Environment-friendly release agent for metal casting and preparation method thereof

Abstract

The invention relates to the field of environment-friendly release agents for metal casting, in particular to an environment-friendly release agent for metal casting and a preparation method thereof. The invention discloses an environment-friendly release agent for metal casting. The environment-friendly release agent comprises the following substances in parts by weight: 30-35 parts of a bio-based film-forming matrix; 15 to 20 parts of pentaerythritol stearate; 5-8 parts of nano cellulose; the bio-based film forming matrix comprises epoxy modified castor oil. According to the environment-friendly release agent disclosed by the invention, a basic system of the environment-friendly release agent is constructed through the synergistic effect of the bio-based film forming matrix, the pentaerythritol stearate and the nano cellulose. Under the synergistic effect of the three components, the system realizes the balance of environmental protection and functionality: the environment accumulation risk of the traditional petroleum-based component is reduced by the bio-based material, and the matching of the lubricating component and the reinforcing phase ensures that the film layer is not easy to damage in the demolding process, so that the surface adhesion and defects of the casting are effectively avoided, and the casting efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly metal casting release agents, specifically to an environmentally friendly metal casting release agent and its preparation method. Background Technology

[0002] Metal casting is a process in which molten metal is poured into a mold cavity and allowed to cool and solidify to obtain a casting of a specific shape. Release agents, as a key auxiliary material in the casting process, function to form an insulating film between the molten metal and the mold surface, reducing the interfacial adhesion between the casting and the mold, ensuring smooth demolding and minimizing surface defects. With the increasing popularity of green manufacturing concepts, traditional release agents have gradually revealed numerous problems and are no longer sufficient to meet the needs of the modern casting industry.

[0003] Release agents for metal casting are mainly classified into mineral oil-based, synthetic resin-based, and silicone oil-based types. While mineral oil-based release agents are lower in cost, they have poor biodegradability, leading to soil and water pollution with long-term use. Furthermore, they are prone to volatilization at high temperatures, producing harmful fumes that endanger operator health. Synthetic resin-based release agents, while offering improved heat resistance, form a brittle film after curing that is prone to cracking and peeling, resulting in unstable release performance. Residual organic components are also prone to carbonization at high temperatures, affecting the surface quality of castings. Silicone oil-based release agents, while possessing excellent lubricity, have poor compatibility with the metal matrix, easily causing defects such as pinholes and shrinkage cavities on the casting surface. Moreover, their strong bioaccumulation poses a potential risk to the ecological environment.

[0004] In response to the aforementioned existing technologies, the inventors discovered that existing environmentally friendly release agents cannot repair themselves after the film layer is damaged due to mechanical friction or sudden temperature changes during the casting process, requiring frequent recoating, which increases process costs and operational complexity. At the same time, the performance of traditional release agents is sensitive to temperature changes, and their viscosity, film-forming properties, and lubricity fluctuate greatly within the temperature range of different casting processes, making it difficult to achieve stable adaptation to complex castings or high-precision casting scenarios. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides an environmentally friendly metal casting release agent and its preparation method.

[0006] In the first aspect, this application provides an environmentally friendly release agent for metal casting, employing the following technical solution:

[0007] An environmentally friendly release agent for metal casting comprises the following components by weight: 30-35 parts of a bio-based film-forming matrix; 15-20 parts of pentaerythritol stearate; and 5-8 parts of nanocellulose; wherein the bio-based film-forming matrix includes epoxy-modified castor oil.

[0008] Through the above technical solution, this application constructs a basic system for an environmentally friendly release agent by leveraging the synergistic effect of a bio-based film-forming matrix, pentaerythritol stearate, and nanocellulose. The epoxy groups and hydroxyl groups in the epoxy-modified castor oil molecule form a cross-linked network, endowing the film with excellent flexibility and adhesion. Pentaerythritol stearate, as a lubricant, forms an oriented adsorption layer on the metal surface through long-chain fatty acid segments, reducing the interfacial tension between the casting and the mold. Nanocellulose, through its nanoscale fibrous structure, constructs a physical support framework within the film, enhancing its mechanical strength and high-temperature resistance. The synergistic effect of these three components achieves a balance between environmental friendliness and functionality: the bio-based material reduces the environmental accumulation risks of traditional petroleum-based components, while the combination of the lubricating components and the reinforcing phase ensures that the film is not easily damaged during the release process, effectively preventing surface adhesion and defects in the casting and improving casting efficiency.

