Mildew-proof and antibacterial bio-based silica gel material and preparation method thereof

Abstract

The application discloses a mildew-proof and antibacterial bio-based silica gel material, which is composed of a bio-based silica rubber polymer matrix and a nano filler with surface chemically anchored polyphenol molecules; wherein the nano filler comprises an inorganic nano filler core and a polyphenol molecule shell layer anchored on the surface of the inorganic nano filler core through a covalent bond, the polyphenol molecule shell layer is formed by ring-opening reaction of phenolic hydroxyl groups on natural polyphenol compounds with epoxy groups pre-grafted on the surface of the inorganic nano filler core, and the natural polyphenol compound molecules are mutually isolated; the epoxy groups pre-grafted on the surface of the inorganic nano filler core are provided by a silane coupling agent containing an epoxy group; and the nano filler is uniformly dispersed in the polymer matrix; on the polyphenol molecule shell layer, antibacterial metal ions are further chelated through residual phenolic hydroxyl groups not participating in the ring-opening reaction, forming a metal-polyphenol coordination network outer layer.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a mildew-resistant and antibacterial bio-based silicone material and its preparation method. Background Technology

[0002] Silicone rubber, with its excellent flexibility, resistance to high and low temperatures, chemical stability, and food-grade safety, has become a star material widely used in the field of daily consumer goods. From kitchenware (baking molds, ice cube trays, spatulas, sealing lids), baby products (baby bottles, nipples, teethers, baby food spoons), personal care products (makeup puffs, toothbrushes, razor handles) to electronic product cases, wearable device straps, water bottle sealing rings, and other everyday consumer products made of silicone have penetrated into all aspects of modern life.

[0003] However, with increasing consumer health awareness and increasingly stringent global environmental regulations, the requirements for microbial safety in everyday consumer products that come into close contact with food and the human body are constantly rising. These products made of silicone rubber, exposed to humid environments with residual nutrients, are highly susceptible to mold and bacteria growth. This not only affects the product's appearance and lifespan, but the mycotoxins and pathogens produced by their metabolism also pose a potential threat to consumer health. Therefore, developing silicone materials that are both highly effective in antibacterial and antifungal properties while remaining safe and environmentally friendly has become an urgent need for the industry. This requires material modification technologies that not only endow silicone with broad-spectrum and long-lasting antibacterial and antifungal properties, but also ensure its biocompatibility in food and skin contact scenarios, while not affecting the appearance, feel, and mechanical properties of silicone products.

[0004] In existing technologies, the antibacterial and antifungal modification of silicone materials mainly employs methods such as surface coating, adding silver-based antibacterial agents, or organic antifungal agents. Specifically, surface coating technology applies an antibacterial layer to the silicone surface by spraying or impregnation, and its core advantage lies in its simple process and significant initial effect. However, the low surface energy of silicone leads to poor coating adhesion, making it prone to peeling off during daily use, such as friction, washing, and high-temperature sterilization. More importantly, the peeled antibacterial particles may migrate into food or be absorbed by human skin, raising safety concerns. In addition, silver-based antibacterial agents (such as silver ions and silver nanoparticles) are currently the most mainstream solution for silicone products that come into contact with infants and food. They exert their antibacterial effect by releasing silver ions to disrupt the cell membranes of microorganisms. However, silver-based antibacterial agents have significant limitations: they are highly effective against bacteria but have weak inhibitory ability against molds, and their broad-spectrum activity is insufficient. Furthermore, the EU and other regions have imposed stricter regulations on the use of nano-silver in food contact materials; excessive migration may pose potential health risks to humans (especially infants), and the high price of silver powder significantly increases product costs. Traditional organic antifungal agents (such as OBPA and carbendazim) have excellent mold-inhibiting effects, but their high toxicity has led to restrictions or bans on their use in food contact materials and baby products under environmental regulations such as RoHS and REACH. In summary, the core bottleneck of existing technologies lies in the difficulty of simultaneously ensuring high-efficiency antibacterial and antifungal activity while maintaining biocompatibility, durability, and cost control.

[0005] Therefore, there is an urgent need to develop a novel antibacterial and antifungal modification strategy for silicone to overcome the limitations of existing technologies. This invention's strategy is based on bio-based antibacterial agents (such as chitosan and plant extracts), endowing silicone with broad-spectrum antibacterial and antifungal capabilities while ensuring high biocompatibility. Simultaneously, functionalized nanofillers (such as nano-zinc oxide, nano-silica, and nano-titanium dioxide) are introduced, utilizing their high specific surface area, functionalizability, and excellent compatibility with the silicone matrix to achieve synergistic dispersion and antibacterial effects of the bio-based antibacterial agents, while simultaneously improving the mechanical properties and durability of the silicone. By constructing a "bio-based antibacterial agent-functionalized nanofiller" composite system, a bio-based silicone material with four functions—highly efficient antibacterial and antifungal properties, biocompatibility, mechanical enhancement, and cost control—is ultimately developed to meet the diversified needs of the everyday consumer goods market. Summary of the Invention

[0006] The purpose of this invention is to provide a mildew-resistant and antibacterial bio-based silicone material and its preparation method.

