Low-temperature-resistant anti-corrosion evaporator fin and preparation method thereof

Abstract

The invention discloses a low-temperature-resistant anti-corrosion evaporator fin and a preparation method thereof, and relates to the field of fin processing, an evaporator aluminum foil fin is coated with a functional coating, and the functional coating is formed by reacting and curing a coating slurry agent and a curing agent according to the mass ratio of 2: 1. The coating comprises polyaspartic acid ester, polyether amine, amino organic silicon resin and polyether graft modified boron nitride filler. The curing agent is a prepolymer with a branched structure, and the prepolymer is prepared by carrying out co-modification on isophorone diisocyanate and dicyclohexylmethane diisocyanate by adopting trimethylolpropane and polytetrahydrofuran polyol. Through systematic modification and compounding of the curing agent, the filler and the functional resin, the fin still keeps the tensile strength retention rate of 90% or above at low temperature, passes a neutral salt spray test for 900 hours, has excellent low-temperature toughness, wear resistance and long-acting corrosion resistance, and is suitable for a refrigeration equipment evaporator under a low-temperature working condition.

Description

Technical Field

[0001] This invention relates to the field of fin processing, specifically to a low-temperature resistant and corrosion-resistant evaporator fin and its preparation method. Background Technology

[0002] As a core heat exchange element in a refrigeration system, the performance of evaporator fins directly affects the energy efficiency and operational reliability of the equipment. In harsh low-temperature and high-humidity conditions such as in cold storage, cold chain logistics, and quick-freezing equipment, traditional fins face multiple failure challenges: First, the continuous condensation on the fin surface combines with corrosive components in the air, causing severe electrochemical corrosion of the aluminum material, leading to pitting and perforation, shortening its service life, and contaminating the refrigerant system. Second, the low-temperature environment greatly exacerbates the tendency for frost to form on the fin surface. Thick frost layers can clog air ducts, drastically increasing air resistance and energy consumption, forcing frequent defrosting, resulting in temperature fluctuations and energy waste. Furthermore, conventional organic protective coatings are prone to embrittlement, cracking, and peeling under the thermal stress caused by periodic large-scale temperature changes due to a mismatch in the coefficient of thermal expansion with the metal substrate, thus losing their protective function.

[0003] Currently, technologies for improving fin performance mostly focus on single-function improvements: for example, using hydrophilic coatings to promote drainage, but this accelerates frost formation at low temperatures; applying conventional epoxy or fluorocarbon anti-corrosion coatings, which lack flexibility and are prone to brittleness at low temperatures; or directly using corrosion-resistant materials such as stainless steel, which are costly and have lower processability and thermal conductivity than aluminum alloys. Although some studies have attempted to use high-performance resins such as polyaspartic acid esters for corrosion protection, ordinary formulations still have shortcomings in terms of extremely low temperature toughness, filler interface compatibility, and long-term adhesion to aluminum substrates, making it difficult to meet the combined requirements of evaporator fins for long-term corrosion protection, frost suppression and extension, high and low temperature cycle tolerance, and excellent adhesion.

[0004] To address the above problems, this invention provides a low-temperature resistant and corrosion-resistant evaporator fin and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature resistant and corrosion-resistant evaporator fin and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing low-temperature resistant and corrosion-resistant evaporator fins includes the following steps: Step 1: Preparation of coating slurry: Polyaspartic acid ester, polyetheramine, and amino silicone resin were added sequentially. Under stirring, polyether-grafted modified boron nitride powder, wetting and dispersing agent, leveling agent, defoamer, ultraviolet absorber, and light stabilizer were added sequentially. After the addition was completed, the dispersion was accelerated. The slurry was circulated and ground. The slurry was then filtered to obtain the coating slurry. Step 2: Preparation of Low-Temperature Resistant and Corrosion-Resistant Evaporator Fins After mixing the modified curing agent and the coating slurry according to the mass ratio, the mixture is sprayed onto the aluminum foil fins, dried and cured to obtain low-temperature resistant and corrosion-resistant evaporator fins.

