A foundry coating and a method for its preparation

Abstract

The application relates to the technical field of foundry coating, in particular to a foundry coating and a preparation method thereof. The foundry coating comprises the following components: 100-150 parts of refractory aggregate, 8-20 parts of binder, 25-50 parts of main solvent, 20-40 parts of auxiliary solvent, 3-8 parts of suspending agent, 1-3 parts of thickening agent, 0.5-2 parts of surfactant and 0.2-1 part of defoaming agent; the main solvent is a hydrofluoroether compound with a boiling point lower than 80 DEG C and no flash point; and the auxiliary solvent is a non-combustible fluorine-containing olefin or fluorine-containing ketone compound with a boiling point lower than 30 DEG C. The technical problem that the existing alcohol-based foundry coating is flammable and the water-based foundry coating is slow to dry is successfully solved by adopting the hydrofluoroether compound with a boiling point lower than 80 DEG C and no flash point as the main solvent and the non-combustible fluorine-containing olefin or fluorine-containing ketone compound with a lower boiling point than 30 DEG C as the auxiliary solvent, and a foundry coating with high volatilization rate and non-combustible characteristics is obtained.

Description

Technical Field

[0001] This application relates to the field of coating technology for casting, and more specifically, to a casting coating and its preparation method. Background Technology

[0002] Foundry coatings are key auxiliary materials applied to the surface of sand molds and cores in casting production. Their main function is to prevent defects such as sand adhesion and sand holes in castings and to improve the surface quality of castings.

[0003] Currently, traditional casting coatings are mainly divided into two systems: alcohol-based and water-based. However, both have significant technical drawbacks, making it difficult to balance production efficiency and safety. Alcohol-based casting coatings typically use alcohols such as methanol, ethanol, and isopropanol as solvents. Their main advantage is rapid evaporation, allowing for quick drying via ignition after application, resulting in high production efficiency. However, their fatal flaw is the serious safety hazard. The alcohol solvents used have extremely low flash points (e.g., ethanol's flash point is approximately 13°C, and methanol's is approximately 12°C), making them highly volatile during storage, transportation, and application. They can form explosive mixtures with air, potentially causing fires or explosions. Furthermore, the evaporating alcohol vapors pose a threat to the health of workers. Water-based casting coatings use water as a solvent, fundamentally solving the flammability problem and offering higher safety. However, their drying speed is extremely slow, especially in low-temperature, high-humidity environments, where drying time is significantly prolonged. To meet production schedules, additional baking equipment is often required for forced drying, which not only increases energy consumption but also reduces overall production efficiency.

[0004] Therefore, there is an urgent need for a casting coating that combines high volatility and non-flammability with the requirements of the casting process, which is of great significance for improving the safety and production efficiency of the casting industry. Summary of the Invention

[0005] The casting coating provided in this application has both a high volatility rate and non-flammability, and can meet the requirements of the casting process.

[0006] The first aspect of this application provides a casting coating, comprising: Refractory aggregate 100-150 parts, binder 8-20 parts, main solvent 25-50 parts, co-solvent 20-40 parts, suspending agent 3-8 parts, thickener 1-3 parts, surfactant 0.5-2 parts, defoamer 0.2-1 parts; The main solvent is a hydrofluoroether compound with a boiling point below 80°C and no flash point; The co-solvent is a non-flammable fluorinated olefin or fluorinated ketone compound with a boiling point below 30°C.

[0007] Preferably, the main solvent includes at least one of methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0008] Preferably, the co-solvent includes at least one of trans-1-chloro-3,3,3-trifluoropropene, 1,2-dichloro-4-trifluorobenzene, or perfluorohexanone.

[0009] Preferably, the refractory aggregate includes at least one of zircon powder, corundum powder, mullite powder, and quartz powder, and the fineness of the refractory aggregate is 200-400 mesh.

