A water-based fast-drying coating for casting and a preparation method thereof

Abstract

The present application relates to a kind of water-based quick-drying coating for casting and its preparation method, the water-based quick-drying coating is prepared by the following raw materials according to weight percentage, refractory aggregate 60~80%, binder 3~10%, suspending agent solution 0.5~5%, quick-drying aid 0.2~1.0%, dispersing agent 0.2~1.0%, defoaming agent 0.1~1.0%, water-reducing agent 0.2~1.0%, carrier liquid 14~25%.The water-based casting coating of the present application has the characteristics of short drying time, small gas evolution, high surface strength.

Description

Technical Field

[0001] This invention relates to a water-based fast-drying coating for casting and its preparation method, belonging to the field of casting coating technology. Background Technology

[0002] In the casting process, the quality of the interface between the mold (core) and the high-temperature molten metal significantly affects the quality of the casting. Applying a casting coating to its surface is a cost-effective and practical method to improve casting quality. Casting coatings can reduce surface roughness, resulting in smooth castings. They can effectively prevent sand adhesion to the casting surface, improve the surface strength of the mold (core), reduce and avoid defects such as sand holes and inclusions, regulate the cooling rate of the casting, shield harmful elements, and prevent casting defects such as porosity, sulfur enrichment, and carbon enrichment. Furthermore, they can reduce the amount of cleaning work, improve the working environment, and lower production costs. Roughly estimated, using casting coatings can reduce casting production costs by more than 5%, demonstrating significant economic benefits. In recent years, with the increasing demands for casting quality, casting coatings have become an indispensable molding material in casting production.

[0003] Foundry coatings can be classified into alcohol-based coatings and water-based coatings based on the carrier liquid. Alcohols are flammable substances; ignition and combustion can remove the carrier liquid. Therefore, alcohol-based coatings can complete the entire application and drying process within minutes, shortening the production cycle. However, they also have many drawbacks. Alcohol-based coatings mainly use methanol, ethanol, and isopropanol as carrier liquids. Methanol is toxic and has a strong, pungent odor; long-term exposure and inhalation are harmful to the physical and mental health of workers. Although ethanol is non-toxic, it is flammable and explosive, posing safety hazards during coating production, transportation, storage, and use. Alcohol-based coatings have poor suspension and workability, resulting in severe brush marks and difficulty in leveling. Alcohols are relatively expensive, increasing production costs, and their volatilization into the air pollutes the environment. Combustion produces a large amount of CO2, violating energy conservation and environmental protection requirements. Water-based coatings are non-toxic, odorless, inexpensive, have stable performance, and are safe and environmentally friendly, aligning with the concept of green coating development. Therefore, water-based coatings have significant advantages over alcohol-based coatings in terms of production cost, coating performance, and safety and environmental protection, making them the preferred choice for developing and promoting green and environmentally friendly coatings.

[0004] With increasingly stringent safety and environmental regulations and the growing acceptance of green and sustainable development concepts, the application of alcohol-based coatings is being restricted and gradually replaced by high-performance, environmentally friendly water-based fast-drying coatings. Water-based fast-drying coatings for foundry applications can achieve rapid drying at room temperature (25±1℃), saving energy and reducing emissions, while being safe and environmentally friendly, offering significant economic and social benefits.

[0005] As early as 1979, the Moscow Machine Tool Foundry developed a self-hardening water-based coating for chilled sand cores. This coating was made from polyvinyl alcohol acetal resin powder, drying oil, water glass, and talc, and was environmentally friendly with good suspension and workability. However, it had a slow drying speed, taking about 5 hours to fully dry, and produced a relatively large amount of gas. Currently, water-based coatings commonly use inorganic binders such as water glass, silica sol, and clay, and organic binders such as polyvinyl alcohol, polyacetic acid emulsion, and water-soluble phenolic resin. These binders result in long drying times and slow drying speeds for water-based coatings. Southeast University developed a polyvinyl alcohol water-based self-drying coating (CN85100565A), which has a self-drying time of 24 hours. Feng Shengshan et al. invented a water-based self-drying / fast-drying sand casting coating and its preparation method (CN103878302B). The invention uses room temperature self-crosslinking styrene-acrylic emulsion, fast-drying silica sol, water-reducing agent, sintering stripping aid and other materials to prepare the coating, and the coating drying time is 90-105 min.

