Efficient bio-based fireproof heat-insulation antibacterial coating as well as preparation method and application thereof

Abstract

The invention relates to an efficient bio-based fireproof heat-insulation antibacterial coating and a preparation method and application thereof.According to the system, renewable phytic acid serves as a core functional component, the phytic acid is modified through polyethylene glycol so as to optimize the compatibility and film forming stability of the phytic acid, and the coating is endowed with lasting antibacterial performance. Piperazine and 1-hydroxyethylidene-1, 1-diphosphonic acid react to prepare piperazine 1-hydroxyethylidene-1, 1-diphosphonic acid serving as a flame-retardant component, and the piperazine 1-hydroxyethylidene-1, 1-diphosphonic acid serves as an acid source / gas source synergistic unit of the intumescent flame-retardant system to promote rapid char formation and construction of an The preparation method comprises the following steps: reacting PEG modified phytic acid with piperazine hydroxyethylidene diphosphonate, introducing aerogel and gelatin, and carrying out blending dispersion and film formation to obtain the composite coating. Wherein the aerogel constructs a high-efficiency heat insulation framework by virtue of low heat conductivity, and the gelatin provides a film forming and interface bonding effect, so that the compactness and adhesive force of the coating are further improved. The coating can simultaneously realize multifunctional synergy of flame retardance, heat insulation, bacteriostasis and mildew prevention on the surface of a base material such as wood and the like.

Description

Technical Field

[0001] This invention relates to the fields of wooden furniture, water-based decoration, packaging coating, building interior decoration, and surface protection of textile and paper-based materials, specifically to a highly efficient bio-based fireproof, heat-insulating, and antibacterial coating, its preparation method, and its application. Background Technology

[0002] Bio-based coatings, due to their renewable sources, low environmental impact, and good human-friendly properties, have been applied in fields such as wooden furniture, water-based decoration, packaging coating, building interiors, and surface protection of textiles and paper-based materials. Typical bio-based film-forming or modifying components include polysaccharides, proteins, phytic acid, tannins, lignin, and vegetable oil derivatives, which can, to some extent, replace petrochemical resins, reduce volatile organic compound (VOC) emissions, and improve material sustainability. However, existing bio-based coatings still face multiple bottlenecks: First, natural polymers generally suffer from insufficient water resistance and durability, low thermal stability, and limitations in substrate adhesion and mechanical properties; second, single bio-based systems have limited functionality and cannot simultaneously meet the composite requirements of flame retardancy, heat insulation, and antibacterial / mildew prevention; third, some halogen-free flame retardant systems require high addition amounts, which can easily cause coating embrittlement, cracking, or affect appearance and workability; fourth, porous substrates such as wood are prone to mold growth in humid environments, leading to corrosion and mechanical degradation, while existing antibacterial solutions containing silver or quaternary ammonium salts are controversial in terms of cost, durability, or environmental risks. Therefore, developing bio-based coating systems that combine green sources, workability, and multifunctional synergy is of great significance.

[0003] Constructing bio-based antibacterial, fireproof, and heat-insulating coatings with gelatin has practical value: gelatin is widely available, can be dispersed in water to form films, and has good wetting and bonding effects on wood fibers, making it suitable as a film-forming and interface-reinforcing phase for coatings; through synergy with phytic acid derivatives and intumescent flame-retardant components, it can promote the formation of char and an intumescent isolation layer when heated, thereby blocking heat transfer. At the same time, the natural phosphorus-containing structures of phytic acid and other components provide antibacterial and antifungal potential, thus extending the service life of wood materials and improving fire safety.

