Recyclable low-loss regenerated coated sand and preparation method thereof
Patent Information
- Application Number
- CN202611320498.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-28
- Publication Date
- 2026-11-03
AI Technical Summary
During repeated recycling, the sand particles of recycled coated sand are prone to breakage and pulverization, resulting in increased loss of effective sand. Furthermore, the interfacial bonding stability between the recycled sand and the resin coating layer is insufficient, affecting its recycling performance.
Synergistic surface modification of recycled quartz sand using silica and silane coupling agent KH550 improves its interfacial compatibility with phenolic resin. Combined with thermoplastic phenolic resin, hexamethylenetetramine, microsilica, calcium stearate and polyethylene glycol, a recyclable, low-loss recycled coated sand is prepared by thermal coating.
It improves the interfacial bonding stability of recycled coated sand, reduces sand particle breakage and pulverization loss during recycling, maintains good molding and mechanical properties, and improves recycling stability and effective sand utilization rate.
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Figure CN123024843A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of casting materials and the resource utilization technology of recycled molding sand, specifically to a recyclable, low-loss recycled coated sand and its preparation method. Background Technology
[0002] Coated sand is a type of foundry molding sand made by coating refractory particles such as quartz sand with phenolic resin, curing agents, and lubricants. It features good fluidity, high molding efficiency, good dimensional stability, and high surface quality of castings, and is widely used in the manufacture of sand molds and cores for automotive parts, machinery, hydraulic components, and other castings. With the expansion of the foundry industry, the amount of waste molding sand generated after the use of coated sand is constantly increasing. Direct disposal not only wastes quartz sand resources but also increases the burden of solid waste disposal. Therefore, regenerating waste coated sand and reusing it for coated sand production has high resource utilization value.
[0003] Currently, the regeneration of waste coated sand mainly includes mechanical regeneration, thermal regeneration, and a combination of mechanical and thermal regeneration. Thermal regeneration typically involves high-temperature treatment to thermally decompose residual resin and organic matter on the surface of the waste sand particles, followed by cooling, dust removal, and screening to obtain recycled sand. The regenerated quartz sand can then be remixed with phenolic resin, curing agents, and other auxiliary components for coating, thus achieving the recycling of waste coated sand. Compared to directly using new sand, recycled sand reduces the consumption of natural sand resources and the amount of waste sand discharged, and therefore has become an important development direction for the resource utilization of foundry sand.
[0004] However, during the recycling process of waste coated sand in casting, crushing and separation, high-temperature regeneration, and recoating, the sand particles are repeatedly subjected to mechanical and thermal effects. This easily leads to micro-cracks, pits, and other defects on the sand particle surface, accompanied by an increase in fine powder content and loss of effective sand particles. As the number of recycling cycles increases, these problems tend to accumulate further, altering the particle integrity and surface condition of the recycled sand, which is detrimental to its repeated recycling. Furthermore, changes in the surface condition of the recycled sand may also affect the wetting, spreading, and adhesion of phenolic resin on the sand particle surface, reducing the uniformity and bonding stability of the resin coating layer.
[0005] To ensure sufficient strength in recycled coated sand, existing technologies typically improve its performance by adjusting the amount of phenolic resin added, optimizing the curing system, or improving the recycling process. However, increasing the amount of resin increases production costs and the organic content in the coated sand, and also increases the amount of resin residue that needs to be removed during subsequent thermal regeneration. Simply increasing the regeneration temperature or extending the processing time may further increase the degree of thermal and mechanical stress on the sand particles. Therefore, how to improve the interfacial bonding between the recycled coated sand and the resin coating layer while maintaining good molding and mechanical properties, and reducing the breakage, pulverization, and effective sand loss of sand particles during multiple cycles, remains a technical problem that needs to be solved in the recycling of recycled coated sand. Summary of the Invention
[0006] To overcome the problems of easy breakage and pulverization of sand particles, increased effective sand loss, and insufficient interfacial stability between recycled sand and resin coating layer in the aforementioned background technology, the present invention aims to provide a recyclable, low-loss regenerated coated sand and its preparation method. The present invention uses silica and silane coupling agent KH550 to synergistically modify the surface of recycled quartz sand. The silane coupling agent improves the interfacial compatibility between the inorganic surface of recycled quartz sand and phenolic resin, and silica is used for auxiliary modification of the surface of recycled quartz sand. Based on this, thermoplastic phenolic resin, hexamethylenetetramine, microsilica powder, calcium stearate, and polyethylene glycol are combined to obtain recyclable, low-loss regenerated coated sand via a thermal coating process.