[0007] Furthermore, the coating adhesive comprises the following components, by weight percentage: 10wt%-15wt% polyetheramine, 5wt%-10wt% amino silicone resin, 4wt%-5wt% polyether grafted modified boron nitride powder, 1wt%-1.5wt% wetting and dispersing agent, 1wt%-1.5wt% leveling agent, 1wt%-1.5wt% defoamer, 0.5wt%-1wt% ultraviolet absorber, 0.5wt%-1wt% light stabilizer, and the balance being polyaspartic acid ester.

[0008] Furthermore, the preparation process of the modified curing agent is as follows: the isocyanate prepolymer and the mixed solvent are mixed, stirred evenly, and then filtered to obtain the modified curing agent. The mixed solvent is a mixture of xylene and butyl acetate, wherein the mass ratio of xylene to butyl acetate is 7:3.

[0009] Furthermore, the preparation process of the isocyanate prepolymer is as follows: trimethylolpropane and polytetrahydrofuran polyol are heated to 80-100℃ under stirring and dehydrated under vacuum for 1-2 hours; cooled to 40-50℃, a catalyst is added, and then isophorone diisocyanate and dicyclohexylmethane diisocyanate are premixed and slowly added dropwise; after the dropwise addition is complete, the temperature is raised to 80℃ and kept at that temperature for 4-6 hours, cooled, diluted with xylene, stirred, and filtered to obtain the modified isocyanate prepolymer.

[0010] Furthermore, the preparation process of the polyether-grafted modified boron nitride powder is as follows: hydroxylated boron nitride is dispersed in anhydrous xylene, and isophorone diisocyanate and catalyst are added under nitrogen protection and stirring. The temperature is raised to 70-80℃ and the reaction is carried out for 5-6 hours. While maintaining the nitrogen atmosphere and stirring, polytetrahydrofuran polyol is added dropwise, and the reaction is continued at 60℃ for 3-4 hours. After cooling and centrifugation, the mixture is vacuum dried at 60℃ for 10-12 hours, ground, and sieved to obtain polyether-grafted modified boron nitride powder.

[0011] Furthermore, the preparation process of the hydroxylated boron nitride is as follows: weigh the flake boron nitride, add a 10wt% nitric acid solution, heat and reflux in an oil bath at 60-80℃ for 4-5 hours, after the reaction is completed, cool, centrifuge, wash, and vacuum dry at 80℃ for 10-12 hours to obtain hydroxylated boron nitride.

[0012] Furthermore, the preparation process of the amino organosilicon resin is as follows: silane coupling agent and isopropanol are stirred evenly; ethylenediamine and dibutyltin dilaurate are mixed evenly and added dropwise, maintaining the reaction temperature at 60-70℃; after the dropwise addition is completed, the temperature is raised to 80-90℃, and the reflux reaction is started for 4-5 hours; after the reaction is completed, the mixture is distilled under reduced pressure and filtered to obtain the amino organosilicon resin.

[0013] Furthermore, the parameters for the vacuum distillation are: distillation at 0.85-0.95 MPa and 85-90 °C for 1-2 hours.

[0014] Furthermore, the mass ratio of isophorone diisocyanate to dicyclohexylmethane diisocyanate is 7:(2-3).

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. A modified isocyanate curing agent with a branched long-chain structure was designed and synthesized, effectively improving the internal stress distribution and mechanical properties of the coating at low temperatures. Trimethylolpropane was used as the branching point, and it was used in conjunction with a long-chain polyether polyol to modify the alicyclic isocyanate. This structure introduces a large number of flexible ether segments into the cured coating. These flexible segments can absorb and dissipate the micro-stress caused by low temperatures, while the moderate branching structure provides crosslinking strength while avoiding increased brittleness due to excessive crosslinking density. This design allows the polymer segments of the coating to maintain a certain degree of mobility when subjected to low temperatures, thereby significantly delaying the rise in glass transition temperature and giving the coating more durable low-temperature flexibility and impact resistance, resulting in superior low-temperature performance and corrosion resistance for the fins.

[0016] 2. By performing surface grafting chemical modification on boron nitride filler, the issues of dispersion stability and interfacial bonding in the organic resin matrix were resolved, synergistically improving the wear resistance and structural density of the coating. Utilizing the bridging effect of isocyanate, long polyether chains with a chemical structure similar to the resin matrix were covalently grafted onto the boron nitride surface. The ends of these grafted chains can participate in the resin curing and cross-linking reaction, transforming the originally physically doped inorganic filler into chemical bonds. This strong interfacial bonding allows stress to be efficiently transferred from the relatively flexible resin matrix to the boron nitride, thereby improving the wear resistance of the coating. Furthermore, the reduced porosity between the filler and the matrix enhances the overall density of the coating, further strengthening the corrosion resistance of the fins.

