Precoated sand collapsing agent, easily collapsible precoated sand and preparation method of easily collapsible precoated sand
By using a specific composition of the coated sand crumbing agent, the problem that the coated sand of aluminum alloy castings is not prone to collapse at high temperatures is solved, and the effect of significantly improving the collapse properties and reducing the residual strength of high temperatures is achieved, while maintaining the strength and curing effect.
Patent Information
- Application Number
- CN202411213687.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-05-09
AI Technical Summary
The coated sand of existing aluminum alloy castings is not easy to collapse at high temperatures, resulting in an increase in the scrap rate of sand core and castings and an increase in production costs.
A coated sand crumbing agent is used, which consists of 30% to 40% heat conduction agent, 40% to 50% oxidizing agent and 10% to 20% oxygen-generating agent, including SnS2 or CuI as heat conduction agent, NH4ClO4 as oxidizing agent, and KIO3 or KClO4 as oxygen-generating agent. The crumbing agent can quickly decompose phenolic resin at high temperatures and improve crumbing properties.
It significantly improves the crackability of the coated sand, reduces the residual strength of the high temperature, and does not adversely affect the strength and curing effect of the coated sand.
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Figure CN119951993A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of casting materials, and in particular to the technical field of coated sand preparation, and specifically to a coated sand dispersant, easily dispersible coated sand, and a method for preparing the easily dispersible coated sand. Background Art
[0002] Due to the rapid development of aviation, aerospace, automobile, shipbuilding and other fields, the demand for lightweight, beautiful color and corrosion-resistant aluminum alloy castings has increased rapidly. The pouring temperature of aluminum alloy castings is generally 650-750°C, and the binding energy of the linking bond in the phenolic resin structure is relatively high (the binding energy of the CC bond is 523.4 kJ / mol, and the binding energy of the C=C bond is 607.1 kJ / mol). It is not easy to be destroyed at this temperature, so the sand core is not easy to collapse. In order to ensure the collapsibility of the coated sand, the amount of phenolic resin added has to be reduced, sacrificing the strength of the sand core in exchange for the collapsibility of the sand core. The result of this is that the scrap rate of sand cores and castings increases, resulting in an increase in casting production costs.
[0003] Therefore, for phenolic resin coated sand for aluminum alloy with relatively high requirements, a disintegrator is usually added to improve the disintegration of the coated sand, thereby avoiding reducing the amount of phenolic resin. The commonly used disintegrators are mainly: (1) metal halides and organic halides that can decompose at the pouring temperature. The halogens produced by decomposition decompose the carbon skeleton chain of the phenolic resin. (2) alkali metal carbonates or hydroxides. The carbonate or hydroxide in these compounds undergoes a condensation reaction with the hydroxymethyl of the phenolic resin, thereby decomposing the phenolic resin. (3) phosphate esters or phosphates. When heated, these substances undergo a dehydration reaction with the phenolic resin, causing the phenolic resin to carbonize. (4) potassium permanganate or peroxide. When heated, these substances decompose to produce oxygen, causing the carbon skeleton chain of the phenolic resin to be oxidized and decomposed.
[0004] No matter which of the above disintegrating agents is used, the strength of the coated sand will be reduced to a certain extent, thereby causing the strength of the sand core to be reduced to a certain extent. Summary of the invention
[0005] Based on the above technical problems, the present invention provides a coated sand disintegrator, and uses the coated sand disintegrator to prepare easily disintegratable coated sand. Compared with conventional coated sand without a disintegrator, the easily disintegratable coated sand has significantly improved disintegrability, and its strength and curing effect are not adversely affected.
[0006] Specifically, the present invention adopts the following technical solutions to achieve the above objectives:
[0007] A coated sand dispersant is composed of the following components by mass percentage: 30% to 40% of a heat conductive agent, 40% to 50% of an oxidant, and 10% to 20% of an oxygen generator; the heat conductive agent is SnS2 or / and CuI; the oxidant is NH4ClO4; and the oxygen generator is KIO3 or / and KClO4.