[0009] Furthermore, the epoxy-modified castor oil is an epoxy-modified castor oil that has undergone heat-resistant modification treatment, and the heat-resistant modification treatment adopts the following technical solution:

[0010] Under nitrogen protection, epoxy castor oil and bio-based diamine monomer are mixed at a molar ratio of 1:1-1.5 and reacted at 75-85℃ for 3-5 hours to prepare heat-resistant modified epoxy castor oil.

[0011] Through the above technical solution, this application further optimizes the high-temperature stability of the film-forming matrix by performing heat-resistant modification treatment on epoxy-modified castor oil. The bio-based diamine monomer undergoes a ring-opening reaction with the epoxy groups in the epoxy castor oil, introducing an amino cross-linked structure into the molecular chain to form a three-dimensional network polymer. This chemical modification increases the cross-linking density between molecular chains, thereby raising the polymer's glass transition temperature and thermal decomposition temperature. Simultaneously, the polar characteristics of the amino groups enhance the intermolecular interaction forces, reducing the thermal motion of the molecular chains at high temperatures. The modified film-forming matrix is ​​less prone to thermal oxidative degradation in the high-temperature environment of the casting process, maintaining the integrity of the film structure and avoiding the carbide residues produced by the high-temperature decomposition of traditional release agents. This extends the effective action time of the release agent and reduces the difficulty of cleaning the casting surface.

[0012] Furthermore, the bio-based diamine monomer is decanediamine.

[0013] Through the above technical solution, this application optimizes the reaction efficiency and product performance of heat-resistant modification treatment by limiting the bio-based diamine monomer to decanediamine. Decanediamine, as a long-chain aliphatic diamine, has a suitable carbon chain length and reactivity: the methylene unit in the carbon chain provides flexibility to the molecular chain, avoiding film brittleness caused by excessive cross-linking; while the amino groups at both ends can react efficiently with epoxy groups, ensuring controllable cross-linking degree. Compared to aromatic diamines or short-chain aliphatic diamines, the bio-based source of decanediamine further enhances the environmentally friendly properties of the release agent, while the hydrophobic segments in its molecular structure can improve the water resistance of the film-forming matrix, reducing the risk of release agent failure in humid environments.

[0014] Furthermore, the environmentally friendly metal casting release agent also includes 10-15 parts by weight of self-healing microcapsules, wherein the self-healing microcapsules comprise a core material of tung oil-epoxidized soybean oil and a wall material of urea-formaldehyde resin.

[0015] Through the above technical solution, this application introduces self-healing microcapsules, endowing the release agent with dynamic damage repair capabilities. A tung oil-epoxidized soybean oil core material is encapsulated within a urea-formaldehyde resin wall material, forming a micron-sized capsule structure. When microcracks appear in the release agent film due to mechanical friction or temperature stress, the mechanical energy generated during crack propagation triggers the rupture of the microcapsule wall material, releasing the reactive core material components. The unsaturated fatty acid segments in the tung oil can undergo oxidative cross-linking reactions with the epoxidized soybean oil in air, or combine with active groups in the film-forming matrix, filling the crack gaps and reforming a continuous film. The effect of this self-healing mechanism is that even if the film is locally damaged, it can restore its integrity through self-repair, reducing casting adhesion problems caused by film damage, extending the single-use lifespan of the release agent, and reducing the frequency of recoating. It is particularly suitable for complex cavity castings or long-cycle casting processes.

[0016] Furthermore, the environmentally friendly metal casting release agent also includes 15-20 parts by weight of an adaptive temperature-modifying material.

[0017] Through the above technical solution, this application enables the release agent to have a dynamic response capability to temperature changes by adding an adaptive temperature-modifying material. The polymer chain segments in the adaptive temperature-modifying material undergo conformational transformation or phase change at different temperatures: at low temperatures, the molecular chains are in an extended state, which can increase the viscosity of the system and improve the adhesion of the film layer; at high temperatures, the molecular chains are coiled or undergo microphase separation, reducing internal friction and maintaining good lubricity.