[0010] Preferably, the binder comprises at least one of silicone-modified phenolic resin, aluminum dihydrogen phosphate, or silica sol.

[0011] Preferably, the suspending agent includes at least one of organically modified bentonite, lithium-based bentonite, or attapulgite; the thickener is sodium carboxymethyl cellulose or hydroxyethyl cellulose.

[0012] Preferably, the surfactant is a fluorocarbon surfactant or a polyether-modified polysiloxane; the defoamer is a polyether defoamer or an organosilicone defoamer.

[0013] Preferably, it also includes 0.5 to 2 parts of polyvinyl butyral, a suspending agent.

[0014] A second aspect of this application provides a method for preparing the casting coating as described above, comprising the following steps: S1: Mix the suspending agent with water and stir at 60~80℃ for 30~60 minutes to activate it, and obtain the activated suspending agent slurry; S2: Mix the main solvent and the co-solvent, and stir at 300~500 rpm for 5~10 minutes; S3: Add the adhesive to the mixed solvent from step S2 and stir to dissolve; S4: Dry mix the refractory aggregate, thickener and suspending agent evenly; S5: Add the activated suspension slurry to the binder solution and disperse it evenly; then add the premixed powder, surfactant and defoamer, and disperse at high speed of 1500~2500rpm for 45~60 minutes; S6: Adjust the Baume degree to 60~85°Bé using a mixed solvent to obtain the casting coating.

[0015] The casting coating provided in this application combines a high evaporation rate with non-flammability and meets the requirements of the casting process. It effectively solves the contradiction that alcohol-based coatings, although evaporating quickly and drying efficiently, are flammable and explosive, posing serious safety hazards; while water-based coatings, although highly safe, dry extremely slowly, resulting in high energy consumption and low production efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the microstructure of the casting coating provided in this application after it has been applied to the surface of a sand mold. Figure 2 This is a schematic flowchart of the method for preparing the casting coating provided in the embodiments of this application.

[0017] Figure 3 This is a comparison chart of the percentage weight of the remaining coating provided in the embodiments of this application. Detailed Implementation

[0018] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0019] Some definitions in this article are explained below: Flash point is the lowest temperature at which, under specified test conditions, the vapor emitted from the surface of a flammable liquid or solid mixes with air and ignites upon contact with an ignition source, resulting in a flash that is immediately extinguished.

[0020] °Bé, the symbol for Baumé degree, is a unit commonly used in industry to express the concentration or relative density of liquids.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. Example

[0023] This embodiment provides a casting coating, which, by weight, comprises the following components: The mixture comprises 100-150 parts refractory aggregate, 8-20 parts binder, 25-50 parts main solvent, 20-40 parts co-solvent, 3-8 parts suspending agent, 1-3 parts thickener, 0.5-2 parts surfactant, and 0.2-1 parts defoamer; the main solvent is a hydrofluoroether compound with a boiling point below 80℃ and no flash point; the co-solvent is a non-flammable fluorinated olefin or fluorinated ketone compound with a boiling point below 30℃.

[0024] The refractory aggregate is at least one of zircon powder, corundum powder, mullite powder, and quartz powder, with a fineness of 200-400 mesh; it plays a role in preventing sand adhesion and improving refractoriness.

[0025] The binder is at least one of silicone-modified phenolic resin, aluminum dihydrogen phosphate, or silica sol; preferably silicone-modified phenolic resin, which has better heat resistance than ordinary phenolic resin and a higher high-temperature carbon residue rate, which is beneficial to improving the coating's erosion resistance.

[0026] The suspending agent is at least one of organic modified bentonite, lithium-based bentonite, or attapulgite; the thickener is sodium carboxymethyl cellulose or hydroxyethyl cellulose.

[0027] The surfactant is a fluorocarbon surfactant or a polyether-modified polysiloxane; the defoamer is a polyether defoamer or an organosilicon defoamer.