[0007] This invention can improve the interfacial bonding state between recycled quartz sand and resin coating layer, reduce sand particle breakage and pulverization loss during the recycling process while maintaining good performance of coated sand, and improve the recycling stability and effective sand utilization rate of recycled coated sand.
[0008] The objective of this invention can be achieved through the following technical solutions: A recyclable, low-loss regenerated coated sand comprises the following raw materials in parts by weight: 100-160 parts of synergistically modified recycled quartz sand; 2-5 parts of thermoplastic phenolic resin; 0.2-0.8 parts of hexamethylenetetramine; 0.5-3 parts of microsilica; 0.1-0.8 parts of calcium stearate; and 0.1-0.6 parts of polyethylene glycol. The synergistically modified recycled quartz sand is prepared by synergistically surface modifying recycled quartz sand with silica and silane coupling agent KH550.
[0009] Optionally, the synergistically modified recycled quartz sand comprises the following raw materials in parts by weight: 100 parts recycled quartz sand; 0.5 to 3.0 parts silica; 0.1 to 0.8 parts silane coupling agent KH550; 5 to 15 parts ethanol; and 2 to 8 parts deionized water.
[0010] Optionally, the preparation method of synergistically modified recycled quartz sand includes the following steps: (1) Add silane coupling agent KH550 to a mixed solution of ethanol and deionized water, stir and hydrolyze to obtain KH550 hydrolysate; (2) Add silica to KH550 hydrolysate, stir and disperse to obtain silica-KH550 synergistic modification solution; (3) Add the recycled quartz sand to the mixing equipment, and under stirring conditions, spray the silica-KH550 synergistic modification liquid evenly onto the surface of the recycled quartz sand, continue stirring, and after drying and cooling, obtain the synergistically modified recycled quartz sand.
[0011] Optionally, the reaction conditions in step (1) are: the volume ratio of ethanol to deionized water is 6 to 9:1, and the mixture is stirred and hydrolyzed for 30 to 60 minutes.
[0012] Optionally, the reaction conditions for step (2) are stirring and dispersing at 20-30°C for 30-60 minutes.
[0013] Optionally, the reaction conditions in step (3) are to preheat the recycled quartz sand to 100-120°C, continue stirring for 5-10 minutes after spraying, and dry at 100-120°C for 1-2 hours.
[0014] Optionally, a method for preparing recyclable, low-loss, regenerable coated sand includes the following steps: S1, Weigh out the co-modified recycled quartz sand, heat the co-modified recycled quartz sand and add it to the sand mixing equipment, add thermoplastic phenolic resin and mix, so that the thermoplastic phenolic resin melts and coats the surface of the co-modified recycled quartz sand to obtain the initial coated sand. S2, add hexamethylenetetramine, microsilica powder and polyethylene glycol to the initial coated sand, and continue mixing to obtain composite coated sand; S3. Add calcium stearate to the composite coated sand, continue mixing, and after cooling, crushing and sieving, obtain recyclable low-loss regenerated coated sand.
[0015] Optionally, the reaction conditions for step S1 are as follows: heating the synergistically modified recycled quartz sand to 140-160°C and then adding thermoplastic phenolic resin for mixing and coating.
[0016] Optionally, the reaction conditions for step S2 are as follows: when the temperature of the initial coating sand drops to 110-120°C, hexamethylenetetramine, silica powder, and polyethylene glycol are added and mixed.
[0017] Optionally, the reaction conditions in step S3 are as follows: calcium stearate is added and mixed when the temperature of the composite coated sand drops to 70-80°C.
[0018] The beneficial effects of this invention are: This invention employs silica and silane coupling agent KH550 to synergistically modify the surface of recycled quartz sand. Silica can assist in modifying the rough surface and microscopic defects formed on the recycled quartz sand after repeated casting and regeneration. Silane coupling agent KH550, through the silanol groups formed by its hydrolysis, creates an interfacial interaction with the hydroxyl groups on the surface of the recycled quartz sand and silica. Furthermore, its organic functional groups improve the interfacial compatibility between the inorganic sand particle surface and the thermoplastic phenolic resin. This allows the surface modification effect of silica and the interfacial coupling effect of KH550 to complement each other, improving the uniformity of wetting and spreading of phenolic resin on the surface of recycled quartz sand and the bonding stability of the coating layer. This reduces breakage and pulverization caused by weak local bonding of the coating layer and surface defects of sand particles during recycling, thereby reducing effective sand loss during repeated regeneration of the coated sand and improving the integrity, performance retention, and recycling rate of sand particles after multiple cycles. Attached Figure Description
[0019] The invention will now be further described with reference to the accompanying drawings.