[0018] Furthermore, the adaptive temperature-modified materials include poly(N-isopropylacrylamide)-polycaprolactone block copolymer and polyethylene glycol-polylactic acid copolymer mixed in a mass ratio of (2-3):1.

[0019] Through the above technical solution, this application utilizes the synergistic effect of poly(N-isopropylacrylamide)-polycaprolactone block copolymer and polyethylene glycol-polylactic acid copolymer: the poly(N-isopropylacrylamide)-polycaprolactone block copolymer segments provide temperature sensitivity; when the ambient temperature is higher than its lower critical solution temperature, the segments change from hydrophilic to hydrophobic and shrink; the polycaprolactone segments provide flexibility and crystallinity at low temperatures, improving low-temperature viscosity; the PEG segments in the polyethylene glycol-polylactic acid copolymer have hydrophilicity and lubricity, while the PLA segments enhance compatibility with bio-based film-forming matrices.

[0020] Furthermore, the self-healing microcapsules are manufactured using the following technical solution:

[0021] Weigh out formaldehyde aqueous solution and urea according to the molar ratio of urea to formaldehyde 1:1-2. Place the formaldehyde aqueous solution in a reaction vessel, adjust the pH, add urea, heat and keep warm to react, and obtain urea-formaldehyde prepolymer.

[0022] Tung oil and epoxidized soybean oil were mixed in a 1:1 mass ratio, and the mixture was collected. 3% of the total mass of the core material was added to Span-80 emulsifier and stirred evenly. The mixture was then slowly dripped into deionized water and subjected to high-speed shearing to prepare an O / W type core material emulsion.

[0023] The urea-formaldehyde prepolymer and core material emulsion were stirred and mixed, and the pH was adjusted to 2.5-3.0. The mixture was heated and stirred, and after the reaction was completed, it was centrifuged, washed and dried to prepare self-healing microcapsules.

[0024] Through the above technical solution, this application optimizes the preparation process of self-healing microcapsules to ensure efficient coating and controllable release of the core material. The microcapsules prepared by this solution have a uniform particle size distribution and controllable wall thickness, which can not only avoid premature damage to the capsules by mechanical external forces during the casting process, but also accurately release the core material when the membrane cracks occur. At the same time, the temperature resistance of the urea-formaldehyde resin wall material ensures that the microcapsules do not rupture prematurely in the high-temperature casting environment, further improving the reliability of the self-healing function.

[0025] Secondly, this application provides a method for preparing an environmentally friendly release agent for metal casting, employing the following technical solution:

[0026] A method for preparing an environmentally friendly release agent for metal casting includes the following preparation steps:

[0027] After selecting a bio-based film-forming substrate and heating it once, add an adaptive temperature-modifying material and stir to mix. Then add self-healing microcapsules, pentaerythritol stearate and nanocellulose. After heating a second time and ultrasonically dispersing and collecting the emulsion, the environmentally friendly metal casting release agent can be prepared.

[0028] Through the above technical solution, this application achieves uniform mixing and synergistic performance of a multi-component system by designing a phased preparation process. The first heating step is for the pretreatment of the bio-based film-forming matrix, reducing its viscosity through gentle heating to provide a fluidity basis for subsequent material mixing. After adding the temperature-adaptive modifier and stirring, the intermolecular forces between the materials promote compatibility. The second heating step and ultrasonic dispersion target solid or high-viscosity components such as self-healing microcapsules, pentaerythritol stearate, and nanocellulose. Increasing the temperature reduces system resistance, and the cavitation effect of ultrasound breaks up agglomerates, ensuring uniform dispersion of nanocellulose and stable suspension of microcapsules. This step-by-step treatment avoids problems such as excessively high local concentrations and uneven dispersion caused by one-time mixing of multiple components. In particular, it prevents the agglomeration of nanocellulose and mechanical damage to microcapsules, ultimately obtaining a highly stable emulsion with synergistic effects among the functional components, ensuring batch-to-batch consistency of the release agent.