[0017] 3. A self-made amino silicone resin was used as a functional component, which optimized the crosslinking network structure and surface properties of the coating. The amino silicone resin was synthesized through the ring-opening reaction of epoxy silanes and amines. This resin has two functions in the curing system: the silicone segments impart low surface energy to the coating, which helps to improve hydrophobicity; while the active amino groups at its ends can react with isocyanate curing agents, improving the compatibility between structures, making the coating performance more stable, and improving the low-temperature resistance and corrosion resistance of the fins. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and all described quantities are by weight. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The sources and types of substances involved in this invention are not particularly limited. Exemplary examples include the following raw materials: polyaspartic acid ester: product number: F420, which can be purchased from Shenzhen Feiyang Junyan New Materials Co., Ltd.; polyetheramine: product number: D2000, which can be purchased from BASF AG; polytetrahydrofuran polyol: PTG-1000, which can be purchased from BASF AG; and flake boron nitride: product number: BSL-BN-1, which can be purchased from Beasley New Materials (Suzhou) Co., Ltd. Example

[0020] Step 1: Preparation of Modified Curing Agent In a reactor, 2g of trimethylolpropane and 40g of polytetrahydrofuran polyol were added. The mixture was heated to 80°C with stirring at 150 rpm and then dehydrated under vacuum for 1 hour until no water was distilled off. The mixture was then cooled to 40°C, and 0.1g of dibutyltin dilaurate catalyst was added. Then, 24.2g of isophorone diisocyanate and 10.4g of dicyclohexylmethane diisocyanate were slowly added dropwise to the reactor. After the addition was complete, the temperature was increased to 80°C at a rate of 5°C / min and maintained at this temperature for 6 hours with stirring at 200 rpm. After the reaction was completed, the mixture was cooled, diluted with 5mL of xylene, stirred, and filtered to obtain the modified isocyanate prepolymer. Mix 12g of isocyanate prepolymer and 6g of mixed solvent, stir well and filter to obtain the modified curing agent. The mixed solvent is a mixture of xylene and butyl acetate, with a mass ratio of xylene to butyl acetate of 7:3. Step 2: Preparation of polyether-grafted modified boron nitride powder Weigh 10g of flake boron nitride and place it in a 250mL round-bottom flask. Add 100mL of 10wt% nitric acid solution and heat under reflux in an oil bath at 60℃ for 4h. After the reaction is complete, cool, centrifuge, wash, and vacuum dry at 80℃ for 10h to obtain hydroxylated boron nitride. Hydroxylated boron nitride was dispersed in 200 mL of anhydrous xylene and placed in a three-necked flask. Under nitrogen protection and magnetic stirring at 300 r / min, 7 g of isophorone diisocyanate and 0.5 g of dibutyltin dilaurate catalyst were added. The oil bath temperature was raised to 70 °C and the reaction was carried out for 5 h. While maintaining the nitrogen atmosphere and stirring, 15 g of polytetrahydrofuran polyol was added dropwise, and the reaction was continued at 60 °C for 3 h. After cooling and centrifugation, the mixture was vacuum dried at 60 °C for 10 h, ground, and sieved to obtain polyether-grafted modified boron nitride powder. Step 3: Preparation of amino silicone resin: Add 100g of γ-glycidyl etheroxypropyltrimethoxysilane and 150g of isopropanol to a dry 500mL four-necked flask, and stir at 200r / min until KH-560 is completely dissolved. Mix 18g of ethylenediamine and 0.10g of dibutyltin dilaurate in a beaker, and add the mixture dropwise to the four-necked flask, maintaining the reaction temperature at 60℃. After the addition is complete, raise the oil bath temperature to 80℃ and start reflux reaction for 4h. After the reaction is completed, distill under reduced pressure at 0.85MPa and 85℃ for 1h, filter, and obtain amino organosilicon resin. Step 4: Preparation of coating slurry: Take polyaspartic acid ester, polyetheramine, and amino silicone resin. While stirring at 500 rpm, sequentially add polyether-grafted modified boron nitride powder, wet dispersant BYK-104S, leveling agent BYK-378, defoamer BYK-066N, ultraviolet absorber UV-1130, and light stabilizer UV-770. After the addition is complete, increase the stirring speed to 1500 rpm and disperse at high speed for 20 minutes until the slurry is initially homogeneous. Transfer the slurry to a sand... In the mill, 0.8mm zirconia beads are used as the grinding media for grinding; the coating slurry is obtained by filtering with a 200-mesh filter; the composition of the coating slurry is as follows, by mass percentage: 10wt% polyetheramine, 5wt% amino silicone resin, 4wt% polyether grafted modified boron nitride powder, 1wt% wetting and dispersing agent, 1wt% leveling agent, 1wt% defoamer, 0.5wt% ultraviolet absorber, 0.5wt% light stabilizer, and the balance is polyaspartic acid ester.

