An antibacterial super-hydrophobic coating and its preparation method and application

Abstract

The application relates to the technical field of new materials, and discloses an antibacterial super-hydrophobic coating as well as a preparation method and application thereof. The antibacterial super-hydrophobic coating is prepared by loading an alkyl pyridine salt modified hydrophobic silicon dioxide and a titanium dioxide composite functional layer on electrospun polylactic acid nanofibers through dip coating and nitrogen curing processes. The antibacterial super-hydrophobic coating has both alkyl pyridine salt modified hydrophobic silicon dioxide sterilization and titanium dioxide photocatalytic sterilization double mechanisms, and is prepared by a mild process. The water contact angle of the prepared antibacterial super-hydrophobic coating is greater than or equal to 150 degrees, the sterilization rate is as high as 99.5%, the biocompatibility is excellent, and the thermal stability, acid and alkali stability and mechanical stability are strong. The preparation process is simple, environment-friendly and scalable, and is suitable for medical dressings, food packaging, water treatment membranes and other scenes, and solves the problems of single antibacterial property and insufficient environmental protection of existing coatings.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and more specifically, to an antibacterial superhydrophobic coating, its preparation method, and its application. Background Technology

[0002] Due to its surface water contact angle ≥150° and roll-off angle ≤10°, superhydrophobic coatings have a wide range of applications in self-cleaning, corrosion prevention, antibacterial, and oil-water separation fields. In particular, in scenarios closely related to human health or environmental safety, such as medical dressings, food packaging, and water treatment, higher requirements are placed on the antibacterial properties, environmental friendliness, and biocompatibility of the coatings.

[0003] However, existing antibacterial superhydrophobic coatings mostly rely on a single physical hydrophobic anti-adhesion mechanism, reducing bacterial adhesion solely through surface micro-nano structures, lacking active bactericidal capabilities, and are prone to bacterial residue and growth with long-term use; some coatings containing a single antibacterial component (such as quaternary ammonium salts or silver ions) are prone to causing bacterial resistance, and components such as silver ions pose biotoxicity and environmental accumulation risks; traditional superhydrophobic coatings are often prepared using fluorinated silanes, and fluorine can easily cause environmental pollution; while fluorine-free coatings solve the pollution problem, the substrates are mostly inorganic materials (such as copper mesh or glass) or non-degradable polymers (such as polyurethane), which are difficult to degrade naturally after disposal, causing environmental burden; while existing biodegradable coatings (such as polylactic acid) Biodegradable polymer substrates (such as polylactic acid nanofiber membranes) generally lack an integrated design that combines antibacterial and superhydrophobic properties, failing to meet safety requirements in medical and food contact applications. Some coatings that combine antibacterial and superhydrophobic functions require complex etching, high-temperature sintering, or multi-step chemical modification processes, which not only increase production costs but may also damage the structural integrity of biodegradable raw materials, reducing their environmental value and biocompatibility. Biodegradable polymer substrates (such as polylactic acid nanofiber membranes) prepared by electrospinning have problems such as low crystallinity, high residual solvent content, and insufficient mechanical strength. When directly loading antibacterial and superhydrophobic functional layers, coating peeling and cracking are prone to occur, leading to a rapid decline in superhydrophobic and antibacterial properties and limiting their actual application lifespan.

[0004] Therefore, providing an antibacterial superhydrophobic coating that is actively antibacterial, biodegradable, and possesses high mechanical properties is of significant practical importance. Summary of the Invention

[0005] In view of this, the present invention proposes an antibacterial superhydrophobic coating, its preparation method and application, aiming to solve the problems of the current technology of superhydrophobic coatings, such as single antibacterial mechanism, insufficient effect durability, contradiction between environmental protection and biocompatibility, weak bonding between substrate and functional layer, poor mechanical stability, poor process adaptability and difficulty in large-scale production.

[0006] This invention proposes an antibacterial superhydrophobic coating, comprising the following components in parts by weight: Alkylpyridine salt modifier 18-23 parts, nano silica 35-40 parts, titanium dioxide 18-23 parts, epichlorohydrin 8-12 parts, fluorine-free silane 1.5-3 parts, polylactic acid base 25-35 parts.

[0007] Furthermore, the polylactic acid nanofibers are polylactic acid nanofiber membranes with a pore size of 50-200 nm and a thickness of 50-150 μm.

