Process for the preparation of foundry sand binders and use thereof

Abstract

The application provides a preparation method of a foundry sand mold binder and an application thereof, and the method comprises the following steps: preparing modified water glass; preparing alkaline phenolic resin; mixing the modified water glass and the alkaline phenolic resin to obtain the foundry sand mold binder; wherein the preparation of the modified water glass comprises the following steps: adding sodium water glass into a stirring kettle, then adding sodium hydroxide to adjust the modulus of the water glass, then adding a modifier solution into the reaction kettle, and uniformly stirring and reacting at a certain temperature to obtain the modified water glass. The modified water glass is introduced into the alkaline phenolic resin, the reaction completeness and the structural compactness are improved while the binding performance is retained, and the requirements of safe production and green production are met.

Description

Technical Field

[0001] This application relates to the field of casting, specifically to a method for preparing a casting sand mold binder and its application. Background Technology

[0002] Among the organic binder family, basic phenolic resins are widely used due to their relatively low environmental impact and odor. However, even so, in practical applications, basic phenolic resins still release a certain amount of harmful gases, posing a potential threat to the safety of the working environment and human health.

[0003] Meanwhile, inorganic binders, due to their inherent properties based on inorganic materials, release almost no harmful gases during use, making them a more environmentally friendly option. However, significant differences in chemical and physical properties between inorganic and organic binders make effective miscibility or mixing difficult, thus limiting the possibility of integrating the advantages of inorganic materials into basic phenolic resins. Specifically, experiments attempting to modify basic phenolic resins with inorganic materials revealed particularly prominent compatibility issues between inorganic binders and basic phenolic resins, severely hindering performance optimization and application expansion after their combination. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of the prior art and to provide a casting sand mold binder that can effectively integrate the advantages of inorganic binders and its preparation method.

[0005] The specific proposal of this application is as follows: 1. A method for preparing a casting sand mold binder, wherein the method comprises: preparing modified water glass; preparing alkaline phenolic resin; mixing the modified water glass and the alkaline phenolic resin to obtain the casting sand mold binder; The preparation of modified water glass includes: adding sodium water glass into a stirred tank, then adding sodium hydroxide to adjust the modulus of the water glass, then adding a modifier solution into a reaction vessel, stirring evenly, and reacting at a constant temperature to obtain modified water glass.

[0006] 2. The method according to item 1, wherein the modifier is selected from epoxy silane modifier or amino silane modifier, and the modifier accounts for 0.1%-1.0% of the mass fraction of the sodium silicate.

[0007] 3. According to the method described in item 1, wherein, The temperature of the isothermal reaction is 70℃-120℃, preferably 85-95℃; The isothermal reaction time is 5-12 hours, preferably 8-10 hours.

[0008] 4. The method according to item 1, wherein the modulus of the water glass is 1.8-2.3.

[0009] 5. The method according to item 1, wherein the preparation of alkaline phenolic resin comprises mixing phenol and KOH solution in a reaction vessel at a certain mass ratio, and then adding formaldehyde solution to obtain the alkaline phenolic resin.

[0010] 6. According to the method described in item 5, wherein the mass ratio of phenol, formaldehyde, and KOH solution is 1:(0.4-1.2):(1.7-2.4).

[0011] 7. The method according to item 1, wherein, in the mixture, the modified water glass accounts for 10%-20% of the mass fraction of the alkaline phenolic resin.

[0012] 8. The method according to item 1, wherein a modifier is added during the mixing process of modified water glass and alkaline phenolic resin, said modifier being a silane modifier.

[0013] 9. A casting sand mold binder, prepared according to any one of claims 1-8.

[0014] 10. The method according to any one of items 1-8, or the application of the casting sand mold binder according to item 9 in the casting field.

[0015] This application introduces a composite of modified water glass and alkaline phenolic resin, which retains the adhesive properties while improving reaction completeness and structural density, and simultaneously meets the requirements of safe and green production. The method provided in this application not only significantly reduces the emission of harmful gases in the final product, improving its environmental friendliness, but also maintains or even improves the mechanical strength and other key performance indicators of the modified resin to meet a wider range of application needs. By solving the problem of miscibility between inorganic and organic components, this application opens up new avenues for developing a new generation of high-performance, low-pollution adhesives. Detailed Implementation

[0016] The present application will now be described in detail. While specific embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0017] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "including but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0018] This application provides a method for preparing a casting sand mold binder, wherein the method comprises: preparing modified water glass; preparing alkaline phenolic resin; and mixing the modified water glass and the alkaline phenolic resin to obtain the casting sand mold binder; The preparation of modified water glass includes: adding sodium water glass into a stirred tank, then adding sodium hydroxide to adjust the modulus of the water glass, then adding a modifier solution into a reaction vessel, stirring evenly, and reacting at a constant temperature to obtain modified water glass.

