Self-healing polyurethane resin and method for preparing a coating thereof

Abstract

The present disclosure provides a self-healing polyurethane resin and a preparation method thereof. The preparation method of the self-healing polyurethane resin coating comprises the following steps: polytetrahydrofuran is placed in a three-necked flask, heated to remove water and kept in an oxygen-free environment; a certain amount of isophorone diisocyanate and a catalyst dibutyltin dilaurate, anhydrous tetrahydrofuran are added into the system and reacted at this temperature; the system is cooled and 1,4-butanediol or bis(2-hydroxyethyl)disulfide, anhydrous tetrahydrofuran are added into the system for reaction; after the reaction is completed, the system is immediately cooled, more than solvent is spun off by rotary evaporation, the product is coated on the surface of a substrate and solidified to form a coating. The obtained coating has high self-healing ability, long healing life, low curing temperature, and excellent mechanical properties and corrosion and stain resistance.

Description

Technical Field

[0001] This disclosure relates to the fields of marine corrosion, marine biofouling adhesion and protection, specifically to the fields of organic synthesis, resins, and coatings, and more specifically to the preparation method of self-healing polyurethane resins and their coatings. Background Technology

[0002] With the rapid development of marine resource development, shipping, and the coastal economy, the number of various ships, offshore platforms, subsea pipelines, and other marine facilities has increased dramatically. However, the harsh marine environment, especially seawater corrosion and marine biofouling, seriously threatens the safety, durability, and operational economics of these facilities. Statistics show that marine biofouling can increase hull drag by up to 60%, fuel consumption by 40%, and accelerate material corrosion, resulting in hundreds of billions of dollars in economic losses to global shipping and marine engineering annually. Therefore, developing efficient, long-lasting, and environmentally friendly marine anti-corrosion and antifouling materials and technologies is of great practical significance.

[0003] Currently, the mainstream technologies in the field of marine corrosion and antifouling mainly include anti-corrosion coatings and antifouling coatings. The former, represented by epoxy resins and zinc-rich coatings, possesses excellent adhesion and shielding properties, effectively blocking the penetration of water, oxygen, and corrosive media. However, these coatings typically suffer from insufficient toughness, poor weather resistance, and high surface hardness but also brittleness, making them prone to cracking due to impact or deformation in dynamic marine environments, leading to protective failure. The latter, primarily antifouling paints, initially focused on releasing toxic substances such as organotin compounds, but these have been banned by international conventions due to their severe damage to the marine ecosystem. The current mainstream is tin-free self-polishing antifouling coatings based on cuprous oxide, which continuously release toxic substances and renew the surface through controlled hydrolysis. Nevertheless, such coatings still pose a potential ecological risk of heavy metal accumulation, and their polymer substrates (such as acrylic resins) have limited mechanical and anti-corrosion properties, usually requiring use in conjunction with an anti-corrosion underlayer, resulting in a complex system.

[0004] Given the aforementioned challenges, polyurethane materials are considered a highly promising solution due to their excellent molecular designability and comprehensive properties. By flexibly selecting polyols, isocyanates, and chain extenders, the microphase separation structure of polyurethane can be precisely controlled, thereby obtaining a range of materials from high elasticity to high hardness, while also possessing excellent toughness, abrasion resistance, adhesion, and potential hydrolysis resistance, making it an ideal matrix resin for multifunctional marine protective coatings. However, the synthesis and application of polyurethane in marine environments still face many unresolved issues, mainly the contradiction between long-term effectiveness and stability, and the unsustainability of antifouling functions.

[0005] Compared with traditional epoxy and phenolic resins, self-healing polyurethane resins have many superior properties such as active repair, multiple healing capabilities, high toughness, high elasticity, and good impact resistance. However, their application range is limited by problems such as harsh healing conditions (e.g., the need for high-temperature heat treatment), difficulty in balancing initial mechanical properties and healing efficiency, and limited healing life.

[0006] Therefore, there is an urgent need in this field for a novel method for synthesizing self-healing polyurethane antifouling coatings to overcome the shortcomings of existing technologies and expand their application scope. Summary of the Invention

[0007] To address the problems existing in the prior art, this disclosure provides a method for preparing a self-healing polyurethane resin and its coating.