[0008] Furthermore, the alkylpyridine salt modifier is tetradecyl chloride (or brominated) pyridine.

[0009] Furthermore, the fluorine-free silane is methyltrimethoxysilane; and the polylactic acid substrate is a polylactic acid nanofiber membrane.

[0010] A method for preparing an antibacterial superhydrophobic coating includes the following steps: (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, an alkylpyridinium salt modifier was added, the solution was adjusted to be alkaline, the reaction was stirred, centrifuged, washed and dried to obtain alkylpyridinium salt modified silica; alkylpyridinium salt modified silica was dispersed in ethanol, stirred and epichlorohydrin was added dropwise for reflux reaction, centrifuged, washed and dried to obtain alkylpyridinium salt modified hydrophobic silica; (2) Preparation of polylactic acid substrate: Polylactic acid was dissolved in a mixture of dichloromethane and ethanol to prepare a polylactic acid nanofiber membrane, which was then annealed to obtain a polylactic acid substrate; (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated to form a stable suspension, and then the polylactic acid nanofiber substrate is immersed in the suspension for coating and then taken out and cured under a nitrogen atmosphere to obtain an antibacterial superhydrophobic coating.

[0011] Furthermore, the reaction parameters in step (1) are: temperature 20~100℃; reaction time greater than 1h; reflux time 3~7h; alkaline solution with pH≥8.0; drying is vacuum drying, and the vacuum drying parameters are: drying temperature 55~65℃ and time 3~5h.

[0012] Furthermore, in step (2), the volume ratio of dichloromethane to ethanol in the mixture of dichloromethane and ethanol is 3:1; the polylactic acid nanofiber membrane is prepared by electrospinning process, and the electrospinning process parameters are: voltage 15~20kV, receiving distance 10~20cm, and pushing speed 0.5~1mL / h.

[0013] Furthermore, the annealing process is as follows: the temperature is raised to 70-90°C at a rate of 5-10°C / min, held at that temperature for 1.5-2.5 hours, and then allowed to cool naturally to room temperature.

[0014] Furthermore, the ultrasonic parameters in step (3) are: power 100~500W, temperature 20~50℃, time 20~60min; the immersion time is 5~30s; the curing parameters are: temperature 90~110℃, time 2.5~5.0h.

[0015] The present invention also provides the application of the antibacterial superhydrophobic coating described in the above technical solution in any of the following: ① The application of the aforementioned antibacterial superhydrophobic coating in the preparation of medical dressings; ② The application of the aforementioned antibacterial superhydrophobic coating in food packaging materials; ③ The application of the antibacterial superhydrophobic coating in water treatment membranes; ④ Application of the antibacterial superhydrophobic coating in tableware.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a dual antibacterial mechanism based on composite materials, overcoming the limitations of existing technologies that rely solely on "physical hydrophobicity and anti-adhesion" for single antibacterial action, resulting in more thorough and long-lasting sterilization.

[0017] This invention uses polylactic acid biodegradable substrate, avoiding the environmental residue problems of traditional inorganic substrates (such as copper mesh), and is more suitable for medical and food contact scenarios.

[0018] The preparation process of this invention does not require etching or high-temperature sintering. The combination of dip coating and electrospinning is simple to operate, reduces costs compared to existing technologies, is suitable for large-scale production, and has broad market prospects. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides an antibacterial superhydrophobic coating comprising the following components in parts by weight: 18-23 parts of alkylpyridinium salt modifier, 35-40 parts of nano silica, 18-23 parts of titanium dioxide, 8-12 parts of epichlorohydrin, 1.5-3 parts of fluorine-free silane, and 25-35 parts of polylactic acid base.

[0025] In this invention, the antibacterial superhydrophobic coating is further preferably composed of the following components in parts by weight: 19-23 parts of alkylpyridinium salt modifier, 37-40 parts of nano-silica, 19-23 parts of titanium dioxide, 9-12 parts of epichlorohydrin, 2-3 parts of fluorine-free silane, and 28-35 parts of polylactic acid substrate.

[0026] In this invention, the polylactic acid nanofibers are preferably polylactic acid nanofiber membranes with a pore size of 50-200 nm and a thickness of 50-150 μm, and more preferably with a pore size of 80-200 nm and a thickness of 80-150 μm.

[0027] In this invention, the alkylpyridine salt modifier is tetradecyl-octadecyl chloride (or brominated) pyridine; the titanium dioxide is commercially available titanium dioxide.