[0028] Furthermore, a suspending agent may be added to the coating, wherein the suspending agent is polyvinyl butyral, and the weight part is 0.5 to 2 parts.

[0029] The trans-1-chloro-3,3,3-trifluoropropylene is a hydrochlorofluoroolefin compound with a global warming potential (GWP) of 1, an ozone depletion potential (ODP) of 0, a boiling point of 19°C, a vapor pressure of approximately 106 kPa at 25°C, a moderate evaporation rate, and no flash point as tested according to ASTM D3278 standard. When the non-flammable diluent is mixed with the hydrofluoroether solvent, the overall solvent evaporation rate can be adjusted by regulating the ratio of the two within the range of 0.5 to 3.0 (based on butyl acetate = 1) to meet the drying speed requirements of different casting processes.

[0030] like Figure 1 As shown, Figure 1 This is a schematic diagram of the microstructure of the casting coating provided in this application after being applied to the surface of a sand mold; wherein, 1 is the casting coating provided by this invention, and 2 is the sand core.

[0031] The casting coating provided in this application completely replaces flammable alcohol solvents with hydrofluoroether solvents and non-flammable thinners. Testing has shown that the coating cannot be ignited under open flame, electric spark, or high-temperature heat sources, has no flash point, and meets the requirements of GB / T 4966-2025 for non-flammable materials, completely eliminating the risk of fire and explosion during storage, transportation, and construction. The hydrofluoroether solvent has a moderate boiling point (40~80℃), high saturated vapor pressure (approximately 30~80kPa at 25℃), and an evaporation rate comparable to or even faster than ethanol. After coating, it is surface dry in 5~15 minutes at room temperature and fully dry in 30~60 minutes, requiring no ignition drying or heating equipment. Its efficiency is comparable to alcohol-based coatings and significantly superior to water-based coatings. Through proper matching of suspending agents and hydrofluoroether solvents, the coating exhibits a settling rate of ≤5% after 24 hours of standing, superior to traditional alcohol-based coatings. Its brushing / flowing properties are excellent: the coating has good leveling properties, is evenly applied, and does not drip. The carbon skeleton formed by the silicone-modified phenolic resin at high temperatures synergistically prevents molten metal penetration, resulting in a smooth casting surface. The hydrofluoroether solvent evaporates rapidly, leaving minimal residue. The binder's high-temperature pyrolysis gas generation is lower than that of traditional alcohol-based coatings, reducing porosity defects in castings. The hydrofluoroether solvent used has a zero ozone depletion potential (ODP), a low global warming potential (GWP), and is free of harmful substances such as benzene and toluene.

[0032] The high evaporation rate of the casting coating provided in this application is mainly due to the intrinsic high volatility of the main solvent, hydrofluoroether (HFE). Taking the HFE solvent recommended in the patent (such as HFE-7100, i.e., methyl nonafluorobutyl ether) as an example, its physical parameters directly confirm this characteristic of "high volatility." Its boiling point is approximately 61°C, which is far lower than the 100°C of water-based systems in conventional casting coatings, and also lower than some traditional organic solvents with medium boiling points. The saturated vapor pressure can reach 26.9 kPa at 20°C. High vapor pressure means that solvent molecules are more likely to escape into the air at room temperature, which is the direct driving force for the high evaporation rate. Furthermore, it has no flash point, which is the physical basis for the "non-flammable" characteristic of this invention, and also enables it to completely eliminate safety risks while maintaining a high evaporation rate.