[0006] The main reason limiting the widespread application of water-based casting coatings is the long drying time, which often requires specialized equipment for drying. This not only increases production costs but also extends the production cycle. Furthermore, some products suffer from problems such as high gas emission and low surface strength. Research and application of binder systems for room-temperature, self-curing, and fast-drying water-based coatings are key technologies for the widespread use of these products. While using acrylic emulsions to prepare water-based coatings can achieve rapid room-temperature drying, no related technical reports have been found to date. Summary of the Invention

[0007] This invention provides a water-based fast-drying coating for casting and its preparation method, aiming to solve the problems of long drying time, large gas generation, and low surface strength of existing water-based casting coatings.

[0008] Technical solution:

[0009] This invention proposes a water-based quick-drying coating for casting, which is prepared from the following raw materials in weight percentage: 60-80% refractory aggregate, 3-10% binder, 0.5-5% suspending agent solution, 0.2-1.0% quick-drying agent, 0.2-1.0% dispersant, 0.1-1.0% defoamer, 0.2-1.0% water-reducing agent, and 14-25% carrier liquid.

[0010] Furthermore, the refractory aggregate includes zircon powder, white fused alumina powder, brown fused alumina powder, mullite powder, high-alumina bauxite powder, quartz powder, graphite powder, and iron oxide, wherein two or more of these are combined in any proportion.

[0011] Furthermore, the adhesive comprises an organic adhesive and an inorganic adhesive in a ratio of 3-4:4-8. The organic adhesive is an acrylic emulsion or a modified acrylic emulsion, or a combination of the two in any proportion. The inorganic adhesive is sodium-based bentonite.

[0012] Furthermore, the minimum film-forming temperature of the acrylic emulsion is 20–60°C, the glass transition temperature is 20–65°C, and the pH is 7–8; the modified acrylic emulsion is an acrylic emulsion modified with the aim of increasing the minimum film-forming temperature and the glass transition temperature.

[0013] Furthermore, the suspending agent is one of CMC, xanthan gum, polyacrylamide, and sodium alginate, or a combination of two or more of them in any proportion.

[0014] Furthermore, the fast-drying agent is one of propylene glycol phenyl ether, propylene glycol butyl ether, trimethylpentane isobutyrate monoester, trimethylolpropane diallyl ether, or a combination of two or more of them in any proportion.

[0015] Furthermore, the dispersant is one of polyphosphate, polyacrylate, and polycarboxylate, or a combination of two or more of them in any proportion.

[0016] Furthermore, the defoamer is one of n-butanol, mineral oil-based high-efficiency defoamer, or organosilicon-modified defoamer, or a combination of two or more of them in any proportion.

[0017] Furthermore, the water-reducing agent is one of polycarboxylate water-reducing agent, naphthalene sulfonate water-reducing agent, and calcium lignosulfonate, or a combination of two or more of them in any proportion.

[0018] Another aspect of this invention proposes a method for preparing a water-based quick-drying coating for casting, the method comprising the following steps:

[0019] (1) Prepare a 1-3% aqueous suspension solution, disperse it at high speed to form a suspension solution, let it stand for 24 hours, and then use it.

[0020] (2) Weigh 0.2-1.0% dispersant, 0.2-1.0% quick-drying agent, 0.2-1.0% water-reducing agent, 0.5-5% suspending agent solution from step (1), 3-10% binder, and 14-25% carrier liquid by mass percentage, disperse for 5-10 minutes, and prepare water-based coating liquid slurry;

[0021] (3) Accurately weigh 60-80% of the refractory aggregate, dry mix for 5-10 minutes, and prepare water-based coating refractory aggregate;

[0022] (4) Mix 18.6-43% water-based coating liquid slurry and 60-80% refractory aggregate by mass percentage, grind at high speed of 800-1200 rpm for 30-40 min, then stir at low speed of 100-300 rpm and add 0.1-1.0% defoamer to eliminate bubbles;

[0023] (5) Discharge and fill to obtain a water-based quick-drying coating for casting.