[0029] Furthermore, the initial heating process involves raising the temperature to 40-50°C at a rate of 2-3°C / min.

[0030] Through the above technical solution, this application limits the heating rate and the final temperature of a single heating cycle, thus protecting the structural integrity of the bio-based film-forming substrate.

[0031] Furthermore, the secondary heating process involves raising the temperature to 60-80°C at a rate of 1-2°C / min.

[0032] Through the above technical solution, this application optimizes the rate and temperature parameters of secondary heating, ensuring the efficient dispersion and stability of functional components.

[0033] In summary, this application has the following beneficial effects:

[0034] First, this application uses epoxy-modified castor oil as the film-forming matrix, which is derived from renewable plant resources, replacing traditional petroleum-based resins or mineral oils, thus reducing the environmental accumulation risk of non-degradable components at the raw material level. Simultaneously, the introduction of bio-based diamine monomers further enhances the system's biodegradability. The natural fatty acid segments in its molecular structure can be decomposed into harmless small molecules in the natural environment through microbial action, avoiding the biotoxicity of traditional synthetic amine curing agents. Furthermore, both the urea-formaldehyde resin wall material of the self-healing microcapsules and the tung oil-epoxy soybean oil core material are biodegradable organic materials, and the plant-derived nature of nanocellulose ensures the biocompatibility of the entire system.

[0035] Secondly, this application overcomes the technical bottleneck of traditional release agents' single-performance optimization and overall performance imbalance through multi-component functional synergy and structural design. On the one hand, the self-healing microcapsules endow the system with dynamic damage repair capabilities: when the film layer develops microcracks due to mechanical friction or temperature stress, the core material components are released through rupture and undergo cross-linking reactions, autonomously filling the defects. This avoids casting adhesion and surface defects caused by film layer damage in traditional release agents, significantly extending the single-use cycle. On the other hand, the adaptive temperature-modified material achieves dynamic response to temperature changes through molecular chain conformational transformation: maintaining high viscosity at low temperatures to enhance adhesion, and reducing internal friction through chain segment coiling at high temperatures to ensure lubricity, solving the problem of large performance fluctuations of traditional release agents in different casting process temperature ranges. In addition, the three-dimensional network skeleton of nanocellulose and the directional lubricating layer of pentaerythritol stearate form a "reinforcement-lubrication" synergistic structure, which not only improves the mechanical strength and high-temperature resistance of the film layer, but also reduces interfacial adhesion. This multifunctional synergistic mechanism enables the release agent to simultaneously possess self-healing, temperature-adaptive, high-strength, and low-friction properties, meeting the needs of high-end scenarios such as complex castings and high-precision casting.

[0036] Third, this application ensures the structural integrity and uniform dispersion of each functional component through refined process control and step-by-step processing strategies, providing a process guarantee for the stable application of the release agent. In the microcapsule preparation stage, the wall material thickness and core material coverage are precisely controlled through a two-step emulsification-in-situ polymerization method, avoiding the core material leakage problem caused by traditional physical mixing methods. In the matrix mixing stage, gradient heating and nitrogen protection technology are used to prevent the bio-based material from undergoing oxidative degradation due to localized overheating, preserving the reactivity of epoxy groups and amino groups. In the functional component dispersion stage, the hydrogen bond aggregation network of nanocellulose is broken through a combination of ultrasonic cavitation effect and low-speed stirring, ensuring its uniform embedding into the matrix to form a reinforced structure, while avoiding mechanical damage to the self-healing microcapsules. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments.

[0038] It should be noted that, unless otherwise specified, the raw materials used in this application are analytical grade materials;

[0039] Poly(N-isopropylacrylamide-polycaprolactone) block copolymer: Hangzhou Xinqiao Biotechnology Co., Ltd.: PCL-PNIPAAm MW: 5000.

[0040] Preparation Example 1

[0041] Epoxy-modified castor oil 1 after heat-resistant modification

[0042] First, weigh epoxidized castor oil and decanediamine at a molar ratio of 1:1. Add the decanediamine to the epoxidized castor oil at a dropping rate of 1 drop / s. Heat the mixture to 75°C at a rate of 1°C / min. During the heating process, increase the stirring speed to 300 rpm and keep the mixture at this temperature for 3 hours to prepare heat-resistant modified epoxidized castor oil 1.