[0007] To achieve the above objectives, the solution of the present invention is: A bio-based silicone material with anti-mildew and antibacterial properties, the bio-based silicone material being composed of a polymer matrix and nanofillers with surface chemically anchored polyphenol molecules; wherein the nanofillers include an inorganic nanofiller core and a polyphenol molecule shell anchored to the surface of the inorganic nanofiller core.

[0008] Preferably, the amount of the surface chemically anchored polyphenol molecules nanofiller added to the polymer matrix accounts for 1% to 30% of the mass of the polymer matrix.

[0009] Preferably, the natural polyphenol compound is selected from tannic acid or gallic acid.

[0010] Preferably, the inorganic nanofiller core is selected from either nano-silica or nano-calcium carbonate.

[0011] Preferably, the polymer matrix is ​​bio-based silicone rubber.

[0012] A method for preparing antifungal and antibacterial bio-based silicone material includes the following steps: (1) An inorganic nanofiller with a surface rich in epoxy groups is prepared by silanizing an unmodified inorganic nanofiller with an epoxy-containing silane coupling agent in an organic solvent. (2) The inorganic nanofiller with surface rich in epoxy groups obtained in step (1) is dispersed in a mixed solvent composed of a non-protic polar solvent and a protic solvent to obtain a suspension of inorganic nanofiller with surface rich in epoxy groups. (3) Add a natural polyphenol compound solution to the suspension of inorganic nanofiller with surface rich in epoxy groups obtained in step (2), and then add a catalyst to carry out a heating reaction to obtain an inorganic nanofiller with a polyphenol molecular shell. (4) Disperse the inorganic nanofiller containing polyphenol molecular shell obtained in step (3) in a solution containing antibacterial metal ions, and then continue to stir the mixture at room temperature to obtain an inorganic nanofiller containing a metal-polyphenol coordination network outer layer. (5) On the open mill, the bio-based silicone rubber is wrapped around the front roller. After the raw rubber is evenly wrapped around the roller and forms a smooth accumulation, the mixing begins. The formulation additives are added in sequence, in small amounts, and in batches: hydroxyl silicone oil, precipitated silica, and inorganic nanofiller containing polyphenol molecular shell prepared in step (4). After all the additives are added, the components are fully mixed by continuously cutting left and right and making triangular wraps. After the filler is evenly dispersed, the vulcanizing agent is added last. The mixture is quickly mixed, passed through a thin sheet, and then the compound is obtained. The compound is placed on a flat vulcanizing machine for a first-stage vulcanization after being left to stand at room temperature. The sheet obtained from the first-stage vulcanization is subjected to a second-stage vulcanization. After natural cooling, the anti-mildew and antibacterial bio-based silicone material can be prepared.

[0013] Preferably, the aprotic polar solvent is N,N-dimethylformamide; and the protic solvent is water.

[0014] Preferably, the heating reaction temperature in step (3) is 50-100°C, and the heating reaction time is 2-12 hours.

[0015] Preferably, the catalyst in step (3) is triethylamine.

[0016] Preferably, the vulcanizing agent in step (5) is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0017] The principle of the anti-mildew and antibacterial bio-based silicone material and its preparation method provided by this invention is as follows: The provided antifungal and antibacterial bio-based silicone material is composed of a bio-based silicone rubber polymer matrix and nanofillers with surface chemically anchored polyphenol molecules. The surface chemically anchored polyphenol nanofillers endow the silicone material with excellent antifungal and antibacterial properties. Specifically, the surface chemically anchored polyphenol nanofillers designed in this invention can be synthesized through the following two steps: Step 1: Surface chemical modification of the original inorganic nanofillers. We select silane coupling agents containing both hydrolyzable alkoxy groups and highly reactive epoxy groups in their molecular structure as "molecular bridges." Under controlled conditions (anhydrous organic solvent, inert atmosphere, heating), the alkoxy group at one end of the silane coupling agent undergoes a hydrolysis-condensation reaction with the abundant active hydroxyl groups (-OH) on the surface of the nanofiller, thereby anchoring the coupling agent molecules to the filler surface in the form of covalent bonds. The epoxy groups at the other end of the coupling agent molecules are completely preserved and exposed. Thus, the originally inert surface of the nanofiller is "pre-armed" with a layer of high-density, uniformly distributed, and chemically active epoxy groups. This layer of epoxy groups acts like millions of highly sensitive "traps" or "capture nets" on the surface of the filler, fully preparing for the next step of efficiently and selectively capturing polyphenol molecules.

