Casting waste sand based compression-resistant reclaimed sand and preparation method thereof

Abstract

The invention relates to the technical field of reclaimed sand, and discloses foundry waste sand based compression-resistant reclaimed sand and a preparation method thereof.The foundry waste sand is crushed, roasted for 1-2 h at the temperature of 600-650 DEG C and ground to obtain the reclaimed sand, the reclaimed sand, sodium silicate, Portland cement, basalt fibers, a silane coupling agent KH-550, an auxiliary and epoxy nano-silica are mixed, the mixture is put into a mold, the mold is sealed, and the foundry waste sand based compression-resistant reclaimed sand is obtained. Stirring for 15-25 minutes under the condition that the temperature is 50-65 DEG C, carrying out compression molding and maintenance under the pressure of 10-15 MPa, and sintering for 50 minutes at the temperature of 230 DEG C, so as to obtain the casting waste sand based compression-resistant reclaimed sand. The foundry waste sand-based compression-resistant reclaimed sand disclosed by the invention has relatively good compression strength.

Description

Technical Field

[0001] The present invention relates to the technical field of recycled sand, and particularly to a casting waste sand-based compressive recycled sand and a preparation method thereof. Background Art

[0002] As a main component of industrial solid waste, traditional treatment methods of casting waste sand (such as landfilling or simple recycling) have problems such as low resource utilization rate and serious environmental pollution. Existing recycled sand technologies mostly use thermal methods or chemical methods for treatment, but there are deficiencies in compressive strength: conventional recycled sand relies on physical crushing or a single binder (such as resin), and the compressive strength is generally low, making it difficult to meet the high-strength requirements in the casting or construction fields. Moreover, the process is complex and costly: thermal regeneration requires high-temperature roasting above 800 °C, with high energy consumption; chemical methods require a large amount of organic binders, increasing costs and having poor heat resistance. Summary of the Invention

[0003] (I) Technical Problems to be Solved Aiming at the deficiencies of the prior art, the present invention provides a casting waste sand-based compressive recycled sand and a preparation method thereof, which have good compressive performance.

[0004] (II) Technical Solutions To achieve the above object, the present invention provides the following technical solutions: A casting waste sand-based compressive recycled sand, comprising the following weight components: 80-100 parts by weight of casting waste sand, 1-1.5 parts by weight of sodium silicate, 0.8-1.6 parts by weight of portland cement, 1-2 parts by weight of basalt fiber, 0.5-1 part by weight of silane coupling agent KH-550, 1-2 parts by weight of an auxiliary agent, and 0.5-0.6 part by weight of epoxy nano-silica.

[0005] Further, the preparation method of the auxiliary agent is as follows: S1. Add 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and N,N-dimethylethylenediamine to the N,N-dimethylformamide solvent, stir and mix, heat up to 65-75 °C for reaction, after completion, carry out vacuum distillation, washing, and drying to obtain Intermediate 1; S2. Add 4-vinylbenzoyl chloride and Intermediate 1 to 50-60 mL of N,N-dimethylformamide solvent, stir to dissolve, then add pyridine catalyst thereto, react at 85-95 °C for 4-6 h, after completion, carry out vacuum distillation, washing, to obtain Intermediate 2; S3. Add Intermediate 2 to 45-60 mL of N,N-dimethylformamide solvent, stir to disperse, then add mercaptoacetic acid and benzoin dimethyl ether photoinitiator thereto, irradiate with ultraviolet light at 365 nm at 25-40 °C, after completion, carry out centrifugal separation, washing and drying to obtain the auxiliary agent.

[0006] Further, in the step S1, the dosage ratio of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde, N,N-dimethylethylenediamine, and N,N-dimethylformamide solvent is 2.27 - 2.34 g: 0.92 - 1.1 g: 50 - 55 mL.

[0007] Further, the reaction time in the step S1 is 4 - 6 h.

[0008] Further, in the step S2, the mass ratio of 4-vinylbenzoyl chloride, intermediate 1, and pyridine catalyst is 2.65 - 3.44 g: 3.14 - 3.26 g: 0.01 - 0.013 g.