[0043] Preparation Example 2

[0044] Epoxy-modified castor oil 2 after heat-resistant modification

[0045] First, weigh epoxy castor oil and decanediamine at a molar ratio of 1:1.2. Add the decanediamine to the epoxy castor oil at a dropping rate of 1 drop / s. Heat the mixture to 80°C at a rate of 1°C / min. During the heating process, increase the stirring speed to 350 rpm and keep the mixture at this temperature for 3-5 hours to prepare epoxy-modified castor oil 2 with heat resistance modification treatment.

[0046] Preparation Example 3

[0047] Epoxy-modified castor oil 3 after heat-resistant modification

[0048] First, weigh epoxy castor oil and decanediamine at a molar ratio of 1:1.5. Add the decanediamine to the epoxy castor oil at a dropping rate of 2 drops / s. Heat the mixture to 85°C at a rate of 2°C / min. During the heating process, increase the stirring speed to 400 rpm and keep the mixture at this temperature for 5 hours to prepare epoxy-modified castor oil 3 with heat resistance modification treatment.

[0049] Preparation Example 4

[0050] Self-healing microcapsules 1

[0051] Tung oil and epoxidized soybean oil were mixed in a 1:1 mass ratio, and the mixture was collected. 3% of the total mass of the core material was added to Span-80 emulsifier and stirred evenly. The mixture was then slowly dripped into deionized water and subjected to high-speed shearing to prepare an O / W type core material emulsion.

[0052] The urea-formaldehyde prepolymer and core material emulsion were mixed at a mass ratio of 0.05:0.02 and the pH was adjusted to 2.5. The mixture was heated to 80°C and stirred. After the reaction was completed, the mixture was centrifuged at 3000 r / min, washed, and dried at 45°C for 3 h to prepare self-healing microcapsules 1.

[0053] Preparation Example 5

[0054] Self-repairing microcapsules 2

[0055] Tung oil and epoxidized soybean oil were mixed in a 1:1 mass ratio, and the mixture was collected. 3% of the total mass of the core material was added to Span-80 emulsifier and stirred evenly. The mixture was then slowly dripped into deionized water and subjected to high-speed shearing to prepare an O / W type core material emulsion.

[0056] The urea-formaldehyde prepolymer and core material emulsion were mixed at a mass ratio of 1:0.5 and the pH was adjusted to 3.0. The mixture was heated to 85°C and stirred. After the reaction was completed, the mixture was centrifuged at 3000 r / min, washed, and dried at 45°C for 3 h to prepare self-healing microcapsules 2.

[0057] Preparation Example 6

[0058] Self-healing microcapsules 3

[0059] Tung oil and epoxidized soybean oil were mixed in a 1:1 mass ratio, and the mixture was collected. 3% of the total mass of the core material was added to Span-80 emulsifier and stirred evenly. The mixture was then slowly dripped into deionized water and subjected to high-speed shearing to prepare an O / W type core material emulsion.

[0060] The urea-formaldehyde prepolymer and core material emulsion were mixed at a mass ratio of 1:1 and the pH was adjusted to 3.0. The mixture was heated to 90°C and stirred. After the reaction was completed, the mixture was centrifuged at 3000 r / min, washed, and dried at 45°C for 3 h to prepare self-healing microcapsules 3.

[0061] Preparation Example 7

[0062] Poly(N-isopropylacrylamide-polycaprolactone) block copolymer 1 is prepared by mixing poly(N-isopropylacrylamide-polycaprolactone) block copolymer and poly(ethylene glycol-polylactic acid) copolymer at a mass ratio of 2:1, freeze-drying, crushing and grinding through a 200-mesh sieve.

[0063] Preparation Example 8

[0064] Poly(N-isopropylacrylamide-polycaprolactone) block copolymer 2 is prepared by mixing poly(N-isopropylacrylamide-polycaprolactone) block copolymer and poly(ethylene glycol-polylactic acid) copolymer at a mass ratio of 3:1, freeze-drying, crushing and grinding through a 200-mesh sieve.

