A bio-based polyurethane antibacterial and antifouling coating, its preparation method and application

Abstract

This invention belongs to the technical field of polymer functional coating materials, and discloses a bio-based polyurethane antibacterial and antifouling coating, its preparation method, and its application. It addresses the technical shortcomings of existing polyurethane coatings, such as reliance on petrochemical raw materials, limited functionality, poor synergistic effect of antibacterial and antifouling properties, short duration of antibacterial and antifouling effects, insufficient biosafety, and complex preparation processes. The steps are as follows: a polyorganosiloxane with single-terminated hydroxyl groups is dissolved in organic solvent I and a polyisocyanate compound is added to carry out the first reaction to obtain reaction solution I; curcumin is dissolved in organic solvent I and added to reaction solution I to carry out the second reaction to obtain reaction solution II; a bio-based polyol is dissolved in organic solvent II and added to reaction solution II to carry out the third reaction to obtain the bio-based polyurethane antibacterial and antifouling coating. The resulting coating exhibits excellent antibacterial properties, antifouling properties, and self-recovering antifouling function, and can be applied to various substrates such as glass, metal, wood, and ceramics, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of polymer functional coating materials technology, and particularly relates to a method for preparing a bio-based polyurethane antibacterial and anti-fouling coating. Background Technology

[0002] Polyurethane coatings exhibit excellent performance and have been widely applied in many fields. The raw materials used in traditional polyurethane preparation, such as polyether polyols and polyester polyols, are mainly derived from petrochemical-based polyols. The excessive consumption of these non-renewable resources contradicts the "dual carbon" strategy goals, and their waste is difficult to degrade, easily causing environmental burden. Developing bio-based polyurethane materials based on renewable bio-based raw materials has become a research hotspot in the polyurethane field due to its alignment with sustainable development needs. Currently reported bio-based polyurethane coatings prepared from polyols derived from natural products such as vegetable oils and starch generally lack antibacterial or antifouling properties. Even those coatings that do possess antibacterial or antifouling properties have limited application scenarios due to their singular functionality, particularly failing to meet the application needs of fields with high hygiene requirements, such as medical and food industries.

[0003] In fields such as medical, food, home furnishing, and marine applications, coating surfaces are prone to biofilm formation due to microbial growth. They are also susceptible to contamination from dust, stains, and bodily fluids, which can lead to safety hazards such as cross-infection and product contamination, and may also affect the lifespan and performance of the materials. Introducing antibacterial and antifouling components can achieve functional modification of the coating; however, organic antibacterial agents such as quaternary ammonium salts have problems such as high toxicity and easy migration leading to shortened antibacterial duration, while inorganic antibacterial agents such as silver nanoparticles have problems such as poor dispersibility and easy aggregation affecting the mechanical properties of the coating. Furthermore, modifying the coating surface with fluorinated materials for antifouling modification has problems such as poor biocompatibility and difficulty in degradation, while traditional polysiloxane block modification has problems such as poor adhesion between the coating and the substrate.

[0004] Existing polyurethane coating preparation technologies that combine bio-based properties, excellent antifouling properties, and high-efficiency antibacterial properties still have many shortcomings:

[0005] 1) Poor synergy between antibacterial and antifouling functions. Most coating preparations only optimize the antibacterial or antifouling function, ignoring the synergy between the two functions, and it is difficult to balance the relationship between antibacterial and antifouling performance and mechanical properties.

[0006] 2) Short-lasting antibacterial and antifouling properties. Most coatings experience a decline or loss of antibacterial or antifouling properties after prolonged use or damage from scratches, impacts, acid and alkali corrosion, etc., and their antibacterial and antifouling functions are difficult to self-recover. For example, the prior art WO2022160853A discloses a method for preparing a UV-responsive coumarin-controlled and self-healing antifouling coating. The antifouling and self-healing functions of this patent rely entirely on the reversible UV-responsive reaction of coumarin, exhibiting an excessive dependence on "specific conditions (UV light)" and "irreversible consumption (coumarin, binding sites, matrix structure)," leading to strict application conditions and short-lasting antibacterial and antifouling properties.

[0007] 3) Significant biosafety risks. Most antibacterial agents are chemically synthesized, posing significant biosafety risks and contradicting the environmentally friendly principles of bio-based materials.

[0008] 4) Complex preparation process. The preparation of most functional coatings requires multiple steps of composite modification, which is complex and involves harsh reaction conditions, making it unsuitable for large-scale production.

[0009] Therefore, developing a simple and controllable process to prepare bio-based polyurethane coatings with excellent antibacterial and antifouling properties, good mechanical properties, and environmental compatibility has become a pressing technical problem in this field. The development of such coatings can not only reduce dependence on petrochemical resources but also expand the application of bio-based polyurethanes in high-end functional protection fields, possessing significant theoretical importance and broad application prospects. Summary of the Invention

[0010] To address the shortcomings of existing polyurethane coatings, such as reliance on petrochemical raw materials, limited functionality, poor synergy between antibacterial and antifouling properties, short duration of antibacterial and antifouling effects, insufficient biosafety, and complex preparation processes, this invention proposes a bio-based polyurethane antibacterial and antifouling coating, its preparation method, and its application.