[0008] The heat conductive agent in the coated sand dispersant provided by the present invention can quickly absorb the heat in the metal casting liquid, providing sufficient heat for the degradation of the phenolic resin; the oxidant has strong oxidizing properties and can quickly oxidize and decompose the phenolic resin under sufficient heat; the oxygen generator decomposes at high temperature to produce oxygen, further promoting the rapid decomposition of the phenolic resin.
[0009] The present invention also provides easily disintegratable coated sand comprising the coated sand disintegrator and phenolic resin.
[0010] In a preferred embodiment, the easily disintegrable coated sand is composed of the following components, measured in percentage by mass: silica sand, phenolic resin accounting for 1% to 3% of the mass of the silica sand, a disintegrating agent for the coated sand accounting for 10% to 15% of the mass of the phenolic resin, a curing agent accounting for 12% to 15% of the mass of the phenolic resin, and a lubricant accounting for 0.1% to 0.2% of the mass of the silica sand.
[0011] In a further preferred embodiment, the curing agent is hexamethylenetetramine.
[0012] In a further preferred embodiment, the lubricant is calcium stearate and / or magnesium stearate.
[0013] The present invention also provides a method for preparing the easily disintegrable coated sand, which comprises the step of preparing the coated sand by using the coated sand disintegrator and phenolic resin.
[0014] In a preferred embodiment, the method for preparing the easily disintegrable coated sand comprises the following steps:
[0015] S1, mixing phenolic resin and the coated sand disintegrator evenly to obtain a mixture A; heating silica sand to a temperature 50 to 60° C. higher than the melting point of the phenolic resin;
[0016] S2, mixing the mixture A and the heated silica sand evenly to obtain first coated sand;
[0017] S3, uniformly mixing the first coated sand and the aqueous solution of the curing agent to obtain the second coated sand;
[0018] S4. Evenly mix the second coated sand and lubricant to obtain the easily disintegrable coated sand.
[0019] In a further preferred embodiment, the curing agent is hexamethylenetetramine.
[0020] In a further preferred embodiment, the lubricant is calcium stearate and / or magnesium stearate.
[0021] In a further preferred embodiment, the uniform mixing in step S2 refers to stirring at a speed of 90 to 110 r / min for 20 to 30 s.
[0022] In a further preferred embodiment, the uniform mixing in step S3 refers to stirring at a speed of 90 to 110 r / min for 20 to 30 s.
[0023] In a further preferred embodiment, the mass percentage of the curing agent in the aqueous solution of the curing agent in step S3 is 30% to 40%.
[0024] In a further preferred embodiment, the uniform mixing in step S4 refers to stirring at a speed of 90 to 110 r / min for 20 to 40 s.
[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: compared with phenolic resin coated sand without disintegrator, when the coated sand disintegrator of the present invention is used to prepare easily disintegratable coated sand, the disintegrability of the phenolic resin coated sand is improved by more than 22%, and the high-temperature residual strength is reduced by more than 26%; and there is no adverse effect on the strength and curing effect of the coated sand. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a schematic diagram of the composition structure of the easily disintegratable coated sand prepared in the present invention.
[0027] In the figure: 1. silica sand; 2. resin layer; 3. disintegrator particles; 4. curing agent layer; 5. lubricant layer. DETAILED DESCRIPTION
[0028] The following content is combined with the embodiments to clearly and completely describe the technical solution of the present application so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made to the following implementation modes by those of ordinary skill in the art without creative work belongs to the protection scope of the present application.
[0029] Ordinal numbers used in this application, such as "first", "second", etc., are only used for descriptive purposes to distinguish similar objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. The phenolic resin used in this application is a phenolic resin commonly used in the field for casting, such as PF-1901, PF-1902, PF-1904, PF-1358 and other models.
[0030] The specific embodiment of the present application provides an easily disintegrated coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 1-3% of the mass of silica sand, coated sand disintegrating agent accounting for 10-15% of the mass of phenolic resin, curing agent accounting for 12-15% of the mass of phenolic resin, and lubricant accounting for 0.1-0.2% of the mass of silica sand. Among them, the coated sand disintegrating agent is composed of the following components by mass percentage: 30%-40% of heat transfer agent, 40%-50% of oxidant, and 10%-20% of oxygen generator.
[0031] In a further preferred embodiment, the curing agent is hexamethylenetetramine.
