Sand mould prepared using high-strength cold-box process, method for preparing same and use thereof
By controlling the reaction process and using formate curing agents, the problem of flammability and volatility of methyl formate in the cold box process was solved, achieving safe production and quality improvement of high-strength phenolic resin sand molds.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINAN SHENGQUAN GRP SHARE HLDG CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-09
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This application relates to the field of casting technology, and in particular to a sand mold prepared using a high-strength cold box process, its preparation method, and its application. Background Technology
[0002] The cold box method widely refers to a resin sand molding process that uses gas or aerosol catalysis or curing to instantly form cores at room temperature. Common characteristics of this process include: a longer usable time after resin sand mixing; shorter blown curing and demolding time; high production efficiency; and the ability to achieve simultaneous core making on rapid molding production lines. Furthermore, the core box manufacturing cost is low, and energy consumption is minimal, thus demonstrating significant application potential.
[0003] Currently, common cold box processes mainly include the following: triethylamine cold box process, SO2 cold box process, and the relatively environmentally friendly organic ester-cured alkaline phenolic resin cold box process. While the first two cold box processes offer fast curing speeds and high strength, the permissible concentration limits for triethylamine and SO2 in air are 5 ppm and 2 ppm, respectively. Therefore, the low-toxicity / non-toxic alkaline phenolic resin curing cold box process was subsequently developed. Organic ester-cured alkaline phenolic resin was first successfully developed by Borden in the UK in 1984. European patent EP 86615B1 details the synthesis method of alkaline phenolic resin in the methyl formate gas-cured alkaline phenolic resin cold box process. In this patent, the methyl formate-cured alkaline phenolic resin cold box process yielded a 24-hour strength of 3.0-4.5 MPa in the compression test blocks, meeting the strength requirements of the production process.
[0004] Although this cold-box process is relatively environmentally friendly, its curing agent, methyl formate, has a low boiling point of only 35°C, making it flammable and highly volatile at room temperature. Due to the mechanism by which methyl formate cures alkaline phenolic resin, the concentration of methyl formate affects the molding strength of alkaline phenolic resin sand, making it difficult to prepare sand cores with complex processes. During sand core production in the molding workshop, the room temperature is generally not very low due to production constraints, which raises safety concerns regarding the transportation, storage, and use of methyl formate curing agent in the workshop. Excessive workshop temperature can cause excessive pressure in the storage tanks containing methyl formate; the overflow of volatile gases can lead to excessively high concentrations in localized areas, potentially causing an explosion and posing a production safety hazard. Summary of the Invention
[0005] Based on the technical problems existing in the prior art, this application provides a method for preparing sand molds using a high-strength cold box process. This method involves mixing phenol with alkaline substances in an alkaline solution, adding formaldehyde solution, and then heating to react. After reacting for a period of time, the mixture is cooled and then alkaline solution, water, and additives are added to continue the reaction. This method can result in a narrow molecular chain distribution of the obtained phenolic resin, and the use of formate ester curing agents can achieve better curing results.
[0006] The specific technical solution of this application is as follows:
[0007] This application provides a method for preparing sand molds using a high-strength cold box process, comprising:
[0008] Phenol is mixed with an alkaline solution, then formaldehyde solution is added, and the mixture is heated to react. After reacting for a period of time, the mixture is cooled and then an alkaline solution, water, and additives are added to react and obtain a phenolic resin solution.
[0009] The phenolic resin solution is mixed with refractory material to obtain a mixture. After the curing agent is heated and vaporized, it is blown into the mixture through a core shooter to obtain a sand mold. The curing agent is a formate-based curing agent.
[0010] The molar ratio of the alkaline substance added to the alkaline solution for cooling to phenol is 0.2-0.5:1;
[0011] The formate curing agent is a compound with 2-5 carbon atoms.
[0012] Optionally, in the method described above, the formate ester compound is methyl formate, ethyl formate, propyl formate, butyl formate, or isobutyl formate.
[0013] Optionally, in the method described above, the alkaline substance in the alkaline solution is sodium hydroxide or potassium hydroxide.