[0020] Figure 1 This is a comparison chart of the results of room temperature tensile strength test and hot tensile strength test for samples with different formulations. Detailed Implementation
[0021] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.
[0022] Example 1: The purpose of this example is to provide a recyclable, low-loss regenerated coated sand under the conditions of adding each major component and process conditions at the lower limit of the claims, so as to verify the feasibility of the technical solution of the present invention under lower raw material consumption and lower processing conditions and the application effect of synergistic modified recycled quartz sand in coated sand.
[0023] S1. Preparation of synergistically modified recycled quartz sand: Weigh 0.1 parts of silane coupling agent KH550, 5 parts of ethanol, and 2 parts of deionized water, wherein the volume ratio of ethanol to deionized water is controlled at 6:1. Add silane coupling agent KH550 to the mixed solution of ethanol and deionized water, stir and hydrolyze for 30 min to obtain KH550 hydrolysate; add 0.5 parts of silica to the obtained KH550 hydrolysate, stir and disperse at 20℃ for 30 min to obtain silica-KH550 synergistic modification solution; weigh 100 parts of recycled quartz sand and add it to the mixing equipment and preheat to 100℃. Under stirring conditions, uniformly spray the obtained silica-KH550 synergistic modification solution onto the surface of recycled quartz sand. After spraying, continue stirring for 5 min, and dry at 100℃ for 1 h. After cooling, obtain synergistically modified recycled quartz sand. S2. Coating treatment: Weigh 100 parts from the synergistically modified recycled quartz sand obtained in S1, heat it to 140℃ and add it to the sand mixing equipment. Add 2 parts of thermoplastic phenolic resin and mix. The thermoplastic phenolic resin melts when heated and uniformly coats the surface of the synergistically modified recycled quartz sand to obtain the initial coated sand. When the temperature of the initial coated sand drops to 110℃, add 0.2 parts of hexamethylenetetramine, 0.5 parts of microsilica powder and 0.1 parts of polyethylene glycol. Continue mixing to uniformly disperse each component in the coating layer to obtain the composite coated sand. S3. Post-processing: When the temperature of the composite coated sand obtained in S2 drops to 70℃, add 0.1 parts of calcium stearate and continue mixing to make the calcium stearate evenly dispersed in the composite coated sand. Then, cool, crush and screen to obtain recyclable low-loss regenerated coated sand.
[0024] Example 2: The purpose of this example is to provide a recyclable, low-loss regenerated coated sand with the addition amount of each main component and process conditions at the intermediate level of the claims. By using silica and silane coupling agent KH550 to perform appropriate synergistic surface modification on the regenerated quartz sand, the surface modification, interfacial bonding and coating effect of the regenerated quartz sand are achieved to reach a better balance, so as to obtain better comprehensive performance and recycling stability.
[0025] S1. Preparation of synergistically modified recycled quartz sand: Weigh 0.45 parts of silane coupling agent KH550, 10 parts of ethanol, and 5 parts of deionized water, wherein the volume ratio of ethanol to deionized water is controlled at 7.5:1. Add silane coupling agent KH550 to the mixed solution of ethanol and deionized water, stir and hydrolyze for 45 min to obtain KH550 hydrolysate; add 1.75 parts of silica to the obtained KH550 hydrolysate, stir and disperse at 25℃ for 45 min to obtain silica-KH550 synergistic modification solution; weigh 100 parts of recycled quartz sand and add it to the mixing equipment and preheat to 110℃. Under stirring conditions, uniformly spray the obtained silica-KH550 synergistic modification solution onto the surface of recycled quartz sand. After spraying, continue stirring for 7.5 min, and dry at 110℃ for 1.5 h. After cooling, obtain synergistically modified recycled quartz sand. S2. Coating treatment: Weigh 130 parts from the synergistically modified recycled quartz sand obtained in S1, heat it to 150℃ and add it to the sand mixing equipment. Add 3.5 parts of thermoplastic phenolic resin and mix. The thermoplastic phenolic resin melts when heated and uniformly coats the surface of the synergistically modified recycled quartz sand to obtain the initial coated sand. When the temperature of the initial coated sand drops to 115℃, add 0.5 parts of hexamethylenetetramine, 1.75 parts of microsilica powder and 0.35 parts of polyethylene glycol. Continue mixing to uniformly disperse each component in the coating layer to obtain the composite coated sand. S3. Post-processing: When the temperature of the composite coated sand obtained in S2 drops to 75℃, add 0.45 parts of calcium stearate and continue mixing to make the calcium stearate evenly dispersed in the composite coated sand. Then, cool, crush and screen to obtain recyclable low-loss regenerated coated sand.