[0011] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0012] This invention adopts a stepwise reaction to introduce functional components for in-situ grafting and covalent reaction. By controlling the order of raw material feeding and reaction conditions, antifouling components, curcumin and bio-based polyurethane matrix are efficiently fused to obtain bio-based polyurethane antibacterial and antifouling coating.

[0013] Specifically, the preparation method of the bio-based polyurethane antibacterial and antifouling coating of the present invention includes the following steps:

[0014] (1) A polyorganosiloxane with a single-terminated hydroxyl group and a polyisocyanate compound are dissolved in organic solvent I to carry out the first step of the reaction, resulting in reaction solution I. The polyorganosiloxane with a single-terminated hydroxyl group serves as the antifouling functional component. Its single-terminated hydroxyl group can react with the isocyanate group (-NCO) of the polyisocyanate compound, achieving in-situ grafting of polysiloxane segments into the polyurethane precursor. The use of a single-terminated hydroxyl structure not only ensures that it is chemically anchored in the polyurethane structure, but also allows the low surface energy polyorganosiloxane grafted chains to spontaneously migrate to the coating surface, imparting excellent antifouling properties to the coating.

[0015] The molar number of hydroxyl groups in the aforementioned polyorganosiloxanes with single-hydroxyl-terminated ends is 0.2-0.5% of the total molar number of hydroxyl groups in the polyorganosiloxanes with single-hydroxyl-terminated ends, curcumin, and bio-based polyols. The weight-average molecular weight of the polyorganosiloxanes with single-hydroxyl-terminated ends is 3000-10000. This molecular weight and dosage can balance antifouling performance and coating transparency. If the molecular weight is too high or the dosage is too high, the coating transparency will easily decrease. If the molecular weight is too low or the dosage is too low, the antifouling effect will be insufficient.

[0016] The polyisocyanate compound is a compound containing three or more isocyanate groups. The molar ratio of the isocyanate groups to the total hydroxyl groups in polyorganosiloxanes with single-terminated hydroxyl groups, curcumin, and bio-based polyols is 1:(1-1.2). This allows for the formation of a dense three-dimensional network structure through cross-linking of multifunctional groups, thereby improving the mechanical properties of the coating. Furthermore, the aforementioned polyisocyanate compound is at least one of hexamethylene diisocyanate trimer, hexamethylene diisocyanate biuret, isophorone diisocyanate trimer, and toluene diisocyanate trimer.

[0017] The reaction temperature is 25-80℃, and the reaction time is 1-3 h. This temperature range ensures a stable reaction, and the reaction time ensures that the single-terminal hydroxyl groups and some NCO groups react fully, reserving active sites for the subsequent incorporation of antibacterial components and bio-based polyols.

[0018] (2) Dissolve curcumin (CUR) in organic solvent I, add it to reaction solution I, and carry out the second step reaction at 25-80℃ for 1-6 h to obtain reaction solution II.

[0019] The hydroxyl groups in curcumin comprise 2-15.5% of the total hydroxyl groups in polyorganosiloxanes with single-terminal hydroxyl groups, curcumin, and bio-based polyols. This addition amount balances antibacterial properties and coating transparency; excessive addition can lead to decreased coating transparency, while insufficient addition results in inadequate antibacterial effect. The hydroxyl groups in curcumin can react with the remaining -NCO groups after the first reaction, introducing antibacterial components. Introducing antibacterial components through chemical reactions avoids the migration and loss of antibacterial agents caused by traditional physical doping, thus prolonging the antibacterial effect. Furthermore, curcumin's strong hydrophobicity can synergistically improve the coating's antifouling properties. Moreover, it has advantages such as good biocompatibility, low toxicity, and environmental friendliness, addressing the safety concerns of chemical antibacterial agents.

[0020] The reaction temperature of 25-80℃ in this step can avoid instability of the reaction system caused by sudden temperature changes; the reaction time of 1-6 h can ensure that the antibacterial agent and the precursor react fully and ensure the uniformity of the antibacterial performance of the coating.

[0021] Furthermore, in steps (1) and (2) above, organic solvent I is at least one of butanone, acetone, isopropanol, and n-hexane. The solvent should be selected in an appropriate amount to ensure complete dissolution of the raw materials and avoid uneven reaction caused by excessively high local concentrations.

[0022] (3) After dissolving the bio-based polyol in organic solvent II, add reaction solution II and carry out the third step reaction at 60-80℃ for 6-16 h to obtain the bio-based polyurethane antibacterial and anti-fouling coating.

[0023] In step (3) above, the hydroxyl groups in the bio-based polyol are 84%-97.5% of the total hydroxyl groups in the polyorganosiloxane with single-terminal hydroxyl groups, curcumin, and bio-based polyol. On the one hand, the hydroxyl groups of the bio-based polyol raw material undergo a cross-linking reaction with the remaining -NCO groups in the system to form a bio-based polyurethane matrix. This ratio ensures sufficient cross-linking of the system and a suitable polyurethane molecular weight, avoiding excessive -OH leading to a low polymer molecular weight, or excessive -NCO causing it to react with water in the air, affecting the coating's density or safety. On the other hand, replacing petrochemical-based polyols with renewable bio-based raw materials reduces dependence on non-renewable resources, aligning with the "dual carbon" strategy.