[0014] Optionally, in the method described above, the additive is a silane coupling agent, and optionally, the silane coupling agent is KH-550, KH-560 or KH-570.
[0015] Optionally, in the method described above, the molar ratio of water to phenol is 1-5:1.
[0016] Optionally, in the method described above, the cooling and addition of alkaline solution, water and additives involves lowering the temperature to 45-55°C before adding the alkaline solution, water and additives. Optionally, the temperature is lowered to below 40°C after adding the alkaline solution and water before adding the additives.
[0017] Optionally, in any of the methods described above, the mass ratio of phenol to the alkaline substance in the alkaline solution is 1:0.3-1.
[0018] Optionally, in any of the methods described above, the mass ratio of phenol to formaldehyde in the formaldehyde solution is 1:1.5-3.
[0019] This application provides a sand mold prepared by any of the methods described above.
[0020] This application provides the use of the sand molds described above in the casting field.
[0021] Beneficial effects
[0022] The method for preparing sand molds using a high-strength cold box process provided in this application employs formate ester compounds as curing agents. Because the intrinsic structure of the ester group has -H and alkyl groups on either side, the -O in -COO- exhibits a conjugation effect with the -H in the hydroxyl groups of the basic phenolic resin, thereby promoting the crosslinking of the basic phenolic resin. The presence of long alkyl chains in the organic ester strengthens the intermolecular forces, increases the boiling point, and makes it less volatile. Furthermore, the β-C linked to the carbonyl group has a stronger electron-donating ability. While the curing speed with the basic phenolic resin sand is slower, this allows for better dispersion of the vaporized ester within the sand core, resulting in more uniform strength and a better sand mold.
[0023] Furthermore, the method described in this application employs a stepwise alkali addition and gradual heating approach, resulting in a narrow molecular chain distribution in the synthesized alkaline phenolic resin, and the formed molecular segments have a higher content of hydroxymethyl groups. Therefore, the sand molds prepared by this method can significantly improve the safety of the cold box method for alkaline phenolic resin production, avoiding the explosion and fire hazards caused by the vaporization of organic esters during sand mold production, ensuring safe production, and the addition of a novel curing agent can improve the quality of the sand molds. Detailed Implementation
[0024] The present application will now be described in detail with reference to the described embodiments. Although 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 so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.
[0025] 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 "comprising 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.
[0026] This application provides a method for preparing sand molds using a high-strength cold box process, comprising:
[0027] Phenol is mixed with an alkaline solution, then formaldehyde solution is added, and the mixture is heated to react. After reacting for a period of time, the mixture is cooled and then an alkaline solution, water, and additives are added to react and obtain a phenolic resin solution.
[0028] The phenolic resin solution is mixed with refractory material to obtain a mixture. The curing agent is heated and vaporized, and then cold-blown into the mixture through a core shooter to obtain a sand mold. The curing agent is a formate curing agent.
[0029] This application mixes phenol with an alkaline solution, adds formaldehyde solution, then cools down and adds alkaline solution, water and additives. Since KOH is used as a catalyst, its stepwise addition can slow down the catalytic rate during the reaction, thereby resulting in a higher 24-hour tensile strength of the final sand core.
[0030] In this application, no restrictions are placed on the amount of curing agent added. Those skilled in the art can make conventional selections based on actual needs. For example, the amount of curing agent added can be 25-30% of the phenolic resin solution. For example, when the amount of phenolic resin solution added is 1g, the amount of curing agent added is 0.25-0.30g.
[0031] For example, the amount of curing agent added can be 25%, 26%, 27%, 28%, 29%, 30% of the phenolic resin solution.
[0032] In this application, no restrictions are placed on the refractory material. Conventional refractory materials used in high-strength cold box processes can be used, such as sand.
[0033] In this application, no restrictions are placed on the amount of refractory material used. Those skilled in the art can make conventional selections based on actual needs, as long as the requirements of this application are met.
[0034] In this application, no restrictions are placed on the molar ratio of phenol to alkaline substances in the alkaline solution. Those skilled in the art can make conventional selections based on actual needs, as long as the requirements of this application are met. For example, the molar ratio of phenol to alkaline substances in the alkaline solution can be 1:0.3-1.0.
