Anti-shelling precoated sand prepared from reclaimed sand and preparation method of anti-shelling precoated sand
By surface modification and sand mixing of recycled sand, the bonding force of resin is enhanced by ammonium fluorotitanate and silane-butadiene hybrid polymer, and the performance of coated sand is improved by combining nano alumina powder and calcium stearate. This solves the problem of poor bonding ability caused by clay and water glass layer on the surface of recycled sand, and realizes the preparation of anti-peeling coated sand.
Patent Information
- Application Number
- CN202610146422.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-02
- Publication Date
- 2026-05-12
AI Technical Summary
The residual clay and water glass layer on the surface of recycled sand results in poor bonding with resin, uneven coating, and easy core peeling.
Ammonium fluorotitanate was used as a surface remodeling agent to modify the recycled sand, etching out micro-textures and depositing Ti-OH roots. A silane-butadiene hybrid polymer was used as a hybrid coupling agent to enhance the resin bonding ability, and nano alumina powder and calcium stearate were added to improve the performance of the coated sand.
It improves the interfacial bonding force and coating uniformity between recycled sand and resin, reduces the tendency of coated sand to peel off, enhances tensile strength, high temperature resistance and hardening rate, and prevents sand core peeling.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This application relates to the technical field of coated sand production, and in particular to an anti-peeling coated sand prepared from recycled sand and its preparation method. Background Technology
[0002] In the foundry industry, coated sand is widely used in the preparation of sand cores and molds due to its advantages such as high strength, good fluidity, and excellent collapsibility. The core principle of coated sand preparation is to uniformly coat the surface of sand particles with a binding system such as resin and curing agent, forming coated sand particles with specific properties. The quality of these properties directly depends on the bonding strength between the sand particles and the resin, as well as the uniformity of the coating.
[0003] Natural quartz sand was once the traditional raw material for preparing coated sand. However, with the increasing depletion of natural sand resources and the increasingly stringent environmental protection policies, the recycling of foundry waste sand has become an inevitable trend in the industry. Recycled sand has gradually become a research hotspot in order to replace natural sand in the preparation of coated sand.
[0004] In actual production, when using recycled sand directly to prepare coated sand, a common technical challenge is the poor bonding performance between the sand particles and the resin. The reason for this is that the surface of the recycled sand contains some accumulated clay oolitic layer or inerted water glass layer that cannot be completely removed, resulting in poor bonding ability with the resin. During coating, the coating adheres unevenly to the surface of the sand particles, and peeling is prone to occur when making sand cores, causing production losses.
[0005] Therefore, how to effectively improve the surface properties of recycled sand, enhance its interfacial bonding with resin and the uniformity of coating, and thus avoid the occurrence of core delamination, is a technical bottleneck that urgently needs to be solved in the preparation of coated sand using recycled sand. Summary of the Invention
[0006] In order to effectively improve the surface properties of recycled sand, enhance its interfacial bonding force with resin and the uniformity of coating, and thus avoid the occurrence of core peeling, this application provides a peel-resistant coated sand prepared from recycled sand and its preparation method.
[0007] In a first aspect, this application provides an anti-peeling coated sand prepared from recycled sand, employing the following technical solution:
[0008] A type of anti-peeling coated sand prepared from recycled sand comprises the following raw materials in parts by weight: 100 parts modified recycled sand, 15-25 parts phenolic resin, 1-2 parts nano alumina powder, 7-9 parts hexamethylenetetramine aqueous solution, and 1-2 parts calcium stearate; wherein the modified recycled sand is prepared by synergistic modification of recycled sand with a surface reconstruction agent and a hybrid coupling agent, and the mass ratio of the recycled sand, the surface reconstruction agent, and the hybrid coupling agent is 100:(3-7):(0.6-0.8).
[0009] By adopting the above technical solutions, since the surface of recycled sand usually has residual clay and water glass layers, which easily leads to poor coating effect, this application modifies the recycled sand by using ammonium fluorotitanate as a surface reconstruction agent. The hydrolysis products of ammonium fluorotitanate are used to etch micro-textures on the surface of the sand particles, increasing the surface energy of the recycled sand particles. Simultaneously, Ti-OH groups are deposited on the surface of the sand particles, transforming the less-than-clean surface of the recycled sand into a highly active surface, making it easier to combine with organic matter. Furthermore, a silane-butadiene hybrid polymer is used as a hybrid coupling agent to modify the recycled sand. One end of the silane-butadiene hybrid polymer molecule combines with the Si-OH and Ti-OH on the surface of the sand particles, and the other end combines with the organic groups of the resin, greatly enhancing the bonding ability between the resin and the surface of the recycled sand particles and reducing the tendency of the coated sand to peel off.