[0024] Furthermore, the aforementioned bio-based polyol is at least one selected from castor oil, starch, palm oil, and soybean oil. Organic solvent II is at least one selected from butanone, dimethyl carbonate (DMC), and N,N-dimethylformamide (DMF), which can meet the dissolution requirements of the bio-based polyol and ensure reaction uniformity. The reaction temperature of 60-80℃, higher than the previous two steps, accelerates the crosslinking reaction process, and the reaction time of 12-16 hours ensures complete crosslinking and improves the mechanical property stability of the coating.

[0025] This invention provides a bio-based polyurethane antibacterial and antifouling coating (denoted as: PU-PDMS-CUR) prepared using the above preparation method.

[0026] The present invention also provides the application of the above-mentioned bio-based polyurethane antibacterial and antifouling coating in antibacterial and antifouling coatings.

[0027] More specifically, the preparation method of the above-mentioned antibacterial and antifouling coating includes the following steps: A bio-based polyurethane antibacterial and antifouling coating is applied to the surface of a substrate (such as glass, metal, wood, ceramics, etc.) using methods such as roller coating, dip coating, spray coating, or spin coating, and then cured at 100-160℃ to obtain the antibacterial and antifouling coating. The curing temperature of 110-160℃ promotes the complete reaction of residual groups, while ensuring the coating adheres tightly to the substrate surface, improving adhesion and cross-linking. Simultaneously, the high temperature promotes the migration of polyorganosiloxane graft chains to the coating surface, endowing the coating with excellent antifouling properties. Multiple coating methods are suitable for different substrate morphologies (planar, curved, etc.), enhancing the applicability of the technology.

[0028] The coating prepared by the method of this invention can be widely used in medical devices, food packaging, building materials, marine engineering and other scenarios that require antibacterial and antifouling protection.

[0029] The beneficial effects of this invention are:

[0030] (1) Excellent antifouling performance; the antifouling function can self-recover after the coating surface is damaged. An antifouling coating is constructed by anchoring single-hydroxyl-terminated low surface energy liquid polyorganosiloxanes inside the coating through in-situ chemical grafting. The liquid polyorganosiloxane segments undergo microphase separation inside the coating to form nanoscale replenishment pools, which impart transparency to the coating. At the same time, the low surface energy liquid polymer graft chains spontaneously migrate to the coating surface to form a liquid film with a thickness of 10-30 nm, giving the coating excellent antifouling function. Even if the coating surface is damaged by physical wear or chemical corrosion, the internal nanopools will still be re-exposed on the new surface of the coating. The liquid polymer graft chains spontaneously migrate to the coating surface to form a new liquid film, realizing the self-recovery of the coating's antifouling function and giving the coating durable antifouling ability. Adding <5 wt% liquid polymer can achieve durable antifouling. A small amount of antifouling component has no significant effect on key properties such as coating hardness, adhesion, and temperature resistance.

[0031] (2) Synergistic enhancement of antibacterial and antifouling properties. Curcumin achieves a strong bond with the coating substrate through chemical reaction, resulting in long-lasting and stable antibacterial effects that effectively inhibit microbial growth. Simultaneously, the long-chain hydrophobic framework of curcumin further reduces the surface free energy of the coating, significantly weakening the adhesion energy between polar pollutants (water-soluble stains, body fluids, proteins, etc.) and non-polar pollutants (such as oil stains and dust particles) at the interface, inhibiting pollutant adsorption, spreading, and penetration, thus further improving the coating's antifouling properties. The polyorganosiloxanes on the coating surface, due to their extremely low surface energy, also inhibit microbial adhesion and spreading, further enhancing antibacterial properties. This synergistic enhancement of antibacterial and antifouling properties endows the coating with excellent antifouling and highly efficient antibacterial properties.

[0032] (3) The coating prepared by the present invention has a water contact angle greater than 107°. Liquid pollutants are easily shrunk on the coating and leave no trace after wiping. The coating does not significantly reduce its anti-fouling performance after being soaked in acidic, alkaline and neutral liquids for 48 hours. After physical wear or chemical corrosion reduces the anti-fouling performance of the coating, the coating can restore its anti-fouling performance after being placed at room temperature for 12 hours or heated at 160°C for 3 hours. The coating has an antibacterial rate of more than 95% against Escherichia coli and Staphylococcus aureus.

[0033] (4) High biosafety. The coating is prepared using bio-based raw materials and curcumin, which meets the needs of the "dual carbon" strategy. At the same time, no toxic and harmful substances such as fluorinated antifouling agents and chemical antibacterial agents are introduced during the preparation process. In addition, the polyurethane material itself has good biocompatibility, which has broad application prospects in medical devices, food packaging or applications that come into contact with the human body / food.