[0018] Step 2: The pre-treated epoxy nanofiller is dispersed in a specially formulated mixed solvent system. This mixed solvent is typically a precisely proportioned mixture of a non-protic polar solvent (such as N,N-dimethylformamide, DMF) with excellent polyphenol solubility but inertness to epoxy groups, and a small amount of a protic solvent (such as water). Then, under vigorous stirring and inert gas protection, the solution containing the natural polyphenol compound is added dropwise to the filler suspension at an extremely slow and controlled rate. When individual, free polyphenol molecules move randomly in the solution and diffuse to the short-range of the filler surface, their highly reactive phenolic hydroxyl groups immediately collide with the high-density epoxy groups on the surface. Under the action of a catalyst (such as a tertiary amine), the phenolic hydroxyl group, acting as a nucleophile, selectively attacks the less sterically hindered carbon atom on the epoxy group, resulting in a highly efficient and irreversible SN2 ring-opening reaction, forming a stable ether bond (-COC-), and regenerating a new hydroxyl group. Through this reaction, a large polyphenol molecule is "clicked" and firmly "locked" onto the filler surface in the form of covalent bonds.

[0019] Through the above two steps, we obtained a novel functionalized nanofiller with a well-defined "core-shell" structure at the individual nanoparticle scale. Its rigid inorganic core (such as nano-silica) provides mechanical support and reinforcement; the surface-covalently anchored polyphenol molecular shell plays a dual key role: First, as a highly efficient "interfacial compatibilizer," the abundant organic functional groups on the surface of the polyphenol molecular shell greatly reduce the surface energy of the filler particles, resulting in strong interfacial interactions (such as hydrogen bonds and chain entanglement) between the filler and the hydrophobic polymer matrix (such as silica gel raw material). This allows the filler to be uniformly dispersed in the matrix in the form of native nanoparticles, avoiding stress concentration and performance degradation caused by agglomeration.

[0020] Secondly, the polyphenol molecule shell serves as a high-density, flexibly customizable "universal secondary reaction platform." Anchored on the surface, the polyphenol molecules still retain a large number of free phenolic hydroxyl groups (including catechol, pyrogallol, etc.) with varying activities that did not participate in the first-step ring-opening reaction. These phenolic hydroxyl groups possess abundant chemical reactivity, especially their strong ability to chelate metal ions. Therefore, simply adding the modified nanofiller of this invention to a container containing target metal ions (such as Zn²⁺ with antibacterial properties) is sufficient. + Cu² + or Fe³ with special optoelectronic functions + Tb³ +By simply stirring in an aqueous or alcoholic solution (e.g., at room temperature to under mild heating), an extremely thin, dense, and robust metal-polyphenol coordination network (MPN) layer can be generated in situ on the outermost layer of the nanofiller. This allows for the one-step acquisition of super-integrated particles that integrate multiple functions such as nano-reinforcement, interfacial compatibility, long-lasting antibacterial properties, antioxidant properties, and photothermal response. Furthermore, since the polyphenol molecules themselves are covalently anchored, the MPN layer formed after chelating metal ions is also stable and non-migrating, thus providing an unbreakable structural foundation for achieving the "non-migrating" long-lasting function of the final composite material product.

[0021] The advantages of the anti-mildew and antibacterial bio-based silicone material and its preparation method provided by this invention are as follows: (1) The surface chemical anchoring of polyphenol molecules prepared by the anti-mildew and antibacterial bio-based silicone material provided by the present invention has innovatively solved the problem of polyphenol molecule dispersion and anchoring: through the interface confined click chemistry strategy, it has for the first time realized that the easily self-polymerized polyphenol molecules are uniformly anchored on the surface of the filler in a monolayer, high density, covalent bonded form, completely eliminating bulk self-polymerization and realizing kinetically stable ideal dispersion.

[0022] (2) The anti-mildew and antibacterial bio-based silicone material provided by the present invention realizes the integration of composite material structure and function: while significantly improving mechanical properties, it simultaneously endows the material with non-migratory long-term antibacterial and antioxidant functions.

[0023] (3) The method for preparing anti-mildew and antibacterial bio-based silicone material provided by the present invention has the advantages of high efficiency, controllability and ease of industrialization.