[0032] In a further preferred embodiment, the lubricant is calcium stearate and / or magnesium stearate.
[0033] In a further preferred embodiment, the thermal conductive agent is SnS2 and / or CuI.
[0034] In a further preferred embodiment, the oxidant is NH4ClO4.
[0035] In a further preferred embodiment, the oxygen generator is KIO3 and / or KClO4.
[0036] The specific embodiment of the present application also provides a method for preparing the above-mentioned easily disintegratable coated sand, comprising the following steps:
[0037] S1, mixing the phenolic resin and the coated sand disintegrator evenly to obtain a mixture A; adding silica sand into a grinding wheel type sand mixer, and heating it to a temperature 50 to 60° C. higher than the melting point of the phenolic resin;
[0038] S2. Put the mixture A into a roller sand mixer, control the rotation speed to 90-110 r / min, and stir for 20-30 s, so that the mixture A is melted by the heat of the silica sand during the stirring process and is evenly coated on the surface of the silica sand particles to obtain the first coated sand in which the disintegrating agent is evenly dispersed in the resin layer.
[0039] S3. Add an aqueous solution of a curing agent into a roller-type sand mixer (there is no limit on the concentration of the aqueous solution of the curing agent. Generally, the curing agent is prepared into an aqueous solution with a mass percentage of 30 to 40% before use), control the rotation speed to 90 to 110 r / min, and stir for 20 to 30 s to fully evaporate the water in the aqueous solution of the curing agent; and obtain a second coated sand.
[0040] S4, add lubricant to the wheel-type sand mixer, control the rotation speed to 90-110r / min, and stir for 20-40s to obtain the easily disintegrated coated sand. Figure 1As shown, the structure of the easily disintegrable coated sand from the inside to the outside is composed of silica sand 1, resin layer 2, curing agent layer 4 and lubricant layer 5, and the resin layer 2 contains disintegrating agent particles 3.
[0041] In a further preferred embodiment, the curing agent is hexamethylenetetramine.
[0042] In a further preferred embodiment, the lubricant is calcium stearate and / or magnesium stearate.
[0043] Example 1
[0044] A disintegrating coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 2% of the mass of silica sand, a coating sand disintegrating agent accounting for 13% of the mass of phenolic resin, a curing agent accounting for 13% of the mass of phenolic resin, and a lubricant accounting for 0.15% of the mass of silica sand. The coating sand disintegrating agent is composed of the following components by mass percentage: 38% SnS2, 45% NH4ClO4, and 17% KIO3; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate.
[0045] The method for preparing the easily disintegratable coated sand comprises the following steps:
[0046] S1. Fully mix the phenolic resin and the coated sand disintegrator to obtain a mixture A; add silica sand into a grinding wheel sand mixer and heat it to a temperature 60° C. higher than the melting point of the phenolic resin (for example, if the melting point of the phenolic resin used is 90° C., heat the silica sand to 150° C.);
[0047] S2. Put the mixture A into a roller sand mixer, control the rotation speed to 100r / min, and stir for 25s, so that the mixture A is melted by the heat of the silica sand during the stirring process and is evenly coated on the surface of the silica sand particles to obtain the first coated sand in which the disintegrating agent is evenly dispersed in the resin layer.
[0048] S3. Add an aqueous solution of a curing agent (the curing agent is prepared into an aqueous solution with a mass percentage of 35% before use) into a roller sand mixer, control the rotation speed to 110 r / min, and stir for 20 s to fully evaporate the water in the aqueous solution of the curing agent; and obtain a second coated sand.
[0049] S4, add lubricant to the wheel-type sand mixer, control the rotation speed to 100r / min, and stir for 30s to obtain the easily disintegrated coated sand. Figure 1 As shown, the structure of the easily disintegrable coated sand from the inside to the outside is composed of silica sand 1, resin layer 2, curing agent layer 4 and lubricant layer 5, and the resin layer 2 contains disintegrating agent particles 3.