[0065] Example 1

[0066] An environmentally friendly release agent for metal casting includes the following substances:

[0067] 30 kg of epoxy-modified castor oil (hydroxyl value ≥ 160 mg KOH / g), 15 kg of pentaerythritol stearate, and 5 kg of nanocellulose.

[0068] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0069] Epoxy-modified castor oil was selected and heated to 40°C at a rate of 2°C / min. Pentaerythritol stearate and nanocellulose were added, and the temperature was increased to 60°C at a rate of 1°C / min. The mixture was then ultrasonically dispersed at 300W for 30 min. The resulting emulsion was collected, and the environmentally friendly metal casting release agent was prepared.

[0070] Example 2

[0071] An environmentally friendly release agent for metal casting includes the following substances:

[0072] 32 kg of epoxy-modified castor oil (hydroxyl value ≥ 160 mg KOH / g), 11 kg of pentaerythritol stearate, and 6 kg of nanocellulose.

[0073] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0074] Epoxy-modified castor oil was selected and heated to 45°C at a rate of 2°C / min. Pentaerythritol stearate and nanocellulose were added, and the temperature was increased to 70°C at a rate of 1°C / min. The mixture was then ultrasonically dispersed at 300W for 30 min. The resulting emulsion was collected, and the environmentally friendly metal casting release agent was prepared.

[0075] Example 3

[0076] An environmentally friendly release agent for metal casting includes the following substances:

[0077] 35 kg of epoxy-modified castor oil (hydroxyl value ≥ 160 mg KOH / g), 20 kg of pentaerythritol stearate, and 8 kg of nanocellulose.

[0078] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0079] Epoxy-modified castor oil was selected and heated to 50°C at a rate of 3°C / min. Pentaerythritol stearate and nanocellulose were added, and the temperature was increased to 80°C at a rate of 2°C / min. The mixture was then ultrasonically dispersed at 300W for 30 min. The resulting emulsion was collected, and the environmentally friendly metal casting release agent was prepared.

[0080] Example 4

[0081] An environmentally friendly release agent for metal casting includes the following substances:

[0082] 32 kg of heat-resistant modified epoxy castor oil, 11 kg of pentaerythritol stearate, and 6 kg of nanocellulose.

[0083] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0084] Epoxy-modified castor oil 1, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Pentaerythritol stearate and nanocellulose are added, and the temperature is raised to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0085] Example 5

[0086] An environmentally friendly release agent for metal casting includes the following substances:

[0087] 32 kg of heat-resistant modified epoxy castor oil, 2 kg of pentaerythritol stearate, and 6 kg of nanocellulose.

[0088] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0089] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Pentaerythritol stearate and nanocellulose are added, and the temperature is raised to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0090] Example 6

[0091] An environmentally friendly release agent for metal casting includes the following substances:

[0092] 32 kg of heat-resistant modified epoxy castor oil, 3 kg of pentaerythritol stearate, and 6 kg of nanocellulose.

[0093] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0094] Epoxy-modified castor oil 3, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0095] Example 7

[0096] An environmentally friendly release agent for metal casting includes the following substances:

[0097] 32 kg of heat-resistant modified epoxy castor oil, 11 kg of pentaerythritol stearate, 6 kg of nanocellulose, and 10 kg of self-healing microcapsules.

[0098] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0099] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Self-healing microcapsules 1, pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0100] Example 8

[0101] An environmentally friendly release agent for metal casting includes the following substances:

[0102] 32 kg of heat-resistant modified epoxy castor oil, 11 kg of pentaerythritol stearate, 6 kg of nanocellulose, and 12 kg of self-healing microcapsules.

[0103] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0104] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Self-healing microcapsules 2, pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0105] Example 9

[0106] An environmentally friendly release agent for metal casting includes the following substances:

[0107] 32kg of heat-resistant modified epoxy castor oil, 11kg of pentaerythritol stearate, 6kg of nanocellulose, and 15kg of self-healing microcapsules.

[0108] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0109] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Self-healing microcapsules 3, pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min, and the emulsion is collected to prepare the environmentally friendly metal casting release agent.