[0019] In this application, the modulus refers to the molar ratio of SiO2 to Na2O in water glass, which determines its solubility, viscosity, alkalinity, water resistance, and applicable fields. Selecting a suitable modulus for water glass is crucial to ensuring application effectiveness, and the modulus can be determined by chemical titration.

[0020] In one embodiment of this application, the modifier is selected from epoxy silane modifiers or amino silane modifiers. Specifically, the modifier is selected from one or more of KH560, KH550, and methyltrimethoxysilane, preferably KH560. In one embodiment of this application, the modifier accounts for 0.1%-1.0% of the mass fraction of the sodium silicate, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%. For example, when the mass of the sodium silicate is 100g, the corresponding amount of modifier added should be 0.2g-1.0g. It should be understood that those skilled in the art can adjust the amount of modifier solution added to the sodium silicate by calculating the concentration (or mass) of the modifier in the modifier solution, thereby making the mass of the modifier conform to the above-mentioned relationship with the mass of the sodium silicate. For example, in some cases, the modifier may be in solution form, such as a 50% mass concentration modifier solution.

[0021] In one embodiment of this application, the temperature of the isothermal reaction is 70℃-120℃, for example, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, or 120℃, preferably 85-95℃. In another embodiment of this application, the time of the isothermal reaction is 5-12 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, preferably 8-10 hours.

[0022] In one embodiment of this application, the modifier solution is a mixture of a modifier and a liquid solvent. In another embodiment, the molar ratio of the modifier to the solvent in the modifier solution is 1:(0.7-1.6). For example, the molar ratio of the modifier (solute) to the solvent can be 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, or 1:1.6. The solvent comprises one or more of water, methanol, and ethanol. In one case, the solvent can be an aqueous solution of methanol or ethanol.

[0023] In one embodiment of this application, the modulus of the water glass is 1.8-3.0. For example, the modulus of the water glass can be 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0, preferably 1.8-2.3.

[0024] In one embodiment of this application, an inorganic acid (e.g., sulfuric acid) or an inorganic alkali (e.g., sodium hydroxide) can be used to adjust the modulus of the water glass.

[0025] In one embodiment of this application, the preparation of the alkaline phenolic resin comprises mixing phenol and KOH solution in a reaction vessel at a certain mass ratio, followed by the addition of formaldehyde solution to obtain the alkaline phenolic resin. Specifically, phenol, 30 wt% KOH solution, and 37 wt% formaldehyde solution are weighed in a mass ratio of 1:(0.4-1.2):(1.7-2.4). Phenol and KOH are first added to the reaction vessel and stirred. After stirring until homogeneous, formaldehyde is added in multiple portions, and the reaction is carried out for 2.5 hours. The temperature is then lowered to below 40°C to obtain an alkaline phenolic resin with a molecular weight of 800-1000, which is then set aside for later use.

[0026] For example, the mass ratio of phenol to KOH solution can be 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, or 1:1.2. The mass ratio of phenol to formaldehyde solution can be 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, or 1:2.4.

[0027] In one embodiment of this application, the modified water glass comprises 10%-30% of the alkaline phenolic resin by mass in the mixture. For example, the mass fraction can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%. In another embodiment of this application, the modified water glass comprises 10%-20% of the alkaline phenolic resin by mass.

[0028] In one embodiment of this application, a modifier may be added during the mixing process of the modified water glass and the alkaline phenolic resin. The modifier is a silane modifier, and more specifically, an epoxy silane modifier, specifically KH560. It should be understood that in one embodiment of this application, the addition of the modifier is an optional step. For example, in one embodiment of this application, the amount of modifier added can be 1g-10g, such as 1g, 2g, 3g, 4g, 5g, 6g, 7g, 8g, 9g, or 10g.

[0029] In one embodiment of this application, a curing agent may be added during the mixing of the modified water glass and the alkaline phenolic resin. The curing agent is selected from HQG20 or ZG-8, and its purpose is to accelerate or trigger the crosslinking reaction of the resin-water glass composite system, so that it can change from liquid to solid in a short time.