[0008] The self-healing polyurethane resin is prepared from the following raw materials: polytetrahydrofuran; isophorone diisocyanate and catalyst dibutyltin dilaurate; 1,4-butanediol or bis(2-hydroxyethyl) disulfide. In some embodiments, the raw materials also include DL-α-lipoic acid and catalyst tetrabutyl titanate.

[0009] In some embodiments, the molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol, or bis(2-hydroxyethyl) disulfide is (0.014~20):(0.004~20):(0.004~20).

[0010] In some embodiments, the molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol or bis(2-hydroxyethyl) disulfide, and DL-α-lipoic acid is (0.014~20):(0.004~20):(0.004~20):(0.004~20).

[0011] The method for preparing the self-healing polyurethane resin coating includes the following steps: Step S1, placing polytetrahydrofuran in a three-necked flask, heating to remove water and maintaining an oxygen-free environment; Step S2, adding a certain amount of isophorone diisocyanate and catalysts dibutyltin dilaurate and anhydrous tetrahydrofuran to the system, and reacting at this temperature; Step S3, cooling and adding 1,4-butanediol or bis(2-hydroxyethyl) disulfide and anhydrous tetrahydrofuran to the system, and reacting; Step S4, immediately cooling after the reaction, rotary evaporating off excess solvent, coating the product onto the surface of the substrate and curing to form a coating.

[0012] In some embodiments, step S34 is further included between steps S3 and S4: maintaining the temperature of step S3 and adding DL-α-lipoic acid and the catalyst tetrabutyl titanate to the system for reaction.

[0013] In some embodiments, in step S1, the heating temperature is 75°C to 80°C.

[0014] In some embodiments, in step S3, the temperature is lowered to 70°C~73°C.

[0015] In some embodiments, the reaction time in step S34 is 5.5 h to 6 h.

[0016] In some embodiments, in step S4, the temperature is lowered to 20°C to 25°C; the curing temperature is room temperature; and the curing time is 2h to 6h.

[0017] The beneficial effects of this disclosure are as follows: the self-healing polyurethane described in this disclosure has a high synthesis rate, and the self-healing polyurethane (R1-R4) resin coating obtained by the method of this disclosure has high self-healing ability, long healing life, low curing temperature, and also has excellent mechanical properties and anti-corrosion and anti-fouling properties. Attached Figure Description

[0018] Figure 1 The images show the infrared spectra of the self-healing polyurethane resins obtained in Examples 1-4, where curves A and D represent the sample spectral curves of Examples 1-4, respectively.

[0019] Figure 2 The bar chart shows the adhesion values ​​of the self-healing polyurethane resins obtained in Examples 1-4, where A and D represent the adhesion values ​​of the samples in Examples 1-4, respectively.

[0020] Figure 3 The images show actual drop hammer tests of the self-healing polyurethane resins obtained in Examples 1-4 to assess their impact resistance.

[0021] Figure 4 The images show actual photos of the self-healing polyurethane resins obtained in Examples 1-4 undergoing self-healing experiments in room temperature air and artificial seawater environments.

[0022] Figure 5 The images show the room temperature self-healing process of Examples 1-4 under a fluorescence optical microscope. A1-D1 are actual images of the scratches in Examples 1-4, A2-D2 are actual images of the healed objects 6 hours after the scratches, and A3-D3 are actual images of the healed objects 7 days after the scratches. Detailed Implementation

[0023] It should be understood that the disclosed embodiments are merely examples of this disclosure, and this disclosure can be implemented in various forms. Therefore, the specific details of this disclosure should not be construed as limiting, but rather serve as the basis for the claims, to teach those skilled in the art how to implement this disclosure in various ways. In the description of this disclosure, terms and technical terms not explicitly stated are common knowledge to those skilled in the art, and methods not explicitly stated are conventional methods known to those skilled in the art.

[0024] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0025] [Self-healing polyurethane resin] This disclosure provides a polyurethane resin that can autonomously trigger healing in ambient and marine environments while maintaining excellent initial mechanical properties and long-term environmental stability.

[0026] The self-healing polyurethane resin disclosed herein comprises the following raw materials: polytetrahydrofuran; isophorone diisocyanate and catalyst dibutyltin dilaurate (DBTDL); 1,4-butanediol or bis(2-hydroxyethyl) disulfide. These raw materials can be used to prepare two different self-healing polyurethanes, R1 (containing 1,4-butanediol) or R3 (containing bis(2-hydroxyethyl) disulfide).