[0004] Introducing aerogel into this type of fireproof, heat-insulating, and antibacterial coating is of key significance: aerogel has ultra-low thermal conductivity and high porosity, which can build a lightweight heat-insulating network in the coating, significantly reduce heat flux and delay the heating of the substrate; its porous skeleton can also work synergistically with the carbon layer to improve the stability and density of the heat insulation layer, inhibit crack propagation and the escape of pyrolysis products, thereby improving heat insulation efficiency and comprehensive protection performance without significantly increasing the coating density and thickness. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient bio-based fire-retardant, heat-insulating, and antibacterial coating, its preparation method, and its application. This invention modifies phytic acid with polyethylene glycol (PEG) to optimize its compatibility. Piperazine hydroxyethylidene diphosphonate (HEDP) is prepared by reacting piperazine and HEDP in anhydrous ethanol, serving as the acid / gas source synergistic unit in an intumescent flame-retardant system. Gelatin is used as the bio-based film-forming agent, and an appropriate amount of aerogel is introduced to improve the stability and density of the heat insulation layer. A composite coating is obtained through blending, dispersion, and film formation.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A highly efficient bio-based fire-retardant, heat-insulating, and antibacterial coating is a polyethylene glycol-modified phytic acid / piperazine hydroxyethylidene diphosphonate-aerogel-gelatin fire-retardant, heat-insulating, and antibacterial coating. The preparation method is as follows: phytic acid is modified with polyethylene glycol, and the prepared piperazine hydroxyethylidene diphosphonate is dissolved in the modified phytic acid solution. The solution is then dried in an oven to prepare a polyethylene glycol-modified phytic acid / piperazine hydroxyethylidene diphosphonate composite flame retardant and antibacterial agent. Subsequently, the product, aerogel, and gelatin are mixed to prepare the polyethylene glycol-modified phytic acid / piperazine hydroxyethylidene diphosphonate-aerogel-gelatin fire-retardant, heat-insulating, and antibacterial coating.

[0007] Specifically, the following steps are included: (1) Preparation of piperazine hydroxyethylidene diphosphonate: Piperazine and hydroxyethylidene diphosphonic acid (HEDP) were prepared at a molar ratio of piperazine to HEDP of 1 to 2:1. Piperazine was dissolved in anhydrous ethanol, and HEDP ethanol solution was added dropwise under stirring. The reaction was carried out at a certain temperature to obtain a white solid product. The product was washed by centrifugation with anhydrous ethanol and dried to constant weight to obtain piperazine hydroxyethylidene diphosphonate, denoted as HEFER. (2) Preparation of polyethylene glycol modified phytic acid: Phytic acid (PA) and polyethylene glycol (PEG) were mixed at a PA:PEG molar ratio of 1:1 to 6. The phytic acid solution was first heated in an oil bath at a certain temperature and filled with an inert atmosphere to remove moisture. Then, polyethylene glycol was added and heated under an inert atmosphere to react, yielding polyethylene glycol-modified phytic acid, denoted as PAPEG. (3) Preparation of composite flame-retardant and antibacterial components: HEFER and PAPEG are mixed at a molar ratio of HEFER:PAPEG of 1 to 3:1, deionized water is added, and the mixture is stirred at 60 to 80°C to form a homogeneous solution. The solution is then dried to obtain a composite flame retardant and antibacterial component, denoted as PAGHR. (4) Preparation and application of the coating system: PAGHR, aerogel and gelatin are mixed at a mass ratio of 0.1-1:0.01-0.1:1, deionized water is added, and the mixture is stirred at 60-80°C until it is uniformly dispersed to obtain a coating solution. The coating solution is applied to the surface of the substrate and dried and cured to obtain a bio-based fireproof, heat-insulating and antibacterial coating.

[0008] Furthermore, the aerogel is a silica aerogel with a particle size of 7~30nm.

[0009] Furthermore, in step (1), the reaction stirring time is 4 to 6 hours.

[0010] Furthermore, in step (2), the molecular formula of polyethylene glycol (PEG) is HO(CH2CH2O). n H and Mn are 200~2000, and further selected from any one of molecular weights of 200, 600, 1000, and 2000; the reaction temperature is 135~150℃, and the reaction time is 5~6h.

[0011] Furthermore, in step (3), the stirring time is 0.5 to 2 hours.

[0012] Furthermore, in step (3), the drying step is carried out in an oven at a temperature of 80-100°C for 12-18 hours.

[0013] Furthermore, in step (4), the stirring time is 1 to 3 hours.

[0014] Furthermore, in step (4), the coating method includes one or more of brush coating, roller coating, and spray coating; when the substrate is a wood substrate, the coating coverage per unit area after drying is 100-300 g / m². 2 .