[0110] Example 10

[0111] An environmentally friendly release agent for metal casting includes the following substances:

[0112] 32 kg of heat-resistant modified epoxy castor oil 2, 11 kg of pentaerythritol stearate, 6 kg of nanocellulose, 12 kg of self-healing microcapsules 2 and 15 kg of poly(N-isopropylacrylamide-polycaprolactone block copolymer 1.

[0113] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0114] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Self-healing microcapsules 2, pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0115] Example 11

[0116] An environmentally friendly release agent for metal casting includes the following substances:

[0117] 32 kg of heat-resistant modified epoxy castor oil 2, 11 kg of pentaerythritol stearate, 6 kg of nanocellulose, 12 kg of self-healing microcapsules 2 and 20 kg of poly(N-isopropylacrylamide-polycaprolactone block copolymer 2.

[0118] A method for preparing an environmentally friendly release agent for metal casting includes the following steps:

[0119] Epoxy-modified castor oil 2, which has undergone heat resistance modification, is heated to 45°C at a rate of 2°C / min. Self-healing microcapsules 2, pentaerythritol stearate and nanocellulose are added, and the temperature is increased to 70°C at a rate of 1°C / min. The mixture is then ultrasonically dispersed at 300W for 30 min. The resulting emulsion is collected, and the environmentally friendly metal casting release agent can be prepared.

[0120] Comparative Example 1

[0121] Compared with Example 1, Comparative Example 1 used castor oil of equal mass instead of epoxy-modified castor oil, and the remaining preparation steps and parameters were the same as in Example 1.

[0122] Performance testing

[0123] Thermal decomposition temperature: The 5% weight loss temperature was determined by thermogravimetric analysis (TGA).

[0124] Demolding force: Simulates the aluminum alloy die casting process to determine the force required for the casting to separate from the mold.

[0125] Self-healing efficiency: The rate of recovery of the friction coefficient after 24 hours of repair following a scratch (50 μm) on the film layer.

[0126] High-temperature residue: the mass fraction of residue after heating at 250℃ for 2 hours.

[0127] The results are shown in Table 1 below:

[0128] Table 1 Performance Test Table

[0129]

[0130]

[0131] By comparing the test results of Examples 1-3 and Comparative Example 1 with those in Table 1, it can be found that:

[0132] By comparing Examples 1-3 and Comparative Example 1, it is further illustrated that the technical solution of this application utilizes epoxy-modified castor oil molecules to form a cross-linked network with epoxy groups and hydroxyl groups, endowing the film layer with good flexibility and adhesion. Pentaerythritol stearate serves as a lubricant, forming an oriented adsorption layer on the metal surface through long-chain fatty acid segments, reducing the interfacial tension between the casting and the mold. Nanocellulose constructs a physical support framework in the film layer through a nanoscale fibrous structure, enhancing the mechanical strength and high-temperature resistance of the film layer. Through the synergistic effect of these three components, the system achieves a balance between environmental friendliness and functionality: bio-based materials reduce the environmental accumulation risks of traditional petroleum-based components, while the combination of lubricating components and reinforcing phases ensures that the film layer is not easily damaged during demolding, effectively avoiding surface adhesion and defects in the casting, and improving casting efficiency.

[0133] By comparing Examples 4-6 with Examples 1-3, it is evident that the heat-resistant modification treatment of epoxy-modified castor oil in this application further optimizes the high-temperature stability of the film-forming matrix. The modified film-forming matrix is ​​less prone to thermal oxidative degradation in the high-temperature environment of the casting process, maintaining the integrity of the film structure. This avoids the carbide residues caused by the high-temperature decomposition of traditional release agents, thus extending the effective action time of the release agent and reducing the difficulty of cleaning the casting surface.

[0134] By comparing Examples 7-9 and Examples 4-6, it is illustrated that the technical solution of this application introduces self-healing microcapsules, endowing the release agent with dynamic damage repair capabilities. Through self-repair, the integrity of the release agent is restored, reducing casting adhesion problems caused by film layer damage, extending the single-use lifespan of the release agent, and reducing the frequency of recoating. This is particularly suitable for complex cavity castings or long-cycle casting processes.