[0027] DBTDL is used as a catalyst to catalyze reactions involving isophorone diisocyanate. If other catalysts are used instead, the preparation effect cannot be obtained well.

[0028] The number-average molecular weight of polytetrahydrofuran should not be too high or too low. In some embodiments, the number-average molecular weight M of polytetrahydrofuran is... n It is between 850 and 1000.

[0029] The amount of raw materials used in the preparation of R1 and R3 can be adjusted according to actual needs. In some embodiments, the molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol or bis(2-hydroxyethyl) disulfide is (0.014~20):(0.004~20):(0.004~20).

[0030] Based on R1 and R3, other raw materials can be introduced to obtain two more self-healing polyurethane segments with improved properties (corresponding to R2 and R4 respectively). In some embodiments, the raw materials for preparing the self-healing polyurethane resin also include DL-α-lipoic acid and the catalyst tetrabutyl titanate.

[0031] Tetrabutyl titanate is used as a catalyst to catalyze reactions involving DL-α-lipoic acid. If other catalysts are used instead, the preparation effect cannot be obtained well.

[0032] The amount of raw materials used in the preparation of R2 and R4 can be adjusted according to actual needs. In some embodiments, the molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol or bis(2-hydroxyethyl) disulfide, and DL-α-lipoic acid is (0.014~20):(0.004~20):(0.004~20):(0.004~20).

[0033] The above four types of self-healing polyurethanes with different chain segments have different focuses in terms of mechanical properties, impact resistance, and self-healing properties. Those skilled in the art can select appropriate raw materials to add according to the specific properties required or emphasized to obtain the desired self-healing resin.

[0034] [Preparation method of self-healing polyurethane resin coating] The self-healing polyurethane resin described in this disclosure can be prepared by prepolymerizing polytetrahydrofuran, isophorone diisocyanate, and dibutyltin dilaurate in an organic solvent, followed by chain extension reaction of the reaction product with a diol (i.e., 1,4-butanediol) or a thiol (i.e., bis(2-hydroxyethyl) disulfide), and then coating it onto a substrate to form coating R1 or R3. Alternatively, after the chain extension reaction, disulfide segments (i.e., thioctic acid) can be added for end-capping to adjust the self-healing properties, and then coated onto a substrate to form coating R2 or R4.

[0035] In some embodiments, the method for preparing the self-healing polyurethane resin coating R1 or R3 includes the following steps: Step S1, placing polytetrahydrofuran in a three-necked flask, heating to remove water and maintaining an oxygen-free environment; Step S2, adding a certain amount of isophorone diisocyanate and catalysts dibutyltin dilaurate and anhydrous tetrahydrofuran to the system, and reacting at this temperature; Step S3, cooling and adding 1,4-butanediol or bis(2-hydroxyethyl) disulfide and anhydrous tetrahydrofuran to the system, and reacting; Step S4, immediately cooling after the reaction, rotary evaporating off excess solvent, coating the product onto the surface of the substrate and curing to form coating R1 or R3.

[0036] In some embodiments, in step S1, the heating temperature is 75°C to 80°C.

[0037] In some embodiments, the reaction time in step S2 is 2.5h to 3h.

[0038] In some embodiments, in step S3, the temperature is lowered to 70°C~73°C.

[0039] In some embodiments, in step S4, the temperature is lowered to 20°C~25°C.

[0040] In some embodiments, in step S4, the curing temperature is room temperature; the curing time is 2h to 6h.

[0041] This disclosure does not specifically limit the material of the substrate. In some embodiments, in step S4, the substrate includes at least two of the following: a metal substrate, a glass substrate, a ceramic substrate, an enamel substrate, a polymer substrate, and a composite substrate formed from the above substrates.

[0042] For the preparation method of the above self-healing polyurethane resin coating R1 or R3, a further step S34 can be added between steps S3 and S4 to obtain coating R2 or R4. Step S34 is: maintaining the temperature of step S3 and adding DL-α-lipoic acid and the catalyst tetrabutyl titanate to the system for reaction.

[0043] In some embodiments, in step S34, the reaction time is 5.5 h to 6 h.