[0015] The high-efficiency bio-based fireproof, heat-insulating, and antibacterial coating prepared by this invention can be used in the fields of flame retardancy, fire prevention, heat insulation, and antibacterial properties. It can be applied to the surface of wood, bamboo, artificial boards, or their composite materials to impart flame-retardant, fire-proof, heat-insulating, and antibacterial / mildew-proof properties to the substrate.

[0016] This coating utilizes a bio-based film-forming system constructed from phytic acid and gelatin. PEG modification enhances compatibility and film-forming stability, while also imparting antibacterial and antifungal potential. Piperazine hydroxyethylidene diphosphonate introduces a phosphorus-nitrogen synergistic expansion flame-retardant mechanism, promoting charring upon heating and forming a dense insulating layer to reduce heat release and flammable gas escape. Aerogel provides a low thermal conductivity insulating framework and synergistically enhances thermal shielding and structural integrity with the char layer. Overall, it boasts advantages such as being green and low in VOCs, having good adhesion, and integrating multiple functions including flame retardancy, heat insulation, and antibacterial properties.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) Significant flame retardant and fireproof effect with more controllable smoke and toxicity: Polyethylene glycol modified phytic acid and piperazine hydroxyethylidene diphosphonate construct a phosphorus-nitrogen intumescent flame retardant system. When heated, it quickly forms char and expands to form a dense isolation layer, which inhibits heat release and the escape of combustible volatiles, and improves the fire resistance safety of wood substrate.

[0018] (2) High thermal insulation efficiency and longer thermal protection: Aerogel forms a stable thermal insulation network in the coating with its ultra-low thermal conductivity and porous skeleton, reducing heat flux and delaying the rise of back temperature; it works in synergy with the carbon layer to improve the integrity of the thermal insulation layer and reduce cracking and failure.

[0019] (3) Antibacterial and mildew-proof properties combined with applicability: PEG-modified phytic acid enhances the compatibility and film-forming stability of the system, and combined with the adhesive film-forming effect of gelatin, the coating adheres well to the wood; the coating has antibacterial and mildew-proof capabilities, which can reduce mold erosion and extend service life. Attached Figure Description

[0020] Figure 1 The reaction equation is for a composite flame retardant and antibacterial flame retardant.

[0021] Figure 2 This is the thermogravimetric analysis (TGA) curve.

[0022] Figure 3 This is a SEM image.

[0023] Figure 4 The total heat release (THR) curve and the heat release rate (HRR) curve are shown.

[0024] Figure 5 To compare the antibacterial activity of the comparative examples against Escherichia coli (a) and Staphylococcus aureus (b). Detailed Implementation

[0025] 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.

[0026] Example 1 Combination Figure 1 As shown, a method for preparing a high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating is as follows: (1) Weigh 0.1 mol piperazine, add 200 g of anhydrous ethanol and stir to dissolve, then add 0.1 mol HEDP (the molar ratio of piperazine to HEDP is 1:1), and stir at 50 °C for 6 h to obtain a white solid product; filter the product with anhydrous ethanol, wash and dry to constant weight to obtain piperazine hydroxyethylidene diphosphonate, denoted as HEFER.

[0027] (2) Weigh 0.01 mol of phytic acid (PA) solution and add it to a three-necked flask. In an oil bath at 135°C, after purging with nitrogen to remove moisture, add 0.03 mol of polyethylene glycol (PEG, Mn 200) (PA to PEG molar ratio 1:3). Continue heating the reaction under nitrogen atmosphere for 6 hours to obtain polyethylene glycol modified phytic acid, denoted as PAPEG.

[0028] (3) such as Figure 1 As shown, 0.03 mol HEFER was weighed and added to PAPEG solution (HEFER to PAPEG molar ratio 3:1), 300 mL of deionized water was added and mixed evenly. The mixture was stirred at 80 °C for 1 hour to form a homogeneous solution. The solution was dried to obtain the composite flame retardant and antibacterial component, denoted as PAGHR.