[0035] For example, the molar ratio of phenol to alkaline substances in an alkaline solution can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, etc.
[0036] In this application, the formaldehyde solution should be added at a low temperature to allow it to react with phenol; optionally, the formaldehyde solution is added at 60-70°C, for example at 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, etc.
[0037] In this application, no restrictions are placed on the concentration of formaldehyde in the formaldehyde solution. Those skilled in the art can make conventional selections according to actual needs, such as using a formaldehyde solution with a concentration of 48%.
[0038] In this application, no restrictions are placed on the molar ratio of phenol to formaldehyde in the formaldehyde solution. Those skilled in the art can make conventional choices based on actual needs. For example, the molar ratio of phenol to formaldehyde in the formaldehyde solution can be 1:1.5-3.
[0039] For example, the molar ratio of phenol to formaldehyde in a formaldehyde solution can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, etc.
[0040] After the addition is complete, raise the temperature to 80-90℃ to carry out the reaction, for example, raise the temperature to 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, etc.
[0041] In this application, "reaction period" refers to a reaction time of 3-3.5 h during which the reaction system is cooled down.
[0042] In this application, the term "sand mold" has the meaning commonly understood by those skilled in the art, referring to a casting mold with a cavity corresponding to the shape of a part, obtained by hardening a resin sand blowing curing agent in a core shooting machine mold through a cold core box process.
[0043] In some embodiments, the formate curing agent is a compound having 2-5 carbon atoms. Optionally, the formate compound is methyl formate, ethyl formate, propyl formate, butyl formate, or isobutyl formate.
[0044] In some embodiments, the molar ratio of the alkaline substance added to the alkaline solution during cooling to phenol is 0.2-0.5:1, preferably 0.2-0.3:1. Optionally, the alkaline substance in the alkaline solution is sodium hydroxide or potassium hydroxide.
[0045] For example, the molar ratio of alkaline substances to phenol in the alkaline solution can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, etc.
[0046] In some embodiments, the additive is a silane coupling agent, optionally KH-550, KH-560 or KH-570.
[0047] In some implementations, the molar ratio of water to phenol is 1-5:1.
[0048] For example, the molar ratio of water can be 1:1, 2:1, 3:1, 4:1, 5:1, etc.
[0049] In some embodiments, the cooling and addition of alkaline solution, water and additives involves lowering the temperature to 45-55°C before adding the alkaline solution, water and additives. Optionally, the temperature is lowered to below 40°C after adding the alkaline solution and water before adding the additives.
[0050] For example, the temperature can be lowered to 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, etc., and then alkaline solution, water, and additives can be added.
[0051] In this application, no restrictions are placed on the amount of additives used; the amount of additives commonly used in the art can be used, as long as it meets the requirements of this application.
[0052] This application provides a sand mold prepared by any of the methods described above.
[0053] The sand mold described in this application is tested using conventional methods in the art, and its instantaneous tensile strength and 24-hour tensile strength are both high, thus it can be used in the casting field.
[0054] This application provides the use of the sand molds described above in the casting field.
[0055] Example
[0056] 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.
[0057] Example 1
[0058] Preparation of alkaline phenolic resin solution: 94.11 g of phenol (1 mol) and 46.77 g of 48% KOH solution (0.6 mol) were mixed and heated to 60-70℃. 126.44 g of 48% formaldehyde solution was added, and the temperature was raised to 85℃. After reacting for 3-3.5 h, the temperature was lowered to 50℃, and 23.38 g of 48% KOH solution (0.2 mol) and 36 ml of H2O (2 mol) were added to continue the reaction. After reacting for 1 h, the reaction system was cooled to 40℃ and 1.88 g of additive (silane coupling agent, KH-550) was added and stirred to obtain alkaline phenolic resin solution.
[0059] Sand mold preparation:
[0060] The obtained alkaline phenolic resin solution was mixed evenly with 1000g of sand to obtain a mixture, which was then placed in a core shooter. 5.4g of curing agent butyl formate was vaporized by the heating device in the core shooter and then evenly blown onto the mixture through a cold core box process to obtain a high sand mold.