[0028] In this invention, alkylpyridinium salts are selected as modifiers to modify silica in the antibacterial superhydrophobic coating. The reaction is mild when using alkylpyridinium salts as modifiers, and can be completed under low temperature and normal pressure conditions. It does not damage the silica crystal structure or the biodegradability of the polylactic acid substrate. It can synergistically construct a superhydrophobic surface with fluorine-free silanes. After modification with alkylpyridinium salts, it can exert its effect by disrupting bacterial cell membranes, improving the bactericidal rate against Escherichia coli and Staphylococcus aureus, and is less likely to induce bacterial resistance. It also easily binds to silica and is not easily desorbed. After thermal and chemical stability tests, the antibacterial and hydrophobic properties show no significant attenuation. Furthermore, alkylpyridinium salt raw materials are readily available, the modification process is simple, no complex equipment is required, it is suitable for large-scale production, and reduces the coating preparation cost.

[0029] In this invention, the fluorine-free silane is methyltrimethoxysilane; the polylactic acid substrate is a polylactic acid nanofiber membrane.

[0030] The present invention adds a fluorine-free silane to the antibacterial superhydrophobic coating. The fluorine-free silane is methyltrimethoxysilane, which has stable chemical properties. When combined with the composite system, it can maintain stable performance in a wide temperature range. It is also fluorine-free and non-toxic, and the residual solvent is easy to remove. The siloxane bond formed after hydrolysis can form a strong chemical bond with the substrate and alkylpyridinium salt modified silica, thereby improving the coating adhesion and supporting friction resistance, thermal and chemical stability.

[0031] The antibacterial superhydrophobic coating of this invention uses a polylactic acid (PLA) substrate, which is a PLA nanofiber membrane. On one hand, PLA is a biodegradable polymer material that can degrade in the natural environment or simulated bodily fluids after disposal, avoiding the environmental residue problems of traditional inorganic / non-degradable substrates. It forms a completely environmentally friendly system with fluorine-free silanes and modified silica, meeting the safety requirements of medical and food packaging. On the other hand, after electrospinning and annealing, a continuous network structure is formed, improving tensile strength and providing a stable mechanical framework for the coating, preventing brittleness or coating peeling during dip coating and friction use. Furthermore, PLA locks in functional layers through its porous structure. The coating ensures superhydrophobicity with WCA ≥ 150° while achieving long-term stability of dual antibacterial properties. It also improves coating uniformity and works synergistically with the functional layer of the coating to achieve environmental protection. It can naturally degrade after disposal, with no environmental burden, and is suitable for high-end environmental protection needs such as medical and food packaging. In addition, polylactic acid is easily soluble in a mixture of dichloromethane and ethanol, and can be precisely prepared into micro-nano structures through electrospinning. Its thermal stability is suitable for low-temperature annealing without damaging its own degradation structure and mechanical properties. The high specific surface area and porous structure of its nanofiber membrane can provide sufficient attachment sites for modified silica and fluorine-free silanes, which helps to uniformly distribute the superhydrophobic micro-nano structure and antibacterial components.

[0032] A method for preparing an antibacterial superhydrophobic coating includes the following steps: (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, an alkylpyridinium salt modifier was added, the solution was adjusted to be alkaline, the reaction was stirred, centrifuged, washed and dried to obtain alkylpyridinium salt modified silica; alkylpyridinium salt modified silica was dispersed in ethanol, stirred and epichlorohydrin was added dropwise for reflux reaction, centrifuged, washed and dried to obtain alkylpyridinium salt modified hydrophobic silica; (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid is dissolved in a mixture of dichloromethane and ethanol to prepare a polylactic acid nanofiber membrane, which is then annealed to obtain a polylactic acid nanofiber substrate. (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica is dispersed in ethanol, stirred and ultrasonically treated to form a stable suspension. The polylactic acid nanofiber substrate is then immersed in the suspension for coating and then taken out and cured under a nitrogen atmosphere to obtain an antibacterial superhydrophobic coating.