[0034] (5) The preparation process is simple and controllable. The one-pot reaction strategy is adopted in a step-by-step manner. The reaction conditions of each step are mild and do not require high temperature, high pressure or special catalysts. The raw material ratio and reaction parameters are precisely controllable and easy to achieve large-scale production. The amount of functional components is small, and the cost increase is small compared with conventional polyurethane coatings. The improvement of product refinement can bring higher added value. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This diagram illustrates the antifouling mechanism of the coating prepared from the bio-based polyurethane antibacterial and antifouling coating of the present invention.

[0037] Figure 2The figures show the water contact angles of the coatings (coatings A, B, C, D, E) prepared with the coatings of Examples 1-5 of the present invention and the coating (coating G) prepared with the coating of Comparative Example 2; in the figures, CUR% of 0 corresponds to PU-PDMS coating G, and CUR% of 1-5 represent PU-PDMS-CUR coatings A, B, C, D, and E respectively.

[0038] Figure 3 The image shows the ink shrinkage after being written on with a marker (left image) and the digital image after the ink has been wiped off (right image) of coating B prepared with the bio-based polyurethane antibacterial and anti-fouling coating of Example 2 of the present invention.

[0039] Figure 4 This study compares the antifouling performance of PU-PDMS-CUR coating B prepared using the bio-based polyurethane antibacterial and antifouling coating of Example 2 of the present invention with that of PU coating F, PU-PDMS coating G, and PU-CUR coating H prepared in Comparative Examples 1-3.

[0040] Figure 5 The diagram shows the change in antifouling performance of coating B prepared with the bio-based polyurethane antibacterial and antifouling coating of Example 2 of the present invention after chemical corrosion; wherein, (a) is a diagram showing the change in antifouling performance of the above coating after immersion in hydrochloric acid solution with pH=2 over time; (b) is a diagram showing the change in antifouling performance of the above coating after immersion in sodium hydroxide solution with pH=12 over time; and (c) is a diagram showing the change in antifouling performance of the above coating after immersion in deionized water with pH=7 over time.

[0041] Figure 6 The diagram shows the change in antifouling performance of coating G prepared with the bio-based antibacterial and antifouling coating of Comparative Example 2 of the present invention after chemical corrosion; wherein, (a) is a diagram showing the change in antifouling performance of the above coating after immersion in hydrochloric acid solution with pH=2 over time; (b) is a diagram showing the change in antifouling performance of the above coating after immersion in sodium hydroxide solution with pH=12 over time; and (c) is a diagram showing the change in antifouling performance of the above coating after immersion in deionized water with pH=7 over time.

[0042] Figure 7 The images show the self-recovery effect of the antifouling performance of coating B prepared with the bio-based antibacterial and antifouling coating of Example 2 of the present invention after corrosion at room temperature; wherein, (a) shows the self-recovery effect of the antifouling performance of coating B1 after being treated with hydrochloric acid solution at pH=2 and placed at room temperature for different times; (b) shows the self-recovery effect of the antifouling performance of coating B2 after being treated with sodium hydroxide solution at pH=12 and placed at room temperature for different times; and (c) shows the self-recovery effect of the antifouling performance of coating B3 after being treated with deionized water at pH=7 and placed at room temperature for different times.

[0043] Figure 8The images show the self-recovery effect of the antifouling performance of coating B prepared with the bio-based antibacterial and antifouling coating of Example 2 of the present invention after corrosion at high temperature; wherein, (a) shows the self-recovery effect of the antifouling performance of coating B1 after being treated with hydrochloric acid solution of pH=2 and placed at 160°C for different times; (b) shows the self-recovery effect of the antifouling performance of coating B2 after being treated with sodium hydroxide solution of pH=12 and placed at 160°C for different times; (c) shows the self-recovery effect of the antifouling performance of coating B3 after being treated with deionized water of pH=7 and placed at 160°C for different times.

[0044] Figure 9 Digital images showing the anti-Escherichia coli effects of coating E (e) and blank glass slide (a), PU coating F (b), PU-PDMS coating G (c) and PU-CUR coating H (d) prepared with the PU-PDMS-CUR coating of Example 5 of the present invention.

[0045] Figure 10 Digital images showing the anti-Staphylococcus aureus effects of coating E (e) and blank glass slide (a), PU coating F (b), PU-PDMS coating G (c) and PU-CUR coating H (d) prepared with the PU-PDMS-CUR coating of Example 5 of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0047] Example 1

[0048] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0049] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0050] (2) Accurately weigh 7.9 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 72℃ for 5 h to carry out the second step reaction and obtain reaction solution II.

[0051] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating (the raw material ratio of curcumin is 1 wt%).

[0052] Example 2

[0053] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0054] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0055] (2) Accurately weigh 15.9 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 72℃ for 5 h to carry out the second step reaction and obtain reaction solution II.

[0056] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating (the raw material ratio of curcumin is 2 wt%).

[0057] Example 3

[0058] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0059] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0060] (2) Accurately weigh 24.1 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 72℃ for 5 h to carry out the second step reaction and obtain reaction solution II.

[0061] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating (the raw material ratio of curcumin is 3 wt%).

[0062] Example 4

[0063] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0064] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0065] (2) Accurately weigh 32.5 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 72℃ for 5 h to carry out the second step reaction and obtain reaction solution II.