[0044] For the dosage of each substance used in the preparation process, please refer to the aforementioned range of raw material dosages for self-healing polyurethane resin.

[0045] The above method can be used to attach self-healing polyurethane resin to the substrate of the product or to at least part of the surface of the substrate, thereby improving the product's anti-corrosion and anti-fouling properties; the above method can give polyurethane resin good self-healing properties while maintaining the original mechanical properties of polyurethane resin as much as possible.

[0046] In some embodiments, the preparation method of the self-healing polyurethane resin coating involves an organic solvent selected from at least one of methanol, chloroform, dimethylformamide, xylene, tetrahydrofuran, toluene, and dichloromethane.

[0047] [Example] The present disclosure is further illustrated below with reference to the embodiments. Unless otherwise specified, the reagents, materials and instruments used in the following embodiments and comparative examples are commercially available or prepared by methods known in the art.

[0048] Example 1 Weigh 0.014 mol (3.4 g) of polytetrahydrofuran (Mn~850) into a 100 mL three-necked flask, heat to 75 °C to remove water and maintain an oxygen-free environment; add a mixed solution of dibutyltin dilaurate (0.1~0.2%), isophorone diisocyanate (0.004 mol, 3.112 g) and anhydrous tetrahydrofuran (25 mL) dropwise to the oxygen-free system through a dropping funnel, and react at 75 °C for 2.5~3 h; then cool to 70 °C and add 0.004 mol (0.36 g) of 1,4-butanediol dissolved in an appropriate amount of anhydrous tetrahydrofuran into the system through a microsyringe, and react for 4 h; immediately after the reaction is completed, cool to 25 °C, evaporate excess solvent by rotary evaporation, and then drop (brush) onto a clean glass slide or carbon steel surface for curing treatment to obtain self-healing polyurethane resin R1(A).

[0049] Example 2 Weigh 0.014 mol (3.4 g) of polytetrahydrofuran (Mn~850) into a 100 mL three-necked flask, heat to 75 °C to remove water and maintain an anaerobic environment; add a mixed solution of dibutyltin dilaurate (0.1~0.2%), isophorone diisocyanate (0.004 mol, 3.112 g) and anhydrous tetrahydrofuran (25 mL) dropwise to the anaerobic system through a dropping funnel, and react at 75 °C for 2.5~3 h; then cool to 70 °C and add 0.14-butanediol (0.4 g) dissolved in an appropriate amount of anhydrous tetrahydrofuran into the system through a microsyringe. 0.004 mol, 0.36 g) was added to the system and reacted for 4 h. Finally, tetrabutyl titanate (0.020 g) and DL-α-lipoic acid (0.003 mol, 0.62 g) dissolved in an appropriate amount of anhydrous tetrahydrofuran were added to the system through a microsyringe, and the reaction was carried out at 70 °C for 6 h. After the reaction was completed, the temperature was immediately lowered to 25 °C, excess solvent was evaporated, and then the solution was dripped (brushed) onto a clean glass slide or carbon steel surface for curing treatment to obtain self-healing polyurethane resin R2(B).

[0050] Example 3 Weigh 0.014 mol (3.4 g) of polytetrahydrofuran (Mn~850) into a 100 mL three-necked flask, heat to 75 °C to remove water and maintain an oxygen-free environment; add a mixed solution of dibutyltin dilaurate (0.1~0.2%), isophorone diisocyanate (0.004 mol, 3.112 g) and anhydrous tetrahydrofuran (25 mL) dropwise to the oxygen-free system through a dropping funnel, and react at 75 °C for 2.5~3 h; then cool to 70 °C and add 0.004 mol (0.62 g) of bis(2-hydroxyethyl) disulfide dissolved in an appropriate amount of anhydrous tetrahydrofuran into the system through a microsyringe, and react for 4 h; immediately after the reaction is completed, cool to 25 °C, evaporate excess solvent by rotary evaporation, and then drop (brush) onto a clean glass slide or carbon steel surface for curing treatment to obtain self-healing polyurethane resin R3(C).