[0010] This application incorporates nano-alumina powder. Firstly, the extremely high melting point of the alumina powder helps the resin resist the burning effect of high-temperature molten metal (>1500℃), preventing sand from adhering to the mold. Secondly, the extremely high strength of the alumina powder particles helps the mold resist micro-cracks caused by thermal stress during casting. Calcium stearate, as a lubricant, improves the fluidity of the coated sand. Urotropine aqueous solution, as a curing agent, can be uniformly dispersed in the sand-resin mixture, promoting cross-linking of the phenolic resin at high temperatures for rapid curing. During the sand mixing stage, the phenolic resin can uniformly coat the surface of the modified recycled sand and cross-link and cure at high temperatures, giving the coated sand sufficient strength and stability after being made into a sand core.
[0011] Optionally, the modified recycled sand is prepared by the following steps: pre-treating the recycled sand to make it neutral or weakly acidic; then heating it, spraying a surface reconstruction agent during stirring, and simultaneously introducing 100°C steam for reaction; after the reaction is completed, drying it, and then spraying a hybrid coupling agent to mix it evenly to obtain the modified recycled sand.
[0012] By employing the above technical solution, after pretreatment of the surface of recycled sand, saturated water vapor at 100°C is introduced simultaneously with the addition of a surface reconstruction agent. On the one hand, the high-temperature water vapor provides a high-humidity environment, which is conducive to the controlled hydrolysis of the surface reconstruction agent. The hydrolysis products undergo a condensation reaction with the Si-OH groups on the sand surface to form Ti-O-Si bonds, improving the surface density and heat resistance of the recycled sand, enhancing surface energy, strengthening compatibility with subsequent hybrid coupling agents, and inhibiting sintering of the recycled sand at high temperatures. On the other hand, the high-temperature water vapor can penetrate the microporous structure of the recycled sand surface, allowing the surface reconstruction agent to be more evenly distributed on the surface and in the microcracks of the recycled sand, achieving nanoscale surface functionalization modification. At the same time, the 100°C high temperature of the water vapor helps to evaporate the internal moisture of the recycled sand, reducing the burden of subsequent drying. After drying, the hybrid coupling agent is sprayed in, which helps to promote the tight adsorption of the coupling agent molecules, ensuring that it is evenly coated on the surface of the recycled sand. The resulting modified recycled sand has better strength, thereby improving the anti-delamination performance of the coated sand.
[0013] Optionally, the pretreatment process includes: stirring 4wt%-6wt% citric acid aqueous solution with regenerated sand at a mass ratio of (2-4):100 for 8-12 minutes.
[0014] By employing the above technical solution, the surface of regenerated sand is usually covered with residual metal oxides or alkali metal salts, which interfere with the subsequent surface modification effect. Pretreatment with a weakly acidic citric acid aqueous solution utilizes its weak organic acid properties and excellent complexing ability. On the one hand, it can dissolve the metal oxides on the surface of the regenerated sand, neutralize alkaline residues, and adjust the pH value of the regenerated sand surface to neutral or weakly acidic, creating a suitable environment for subsequent surface modification and preventing the hydrolysis of hybrid coupling agents in an alkaline environment or the precipitation or decomposition of surface reconstruction agents. On the other hand, pretreatment with citric acid aqueous solution helps clean the surface of the regenerated sand, exposing SiO2 active sites and improving the adhesion efficiency of subsequent surface reconstruction agents.
[0015] Optionally, the drying temperature is 115-125℃.
[0016] By adopting the above technical solution, drying at a temperature of 115-125℃ can remove temporary reactants and ethanol, thus avoiding interference with subsequent processes.
[0017] Optionally, the surface reconstruction agent includes an ammonium fluorotitanate ethanol solution or an ammonium fluorozirconate ethanol solution, and the hybrid coupling agent includes a silane-butadiene hybrid polymer.
[0018] Optionally, the concentration of the ammonium fluorotitanate ethanol solution or the ammonium fluorozirconate ethanol solution is 4wt%-6wt%.