[0066] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating (the raw material ratio of curcumin is 4 wt%).

[0067] Example 5

[0068] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0069] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0070] (2) Accurately weigh 41.1 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 72℃ for 5 h to carry out the second step reaction and obtain reaction solution II.

[0071] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating (the raw material ratio of curcumin is 5 wt%).

[0072] Example 6

[0073] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0074] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 3000) and 149.7 mg of hexamethylene diisocyanate trimer and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in an oil bath at 25 °C for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0075] (2) Accurately weigh 30.3 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 80℃ for 1 h to carry out the second step reaction and obtain reaction solution II.

[0076] (3) Accurately weigh 306.7 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 60℃ for the third crosslinking reaction for 16 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating.

[0077] Example 7

[0078] The preparation method of a bio-based polyurethane antibacterial and antifouling coating in this embodiment includes the following steps:

[0079] (1) Accurately weigh 33.4 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 10000) and 250 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in an 80℃ oil bath for 1 h to carry out the first step of the reaction, and obtain reaction solution I.

[0080] (2) Accurately weigh 15.9 mg of curcumin powder and dissolve it in 0.5 mL of butanone. After dissolving, add it to the first step reaction system and react in an oil bath at 25°C for 6 h to carry out the second step reaction and obtain reaction solution II.

[0081] (3) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution II and place it in an oven at 80℃ for the third crosslinking reaction for 6 h to obtain a bio-based polyurethane antibacterial and anti-fouling coating.

[0082] Comparative Example 1

[0083] The preparation method of the coating in this comparative example differs from that in Example 2 in that PDMS-OH and curcumin are not added. The steps are as follows:

[0084] (1) Accurately weigh 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve it in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle.

[0085] (2) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to the solution obtained in step (1) and place it in an oven at 72°C for the third crosslinking reaction for 12 h to obtain the coating, which is denoted as PU.

[0086] Comparative Example 2

[0087] The preparation method of the antifouling coating in this comparative example differs from that in Example 2 in that curcumin is not added. The steps are as follows:

[0088] (1) Accurately weigh 15.9 mg of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, weight average molecular weight 5000) and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72℃ oil bath for 3 h to carry out the first step of the reaction, and obtain reaction solution I.

[0089] (2) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to reaction solution I and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain an anti-fouling coating, denoted as PU-PDMS.

[0090] Comparative Example 3

[0091] The preparation method of the antibacterial coating in this comparative example differs from that in Example 2 in that PDMS-OH is not added. The steps are as follows:

[0092] (1) Accurately weigh 15.9 mg of curcumin powder and 250.0 mg of hexamethylene diisocyanate trimer (HDIT) and dissolve them in 1.5 mL of butanone (MEK). Seal the mixture in a 5 mL glass bottle, add a rotor and stir. Place the glass bottle in a 72°C oil bath for 5 h to obtain the reaction solution.

[0093] (2) Accurately weigh 514.0 mg of castor oil and dissolve it in 1 mL of dimethyl carbonate (DMC). Add it to the reaction solution obtained in step (1) and place it in an oven at 72℃ for the third crosslinking reaction for 12 h to obtain an anti-fouling coating, denoted as PU-CUR.

[0094] Implementation Results Example

[0095] The coatings prepared in Examples 1-5 and Comparative Examples 1-3 were applied to antibacterial and antifouling coatings, and the specific steps are as follows:

[0096] Take 0.4 mL of each coating and spin coat it onto a 2 cm × 2 cm glass slide using a spin coater. After the solvent evaporates for 10-15 min, place it in a 160℃ oven for high-temperature curing for 3 h to obtain PU-PDMS-CUR antibacterial and anti-fouling coatings A, B, C, D, and E, and PU coating F, PU-PDMS coating G, and PU-CUR coating H.

[0097] Figure 1 To explain the antifouling mechanism of the antibacterial and antifouling coatings prepared using the bio-based polyurethane antibacterial and antifouling coatings of Examples 1-5, an antifouling coating is constructed by anchoring low surface energy liquid polyorganosiloxanes with single-hydroxyl ends into the coating interior via in-situ chemical grafting. The liquid polymer segments undergo microphase separation within the coating, forming nanoscale replenishment pools that impart good transparency to the coating. The low surface energy liquid polymer graft chains spontaneously migrate to the coating surface to form a liquid film, giving the coating excellent antifouling properties. Even if the coating surface is physically worn or chemically corroded, the internal nanoscale pools are re-exposed on the new surface of the coating. The liquid polymer self-migrates to form a new liquid film on the coating surface, achieving self-recovery of the coating's antifouling function and endowing the coating with durable antifouling capabilities. Furthermore, the long-chain hydrophobic framework structure of curcumin further enhances the antifouling effect.