[0030] This application also provides a casting sand mold binder prepared according to any of the methods described above.

[0031] In one embodiment of this application, the formaldehyde concentration can be detected using a method consistent with GB / T 15516-1995, or as described in the examples. It should be understood that regardless of the method used, the test results should be considered identical, unique, and accurate, and should not be construed as limiting the scope of this application.

[0032] This application also provides casting sand mold binders prepared by the methods described in any of the above claims, and the application of the resins described in any of the above claims in the casting field.

[0033] In one instance of this application, "inorganic alkaline phenolic resin" and "casting sand mold binder" can be used interchangeably, meaning that in one case it is the physical name of the product, and in another case the product can be used for a certain purpose in certain fields. Therefore, such a description should not be regarded as a limitation of this application.

[0034] Example Specific embodiments of this application are described in more detail below. While specific embodiments of this application are shown herein, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of this application to those skilled in the art.

[0035] This application provides a general and / or specific description of the materials and methods used in the experiments, as shown in the examples below. Unless otherwise specified, all reagents and instruments used are commercially available conventional reagents or instruments.

[0036] This application provides a general and / or specific description of the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., weight percentage. Reagents or instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0037] Methods for observing the color of water glass: Take 20 mL of the modified water glass solution after the reaction is complete and place it in a sample tube. Place the sample tube in front of a white background and observe the color change directly by comparing it horizontally with the unmodified blank water glass solution under natural light. The color of water glass can range from colorless to light yellow to light brownish-red, with light brownish-red showing the best effect. If the water glass color is any other color (e.g., colorless and transparent, light yellow, etc.), it is considered unqualified.

[0038] Test methods for inorganic alkaline phenolic resin after casting and molding Compressive strength test method: The compressive strength is tested using a tensile testing machine (XQY-Ⅱ intelligent sand strength tester). Inorganic alkaline phenolic resin is mixed with aggregate and prepared into a figure-eight shaped sample. The prepared inorganic alkaline phenolic resin is tested according to the tensile testing machine's instruction manual.

[0039] After the inorganic basic phenolic resin was prepared, the inorganic basic phenolic resin was tested at different times.

[0040] Observation method for inorganic alkaline phenolic resin: Using conventional observation methods, we observed whether inorganic alkaline phenolic resin exhibited stratification under normal temperature and pressure conditions.

[0041] Specifically, take 100g of the modified alkaline phenolic resin solution, transfer it to a stoppered graduated container, and let it stand vertically at room temperature for 24 hours. Check whether there is a clear interface in the solution system. If a clear layering line is observed visually, or the upper layer is a transparent liquid and the lower layer contains precipitates, flocculent matter, or turbidity, it is determined that the resin solution has undergone stratification. If the solution remains uniform throughout without any interface, it is determined that there is no stratification.

[0042] Method for testing formaldehyde concentration in inorganic alkaline phenolic resin: Formaldehyde concentration is primarily tested using the acetylacetone spectrophotometric method. First, a measured amount of alkaline phenolic resin sand sample is placed in a 25°C water bath and stirred. The released gas is pumped at a fixed flow rate into two gas bubble absorption tubes, each containing 10 mL of absorption liquid. The absorption liquids are combined and diluted to volume to obtain the test solution. A blank and a test group are prepared by adding the same amount of acetylacetone solution to each, tightening the caps, shaking well, and then heating in a constant temperature water bath at 60°C for 40 min. After the reaction is complete, the mixture is cooled to room temperature. Next, the blank and test group solutions are added to 1 cm cuvettes, and the absorbance of each solution is measured sequentially at a wavelength of 412 nm. The absorbance values ​​of the sample solutions are substituted into the equation to calculate the absolute formaldehyde content in the sample tubes, and the formaldehyde concentration is then calculated using the standard formula.

[0043] On the other hand, the method for detecting formaldehyde concentration can be referred to GB / T 15516-1995. It should be understood that regardless of the method used, the test results should be considered the same, unique, and accurate.

[0044] Preparation method Step 1: Synthesis method of modified water glass: 2 kg of commercially available industrial sodium silicate was added to a stirred tank. Sodium hydroxide was then added to adjust the modulus of the silicate. A 10 wt% modifier solution was then added to the reactor. After stirring until homogeneous, the mixture was reacted at a constant temperature to obtain modified silicate.