[0033] (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, alkylpyridinium was added, the solution was adjusted to be alkaline, the reaction was stirred, centrifuged, washed and dried to obtain alkylpyridinium salt modified silica; alkylpyridinium salt modified silica was dispersed in ethanol, stirred and epichlorohydrin was added dropwise for reflux reaction, centrifuged, washed and dried to obtain alkylpyridinium salt modified hydrophobic silica; In this invention, the reaction parameters in step (1) are preferably: temperature 20~100℃; reaction time greater than 1h, more preferably temperature 50~70℃ and time 2.0~2.5h; the reflux time is preferably 3~7h, more preferably 4~6h; the drying is vacuum drying, and the vacuum drying parameters are preferably: drying temperature 50~70℃ and time 3~5h, more preferably drying temperature 58~65℃ and time 3.5~5h.

[0034] In this invention, the drying method adopts vacuum drying, which can effectively avoid high-temperature decomposition of materials, quickly remove ethanol solvent, preserve the integrity of the modified structure, and the vacuum environment is an oxygen-free environment, which reduces the self-depletion of silica photocatalysis and extends the antibacterial life of the coating.

[0035] In this invention, epichlorohydrin is selectively added to the antibacterial superhydrophobic coating. Epichlorohydrin can be regarded as a crosslinking agent, which reacts with the hydroxyl groups on the surface of nano-silica through ring-opening reaction to form stable chemical bonds, preventing the desorption of antibacterial components. During the crosslinking process, long alkyl chains are introduced simultaneously, and it synergistically optimizes the surface energy of the coating with titanium dioxide, which helps to form superhydrophobic properties. Moreover, epichlorohydrin can react efficiently in the ethanol-supported system without damaging the silica crystal structure or the biodegradability of polylactic acid. There are no side reactions with other components, and it does not affect subsequent reactions. The raw materials are inexpensive and widely available, and the modification process does not require complex equipment, making it suitable for large-scale production.

[0036] (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid is dissolved in a mixture of dichloromethane and ethanol to prepare a polylactic acid nanofiber membrane, which is then annealed to obtain a polylactic acid nanofiber substrate. In this invention, the volume ratio of dichloromethane to ethanol in the mixture of dichloromethane and ethanol in step (2) is 3:1; the polylactic acid nanofiber membrane is prepared by electrospinning process, and the electrospinning process parameters are preferably: voltage 15~20kV, receiving distance 10~20cm, and pushing speed 0.5~1mL / h, and more preferably voltage 16~20kV, receiving distance 13~20cm, and pushing speed 0.7~1mL / h.

[0037] In this invention, the annealing treatment in step (2) is preferably: heating to 70-90°C at a rate of 5-10°C / min, holding for 1.5-2.5h, and then naturally cooling to room temperature; more preferably, heating to 75-90°C at a rate of 6-10°C / min, holding for 2-2.5h, and then naturally cooling to room temperature.

[0038] In this invention, the polylactic acid nanofiber membrane is prepared using an electrospinning process. By adjusting its parameters, the pore size and thickness of the fiber membrane can be flexibly controlled to meet different application scenarios and precisely construct polylactic acid nanofiber membranes with consistent pore size and uniform thickness. This results in abundant pores and a high specific surface area, providing stable adhesion sites for modified silica, strengthening the adhesion between the coating and the substrate, preventing coating detachment, and promoting the formation of hydrophobic micro-nano structures. The room temperature spinning and low temperature annealing conditions in the process are mild and do not damage the biodegradable structure of polylactic acid. Furthermore, the coating exhibits low cytotoxicity and can be applied to medical and food contact applications. The continuous spinning process is highly efficient, requires moderate equipment, and can produce substrates with good uniformity in batches. Compared with etching, template methods, and other processes, it reduces production costs and generates no pollutants, meeting environmental protection requirements. Moreover, the fibers form a continuous network structure after spinning, and the crystallinity and tensile strength are improved after annealing, solving the problem of brittleness in pure polylactic acid fiber membranes and ensuring the mechanical stability of the coating under dipping, friction, and other scenarios.

[0039] In this invention, the annealing is a thermal annealing treatment of the polylactic acid nanofiber membrane, a key post-processing step after electrospinning to prepare the substrate. It optimizes the substrate structure through gentle heating and holding, without altering the chemical properties of the raw materials, only controlling the crystal morphology and mechanical properties of polylactic acid (PLA). The annealing treatment can improve the crystallinity of the PLA nanofiber membrane, enhance the mechanical strength and toughness of the substrate, and prevent brittleness during subsequent dip coating and use. It can also completely remove residual dichloromethane and ethanol solvents from the spun membrane, preventing solvent residues from affecting the adhesion between the functional layer and the substrate, or causing bubbles and pinholes in the coating. Furthermore, it can optimize the pore size uniformity of the fiber membrane, maintaining the target pore size and providing stable micro / nanostructure support for the uniform adhesion of the functional layer, ensuring the consistency of superhydrophobic and antibacterial properties.

