Molding sand adhesive, molding sand and preparation method

Abstract

The present invention provides a molding sand adhesive, molding sand and a preparation method. The preparation method of the molding sand adhesive comprises the following steps: subjecting bentonite mineral powder to cation exchange modification treatment to obtain modified bentonite; and uniformly mixing the modified bentonite and auxiliary materials to obtain the molding sand adhesive. The molding sand adhesive is prepared by the preparation method described above. The preparation method of the molding sand utilizes the molding sand adhesive described above to prepare molding sand. The molding sand is prepared by the molding sand preparation method described above. The present invention increases the bonding performance by adding auxiliary clay, reduces the deficiency of casting sand bonding by adding a release agent, realizes the reusability of the molding sand by the main body of the binder being layered minerals, realizes resource utilization, and reduces environmental pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive preparation, and in particular relates to a molding sand adhesive, molding sand and a preparation method. Background Art

[0002] The raw materials of foundry sand are composed of quartz sand, additives, binders, etc., and the performance mainly depends on the material system of the binder and additives. When using organic binders, the environmental pollution is large and the production cost is high. Inorganic compound binders have disadvantages such as low specific strength and poor moisture resistance. Clay binders are usually bentonite, which has the advantages of good disintegration, low cost and reusability, and is favored by the majority of foundry industries. Bentonite has good bonding properties, is easy to demould and has relatively stable performance under high temperature conditions. It is commonly used as a binder in clay wet sand.

[0003] Traditional casting green sand often needs to be added with coal powder, which is to prevent sand from sticking to the casting surface, inhibit expansion defects and reduce pores, which can effectively reduce the surface roughness of cast iron parts and improve the quality of castings. However, green sand has problems such as polluting the environment and difficulty in meeting the requirements of high compaction rate wet mold molding process in production, so it is urgent to develop new coal powder substitute materials.

[0004] In foundry production, castings produced by sand casting account for 90% of the total casting production, and clay sand casting accounts for about 85% of sand casting. According to statistics, 1 to 1.2 tons of waste sand are generated for every ton of castings produced, so the recycling of old clay sand is a major problem that needs to be solved in the foundry industry. Summary of the invention

[0005] The object of the present invention is to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the objects of the present invention is to provide a method for preparing a molding sand adhesive. Another object of the present invention is to provide a molding sand adhesive. Another object of the present invention is to provide a method for preparing molding sand. Yet another object of the present invention is to provide molding sand.

[0006] In order to achieve the above object, one aspect of the present invention provides a method for preparing a molding sand adhesive, the preparation method comprising the following steps: subjecting bentonite powder to a cation exchange modification treatment to obtain a modified bentonite; and uniformly mixing the modified bentonite and auxiliary materials to obtain a molding sand adhesive. The auxiliary materials include auxiliary clay and a release agent, and the cation exchange modification treatment uses an alkali metal ion modifier.

[0007] In an exemplary embodiment of the present invention, the mass ratio of the modified bentonite to the auxiliary material may be 7.5-8.5:1.5-3; the mass ratio of the alkali metal ion modifier to the bentonite mineral powder may be 1-2.5:100; and the mass percentage concentration of the alkali metal ion modifier may be 0.3-1.0%.

[0008] In an exemplary embodiment of the present invention, the bentonite mineral powder may include calcium montmorillonite, quartz, illite and calcite; the alkali metal ion modifier may include one or more of sodium hydroxide, sodium carbonate, lithium hydroxide, lithium carbonate, sodium phosphate and sodium silicate aqueous solution; the release agent may include one or more of phlogopite powder, sericite powder, talc powder and graphite powder; the auxiliary clay may include one or more of illite clay, sepiolite clay, palygorskite clay, coal gangue and kaolin.

[0009] In an exemplary embodiment of the present invention, the bentonite mineral powder may include the following components by mass fraction: 50% to 60% SiO2, 20% to 30% Al2O3, 10% to 15% Na2O, 1% to 5% MgO and 5% to 10% CaO; the auxiliary clay may include the following components by mass fraction: 50% to 55% SiO2, 10% to 15% K2O and 30% to 40% Al2O3.

[0010] In an exemplary embodiment of the present invention, the particle sizes of the modified bentonite, auxiliary clay and release agent may be 200-350 meshes.

[0011] Another aspect of the present invention provides a molding sand adhesive, which is prepared by any one of the preparation methods described above.