[0045] The prepared modified water glass was subjected to color observation according to the method described above. If the color observation result failed, the subsequent synthesis and testing steps were not performed.

[0046] Step Two: Synthesis Method of Alkaline Phenolic Resin Weigh out phenol, 30% KOH solution and 37% formaldehyde solution in a mass ratio of 1:0.6:2.0. First, put phenol and KOH into the reaction vessel and stir. After stirring evenly, add formaldehyde in several batches and react for 2.5 hours. Then cool down to below 40℃ to obtain alkaline phenolic resin with a molecular weight of 800-1000 for later use.

[0047] Step 3: Synthesis method of casting sand mold binder (inorganic alkaline phenolic resin): The modified water glass from step one and the alkaline phenolic resin from step two are mixed in a certain mass ratio, and then 5g of an appropriate amount of epoxy silane regulator (KH560) is added. After mixing evenly, a casting sand mold binder (inorganic alkaline phenolic resin) is obtained.

[0048] The prepared inorganic basic phenolic resin was subjected to the performance tests described above. First, the inorganic basic phenolic resin was observed to separate into layers. If separation occurred, it indicated that the inorganic basic phenolic resin's properties were not uniform, leading to fluctuations in product quality, deterioration of processing performance, or inability to store the product for long periods, thus increasing subsequent operating costs.

[0049] Casting and Shaping Weigh 2 kg of standard sand (commercially purchased) and place it in a sand mixer. Turn on the sand mixer and add the curing agent (ZG-8) at a uniform speed, mixing thoroughly. Then, uniformly add the modified water glass prepared in step one, mixing thoroughly, and place the product into a compression mold for performance testing. The mass of the water glass is 2.5% (i.e., 50 g) of the standard sand mass, and the mass of the curing agent is 20% (i.e., 10 g) of the water glass mass.

[0050] Weigh 2 kg of standard sand (commercially purchased) and place it in a sand mixer. Turn on the sand mixer and add the curing agent (HQG20) at a uniform speed, mixing thoroughly. Then, uniformly add the inorganic alkaline phenolic resin prepared in step three, mix thoroughly, and place the product into a compression mold for performance testing. The mass of the resin is 1.4% (28 g) of the mass of the standard sand, and the mass of the curing agent is 25% (7 g) of the mass of the resin.

[0051] The performance of the obtained products was determined according to the testing methods described above.

[0052] Example 1 Example 1-1 Prepare the casting sand mold binder according to the methods in steps one to three above.

[0053] In step one, the modulus of water glass is adjusted to 2.0, the modifier solution is a 10 wt% aqueous solution of KH560, and the modifier is 0.2% of the mass of sodium water glass. The modified water glass is obtained by reacting at 90℃ for 8 hours. In step three, the modified water glass and the alkaline phenolic resin are mixed in a certain mass ratio, wherein the modified water glass accounts for 20% of the mass of the alkaline phenolic resin.

[0054] The prepared modified water glass and inorganic alkaline phenolic resin were molded, and their corresponding performance was measured after curing for 2 hours and 24 hours. The conditions of the examples are summarized in Table 1, and the performance test results are summarized in Table 2.

[0055] Examples 1-2 The procedure is the same as in Example 1-1, except that the modifier solution is adjusted to an aqueous solution of KH550.

[0056] Examples 1-3 The procedure is the same as in Example 1-1, except that the modifier solution is adjusted to an aqueous solution of methyltrimethoxysilane.

[0057] Examples 1-4 The procedure is the same as in Example 1-1, except that the solvent in the modifier solution is changed to ethanol.

[0058] Examples 1-5 The procedure is the same as in Example 1-1, except that the solvent in the modifier solution is changed to methanol.

[0059] Examples 1-6 The procedure is the same as in Example 1-1, except that the solvent in the modifier solution is adjusted to be a mixture of ethanol and water in a 1:1 mass ratio.

[0060] Examples 1-7 The procedure is the same as in Example 1-1, except that there is no modifier solution.

[0061] Examples 1-8 The procedure is the same as in Example 1-1, except that the mass fraction of the modifier in sodium silicate is adjusted to 0.1%.

[0062] Examples 1-9 The procedure is the same as in Example 1-1, except that the mass fraction of the modifier in sodium silicate is adjusted to 0.5%.

[0063] Examples 1-10 The procedure is the same as in Example 1-1, except that the mass fraction of the modifier in sodium silicate is adjusted to 1%.