[0024] Beneficial effects:

[0025] This invention utilizes a combination of room-temperature self-crosslinking curing acrylic emulsion as an organic binder and a fast-drying agent, significantly improving the drying speed and surface strength of water-based coatings and solving technical problems such as excessively long drying time and poor moisture resistance. Adding an appropriate amount of water-reducing agent effectively reduces the amount of carrier water used, achieving a high solids content in the water-based coating. Adding an appropriate amount of suspending agent gives the coating excellent suspension properties, maintaining good workability and leveling performance despite the high solids content. The casting water-based fast-drying coating prepared by this invention achieves rapid drying at room temperature, and the dried coating film exhibits strong moisture resistance, embodying the development concepts of energy conservation, emission reduction, and environmental protection. Production verification shows that the casting surface is smooth and flat, free from casting defects such as porosity and sand adhesion, improving casting quality and meeting the requirements of casting production processes.

[0026] The water-based quick-drying coating for cast steel prepared by this invention has a viscosity of 15-25s, a solid content of ≥75wt%, and good workability; a suspension rate of ≥98% after 48h; a gas evolution of ≤8ml / g, which is low and avoids defects such as porosity in castings; at room temperature, a 500μm coating film dries in ≤60min, shortening the production cycle; the dried coating film has high surface strength, good moisture resistance, and a high-temperature thermal cracking level of I.

[0027] The water-based quick-drying coating for cast iron prepared by this invention has a room temperature drying time of ≤60min, a gas emission of ≤7.9ml / g, and a wear loss of ≤0.03g.

[0028] This invention employs a method combining low-speed stirring and high-speed grinding, resulting in a simple and low-cost production process suitable for mass production. Production verification has shown that the castings have smooth and flat surfaces, free from casting defects such as sand adhesion and porosity, meeting casting process requirements and demonstrating broad application prospects. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the drying mechanism of the water-based fast-drying coating of the present invention;

[0030] Figure 2 The infrared spectrum of the acrylic emulsion, an organic binder for the water-based fast-drying coating of this invention, and the infrared spectrum of the acrylic emulsion after adding a fast-drying additive are shown in the figure. Curve A is the infrared spectrum of the acrylic emulsion without the fast-drying additive, and curve B is the infrared spectrum of the acrylic emulsion after adding the fast-drying additive.

[0031] Figure 3 The images show the microstructure of the water-based quick-drying coating after drying, as observed under a scanning electron microscope. Figures a, b, c, and d show the microstructure of the coating at magnifications of 190x, 500x, 800x, and 1800x, respectively. Detailed Implementation

[0032] To make the technical solutions, preparation methods and beneficial effects of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0033] A water-based quick-drying coating for casting comprises, by weight percentage: 60-80% refractory aggregate, 3-10% binder, 0.5-5% suspending agent, 0.2-1.0% quick-drying agent, 0.2-1.0% dispersant, 0.1-1.0% defoamer, 0.2-1.0% water-reducing agent, and 14-25% carrier liquid. Preferably, the composition is 73-80% refractory aggregate, 5-10% binder, 0.5-3% suspending agent, 0.2-1.0% quick-drying agent, 0.2-1.0% dispersant, 0.1-1.0% defoamer, 0.2-1.0% water-reducing agent, and 14-25% carrier liquid.