[0009] Further, in the step S3, the mass ratio of intermediate 2, mercaptoacetic acid, and benzoin dimethyl ether photoinitiator is 1.2 - 1.4 g: 2.01 - 2.13 g: 0.02 - 0.03 g.

[0010] Further, the irradiation time in the step S3 is 2 - 4 h.

[0011] Further, the preparation method of the foundry waste sand-based compressive regenerated sand is as follows: after crushing the foundry waste sand, calcine it at a temperature of 600 - 650 °C for 1 - 2 h, grind it to obtain regenerated sand, mix the regenerated sand, sodium silicate, portland cement, basalt fiber, silane coupling agent KH-550, auxiliary agent, and epoxy nano-silica, stir at a temperature of 50 - 65 °C for 15 - 25 min, press and mold it under a pressure of 10 - 15 MPa, cure it, and sinter it at 230 °C for 50 min to obtain the foundry waste sand-based compressive regenerated sand.

[0012] (III) Beneficial technical effects In the present invention, after crushing the foundry waste sand, calcine it, grind it to obtain regenerated sand, mix the regenerated sand, sodium silicate, portland cement, basalt fiber, silane coupling agent KH-550, auxiliary agent, and epoxy nano-silica, stir for 15 - 25 min, press and mold it, cure it, and sinter it to obtain the foundry waste sand-based compressive regenerated sand.

[0013] Sodium silicate and portland cement form calcium silicate gel through a hydration reaction, which synergistically acts with the mechanical strengthening effect of basalt fiber and the nano-filling effect of epoxy nano-silica to increase its compressive strength; during the stirring process, the epoxy groups of epoxy nano-silica will undergo a ring-opening reaction with the carboxyl group and tertiary amine group in the auxiliary agent, crosslinking with each other. This crosslinking network restricts the free movement of molecular chains and reduces the porosity inside the regenerated sand, increasing its mechanical properties while also reducing its water absorption. Description of the drawings

[0014] Figure 1 is the NMR spectrum of the auxiliary agent in Example 1. Detailed implementation mode

[0015] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0017] Preparation of epoxy nano-silica: Referring to the reference document "Modification of nano-silica with silane coupling agent KH-560", a certain amount of nano-silica was weighed and added to 20 mL of toluene. It was ultrasonically dispersed for 30 min at room temperature with a KQ-300E ultrasonic cleaner (300 W) to obtain a uniform suspension. Then, silane coupling agent KH-560 was added thereto and ultrasonically treated for another 3 - 4 min, and then transferred to a 100 mL four-necked flask equipped with a reflux condenser and a powerful electric stirrer and stirred and reacted at a set oil bath temperature. The reacted slurry was centrifugally separated at a speed of 12,000 r / min at room temperature with a CT15RT bench-top high-speed refrigerated centrifuge to obtain epoxy nano-silica. Example 1

[0018] S1. 2.27 g of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and 0.92 g of N,N-dimethylethylenediamine were added to 50 mL of N,N-dimethylformamide, stirred and mixed, heated to 65 °C and reacted for 4 h. After completion, it was distilled under reduced pressure, washed and dried to obtain Intermediate 1;

[0019] S2. 2.65 g of 4-vinylbenzoyl chloride and 3.14 g of Intermediate 1 were added to 50 mL of N,N-dimethylformamide solvent, stirred and dissolved. Then, 0.01 g of pyridine catalyst was added thereto and reacted at 85 °C for 4 h. After completion, it was distilled under reduced pressure, washed to obtain Intermediate 2; S3. 1.2 g of Intermediate 2 was added to 45 mL of N,N-dimethylformamide solvent, stirred and dispersed. Then, 2.01 g of mercaptoacetic acid and 0.02 g of benzoin dimethyl ether photoinitiator were added thereto. Under ultraviolet light of 365 nm at 25 °C for 2 h. After completion, it was centrifugally separated, washed and dried to obtain the additive; S4. After crushing 80 parts by weight of foundry waste sand, it is calcined at 600 °C for 1 h, ground to obtain recycled sand. Then, the recycled sand, 1 part by weight of sodium silicate, 0.8 part by weight of portland cement, 1 part by weight of basalt fiber, 0.5 part by weight of silane coupling agent KH-550, 1 part by weight of additive, and 0.5 part by weight of epoxy nano-silica are mixed, stirred at 50 °C for 15 min, pressed into shape under a pressure of 10 MPa, cured, and sintered at 230 °C for 50 min to obtain compressive recycled sand based on foundry waste sand. Example 2