[0024] (4) The method for preparing anti-mildew and antibacterial bio-based silicone material provided by the present invention has a simple process, mild conditions, and a wide range of raw materials, which is in line with the trend of green chemistry and sustainable development. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to embodiments. It should also be understood that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. The specific mass, reaction time, temperature, process parameters, etc., in the examples are merely examples within a suitable range. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0026] The main raw material used in the examples section is: fumed silica nanoparticles: primary particle size approximately 12 nm, BET specific surface area 200 ± 25 m². 2 / g, activated and dried in a vacuum oven at 120℃ for 2 hours before use to remove physically adsorbed water on the surface; Nano-CaCO3: cubic nano-calcium carbonate, average particle size 50 nm, BET specific surface area approximately 40 m² 2 / g; dried at 100℃ before use; γ-glycidoxypropyltrimethoxysilane (GPTMS): purity ≥98%, sealed and stored away from moisture; hydrolyzed tannic acid: analytical grade, derived from gallnut, molecular weight approximately 1700 Da, each molecule theoretically contains 25 phenolic hydroxyl groups; gallic acid monohydrate: analytical grade, white or light gray fine crystals, each molecule contains one carboxyl group and three phenolic hydroxyl groups; triethylamine, analytical grade. To eliminate moisture interference, dried by heating with calcium hydride under reflux before use, and then distilled under nitrogen protection at atmospheric pressure; anhydrous toluene: heated to blue in a sodium wire / benzophenone system, then distilled and used immediately under nitrogen protection; N,N-dimethylformamide (DMF): analytical grade, soaked and dried in activated 4A molecular sieve for more than 48 hours; deionized water: high-purity water with a resistivity of 18.25 MΩ·cm, bubbled with high-purity nitrogen for 30 minutes to remove dissolved oxygen. Bio-based silicone rubber: ELASTOSIL® eco R 401 / 40 S.

[0027] The main instruments used in the examples section are: a three-necked round-bottom flask, a reflux condenser, a constant pressure dropping funnel, a Schlenk double-row vacuum / nitrogen system, a high-speed centrifuge (maximum speed 15000 rpm), a vacuum oven, a constant temperature and humidity incubator, and a biological microscope.

[0028] Example 1: The preparation steps for anti-mildew and antibacterial bio-based silicone materials are as follows: (1) Accurately add 5.0 g of pre-dried fumed silica and 250 mL of anhydrous toluene to a 500 mL three-necked round-bottom flask; immerse the flask in an ice-water bath and purge with high-purity nitrogen for at least 15 minutes to replace the air in the system; then ultrasonically disperse the mixture for 30 minutes to prepare a stable suspension that is uniformly translucent, slightly milky white, and free of obvious particles. Maintain continuous nitrogen protection and mechanical stirring (300 rpm), add 0.75 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) to the obtained suspension at once using a syringe; slowly turn on the heating and raise the temperature to 90 °C, and stir at this temperature for 10 hours; after the reaction is completed, transfer the mixture to a centrifuge tube, centrifuge at 8000 rpm for 10 minutes, and discard the supernatant. Add approximately 50 mL of anhydrous toluene to the solid obtained by centrifugation, vortex or sonicate to redisperse it, and centrifuge again; repeat this "redispersion-centrifugation" washing process twice; then, replace the washing solvent with anhydrous ethanol, and wash and centrifuge twice more to thoroughly remove any unreacted GPTMS monomers and their self-condensation byproducts; place the washed solid product on a petri dish and dry it in a vacuum oven at 60°C for 12 hours until constant weight; remove the dried solid and gently grind it in an agate mortar until a fluffy white powder is obtained, thus preparing epoxy-functionalized nano-silica (SiO2-GPTMS). (2) Accurately weigh 3.0 g of the SiO2-GPTMS powder prepared in step (1) and put it into a dry 500 mL three-necked flask; then add 150 mL of a mixed solvent consisting of N,N-dimethylformamide (DMF) and deionized water (the volume ratio of DMF to deionized water is 85:15); ultrasonically disperse the three-necked flask under an ice-water bath for 30 minutes to obtain a uniform suspension containing SiO2-GPTMS; (3) Under conditions of room temperature, nitrogen protection, and uniform stirring (200 rpm), a tannic acid solution (1.5 g of tannic acid dissolved in 50 mL of a mixed solvent consisting of DMF and deionized water in a volume ratio of 85:15) was added dropwise at a very slow flow rate of 0.5 mL / min to the suspension containing SiO2-GPTMS obtained in step (2). The entire process took about 100 minutes. After the addition was complete, 0.05 g of the catalyst triethylamine was added to the reaction mixture using a microsyringe. The reaction system was slowly heated to 70°C and stirred gently at this temperature for 6 hours. As the reaction proceeded, the color of the reaction mixture was clearly observed to gradually and uniformly change from the initial milky white to light brown and even brown, which is a macroscopic color indicator of the successful anchoring of tannic acid molecules. After the reaction was completed, the mixture was cooled to room temperature. The mixture was centrifuged at 10,000 rpm for 15 minutes, and the lower brown solid was collected. To completely remove all unreacted, physically adsorbed, or self-polymerized free tannins in the bulk phase, an extremely rigorous washing procedure is required: the solids are repeatedly redispersed and centrifuged using the aforementioned DMF / water (85:15) mixed solvent. Each wash uses at least 50 mL of fresh solvent, and the solids are thoroughly and uniformly redispersed with ultrasonic assistance before centrifugation. This process is repeated at least five times until the supernatant after the final centrifugation shows no detectable characteristic absorption peaks of tannins at 280 nm using a UV-Vis spectrophotometer. Finally, the product is washed once more with anhydrous ethanol to replace the high-boiling-point DMF. The washed product is dried to constant weight in a vacuum oven at 50°C, and after grinding, a light brown powder is obtained, which is high-density tannin-anchored nano-silica (SiO2-TA). (4) Under the conditions of room temperature and continuous magnetic stirring, 4.0 g of SiO2-TA powder obtained in step (3) was slowly added to 200 mL of zinc sulfate heptahydrate aqueous solution with a concentration of 2.5 mg / mL. As the powder dispersed, the color of the system was observed to rapidly change from light brown to dark brown, or even black. This is a typical color change of the reaction between zinc ions and polyphenols to form a coordination complex. The reaction needs to be continuously stirred at room temperature for 45 minutes. After the reaction was completed, the product was precipitated by centrifugation at 10,000 rpm for 15 minutes, and the supernatant was discarded. The precipitate was redispersed with a large amount of deionized water and washed twice by centrifugation to remove excess free zinc ions and sulfate ions. Then it was washed once with anhydrous ethanol, and the product was dried overnight in a vacuum oven at 60℃ to obtain dark brown SiO2@TA-Zn powder. (5) On a clean two-roll mill (roll diameter 150 mm, speed ratio 1:1.4), coat 100 parts by weight of bio-based silicone rubber (ELASTOSIL® eco R 401 / 40 S) onto the front roll. The roll temperature is controlled at 25-35°C using circulating cooling water. After the raw rubber has evenly coated the roll and formed a smooth accumulation, begin mixing; Add the formulation additives sequentially, in small batches, in the following order and in the following quantities (by weight, phr): 5 phr hydroxyl silicone oil (structure control agent, hydroxyl value 4.5%) 35 phr precipitated silica (BET specific surface area 160 m² / g). 5 phr SiO2@TA-Zn powder prepared in step (4).