[0050] Example 2
[0051] A disintegrating coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 1% of the mass of silica sand, a coating sand disintegrating agent accounting for 10% of the mass of the phenolic resin, a curing agent accounting for 12% of the mass of the phenolic resin, and a lubricant accounting for 0.1% of the mass of silica sand. The coating sand disintegrating agent is composed of the following components by mass percentage: 40% CuI, 40% NH4ClO4, and 20% KClO4; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate.
[0052] The method for preparing the easily disintegratable coated sand comprises the following steps:
[0053] S1. Fully mix the phenolic resin and the coated sand disintegrator to obtain a mixture A; add silica sand into a grinding wheel sand mixer and heat it to a temperature 50° C. higher than the melting point of the phenolic resin (for example, if the melting point of the phenolic resin used is 90° C., heat the silica sand to 140° C.);
[0054] S2. Put the mixture A into a roller sand mixer, control the rotation speed to 90r / min, and stir for 30s, so that the mixture A is melted by the heat of the silica sand during the stirring process and is evenly coated on the surface of the silica sand particles to obtain the first coated sand in which the disintegrating agent is evenly dispersed in the resin layer.
[0055] S3. Add an aqueous solution of a curing agent (the curing agent is prepared into an aqueous solution with a mass percentage of 30% before use) into a roller sand mixer, control the rotation speed to 100 r / min, and stir for 25 s to fully evaporate the water in the aqueous solution of the curing agent; and obtain a second coated sand.
[0056] S4, add lubricant to the wheel-type sand mixer, control the rotation speed to 90r / min, and stir for 40s to obtain the easily disintegrated coated sand. Figure 1 As shown, the structure of the easily disintegrable coated sand from the inside to the outside is composed of silica sand 1, resin layer 2, curing agent layer 4 and lubricant layer 5, and the resin layer 2 contains disintegrating agent particles 3.
[0057] Example 3
[0058] A disintegrating coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 3% of the mass of silica sand, a coating sand disintegrating agent accounting for 15% of the mass of phenolic resin, a curing agent accounting for 15% of the mass of phenolic resin, and a lubricant accounting for 0.2% of the mass of silica sand. The coating sand disintegrating agent is composed of the following components by mass percentage: 15% SnS2 and 15% CuI, 50% NH4ClO4, 10% KIO3 and 10% KClO4; the curing agent is urotropine; and the lubricant is calcium stearate.
[0059] The method for preparing the easily disintegratable coated sand comprises the following steps:
[0060] S1. Fully mix the phenolic resin and the coated sand disintegrator to obtain a mixture A; add silica sand into a grinding wheel sand mixer and heat it to a temperature 55°C higher than the melting point of the phenolic resin (for example, if the melting point of the phenolic resin used is 105°C, heat the silica sand to 160°C);
[0061] S2. Put the mixture A into a roller sand mixer, control the rotation speed to 110r / min, and stir for 20s, so that the mixture A is melted by the heat of the silica sand during the stirring process and is evenly coated on the surface of the silica sand particles to obtain the first coated sand in which the disintegrating agent is evenly dispersed in the resin layer.
[0062] S3. Add an aqueous solution of a curing agent (the curing agent is prepared into an aqueous solution with a mass percentage of 40% before use) into a roller sand mixer, control the rotation speed to 90 r / min, and stir for 30 s to fully evaporate the water in the aqueous solution of the curing agent; and obtain a second coated sand.
[0063] S4, add lubricant to the wheel-type sand mixer, control the rotation speed to 110r / min, and stir for 20s to obtain the easily disintegrable coated sand. Figure 1 As shown, the structure of the easily disintegrable coated sand from the inside to the outside is composed of silica sand 1, resin layer 2, curing agent layer 4 and lubricant layer 5, and the resin layer 2 contains disintegrating agent particles 3.
[0064] Example 4
[0065] A disintegrating coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 2% of the mass of silica sand, a coating sand disintegrating agent accounting for 14% of the mass of phenolic resin, a curing agent accounting for 14% of the mass of phenolic resin, and a lubricant accounting for 0.14% of the mass of silica sand. The coating sand disintegrating agent is composed of the following components by mass percentage: 40% SnS2, 50% NH4ClO4, and 10% KIO3; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate.
[0066] The preparation method of the easily disintegrable coated sand is basically the same as that in Example 1, except that the amount of each raw material used is different.