[0051] Example 4 Weigh 0.014 mol (3.4 g) of polytetrahydrofuran (Mn~850) into a 100 mL three-necked flask, heat to 75 °C to remove water and maintain an anaerobic environment; add a mixed solution of dibutyltin dilaurate (0.1~0.2%), isophorone diisocyanate (0.004 mol, 3.112 g), and anhydrous tetrahydrofuran (25 mL) dropwise to the anaerobic system through a dropping funnel, and react at 75 °C for 2.5~3 h; then cool to 70 °C and add bis(2-hydroxyethyl) disulfide dissolved in an appropriate amount of anhydrous tetrahydrofuran into the system through a microsyringe. 0.004 mol, 0.62 g) of tetrabutyl titanate and DL-α-lipoic acid dissolved in an appropriate amount of anhydrous tetrahydrofuran were added to the system and reacted at 70 °C for 6 h. After the reaction was completed, the temperature was immediately lowered to 25 °C, excess solvent was evaporated, and then the solution was dripped (brushed) onto a clean glass slide or carbon steel surface for curing to obtain self-healing polyurethane resin R4(D).

[0052] The material parameters involved in the experiments of Examples 1-4 are shown in Table 1, and the self-healing times of the obtained samples are shown in Table 2. For ease of explanation, symbols are used to represent substances in Table 1: A1: Polytetrahydrofuran (Mn~850); A2: Dibutyltin dilaurate; A3: Isophorone diisocyanate; B1: 1,4-Butanediol; B2: Bis(2-hydroxyethyl) disulfide; C1: Tetrabutyl titanate; C2: DL-α-lipoic acid; Next, infrared testing, mechanical testing, impact resistance testing, and self-healing experiment testing were conducted on the relevant samples obtained in the above embodiments.

[0053] 1. Infrared Testing: The transmittance of the self-healing polyurethane resins obtained in Examples 1-4 was tested using a Fourier Transmittance Infrared Spectrometer (FT-IR) (IS-50). The scanning results are as follows: Figure 1 As shown.

[0054] 2. Mechanical Testing: Adhesion tests were conducted on the self-healing polyurethane resin samples obtained in Examples 1-4. The tests were performed using a PosiTest AT pull-out tester. The adhesion test results are as follows: Figure 2 As shown.

[0055] 3. Impact Resistance Test: The self-healing polyurethane resins obtained in Examples 1-4 were subjected to impact resistance tests. The test method was a drop hammer test using an impact tester, the test standard was ASTM D2794, and the test mode was positive impact. The test results are as follows: Figure 3 As shown.

[0056] Table 1. Material parameters involved in the experiments of Examples 1-4 Note: - indicates no addition.

[0057] 4. Self-healing test: The self-healing performance of the self-healing polyurethane resin coating was evaluated through the following experiment: First, a glass slide coated with the study coating was scratched to the substrate surface using a scalpel. The scratches were then photographed using a fluorescence optical microscope. After the coating healed in air and seawater, it was photographed again using a fluorescence optical microscope. The self-healing performance of the coating was comprehensively evaluated based on the self-healing time from scratch to healing and the degree of wound healing. The test results are as follows: Figure 5 As shown.

[0058] Depend on Figure 1 It can be known that 3300~3500cm -1 The typical band at 2948 cm⁻¹ is due to the stretching vibration of NH₃. -1 and 2857cm -1 The characteristic peak at 1698 cm⁻¹ originates from the CH stretching vibration of polyols. -1 This is a C=O stretching vibration originating from the carbamate bond, 1530–1560 cm⁻¹ -1 The characteristic peak at 1100 cm⁻¹ originates from the NH bending and C-N stretching of the "amide II band" in the carbamate bond. -1The characteristic peaks are COC stretching vibrations in polyether polyols or polyester polyols. As can be seen above, the characteristic peaks of different functional groups on polyurethane were successfully detected, indicating that self-healing polyurethane resins (R1~R4) were successfully prepared.

[0059] Depend on Figure 2 It can be seen that the self-healing polyurethane resins (R1~R4) have excellent mechanical properties. The adhesion of common polyurethane coatings is generally around 5 MPa, while the adhesion of the self-healing polyurethane resin obtained in this embodiment is 6.46 MPa~8.03 MPa. Therefore, this self-healing polyurethane resin (R1~R4) has improved and excellent mechanical properties. In addition, the adhesion of resins R1~R3 ​​is around 8 MPa, which further improves the mechanical properties.