[0033] Based on the same inventive concept, embodiments of this application provide a method for preparing casting coatings, such as... Figure 2 As shown, Figure 2 This is a schematic flowchart illustrating the preparation method of the casting coating provided in this application. It includes the following steps: S1: Mix the suspending agent with water and stir at 60~80℃ for 30~60 minutes to activate it, and obtain the activated suspending agent slurry; S2: Mix the main solvent and the co-solvent, and stir at 300~500 rpm for 5~10 minutes; S3: Add the adhesive to the mixed solvent from step S2 and stir to dissolve; S4: Dry mix the refractory aggregate, thickener and suspending agent evenly; S5: Add the activated suspension slurry to the binder solution and disperse it evenly; then add the premixed powder, surfactant and defoamer, and disperse at high speed of 1500~2500rpm for 45~60 minutes; S6: Adjust the Baume degree to 60~85°Bé using a mixed solvent to obtain the casting coating; The process may then include step S7: sealing and packaging the casting coating after filtering it to remove impurities.

[0034] The present invention will be further described in detail below through specific embodiments. Example

[0035] This embodiment provides a casting coating, the components of which are shown in Table 1 by weight: Table 1: Refractory aggregates Zircon powder (325 mesh) 120 copies adhesive Organosilicon modified phenolic resin 15 copies suspending agent Polyvinyl butyral 1 copy Thickener Sodium carboxymethyl cellulose 2 copies Suspension Organic modified bentonite 5 copies Defoamer Polyether defoamers 0.5 copies surfactants Fluorocarbon surfactant FC-4430 1 copy main solvent Methyl nonafluorobutyl ether (boiling point 61℃, no flash point) 35 copies Cosolvent trans-1-chloro-3,3,3-trifluoropropene (boiling point 19°C, no flash point) 25 copies The main solvent, methyl nonafluorobutyl ether, is a hydrofluoroether compound with a boiling point below 80°C and no flash point; the co-solvent, trans-1-chloro-3,3,3-trifluoropropene, is a non-flammable fluorinated olefin compound with a boiling point below 30°C.

[0036] The method for preparing casting coating provided in this embodiment includes the following steps: 1) Activation treatment of suspension agent: Mix organic modified bentonite with 1 part water (the weight ratio of suspension agent to water is 1:0.2), stir and activate at 70°C for 45 minutes to obtain activated suspension agent slurry; 2) Solvent system preparation: Methyl nonafluorobutyl ether and trans-1-chloro-3,3,3-trifluoropropene are mixed at a weight ratio of 35:25 and stirred at 400 rpm for 8 minutes to form a mixed solvent; 3) Adhesive dissolution: Under stirring conditions, add the silicone-modified phenolic resin to the above mixed solvent and stir until completely dissolved; 4) Powder premixing: Mix zircon powder, sodium carboxymethyl cellulose, and polyvinyl butyral evenly in a dry state; 5) Coating preparation: In a high-speed disperser, first add the activated suspension slurry to the binder solution and disperse it evenly; then slowly add the premixed powder, and at the same time add the fluorocarbon surfactant FC-4430 and the polyether defoamer; disperse at a high speed of 2000 rpm for 50 minutes, and the fineness at the dispersion endpoint is 65 μm; 6) Adjust the Baumé degree: Adjust the Baumé degree of the coating to 75°Bé (Ford Cup 4, 25°C) using the mixed solvent obtained in step (2). 7) Filtering and packaging: Filter through a 100-mesh sieve and then package. Example

[0037] This embodiment provides a casting coating, the components of which are shown in Table 2 by weight: Table 2: Refractory aggregates Corundum powder (250 mesh) 130 copies adhesive Aluminum dihydrogen phosphate 12 copies suspending agent Polyvinyl butyral 1 copy Thickener Hydroxyethyl cellulose 1.5 copies Suspension Lithium-based bentonite 6 copies Defoamer silicone defoamer 0.6 copies surfactants Polyether modified polysiloxane 1.2 portions main solvent Ethyl nonafluorobutyl ether (boiling point approximately 65°C, no flash point) 40 copies Cosolvent 1,2-Dichloro-4-trifluorobenzene (boiling point approximately 25°C, no flash point) 30 copies The main solvent, ethyl nonafluorobutyl ether, is a hydrofluoroether compound with a boiling point below 80°C and no flash point; the co-solvent, 1,2-dichloro-4-trifluorobenzene, is a non-flammable fluorinated organic compound with a boiling point below 30°C.