[0067] Comparative Example 1
[0068] A disintegrable coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 2% of the mass of silica sand, a disintegrating agent for coated sand accounting for 13% of the mass of phenolic resin, a curing agent accounting for 13% of the mass of phenolic resin, and a lubricant accounting for 0.15% of the mass of silica sand. The disintegrating agent is anhydrous copper sulfate, the curing agent is hexamethylenetetramine, and the lubricant is calcium stearate.
[0069] The preparation method of the easily disintegrable coated sand is the same as that of Example 1, except that the composition of the disintegrating agent is different.
[0070] Comparative Example 2
[0071] A disintegrable coated sand, which is composed of the following components by mass percentage: silica sand, phenolic resin accounting for 2% of the mass of silica sand, a coated sand disintegrating agent accounting for 13% of the mass of the phenolic resin, a curing agent accounting for 13% of the mass of the phenolic resin, and a lubricant accounting for 0.15% of the mass of silica sand. The disintegrating agent is a mixture of manganese dioxide and potassium chlorate in a mass ratio of 0.2:1, the curing agent is hexamethylenetetramine, and the lubricant is calcium stearate.
[0072] The preparation method of the easily disintegrable coated sand is the same as that of Example 1, except that the composition of the disintegrating agent is different.
[0073] Coated sand performance test
[0074] Taking conventional coated sand (the only difference between the composition of conventional coated sand and the easily disintegratable coated sand in Example 1 is that it does not contain coated sand disintegrating agent) as a comparison, the room temperature flexural strength of the coated sand was tested according to the method in JB / T 8583-2008 "Coated Sand for Casting".
[0075] The collapsibility of coated sand was tested according to the following method:
[0076] Prepare tensile standard test blocks of the coated sand of Example 1 and conventional coated sand according to the provisions of JB / T 8583-2008; cool the standard test blocks to room temperature and weigh them, with a mass of M0; place the standard test blocks in an environment at 700°C for 120 seconds, and the resin film on the surface of the sand particles that has been baked at high temperature will be destroyed and scattered; after baking, cool the standard test blocks to room temperature, collect the scattered sand particles, weigh them, and the mass is M1. Collapsibility of coated sand The units of M1 and M0 are the same. The larger it is, the better the disintegration of the coated sand.
[0077] The high temperature residual strength of coated sand is tested according to the following method:
[0078] A batch of 12 standard tensile test blocks were prepared from the coated sand of Example 1 and conventional coated sand respectively according to the provisions of JB / T 8583-2008. The standard tensile test blocks were cooled to room temperature, 6 of which were tested for room temperature tensile strength, and the average value P0 was calculated; the other 6 standard tensile test blocks were placed in an environment with a temperature of 700°C and maintained for 60 seconds. At this temperature and time, the resin film on the surface of the sand grains of conventional coated sand will not be completely destroyed and scattered; since the coated sand of Example 1 contains a disintegrating agent, the resin film will be quickly destroyed. After the above standard test blocks are cooled to room temperature, the tensile strength is tested and the average value P1 is calculated; the calculation formula for the high temperature residual strength P is: P = P1 / P0×100%, and the units of P1 and P0 are the same. The larger the P, the higher the high temperature residual strength and the less ideal the disintegrating property.
[0079] The cured thickness of the coated sand was tested according to the following method: the mold of the standard tensile test block specified in JB / T 8583-2008 was heated to a preset temperature of 232±5°C, and the coated sand of Example 1 and the conventional coated sand were poured into the mold respectively. After 90 seconds, the uncured loose sand was quickly cleaned with a brush, and the middle position of the tensile test block was sawed with a small saw blade. The thickness at the center of the test block was measured with a vernier caliper as the cured thickness. The smaller the cured thickness, the more the chemical reaction between the resin and the curing agent is hindered. When the coated sand is used to make the core, it is necessary to extend the curing time or increase the mold temperature, which leads to energy waste and low production efficiency.
[0080] The performance test results of coated sand are shown in Table 1.