[0019] Optionally, the silane-butadiene hybrid polymer is prepared by the following steps:
[0020] 95-105 parts of triethoxysilane and 290-310 parts of anhydrous toluene were placed in a reactor and purged with nitrogen. 0.05-0.15 parts of catalyst were added dropwise with stirring, the temperature was raised to 48-52°C and held for 8-12 minutes. Then 28-32 parts of liquefied butadiene were added dropwise while maintaining the temperature at 50-60°C. After the addition was complete, the temperature was raised to 70°C and held for 2-4 hours. The mixture was then distilled under reduced pressure to obtain the silane-butadiene hybrid polymer.
[0021] By adopting the above technical solution, nitrogen replacement is first performed in the preparation of silane-butadiene hybrid polymer to remove air and moisture. Then, the catalyst is added and kept at a certain temperature for a certain period of time to activate the catalyst. Liquid butadiene is then slowly added dropwise to avoid local high concentrations that may cause self-polymerization. Finally, unreacted butadiene and solvent are removed by vacuum distillation to obtain a pure grafted product. The reaction principle is that the grafting is achieved through the hydrosilylation reaction between the silane-hydrogen bonds in triethoxysilane and the carbon-carbon double bonds in butadiene. When the silane-butadiene hybrid polymer is applied to the surface of regenerated sand, it can have a better bonding effect with the surface of regenerated sand. At the same time, it can also improve the bonding ability between the modified regenerated sand and phenolic resin, improve the uniformity of coating, and reduce the peeling of coated sand.
[0022] Optionally, the catalyst is a chloroplatinic acid solution.
[0023] Optionally, the concentration of the hexamethylenetetramine aqueous solution is 14wt%-16wt%.
[0024] Secondly, this application provides a method for preparing anti-peeling coated sand using recycled sand, employing the following technical solution:
[0025] A method for preparing anti-peeling coated sand using recycled sand includes the following steps:
[0026] The modified recycled sand is heated to 145-155℃ and mixed. Phenolic resin is added and stirred for 25-35 seconds. Then, nano alumina powder is added and mixed for 15-25 seconds. Next, hexamethylenetetramine aqueous solution is added and mixed for 35-45 seconds. Finally, calcium stearate is added and mixed for 25-35 seconds to obtain coated sand.
[0027] By modifying recycled sand and then mixing it with other sands, the surface properties of the recycled sand are effectively improved, the interfacial bonding force with the resin and the uniformity of the coating are enhanced, thereby avoiding the occurrence of core delamination and obtaining anti-delamination coated sand with good tensile strength, high temperature resistance and hardening rate.
[0028] In summary, this application has the following beneficial effects:
[0029] 1. Since recycled sand typically retains clay and water glass layers on its surface, resulting in poor coating effects, this application modifies the recycled sand using ammonium fluorotitanate as a surface remodeling agent. The hydrolysis products of ammonium fluorotitanate are used to etch micro-textures onto the sand grain surface, increasing the surface energy of the sand grains. Simultaneously, Ti-OH groups are deposited on the sand grain surface, transforming the less-than-clean surface of the recycled sand into a highly active surface, making it easier to bind with organic matter. Furthermore, a silane-butadiene hybrid polymer is used as a hybrid coupling agent to modify the recycled sand. One end of the silane-butadiene hybrid polymer molecule binds to the Si-OH and Ti-OH groups on the sand grain surface, while the other end binds to the organic groups of the resin, greatly enhancing the binding ability between the resin and the sand grain surface and reducing the tendency for the coated sand to peel off.
[0030] 2. The addition of nano-alumina powder in this application serves two purposes. Firstly, the alumina powder with its extremely high melting point helps the resin resist the burning of molten metal and prevents it from invading the sand mold and causing sand adhesion. Secondly, the alumina powder particles with extremely high strength help the sand mold resist micro-cracks caused by thermal stress during the casting process.
[0031] 3. By modifying the recycled sand and then mixing it with other sand, the surface properties of the recycled sand are effectively improved, the interfacial bonding force with the resin and the uniformity of the coating are enhanced, thereby avoiding the occurrence of core delamination and obtaining anti-delamination coated sand with good tensile strength, high temperature resistance and hardening rate. Detailed Implementation
[0032] Experimental methods in the following embodiments of this application that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.