[0064] Examples 1-11 The procedure is the same as in Example 1-1, except that the mass fraction of the modifier in sodium silicate is adjusted to 2%.

[0065] Examples 1-12 The procedure is the same as in Example 1-1, except that the reaction temperature is adjusted to 75°C.

[0066] Examples 1-13 The procedure is the same as in Example 1-1, except that the reaction temperature is adjusted to 85°C.

[0067] Examples 1-14 The procedure is the same as in Example 1-1, except that the reaction temperature is adjusted to 95°C.

[0068] Examples 1-15 The procedure is the same as in Example 1-1, except that the reaction temperature is adjusted to 110°C.

[0069] Examples 1-16 The procedure is the same as in Example 1-1, except that the reaction time is adjusted to 2 hours.

[0070] Examples 1-17 The procedure is the same as in Example 1-1, except that the reaction time is adjusted to 6 hours.

[0071] Examples 1-18 The procedure is the same as in Example 1-1, except that the reaction time is adjusted to 9 hours.

[0072] Examples 1-19 The operation is the same as in Example 1-1, except that the reaction time is adjusted to 10 hours.

[0073] Examples 1-20 The operation is the same as in Example 1-1, except that the modulus of the water glass is adjusted to 1.5.

[0074] Examples 1-21 The operation is the same as in Example 1-1, except that the modulus of the water glass is adjusted to 1.8.

[0075] Examples 1-22 The operation is the same as in Example 1-1, except that the modulus of the water glass is adjusted to 2.3.

[0076] Examples 1-23 The operation is the same as in Example 1-1, except that the modulus of the water glass is adjusted to 2.6.

[0077] Comparative Example 1-1 Purchase commercially available water glass with a modulus of 2.0 from Shengquan, and test its compressive strength after 2 hours and 24 hours of curing, respectively, according to the relevant standard methods in the example, and record the experimental results.

[0078] Table 1

[0079] Table 2

[0080] In Tables 1 and 2, the symbol " / " indicates that there is no performance or no data at this point.

[0081] As shown in Tables 1 and 2, the water glass in Examples 1-4, 1-12, and 1-17 all exhibited a yellowish tint. It is speculated that during the modification process of the water glass, side reactions produced trace amounts of organic oxidation products (aldehydes, ketones, or carboxylic acids), leading to the yellowing of the product. When used in the casting field, these oxidation products can catalyze further hydrolysis of the water glass, corroding the metal substrate, lowering the system pH, and affecting subsequent curing. The water glass in Examples 1-5 exhibited turbidity because methanol, as a potential chemical reaction product during the water modification process, prevented the complete chemical reaction. The self-polymerization of KH560 into nano-sized siloxane particles indicates that this system cannot form a uniform and stable product shape.

[0082] When KH560 and methyltrimethoxysilane were used as modifiers, the modified water glass showed higher strength after 2 hours and 24 hours compared to when KH550 was used. When adjusting the mass fraction of the modifier, the strength of the modified water glass was highest at 0.2% and then gradually decreased, suggesting that the optimal mass fraction is between 0.1% and 0.5%. At a reaction temperature of 75℃, the water glass was yellowish. When the reaction temperature was gradually increased to 110℃, the performance remained stable. Therefore, for cost reasons, a temperature between 85-95℃ is preferable. Similarly, the reaction time is best kept above 9 hours. When the modulus of the water glass was too low, the modified water glass had a strength of 0.6 after 2 hours, which is less than 1 and does not meet the strength standard. When the modulus was increased to 2.6, the strength of the modified water glass just met the standard after 2 hours, but relatively speaking, the strength dropped sharply to 0.8 after 24 hours.

[0083] It should be understood that when the performance of a newly developed product is significantly lower than that of existing technology, the product should be considered to have no application value. Therefore, slight fluctuations are allowed in the performance of newly developed products, and it is generally considered that the performance should not be lower than 90%. It can be seen that the water glass prepared by the method of Example 1-1 has stronger test results than the comparative example. In Examples 1-8, 1-11, and 1-20, since the tensile strength of a certain item is lower than 90% of the strength of the comparative example in the corresponding period, it is indicated that the water glass prepared under these conditions does not meet the industry standard. Therefore, it will not be used in the preparation of inorganic alkaline phenolic resin in the future.

[0084] The modified water glass prepared by the method of this application has slightly lower performance than the prior art when it has been left to stand for 2 hours, but its performance is improved compared with the prior art after standing for 24 hours.