[0012] Another aspect of the present invention provides a method for preparing molding sand, wherein the method for preparing molding sand utilizes the molding sand adhesive, quartz sand and industrial water to prepare molding sand.

[0013] In an exemplary embodiment of the present invention, the preparation method may include the following steps: mixing the molding sand binder and quartz sand, adding water for homogenization, so that the molding sand binder is fully wrapped on the surface of the quartz sand to obtain a sand mold. The mass ratio of the molding sand binder to the quartz sand is 0.8 to 1.2:20.

[0014] In an exemplary embodiment of the present invention, the preparation method may further include: pressing the molding sand into a mold, wherein the green compression strength of the molded sand is 130-170 kPa.

[0015] In another aspect, the present invention provides a molding sand, which is prepared by any one of the molding sand preparation methods described above, and the molded sand mold is used for casting copper, zinc, lead, pig iron, cast iron, aluminum, and alloy steel castings.

[0016] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0017] 1) The present invention has a formula design with a completely different design concept from the traditional molding sand binder. In addition to using modified bentonite, the bonding performance is increased by adding auxiliary clay, the deficiency of casting sand bonding is reduced by adding a release agent, and the reusability of the molding sand is achieved by the main body of the binder being layered minerals, thereby realizing resource utilization and reducing environmental pollution;

[0018] 2) In the process of compounding the binder, a mold release agent with good high temperature stability and mainly composed of flaky minerals is added. The mold release agent has a similar layered structure to montmorillonite in bentonite, but has better high temperature resistance, so that it has higher demolding properties, and the prepared casting is not prone to sand adhesion;

[0019] 3) Since the present invention does not add coal powder, theoretically no harmful gases such as carbon monoxide, carbon dioxide and sulfur oxide will be released from the binder, which greatly improves the production environment and protects the health of workers;

[0020] 4) Graphite powder is used to replace coal powder with poor thermal stability and easy combustion, and it can play the role of bright carbon;

[0021] 5) The binder of the present invention adopts natural mineral raw materials, which are cheap, easy to obtain and have strong universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 shows an XRD pattern of the modified bentonite of Example 1 of the present invention;

[0023] Figure 2 shows an XRD pattern of auxiliary clay of Example 1 of the present invention;

[0024] Figure 3 The XRD pattern of the release agent powder of Example 1 of the present invention is shown;

[0025] Figure 4 A casting diagram of Application Example 1 of the present invention is shown;

[0026] Figure 5 A casting diagram of Application Example 2 of the present invention is shown;

[0027] Figure 6 A casting diagram of Application Example 3 of the present invention is shown. DETAILED DESCRIPTION

[0028] Hereinafter, a molding sand binder, molding sand and a preparation method of the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0029] First Exemplary Embodiment

[0030] In a first exemplary embodiment of the present invention, a method for preparing a molding sand binder is provided, the preparation method comprising the following steps:

[0031] S1. Performing cation exchange modification on bentonite powder to obtain modified bentonite.

[0032] Optionally, the bentonite powder may include calcium montmorillonite, quartz, illite and calcite. The bentonite powder may include the following components which may be calculated by mass fraction:

[0033] 50% to 60% SiO2, for example, 53%, 55%, 57%;

[0034] 20% to 30% Al2O3, for example, 23%, 25%, 27%, 29%;

[0035] 10% to 15% Na2O, for example, 12%, 14%;

[0036] 1% to 5% MgO, for example, 2%, 4%;

[0037] 5% to 10% CaO, for example, 6%, 7%, 9%.

[0038] Optionally, the mass ratio of alkali metal ion modifier to bentonite powder is 1 to 2.5:100. Specifically, the cation exchange modification treatment uses an alkali metal ion modifier, which may include one or more aqueous solutions of sodium hydroxide, sodium carbonate, lithium hydroxide, lithium carbonate, sodium phosphate, and sodium silicate. Here, the alkali metal ion modifier is sprayed into the bentonite powder, and the added amount is 1% to 2.5% by mass of the bentonite powder, and the mass percentage concentration of the modifier aqueous solution can be 0.3 to 1.0%. After spraying, the mixture is evenly mixed and the aging reaction is carried out.

[0039] S2. Evenly mix the modified bentonite and auxiliary materials to obtain a molding sand adhesive.

[0040] Specifically, the modified bentonite and auxiliary materials are proportioned and mixed, and then mixed evenly using a mixer to obtain a molding sand adhesive.