[0081] Table 1 Test results of coated sand performance
[0082] Performance Indicators Example 1 Conventional coated sand Comparative Example 1 Comparative Example 2 Room temperature flexural strength (MPa) 8.5 8.4 6.5 5.6 Collapse (%) 62.6 40.3 56.2 54.7 High temperature residual strength (%) 32 58 42 48 90s curing thickness (mm) 4.3 4.2 3.7 3.2
[0083] As can be seen from Table 1, the easily disintegrated coated sand prepared by using the coated sand disintegrator of the present invention significantly improves the disintegrability and reduces the high temperature residual strength compared with the conventional coated sand, and the coated sand disintegrator will not have an adverse effect on the strength and curing effect of the coated sand. The main reason is that the disintegrator is dispersed in the resin layer and will not hinder the cross-linking reaction of the resin and the curing agent, so it will not reduce the strength. In addition, during pouring, the solidification of the molten metal will release heat, and the metal elements of the heat conductive agent can quickly transfer the heat to the inside of the sand core. The disintegrator quickly takes effect and promotes the decomposition of the phenolic resin, thereby improving the disintegrability. In addition, because the molten metal can quickly dissipate heat, it is beneficial to the solidification speed. The surface of the casting will quickly solidify into a dense equiaxed crystal shell layer. This layer of organization can prevent the O2 decomposed by the oxygen generator and the CO2, NO and other gases decomposed by the phenolic resin from invading the molten metal, causing the casting to produce pores and be scrapped; this layer of dense equiaxed crystals can also significantly improve the strength of the casting.
[0084] The above-described embodiments are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. For any person skilled in the art, the present application may have various changes and modifications. Any simple equivalent changes and modifications made based on the scope of protection of the present application and the contents of the specification should be included in the scope of protection of the present application.
Claims
1. A coated sand disintegrator, characterized in that: The invention is composed of the following components in percentage by mass: 30% to 40% of a heat transfer agent, 40% to 50% of an oxidant, and 10% to 20% of an oxygen generator; the heat transfer agent is SnS2 or / and CuI; the oxidant is NH4ClO4; and the oxygen generator is KIO3 or / and KClO4.
2. An easily disintegratable coated sand, characterized in that: It comprises the coated sand dispersant as described in claim 1 and phenolic resin.
3. The easily disintegratable coated sand according to claim 2, characterized in that: In terms of mass percentage, the easily disintegrable coated sand is composed of the following components: silica sand, phenolic resin accounting for 1% to 3% of the mass of the silica sand, a disintegrating agent for the coated sand accounting for 10% to 15% of the mass of the phenolic resin, a curing agent accounting for 12% to 15% of the mass of the phenolic resin, and a lubricant accounting for 0.1% to 0.2% of the mass of the silica sand.
4. The easily disintegrable coated sand according to claim 3, characterized in that: The curing agent is hexamethylenetetramine.
5. The easily disintegratable coated sand according to claim 3, characterized in that: The lubricant is calcium stearate and / or magnesium stearate.
6. The method for preparing easily disintegrable coated sand according to any one of claims 2 to 5, characterized in that: The method comprises the steps of preparing coated sand by using the coated sand dispersant and the phenolic resin.
7. The method for preparing easily disintegrable coated sand according to claim 6, characterized in that: The following steps are involved: S1, mixing phenolic resin and the coated sand disintegrator evenly to obtain a mixture A; heating silica sand to a temperature 50 to 60° C. higher than the melting point of the phenolic resin; S2, mixing the mixture A and the heated silica sand evenly to obtain first coated sand; S3, uniformly mixing the first coated sand and the aqueous solution of the curing agent to obtain the second coated sand; S4. Evenly mix the second coated sand and lubricant to obtain the easily disintegrable coated sand.
8. The preparation method according to claim 7, characterized in that: The curing agent is hexamethylenetetramine.
9. The preparation method according to claim 7, characterized in that: The lubricant is calcium stearate and / or magnesium stearate.
10. The preparation method according to claim 7, characterized in that: The uniform mixing in step S2 refers to stirring at a speed of 90 to 110 r / min for 20 to 30 s; or / and the uniform mixing in step S3 refers to stirring at a speed of 90 to 110 r / min for 20 to 30 s; or / and the uniform mixing in step S4 refers to stirring at a speed of 90 to 110 r / min for 20 to 40 s.