[0040] (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated to form a stable suspension, and then the polylactic acid nanofiber substrate is immersed in the suspension for coating and then taken out and cured under a nitrogen atmosphere to obtain an antibacterial superhydrophobic coating.

[0041] In this invention, the ultrasonic parameters in step (3) are preferably: power 100~500W, temperature 20~50℃, time 20~60min, and more preferably power 180~300W, temperature 30~50℃, time 35~40min; the immersion time is preferably 5~30s, and more preferably 10~20s; the curing parameters are preferably: temperature 90~110℃, time 2.5~5.0h, and more preferably temperature 95~110℃, time 3~3.5h.

[0042] In this invention, the curing and drying method under a nitrogen atmosphere can effectively isolate oxygen, avoid excessively rapid hydrolysis of the fluorine-free silane methyltrimethoxysilane, ensure the density of the superhydrophobic coating, and the low drying temperature can prevent polylactic acid degradation and ensure the stability of the material.

[0043] In this invention, the purpose of the ultrasonic treatment is to uniformly disperse the hydrophobic silica in the ethanol solution, avoiding agglomeration that would lead to uneven structure of the composite functional layer; nitrogen atmosphere curing can inhibit the excessively rapid hydrolysis of silanes and ensure the compactness of the composite functional layer.

[0044] The present invention also provides the application of the antibacterial superhydrophobic coating described in the above technical solution in any of the following: ① The application of the aforementioned antibacterial superhydrophobic coating in the preparation of medical dressings; ② The application of the aforementioned antibacterial superhydrophobic coating in food packaging materials; ③ The application of the antibacterial superhydrophobic coating in water treatment membranes; ④ Application of the antibacterial superhydrophobic coating in tableware.

[0045] In this invention, the medical dressing is used as a surface coating for wound dressings to prevent bacterial infection and achieve self-cleaning, reducing the frequency of dressing changes; the food packaging is a self-cleaning antibacterial packaging film to extend the shelf life of fresh foods (such as meat, fruits and vegetables); the water treatment membrane is used for surface modification of wastewater purification membranes to prevent bacterial adhesion and clogging, improving membrane separation efficiency and service life; the tableware is coated on the surface of ceramic and stainless steel tableware to achieve antibacterial self-cleaning and reduce cleaning difficulty.

[0046] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0047] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1 Raw materials: 35 parts nano silica, 19 parts titanium dioxide, 19 parts hexadecyl pyridine chloride, 9 parts epichlorohydrin, 2 parts fluorine-free silane, 28 parts polylactic acid substrate, wherein the fluorine-free silane is methyltrimethoxysilane, and the polylactic acid nanofibers have a pore size of 80 nm and a thickness of 80 μm.

[0049] Preparation method: (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, hexadecyl pyridine chloride was added, the pH of the solution was adjusted to 12 with NaOH, stirred at 50°C for 2 h, centrifuged and dried, dispersed in ethanol, epichlorohydrin was added dropwise and refluxed for 4 h, centrifuged and washed, and vacuum dried at 58°C to obtain alkylpyridinium salt modified hydrophobic silica; (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid was dissolved in a mixture of dichloromethane and ethanol in a volume ratio of 3:1. Polylactic acid nanofiber membrane was prepared under electrospinning process with voltage of 16kV, receiving distance of 13cm and pushing speed of 0.7mL / h. The temperature was raised to 75℃ at a rate of 6℃ / min and held for 2h. Then it was naturally cooled to room temperature to obtain polylactic acid nanofiber substrate. (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated at 180W and 30℃ for 35min to form a stable suspension. The polylactic acid nanofiber substrate is then immersed in the suspension for 10s and taken out. It is then cured at 95℃ in a nitrogen atmosphere for 3h to obtain an antibacterial superhydrophobic coating.

[0050] Example 2 Raw materials: 35 parts nano silica, 21 parts titanium dioxide, 21 parts hexadecyl pyridine bromide, 10 parts epichlorohydrin, 2.5 parts fluorine-free silane, and 30 parts polylactic acid substrate, wherein the fluorine-free silane is methyltrimethoxysilane, and the polylactic acid nanofibers have a pore size of 120 nm and a thickness of 100 μm.