[0026] Example 3: The purpose of this example is to provide a recyclable, low-loss regenerated coated sand under the conditions of the addition amount of each main component and the process conditions being at the upper limit of the claims, in order to verify the feasibility of the technical solution of the present invention under higher modifier dosage, higher functional component addition amount and higher treatment conditions, and to examine its influence on the surface modification and coating stability of the recycled quartz sand.
[0027] S1. Preparation of synergistically modified recycled quartz sand: Weigh 8 parts of silane coupling agent KH5500, 15 parts of ethanol, and 8 parts of deionized water, wherein the volume ratio of ethanol to deionized water is controlled at 9:1. Add silane coupling agent KH550 to the mixed solution of ethanol and deionized water, stir and hydrolyze for 60 min to obtain KH550 hydrolysate; add 3.0 parts of silica to the obtained KH550 hydrolysate, stir and disperse at 30℃ for 60 min to obtain silica-KH550 synergistic modification solution; weigh 100 parts of recycled quartz sand and add it to the mixing equipment and preheat to 120℃. Under stirring conditions, uniformly spray the obtained silica-KH550 synergistic modification solution onto the surface of recycled quartz sand. After spraying, continue stirring for 10 min, and dry at 120℃ for 2 h. After cooling, obtain synergistically modified recycled quartz sand. S2. Coating treatment: Weigh 160 parts from the synergistically modified recycled quartz sand obtained in S1, heat it to 160℃ and add it to the sand mixing equipment. Add 5 parts of thermoplastic phenolic resin and mix. The thermoplastic phenolic resin melts when heated and uniformly coats the surface of the synergistically modified recycled quartz sand to obtain the initial coated sand. When the temperature of the initial coated sand drops to 120℃, add 0.8 parts of hexamethylenetetramine, 3 parts of microsilica powder and 0.6 parts of polyethylene glycol. Continue mixing to uniformly disperse each component in the coating layer to obtain the composite coated sand. S3. Post-processing: When the temperature of the composite coated sand obtained in S2 drops to 80℃, add 0.8 parts of calcium stearate and continue mixing to make the calcium stearate evenly dispersed in the composite coated sand. Then, cool, crush and screen to obtain recyclable low-loss regenerated coated sand.
[0028] Comparative Example 1: The purpose of this comparative example is to investigate the effect of unmodified recycled quartz sand with synergistic surface treatment by silica and silane coupling agent KH550 on the overall performance and recyclability of coated sand. Except for using unmodified recycled quartz sand instead of synergistically modified recycled quartz sand, the raw material amounts and preparation conditions in this comparative example are the same as in Example 2.
[0029] S1. Treatment of recycled quartz sand: Weigh 100 parts of recycled quartz sand, without adding silica and silane coupling agent KH550, without performing synergistic surface modification treatment, treat the recycled quartz sand at 110℃ for 1.5h, and cool it for later use. S2. Coating treatment: Weigh 130 parts of the recycled quartz sand after S1 treatment, heat it to 150℃ and add it to the sand mixing equipment. Add 3.5 parts of thermoplastic phenolic resin and mix. The thermoplastic phenolic resin melts when heated and evenly coats the surface of the recycled quartz sand to obtain the initial coated sand. When the temperature of the initial coated sand drops to 115℃, add 0.5 parts of hexamethylenetetramine, 1.75 parts of silica powder and 0.35 parts of polyethylene glycol. Continue mixing to evenly disperse each component in the coating layer to obtain the composite coated sand. S3. Post-processing: When the temperature of the composite coated sand obtained in S2 drops to 75℃, add 0.45 parts of calcium stearate and continue mixing to uniformly disperse the calcium stearate in the composite coated sand. Then, cool, crush and screen to obtain the recycled coated sand of Comparative Example 1.