[0021] Step 5: Preparation of Low-Temperature Resistant and Corrosion-Resistant Evaporator Fins The modified curing agent and coating slurry were mixed at a mass ratio of 1:2 and then sprayed onto aluminum foil fins to a thickness of 30µm. After drying and curing, low-temperature resistant and corrosion-resistant evaporator fins were obtained. Example

[0022] Step 1: Preparation of Modified Curing Agent In a reactor, 2g of trimethylolpropane and polytetrahydrofuran polyol were added. The mixture was heated to 90°C with stirring at 150 rpm and then dehydrated under vacuum for 1.5 h until no water was distilled off. The mixture was then cooled to 45°C, and 0.1g of dibutyltin dilaurate catalyst was added. Then, 24.2g of isophorone diisocyanate and 10.4g of dicyclohexylmethane diisocyanate were slowly added dropwise to the reactor. After the addition was complete, the temperature was increased to 80°C at a rate of 5°C / min and maintained at this temperature for 6 h with stirring at 200 rpm. After the reaction was completed, the mixture was cooled, diluted with 5mL of xylene, stirred, and filtered to obtain the modified isocyanate prepolymer. Mix 12g of isocyanate prepolymer and 6g of mixed solvent, stir well and filter to obtain the modified curing agent. The mixed solvent is a mixture of xylene and butyl acetate, with a mass ratio of xylene to butyl acetate of 7:3. Step 2: Preparation of polyether-grafted modified boron nitride powder Weigh 10g of boron nitride flakes and place them in a 250mL round-bottom flask. Add 100mL of 10wt% nitric acid solution and heat under reflux in an oil bath at 70℃ for 4.5h. After the reaction is complete, cool, centrifuge, wash, and vacuum dry at 80℃ for 11h to obtain hydroxylated boron nitride. Hydroxylated boron nitride was dispersed in 200 mL of anhydrous xylene and placed in a three-necked flask. Under nitrogen protection and magnetic stirring at 300 r / min, 7 g of isophorone diisocyanate and 0.5 g of dibutyltin dilaurate catalyst were added. The oil bath temperature was raised to 75 °C and the reaction was carried out for 5.5 h. While maintaining the nitrogen atmosphere and stirring, 15 g of polytetrahydrofuran polyol was added dropwise, and the reaction was continued at 60 °C for 3.5 h. After cooling and centrifugation, the mixture was vacuum dried at 60 °C for 11 h, ground, and sieved to obtain polyether-grafted modified boron nitride powder. Step 3: Preparation of amino silicone resin: Add 100g of γ-glycidyl etheroxypropyltrimethoxysilane and 150g of isopropanol to a dry 500mL four-necked flask, and stir at 250r / min until KH-560 is completely dissolved. Mix 18g of ethylenediamine and 0.1g of dibutyltin dilaurate in a beaker, and add the mixture dropwise to the four-necked flask, maintaining the reaction temperature at 60-70℃. After the addition is complete, raise the oil bath temperature to 85℃ and begin reflux reaction for 4.5h. After the reaction is complete, distill under reduced pressure at 0.9MPa and 88℃ for 1.5h, filter, and obtain amino organosilicon resin. Step 4: Preparation of coating slurry: Take polyaspartic acid ester, polyetheramine, and amino silicone resin. While stirring at 500 rpm, sequentially add polyether-grafted modified boron nitride powder, wet dispersant BYK-104S, leveling agent BYK-378, defoamer BYK-066N, ultraviolet absorber UV-1130, and light stabilizer UV-770. After the addition is complete, increase the stirring speed to 1500 rpm and disperse at high speed for 20 minutes until the slurry is initially homogeneous. Transfer the slurry to a sand mill. Grinding was performed using 1.0 mm zirconia beads as the grinding media; the coating slurry was obtained by filtering through a 200-mesh filter; the components of the coating slurry, by mass percentage, are: 12 wt% polyetheramine, 8 wt% amino silicone resin, 4.5 wt% polyether-grafted modified boron nitride powder, 1.2 wt% wetting and dispersing agent, 1.2 wt% leveling agent, 1.2 wt% defoamer, 0.8 wt% ultraviolet absorber, 0.8 wt% light stabilizer, and the balance being polyaspartic acid ester; Step 5: Preparation of Low-Temperature Resistant and Corrosion-Resistant Evaporator Fins The modified curing agent and coating slurry were mixed at a mass ratio of 1:2 and then sprayed onto aluminum foil fins to a thickness of 35µm. After drying and curing, low-temperature resistant and corrosion-resistant evaporator fins were obtained. Example