[0041] Among them, the auxiliary materials include auxiliary clay and release agent, and the mass ratio of modified bentonite to auxiliary materials is 7.5-8.5:1.5-3, for example, 7.8:2, 8:2, 8.3:2.9. The ratio of auxiliary clay to release agent in the auxiliary materials is 1-1.5:1-1.5, for example, 1:1, 1:1.2, 1.2:1. Here, modified bentonite is the main material. When the mass ratio of modified bentonite reaches 7.5 or more, the wet compressive strength of the molding sand can meet the standard.

[0042] Optionally, the modified bentonite, auxiliary clay and release agent are easily available. Here, the chemical composition of the raw materials such as the modified bentonite, auxiliary clay and release agent is substantially free of sulfur, volatile sulfur or low in sulfur content.

[0043] Optionally, the auxiliary clay may include one or more of illite clay, sepiolite clay, palygorskite clay, coal gangue and kaolin. The auxiliary clay may include the following components which may be calculated by mass fraction:

[0044] 50% to 55% SiO2, for example, 53%, 54%;

[0045] 10% to 15% K2O, for example, 12%, 14%;

[0046] 30% to 40% Al2O3, for example, 32%, 35%, 37%, 39%.

[0047] Optionally, the release agent may include one or more of phlogopite powder, sericite powder, talc powder and graphite powder. The release agent may include the following components which may be calculated by mass fraction:

[0048] 50% to 60% SiO2, for example, 53%, 54%;

[0049] 10% to 15% K2O, for example, 12%, 14%;

[0050] 30% to 40% Al2O3. For example, 32%, 35%, 37%, 39%.

[0051] Optionally, the mass percentage of calcium montmorillonite in the modified bentonite can be greater than 70wt%, for example, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%; the mass percentage of clay minerals in the auxiliary clay can be greater than 70wt%, for example, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%; the mass percentage of flaky minerals in the release agent or the carbon content in the graphite powder can be greater than 70wt%, for example, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%. When the mass percentage of montmorillonite in the modified bentonite, the mass percentage of clay minerals in the auxiliary clay and the mass percentage of flaky minerals in the release agent or the carbon content of the graphite powder is higher than 70%, the wet compressive strength of the pressed sample is high; when the content is lower than 70%, the wet compressive strength of the pressed sample will be lower than the value in the national standard.

[0052] Optionally, the amount of adsorbed water contained in the modified bentonite, auxiliary clay and release agent may be no more than 3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%. The modified bentonite, auxiliary clay and release agent are dried, and the parameters such as the temperature and time of the dryer are adjusted so that the amount of adsorbed water contained in the dried modified bentonite, auxiliary clay and release agent may be no more than 3%, so as to obtain a dry powder. Here, the drying temperature is 110°C to 150°C, and the drying time is 2h to 5h. For example, the temperature can be 120°C, 130°C, 140°C, and the time is 2.5h, 4h, 4.5h.

[0053] In this exemplary embodiment, in the step of homogenizing the modified bentonite and the auxiliary materials, a stirrer may be used to mix them evenly, and the stirring time may be 20 to 50 minutes. For example, the stirring time may be 25 minutes, 30 minutes, 40 minutes, or 45 minutes.

[0054] Optionally, the particle size of the modified bentonite, auxiliary clay and release agent can be 200-350 mesh, such as 250 mesh, 260 mesh, 280 mesh, 300 mesh, 325 mesh. Here, the particle size of 200-350 mesh is convenient for mixing during mixing, and this particle size range is easy to obtain in industrial experiments and is relatively cheap.

[0055] Among them, the bonding performance is increased by adding auxiliary clay, the deficiency of sand bonding of castings is reduced by adding mold release agent, and the reusability of molding sand is achieved by the main body of molding sand binder being layered minerals.

[0056] Second Exemplary Embodiment

[0057] In a second exemplary embodiment of the present invention, a molding sand adhesive is provided. The molding sand adhesive is prepared by the preparation method described above.

[0058] Third Exemplary Embodiment

[0059] In a third exemplary embodiment of the present invention, a method for preparing molding sand is provided. The method for preparing molding sand utilizes the molding sand binder, quartz sand and industrial water described above to prepare molding sand.

[0060] In this exemplary embodiment, the preparation method may include the following steps: mixing the molding sand binder and quartz sand, adding water for homogenization, so that the molding sand binder is fully wrapped on the surface of the quartz sand to obtain molding sand.