[0034] The refractory aggregates include zircon powder, high-alumina bauxite powder, mullite powder, white fused alumina powder, brown fused alumina powder, quartz powder, graphite powder, and iron oxide. These refractory aggregates are widely available and inexpensive, meeting the requirements of casting production processes. Zircon powder, in particular, has high refractoriness, low thermal expansion, and is neutral to weakly acidic at high temperatures, commonly used as refractory aggregate for cast steel and cast iron parts. High-alumina bauxite has low thermal expansion, high-temperature volume stability, high refractoriness, and good slag resistance. Mullite is a high-quality refractory aggregate with advantages such as uniform expansion, good thermal shock stability, low high-temperature creep, high hardness, and good chemical corrosion resistance. Fused alumina powder is high-purity Al2O3 with a mass fraction of 99-99.5%. White fused alumina has an Al2O3 content ≥97%, while brown fused alumina has an Al2O3 content ≥92.5%. The density of fused alumina is 3.85-3.9 g / cm³. 3With a melting point of 2000–2050℃, high thermal conductivity, and small and uniform thermal expansion, it exhibits weak alkalinity or neutrality at high temperatures and good chemical stability. High-alumina bauxite, mullite powder, and corundum powder are mainly used as refractory aggregates for cast steel. Quartz powder is a white, transparent powder, its main component being SiO2, with a melting point of 1713℃. Quartz powder is widely available and inexpensive. Chemical sand adhesion in castings (2FeO + SiO2 = Fe2SiO4) forms a ceramic-like layer of fritillary olivine on the casting surface, affecting the surface quality of the casting, being difficult to remove, and increasing production costs. Adding flake graphite to coatings is an effective way to prevent chemical sand adhesion. Graphite powder is a neutral refractory filler with high quenching ability for metals, is not wetted by metals or metal oxides, does not chemically react with high-temperature molten metal, has high refractoriness, a melting point above 3000℃, low density, easily suspended in water, abundant sources, and low price, making it a commonly used refractory filler in cast iron production. Iron oxide can compensate for the consumption of oxides, promote the formation of an easy-to-peel layer, and also increase the vividness of the paint color, improving the visibility of the paint application quality. High-alumina bauxite, mullite powder, quartz powder, graphite powder, and iron oxide can be used as refractory aggregates for cast iron. The refractory aggregates for cast steel and cast iron coatings are not entirely the same, the main difference being their refractoriness. Because the casting temperature of cast steel is higher than that of cast iron, the refractoriness of aggregates used for cast steel is higher, while that used for cast iron is relatively lower. Cast iron parts are easily oxidized during the casting process, so a reducing atmosphere should be maintained during casting. Graphite powder can be added, but it is not suitable for cast steel, as graphite powder causes carburization in cast steel parts, affecting the quality of the casting. Iron oxide can compensate for the consumption of oxides and promote the formation of an easy-to-peel coating.

[0035] The refractory aggregates include zircon powder (150-200 mesh), white corundum powder (150-200 mesh), brown corundum powder (150-200 mesh), mullite powder (200-320 mesh), high-alumina bauxite (200-320 mesh), quartz powder (200-320 mesh), graphite powder (200-320 mesh), and iron oxide (200-320 mesh).

[0036] Zircon powder, high-alumina bauxite, mullite powder, and corundum powder are used as refractory aggregates for cast steel, with two or more of these materials combined.

[0037] High-alumina bauxite, mullite powder, quartz powder, graphite powder, and iron oxide are used as refractory aggregates for cast iron, with two or more of these materials combined.

[0038] The binder comprises an organic binder and an inorganic binder in a ratio of 3-4:4-8. The organic binder is an acrylic emulsion or a modified acrylic emulsion, or a combination of the two in any proportion. The inorganic binder is sodium bentonite. The organic binder, being an acrylic emulsion, is formed by emulsifying copolymers of methyl methacrylate and acrylates. It exhibits strong affinity for refractory powders, high adhesion, and excellent water and chemical resistance in the coating film. It can self-crosslink and cure at room temperature with a fast film-forming speed. This type of binder has a specific minimum film-forming temperature (MFT) and glass transition temperature (Tg): MFT is between 20 and 60°C, Tg is between 20 and 65°C, and pH is between 7 and 8. With the synergistic effect of a matching fast-drying additive, the coating rapidly cures at room temperature (25±1°C), resulting in a high surface strength and strong moisture resistance. The modified acrylic emulsion is an acrylic emulsion modified to increase the minimum film-forming temperature and glass transition temperature.

[0039] The inorganic binder is sodium-based bentonite, which is a good binder at room temperature. When heated to above 700℃, it begins to form a glassy structure, and when the temperature is above 1000℃, it softens significantly. This change is extremely beneficial to the sintering of refractory aggregates in coatings, and therefore it is also a good high-temperature binder.