[0029] Once each batch of filler has been largely incorporated into the rubber compound, the next batch is added. After all fillers have been added, the mixture is thoroughly combined by continuously cutting left and right with the blades and creating triangular clumps. The entire mixing process takes approximately 40 minutes.

[0030] After the filler is evenly dispersed, add 1.5 phr of peroxide vulcanizing agent (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, bis(2,5-dimethyl)peroxy)hexane. After adding the vulcanizing agent, quickly mix and pass through a thin sheet 8 times to obtain a light gray-black homogeneous compound. Let the compound stand at room temperature overnight (12 hours).

[0031] The next day, the compounded rubber was vulcanized on a flat vulcanizing machine. The mold was a 2 mm thick metal frame, the vulcanization temperature was 170℃, the pressure was 15 MPa, and the vulcanization time was T90+2 minutes (determined by the positive vulcanization time measured by a rotorless rheometer; for this formula, it was approximately 10 minutes). After vulcanization, the sheet was demolded and removed. To completely decompose residual peroxides, eliminate their impact on performance, and stabilize the crosslinking network, the sheet obtained from the first vulcanization was suspended in a forced-ventilation high-temperature oven and subjected to a second vulcanization at 200℃ for 4 hours. After natural cooling, the final anti-mildew and antibacterial bio-based silicone sheet was obtained.

[0032] The mechanical properties of the anti-mildew and antibacterial bio-based silicone sheet were tested according to ASTM D412 standard, using dumbbell-shaped specimens and a universal testing machine. The results are as follows: Tensile strength: 8.4 MPa; 100% constant tensile stress: 1.2 MPa; Elongation at break: 580%; Tear strength (trousers type, ASTM D624): 22 kN / m.

[0033] The non-migratory antibacterial test procedures and results for the antifungal and antimicrobial bio-based silicone sheet are as follows: This test was conducted in accordance with JIS Z 2801 standard, using Escherichia coli and Staphylococcus aureus as test strains.

[0034] The accelerated migration experiment was conducted by immersing two samples of the same size (5cm×5cm) of the tested antifungal and antibacterial bio-based silicone sheet and the control sample (silicone sheet with equal amounts of tannic acid and zinc salt directly physically blended, with other formulations being the same) in 100mL of food simulation solution (two portions each of 3% acetic acid and 10% ethanol aqueous solution) and aging them in an oven at 60℃ for 10 days.

[0035] The inoculation and culture conditions were as follows: 10 days later, the two types of samples were taken respectively; one part was directly rinsed with sterile water and inoculated according to JIS Z 2801 standard, and cultured at 37℃ and 90% RH for 24 hours to test its antibacterial rate against the two bacteria; the other part was analyzed by inductively coupled plasma mass spectrometry and other analytical methods to detect the concentration of zinc ions released.