[0061] Wherein, the mass ratio of the molding sand binder to the quartz sand is 0.8-1.2:20. For example, the mass ratio may be 0.9:20, 1:20, or 1.1:20.

[0062] In this exemplary embodiment, in the step of homogenizing the molding sand binder and the quartz sand, the quartz sand is added according to the national standard. The particle size of the quartz sand can be 50-100 meshes or 70-140 meshes.

[0063] Optionally, adding water for homogenization means that the mass percentage of the mixture of industrial water, molding sand binder and quartz sand can be 5-10%, and the mixture is mixed and rolled evenly in a sand mixer. Here, in the homogenization step, a sand mixer can be used to mix and roll so that the molding sand binder is wrapped on the surface of the quartz sand, and the mixing time can be 20-50 minutes. In order to make the moisture content of the molding sand 5-10% of the mass percentage of the molding sand, industrial water can be added during the mixing process. For example, the moisture content can be 6%, 7%, 8%, 9% of the mass percentage of the molding sand.

[0064] In this exemplary embodiment, the preparation method may further include: pressing the molding sand. Optionally, the sample is subjected to a compression test, and the machine used for compression may be a hammer type compression machine. The sand mold sample from the previous step is placed in a cylindrical mold, placed on the hammer type compression machine, swung 3 to 5 times, and the mold is removed to take out the sample. Measure the height of the sample and keep it at 5.00 cm ± 0.1 cm. Among them, the sample is cylindrical, with a diameter of 5 cm and a height of 5 cm. Here, the sample comes out of the mold, and the shape will not change. It can be formed as long as it is within the humidity range.

[0065] The wet compressive strength of the molded sand after molding is 130-170 kPa, for example, 140 kPa, 150 kPa, 160 kPa. The wet compressive strength is within the range of 130-170 kPa and meets the standard. The molded sand samples meeting the standard are reserved for use in the next step of the pouring experiment.

[0066] Fourth Exemplary Embodiment

[0067] In a fourth exemplary embodiment of the present invention, a molding sand is provided. The molding sand is prepared by the molding sand preparation method described above. The molded sand mold can be used for casting copper, zinc, lead, pig iron, cast iron, aluminum, and alloy steel castings.

[0068] Optionally, the application of casting can be to cast aluminum parts with standard molding sand samples. The steps of casting can include: placing the mixed sand mold sample into a sample tank, pouring the fired aluminum liquid into the sample tank, and after the aluminum part is formed, removing the mold and placing it in a water tank to cool down, and finally taking out the aluminum part after it cools down.

[0069] Optionally, the reason why the prepared casting is not easy to be sand-bonded is that a release agent mainly composed of flaky minerals with good high-temperature stability is added during the binder compounding process. The release agent has a similar layered structure characteristic to montmorillonite in bentonite, but has better high-temperature resistance.

[0070] In order to better understand the above exemplary embodiments of the present invention, a molding sand adhesive, molding sand and a preparation method are described below with reference to specific examples.

[0071] Example 1

[0072] The preparation method of the molding sand in this example comprises the following steps:

[0073] (1) The bentonite powder is subjected to cation exchange modification treatment to obtain modified bentonite. The modified bentonite, auxiliary clay and release agent are then dried for 3 hours, and the amount of water adsorbed by the dried modified bentonite, auxiliary clay and release agent is 3%, 1% and 1% respectively. The dried sample is then added to a blender and stirred to obtain a molding sand adhesive, wherein the mass ratio of the modified bentonite, auxiliary clay and release agent is 8:1:1, the mass percentage of montmorillonite in the modified bentonite is 70%, the mass percentage of clay minerals in the auxiliary clay is 70%, the mass percentage of lamellar minerals in the release agent or the carbon content in graphite powder is 70%, the particle size of the modified bentonite is 200 mesh, the particle size of the auxiliary clay is 200 mesh, and the particle size of the release agent is 325 mesh.

[0074] (2) Add the molding sand adhesive sample obtained in step (1) to quartz sand for homogenization, put it into a sand mixer for stirring and grinding, add an appropriate amount of water so that the water content is maintained at 7% of the mass percentage of the sand mold, and obtain a sand mold. The ratio of quartz sand to molding sand adhesive is 20:0.8. Press the molding sand sample and test the wet compressive strength. The wet compressive strength of the sample is measured to be 145 kPa.