[0051] Preparation method: (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, hexadecylpyridine bromide was added, the pH of the solution was adjusted to 11 with NaOH, stirred at 60°C for 2 h, centrifuged and dried, dispersed in ethanol, epichlorohydrin was added dropwise and refluxed for 5 h, centrifuged and washed, and then vacuum dried at 60°C to obtain alkylpyridinium salt modified hydrophobic silica; (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid was dissolved in a mixture of dichloromethane and ethanol in a volume ratio of 3:1. Polylactic acid nanofiber membrane was prepared under electrospinning process with voltage of 18kV, receiving distance of 15cm and pushing speed of 0.8mL / h. The temperature was raised to 80℃ at a rate of 8℃ / min and kept at the temperature for 2h. Then it was naturally cooled to room temperature to obtain polylactic acid nanofiber substrate. (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated at 240W and 40℃ for 37min to form a stable suspension. The polylactic acid nanofiber substrate is then immersed in the suspension for 15s and taken out. It is then cured at 100℃ in a nitrogen atmosphere for 3h to obtain an antibacterial superhydrophobic coating.

[0052] Example 3 Raw materials: 35 parts nano silica, 23 parts titanium dioxide, 23 parts octadecyl pyridine chloride, 12 parts epichlorohydrin, 3 parts fluorine-free silane, 35 parts polylactic acid substrate, wherein the fluorine-free silane is methyltrimethoxysilane, and the polylactic acid nanofibers have a pore size of 200 nm and a thickness of 150 μm.

[0053] Preparation method: (1) Preparation of alkylpyridine modified hydrophobic silica: Silica was dispersed in an aqueous solution, octadecylpyridine chloride was added, the pH of the solution was adjusted to 12 with NaOH, stirred at 70°C for 2.5 h, centrifuged and dried, dispersed in ethanol, epichlorohydrin was added dropwise and refluxed for 6 h, centrifuged and washed, and vacuum dried at 60°C to obtain alkylpyridine salt modified hydrophobic silica; (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid was dissolved in a mixture of dichloromethane and ethanol in a volume ratio of 3:1. Polylactic acid nanofiber membrane was prepared under electrospinning process with voltage of 20kV, receiving distance of 20cm and pushing speed of 1mL / h. The temperature was raised to 90℃ at a rate of 10℃ / min and held for 2.5h. Then it was naturally cooled to room temperature to obtain polylactic acid nanofiber substrate. (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated at 300W and 50℃ for 40min to form a stable suspension. The polylactic acid nanofiber substrate is then immersed in the suspension for 20s and taken out. It is then cured at 110℃ in a nitrogen atmosphere for 3h to obtain an antibacterial superhydrophobic coating.

[0054] Performance testing: (1) The water contact angle (°) of the antibacterial superhydrophobic coating described in Examples 1-3 was tested at room temperature using a contact angle measuring instrument (DSA30). The test was conducted in accordance with (GB / T 30693-2014 "Measurement of the contact angle between plastic film and water" and GB / T 30447-2013 "Method for measuring the contact angle of nanofilms").

[0055] (2) The water roll-off angle (°) of the antibacterial superhydrophobic coating described in Examples 1-3 was measured using a contact angle measuring instrument (DSA30) and the tilt method according to the test standard (ISO 19403-7:2017 "Hydrophilicity of paints and varnishes - Part 7: Measurement of contact angle (roll-off angle) on an inclined platform").

[0056] (3) The Escherichia coli bactericidal rate of the antibacterial superhydrophobic coating described in Examples 1-3 was determined by colony counting method, with an initial concentration of 10. 7 CFU / mL, the test was conducted according to (GB / T 21866-2008 "Determination of Antibacterial Properties and Antibacterial Effects of Antibacterial Coatings (Films)").

[0057] (4) The Staphylococcus aureus bactericidal rate of the antibacterial superhydrophobic coatings described in Examples 1-3 was determined by colony counting method, with an initial concentration of 10. 7 CFU / mL, the test was conducted according to (GB / T 21866-2008 "Determination of Antibacterial Properties and Antibacterial Effects of Antibacterial Coatings (Films)").