[0036] Test results: Antibacterial rate: The antifungal and antibacterial bio-based silicone sample prepared in this embodiment, after undergoing a rigorous accelerated aging process at 60°C for 10 days, achieved an antibacterial rate of over 99.999% against two types of bacteria, demonstrating extremely excellent durability.

[0037] Migration and precipitation: High concentrations of zinc ions and polyphenols were detected in the migration liquid of the control sample's food simulation solution, directly demonstrating the migration and precipitation of small molecule active substances in the "physical blending" system. In contrast, the concentration of zinc ions in the migration liquid of the present invention's sample was below the detection limit of inductively coupled plasma mass spectrometry. This strongly proves that, through the covalent anchoring and in-situ chelation strategy of the present invention, the antibacterial active components are irreversibly "locked" onto the filler surface, achieving truly "non-migratory" long-lasting antibacterial action.

[0038] The test steps and results for the anti-mildew and antibacterial properties of bio-based silicone sheets are as follows: This test was conducted according to GB / T 1741-2020 "Determination of Antifungal Resistance of Coatings" to test the antifungal and antibacterial silicone sheet prepared in this embodiment. A mixed spore suspension was prepared using five standard strains: *Aspergillus niger* (ATCC 9642), *Chaetomium globosum* (ATCC 6205), *Trichoderma virens* (ATCC 9645), *Aureobasidium pullulans* (ATCC 15233), and *Aspergillus flavus*, with a spore concentration of 1.0 × 10⁻⁶. 6 CFU / mL. Place a 50 mm × 50 mm × 2 mm sample in a petri dish, spray the spore suspension evenly, and incubate for 28 days in a constant temperature and humidity incubator at 28 ± 1°C and relative humidity ≥ 90%. Observe the mold growth every 7 days and evaluate the mold prevention level according to the 0-4 standard.

[0039] Test results show that the antifungal and antibacterial bio-based silica gel sample prepared in this embodiment showed no mold growth on its surface during the 28-day incubation period, achieving a mold resistance level of 0 (the highest level). In contrast, the blank silica gel without added functional fillers (Comparative Example 1) showed obvious mold growth on day 14, and its mold resistance level was only level 4 after 28 days, proving that the present invention achieves excellent non-migratory mold resistance.

[0040] Example 2: The preparation steps for the anti-mildew and antibacterial bio-based silicone material are the same as in Example 1, with the following differences: In step (1), nano-silica is replaced by an equal mass of nano-calcium carbonate (Nano-CaCO3, cubic nano-calcium carbonate, average particle size 50 nm, BET specific surface area approximately 40 m²). 2 / g; dry at 100℃ before use. ); To avoid excessive acidity affecting the hydrolysis of the coupling agent, the amount of silane coupling agent GPTMS was adjusted to 1.0 g, and all other process parameters (temperature, time, solvent) remained consistent with Example 1, thus preparing epoxy-functionalized nano-calcium carbonate (CaCO3-GPTMS).

[0041] In step (2), the ratio of the mixed solvent is adjusted to DMF / water = 95:5; In step (3), tannic acid was replaced by gallic acid (GA) at a mass ratio. Because gallic acid is a small molecule, it has better solubility in the solvent and higher reactivity; to promote its complete dissolution and unification, the ratio of the mixed solvent was adjusted to DMF / water = 95:5. Similarly, the gallic acid solution was added dropwise to the CaCO3-GPTMS suspension at a rate of 0.5 mL / min, and 0.05 g of triethylamine was added as a catalyst. The reaction temperature was lowered to 60℃, and the reaction time was shortened to 4 hours to avoid oxidation of the grafted gallic acid due to excessively high temperature or long reaction time. Finally, after the same rigorous washing and drying process, a white, slightly beige CaCO3-GA powder was obtained.

[0042] Zinc ion chelated CaCO3@GA-Zn core-shell particles were prepared according to step (4); Step (5) Prepare silicone according to the following formulation: 100 phr bio-based silicone rubber (ELASTOSIL® eco R401 / 40 S), 10 phr hydroxyl silicone oil, 30 phr surface-modified fumed silica (suitable for high transparency systems), 15 phr CaCO3@GA-Zn particles, and 0.8 phr bis(2,5)-pentachlor vulcanizing agent. Using the same mixing and vulcanization process as in Example 1, a light-colored, translucent silicone sheet is obtained.

[0043] The mechanical properties of the obtained silicone sheet were characterized according to Example 1, and the results are as follows: Tensile strength: 9.1 MPa; 100% constant tensile stress: 1.6 MPa; Elongation at break: 710%; Tear strength (trouser type, ASTM D624): 29 kN / m.

[0044] The obtained silicone sheet was subjected to an antibacterial test according to Example 1, and the results are as follows: The obtained silicone sheet had an antibacterial rate of 83% against Escherichia coli and an antibacterial rate of 80% against Staphylococcus aureus.