[0033] Example 1
[0034] A type of anti-peeling coated sand prepared from recycled sand comprises the following raw materials by weight:
[0035] The mixture consists of 100 kg of modified recycled sand, 15 kg of phenolic resin, 2 kg of nano-alumina powder, 7 kg of hexamethylenetetramine aqueous solution, and 1 kg of calcium stearate. The concentration of the hexamethylenetetramine aqueous solution is 15 wt%. The average particle size of the nano-alumina is 10-20 nm.
[0036] The modified recycled sand is prepared through the following steps:
[0037] 100 kg of unmodified regenerated sand was placed in a mixer and stirred. 3 kg of 5 wt% citric acid aqueous solution was added for pretreatment for 10 min to adjust the regenerated sand to a weakly acidic state (pH 5-7). Then, the regenerated sand was heated to 100°C and sprayed with 3 kg of 5 wt% ammonium fluorotitanate ethanol solution as a surface reconstruction agent. The mixture was stirred and reacted for 30 min. After the reaction was completed, the sand was heated to 120°C and dried. After drying, 0.8 kg of silane-butadiene hybrid polymer was sprayed in as a hybrid coupling agent and mixed evenly to obtain modified regenerated sand.
[0038] The preparation method of the silane-butadiene hybrid polymer is as follows:
[0039] A1. Add 100 kg of triethoxysilane and 300 kg of anhydrous toluene to a dry reaction vessel, and purge with nitrogen three times to remove air and moisture.
[0040] A2. Add 0.1 kg of chloroplatinic acid solution dropwise as a catalyst while stirring, heat to 50°C and keep warm for 10 min to activate the catalyst;
[0041] A3. Slowly add 30 kg of liquefied butadiene, maintaining the temperature at 55°C to avoid excessive local concentration that could trigger self-polymerization;
[0042] A4. After the addition is complete, raise the temperature to 70℃ and keep it warm for 3 hours;
[0043] A5. Remove unreacted butadiene and solvent by vacuum distillation to obtain a silane-butadiene hybrid polymer.
[0044] A method for preparing anti-peeling coated sand using recycled sand includes the following steps:
[0045] The modified recycled sand prepared above was heated to 100°C and mixed. Phenolic resin was added and stirred for 30 seconds. Then, nano alumina powder was added and mixed for 20 seconds. Next, hexamethylenetetramine aqueous solution was added and mixed for 40 seconds. Finally, calcium stearate was added and mixed for 30 seconds to obtain coated sand.
[0046] Example 2-Example 3
[0047] A type of anti-peeling coated sand prepared from recycled sand differs from Example 1 in that the proportions of raw materials are different, as shown in Table 1.
[0048] Table 1. Raw material consumption amounts for Examples 1-3 (unit: kg)
[0049]
[0050] Example 4
[0051] A type of anti-peeling coated sand prepared from recycled sand differs from Example 2 in that an equal amount of 5wt% ammonium fluorotitanate ethanol solution is used instead of 5wt% ammonium fluorozirconate ethanol solution.
[0052] Comparative Example 1
[0053] A coated sand prepared from recycled sand differs from Example 2 in that the amount of surface reconstruction agent used is 0 kg.
[0054] Comparative Example 2
[0055] A coated sand prepared from recycled sand differs from Example 2 in that the amount of surface reconstruction agent used is 9 kg.
[0056] Comparative Example 3
[0057] A coated sand prepared from recycled sand differs from Example 2 in that the amount of hybrid coupling agent used is 0.5 kg.
[0058] Comparative Example 4
[0059] A coated sand prepared from recycled sand differs from Example 2 in that the amount of hybrid coupling agent used is 1 kg.
[0060] Comparative Example 5
[0061] A coated sand prepared from recycled sand differs from Example 2 in that the amount of nano-alumina powder used is 0 kg.
[0062] Comparative Example 6
[0063] A coated sand prepared from recycled sand differs from Example 2 in that the amount of nano-alumina powder used is 3 kg.
[0064] Comparative Example 7
[0065] A coated sand prepared from recycled sand, which differs from Example 2 in that an equal amount of unmodified recycled sand is used to replace the modified recycled sand.