[0040] Organic binders, also known as low-temperature binders, provide room-temperature strength for the coating, preventing mold (core) damage caused by vibration or accidental minor collisions during handling. Inorganic binders, also known as high-temperature binders, ensure sufficient strength of the coating during pouring, preventing casting defects caused by molten metal penetration. Therefore, a single binder cannot meet casting requirements, and an organic-inorganic composite binder should be used.

[0041] The suspending agent is one of CMC, xanthan gum, polyacrylamide, and sodium alginate, or a combination of two or more of them. The suspending agent is pre-dispersed and ground with water at high speed to prepare a 1-3% aqueous suspension solution, which is then allowed to stand for 24 hours to allow for complete defoaming. The suspending agent forms a spatial network or chain structure in the coating, significantly improving the coating's suspension performance.

[0042] The fast-drying agent is one of propylene glycol phenyl ether, propylene glycol butyl ether, trimethylpentane isobutyrate monoester, and trimethylolpropane diallyl ether, or a combination of two or more of them. Acrylic adhesives have a minimum temperature threshold (MFT). Coatings obtained below the MFT temperature are cracked and lack adhesion and mechanical strength. Only above the MFT temperature can an ideal coating be obtained. The fast-drying agent can significantly reduce the MFT of organic adhesives to room temperature and below, allowing the coating to quickly form a continuous film with a certain mechanical strength.

[0043] The water-reducing agent is one of polycarboxylate water-reducing agents, naphthalene sulfonate water-reducing agents, and calcium lignosulfonate, or a combination of two or more of them. Excessive water content in water-based coatings can affect their drying time. The addition of a water-reducing agent can effectively reduce the amount of carrier water used. The addition amount (mass percentage) is 0.2-1.0%, resulting in a water reduction rate of 10-20%, thus improving the drying speed of the coating.

[0044] The defoamer is one of n-butanol, mineral oil-based high-efficiency defoamers, and organosilicon-modified defoamers, or a combination of two or more of them.

[0045] The dispersant is one of polyphosphate, polyacrylate, and polycarboxylate, or a combination of two or more of these materials.

[0046] The drying mechanism of the water-based coating of this invention is as follows: Figure 1 The acrylic emulsion binder used in the coating of this invention has good Tg and MFT. When combined with a fast-drying additive, it can effectively reduce the MFT of the binder, enabling the coating to form a film rapidly at room temperature and below. Combined with infrared spectroscopy, such as... Figure 2 And the detection of scanning electron microscopy, such as Figure 3 The drying mechanism of water-based coatings was found to be a complex and dynamic process: under the action of surface tension and capillary force, binder particles come into contact with each other, accumulate, cross-link, and are tightly bonded to refractory aggregate particles, eventually forming a uniform and continuous coating film with mechanical strength.

[0047] The water-based quick-drying coating of the present invention can be used in the fields of cast steel and cast iron, specifically:

[0048] A method for preparing a water-based quick-drying coating for cast steel is described in Examples 1-5.

[0049] Example 1

[0050] Accurately weigh 2g of CMC and 98g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; add 3g of suspension solution, 0.6g of polycarboxylate dispersant, 4g of sodium bentonite paste, 4g of acrylic emulsion, 0.5g of propylene glycol phenyl ether, 0.75g of polycarboxylate superplasticizer, and 18g of water, disperse for 5 minutes to prepare a water-based coating liquid slurry; add 20g of zircon powder, 30g of white corundum powder, and 30g of high-alumina bauxite powder, grind at high speed of 1200 rpm for 30 minutes, then stir at low speed of 300 rpm and add 0.2g of organosilicon modified defoamer, disperse for 5 minutes to obtain a water-based quick-drying coating for cast steel.

[0051] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 16s, drying time 60min, gas emission 7.8ml / g, and abrasion loss 0.0186g.

[0052] Example 2

[0053] Accurately weigh 2g of CMC, 1g of polyacrylamide, and 97g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 1g of the suspension solution, 0.6g of polycarboxylate dispersant, 4g of sodium bentonite paste, 5g of acrylic emulsion, 0.5g of propylene glycol butyl ether, 0.75g of naphthalene sulfonate water-reducing agent, and 16g of water, disperse for 6 minutes to prepare a water-based coating liquid slurry; add 10g of zircon powder, 40g of white corundum powder, and 30g of high-alumina bauxite powder, grind at high speed of 800 rpm for 35 minutes, stir at low speed of 100 rpm and add 0.2g of n-butanol, disperse for 6 minutes to obtain a water-based quick-drying coating for cast steel.