[0135] By comparing Examples 10-11 with Examples 7-9, it can be seen that the technical solution of this application achieves the following effect through the synergistic action of poly(N-isopropylacrylamide)-polycaprolactone block copolymer and polyethylene glycol-polylactic acid copolymer: when the ambient temperature is higher than its lower critical solution temperature, the chain segments change from hydrophilic to hydrophobic and shrink; the polycaprolactone chain segments provide flexibility and crystallinity at low temperatures, thereby improving low-temperature viscosity; the PEG chain segments in the polyethylene glycol-polylactic acid copolymer have hydrophilicity and lubricity, while the PLA chain segments enhance compatibility with bio-based film-forming matrices.

[0136] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0137] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0138] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0139] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. An environmentally friendly release agent for metal casting, characterized in that, Includes the following substances in parts by weight: 30-35 parts of bio-based film-forming substrate; 15-20 parts of pentaerythritol stearate; 5-8 parts of nanocellulose; The bio-based film-forming matrix includes epoxy-modified castor oil.

2. The environmentally friendly release agent for metal casting according to claim 1, characterized in that, The epoxy-modified castor oil is epoxy-modified castor oil that has undergone heat-resistant modification treatment, and the heat-resistant modification treatment adopts the following technical solution. Under nitrogen protection, epoxy castor oil and bio-based diamine monomer are mixed at a molar ratio of 1:1-1.5 and reacted at 75-85℃ for 3-5 hours to prepare heat-resistant modified epoxy castor oil.

3. The environmentally friendly release agent for metal casting according to claim 1, characterized in that, The bio-based diamine monomer is sebacdiamine.

4. The environmentally friendly release agent for metal casting according to claim 1, characterized in that, The environmentally friendly metal casting release agent also includes 10-15 parts by weight of self-healing microcapsules, wherein the self-healing microcapsules comprise a core material of tung oil-epoxidized soybean oil and a wall material of urea-formaldehyde resin.

5. The environmentally friendly release agent for metal casting according to claim 1, characterized in that, The environmentally friendly metal casting release agent also includes 15-20 parts by weight of an adaptive temperature-modifying material.

6. The environmentally friendly release agent for metal casting according to claim 5, characterized in that, The adaptive temperature-modified materials include poly(N-isopropylacrylamide)-polycaprolactone block copolymer and polyethylene glycol-polylactic acid copolymer mixed in a mass ratio of (2-3):

1.

7. The environmentally friendly release agent for metal casting according to claim 4, characterized in that, The self-healing microcapsules are manufactured using the following technical solution: Weigh out formaldehyde aqueous solution and urea according to the molar ratio of urea to formaldehyde 1:1-2. Place the formaldehyde aqueous solution in a reaction vessel, adjust the pH, add urea, heat and keep warm to react, and obtain urea-formaldehyde prepolymer. Tung oil and epoxidized soybean oil were mixed in a 1:1 mass ratio, and the mixture was collected. 3% of the total mass of the core material was added to Span-80 emulsifier and stirred evenly. The mixture was then slowly dripped into deionized water and subjected to high-speed shearing to prepare an O / W type core material emulsion. The urea-formaldehyde prepolymer and core material emulsion were stirred and mixed, and the pH was adjusted to 2.5-3.

0. The mixture was heated and stirred, and after the reaction was completed, it was centrifuged, washed and dried to prepare self-healing microcapsules.

8. A method for preparing an environmentally friendly metal casting release agent according to any one of claims 1-6, characterized in that, The preparation steps include the following: After selecting a bio-based film-forming substrate and heating it once, add an adaptive temperature-modifying material and stir to mix. Then add self-healing microcapsules, pentaerythritol stearate and nanocellulose. After heating a second time and ultrasonically dispersing and collecting the emulsion, the environmentally friendly metal casting release agent can be prepared.

9. The method for preparing an environmentally friendly metal casting release agent according to claim 8, characterized in that, The first heating process involves raising the temperature to 40-50°C at a rate of 2-3°C / min.

10. The method for preparing an environmentally friendly metal casting release agent according to claim 7, characterized in that, The secondary heating process involves raising the temperature to 60-80℃ at a rate of 1-2℃ / min.

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