Fluoride-free and nitrate-free cast iron enamel high temperature matte glaze, its preparation method and application

Abstract

The application discloses a cast iron enamel high-temperature matte glaze without fluorinated salt and nitrate, and a preparation method and application thereof, and belongs to the technical field of enamel. The matte glaze is prepared from quartz, borax pentahydrate, titanium dioxide, sodium carbonate, calcium carbonate, barium carbonate, aluminum oxide, sodium tripolyphosphate, potassium carbonate and lithium carbonate according to specific mass proportions. The preparation comprises raw material mixing, smelting at 1300+ / -10 DEG C under a pure oxygen environment, and rapid cooling after wire drawing detection of the smelting state. The matte glaze completely avoids the use of fluorinated salt and nitrate, eliminates the problems of fluoride emission and environmental protection equipment blockage from the source, and the fluorine content of the product is not detected through detection, thereby meeting the limit value requirements of the EU REACH regulation. Meanwhile, the matte glaze has good enamel surface, excellent firing performance and matte performance, is suitable for a cast iron substrate, has a firing temperature of 780-800 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 cast iron enamel high-temperature matte glaze free of fluorinated salt and nitrate salt and a preparation method and application thereof. BACKGROUND

[0002] The cast iron enamel high-temperature matte glaze requires high-temperature (780-800℃) firing, and has no defects in appearance, a smooth porcelain surface and a gloss (≤10). The traditional formula relies on fluorinated salt (fluorite / fluorosilicate accounts for 1-12%) to achieve fluxing, increase gloss and improve transparency, and the fluorinated salt is not an "optional" additive in the traditional high-temperature matte glaze, but an "indispensable" skeleton component. Since fluorinated salt has multiple synergistic effects of reducing the melting temperature, increasing the gloss and increasing the stability of the crystal, simply and roughly removing fluorinated salt does not result in "performance decline", but "collapse" of the entire enamel system. Any attempt to remove fluorinated salt 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 shown 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 adhesion promoting component, is prone to produce nitrogen oxides (NO x ) during high-temperature decomposition, and also faces environmental pressure. Currently, the removal of nitrate from enamel glaze has solved the problem of nitrogen oxide emission (such as CN114368912B, CN114315150B, CN114315151B, etc.), and further implementation 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) 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 migrate applications: 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, a cast iron enamel high-temperature matte glaze without fluorinated salt and nitrate salt and a preparation method and application thereof are provided.

[0013] The high-temperature matte enamel of the cast iron enamel without fluorinated salt and nitrate salt of the application is prepared from the following components in the following mass parts: quartz 33-36 parts, borax pentahydrate 12-14 parts, titanium white 3-5 parts, sodium carbonate 17-19 parts, calcium carbonate 5-7 parts, barium carbonate 2-4 parts, aluminum oxide 16-18 parts, sodium tripolyphosphate 2-4 parts, potassium carbonate 3-5 parts, and lithium carbonate 2-4 parts.

[0014] Further, the high-temperature matte enamel of the cast iron enamel without fluorinated salt and nitrate salt of the application is prepared from the following components in the following mass parts: quartz 35-36 parts, borax pentahydrate 13-14 parts, titanium white 4-5 parts, sodium carbonate 18-19 parts, calcium carbonate 6-7 parts, barium carbonate 3-4 parts, aluminum oxide 17-18 parts, sodium tripolyphosphate 3-4 parts, potassium carbonate 4-5 parts, and lithium carbonate 3-4 parts.

[0015] Further, in the quartz, the mass ratio of SiO2 and Fe2O3 is: SiO2≥99%, Fe2O3≤0.05%; in the titanium white, the mass ratio of TiO2 is: TiO2≥99%.

[0016] The preparation method of the above-mentioned high-temperature matte enamel of the cast iron enamel without fluorinated salt and nitrate salt comprises the following steps:

[0017] (1) the raw materials are weighed according to the above-mentioned mass parts;

[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, and the melting temperature is 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 glass filament of 1.2-1.5 meters for detection, and the detection requirement is: no knot is found within 1 meter of the glass filament, and the melting is continued for 10-15 minutes to complete the melting;

[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 using the water quenching or tabletting process.

[0023] The application of the above-mentioned high-temperature matte enamel of the cast iron enamel without fluorinated salt and nitrate salt is applied to a blank with a cast iron base, and the firing temperature of the finished product is 780-800℃, and does not include the end point value 780℃.

[0024] In addition, by adjusting the components and amount of the fluxing agent of the non-fluorinated salt in the formula of the present application, the melting of the enamel can be completed as required even without the fluxing of the fluorinated salt; the present application adds phosphate in the formula of the high-temperature matte enamel of cast iron enamel to form a eutectic complex fluxing system of'multi-carbonate + phosphate + borate' to strengthen the fluxing, and the components synergistically improve the gloss and firing performance of the enamel.

[0025] The present application has the following advantages:

[0026] (1) The fluorinated substance is discharged at an ultra-low standard.

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

[0028] (3) The problem of blockage of the end environmental protection equipment is solved: the present application completely removes the fluorinated substance (fluorite, sodium fluorosilicate, etc.), eliminates the fluorinated salt crystallization source from the source, and solves the problem of blockage of the end environmental protection equipment. According to the actual measurement of the production line, the continuous operation period 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 firing adaptability: the eutectic complex fluxing system (multi-carbonate + phosphate + borate) interacts with other components to stably control the firing temperature at 780-800℃, and the enamel surface has good leveling property.