[0029] (4) Weigh 6 g of gelatin, 3.5 g of PAGHR and 0.5 g of aerogel, mix them and add 50 mL of deionized water. Stir at 60 °C until uniformly dispersed to obtain a coating solution. Brush the coating solution onto the surface of the wood board and dry and cure to obtain a bio-based fireproof, heat-insulating and antibacterial coating, according to the standard of 200 g per square meter after drying. Among them, the aerogel is silica aerogel with a particle size of 7~30 nm.

[0030] Example 2 Combination Figure 1 As shown, a method for preparing a high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating is as follows: (1) Weigh 0.1 mol piperazine, add 200 g of anhydrous ethanol and stir to dissolve, then add 0.1 mol HEDP (the molar ratio of piperazine to HEDP is 1:1), and stir at 50 °C for 6 h to obtain a white solid product; filter the product with anhydrous ethanol, wash and dry to constant weight to obtain piperazine hydroxyethylidene diphosphonate, denoted as HEFER.

[0031] (2) Weigh 0.01 mol of phytic acid (PA) solution and add it to a three-necked flask. In an oil bath at 135°C, after purging with nitrogen to remove moisture, add 0.03 mol of polyethylene glycol (PEG, Mn 200) (PA to PEG molar ratio 1:3). Continue heating the reaction under nitrogen atmosphere for 6 hours to obtain polyethylene glycol modified phytic acid, denoted as PAPEG.

[0032] (3) such as Figure 1 As shown, 0.03 mol HEFER was weighed and added to PAPEG solution (HEFER to PAPEG molar ratio 3:1), 300 mL of deionized water was added and mixed evenly. The mixture was stirred at 80 °C for 1 hour to form a homogeneous solution. The solution was dried to obtain the composite flame retardant and antibacterial component, denoted as PAGHR.

[0033] (4) Weigh 6 g of gelatin, 3 g of PAGHR and 1 g of aerogel, mix them and add 50 mL of deionized water. Stir at 60 °C until uniformly dispersed to obtain a coating solution. Brush the coating solution onto the surface of the wood board and dry and cure to obtain a bio-based fireproof, heat-insulating and antibacterial coating, according to the standard of 200 g per square meter after drying. Among them, the aerogel is silica aerogel with a particle size of 7~30 nm.

[0034] Example 3 Combination Figure 1 As shown, a method for preparing a high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating is as follows: (1) Weigh 0.1 mol piperazine, add 200 g of anhydrous ethanol and stir to dissolve, then add 0.1 mol HEDP (the molar ratio of piperazine to HEDP is 1:1), and stir at 50 °C for 6 h to obtain a white solid product; filter the product with anhydrous ethanol, wash and dry to constant weight to obtain piperazine hydroxyethylidene diphosphonate, denoted as HEFER.

[0035] (2) Weigh 0.01 mol of phytic acid (PA) solution and add it to a three-necked flask. In an oil bath at 135°C, after purging with nitrogen to remove moisture, add 0.03 mol of polyethylene glycol (PEG, Mn 200) (PA to PEG molar ratio 1:3). Continue heating the reaction under nitrogen atmosphere for 6 hours to obtain polyethylene glycol modified phytic acid, denoted as PAPEG.

[0036] (3) such as Figure 1 As shown, 0.03 mol HEFER was weighed and added to PAPEG solution (HEFER to PAPEG molar ratio 3:1), 300 mL of deionized water was added and mixed evenly. The mixture was stirred at 80 °C for 1 hour to form a homogeneous solution. The solution was dried to obtain the composite flame retardant and antibacterial component, denoted as PAGHR.

[0037] (4) Weigh 6 g of gelatin, 2 g of PAGHR and 2 g of aerogel, mix them and add 50 mL of deionized water. Stir at 60 °C until uniformly dispersed to obtain a coating solution. Brush the coating solution onto the surface of the wood board and dry and cure to obtain a bio-based fireproof, heat-insulating and antibacterial coating, according to the standard of 200 g per square meter after drying. Among them, the aerogel is silica aerogel with a particle size of 7~30 nm.

[0038] To highlight the beneficial effects of the present invention, the following comparative examples are provided.

[0039] Comparative Example 1 Weigh 10g of gelatin and add 50mL of deionized water. Stir at 80℃ and apply to the wood board after thorough stirring, according to the standard of 200g per square meter after drying.

