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

Abstract

The application discloses a cast iron enamel low-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, magnesium carbonate, sodium tripolyphosphate, potassium carbonate, lithium carbonate and potassium feldspar 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, the fluoride content of the product is not detected through detection, and the product meets the limit value requirements of the EU REACH regulation. Meanwhile, the matte glaze has good enamel surface, low-temperature sintering performance and excellent matte performance, is suitable for a cast iron substrate, has a sintering 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 present application belongs to the technical field of enamel, and particularly relates to a cast iron enamel low-temperature matte glaze free of fluorinated salt and nitrate salt and a preparation method and application thereof. BACKGROUND

[0002] The cast iron enamel low-temperature matte glaze requires low-temperature (740-760 DEG C) firing, and has no defects in appearance, a smooth porcelain surface and a gloss (less than or equal to 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 low-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 field of enamel technology. 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 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 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 not only is a necessary choice to respond to regulations, but also is 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, a cast iron enamel low-temperature matte glaze without fluorinated salt and nitrate salt, as well as a preparation method and application thereof are provided.

[0013] The fluorine-free salt-free nitrate-free cast iron enamel low-temperature matte glaze of the present application is composed of the following components in the following mass parts: quartz 43-46 parts, borax pentahydrate 10-13 parts, titanium white 4-6 parts, sodium carbonate 18-22 parts, magnesium carbonate 5-7 parts, sodium tripolyphosphate 3-5 parts, potassium carbonate 5-7 parts, lithium carbonate 2-4 parts, and potassium feldspar 6-8 parts.

[0014] Further, the quartz is 45-46 parts, the borax pentahydrate is 10-11 parts, the titanium white is 5-6 parts, the sodium carbonate is 20-22 parts, the magnesium carbonate is 6-7 parts, the sodium tripolyphosphate is 4-5 parts, the potassium carbonate is 6-7 parts, the lithium carbonate is 3-4 parts, and the potassium feldspar is 7-8 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 fluorine-free salt-free nitrate-free cast iron enamel low-temperature matte glaze comprises the following steps:

[0017] (1) the raw materials of each component are weighed according to the above 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, 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 glass filament of 1.2-1.5 meters for detection, with the detection requirement being: no knot 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, and the product is obtained.

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

[0023] The application of the above-mentioned fluorine-free salt-free nitrate-free cast iron enamel low-temperature matte glaze is applied to a blank with a cast iron base, and the firing temperature of the finished product is 740-760℃.

[0024] In addition, in the formula of the present application, the components and amount of the non-fluoride fluxing agent are adjusted, so that even without the fluxing of fluorine-free salt, the melting can be completed as required; the present application increases the phosphate in the formula of the cast iron enamel low-temperature matte glaze, which provides [PO4]3- The group promotes feldspar nucleation, and on the other hand forms a eutectic complex fluxing system of'multi-carbonate + phosphate + borate' to strengthen fluxing, and the components synergistically improve the gloss and firing performance of the enamel.

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

[0026] (1) The 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 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: the present application completely removes fluoride (fluorite, sodium fluorosilicate, etc.), eliminates the source of fluoride salt crystallization 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 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 low-temperature firing adaptability: the eutectic complex fluxing system (multi-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 addition of phosphate provides [PO4] 3- The group promotes feldspar nucleation, and on the other hand forms a eutectic complex fluxing system of'multi-carbonate + phosphate + borate' to strengthen 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 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 embodiments, but the present application is not limited thereto.

[0033] The equipment used in the embodiments 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 embodiment of the present application meets the requirements of the industrial grade.

[0038] Embodiment 1

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

[0040] Quartz 43 parts, borax pentahydrate 13 parts, titanium dioxide 6 parts, sodium carbonate 18 parts, magnesium carbonate 7 parts, sodium tripolyphosphate 5 parts, potassium carbonate 5 parts, lithium carbonate 2 parts, potassium feldspar 6 parts.

[0041] In the quartz, the mass ratio of SiO2 and Fe2O3 is: SiO2≥99%, Fe2O3≤0.05%; in the titanium dioxide, 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, with the detection requirement being: no knot within 1 meter of the glass filament, and continuing to melt for 15 minutes is the completion of 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 740-760℃.

[0047] The product obtained in Embodiment 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 low-temperature matte glaze without fluorinated salt and nitrate salt has a good porcelain surface, excellent low-temperature firing performance and matte performance, and is widely applied to cast iron enameling products.

[0048] Embodiment 2

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

[0050] In step (1), the mass parts of each component are: quartz 44 parts, borax pentahydrate 12 parts, titanium dioxide 5 parts, sodium carbonate 19 parts, magnesium carbonate 6 parts, sodium tripolyphosphate 4 parts, potassium carbonate 6 parts, lithium carbonate 3 parts, potassium feldspar 7 parts.

[0051] In step (5), the rapid cooling of the melted borosilicate glass body is carried out by a tablet pressing process.

[0052] Example 3

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

[0054] The mass parts of each component in step (1) are: quartz 45 parts, borax pentahydrate 11 parts, titanium white 4 parts, sodium carbonate 20 parts, magnesium carbonate 5 parts, sodium tripolyphosphate 3 parts, potassium carbonate 7 parts, lithium carbonate 4 parts, potassium feldspar 8 parts.

[0055] Example 4

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

[0057] The mass parts of each component in step (1) are: quartz 46 parts, borax pentahydrate 10 parts, titanium white 4 parts, sodium carbonate 22 parts, magnesium carbonate 5 parts, sodium tripolyphosphate 3 parts, potassium carbonate 5 parts, lithium carbonate 2 parts, potassium feldspar 6 parts.

[0058] Comparative Example 1

[0059] The rest is the same as example 1, except that: the mass parts of each component in step (1) are: borax pentahydrate 9.4 parts, quartz 43.0 parts, titanium white 5.8 parts, sodium fluosilicate 4.8 parts, sodium carbonate 16.7 parts, sodium nitrate 1.8 parts, potassium feldspar 5.2 parts, fluorite powder 3.3 parts, magnesium oxide 5.2 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 each example and comparative example

[0062]

[0063] The above examples and test results prove that the cast iron enamel low-temperature matte glaze produced by the method of the present application does not contain fluorinated salt and nitrate salt, 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 low-temperature matte 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 existing cast iron enamel low-temperature matte glaze in the production process, such as fluorinated compound gas emission polluting the environment and fluorinated salt emission blocking environmental protection treatment facilities.

Claims

1. A low-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 43-46 parts, borax pentahydrate 10-13 parts, titanium dioxide 4-6 parts, sodium carbonate 18-22 parts, magnesium carbonate 5-7 parts, sodium tripolyphosphate 3-5 parts, potassium carbonate 5-7 parts, lithium carbonate 2-4 parts, and potassium feldspar 6-8 parts.

2. The low-temperature matte enamel glaze for cast iron that is free of fluoride salts and nitrates as described in claim 1, characterized in that, Quartz 45-46 parts, borax pentahydrate 10-11 parts, titanium dioxide 5-6 parts, sodium carbonate 20-22 parts, magnesium carbonate 6-7 parts, sodium tripolyphosphate 4-5 parts, potassium carbonate 6-7 parts, lithium carbonate 3-4 parts, potassium feldspar 7-8 parts.

3. The low-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 low-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 Fe2O3 is: Fe2O3≤0.05%.

5. The low-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 low-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 low-temperature matte enamel 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 740-760℃.

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