[0020] S1. 2.34 g of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and 1.1 g of N,N-dimethylethylenediamine are added to 55 mL of N,N-dimethylformamide, stirred and mixed, heated to 75 °C and reacted for 6 h. After completion, it is distilled under reduced pressure, washed, and dried to obtain Intermediate 1; S2. 3.44 g of 4-vinylbenzoyl chloride and 3.26 g of Intermediate 1 are added to 60 mL of N,N-dimethylformamide solvent, stirred and dissolved. Then, 0.013 g of pyridine catalyst is added thereto, and the reaction is carried out at 95 °C for 6 h. After completion, it is distilled under reduced pressure, washed to obtain Intermediate 2; S3. 1.4 g of Intermediate 2 is added to 60 mL of N,N-dimethylformamide solvent, stirred and dispersed. Then, 2.13 g of mercaptoacetic acid and 0.03 g of benzoin dimethyl ether photoinitiator are added thereto. Under ultraviolet light of 365 nm at 40 °C, it is irradiated for 4 h. After completion, it is centrifuged, washed, and dried to obtain the additive; S4. After crushing 100 parts by weight of foundry waste sand, it is calcined at 50 °C for 2 h, ground to obtain recycled sand. Then, the recycled sand, 1.5 parts by weight of sodium silicate, 1.6 parts by weight of portland cement, 2 parts by weight of basalt fiber, 1 part by weight of silane coupling agent KH-550, 2 parts by weight of additive, and 0.6 part by weight of epoxy nano-silica are mixed, stirred at 65 °C for 25 min, pressed into shape under a pressure of 15 MPa, cured, and sintered at 230 °C for 50 min to obtain compressive recycled sand based on foundry waste sand. Example 3

[0021] S1. 2.31 g of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and 1.02 g of N,N-dimethylethylenediamine are added to 53 mL of N,N-dimethylformamide, stirred and mixed, heated to 70 °C and reacted for 5 h. After completion, it is distilled under reduced pressure, washed, and dried to obtain Intermediate 1; S2. Add 3.04 g of 4-vinylbenzoyl chloride and 3.22 g of intermediate 1 to 55 mL of N,N-dimethylformamide solvent, stir to dissolve, then continue to add 0.011 g of pyridine catalyst thereto, react at 90 °C for 5 h, after completion, carry out vacuum distillation and washing to obtain intermediate 2; S3. Add 1.3 g of intermediate 2 to 50 mL of N,N-dimethylformamide solvent, stir to disperse, then add 2.08 g of mercaptoacetic acid and 0.025 g of benzoin dimethyl ether photoinitiator thereto, irradiate with ultraviolet light at 365 nm at 30 °C for 3 h, after completion, carry out centrifugal separation, washing and drying to obtain the additive; S4. Crush 90 parts by weight of foundry waste sand, roast at 620 °C for 1.5 h, grind to obtain regenerated sand, mix the regenerated sand, 1.2 parts by weight of sodium silicate, 1.3 parts by weight of portland cement, 2 parts by weight of basalt fiber, 0.8 parts by weight of silane coupling agent KH-550, 1 part by weight of the additive, 0.55 parts by weight of epoxy nano-silica, stir at 60 °C for 20 min, press into shape under a pressure of 13 MPa, cure, and sinter at 230 °C for 50 min to obtain foundry waste sand-based compressive regenerated sand. Example 4