[0060] Depend on Figure 3 The impact test results show that after the self-healing polyurethane (R1~R4) resin is coated on the substrate surface, the self-healing polyurethane resin (R1~R4) in Examples 1-4 is still not damaged when the test energy of the drop hammer test is 50 kg·cm or above, which shows that the self-healing polyurethane resin (R1~R4) has excellent impact resistance.

[0061] Depend on Figure 4 The experimental results show that the self-healing polyurethane resins (R1~R4) obtained in Examples 1~4 can achieve self-healing in both room temperature air and artificial seawater, and therefore all have good self-healing ability.

[0062] Figure 5 The images show the room-temperature self-healing process of self-healing polyurethane resins (R1~R4) captured under a fluorescence optical microscope. Microscopic observation further confirms the excellent self-healing ability of the obtained self-healing polyurethane resins (R1~R4). Among them, R2 and R4, which have disulfide bonds as end caps, exhibit greater self-healing effects than their precursor resins R1 and R3. This is because the self-healing of R2 and R4 involves the combined action of dynamic non-covalent bonds (hydrogen bonds) and dynamic covalent bonds (disulfide bonds), while R1 relies solely on hydrogen bonds. R3, with its thiol chain extension, also exhibits healing effects from both disulfide and hydrogen bonds, but its overall self-healing effect is not as significant as that of R2 and R4 within the same timeframe. Therefore, in terms of self-healing effect, R4 > R2 > R3 > R1.

[0063] The above description is merely an example of this disclosure and is not intended to limit this disclosure in any way. Although this disclosure is presented above with preferred embodiments, it is not intended to limit this disclosure. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solutions disclosed herein are equivalent to equivalent implementation cases and are all within the scope of the technical solutions disclosed herein.

Claims

1. A self-healing polyurethane resin, wherein, The raw materials for its preparation include: polytetrahydrofuran; isophorone diisocyanate and catalyst dibutyltin dilaurate; 1,4-butanediol or bis(2-hydroxyethyl) disulfide.

2. The self-healing polyurethane resin according to claim 1, characterized in that, Its raw materials also include DL-α-lipoic acid and the catalyst tetrabutyl titanate.

3. The self-healing polyurethane resin according to claim 1, characterized in that, The molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol or bis(2-hydroxyethyl) disulfide is (0.014~20):(0.004~20):(0.004~20).

4. The self-healing polyurethane resin according to claim 2, characterized in that, The molar ratio of polytetrahydrofuran, isophorone diisocyanate, 1,4-butanediol or bis(2-hydroxyethyl) disulfide, and DL-α-lipoic acid is (0.014~20):(0.004~20):(0.004~20):(0.004~20).

5. A method for preparing a self-healing polyurethane resin coating, wherein, Including the following steps: Step S1: Place polytetrahydrofuran into a three-necked flask, heat to remove water and maintain an oxygen-free environment; In step S2, a fixed amount of isophorone diisocyanate and catalysts dibutyltin dilaurate and anhydrous tetrahydrofuran are added to the system, and the reaction is carried out at this temperature. Step S3: Cool down and add 1,4-butanediol or bis(2-hydroxyethyl) disulfide or anhydrous tetrahydrofuran to the system to carry out the reaction; Step S4: After the reaction is complete, immediately cool down, evaporate excess solvent, and coat the product onto the substrate surface to cure, forming a coating.

6. The method for preparing the self-healing polyurethane resin coating according to claim 5, characterized in that, Between steps S3 and S4, there is also step S34: maintaining the temperature of step S3, and adding DL-α-lipoic acid and the catalyst tetrabutyl titanate to the system for reaction.

7. The method for preparing the self-healing polyurethane resin coating according to claim 5, characterized in that, In step S1, the heating temperature is 75℃~80℃.

8. The method for preparing the self-healing polyurethane resin coating according to claim 5, characterized in that, In step S3, the temperature is lowered to 70℃~73℃.

9. The method for preparing a self-healing polyurethane resin coating according to claim 6, characterized in that, In step S34, the reaction time is 5.5 h to 6 h.

10. The method for preparing the self-healing polyurethane resin coating according to claim 5, characterized in that, In step S4, the temperature is lowered to 20℃~25℃; the curing temperature is room temperature; and the curing time is 2h~6h.

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