[0085] Example 2 As can be seen from the above, when water glass is modified according to the conditions described in Example 1-1, the modified water glass prepared exhibits excellent performance.

[0086] Therefore, a method for preparing a casting sand mold binder by mixing modified water glass and alkaline phenolic resin in a certain mass ratio was further explored.

[0087] Example 2-1 The modified water glass prepared in Example 1-1 and the alkaline phenolic resin prepared in step 2 above were mixed in a certain mass ratio. Then, 5g of epoxy silane regulator (KH560) was added and mixed evenly to obtain a casting sand mold binder (inorganic alkaline phenolic resin).

[0088] Weigh 2 kg of standard sand (commercially purchased) and place it in a sand mixer. Turn on the sand mixer and add the curing agent (HQG20) at a uniform speed, mixing thoroughly. Then, uniformly add the inorganic alkaline phenolic resin prepared in step three above, mixing thoroughly, and then place the product into a compression mold for performance testing. The mass of the resin is 1.4% (i.e., 28 g) of the mass of the standard sand, and the mass of the curing agent is 25% (i.e., 7 g) of the mass of the resin.

[0089] The inorganic alkaline phenolic resin properties of the obtained product were tested according to the casting molding method described above, and the results were statistically summarized in Table 3.

[0090] Examples 2-2 to 2-23 The procedure is the same as in Example 2-1, except that the modified water glass is adjusted to the water glass prepared in Examples 1-2 to 1-23. Also, in Example 1, the results of the examples where the water glass color did not meet the standard will not be included in Table 3.

[0091] Example 2-24 The procedure was the same as in Example 2-1, except that the mass fraction of modified water glass in the alkaline phenolic resin was adjusted to 10%. The results are summarized in Table 3.

[0092] Example 2-25 The procedure was the same as in Example 2-1, except that the mass fraction of modified water glass in the alkaline phenolic resin was adjusted to 15%. The results are summarized in Table 3.

[0093] Example 2-26 The procedure was the same as in Example 2-1, except that the mass fraction of modified water glass in the alkaline phenolic resin was adjusted to 25%. The results are summarized in Table 3.

[0094] Example 2-27 The procedure was the same as in Example 2-1, except that the mass fraction of modified water glass in the alkaline phenolic resin was adjusted to 30%. The results are summarized in Table 3.

[0095] Comparative Example 2-1 The procedure was the same as in Example 2-1, except that the mass fraction of modified water glass in the alkaline phenolic resin was adjusted to 0%. The results are summarized in Table 3.

[0096] Table 3

[0097] In Examples 2-8, 2-11, and 2-20, the compressive strength of the modified water glass was too low, all below 1 MPa, failing to meet the standard, and no inorganic alkaline phenolic resin experiment was conducted. In Example 2-15, the performance of the modified water glass did not improve significantly after increasing the modification temperature during preparation, therefore the modified water glass prepared under these conditions was not used in the inorganic alkaline phenolic resin experiment.

[0098] Table 3 shows that after compounding with basic phenolic resin, the compressive strength of water glass modified with KH550 and methyltrimethoxysilane slightly decreased, but remained stable above 0.9 MPa overall. Furthermore, the formaldehyde content in Example 2-1 was relatively low, only higher than in Example 2-18. In contrast, the formaldehyde content of the phenolic resin without modified water glass (Comparative Example 2-1) was as high as 0.876 mg / g. When the mass of modified water glass added was 20% of the basic phenolic resin, the formaldehyde content reached its lowest level. When the addition amount was too high (e.g., 25% in Example 2-26 and 30% in Example 2-27), the compressive strength after 1 hour dropped sharply to 0.73 MPa and 0.56 MPa, respectively, failing to meet the process requirements. Despite the addition of inorganic components (modified water glass), no stratification occurred in the binders of all qualified examples (e.g., 2-1, 2-2, 2-3, 2-13, 2-14, etc.), demonstrating that the modified water glass and alkaline phenolic resin achieved good compatibility and stable miscibility. This successfully overcomes the technical challenge of "difficulty in miscibility between inorganic and organic binders" mentioned in the background art, providing a feasible path for developing high-performance composite binders. Generally, the compressive strength of inorganic alkaline phenolic resin after standing for 24 hours was improved compared to that of modified water glass after the same time. With the increase of temperature (Examples 2-13, 2-14) and reaction time (Examples 2-18, 2-19) of the modified water glass, the formaldehyde content will increase. Therefore, the strength of the water glass should be ensured first, and the reaction time and temperature of the water glass should be minimized as much as possible.