[0038] The preparation method of the coating in this embodiment includes the following steps: (1) Activation treatment of suspension agent: Lithium-based bentonite is mixed with 1.2 parts of water (the weight ratio of suspension agent to water is 1:0.2), and stirred and activated at 70°C for 45 minutes to obtain activated suspension agent slurry; (2) Solvent system preparation: Ethyl nonafluorobutyl ether and 1,2-dichloro-4-trifluorobenzene were mixed at a weight ratio of 40:30 and stirred at 400 rpm for 8 minutes to form a mixed solvent; (3) Dissolution of binder: Under stirring conditions, aluminum dihydrogen phosphate is added to the above mixed solvent and stirred until completely dissolved; (4) Powder premixing: Mix corundum powder, hydroxyethyl cellulose and polyvinyl butyral evenly in a dry state; (5) Coating preparation: In a high-speed disperser, the activated suspension slurry is first added to the binder solution and dispersed evenly; then the premixed powder is slowly added, along with polyether modified polysiloxane and organosilicon defoamer; disperse at a high speed of 2000 rpm for 50 minutes, with a dispersion endpoint fineness of 70 μm; (6) Adjusting the Baumé degree: Adjust the Baumé degree of the coating to 75°Bé using the mixed solvent obtained in step (2) (Ford-4 cup viscometer, 25°C). (7) Filtering and packaging: Filter through a 100-mesh sieve and then package.

[0039] This application also provides a comparison between conventional alcohol-based casting coatings and water-based casting coatings: Comparative Example 1 This comparative example provides a conventional alcohol-based casting coating, the components of which are shown in Table 3 by weight: Table 3: Zircon powder (325 mesh) 120 copies Phenolic resin 12 copies Organic bentonite 4 copies Polyvinyl butyral (PVB) 1 copy ethanol 65 copies Isopropanol 20 copies After activating the organic bentonite by mixing it with water, solvents such as phenolic resin, ethanol, and isopropanol are added, followed by powders such as zircon powder and PVB. The mixture is then dispersed at high speed until uniform, and after adjusting the Baume degree, it is sieved and packaged.

[0040] Comparative Example 2 This comparative example provides a conventional water-based casting coating, the components of which are shown in Table 4 by weight: Table 4: Refractory aggregates Zircon powder (325 mesh) 120 copies adhesive silica sol 15 copies Suspension Bentonite 5 copies Thickener Sodium carboxymethyl cellulose 3 copies solvent water 70 copies After activating the bentonite with water, silica sol and sodium carboxymethyl cellulose are added, followed by zircon powder. The mixture is then dispersed at high speed until uniform, and after adjusting the Baume degree, it is sieved and packaged.

[0041] Examples 2-3 and Comparative Examples 1-2 were tested, and the test results are shown in Table 5. Table 5 Flash point (°C) No flashpoint No flashpoint 12~14 No flashpoint Surface drying time (min, 25℃) 8 10 8 45 Drying time (min, 25℃) 35 42 25 180 Suspension stability (24h settling rate / %) 4.2 5 8.5 0.25 Coating abrasion resistance (weight loss / g) 0.08 0.1 0.15 0.25 High-temperature crack resistance (1300℃) No cracks No cracks microcracks microcracks Surface quality (grade) of castings Level 1 Level 1-2 Level 2 Level 3 Gas evolution (mL / g, 1000℃) 12.5 13.2 18.6 8.5 Construction safety Non-flammable Non-flammable Highly flammable Non-flammable From the test results in Table 5, we can conclude that: Non-flammability: Examples 2-3 have no flash point and do not burn when directly exposed to open flame, making them far safer than alcohol-based coatings (flash point only 12-14℃).