[0098] The properties of the coatings prepared above were tested and analyzed, and the results are as follows:

[0099] 1. Contact angle

[0100] Coatings A, B, C, D, E, and G, prepared using the coatings of Examples 1-5 and Comparative Example 2, were tested for water contact angle using an OCA20 water contact angle measuring instrument. First, the sample surface was ensured to be clean. The sample was fixed on the test stage and positioned in the center of the contact angle measuring instrument's camera. The droplet volume was set to 5 μL. The water contact angle value on the surface was measured. After stabilization for 30 seconds, a real-time image of the droplet was captured, and the CA value was obtained through fitting. The results are shown below. Figure 2 As shown, without curcumin, the water contact angle of coating G is 102°. After the introduction of curcumin, the water contact angles of coatings A, B, C, D, and E are significantly improved, all exceeding 107°, with the highest reaching 112°.

[0101] 2. Anti-fouling performance

[0102] (1) Antifouling performance

[0103] Using a marker (No. 6821), a 2.5 mm × 0.5 mm mark was written at a speed of 4 cm / s at a 45° angle on the antibacterial and anti-fouling coating B prepared with the bio-based polyurethane antibacterial and anti-fouling coating of Example 2 and the coatings F, G, and H prepared in Comparative Examples 1-3. The proportion of ink shrinkage area to the total ink coating area was then calculated using ImageJ software. It was found that the ink shrinkage area of ​​coating B was 83.6% of the coating area. The ink on the coating surface could be completely removed by wiping with lint-free paper. Figure 3 This demonstrates that the coating has excellent stain resistance.

[0104] Figure 4 A comparison of the stain resistance of coatings B, F, G, and H: Coating F (PU) showed no ink shrinkage, with the ink shrinkage area being 0% of the coated area, indicating no stain resistance. Coating H (PU-CUR) showed ink shrinkage of 37.2% of the coated area, exhibiting poor stain resistance. This is because the introduction of CUR, an antibacterial substance with a long-chain hydrophobic structure, reduces the surface energy of the coating to some extent, thus providing some stain resistance. Coating G (PU-PDMS) showed ink shrinkage of 81.0% of the coated area, demonstrating excellent stain resistance due to the introduction of the low surface energy substance PDMS. Coating B (PU-PDMS-CUR) showed ink shrinkage of 83.6% of the coated area, indicating superior stain resistance. This is because both anti-fouling and antibacterial components are introduced into the coating, working synergistically to give it superior stain resistance.

[0105] (2) Environmental stability

[0106] To further investigate the environmental stability of the polyurethane-based antibacterial and antifouling coating of the present invention, the following experiments were conducted. The specific steps are as follows:

[0107] a. Using a marker (No. 6821), a 2.5mm × 0.5mm mark was drawn on the surface of the first group of coatings (B1 and G1) prepared from the coatings of Example 2 and Comparative Example 2 at a speed of 4 cm / s at a 45° angle. The proportion of ink shrinkage area to the total ink coating area was then calculated using ImageJ software. The results showed that the ink shrinkage area of ​​B1 was 83.6% of the coating area, and the ink shrinkage area of ​​G1 was 81.0% of the coating area. After wiping off the ink with lint-free paper, the coatings were completely immersed in a hydrochloric acid solution with pH=2. Every 24 hours, the coatings were removed, the surface liquid was wiped off, and the marks were drawn again using the marker. The percentage of ink shrinkage area was calculated using ImageJ software. The change in the percentage of ink shrinkage area was used to determine the change in the coating's anti-fouling performance. After the measurement, the immersion continued until the anti-fouling performance disappeared. The results for B1 are as follows: Figure 5 As shown in a, the G1 result is as follows: Figure 6 As shown in a.

[0108] b. Using a marker (No. 6821), a 2.5mm × 0.5mm mark was drawn on the surface of the second group of coatings (B2 and G2) prepared from the coatings of Example 2 and Comparative Example 2 at a speed of 4 cm / s at a 45° angle. The shrinkage area of ​​the ink on the mark was then calculated using ImageJ software to determine the percentage of the total ink coating area. The results showed that the ink shrinkage area of ​​B2 was 83.6% of the coating area, and the ink shrinkage area of ​​G2 was 81.0% of the coating area. After wiping off the ink with lint-free paper, the coatings were completely immersed in a sodium hydroxide solution with pH=12. Every 24 hours, the coatings were removed, the surface liquid was wiped off, and the marks were drawn on the surface again using the marker. The percentage of ink shrinkage area was calculated using ImageJ software. The change in the percentage of ink shrinkage area was used to determine the change in the coating's anti-fouling performance. Immersion continued until the anti-fouling performance disappeared. The results for B2 were as follows: Figure 5 As shown in b, the G2 result is as follows: Figure 6 As shown in b.

[0109] c. Using a marker (No. 6821), a 2.5mm × 0.5mm line was drawn on the surface of the third group of coatings (B3 and G3) prepared from the coatings of Example 2 and Comparative Example 2 at a speed of 4 cm / s at a 45° angle. The shrinkage area of ​​the ink on the line was then calculated using ImageJ software to determine the percentage of the total ink coating area. The results showed that the ink shrinkage area of ​​B3 was 83.6% of the coating area, and the ink shrinkage area of ​​G3 was 81.0% of the coating area. After wiping the ink off the coating surface with lint-free paper, the coatings were completely immersed in deionized water at pH=7. Every 24 hours, the coatings were removed, the surface liquid was wiped off, and the lines were drawn again using the marker. The percentage of ink shrinkage area was calculated using ImageJ software. The change in the percentage of ink shrinkage area was used to determine the change in the coating's anti-fouling performance. After the measurement, the immersion continued until the anti-fouling performance disappeared. The results for B3 were as follows: Figure 5 As shown in c, the G3 result is as follows: Figure 6 As shown in c.