[0030] Comparative Example 2: The purpose of this comparative example is to investigate the effect of using only silane coupling agent KH550 to modify the surface of recycled quartz sand without adding silica on the overall performance and recyclability of the coated sand, in order to verify the synergistic surface modification effect of silica and silane coupling agent KH550. Except for the absence of silica in the preparation of the synergistically modified recycled quartz sand, the raw material amounts and preparation conditions in this comparative example are the same as in Example 2.
[0031] S1. Preparation of modified recycled quartz sand: Weigh 0.45 parts of silane coupling agent KH550, 10 parts of ethanol and 5 parts of deionized water, wherein the volume ratio of ethanol to deionized water is controlled at 7.5:1. Add silane coupling agent KH550 to the mixed solution of ethanol and deionized water, stir and hydrolyze for 45 min to obtain KH550 hydrolysate; Weigh 100 parts of recycled quartz sand and add it to the mixing equipment and preheat to 110℃. Under stirring conditions, spray the obtained KH550 hydrolysate evenly on the surface of recycled quartz sand. After spraying, continue stirring for 7.5 min, and dry at 110℃ for 1.5 h. After cooling, obtain KH550 modified recycled quartz sand. S2. Coating treatment: Weigh 130 parts of KH550 modified recycled quartz sand obtained in S1, heat it to 150℃ and add it to the sand mixing equipment. Add 3.5 parts of thermoplastic phenolic resin and mix. The thermoplastic phenolic resin melts when heated and evenly coats the surface of KH550 modified recycled quartz sand to obtain the initial coated sand. When the temperature of the initial coated sand drops to 115℃, add 0.5 parts of hexamethylenetetramine, 1.75 parts of microsilica powder and 0.35 parts of polyethylene glycol. Continue mixing to evenly disperse each component in the coating layer to obtain the composite coated sand. S3. Post-processing: When the temperature of the composite coated sand obtained in S2 drops to 75℃, add 0.45 parts of calcium stearate and continue mixing to uniformly disperse the calcium stearate in the composite coated sand. Then, cool, crush and screen to obtain the recycled coated sand of Comparative Example 2.
[0032] Performance testing: 1. Tensile strength test at room temperature Recycled coated sand prepared in Examples 1-3 and Comparative Examples 1-2 were used as test samples. Figure-eight shaped tensile specimens were prepared using a standard sample preparation mold. The coated sand was placed into a metal mold preheated to 230°C and cured for 120 seconds. After demolding, the specimens were cooled to room temperature. Tensile strength was tested using a molding sand strength testing machine. A tensile load was applied to the specimen at a constant loading rate until the specimen fractured. The room temperature tensile strength of the specimen was recorded, and the test results were expressed in MPa. Five specimens were tested in parallel for each group of samples, and the arithmetic mean was taken as the final test result.
[0033] 2. Hot tensile strength test Figure-eight shaped tensile test specimens were prepared from the recycled coated sand obtained in Examples 1-3 and Comparative Examples 1-2, respectively. The specimens were heated and cured at 230°C for 120 seconds. Immediately after curing, the tensile strength was tested using a molding sand strength testing machine under hot conditions. The hot tensile strength at the point of fracture was recorded, and the test results were expressed in MPa. Five specimens were tested in parallel for each group of samples, and the arithmetic mean was taken as the final test result to evaluate the bonding strength of the recycled coated sand and the stability of the coating layer under heated conditions.
[0034] 3. Recycling rate test Equal masses of the recycled coated sand prepared in Examples 1-3 and Comparative Examples 1-2 were weighed and solidified under the same conditions. The solidified coated sand was then crushed, calcined for regeneration, cooled, dusted, and sieved. Regenerated sand meeting the original effective sand particle size range was collected and weighed, and the effective sand recovery rate was determined. The recovered effective recycled sand was then re-prepared into coated sand according to the coating process of the corresponding examples or comparative examples. The above solidification, crushing, regeneration, and re-coating processes were repeated for a total of 5 cycles. The effective sand recovery rate after the 5th cycle was recorded. The test results are expressed as a percentage (%) and are used to evaluate the effective sand retention capacity of the coated sand after multiple cycles of use.