[0040] The performance of the materials in Examples 1-3 and Comparative Example 1 was tested, and the results are as follows.

[0041] (1) Thermogravimetric analysis (TGA): The thermal stability of the material was tested using a TGA-4000 thermal analyzer in a nitrogen atmosphere (heating rate 20℃ / min).

[0042] like Figure 2 As shown, under a nitrogen atmosphere, from room temperature to 250°C, the mass loss of the four groups of samples was very small, and the curves almost overlapped. The content of volatile small molecules / adsorbed water in the system was similar, and the introduction of aerogel and flame retardant had no significant effect on the low-temperature volatilization process. Comparative Example 1, with its pure gelatin coating, exhibited severe thermal decomposition at 300-400°C and continued to lose weight in the high-temperature region, with a residual mass of approximately 20% at 800°C, indicating limited carbonization efficiency and carbon structure stability. After introducing flame retardant and aerogel, the weight loss rate of the samples decreased in the main weight loss stage, and the mass retention capacity in the 400-800°C range was significantly enhanced, with the residual mass at 800°C increasing to approximately 43-48%. Examples 1-3 showed a significant slowdown in weight loss after 400°C and maintained higher residual mass at 800°C: Example 1: approximately 43% residual mass at 800°C; Example 2: approximately 48% residual mass at 800°C (highest); Example 3: approximately 46% residual mass at 800°C. Compared to Comparative Example 1, the residual mass of the composite system at 800°C increased by approximately 20-30 percentage points, indicating a significant synergistic effect between the flame retardant and aerogel: promoting dehydration and carbonization while stabilizing the residual structure with an inorganic framework. Among these, the 10% aerogel composite system exhibited the highest char rate and a more stable high-temperature plateau, demonstrating that an appropriate amount of aerogel and flame retardant can produce the best synergistic carbonization effect.

[0043] (2) Scanning electron microscope (SEM): ZEISS GeminiSEM500 was used for observation.

[0044] Figure 3The paper presents SEM morphologies (scale bar 10 μm) of the residual char layers after burning of four groups of coated wood panels. Comparative Example 1 shows a distinctly granular, loose, and porous char layer with a surface composed of numerous irregular fragments / particles, exhibiting a wide pore size distribution and strong connectivity. Example 1 shows a more pronounced plate-like / blocky continuous phase in its char layer. Compared to the pulverized particle structure of Comparative Example 1, its surface is more integrated, with locally visible large-sized plates. Example 2 exhibits a typical wrinkled / flaky char layer morphology, with fine texture and relatively uniform coverage, showing better overall continuity than Example 1. The good surface uniformity indicates a relatively ideal compatibility / dispersion state between the filler and the matrix, resulting in a more balanced carbonization reaction. Example 3 shows a char layer morphology exhibiting large-scale plate stacking and localized pores / fragmentation / peeling: on the one hand, a thicker plate-like char layer is visible, suggesting enhanced char yield and skeletal structure; on the other hand, obvious structural defects (such as localized through-holes, cracks, or plate detachment) are present in the char layer.

[0045] (3) Cone calorimeter test: The cone calorimeter test (Suzhou Yangyi Wolchi Testing Technology Co., Ltd.) was conducted according to the ISO 5600 standard test method. The sample size was 100×100×3 mm. 3 The radiative heat flux used in the experiment was 35 kW / m². 2 .