[0066] Comparative Example 8
[0067] A coated sand prepared from recycled sand, differing from Example 2 in that the recycled sand is not pretreated during preparation, and the modified recycled sand comprises the following steps:
[0068] 100 kg of unmodified recycled sand was placed in a mixer and stirred. The recycled sand was then heated to 100°C and sprayed with 3 kg of 5 wt% ammonium fluorotitanate ethanol solution as a surface reconstruction agent. The mixture was stirred for 30 min. After the reaction was completed, the sand was heated to 120°C and dried. After drying, 0.8 kg of silane-butadiene hybrid polymer was sprayed in as a hybrid coupling agent and mixed evenly to obtain modified recycled sand.
[0069] Comparative Example 9
[0070] A coated sand prepared from recycled sand differs from Example 2 in that, in the preparation of the modified recycled sand, an equal amount of 5wt% hydrochloric acid solution is used instead of a 5wt% citric acid aqueous solution for pretreatment. All other aspects are the same.
[0071] Performance testing experiment
[0072] The coated sands prepared in Examples 1-4 and Comparative Examples 1-7 were tested for tensile strength, high-temperature compressive stability and hardening rate, respectively.
[0073] 1. Tensile strength
[0074] The room temperature tensile strength of the coated sand is measured according to the methods specified in GB / T 2684—2021 "Test Methods for Foundry Sand and Mixtures". Higher room temperature tensile strength indicates better structural integrity and interfacial bonding performance of the coated sand.
[0075] 2. High-temperature pressure resistance
[0076] The coated sand to be tested was prepared into a cylindrical standard specimen with a diameter of Φ20 mm and a height of 30 mm. A 2 kg load was applied at 1000℃ using a high-temperature load testing instrument. The time taken from reaching the constant temperature of 1000℃ to the specimen showing obvious deformation and collapse was recorded as the high-temperature pressure resistance time. The longer the high-temperature pressure resistance time, the better the high-temperature structural stability and thermal collapse resistance of the coated sand.
[0077] 3. Hardening rate
[0078] The hardening rate was tested according to the method specified in JB-T8583-2008 "Coated Sand for Foundry". A higher hardening rate indicates better surface activity of the recycled sand, resulting in better thermal response performance and resistance to peeling of the coated sand.
[0079] The test results are shown in Table 2.
[0080] Table 2 Test results of Examples 1-4 and Comparative Examples 1-9
[0081]
[0082] Combining the test results of Examples 1-4 and Comparative Examples 1-7 with those in Table 2, it can be seen that the tensile strength, high-temperature resistance time, and hardening rate of Examples 1-4 are all superior to those of Comparative Examples 1-7. The reason for this is that this application modifies the recycled sand by using ammonium fluorotitanate as a surface reconstruction agent. The hydrolysis products of ammonium fluorotitanate are used to etch micro-textures on the surface of the sand particles, thereby increasing the surface energy of the sand particles. At the same time, Ti-OH roots can be deposited on the surface of the sand particles, transforming the less-than-clean surface of the recycled sand into a highly active surface, which is easier to combine with organic matter. In addition, a silane-butadiene hybrid polymer is used as a hybrid coupling agent to modify the recycled sand. One end of the silane-butadiene hybrid polymer molecule combines with the Si-OH and Ti-OH on the surface of the sand particles, and the other end combines with the organic groups of the resin, which greatly enhances the bonding ability between the resin and the surface of the sand particles and reduces the tendency of the coated sand to peel off.
[0083] This application incorporates nano-alumina powder. On one hand, the extremely high melting point of the alumina powder helps the resin resist the burning of molten metal, preventing sand from adhering to the mold. On the other hand, the extremely high strength of the alumina powder particles helps the mold resist micro-cracks caused by thermal stress during casting. Calcium stearate, as a lubricant, improves the fluidity of the coated sand. Urotropine aqueous solution, as a curing agent, can be uniformly dispersed in the sand-resin mixture, promoting cross-linking of the phenolic resin at high temperatures for rapid curing. During the sand mixing stage, the phenolic resin can uniformly coat the surface of the modified recycled sand and cross-link and cure at high temperatures, giving the coated sand sufficient strength and stability after being made into a sand core.