[0042] Evaporation drying speed: In Example 2, the surface drying time was 8-10 minutes, and the actual drying time was 35-42 minutes, which is close to that of alcohol-based coatings (6 / 25 minutes) and much faster than that of water-based coatings (45 / 180 minutes), achieving "the efficiency of alcohol-based coatings and the safety of water-based coatings." Additionally, please refer to... Figure 3 The graph shows a comparison of the remaining coating weight percentage curves. In the XY line graph, the X-axis represents time (minutes) and the Y-axis represents the remaining coating weight percentage (%). The faster the curve decreases, the higher the evaporation rate.

[0043] Casting process performance: The suspension stability is better than that of alcohol-based coatings; the high-temperature crack resistance and casting surface quality are both better than those of alcohol-based and water-based coatings; the gas generation is lower than that of alcohol-based coatings, reducing the risk of porosity defects.

[0044] It eliminates the risk of flash fire and explosion, and can be used safely near areas with electrical equipment or open flame operations.

[0045] In summary, this invention successfully solves the technical problems of flammability in existing alcohol-based casting coatings and slow drying in water-based casting coatings by using hydrofluoroether compounds with boiling points below 80°C and no flash points as the main solvent, and compounding them with non-flammable fluorinated olefins or fluorinated ketones with boiling points below 30°C as co-solvents. This results in a casting coating that combines high volatility and non-flammability, demonstrating significant technological advancements and beneficial effects.

[0046] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A casting coating, characterized in that, include: Refractory aggregate 100-150 parts, binder 8-20 parts, main solvent 25-50 parts, co-solvent 20-40 parts, suspending agent 3-8 parts, thickener 1-3 parts, surfactant 0.5-2 parts, defoamer 0.2-1 parts; The main solvent is a hydrofluoroether compound with a boiling point below 80°C and no flash point; The co-solvent is a non-flammable fluorinated olefin or fluorinated ketone compound with a boiling point below 30°C.

2. The casting coating according to claim 1, characterized in that, The main solvent includes at least one of methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

3. The casting coating according to claim 1, characterized in that, The co-solvent includes at least one of trans-1-chloro-3,3,3-trifluoropropene, 1,2-dichloro-4-trifluorobenzene, or perfluorohexanone.

4. The casting coating according to claim 1, characterized in that, The refractory aggregate includes at least one of zircon powder, corundum powder, mullite powder, and quartz powder, and the fineness of the refractory aggregate is 200-400 mesh.

5. The casting coating according to claim 1, characterized in that, The binder includes at least one of silicone-modified phenolic resin, aluminum dihydrogen phosphate, or silica sol.

6. The casting coating according to claim 1, characterized in that, The suspending agent includes at least one of organic modified bentonite, lithium-based bentonite, or attapulgite; the thickener is sodium carboxymethyl cellulose or hydroxyethyl cellulose.

7. The casting coating according to claim 1, characterized in that, The surfactant is a fluorocarbon surfactant or a polyether-modified polysiloxane; the defoamer is a polyether defoamer or an organosilicon defoamer.

8. The casting coating according to claim 1, characterized in that, It also includes 0.5 to 2 parts of polyvinyl butyral, a suspending agent.

9. A method for preparing a casting coating as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Mix the suspending agent with water and stir at 60~80℃ for 30~60 minutes to activate it, and obtain the activated suspending agent slurry; S2: Mix the main solvent and the co-solvent, and stir at 300~500 rpm for 5~10 minutes; S3: Add the adhesive to the mixed solvent from step S2 and stir to dissolve; S4: Dry mix the refractory aggregate, thickener and suspending agent evenly; S5: Add the activated suspension slurry to the binder solution and disperse it evenly; then add the premixed powder, surfactant and defoamer, and disperse at high speed of 1500~2500rpm for 45~60 minutes; S6: Adjust the Baume degree to 60~85°Bé using a mixed solvent to obtain the casting coating.

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