[0023] Step 1: Preparation of Modified Curing Agent In a reactor, 2g of trimethylolpropane and polytetrahydrofuran polyol PTG-1000 were added. The mixture was heated to 100℃ and vacuum-dehydrated for 2 hours with stirring at 150 rpm until no water was distilled off. The mixture was then cooled to 50℃, and 0.1g of dibutyltin dilaurate catalyst was added. Isophorone diisocyanate and dicyclohexylmethane diisocyanate were pre-mixed at a mass ratio of 70:30 and slowly added dropwise to the reactor. After the addition was complete, the temperature was increased to 80℃ at a rate of 5℃ / min and maintained at this temperature for 6 hours with stirring at 200 rpm. After the reaction was completed, the mixture was cooled, diluted with 5mL of xylene, stirred, and filtered to obtain the modified isocyanate prepolymer. Mix 12g of isocyanate prepolymer and 6g of mixed solvent, stir well and filter to obtain the modified curing agent. The mixed solvent is a mixture of xylene and butyl acetate, with a mass ratio of xylene to butyl acetate of 7:3. Step 2: Preparation of polyether-grafted modified boron nitride powder Weigh 10g of boron nitride flakes and place them in a 250mL round-bottom flask. Add 100mL of 10wt% nitric acid solution and heat under reflux in an oil bath at 80℃ for 5h. After the reaction is complete, cool, centrifuge, wash, and vacuum dry at 80℃ for 12h to obtain hydroxylated boron nitride. Hydroxylated boron nitride was dispersed in 200 mL of anhydrous xylene and placed in a three-necked flask. Under nitrogen protection and magnetic stirring at 300 r / min, 7 g of isophorone diisocyanate and 0.5 g of dibutyltin dilaurate catalyst were added. The oil bath temperature was raised to 80 °C and the reaction was carried out for 6 h. While maintaining the nitrogen atmosphere and stirring, 15 g of polytetrahydrofuran polyol was added dropwise, and the reaction was continued at 60 °C for 4 h. After cooling and centrifugation, the mixture was vacuum dried at 60 °C for 12 h, ground, and sieved to obtain polyether-grafted modified boron nitride powder. Step 3: Preparation of amino silicone resin: Add 100g of γ-glycidyl etheroxypropyltrimethoxysilane and 150g of isopropanol to a dry 500mL four-necked flask, and stir at 300r / min until KH-560 is completely dissolved. Mix 18g of ethylenediamine and 0.1g of dibutyltin dilaurate in a beaker, and add the mixture dropwise to the four-necked flask, maintaining the reaction temperature at 70℃. After the addition is complete, raise the oil bath temperature to 90℃ and begin reflux reaction for 5h. After the reaction is complete, distill under reduced pressure at 0.95MPa and 90℃ for 2h, filter, and obtain amino organosilicon resin. Step 4: Preparation of coating slurry: Take polyaspartic acid ester, polyetheramine, and amino silicone resin. While stirring at 500 rpm, sequentially add polyether-grafted modified boron nitride powder, wet dispersant BYK-104S, leveling agent BYK-378, defoamer BYK-066N, ultraviolet absorber UV-1130, and light stabilizer UV-770. After the addition is complete, increase the stirring speed to 1500 rpm and disperse at high speed for 20 minutes until the slurry is initially homogeneous. Transfer the slurry to a sand mill. In the machine, 1.2mm zirconia beads are used as the grinding media for grinding; the coating slurry is obtained by filtering with a 200-mesh filter; the composition of the coating slurry is as follows, by mass percentage: 15wt% polyetheramine, 10wt% amino silicone resin, 5wt% polyether grafted modified boron nitride powder, 1.5wt% wetting and dispersing agent, 1.5wt% leveling agent, 1.5wt% defoamer, 1wt% ultraviolet absorber, 1wt% light stabilizer, and the balance is polyaspartic acid ester; Step 5: Preparation of Low-Temperature Resistant and Corrosion-Resistant Evaporator Fins The modified curing agent and coating slurry were mixed at a mass ratio of 1:2 and then sprayed onto aluminum foil fins to a thickness of 40µm. After drying and curing, low-temperature resistant and corrosion-resistant evaporator fins were obtained.