[0110] Figure 5 The changes in the antifouling performance of the prepared polyurethane-based antibacterial and antifouling coating B after immersion in liquids with different pH values ​​are shown. After 24 h, the percentage of ink shrinkage area of ​​the coating is higher than 75%; after 48 h, the percentage of ink shrinkage area of ​​the coating is higher than 70%; after 72 h, the coating still has more than 55% ink shrinkage area percentage; after 96 h, the coating still has more than 40% ink shrinkage area percentage; after 120 h, the coating loses its antifouling performance. Figure 6 The stain resistance of coating G prepared in Comparative Example 2 was observed to change under different pH conditions after immersion in liquids. After immersion for 48 h, the stain resistance of coating G was not significantly different from that of coating B; after immersion for 72 h, the percentage of ink shrinkage area in the coating was less than 55%; after immersion for 96 h, the coating lost its stain resistance. These results indicate that the introduction of curcumin into the PU-PDMS coating improved the water repellency of PU-PDMS-CUR coating B, demonstrating improved environmental stability, which is consistent with... Figure 2 The water contact angle of the intermediate coating B, at 109.0°, is higher than that of the coating G, which has a water contact angle of 102.4°.

[0111] (3) Self-healing properties against fouling

[0112] 1) Room temperature stain resistance and self-healing properties

[0113] Multiple groups of coatings that lost their anti-fouling properties after environmental stability testing were taken out and placed at room temperature. Every 3 hours, the percentage of ink shrinkage area was measured using a marker (No. 6821) to verify the coating's self-recovery against stains by observing the changes in anti-fouling properties. Figure 7The image shows the antifouling self-healing performance of coating B prepared using the coating from Example 2 at room temperature. After 9 hours at room temperature, the antifouling performance of the coating recovered to more than 80% of its original value, and after 24 hours, the antifouling performance was almost completely restored. Comparative Example 1 showed no antifouling performance; Comparative Example 2 showed no significant difference in antifouling self-healing performance compared to Example 2, but the coating lacked antibacterial properties; Comparative Example 3 showed some antifouling performance, but lacked antifouling self-healing properties.

[0114] 2) High-temperature anti-fouling self-healing performance

[0115] Multiple groups of coatings that lost their anti-fouling properties after environmental stability testing were taken out and placed in a 160°C oven. At regular intervals, they were taken out and the percentage of ink shrinkage area was measured using a marker (No. 6821). The anti-fouling self-recovery property of the coating was verified by the change in anti-fouling properties. Figure 8 The image shows the antifouling self-healing performance of coating B prepared using the coating from Example 2 at high temperatures. After 0.75 h of recovery at 160°C, the antifouling performance of the coating recovered to over 90% of its original value, and after 3 h, the antifouling performance was almost completely recovered. Comparative Example 1 showed no antifouling performance; Comparative Example 2 showed no significant difference in antifouling self-healing performance compared to Example 2, but the coating lacked antibacterial properties; Comparative Example 3 showed some antifouling performance, but lacked antifouling self-healing properties.

[0116] 3. Hardness, water absorption, flexibility, and adhesion

[0117] The pencil hardness of the coating was tested using ASTM D3363-22, the water absorption rate was measured using ASTM D570-22, the flexibility was measured using ASTM D522M-17(2021), and the adhesion was measured using ASTM D3359-23. The coatings (A, B, C, D, E) prepared in this embodiment all had a hardness of 2H and a water absorption rate of less than 0.2%. The flexibility of all coatings was F7 (tested using coating samples coated on tinplate sheets, the samples were wound around shafts with different radii of curvature, and the flexibility level was determined by whether cracking or peeling occurred on the sample surface; the smaller the radius of curvature of the shaft, the larger the number after "F," indicating better coating flexibility; the flexibility level of the shaft that did not show significant phenomena after bending was the coating's flexibility level), indicating good flexibility. The adhesion was rated A1 (the coating was applied to tinplate; a 10 mm × 10 mm sample was cut into 100 1 mm × 1 mm square grids using a blade; debris was cleaned up; 3M transparent tape was firmly adhered to the test area; and the tape was quickly removed by hand. The adhesion rating was evaluated from A0 to A5 based on the area of ​​the coating remaining on the substrate. The larger the remaining area, the smaller the number after "A," indicating better adhesion). This demonstrates good adhesion.