[0054] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 20s, drying time 55min, gas emission 7.3ml / g, and abrasion loss 0.0160g.

[0055] Example 3

[0056] Accurately weigh 1g xanthan gum and 99g water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 3g suspension solution, 0.6g polycarboxylate dispersant, 3g sodium bentonite paste, 5g acrylic emulsion, 0.5g trimethylpentanediol isobutyrate monoester, 0.75g polycarboxylate superplasticizer, and 20g water, disperse for 7 minutes to prepare a water-based coating liquid slurry; then add 10g zircon powder, 40g white corundum powder, 20g high-alumina bauxite, and 10g mullite powder, grind at high speed of 1000 rpm for 30 minutes, stir at low speed of 200 rpm and add 0.2g organosilicon defoamer, disperse for 7 minutes to obtain a water-based quick-drying coating for cast steel.

[0057] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 23s, drying time 60min, gas emission 7.5ml / g, and abrasion loss 0.0195g.

[0058] Example 4

[0059] Accurately weigh 1g xanthan gum and 99g water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 1g of the suspension solution, 0.6g of polycarboxylate dispersant, 3g of sodium bentonite paste, 8g of modified acrylic emulsion, 0.6g of trimethylolpropane diallyl ether, 0.5g of calcium lignosulfonate, and 16g of water, disperse for 8 minutes to prepare a water-based coating liquid slurry; then add 20g of zircon powder, 30g of brown corundum powder, and 30g of high-alumina bauxite, grind at high speed of 1100 rpm for 40 minutes, stir at low speed of 200 rpm and add 0.2g of silicone defoamer, disperse for 8 minutes to obtain a water-based quick-drying coating for cast steel.

[0060] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 18s, drying time 50min, gas emission 7.9ml / g, and abrasion loss 0.0135g.

[0061] Example 5

[0062] Accurately weigh 2g of CMC and 98g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 2g of the suspension solution, 0.6g of polycarboxylate dispersant, 3g of sodium bentonite paste, 5g of acrylic emulsion, 0.1g of propylene glycol phenyl ether, 0.2g of propylene glycol butyl ether, 0.3g of polycarboxylate superplasticizer, 0.2g of naphthalene sulfonate superplasticizer, and 17g of water, disperse for 9 minutes to prepare a water-based coating liquid slurry; then add 50g of white corundum powder and 30g of high-alumina bauxite powder, grind at high speed of 1100 rpm for 35 minutes, stir at low speed of 200 rpm and add 0.2g of organosilicon modified defoamer, disperse for 9 minutes to obtain a water-based quick-drying coating for cast steel.

[0063] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 20s, drying time 60min, gas emission 7.1ml / g, and abrasion loss 0.0162g.

[0064] Comparative Example 1

[0065] Accurately weigh 0.8g of polycarboxylate dispersant, 8g of vinyl acetate emulsion, 2g of silica sol, 3g of CMC solution, and 30g of water, disperse for 8 minutes, add 70g of chromite powder, grind at high speed for 35 minutes, add 0.3g of organosilicon defoamer, disperse for 8 minutes, and obtain a water-based coating.

[0066] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured as follows: viscosity 15s, drying time 150min, gas emission 9.6ml / g, and abrasion loss 0.0538g.

[0067] A method for preparing a water-based quick-drying coating for cast iron is described in Examples 6-10.

[0068] Example 6

[0069] Accurately weigh 2g of CMC and 98g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 2g of the suspension solution, 0.5g of polycarboxylate dispersant, 0.5g of propylene glycol phenyl ether, 0.75g of polycarboxylate superplasticizer, 3g of sodium bentonite paste, 4g of acrylic emulsion, and 18g of water, disperse for 10 minutes to prepare a water-based coating liquid slurry; then add 40g of high-alumina bauxite powder, 25g of mullite powder, 3g of flake graphite, 5g of quartz powder, and 5g of iron oxide, grind at high speed of 800 rpm for 40 minutes, stir at low speed of 100 rpm, and finally add 0.2g of organosilicon defoamer to obtain a water-based quick-drying coating for cast iron.