[0099] Example 3 The obtained inorganic alkaline phenolic resin was subjected to qualitative and quantitative phenolic tests as follows.

[0100] Inorganic alkaline phenolic resin was instantaneously pyrolyzed under a high-temperature inert atmosphere, decomposing it into volatile small molecule products, which were then separated and detected by gas chromatography-mass spectrometry (GC / MS). Qualitative analysis of phenolic substances (such as phenol, o-cresol, p-cresol, 2,6-dimethylphenol, 2,4-dimethylphenol, etc.) in the pyrolysis products was performed by comparing standard mass spectra and retention times. Quantitative analysis of the target phenolic compounds was conducted using the internal standard method (adding a known amount of internal standard (such as deuterated phenol or structural analogue) to the sample, and quantifying based on the response ratio of the target phenol to the internal standard).

[0101] Table 4. Comparison of qualitative and quantitative phenolic properties of the inorganic alkaline phenolic resin prepared by the steps of Example 1-1 with existing phenolic resins.

[0102] Unmodified resin refers to alkaline phenolic resin (commercially available from Shengquan) that has not been mixed with modified water glass.

[0103] As shown in Table 4, the content of all five free phenolic substances in the modified resin was significantly lower than that in the unmodified resin. This application introduced modified water glass (such as water glass treated with silane coupling agent KH560) into a composite with basic phenolic resin, providing more active sites (such as Si–OH) during the preparation process to form hydrogen bonds or condensation with free phenolic hydroxyl groups; it also altered the system's polarity or microenvironment, promoting the further participation of unreacted phenols in the resin condensation reaction; and it formed an organic-inorganic hybrid network structure, "encapsulating" or chemically anchoring some of the free phenols, thereby reducing their extractable / volatile content. The reduction of free phenols stems from the optimization of the chemical structure, indicating that the composite modification process did not destroy the basic cross-linking framework of the phenolic resin, but rather improved the reaction completeness and structural density while retaining its adhesive properties.

[0104] This application, by exploring the synthesis conditions of modified water glass and the mass ratio of modified water glass to resin, determined the optimal synthesis route and ratio. The method provided in this application can significantly reduce the emission of harmful gases in the final product, improve the product's environmental friendliness, and simultaneously maintain or even improve the mechanical strength and other key performance indicators of the modified resin to meet a wider range of application needs. This is achieved by solving the problem of miscibility between inorganic and organic components.

[0105] Although the embodiments of this application have been described above, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A method for preparing a casting sand mold binder, wherein, The method includes: Preparation of modified water glass; Preparation of basic phenolic resin; Modified water glass is mixed with alkaline phenolic resin to obtain a casting sand mold binder; The preparation of modified water glass includes: Sodium silicate was added to a stirred tank, followed by the addition of sodium hydroxide to adjust the modulus of the silicate. Then, a modifier solution was added to the reaction vessel, stirred until homogeneous, and reacted at a constant temperature to obtain modified silicate.

2. The method according to claim 1, wherein, The modifier is selected from epoxy silane modifiers or amino silane modifiers. The modifier accounts for 0.1%-1.0% of the mass fraction of the sodium silicate.

3. The method according to claim 1, wherein, The temperature of the isothermal reaction is 70℃-120℃, preferably 85-95℃; The isothermal reaction time is 5-12 hours, preferably 8-10 hours.

4. The method according to claim 1, wherein, The modulus of the water glass is 1.8-2.

3.

5. The method according to claim 1, wherein, The preparation of the alkaline phenolic resin includes... Phenol and KOH solution are mixed in a reaction vessel at a certain mass ratio, and then formaldehyde solution is added to obtain the alkaline phenolic resin.

6. The method according to claim 5, wherein, The mass ratio of phenol, formaldehyde, and KOH solution is 1:(0.4-1.2):(1.7-2.4).

7. The method according to claim 1, wherein, In the mixture, the modified water glass accounts for 10%-20% of the mass fraction of the alkaline phenolic resin.

8. The method according to claim 1, wherein, A modifier, specifically a silane modifier, is added during the mixing process of modified water glass and alkaline phenolic resin.

9. A casting sand mold binder, prepared according to any one of claims 1-8.

10. The method according to any one of claims 1-8, or the application of the casting sand mold binder according to claim 9 in the casting field.

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