[0084] Combining Example 2 and Comparative Examples 8-9 with Table 2, it can be seen that Example 2 is superior to Comparative Examples 8-9. The reason for this may be that the surface of regenerated sand usually has residual metal oxides or alkali metal salts, which interfere with the subsequent surface modification effect. Pretreatment with a weakly acidic citric acid aqueous solution utilizes its weak organic acid properties and good complexing ability. On the one hand, it can dissolve the metal oxides on the surface of the regenerated sand, neutralize alkaline residues, and adjust the pH value of the regenerated sand surface to neutral or weakly acidic, creating a suitable environment for subsequent surface modification and avoiding the hydrolysis of hybrid coupling agents in an alkaline environment and the precipitation or decomposition of surface reconstruction agents in an alkaline environment. On the other hand, pretreatment with citric acid aqueous solution helps to clean the surface of the regenerated sand, exposing SiO2 active sites and improving the adhesion efficiency of the subsequent surface reconstruction agent. While using hydrochloric acid to pretreat regenerated sand (as in Comparative Example 9) can reduce the pH value of the regenerated sand surface, it can easily lead to excessive acidity on the surface of the regenerated sand, which is difficult to control. Furthermore, as an inorganic acid, hydrochloric acid does not have the ability to complex metal ions on the surface of the regenerated sand. At the same time, hydrochloric acid can easily damage the active structure on the surface of the regenerated sand, resulting in a poorer treatment effect on the regenerated sand.
[0085] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A type of anti-peeling coated sand prepared from recycled sand, characterized in that, The raw materials include the following parts by weight: 100 parts modified recycled sand, 15-25 parts phenolic resin, 1-2 parts nano alumina powder, 7-9 parts hexamethylenetetramine aqueous solution and 1-2 parts calcium stearate. The modified recycled sand is prepared by synergistic modification of recycled sand with surface reconstruction agent and hybrid coupling agent, and the mass ratio of recycled sand, surface reconstruction agent and hybrid coupling agent is 100:(3-7):(0.6-0.8).
2. The anti-peeling coated sand prepared from recycled sand according to claim 1, characterized in that, The modified recycled sand is prepared by the following steps: the recycled sand is pretreated to make it neutral or weakly acidic; then it is heated, a surface reconstruction agent is sprayed in during stirring, and 100°C water vapor is introduced for reaction. After the reaction is completed, it is dried, and after drying, a hybrid coupling agent is sprayed in and mixed evenly to obtain the modified recycled sand.
3. The anti-peeling coated sand prepared from recycled sand according to claim 2, characterized in that, The pretreatment process includes: mixing 4wt%-6wt% citric acid aqueous solution with regenerated sand at a mass ratio of (2-4):100 for 8-12 minutes.
4. The anti-peeling coated sand prepared from recycled sand according to claim 2, characterized in that, The drying temperature is 115-125℃.
5. The anti-peeling coated sand prepared from recycled sand according to claim 2, characterized in that, The surface reconstruction agent includes an ammonium fluorotitanate ethanol solution or an ammonium fluorozirconate ethanol solution, and the hybrid coupling agent includes a silane-butadiene hybrid polymer.
6. The anti-peeling coated sand prepared from recycled sand according to claim 5, characterized in that, The concentration of the ammonium fluorotitanate ethanol solution or the ammonium fluorozirconate ethanol solution is 4wt%-6wt%.
7. The anti-peeling coated sand prepared from recycled sand according to claim 5, characterized in that, The silane-butadiene hybrid polymer is prepared by the following steps: Place 95-105 parts of triethoxysilane and 290-310 parts of anhydrous toluene into a reaction vessel and purge with nitrogen; add 0.05-0.15 parts of catalyst dropwise while stirring, raise the temperature to 48-52℃ and hold for 8-12 minutes. Add 28-32 parts of liquefied butadiene dropwise, maintain the temperature at 50-60℃, and after the addition is complete, raise the temperature to 70℃ and keep it at that temperature for 2-4 hours. Then distill under reduced pressure to obtain the silane-butadiene hybrid polymer.
8. The anti-peeling coated sand prepared from recycled sand according to claim 7, characterized in that, The catalyst is a chloroplatinic acid solution.
9. The anti-peeling coated sand prepared from recycled sand according to claim 1, characterized in that, The concentration of the hexamethylenetetramine aqueous solution is 14wt%-16wt%.
10. A method for preparing anti-peeling coated sand using recycled sand as described in any one of claims 1-9, characterized in that, Includes the following steps: The modified recycled sand is heated to 145-155℃ and mixed. Phenolic resin is added and stirred for 25-35 seconds. Then, nano alumina powder is added and mixed for 15-25 seconds. Next, hexamethylenetetramine aqueous solution is added and mixed for 35-45 seconds. Finally, calcium stearate is added and mixed for 25-35 seconds to obtain coated sand.