[0046] like Figure 4 As shown in (a), at 35 kW·m -2 Under thermal irradiation, the THR of Comparative Example 1 accumulated rapidly over time, reaching approximately 34 MJ·m⁻¹ in about 600 s. -2 In contrast, Examples 1-3 exhibited significantly reduced cumulative heat release levels: THR was approximately 16 MJ·m⁻¹ at 600 s. -2 (Example 1), 14.4 MJ·m -2 (Example 2) and 15 MJ·m -2 (Example 3) The reductions compared to Comparative Example 1 were approximately 53%, 57%, and 56%. From the curve morphology, the THR rise slope of the composite system decreased significantly in the early combustion stage (approximately 50-200 s), and maintained a consistently low accumulation rate in the subsequent stage (>200 s), indicating that the composite coating effectively weakened the positive feedback process of thermal decomposition combustion supply and flame thermal feedback. This result shows that the introduction of aerogel and flame retardant significantly reduced the effective combustion degree of the material at a given heat flux, promoted the formation of a char / insulation shield, and inhibited the continuous release of combustible volatiles. Example 2 (10% aerogel) achieved the lowest THR, indicating that the synergistic effect of barrier and char promotion was most sufficient at this formulation. Figure 4(b) shows that Comparative Example 1 exhibits high-intensity exothermic characteristics, rapidly reaching a high HRR after ignition and displaying obvious multi-peak behavior; its peak heat release rate (pHRR) is approximately 193 kW·m. -2 A high and sustained HRR indicates an ample supply of flammable volatiles generated by the thermal decomposition of the pure gelatin system, resulting in high combustion intensity in the flame zone and a significant risk of fire growth. After introducing aerogel and flame retardants, the HRR curve shifted downwards overall, especially the initial peak was significantly weakened: in Example 1, the pHRR decreased to approximately 90 kW·m⁻¹. -2 (Reduction of approximately 53%); Example 2: pHRR further decreased to approximately 76 kW·m -2 (The decrease was approximately 61%), and it entered a quasi-steady-state phase with a lower HRR more quickly after the peak; Example 3 pHRR was approximately 114 kW·m -2 (Reduction of approximately 41%), the suppression effect is weaker than that of Examples 1 and 2. From the perspective of flame retardant mechanism, the significant decrease in pHRR indicates that the composite system can establish an effective "heat-mass transfer barrier" in the early stage of combustion: on the one hand, the low thermal conductivity and porous framework of aerogel help reduce heat transfer to the substrate and alleviate the pyrolysis rate; on the other hand, the flame retardant promotes the dehydration and carbonization / crosslinking of gelatin, quickly forming a more stable char layer, reducing the transport of combustible volatiles to the flame zone and the diffusion of oxygen to the wood, thereby weakening the flame thermal feedback and suppressing the exothermic peak. It is worth noting that although Example 3 still has a significantly lower THR than Comparative Example 1, its early pHRR is higher than that of Example 2, suggesting that excessive aerogel content may introduce coating structural defects (such as uneven dispersion, insufficient interfacial bonding, or thermal cracking / peeling), resulting in insufficient continuity of the early shielding layer, thereby reducing the peak suppression efficiency; this trend is consistent with the structural fragmentation / pore characteristics observed in the char layer morphology after combustion.

[0047] Combining THR and HRR results, the aerogel / flame retardant / gelatin composite coating at 35 kW·m -2 Significantly improves material combustion behavior under certain conditions: Compared to pure gelatin coating, the composite system reduces THR (600 s) from approximately 34 MJ·m⁻¹. -2 Reduced to approximately 14.4–16 MJ·m -2 (Reduced by 53-57%), and reduced pHRR from approximately 193 kW·m -2 Reduced to approximately 76~114 kW·m -2(Reduction of 41-61%). Among them, 10% aerogel (Example 2) simultaneously achieved the lowest THR and the most significant pHRR suppression, indicating the existence of an optimal addition window; when the aerogel content increased to 20%, although the total heat release was still significantly reduced, the peak suppression effect weakened, indicating that excessive filler may weaken the early barrier effect due to the decrease in char layer continuity. Overall, this composite coating system, with condensed phase promoting char and heat / mass transfer barrier as the dominant mechanisms, effectively reduces the fire growth rate and fire heat load.

[0048] (4) Flame retardant performance: Taking the coated wood panels prepared in Examples 1-3 as examples, their flame retardant performance was determined. Limiting oxygen index (LOI) test: LOI was tested on an HC-2 oxygen index meter according to GB / T 2406.2-2009 standard. The sample size was 100×6.5×3 mm. 3 The sample was tested on a CZF-3 type horizontal and vertical combustion tester according to the GB / T 2408-2021 standard, with a sample size of 100×13×3 mm. 3 The specific measurement results are shown in Table 1.