[0045] In addition, we characterized the optical properties and UV aging resistance of the obtained silicone sheet. The characterization conditions and results are as follows: Optical performance: Tested with a UV-Vis-NIR spectrophotometer, the 2 mm thick sheet achieved a transmittance of 82.3% at a visible wavelength of 550 nm, only slightly lower than the transmittance of blank transparent silicone without this functional filler (88.5%), while the haze was only 5.1%. This invention successfully achieves compatibility between functionality and optical transparency through an extremely thin shell and refractive index matching (the composite refractive index of the gallic acid-zinc shell and nano-calcium carbonate is very close to that of the silicone matrix).

[0046] UV aging resistance (non-migratory antioxidant): Since the anchored gallic acid shell itself is an excellent free radical scavenger, this material exhibits good UV aging resistance in a UV aging chamber (UVA-340 lamp, 0.89 W / m²). 2 After being tested at 60℃ for 168 hours, its tensile strength and elongation at break retained as high as 91% and 88%, respectively.

[0047] Example 3: The preparation steps for the anti-mildew and antibacterial bio-based silicone material are the same as in Example 1, with the following differences: In step (4), the zinc sulfate heptahydrate aqueous solution is replaced by an equal mass of copper sulfate pentahydrate aqueous solution to prepare copper ion chelated SiO2@TA-Cu powder; In step (5), SiO2@TA-Zn powder is replaced with SiO2@TA-Cu powder; the same mixing and vulcanization process as in Example 1 is used to obtain light-colored, translucent silicone sheets.

[0048] The mechanical properties of the obtained silicone sheet were characterized according to Example 1, and the results are as follows: Tensile strength: 8.7 MPa; 100% constant tensile stress: 1.3 MPa; Elongation at break: 600%; Tear strength (trouser type, ASTM D624): 24 kN / m.

[0049] The obtained silicone sheet was subjected to an antibacterial test according to Example 1, and the results are as follows: The resulting silicone sheet exhibits an antibacterial rate of over 99.999% against Escherichia coli and Staphylococcus aureus.

[0050] The amount of copper ions migrating and precipitating in the obtained silicone sheet was below the detection limit; this proves that the copper ions are firmly chelated in the polyphenol shell, achieving non-migratory long-lasting antibacterial effect.

[0051] The resulting silicone sheet has a mildew resistance rating of 0.

[0052] Furthermore, we used a small blade to create a slight scratch approximately 5 μm wide on the surface of the prepared silicone sheet. The scratched sheet was then exposed to a 60°C, 90% RH environment for 24 hours. Microscopic observation revealed significant healing of the scratch, with the width narrowing and the edges becoming blurred. We hypothesize that at the microcracks on the silicone sheet surface, the functionalized nanofiller (SiO2@TA-Cu), originally physically encapsulated by silicone rubber polymer chains, was exposed. Then, under the synergistic effect of 60°C and high humidity (90% RH), water molecules, acting as plasticizers, lowered the glass transition temperature of the silicone rubber molecular chains, enhancing the mobility of the chain segments. Simultaneously, the coordination bonds between the metal and ligands in the TA-Cu coordination network underwent dynamic dissociation and recombination. Therefore, with the assistance of water molecules, the coordination bonds on the exposed filler particle surface broke and re-coordinated, driving chain rearrangement and interdiffusion of the surrounding silicone rubber polymer chains, thereby achieving the filling and repair of the microcracks. This phenomenon endows the antifungal and antibacterial bio-based silicone material of this application with a unique self-healing function.

[0053] Comparative Example 1: The preparation steps of the anti-mildew and antibacterial bio-based silicone material are the same as those in step (5) of Example 1, except that the SiO2@TA-Zn functionalized core-shell particles are replaced with unmodified fumed silica from the same batch.

[0054] The mechanical properties of the obtained silicone sheet were characterized according to Example 1, and the results are as follows: Tensile strength: 6.1 MPa; 100% constant tensile stress: 1.0 MPa; Elongation at break: 430%; Tear strength (trouser type, ASTM D624): 16 kN / m.

[0055] The obtained silicone sheet was subjected to an antibacterial test according to Example 1, and the results are as follows: The resulting silicone sheet had an antibacterial rate of 77% against Escherichia coli and an antibacterial rate of 73% against Staphylococcus aureus.

[0056] The obtained silicone sheet was subjected to an anti-mildew test according to Example 1, and the results are as follows: The obtained silicone sheet showed obvious mold growth on the 14th day, and after 28 days the mold coverage area exceeded 80%, with a mold resistance level of 4.

[0057] A slight scratch about 5 μm wide was made on the surface of the prepared silicone sheet using a small blade; the scratched sheet was then exposed to an environment of 60°C and 90% RH for 24 hours; microscopic observation revealed that the scratch did not change significantly.