[0058] (5) The tensile strength (MPa) of the antibacterial superhydrophobic coating described in Examples 1-3 was tested using a universal testing machine at a tensile rate of 5 mm / min. The test was conducted in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0059] (6) The tensile elongation at break (%) of the antibacterial superhydrophobic coating described in Examples 1-3 was determined by using a universal testing machine and recording the elongation at break. The test was conducted in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0060] (7) The thermal stability of the antibacterial superhydrophobic coating described in Examples 1-3 was tested by oven constant temperature treatment (80℃ / 2h) and the water contact angle was tested according to (GB / T 30693-2014 "Measurement of water contact angle of plastic film" and GB / T 30447-2013 "Method for measuring contact angle of nanofilm").

[0061] (8) The acid resistance of the antibacterial superhydrophobic coating described in Examples 1-3 is tested by soaking the coating in a 3.5% NaCl solution with the pH adjusted to 2 for 12 hours and then drying it. The test is based on GB / T 30693-2014 "Measurement of the contact angle between plastic film and water" and GB / T 30447-2013 "Method for measuring the contact angle of nanofilm".

[0062] (9) The alkali resistance of the antibacterial superhydrophobic coating described in Examples 1-3 is tested by soaking the coating in a 3.5% NaCl solution with the pH adjusted to 12 for 12 hours and then drying it. The test is based on GB / T 30693-2014 "Measurement of the contact angle between plastic film and water" and GB / T 30447-2013 "Method for measuring the contact angle of nanofilm".

[0063] (10) The abrasion resistance of the antibacterial superhydrophobic coating described in Examples 1-3 was tested by rubbing with 50g load and 180-grit sandpaper, moving 10cm each time, and after 10 cycles, the water contact angle was measured. The test was based on GB / T 30693-2014 "Measurement of the contact angle between plastic film and water" and GB / T 30447-2013 "Method for measuring the contact angle of nanofilm".

[0064] (11) The in vitro cytotoxicity level of the antibacterial superhydrophobic coating described in Examples 1-3 was determined by the L929 cell culture method, and the test was conducted according to (GB / T 16886.5—2017 "Biological Evaluation of Medical Devices Part 5: In Vitro Cytotoxicity Tests").

[0065] (12) The residual solvent content of the antibacterial superhydrophobic coating described in Examples 1-3 was detected by gas chromatography. The test was based on GB / T 5009.26—2016 "National Food Safety Standard: Determination of Residual Solvents in Food" and GB / T 16886.7—2015 "Detection Approach for Residual Solvents in Medical Devices".

[0066] (13) The biodegradation rate of the antibacterial superhydrophobic coating described in Examples 1-3 was calculated by gravimetric method, and the test was based on (GB / T 19277.1—2011 "Determination of the final aerobic biodegradation capacity of materials under controlled composting conditions by means of determination of released carbon dioxide - Part 1: General method").

[0067] The performance test results of the antibacterial superhydrophobic coatings obtained in Examples 1-3 are shown in Table 1 below: Table 1. Performance test results of the antibacterial superhydrophobic coatings obtained in Examples 1-3

[0068] As shown in Table 1, with the increase of substrate pore size, ultrasonic power, and immersion time, the water contact angle (WCA) gradually increases, reaching over 163° in Examples 2-3, meeting the requirements for high-efficiency superhydrophobicity. All three exhibit a sterilization rate ≥99.5%. Example 3, with its higher proportion of hydrophobic silica and denser coating, demonstrates the best sterilization effect and eliminates the risk of drug resistance due to its dual antibacterial mechanism. Example 2 shows the best overall coating performance (optimal synergy between tensile strength and elongation at break). Example 3, with its high annealing temperature (90℃) and high crystallinity, has the highest tensile strength but a slightly lower elongation at break. All three demonstrate excellent thermal stability, acid and alkali resistance, and frictional stability. Example 3, with its high curing temperature (110℃) and stronger functional layer bonding, exhibits slightly better stability than the other two. Furthermore, all antibacterial superhydrophobic coatings prepared in Examples 1-3 meet medical and food-grade standards, with residual solvent content far below the safety threshold, and their biodegradability meets environmental protection requirements.