[0118] 4. Antibacterial properties

[0119] First, prepare Luria broth (LB) medium by weighing 7.5 g tryptone, 2.5 g soybean peptone, 2.5 g sodium chloride, and 3.75 g agar powder. Add 500 mL of deionized water, mix well, loosen the cap, and sterilize in an autoclave at 121°C and 131 kPa for 20 min. Tighten the cap upon removal, cool, and store at 4°C for later use. Add *E. coli* or *S. aureus* to the LB medium and incubate overnight at 37°C. Bacterial density was determined using NanoDrop One (Thermo, USA). The bacterial suspension was then diluted to 10⁻¹⁰ with sterile phosphate-buffered saline (PBS). 5 CFU mL -1 The antibacterial rate was determined using the parallel plate counting method. Coating E, prepared according to the polyurethane-based antibacterial and antifouling coating of Example 5, was placed in a 6-well plate. 36 μL of diluted bacterial suspension was dropped onto the sample surface, covered with a coverslip to ensure even distribution, and then incubated at 120 r / min for 24 h in a 37°C constant temperature shaker. After incubation, the co-cultured bacterial suspension on the coating was diluted to 500 CFU / mL with PBS. -1Take 50 μL of the twice diluted bacterial solution and add it to the solid culture medium. Incubate in a 37℃ constant temperature incubator for 10 h and then count the colonies. Perform three parallel samples for each sample.

[0120] The antibacterial rate is calculated using the following formula:

[0121]

[0122] The entire experimental process strictly followed aseptic operation procedures, and all experimental data were measured in triplicate to ensure the accuracy and reliability of the experimental results.

[0123] Figure 9 The images show the antibacterial efficacy against *E. coli* on a blank glass slide, PU coating F, PU-PDMS coating G, PU-CUR coating H, and polyurethane-based antibacterial and antifouling PU-PDMS-CUR coating E. Calculations using the formula show that coating E achieves an antibacterial rate of 95.4% against *E. coli*.

[0124] Figure 10 The images show the anti-Staphylococcus aureus effects of a blank glass slide, PU coating F, PU-PDMS coating G, PU-CUR coating H, and polyurethane-based antibacterial and antifouling PU-PDMS-CUR coating E. Calculations show that coating E achieves a 99.8% antibacterial rate against Staphylococcus aureus.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based polyurethane antibacterial and antifouling coating, characterized in that, The steps are as follows: (1) Dissolve the polyorganosiloxane with a single-terminal hydroxyl group and the polyisocyanate compound in organic solvent I to carry out the first step reaction to obtain reaction solution I; (2) Dissolve curcumin in organic solvent I, add it to reaction solution I, and carry out the second step of the reaction to obtain reaction solution II; (3) Dissolve the bio-based polyol in organic solvent II, add reaction solution II, and carry out the third step of the reaction to obtain the bio-based polyurethane antibacterial and anti-fouling coating.

2. The method for preparing the bio-based polyurethane antibacterial and antifouling coating according to claim 1, characterized in that, In the raw materials of the bio-based polyurethane antibacterial and antifouling coating, the molar ratio of total hydroxyl groups to isocyanate groups in the polyorganosiloxane with single-terminal hydroxyl groups, bio-based polyol, and curcumin is (1-1.2):

1. The hydroxyl content of the polyorganosiloxane with single-terminal hydroxyl groups is 0.2-0.5% of the total hydroxyl groups, the hydroxyl content of curcumin is 2-15.5% of the total hydroxyl groups, and the hydroxyl content of the bio-based polyol is 84-97.5% of the total hydroxyl groups.

3. The method for preparing the bio-based polyurethane antibacterial and antifouling coating according to claim 2, characterized in that, In step (1), the weight-average molecular weight of the polyorganosiloxane with a single-terminal hydroxyl group is 3000-10000; the polyisocyanate compound is a compound containing three or more isocyanate groups; the temperature of the first step reaction is 25-80℃ and the time is 1-3 h.

4. The preparation method of the bio-based polyurethane antibacterial and antifouling coating according to claim 3, characterized in that, The polyisocyanate compound in step (1) is at least one of hexamethylene diisocyanate trimer, hexamethylene diisocyanate biuret, isophorone diisocyanate trimer, and toluene diisocyanate trimer.

5. The method for preparing the bio-based polyurethane antibacterial and antifouling coating according to claim 4, characterized in that, The organic solvent I is at least one of butanone, acetone, isopropanol, and n-hexane; the temperature of the second step reaction is 25-80℃, and the time is 1-6 h.

6. The method for preparing the bio-based polyurethane antibacterial and antifouling coating according to claim 5, characterized in that, The temperature of the third reaction in step (3) is 60-80℃ and the time is 6-16 h.

7. The method for preparing the bio-based polyurethane antibacterial and antifouling coating according to claim 6, characterized in that, In step (3), the bio-based polyol is at least one of castor oil, starch, palm oil and soybean oil, and the organic solvent II is at least one of butanone, dimethyl carbonate and N,N-dimethylformamide.

8. A bio-based polyurethane antibacterial and antifouling coating prepared by the preparation method according to any one of claims 1-7.

9. The application of the bio-based polyurethane antibacterial and antifouling coating of claim 8 in antibacterial and antifouling coatings.

10. The application according to claim 9, characterized in that, The application steps are as follows: the bio-based polyurethane antibacterial and antifouling coating of claim 8 is applied to the surface of the substrate and cured to obtain an antibacterial and antifouling coating.

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