[0035] 4. Circulating fine powder rate test Regenerated sand from Examples 1-3 and Comparative Examples 1-2 after 5 cycles was collected. Equal masses of samples from each group of recycled sand were thoroughly mixed and sieved using a standard sieve under the same conditions. Particles with a diameter lower than the lower limit of the effective sand particle size range were considered fine powder. The undersized fine powder was collected and weighed, and the fine powder rate after the 5th cycle was determined. The test results are expressed as a percentage (%). Each sample group was tested in triplicate, and the arithmetic mean was taken as the final test result. This result was used to evaluate the degree of sand particle breakage and pulverization during repeated curing, crushing, and regeneration of the coated sand. A lower fine powder rate indicates better cycle integrity and low-loss performance of the coated sand.
[0036] Table 1 Performance test results of the examples and comparative examples
[0037] As shown in Table 1, the recyclable, low-loss regenerated coated sand prepared in Examples 1-3 all exhibited good room-temperature tensile strength, hot-state tensile strength, and recyclability. Specifically, the room-temperature tensile strengths of Examples 1-3 were 4.08 MPa, 4.43 MPa, and 4.22 MPa, respectively; the hot-state tensile strengths were 2.16 MPa, 2.38 MPa, and 2.27 MPa, respectively; the effective sand recovery rates in the fifth cycle reached 92.1%, 94.0%, and 92.9%, respectively; and the fine powder rates in the fifth cycle were 2.73%, 2.08%, and 2.46%, respectively. These results indicate that the regenerated coated sand prepared by this invention, while possessing high mechanical strength, can maintain a high effective sand recovery rate and a low fine powder rate even after multiple cycles, demonstrating good recyclability stability and low-loss characteristics.
[0038] Example 2 exhibits the best overall performance, with room temperature tensile strength and hot tensile strength reaching 4.43 MPa and 2.38 MPa, respectively. The effective sand recovery rate in the fifth cycle reaches 94.0%, while the fine powder rate in the fifth cycle is only 2.08%. Compared to Examples 1 and 3, Example 2 uses appropriate amounts of silica and silane coupling agent KH550, along with suitable surface treatment conditions. This facilitates the uniform dispersion of silica on the surface of the recycled quartz sand and fully utilizes the interfacial coupling effect of KH550 between the inorganic sand particles and the phenolic resin coating layer. This results in a better balance between the surface modification degree of the recycled quartz sand, the uniformity of the resin coating, and the stability of the interfacial bonding, thus demonstrating the best overall performance.
[0039] Compared with Examples 1-3, the room temperature tensile strength and hot tensile strength of Comparative Example 1 were only 3.46 MPa and 1.76 MPa, respectively. The effective sand recovery rate in the fifth cycle decreased to 86.2%, while the fine powder rate increased to 5.18%. Comparative Example 1 did not use silica and silane coupling agent KH550 to synergistically modify the surface of the recycled quartz sand. As a result, the microscopic defects on the surface of the recycled quartz sand and the interfacial compatibility between inorganic sand particles and organic resin were not effectively improved. The bonding stability between the resin coating layer and the sand particles was relatively poor. During repeated curing, crushing and regeneration, sand particles were more likely to break and pulverize, resulting in a decrease in effective sand recovery rate and an increase in fine powder rate.
[0040] Comparative Example 2 used only the silane coupling agent KH550 to modify the surface of recycled quartz sand. Its room temperature tensile strength was 3.82 MPa, hot tensile strength was 1.97 MPa, the effective sand recovery rate in the 5th cycle was 89.5%, and the fine powder rate in the 5th cycle was 3.74%. All these properties were superior to Comparative Example 1, which had no synergistic surface modification, but were still significantly lower than Examples 1-3. This indicates that KH550 can improve the interfacial compatibility and bonding performance between recycled quartz sand and thermoplastic phenolic resin to some extent, but KH550 alone is insufficient to fully improve the surface condition of the recycled quartz sand. After introducing silica, the surface modification effect of silica and the interfacial coupling effect of KH550 work together to further improve the uniformity of the resin coating layer and the stability of the interfacial bonding, and reduce the degree of sand particle breakage and pulverization during the recycling process.