[0024] Comparative Example 1: No amino silicone resin was used; ordinary silicone resin was used directly, and the rest was the same as in Example 1.

[0025] Comparative Example 2: No modification was made to boron nitride, and the rest was the same as in Example 1.

[0026] Comparative Example 3: No modification was made to the isocyanate curing agent; otherwise, it was the same as in Example 1.

[0027] experiment: (1) The modified curing agent and coating slurry prepared in Example 1 and Comparative Example 1 were mixed at a mass ratio of 1:2 and then sprayed onto a tinplate with dimensions of 50mm×120mm×0.3mm for impact strength testing. The test was conducted in accordance with GB / T1732-93, and the data obtained are shown in Table 1 below:

[0028] (2) The corrosion resistance of the evaporator fins prepared in Examples 1-3 and Comparative Examples 1-3 was tested using the international standard ISO9227:2012 with reference to the international standard ISO9227:2012. The salt solution was a sodium chloride solution with a mass percentage of 5%. The time for rust to appear in the salt spray was recorded. The data obtained are shown in Table 2 below:

[0029] Conclusion: The data above demonstrates that the low-temperature corrosion-resistant evaporator fins prepared by this invention possess excellent comprehensive performance. The coating exhibits high impact strength and maintains over 90% tensile strength retention even at -15℃, indicating that the coating system combines good room-temperature mechanical properties with excellent low-temperature toughness. The neutral salt spray resistance exceeds 950 hours, demonstrating that the fin coating prepared by this invention has long-lasting and reliable corrosion protection. In summary, the low-temperature corrosion-resistant evaporator fins prepared by this invention exhibit balanced and excellent mechanical properties and protective durability.

[0030] In Comparative Example 1, instead of using the self-made amino silicone resin, ordinary silicone resin was used, and the fin coating did not contain any amino silicone components that could participate in crosslinking. Compared to Example 1, the impact strength and salt spray resistance of the coating both decreased. This indicates that the self-made amino silicone resin, through its active amino groups participating in crosslinking, can effectively enhance the density of the coating network, thereby improving the mechanical strength and long-term corrosion resistance of the coating.

[0031] In Comparative Example 2, the boron nitride filler was not modified with polyether grafting; the coating used untreated ordinary boron nitride. Compared to Example 1, the tensile strength and salt spray resistance of the coating decreased significantly, and the low-temperature toughness also decreased significantly. This indicates that polyether long-link grafting of boron nitride using isocyanate bridging technology can solve the problems of its dispersion and interfacial compatibility in the resin, which is the key to simultaneously improving the mechanical properties and corrosion protection of the coating.