[0069] In summary, in this invention, alkylpyridinium salt-modified hydrophobic silica, titanium dioxide, and methyltrimethoxysilane are cross-linked through siloxane bonds to form a dense composite functional layer. The alkylpyridinium salt-modified hydrophobic silica and titanium dioxide provide dual antibacterial activity, while methyltrimethoxysilane enhances the adhesion between the coating and the substrate. During this process, the hydroxyl groups on the surface of the modified silica undergo a condensation reaction with the silanol groups generated by the hydrolysis of methyltrimethoxysilane, forming a cross-linked network structure and constituting a dense composite functional layer, ultimately resulting in an antibacterial superhydrophobic coating.

[0070] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is determined by the appended claims.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An antibacterial superhydrophobic coating, characterized in that, The components comprise the following parts by weight: Alkylpyridine salt modifier 18-23 parts, nano silica 35-40 parts, titanium dioxide 18-23 parts, epichlorohydrin 8-13 parts, fluorine-free silane 1.5-3 parts, polylactic acid base 25-35 parts.

2. The antibacterial superhydrophobic coating according to claim 1, characterized in that, The alkylpyridinium salt modifier is tetradecyl-octadecylpyridinium salt; the titanium dioxide is commercially available titanium dioxide.

3. The antibacterial superhydrophobic coating according to claim 1, characterized in that, The polylactic acid nanofibers are polylactic acid nanofiber membranes with a pore size of 50-200 nm and a thickness of 50-150 μm.

4. The antibacterial superhydrophobic coating according to claim 1, characterized in that, The fluorine-free silane is methyltrimethoxysilane; the polylactic acid substrate is a polylactic acid nanofiber membrane.

5. A method for preparing an antibacterial superhydrophobic coating according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of alkylpyridinium salt modified hydrophobic silica: Silica was dispersed in an aqueous solution, an alkylpyridinium salt modifier was added, the solution was adjusted to be alkaline, the reaction was stirred, centrifuged, washed and dried to obtain alkylpyridinium salt modified silica; alkylpyridinium salt modified silica was dispersed in ethanol, stirred and epichlorohydrin was added dropwise for reflux reaction, centrifuged, washed and dried to obtain alkylpyridinium salt modified hydrophobic silica; (2) Preparation of polylactic acid nanofiber substrate: Polylactic acid is dissolved in a mixture of dichloromethane and ethanol to prepare a polylactic acid nanofiber membrane, which is then annealed to obtain a polylactic acid nanofiber substrate. (3) Constructing a composite coating: The alkylpyridinium salt modified hydrophobic silica, titanium dioxide and methyltrimethoxysilane are dispersed in ethanol, stirred and ultrasonically treated to form a stable suspension, and then the polylactic acid nanofiber substrate is immersed in the suspension for coating and then taken out and cured under a nitrogen atmosphere to obtain an antibacterial superhydrophobic coating.

6. The method for preparing an antibacterial superhydrophobic coating according to claim 5, characterized in that, The stirring reaction parameters in step (1) are: temperature 20~100℃, reaction time greater than 1h; reflux time 3~7h; alkaline solution with pH≥8.0; and drying is vacuum drying with the following parameters: drying temperature 55~65℃, time 3~5h.

7. The method for preparing an antibacterial superhydrophobic coating according to claim 5, characterized in that, In step (2), the volume ratio of dichloromethane to ethanol in the mixture of dichloromethane and ethanol is 3:1; the polylactic acid nanofiber membrane is prepared by electrospinning process, and the electrospinning process parameters are: voltage 15~20kV, receiving distance 10~20cm, and pushing speed 0.5~1mL / h.

8. The method for preparing an antibacterial superhydrophobic coating according to claim 5, characterized in that, The annealing process is as follows: the temperature is increased to 70-90℃ at a rate of 5-10℃ / min, held at that temperature for 1.5-2.5h, and then allowed to cool naturally to room temperature.

9. The method for preparing an antibacterial superhydrophobic coating according to claim 5, characterized in that, The ultrasonic parameters in step (3) are: power 100~500W, temperature 20~50℃, time 20~60min; the immersion time is 5~30s; the curing parameters are: temperature 90~110℃, time 2.5~5.0h.

10. An application of the antibacterial superhydrophobic coating as described in any one of claims 1-4, characterized in that, The antibacterial superhydrophobic coating is used in any of the following applications: ① The application of the aforementioned antibacterial superhydrophobic coating in the preparation of medical dressings; ② The application of the aforementioned antibacterial superhydrophobic coating in food packaging materials; ③ The application of the antibacterial superhydrophobic coating in water treatment membranes; ④ The application of the antibacterial superhydrophobic coating in tableware.

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