[0022] S1. Add 2.27 g of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and 0.92 g of N,N-dimethylethylenediamine to 50 mL of N,N-dimethylformamide, stir and mix, heat up to 65 °C and react for 4 h, after completion, carry out vacuum distillation, washing and drying to obtain intermediate 1; S2. Add 2.65 g of 4-vinylbenzoyl chloride and 3.14 g of intermediate 1 to 50 mL of N,N-dimethylformamide solvent, stir to dissolve, then continue to add 0.01 g of pyridine catalyst thereto, react at 85 °C for 4 h, after completion, carry out vacuum distillation and washing to obtain intermediate 2; S3. Add 1.4 g of intermediate 2 to 60 mL of N,N-dimethylformamide solvent, stir to disperse, then add 2.13 g of mercaptoacetic acid and 0.03 g of benzoin dimethyl ether photoinitiator thereto, irradiate with ultraviolet light at 365 nm at 40 °C for 4 h, after completion, carry out centrifugal separation, washing and drying to obtain the additive; S4. After crushing 90 parts by weight of foundry waste sand, it is calcined at 620 °C for 1.5 h, ground to obtain recycled sand. Then, the recycled sand, 1.2 parts by weight of sodium silicate, 1.3 parts by weight of portland cement, 2 parts by weight of basalt fiber, 0.8 parts by weight of silane coupling agent KH-550, 1 part by weight of additive, and 0.55 parts by weight of epoxy nano-silica are mixed, stirred at 60 °C for 20 min, pressed into shape under a pressure of 13 MPa, cured, and sintered at 230 °C for 50 min to obtain compressive recycled sand based on foundry waste sand. Example 5

[0023] S1. Add 2.34 g of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and 1.1 g of N,N-dimethylethylenediamine to 55 mL of N,N-dimethylformamide, stir and mix, heat up to 75 °C and react for 6 h. After completion, carry out vacuum distillation, washing, and drying to obtain Intermediate 1; S2. Add 3.44 g of 4-vinylbenzoyl chloride and 3.26 g of Intermediate 1 to 60 mL of N,N-dimethylformamide solvent, stir to dissolve, then add 0.013 g of pyridine catalyst thereto, react at 95 °C for 6 h. After completion, carry out vacuum distillation, washing to obtain Intermediate 2; S3. Add 1.3 g of Intermediate 2 to 50 mL of N,N-dimethylformamide solvent, stir to disperse, then add 2.08 g of mercaptoacetic acid and 0.025 g of benzoin dimethyl ether photoinitiator thereto, irradiate with ultraviolet light at 365 nm for 3 h at 30 °C. After completion, carry out centrifugal separation, washing and drying to obtain the additive; S4. After crushing 80 parts by weight of foundry waste sand, it is calcined at 600 °C for 1 h, ground to obtain recycled sand. Then, the recycled sand, 1 part by weight of sodium silicate, 0.8 parts by weight of portland cement, 1 part by weight of basalt fiber, 0.5 parts by weight of silane coupling agent KH-550, 1 part by weight of additive, and 0.5 parts by weight of epoxy nano-silica are mixed, stirred at 50 °C for 15 min, pressed into shape under a pressure of 10 MPa, cured, and sintered at 230 °C for 50 min to obtain compressive recycled sand based on foundry waste sand.

[0024] Comparative Example 1 The difference between this comparative example and Example 5 is that Intermediate 1 is used instead of the additive.

[0025] Comparative Example 2 The difference between this comparative example and Example 5 is that Intermediate 2 is used instead of the additive.

[0026] The compressive strength test is carried out in accordance with GB / T 2684-2009.

[0027] Table 1: Compressive strength test.

[0028] Item Compressive strength (MPa) Example 1 4.85 Example 2 5.13 Example 3 4.69 Example 4 4.82 Example 5 5.04 Comparative Example 1 2.3 Comparative Example 2 2.6 As can be seen from Table 1, Examples 1-5 of the foundry waste sand-based compressive recycled sand of the present invention have better compressive strength compared to Comparative Examples 1-2.

[0029] The water absorption test was carried out in accordance with GB / T 17431.2-2010.

[0030] Table 2: Water absorption test.