[0032] In Comparative Example 3, the isocyanate curing agent was not modified with a branched structure. Compared to Example 1, the low-temperature tensile strength retention rate of its coating decreased sharply, although the room-temperature strength may be similar. This indicates that the modified isocyanate curing agent with a branched long-chain structure can introduce the necessary flexibility into the coating network, ensuring that the coating does not undergo brittle cracking and maintains good toughness under harsh low-temperature conditions.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing low-temperature resistant and corrosion-resistant evaporator fins, characterized in that: Includes the following steps: Step 1: Preparation of coating slurry: Add polyaspartic acid ester, polyetheramine, and amino silicone resin in sequence; while stirring, add polyether grafted modified boron nitride powder, wetting and dispersing agent, leveling agent, defoamer, ultraviolet absorber, and light stabilizer in sequence. After the addition is complete, accelerate the dispersion. The slurry is circulated and ground; then filtered to obtain the coating slurry. Step 2: Preparation of Low-Temperature Resistant and Corrosion-Resistant Evaporator Fins After mixing the modified curing agent and the coating slurry according to the mass ratio, the mixture is sprayed onto the aluminum foil fins, dried and cured to obtain low-temperature resistant and corrosion-resistant evaporator fins.

2. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 1, characterized in that: The coating adhesive comprises the following components, by weight percentage: 10wt%-15wt% polyetheramine, 5wt%-10wt% amino silicone resin, 4wt%-5wt% polyether grafted modified boron nitride powder, 1wt%-1.5wt% wetting and dispersing agent, 1wt%-1.5wt% leveling agent, 1wt%-1.5wt% defoamer, 0.5wt%-1wt% ultraviolet absorber, 0.5wt%-1wt% light stabilizer, and the balance being polyaspartic acid ester.

3. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 1, characterized in that: The modified curing agent is prepared by mixing isocyanate prepolymer and mixed solvent, stirring evenly and then filtering to obtain the modified curing agent. The mixed solvent is a mixture of xylene and butyl acetate, wherein the mass ratio of xylene to butyl acetate is 7:

3.

4. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 3, characterized in that: The preparation process of the isocyanate prepolymer is as follows: Trimethylolpropane and polytetrahydrofuran polyol are heated to 80-100℃ under stirring and dehydrated under vacuum for 1-2 hours; cooled to 40-50℃, a catalyst is added, and then isophorone diisocyanate and dicyclohexylmethane diisocyanate are premixed and slowly added dropwise; after the addition is complete, the temperature is raised to 80℃ and kept at that temperature for 4-6 hours, cooled, diluted with xylene, stirred, and filtered to obtain the modified isocyanate prepolymer.

5. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 1, characterized in that: The preparation process of the polyether-grafted modified boron nitride powder is as follows: hydroxylated boron nitride is dispersed in anhydrous xylene, and isophorone diisocyanate and catalyst are added under nitrogen protection and stirring. The temperature is raised to 70-80℃ and the reaction is carried out for 5-6 hours. While maintaining the nitrogen atmosphere and stirring, polytetrahydrofuran polyol is added dropwise, and the reaction is continued at 60℃ for 3-4 hours. After cooling and centrifugation, the mixture is vacuum dried at 60℃ for 10-12 hours, ground, and sieved to obtain polyether-grafted modified boron nitride powder.

6. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 5, characterized in that: The preparation process of the hydroxylated boron nitride is as follows: weigh the flake boron nitride, add a 10wt% nitric acid solution, heat and reflux in an oil bath at 60-80℃ for 4-5 hours, after the reaction is completed, cool, centrifuge, wash, and vacuum dry at 80℃ for 10-12 hours to obtain hydroxylated boron nitride.

7. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 1, characterized in that: The preparation process of the amino organosilicon resin is as follows: silane coupling agent and isopropanol are stirred evenly; ethylenediamine and dibutyltin dilaurate are mixed evenly and added dropwise, maintaining the reaction temperature at 60-70℃; after the addition is completed, the temperature is raised to 80-90℃ and reflux reaction is started for 4-5 hours; after the reaction is completed, the mixture is distilled under reduced pressure and filtered to obtain the amino organosilicon resin.

8. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 7, characterized in that: The parameters for vacuum distillation are: 0.85-0.95 MPa, 85-90 °C, distillation for 1-2 hours.

9. The method for preparing low-temperature resistant and corrosion-resistant evaporator fins according to claim 4, characterized in that: The mass ratio of isophorone diisocyanate to dicyclohexylmethane diisocyanate is 7:(2-3).

10. The low-temperature corrosion resistant evaporator fins prepared by the method according to any one of claims 1-9.

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