[0075] The bentonite powder includes calcium montmorillonite, quartz, illite and calcite, the alkali metal ion modifier is a sodium carbonate aqueous solution, the concentration of the alkali metal ion modifier is 0.3%, the auxiliary clay is sepiolite clay, and the release agent is talc. The mass ratio of the alkali metal ion modifier to the bentonite powder is 100:1.

[0076] Figure 1 shows an XRD pattern of the modified bentonite of Example 1 of the present invention; Figure 2 shows an XRD pattern of auxiliary clay of Example 1 of the present invention; Figure 3 The XRD pattern of the release agent of Example 1 of the present invention is shown. Figure 1 to Figure 3 As shown, the purity of the samples used can meet the above purity requirements, the mass percentage of montmorillonite in the modified bentonite is 70%, the mass percentage of clay minerals in the auxiliary clay is 70%, the mass percentage of lamellar minerals in the release agent or the carbon content in the coal graphite powder is 70%.

[0077] Application Example 1

[0078] The molding sand obtained in Example 1 was used for reverse casting. After the pouring was completed, the sample was demoulded and placed in a water tank to cool down to obtain a casting.

[0079] Figure 4 FIG. 2 shows a casting diagram of Application Example 1 of the present invention. Figure 4 As shown, the casting has high surface gloss, smooth surface and low sand adhesion.

[0080] Example 2

[0081] The preparation method of the molding sand in this example comprises the following steps:

[0082] (1) The bentonite powder is subjected to cation exchange modification treatment to obtain modified bentonite. The modified bentonite, auxiliary clay and release agent are then dried for 3 hours. The amount of adsorbed water contained in the dried modified bentonite, auxiliary clay and release agent is 2%, 1% and 1% respectively. The dried sample is then added to a blender and stirred to obtain a molding sand adhesive, wherein the mass ratio of the modified bentonite, auxiliary clay and release agent is 7.8:1.2:1, the mass percentage of montmorillonite in the modified bentonite is 70%, the mass percentage of clay minerals in the auxiliary clay is 70%, the mass percentage of lamellar minerals in the release agent or the carbon content in graphite powder is 70%, the particle size of the modified bentonite is 250 mesh, the particle size of the auxiliary clay is 200 mesh, and the particle size of the release agent is 325 mesh.

[0083] (2) Add the molding sand adhesive sample obtained in step (1) to quartz sand for homogenization, put it into a sand mixer for stirring and grinding, add an appropriate amount of water so that the water content is maintained at 7% of the mass percentage of the sand mold, and obtain a sand mold. The ratio of quartz sand to molding sand adhesive is 20:1.0. Press the sand mold sample and test the wet compressive strength. The wet compressive strength of the sample is measured to be 147 kPa.

[0084] The bentonite powder includes calcium montmorillonite, quartz, illite and calcite, the alkali metal ion modifier is a sodium silicate aqueous solution, the concentration of the alkali metal ion modifier is 0.8%, the auxiliary clay is kaolin, and the release agent is phlogopite. The mass ratio of the alkali metal ion modifier to the bentonite powder is 100:1.5.

[0085] Application Example 2

[0086] The molding sand obtained in Example 2 was used for reverse casting. After the pouring was completed, the sample was demoulded and placed in a water tank to cool down to obtain a casting.

[0087] Figure 5 FIG. 2 shows a casting diagram of Application Example 2 of the present invention. Figure 5 As shown, the casting has high surface gloss, smooth surface and low sand adhesion.

[0088] Example 3

[0089] The preparation method of the molding sand in this example comprises the following steps:

[0090] (1) The bentonite powder is subjected to cation exchange modification to obtain modified bentonite. The modified bentonite, auxiliary clay and release agent are then dried for 3 hours. The amount of adsorbed water contained in the dried bentonite, clay and release agent is 3%, 1% and 1% respectively. The dried sample is then added to a blender and stirred to obtain a molding sand adhesive, wherein the mass ratio of the modified bentonite, auxiliary clay and release agent is 7.8:1:1.2, the mass percentage of montmorillonite in the modified bentonite is 70%, the mass percentage of clay minerals in the auxiliary clay is 70%, the mass percentage of lamellar minerals in the release agent or the carbon content in graphite powder is 70%, the particle size of the modified bentonite is 325 mesh, the particle size of the auxiliary clay is 200 mesh, and the particle size of the release agent is 325 mesh.

