonate 1-4 parts, potassium carbonate 4-8 parts, potassium feldspar 2-5 parts, zinc oxide 4-7 parts, aluminum hydroxide 14-18 parts, calcium carbonate 10-14 parts, zirconium silicate 15-18 parts, sodium tripolyphosphate 3-5 parts, and lithium carbonate 0.1-0.5 parts.

2. The cast iron enamel zirconium white glaze that is free of fluoride salts and nitrates as described in claim 1, characterized in that, Quartz 19-23 parts, borax pentahydrate 15-17 parts, magnesium carbonate 2-3 parts, potassium carbonate 4.6-6.6 parts, potassium feldspar 3-4.5 parts, zinc oxide 4.5-6 parts, aluminum hydroxide 14.8-16.8 parts, calcium carbonate 10-14 parts, zirconium silicate 16-17.5 parts, sodium tripolyphosphate 3.5-4.5 parts, lithium carbonate 0.2-0.4 parts.

3. The cast iron enamel zirconium white glaze 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%.

4. The cast iron enamel zirconium white glaze 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%.

5. The cast iron enamel zirconium white glaze 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%.

6. The method for preparing cast iron enamel zirconium white glaze 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 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.

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 cast iron enamel zirconium white glaze 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 740-760℃.

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