[0041] In summary, the synergistic surface modification of recycled quartz sand by silica and silane coupling agent KH550 can effectively improve the surface state of recycled quartz sand and its interfacial bonding performance with thermoplastic phenolic resin. This results in recycled coated sand with both high room temperature and hot mechanical strength, and maintains a high effective sand recovery rate and a low fine powder rate after multiple cycles. The component ratio and process conditions used in Example 2 enable the components to form a good synergistic effect, resulting in the best overall performance. This demonstrates that the technical solution of the present invention can effectively reduce sand particle loss during the recycling process of recycled coated sand and improve its recycling stability.
Claims
1. A recyclable, low-loss, regenerable coated sand, characterized in that, The raw materials include the following parts by weight: 100-160 parts of synergistically modified recycled quartz sand; 2-5 parts of thermoplastic phenolic resin; 0.2-0.8 parts of hexamethylenetetramine; 0.5-3 parts of microsilica powder; 0.1-0.8 parts of calcium stearate; and 0.1-0.6 parts of polyethylene glycol. The synergistically modified recycled quartz sand is prepared by synergistically surface modifying recycled quartz sand with silica and silane coupling agent KH550.
2. The recyclable, low-loss, regenerable coated sand according to claim 1, characterized in that, The synergistically modified recycled quartz sand comprises the following raw materials in parts by weight: 100 parts recycled quartz sand; 0.5-3.0 parts silica; 0.1-0.8 parts silane coupling agent KH550; 5-15 parts ethanol; and 2-8 parts deionized water.
3. A recyclable, low-loss, regenerable coated sand according to claim 1 or 2, characterized in that, The preparation method of the synergistically modified recycled quartz sand includes the following steps: (1) Add silane coupling agent KH550 to a mixed solution of ethanol and deionized water, stir and hydrolyze to obtain KH550 hydrolysate; (2) Add silica to KH550 hydrolysate, stir and disperse to obtain silica-KH550 synergistic modification solution; (3) Add the recycled quartz sand to the mixing equipment, and under stirring conditions, spray the silica-KH550 synergistic modification liquid evenly onto the surface of the recycled quartz sand, continue stirring, and after drying and cooling, obtain the synergistically modified recycled quartz sand.
4. The recyclable, low-loss, regenerable coated sand according to claim 3, characterized in that, The reaction conditions for step (1) are: the volume ratio of ethanol to deionized water is 6 to 9:1, and the mixture is stirred and hydrolyzed for 30 to 60 minutes.
5. The recyclable, low-loss, regenerable coated sand according to claim 3, characterized in that, The reaction conditions for step (2) are stirring and dispersing at 20-30°C for 30-60 minutes.
6. The recyclable, low-loss, regenerable coated sand according to claim 3, characterized in that, The reaction conditions for step (3) are to preheat the recycled quartz sand to 100-120°C, continue stirring for 5-10 minutes after spraying, and dry it at 100-120°C for 1-2 hours.
7. A method for preparing recyclable, low-loss, regenerable coated sand, characterized in that, The preparation method includes the following steps: S1, Weigh out the co-modified recycled quartz sand, heat the co-modified recycled quartz sand and add it to the sand mixing equipment, add thermoplastic phenolic resin and mix, so that the thermoplastic phenolic resin melts and coats the surface of the co-modified recycled quartz sand to obtain the initial coated sand. S2, add hexamethylenetetramine, microsilica powder and polyethylene glycol to the initial coated sand, and continue mixing to obtain composite coated sand; S3. Add calcium stearate to the composite coated sand, continue mixing, and after cooling, crushing and sieving, obtain recyclable low-loss regenerated coated sand.
8. The method for preparing recyclable, low-loss, regenerable coated sand according to claim 7, characterized in that, The reaction conditions for step S1 are as follows: heating the synergistically modified recycled quartz sand to 140-160°C and then adding thermoplastic phenolic resin for mixing and coating.
9. The method for preparing recyclable, low-loss, regenerable coated sand according to claim 7, characterized in that, The reaction conditions for step S2 are as follows: when the temperature of the initial coating sand drops to 110-120°C, hexamethylenetetramine, microsilica powder, and polyethylene glycol are added and mixed.
10. The method for preparing recyclable, low-loss, regenerable coated sand according to claim 7, characterized in that, The reaction conditions for step S3 are as follows: calcium stearate is added and mixed when the temperature of the composite coated sand drops to 70-80°C.