[0091] (2) Add the molding sand adhesive sample obtained in step (1) to quartz sand for homogenization, put it into a sand mixer for stirring and grinding, add an appropriate amount of water so that the water content is maintained at 8% of the molding sand mass percentage, and obtain a sand mold. The ratio of quartz sand to molding sand adhesive is 20:1.2. Press the molding sand and test the wet compressive strength. The wet compressive strength of the sample is measured to be 157 kPa.

[0092] The bentonite powder includes calcium montmorillonite, quartz, illite and calcite, the alkali metal ion modifier is a sodium phosphate aqueous solution, the concentration of the alkali metal ion modifier is 1.0%, the auxiliary clay is illite clay, and the release agent is sericite. The mass ratio of the alkali metal ion modifier to the bentonite powder is 100:2.5.

[0093] Application Example 3

[0094] The molding sand obtained in Example 3 was used for reverse casting. After the pouring was completed, the sample was demoulded and placed in a water tank to cool down to obtain a casting.

[0095] Figure 6 FIG. 2 shows a casting diagram of Application Example 3 of the present invention. Figure 6 As shown, the casting has high surface gloss, smooth surface and low sand adhesion.

[0096] Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for preparing a molding sand adhesive, characterized in that: The preparation method comprises the following steps: The bentonite powder is subjected to cation exchange modification treatment, and an alkali metal ion modifier is sprayed into the bentonite powder. After spraying, the mixture is evenly mixed and subjected to aging reaction to obtain modified bentonite; The modified bentonite and auxiliary materials are mixed evenly to obtain a molding sand adhesive; the mass ratio of the modified bentonite to the auxiliary materials is 7.5-8.5:1.5-3; Among them, the auxiliary materials are auxiliary clay and a release agent, the auxiliary clay is one or more of illite clay, sepiolite clay, palygorskite clay, coal gangue and kaolin; the release agent is one or more of phlogopite powder, sericite powder, talcum powder and graphite powder; the mass percentage of calcium montmorillonite in the modified bentonite is greater than 70wt%, the mass percentage of clay minerals in the auxiliary clay is 70wt%, the mass percentage of flaky minerals in the release agent or the carbon content in the graphite powder is greater than 70wt%; the ratio of the auxiliary clay to the release agent in the auxiliary material is 1-1.5:1-1.5; The cation exchange modification treatment uses an alkali metal ion modifier; the alkali metal ion modifier includes one or more of sodium hydroxide, sodium carbonate, lithium hydroxide, lithium carbonate, sodium phosphate and sodium silicate aqueous solution; the mass ratio of the alkali metal ion modifier to the bentonite powder is 1 to 2.5:100; the mass percentage concentration of the alkali metal ion modifier is 0.3 to 1.0%; The bentonite powder includes calcium montmorillonite, quartz, illite and calcite; The bentonite powder includes the following components by mass fraction: 50% to 60% SiO2, 20% to 30% Al2O3, 10% to 15% Na2O, 1% to 5% MgO and 5% to 10% CaO; The auxiliary clay includes the following components by mass fraction: 50% to 55% SiO2, 10% to 15% K2O and 30% to 40% Al2O3.

2. The method for preparing the molding sand adhesive according to claim 1, characterized in that: The particle sizes of the modified bentonite, auxiliary clay and release agent are 100-350 meshes.

3. A molding sand adhesive, characterized in that: The molding sand adhesive is prepared by the preparation method according to claim 1 or 2.

4. A method for preparing molding sand, characterized in that: The method for preparing molding sand utilizes the molding sand adhesive as claimed in claim 3, quartz sand and industrial water to prepare molding sand.

5. The method for preparing molding sand according to claim 4, characterized in that: The preparation method comprises the following steps: After the molding sand binder and quartz sand are mixed, water is added for homogenization so that the molding sand binder is fully wrapped on the surface of the quartz sand to obtain molding sand; Wherein, the mass ratio of the molding sand binder to quartz sand is 0.8-1.2:

20.

6. The method for preparing molding sand according to claim 4, characterized in that: The preparation method further comprises: pressing and molding the molding sand to obtain a molded sand mold; wherein the molded sand mold has a wet compression strength of 130 to 170 kPa.

7. A molding sand, characterized in that: The molding sand is prepared by the molding sand preparation method according to any one of claims 4 to 6, and the molded sand mold is used for casting copper, zinc, lead, pig iron, cast iron, aluminum, and alloy steel castings.

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