[0030] (5) The phosphate is added to form a eutectic complex fluxing system of'multi-carbonate + phosphate + borate' to strengthen the fluxing, and the components synergistically improve the gloss and firing performance of the enamel. BRIEF DESCRIPTION OF DRAWINGS

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

[0032] The present application will be further described in detail below in combination 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 automatic 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: an automatic packaging system is used.

[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 following mass parts of each component:

[0040] Quartz 33 parts, borax pentahydrate 14 parts, titanium white 5 parts, sodium carbonate 17 parts, calcium carbonate 7 parts, barium carbonate 2 parts, aluminum oxide 18 parts, sodium tripolyphosphate 2 parts, potassium carbonate 3 parts, and lithium carbonate 2 parts.

[0041] In the quartz, the mass ratio of SiO2 and Fe2O3 is: SiO2≥99%, Fe2O3≤0.05%; in the titanium white, the mass ratio of TiO2 is: TiO2≥99%.

[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 tapped, and is quickly drawn into a glass filament of 1.2-1.5 meters for detection. The detection requirement is that there is no knot within 1 meter of the glass filament, and the melting is continued for 15 minutes to complete the melting.

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

[0046] The product prepared by the present application is applied to a blank with cast iron as the base body, and the firing temperature of the finished product is 780-800℃.

[0047] 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 high-temperature matte glaze without fluorinated salt and nitrate salt has a good porcelain surface, excellent high-temperature firing performance and matte performance, and is widely used in cast iron enameling products.

[0048] Example 2

[0049] The rest is the same as Example 1, except that:

[0050] The mass parts of each component in step (1) are: quartz 34 parts, borax pentahydrate 13 parts, titanium white 4 parts, sodium carbonate 18 parts, calcium carbonate 6 parts, barium carbonate 3 parts, aluminum oxide 17 parts, sodium tripolyphosphate 3 parts, potassium carbonate 4 parts, and lithium carbonate 3 parts.

[0051] In step (5), the borosilicate glass body melted is rapidly cooled by a tabletting process.

[0052] Example 3

[0053] The rest is the same as example 1, except that:

[0054] In step (1), the mass parts of each component are: quartz 35 parts, borax pentahydrate 12 parts, titanium white 3 parts, sodium carbonate 18 parts, calcium carbonate 5 parts, barium carbonate 4 parts, alumina 16 parts, sodium tripolyphosphate 4 parts, potassium carbonate 5 parts, and lithium carbonate 2 parts.

[0055] Example 4

[0056] The rest is the same as example 1, except that:

[0057] In step (1), the mass parts of each component are: quartz 36 parts, borax pentahydrate 12 parts, titanium white 3 parts, sodium carbonate 19 parts, calcium carbonate 5 parts, barium carbonate 3 parts, alumina 16 parts, sodium tripolyphosphate 2 parts, potassium carbonate 3 parts, and lithium carbonate 4 parts.

[0058] Comparative Example 1

[0059] The rest is the same as example 1, except that: in step (1), the mass parts of each component are: borax pentahydrate 12.7 parts, quartz 33.4 parts, titanium white 2.5 parts, sodium fluorosilicate 3.4 parts, sodium carbonate 16.6 parts, calcium carbonate 6.1 parts, barium carbonate 2.4 parts, fluorite powder 3.3 parts, and alumina 18.4 parts.

[0060] The test results of the products obtained in the above examples and comparative examples are shown in Table 1 below.

[0061] Table 1 Test results of products obtained in examples and comparative examples

[0062]

[0063] The above examples and test results prove that the cast iron enamel high-temperature matte glaze produced by the method of the present application does not contain fluorinated salt and nitrate, no fluorinated compound is generated during preparation, and after defluorination, the properties (porcelain surface, gloss, firing temperature) of the obtained product meet the requirements of cast iron enamel high-temperature matte glaze, the fluorinated compound test result of the product shows no detection, which meets the limit requirements of SVHC (high concern substance) 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 production of existing cast iron enamel high-temperature matte glaze.

Claims

1. A high-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates, characterized in that, Its formula consists of the following components by weight: quartz 33-36 parts, borax pentahydrate 12-14 parts, titanium dioxide 3-5 parts, sodium carbonate 17-19 parts, calcium carbonate 5-7 parts, barium carbonate 2-4 parts, alumina 16-18 parts, sodium tripolyphosphate 2-4 parts, potassium carbonate 3-5 parts, and lithium carbonate 2-4 parts.

2. The high-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates as described in claim 1, characterized in that, Quartz 35-36 parts, borax pentahydrate 13-14 parts, titanium dioxide 4-5 parts, sodium carbonate 18-19 parts, calcium carbonate 6-7 parts, barium carbonate 3-4 parts, alumina 17-18 parts, sodium tripolyphosphate 3-4 parts, potassium carbonate 4-5 parts, lithium carbonate 3-4 parts.

3. The high-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, In quartz, the mass percentage of SiO2 is: SiO2≥99%.

4. The high-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, The mass percentage of Fe2O3 is: Fe2O3≤0.05%.

5. The high-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates as described in claim 1 or 2, characterized in that, The mass percentage of TiO2 in the titanium dioxide is: TiO2≥99%.

6. The method for preparing a high-temperature matte enamel 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 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 free of knots within 1 meter and then continues to be melted for 10 to 15 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 high-temperature matte enamel 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 780-800℃, excluding the endpoint value of 780℃.

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