[0049] Table 1 As shown in Table 1 above, the LOI of Comparative Example 1 was only 24.0%, close to the oxygen content in the air (~21%), indicating that the pure gelatin coating system has strong flammability and requires a low oxygen concentration to maintain combustion, making it difficult to form an effective flame-retardant barrier. After introducing aerogel and flame retardant, the LOI significantly increased to 35.0% (Example 1), 45.4% (Example 2), and 44.0% (Example 3), respectively, representing increases of +11.0, +21.4, and +20.0 percentage points compared to Comparative Example 1. This result shows that the composite coating significantly reduces the material's dependence on the oxygen environment and inhibits sustained combustion, demonstrating a clear flame-retardant synergistic effect. Comparative Group 1 failed the UL-94 test, indicating that the sample could not meet the rating requirements under vertical combustion conditions, reflecting its lack of an effective self-extinguishing mechanism and flame-retardant barrier under open flame conditions. In contrast, Examples 1-3 all achieved the V-0 rating, indicating that the composite coating has excellent flame-retardant response capabilities under the dynamic flame scouring conditions of vertical combustion. Combining the LOI and UL-94 results, the aerogel / flame retardant / gelatin composite coating exhibited significant flame retardant enhancement: the LOI increased from 24.0% to 35.0-45.4%, and the UL-94 rating improved from NR to V-0. The 10% aerogel (Example 2) achieved the highest LOI (45.4%), and combined with its V-0 rating, this indicates that the synergistic effect of condensed phase charring and thermal insulation is optimal at this content. When the aerogel content was further increased to 20%, the LOI slightly decreased, indicating that excessive addition would affect the flame retardant performance.

[0050] (5) Antibacterial properties.

[0051] The antibacterial properties of the composite coating were evaluated using Escherichia coli and Staphylococcus aureus. The coated samples from Comparative Example 1 and Examples 1-3 were directly cultured with bacterial suspensions at a mass ratio of 1:2. The samples were immersed in 1×10⁻⁶... 6 CFU·mL -1 The diluted bacterial suspension was first agitated in a shaking incubator for 30 minutes, and then incubated for 24 hours. 10 mL of buffer (pH = 7.4) was added to Comparative Example 1 and Examples 1-3, and bacterial suspensions were formed under vigorous shaking. The resulting suspension samples were then diluted 1000-fold. 100 µL of the diluted bacterial solution was then evenly spread on fresh Luria-Bertani (LB) agar plates, with each sample repeated three times, and incubated for 24 hours. Subsequently, bacterial colonies were photographed and their numbers were counted.

[0052] The antibacterial properties of the composite coating were evaluated using Escherichia coli and Staphylococcus aureus. The coated samples from Comparative Example 1 and Examples 1-3 were directly cultured with bacterial suspensions at a mass ratio of 1:2. The samples were immersed in 1×10⁻⁶... 6 CFU·mL -1 The diluted bacterial suspension was first incubated in a constant temperature shaker for 24 hours. PBS buffer (pH = 7.4) was added to Comparative Example 1 and Examples 1-3 to dilute the resulting suspension samples 1000-fold. Then, 100 µL of the diluted bacterial solution was evenly spread on fresh Luria-Bertani (LB) agar plates, with each sample repeated three times, and incubated for 24 hours. Subsequently, bacterial colonies were photographed and their numbers were counted.