[0058] Comparative Example 2: The preparation steps of the anti-mildew and antibacterial bio-based silicone material are the same as in Example 2, except that the SiO2@TA-Zn functionalized core-shell particles are replaced with unmodified nano-calcium carbonate.

[0059] The mechanical properties of the obtained silicone sheet were characterized according to Example 1, and the results are as follows: Tensile strength: 5.2 MPa; 100% constant tensile stress: 0.9 MPa; Elongation at break: 480%; Tear strength: 15 kN / m.

[0060] The obtained silicone sheet was subjected to an antibacterial test according to Example 1, and the results are as follows: The obtained silicone sheets showed antibacterial rates of less than 20% against both Escherichia coli and Staphylococcus aureus, indicating no significant antibacterial activity.

[0061] The obtained silicone sheet was subjected to an anti-mildew test according to Example 1, and the results are as follows: The obtained silicone sheet showed mold growth on the 21st day, and after 28 days the coverage area was about 25-40%, with a mold resistance level of 2-3.

[0062] The optical properties of the obtained silicone sheet were characterized according to Example 2, and the results are as follows: The light transmittance of the resulting silicone sheet dropped sharply to 62.0%, while the haze reached as high as 33.0%.

Claims

1. A bio-based silicone material with anti-mildew and antibacterial properties, characterized in that, The bio-based silicone material is composed of a polymer matrix and nanofillers with surface chemically anchored polyphenol molecules; wherein the nanofillers include an inorganic nanofiller core and a polyphenol molecule shell anchored to the surface of the inorganic nanofiller core.

2. The anti-mildew and antibacterial bio-based silicone material according to claim 1, characterized in that, The amount of the surface chemically anchored polyphenol molecules nanofiller added to the polymer matrix is ​​1% to 30% of the mass of the polymer matrix.

3. The anti-mildew and antibacterial bio-based silicone material according to claim 1, characterized in that, The natural polyphenolic compound is selected from either tannic acid or gallic acid.

4. The anti-mildew and antibacterial bio-based silicone material according to claim 1, characterized in that, The inorganic nanofiller core is selected from either nano-silica or nano-calcium carbonate.

5. The antifungal and antibacterial bio-based silicone material according to claim 1, characterized in that, The polymer matrix is ​​bio-based silicone rubber.

6. A method for preparing a mildew- and antibacterial bio-based silicone material as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) An inorganic nanofiller with a surface rich in epoxy groups is prepared by silanizing an unmodified inorganic nanofiller with an epoxy-containing silane coupling agent in an organic solvent. (2) The inorganic nanofiller with surface rich in epoxy groups obtained in step (1) is dispersed in a mixed solvent composed of a non-protic polar solvent and a protic solvent to obtain a suspension of inorganic nanofiller with surface rich in epoxy groups. (3) Add a natural polyphenol compound solution to the suspension of inorganic nanofiller with surface rich in epoxy groups obtained in step (2), and then add a catalyst to carry out a heating reaction to obtain an inorganic nanofiller with a polyphenol molecular shell. (4) Disperse the inorganic nanofiller containing polyphenol molecular shell obtained in step (3) in a solution containing antibacterial metal ions, and then continue to stir the mixture at room temperature to obtain an inorganic nanofiller containing a metal-polyphenol coordination network outer layer. (5) On the open mill, the bio-based silicone rubber is wrapped around the front roller. After the raw rubber is evenly wrapped around the roller and forms a smooth accumulation, the mixing begins. The formulation additives are added in sequence, in small amounts, and in batches: hydroxyl silicone oil, precipitated silica, and inorganic nanofiller containing polyphenol molecular shell prepared in step (4). After all the additives are added, the components are fully mixed by continuously cutting left and right and making triangular wraps. After the filler is evenly dispersed, the vulcanizing agent is added last. The mixture is quickly mixed, passed through a thin sheet, and then the compound is obtained. The compound is placed on a flat vulcanizing machine for a first-stage vulcanization after being left to stand at room temperature. The sheet obtained from the first-stage vulcanization is subjected to a second-stage vulcanization. After natural cooling, the anti-mildew and antibacterial bio-based silicone material can be prepared.

7. The method for preparing antifungal and antibacterial bio-based silicone material according to claim 6, characterized in that, The aprotic polar solvent is N,N-dimethylformamide; the protic solvent is water.

8. The method for preparing antifungal and antibacterial bio-based silicone material according to claim 6, characterized in that, The heating reaction in step (3) is carried out at a temperature of 50-100°C for 2-12 hours.

9. The method for preparing antifungal and antibacterial bio-based silicone material according to claim 6, characterized in that, The catalyst mentioned in step (3) is triethylamine.

10. The method for preparing antifungal and antibacterial bio-based silicone material according to claim 6, characterized in that, In step (5), the vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.