[0061] Example 2
[0062] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0063] The difference between Example 2 and Example 1 is that isobutyl formate is used as the curing agent to obtain the sand mold.
[0064] Example 3
[0065] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0066] The difference between Example 3 and Example 1 is that methyl formate is used as the curing agent to obtain the sand mold.
[0067] Example 4
[0068] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0069] The difference between Example 4 and Example 1 is that ethyl formate is used as the curing agent to obtain the sand mold.
[0070] Example 5
[0071] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0072] The difference between Example 5 and Example 1 is that propyl formate is used as the curing agent to obtain the sand mold.
[0073] Example 6
[0074] The difference between Example 6 and Example 1 is that after cooling, 35.78g of 48% KOH solution (0.3mol) was added to obtain an alkaline phenolic resin solution.
[0075] The preparation of the sand mold is the same as in Example 1.
[0076] Example 7
[0077] The difference between Example 7 and Example 1 is that after cooling, 46.77g of 48% KOH solution (0.4mol) was added to obtain an alkaline phenolic resin solution.
[0078] The preparation of the sand mold is the same as in Example 1.
[0079] Example 8
[0080] The difference between Example 8 and Example 1 is that after cooling, 59.63g of 48% KOH solution (0.5mol) was added to obtain an alkaline phenolic resin solution.
[0081] The preparation of the sand mold is the same as in Example 1.
[0082] Example 9
[0083] The difference between Example 9 and Example 1 is that the additive KH-560 is added to obtain an alkaline phenolic resin solution.
[0084] The preparation of the sand mold is the same as in Example 1.
[0085] Example 10
[0086] The difference between Example 10 and Example 1 is that the additive KH-570 was added to obtain an alkaline phenolic resin solution.
[0087] The preparation of the sand mold is the same as in Example 1.
[0088] Comparative Example 1
[0089] The difference between Comparative Example 1 and Example 1 is that after cooling, 48% KOH solution (0.2 mol of KOH) and water were not added to obtain an alkaline phenolic resin solution.
[0090] The preparation of the sand mold is the same as in Example 1.
[0091] Comparative Example 2
[0092] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0093] The difference between Comparative Example 2 and Example 1 is that γ-butyrolactone is used as the curing agent to obtain the sand mold.
[0094] Comparative Example 3
[0095] The difference between Comparative Example 3 and Example 1 is that the additive used is KH-792 to obtain an alkaline phenolic resin solution.
[0096] The preparation of the sand mold is the same as in Example 1.
[0097] Comparative Example 4
[0098] Preparation of alkaline phenolic resin solution: 94.11 g of phenol (1 mol) and 70.16 g of 48% KOH solution (0.8 mol) were mixed. The mixture was heated to 60-70℃, and 126.44 g of 48% formaldehyde solution was added. The temperature was raised to 85℃ and reacted for 3-3.5 h. The temperature was then lowered to 50℃, and 36 ml of H2O was added to continue the reaction. After reacting for 1 h, the reaction system was cooled to 40℃ and 1.88 g of additive (silane coupling agent, KH-550) was added and stirred to obtain alkaline phenolic resin solution.
[0099] The preparation of the sand mold is the same as in Example 1.
[0100] Comparative Example 5
[0101] The preparation of the alkaline phenolic resin solution is the same as in Example 1.
[0102] The difference between Comparative Example 5 and Example 1 is that carbon dioxide is used as the curing agent to obtain the sand mold.
[0103] Experimental Example
[0104] The properties of the sand molds in the examples and comparative examples were determined according to GB / T 24413-2009, and the results are shown in Table 1.