[0031] Item Water absorption rate (%) Example 1 2.8 Example 2 2.6 Example 3 2.7 Example 4 2.6 Example 5 2.9 Comparative Example 1 5.3 Comparative Example 2 4.5 As can be seen from Table 2, Examples 1-5 of the foundry waste sand-based compressive recycled sand of the present invention have a smaller water absorption compared to Comparative Examples 1-2.

[0032] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of additional identical elements in the process, method, article or device including the said element.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0034] Those skilled in the art should understand that the above are only several specific embodiments of the present invention, rather than all embodiments. It should be pointed out that many variations and improvements can be made for those of ordinary skill in the art, and all variations or improvements that do not exceed the scope of the claims should be regarded as the protection scope of the present invention.

Claims

1. A casting waste sand-based compressive recycled sand, characterized in that, It comprises the following weight components: 80 - 100 parts by weight of foundry waste sand, 1 - 1.5 parts by weight of sodium silicate, 0.8 - 1.6 parts by weight of portland cement, 1 - 2 parts by weight of basalt fiber, 0.5 - 1 part by weight of silane coupling agent KH-550, 1 - 2 parts by weight of an auxiliary agent, and 0.5 - 0.6 part by weight of epoxy nano-silica.

2. The casting waste sand-based compressive recycled sand according to claim 1, characterized in that, The preparation method of the auxiliary agent is as follows: S1. Add 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde and N,N-dimethylethylenediamine into N,N-dimethylformamide solvent, stir and mix, heat up to 65 - 75 °C for reaction. After completion, carry out vacuum distillation, washing, and drying to obtain Intermediate 1; S2. Add 4-vinylbenzoyl chloride and Intermediate 1 into 50 - 60 mL of N,N-dimethylformamide solvent, stir to dissolve, then continue to add pyridine catalyst thereto, and react at 85 - 95 °C for 4 - 6 h. After completion, carry out vacuum distillation and washing to obtain Intermediate 2; S3. Add Intermediate 2 into 45 - 60 mL of N,N-dimethylformamide solvent, stir to disperse, then add mercaptoacetic acid and benzoin dimethyl ether photoinitiator thereto, irradiate with ultraviolet light of 365 nm at 25 - 40 °C. After completion, carry out centrifugal separation, washing, and drying to obtain the auxiliary agent.

3. The casting waste sand-based compressive recycled sand according to claim 2, characterized in that, In S1, the dosage ratio of 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde, N,N-dimethylethylenediamine, and N,N-dimethylformamide solvent is 2.27 - 2.34 g : 0.92 - 1.1 g : 50 - 55 mL.

4. The casting waste sand-based compressive recycled sand according to claim 2, characterized in that, The reaction time in S1 is 4 - 6 h.

5. The casting waste sand-based compressive recycled sand according to claim 2, characterized in that, In S2, the mass ratio of 4-vinylbenzoyl chloride, Intermediate 1, and pyridine catalyst is 2.65 - 3.44 g : 3.14 - 3.26 g : 0.01 - 0.013 g.

6. The casting waste sand-based compressive recycled sand according to claim 2, characterized in that, In S3, the mass ratio of Intermediate 2, mercaptoacetic acid, and benzoin dimethyl ether photoinitiator is 1.2 - 1.4 g : 2.01 - 2.13 g : 0.02 - 0.03 g.

7. The casting waste sand-based compressive recycled sand according to claim 2, characterized in that, The irradiation time in S3 is 2 - 4 h.

8. A preparation method of the casting waste sand-based compressive recycled sand according to any one of claims 1-7, characterized in that, The preparation method of the foundry waste sand-based compressive recycled sand is as follows: After crushing the foundry waste sand, calcine it at 600 - 650 °C for 1 - 2 h, grind it to obtain recycled sand. Mix the recycled sand, sodium silicate, portland cement, basalt fiber, silane coupling agent KH-550, auxiliary agent, and epoxy nano-silica, stir at 50 - 65 °C for 15 - 25 min, press and mold it under a pressure of 10 - 15 MPa, cure it, and sinter it at 230 °C for 50 min to obtain the foundry waste sand-based compressive recycled sand.

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