[0070] Example 7

[0071] Accurately weigh 1g xanthan gum and 99g water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 3g of the suspension solution, 0.5g of polycarboxylate dispersant, 0.5g of trimethylpentanediol isobutyrate monoester, 0.75g of polycarboxylate superplasticizer, 3g of sodium bentonite paste, 4g of modified acrylic emulsion, and 16g of water, disperse for 5 minutes to prepare a water-based coating liquid slurry; then add 40g of high-alumina bauxite powder, 25g of mullite powder, 5g of flake graphite, 5g of quartz powder, and 3g of iron oxide, grind at high speed for 30 minutes, and finally add 0.2g of organosilicon defoamer to obtain a water-based quick-drying coating for cast iron.

[0072] Example 8

[0073] Accurately weigh 3g of CMC and 97g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 3g of the suspension solution, 0.5g of polycarboxylate dispersant, 0.5g of propylene glycol butyl ether, 0.75g of polycarboxylate superplasticizer, 3g of sodium bentonite paste, 5g of acrylic emulsion, and 20g of water, disperse for 8 minutes to prepare a water-based coating liquid slurry; then add 45g of high-alumina bauxite powder, 25g of mullite powder, 3g of flake graphite, 3g of quartz powder, and 4g of iron oxide, grind at high speed of 1000 rpm for 35 minutes, stir at low speed of 200 rpm, and finally add 0.2g of organosilicon defoamer to obtain a water-based quick-drying coating for cast iron.

[0074] Example 9

[0075] Accurately weigh 1g xanthan gum and 99g water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; mix 3g of the suspension solution, 0.6g of polycarboxylate dispersant, 0.3g of propylene glycol phenyl ether, 0.2g of propylene glycol butyl ether, 0.5g of polycarboxylate superplasticizer, 3g of sodium bentonite paste, 8g of acrylic emulsion, and 16g of water, disperse for 8 minutes to prepare a water-based coating liquid slurry; then add 45g of high-alumina bauxite powder, 25g of mullite powder, 5g of flake graphite, 5g of quartz powder, and 5g of iron oxide, grind at high speed of 900 rpm for 35 minutes, stir at low speed of 200 rpm, and finally add 0.2g of organosilicon defoamer to obtain a water-based quick-drying coating for cast iron.

[0076] Example 10

[0077] Accurately weigh 2g of CMC and 98g of water, grind at high speed to prepare a suspension solution, let stand for 24 hours, and set aside for use; 2g of suspension solution, 0.6g of polycarboxylate dispersant, 0.5g of propylene glycol phenyl ether, 0.75g of polycarboxylate superplasticizer, 3g of sodium bentonite paste, 6g of acrylic emulsion, and 17g of water, disperse for 8 minutes to prepare a water-based coating liquid slurry; then add 45g of high-alumina bauxite, 25g of mullite powder, 2g of flake graphite, 5g of quartz powder, and 5g of iron oxide, grind at high speed of 1200 rpm for 35 minutes, stir at low speed of 200 rpm, and finally add 0.2g of mineral oil-based high-efficiency defoamer to obtain a water-based quick-drying coating for cast iron.

[0078] Comparative Example 2

[0079] Accurately weigh 4g of CMC suspending agent, 2g of polycarboxylate dispersant, 2g of styrene-acrylic emulsion, 8g of quick-drying silica sol, 0.2g of polycarboxylate superplasticizer, and 40g of water. Disperse for 8 minutes to prepare a water-based coating liquid slurry. Then add 80g of chromite powder and grind at high speed for 35 minutes. Finally, add an appropriate amount of 1g of organosilicon defoamer to obtain the water-based coating.

[0080] According to the JB / T 9226 standard and the QGZ-24 automatic paint film drying time tester, the technical indicators of the coating were measured, and the results are shown in Table 1.