[0053] like Figure 5 As shown in (a), a large number of dense E. coli colonies appeared on the Comparative Example 1 (pure gelatin coating) plate, indicating that the pure gelatin system lacks effective inhibitory effect on E. coli. Compared with the Comparative Example, the colony counts in Examples 1-3 were significantly reduced, showing a significant antibacterial effect. Specifically: Example 1 (5% aerogel): the number of colonies was significantly reduced, but a certain number of scattered colonies were still visible; Example 2 (10% aerogel): the number of colonies was further reduced, the plate was "cleaner" overall, and the residual colonies were minimal; Example 3 (20% aerogel): the number of colonies increased slightly compared to Example 2, but was still significantly lower than that in Comparative Example 1. Figure 5As shown in (b), a large number of dense and widely distributed colonies were observed on the plate of Comparative Example 1, indicating that the pure gelatin system had almost no inhibitory effect on Staphylococcus aureus. In contrast, the number of colonies on the plate of Example 1 was significantly reduced, with only a few scattered colonies observed, indicating that the composite coating had produced a clear antibacterial / bacteriostatic effect. The number of colonies in Example 2 was further reduced, with only a very few residual colonies on the plate, showing the strongest antibacterial performance in this group of samples. The number of colonies on the plate of Example 3 (20% aerogel) showed a significant rebound. This indicates that when the aerogel content is too high, the antibacterial effectiveness of the composite system cannot be maintained, and there is an "optimal content window," rather than a monotonous increase with the aerogel content. As a hydrophilic protein matrix, gelatin may provide a certain nutrient / adhesion environment for bacterial growth, thus exhibiting a high level of colony formation, which easily provides a favorable interface environment for bacterial adhesion and reproduction, resulting in a high colony formation rate. After introducing aerogel and flame retardant, the antibacterial performance of the coating was significantly improved, with the colony count of the 10% aerogel composite coating dropping to the lowest level, showing the best antibacterial effect. However, when the aerogel content increased to 20%, the colony count rebounded significantly, indicating that there is an optimal addition window for antibacterial performance.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating, characterized in that, Includes the following steps: (1) Preparation of piperazine hydroxyethylidene diphosphonate: Piperazine and hydroxyethylidene diphosphonic acid were prepared in a molar ratio of 1 to 2:

1. Piperazine was dissolved in anhydrous ethanol, and an ethanol solution of hydroxyethylidene diphosphonic acid was added dropwise under stirring. The reaction was carried out at a certain temperature to obtain a white solid product. The product was washed by centrifugation with anhydrous ethanol and dried to constant weight to obtain piperazine hydroxyethylidene diphosphonate, denoted as HEFER. (2) Preparation of polyethylene glycol modified phytic acid: Phytic acid and polyethylene glycol were mixed at a PA:PEG molar ratio of 1:1 to 6. The phytic acid solution was first heated in an oil bath at a certain temperature and filled with an inert atmosphere to remove moisture. Then, polyethylene glycol was added and heated under an inert atmosphere to react, yielding polyethylene glycol-modified phytic acid, denoted as PAPEG. (3) Preparation of composite flame-retardant and antibacterial components: HEFER and PAPEG are mixed at a molar ratio of HEFER:PAPEG of 1 to 3:1, deionized water is added, and the mixture is stirred at 60 to 80°C to form a homogeneous solution. The solution is then dried to obtain a composite flame retardant and antibacterial component, denoted as PAGHR. (4) Preparation and application of the coating system: PAGHR, aerogel and gelatin are mixed at a mass ratio of 0.1-1:0.01-1:1, deionized water is added, and the mixture is stirred at 60-80°C until it is uniformly dispersed to obtain a coating solution. The coating solution is applied to the surface of the substrate and dried and cured to obtain a bio-based fireproof, heat-insulating and antibacterial coating.

2. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: The aerogel is a silica aerogel with a particle size of 7~30nm.

3. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (1), the reaction stirring time is 4 to 6 hours.

4. The method for preparing the high-efficiency bio-based fireproof, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (2), the structural formula of polyethylene glycol is HO(CH2CH2O). n H, with a number-average molecular weight Mn of 200–2000; reaction temperature of 130–150℃, reaction time of 5–6 h, and carried out under nitrogen protection.

5. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (3), the stirring time is 0.5 to 2 hours.

6. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (3), the drying step is carried out in an oven at a temperature of 80-100°C for 12-18 hours.

7. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (4), the stirring time is 1 to 3 hours.

8. The method for preparing the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating according to claim 1, characterized in that: In step (4), the coating method includes one or more of brushing, roller coating, and spraying; when the substrate is wood, the coating coverage per unit area after drying is 100-300 g / m². 2 .

9. A high-efficiency bio-based fireproof, heat-insulating, and antibacterial coating prepared by any one of claims 1-8.

10. The application of the high-efficiency bio-based fire-retardant, heat-insulating, and antibacterial coating of claim 9 on the surface of wood, bamboo, engineered wood, or their composite materials, characterized in that: It imparts one or more of the following properties to the substrate: flame retardant, heat insulation, and antibacterial / antifungal properties.

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