[0105] Table 1
[0106]
[0107] As can be seen from the table above, the butyl formate-cured alkaline phenolic resin sand in Example 1 exhibits the best tensile strength, with an immediate tensile strength of 0.386 MPa and a 24-hour tensile strength of 0.955 MPa. In Examples 2, 3, 4, and 5, isobutyl formate, methyl formate, ethyl formate, and propyl formate were used as curing agents to cure the resin sand, respectively. The initial strength of the resin sand cured with isobutyl formate in Example 2 was 0.258 MPa, which is lower than that of the other three examples. This is mainly because the isobutyl group in isobutyl formate has large steric hindrance, which hinders the reaction rate between the curing agent and the active groups in the alkaline phenolic resin during the initial reaction, thus resulting in lower strength. Methyl formate and ethyl formate cure alkaline phenolic resin... Although the tensile strength of aldehyde resins is not significantly different, they pose production safety hazards due to their low boiling point, high volatility, flammability, and explosiveness. Propyl formate is also expensive and has high production costs. In contrast, the conventional curing agent γ-butyrolactone used in Comparative Example 2 showed a much lower initial strength than the examples during the curing experiment. This is because γ-butyrolactone has a cyclic structure, which is stable, and the activation of its groups and electron transfer require time. It reacts more slowly with the active groups of alkaline phenolic resins than formate esters, resulting in a lower initial strength of only 0.106 MPa. In Examples 6, 7, and 8, the different amounts of KOH added in the later stages of the reaction of the alkaline phenolic resin also affected the tensile strength of the resin. As the amount added increased, the strength tended to decrease. This was mainly because the catalytic effect of KOH and the hydroxyl groups caused the alkaline phenolic resin to react quickly in the early stages of curing, resulting in higher strengths than in Example 1, at 0.421 MPa, 0.398 MPa, and 0.366 MPa, respectively. However, due to the excessively rapid catalysis, the resin reacted excessively in some areas, causing molecular chain breakage, and thus the final strength was not high, all lower than the 0.955 MPa in Example 1. In contrast, Comparative Example 1 did not add KOH or water for dilution, and the viscosity of the alkaline phenolic resin was too high to conduct strength tests. By changing the additives, it can be seen from Examples 9 and 10 that the strengths are similar; using the KH-792 additive in Comparative Example 3, which is a silane coupling agent with diamino groups, it reacts with some active groups when added to the alkaline phenolic resin solution, resulting in a lower initial strength of 0.283 MPa; in Comparative Example 4, KOH is added directly in the first step, because OH... - The mutual repulsion between the hydroxyl anions in phenol and formaldehyde results in a short polymer chain during the condensation reaction of phenol and formaldehyde, leading to low tensile strength in the tensile strength test. In contrast, Comparative Example 5 uses carbon dioxide for curing. Since metal salt ions are added for coordination crosslinking and curing during this process, the hygroscopicity of metal salt ions and their weaker crosslinking properties compared to chemical bonds result in a 24-hour tensile strength that is much lower than that in Example 1.
[0108] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.
Claims
1. A method for preparing sand molds using a high-strength cold box process, comprising: Phenol is mixed with an alkaline solution, then formaldehyde solution is added, and the mixture is heated to react. After reacting for a period of time, the mixture is cooled and then an alkaline solution, water, and additives are added to react and obtain a phenolic resin solution. The phenolic resin solution is mixed with refractory material to obtain a mixture. After the curing agent is heated and vaporized, it is blown into the mixture through a core shooter to obtain a sand mold. The curing agent is a formate-based curing agent. The molar ratio of the alkaline substance added to the alkaline solution for cooling to phenol is 0.2:1; The formate curing agent is butyl formate; The additive is a silane coupling agent, specifically KH-550, KH-560, or KH-570.
2. The method according to claim 1, wherein the alkaline substance in the alkaline solution is sodium hydroxide or potassium hydroxide.
3. The method according to claim 1, wherein the molar ratio of water to phenol is 1-5:
1.
4. The method according to claim 1, wherein the cooling and addition of alkaline solution, water and additives involves lowering the temperature to 45-55°C before adding alkaline solution and water, and then cooling the temperature to below 40°C before adding additives.
5. The method according to any one of claims 1-4, wherein the molar ratio of phenol to the alkaline substance in the alkaline solution is 1:0.3-1.
6. The method according to any one of claims 1-4, wherein the molar ratio of phenol to formaldehyde in the formaldehyde solution is 1:1.5-3.
7. A sand mold prepared by the method described in any one of claims 1-6.
8. The use of the sand mold according to claim 7 in the casting field.