[0081] Table 1 Technical Specifications of Water-Based Coatings

[0082] Serial Number Drying time / min Gas production, ml / g Abrasion resistance / g Example 6 60.0 7.5 0.0196 Example 7 55.0 7.6 0.0145 Example 8 60.0 7.5 0.0165 Example 9 50.0 7.9 0.0135 Example 10 55.0 7.2 0.0152 Comparative Example 120.0 9.3 0.0856

[0083] The water-based quick-drying coating for cast iron of this invention has a room temperature drying time of ≤60min, a gas emission of ≤7.9ml / g, and a wear loss of ≤0.03g.

[0084] This invention employs a method combining low-speed stirring and high-speed grinding, resulting in a simple and low-cost production process. Production verification has shown that the castings have smooth and flat surfaces, free from casting defects such as sand adhesion and porosity, meeting casting process requirements and demonstrating broad application prospects.

Claims

1. A water-based quick-drying coating for casting, characterized in that, It is prepared from the following raw materials by weight percentage: refractory aggregate 60-80%, binder 3-10%, suspending agent solution 0.5-5%, quick-drying agent 0.2-1.0%, dispersant 0.2-1.0%, defoamer 0.1-1.0%, water-reducing agent 0.2-1.0%, and carrier liquid 14-25%; The adhesive comprises an organic adhesive and an inorganic adhesive in a ratio of 3-4:4-8. The organic adhesive is an acrylic emulsion or a modified acrylic emulsion, or a combination of the two in any proportion. The inorganic adhesive is sodium-based bentonite. The acrylic emulsion has a minimum film-forming temperature of 20~60℃, a glass transition temperature of 20~65℃, and a pH of 7~8; the modified acrylic emulsion is an acrylic emulsion modified with the aim of increasing the minimum film-forming temperature and glass transition temperature. The fast-drying agent is one of propylene glycol phenyl ether, propylene glycol butyl ether, trimethylpentane isobutyrate monoester, trimethylolpropane diallyl ether, or a combination of two or more of them in any proportion.

2. The casting water-based quick-drying coating according to claim 1, characterized in that, The refractory aggregate includes zircon powder, white fused alumina powder, brown fused alumina powder, mullite powder, high-alumina bauxite powder, quartz powder, graphite powder, and iron oxide, in any combination of two or more of these in any proportion.

3. The casting water-based quick-drying coating according to claim 1, characterized in that, The suspending agent is one of CMC, xanthan gum, polyacrylamide, and sodium alginate, or a combination of two or more of them in any proportion.

4. The casting water-based quick-drying coating according to claim 1, characterized in that, The dispersant is one of polyphosphate, polyacrylate, and polycarboxylate, or a combination of two or more of them in any proportion.

5. The casting water-based quick-drying coating according to claim 1, characterized in that, The defoamer is one of n-butanol, mineral oil-based high-efficiency defoamers, or organosilicon-modified defoamers, or a combination of two or more of them in any proportion.

6. The casting water-based quick-drying coating according to claim 1, characterized in that, The water-reducing agent is one of polycarboxylate water-reducing agent, naphthalene sulfonate water-reducing agent, and calcium lignosulfonate, or a combination of two or more of them in any proportion.

7. A method for preparing a water-based quick-drying coating for casting as described in claim 1, characterized in that, The method includes the following steps: (1) Prepare a 1-3% concentration of suspending agent aqueous solution, grind at high speed to make a suspending agent solution, let stand for 24 hours, and wait for use; (2) Weigh 0.2-1.0% dispersant, 0.2-1.0% quick-drying agent, 0.2-1.0% water-reducing agent, 0.5-5% suspending agent solution from step (1), 3-10% binder, and 14-25% carrier liquid by mass percentage, disperse for 5-10 minutes, and prepare water-based coating liquid slurry; (3) Accurately weigh 60-80% of the refractory aggregate, dry mix for 5-10 minutes to prepare water-based coating refractory aggregate; (4) Mix 18.6-43% water-based coating liquid slurry and 60-80% refractory aggregate by mass percentage, grind at high speed of 800-1200 rpm for 30-40 min, then stir at low speed of 100-300 rpm and add 0.1-1.0% defoamer to eliminate bubbles; (5) Discharge and fill to obtain a water-based quick-drying coating for casting.

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