A cellulose antibacterial coating and its preparation method

Abstract

This invention discloses a cellulose antibacterial coating, belonging to the field of cellulose technology. The cellulose antibacterial coating, by weight, comprises the following components: 8-15 parts TPP-modified cellulose, 1-2 parts heptadecafluorodecyltrimethoxysilane, 1-1.5 parts isocyanate, 0.3-0.7 parts nano-silica, 65-70 parts anhydrous ethanol, and 18-20 parts tetrahydrofuran. This invention overcomes the limitations of traditional antibacterial agents by combining flexible alkyl chains with rigid quaternary phosphonium salt TPP molecules; silane pre-hydrolysis directional grafting technology achieves chemical bond anchoring; and electrostatic spraying and vapor deposition are combined to achieve efficient coating preparation on cross-scale substrates. Through multi-mechanism synergy, chemical bonding, and intelligent surface design, this invention provides a reliable solution for the large-scale application of cellulose antibacterial coatings in medical, food packaging, and environmental engineering fields.

Description

Technical Field

[0001] This invention belongs to the field of cellulose technology, specifically relating to a cellulose antibacterial coating and its preparation method. Background Technology

[0002] Traditional cellulose antibacterial coatings are mainly achieved through physical adsorption or blending modification, specifically including impregnation loading methods, such as immersing cellulose in silver nanoparticles or quaternary ammonium salt solutions, relying on hydrogen bonds and van der Waals forces for adsorption; melt blending methods; and surface coating methods. However, these methods face multiple technical challenges: physically adsorbed antibacterial agents are easily eluted, and silver nanoparticles suffer from slow-release runaway issues; silver ions can also cause ecotoxicity due to bioaccumulation. Functionally, it is difficult to achieve both antibacterial and antifungal effects, and they lack anti-biofilm capabilities; during processing, high-temperature melting can destroy the cellulose hydrogen bond network, leading to a 30% decrease in strength, and solvent residues can also cause cytotoxicity. Although existing patents attempt to improve the coating through chemical modification, they still suffer from low Gram-negative antibacterial rates and fail to resolve the core contradiction between drug resistance and long-term effectiveness. Therefore, there is an urgent need to develop antibacterial coating technologies with high grafting rates, zero release, and multi-mechanism synergy. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention provides a cellulose antibacterial coating and its preparation method. By designing TPP-modified cellulose, the cellulose antibacterial coating achieves improvements in long-lasting effect, safety and performance.

[0004] The technical solution for achieving the objective of this invention is as follows:

[0005] A cellulose antibacterial coating, by weight, comprises the following components: 8-15 parts of TPP modified cellulose, 1-2 parts of heptadecafluorodecyltrimethoxysilane, 1-1.5 parts of isocyanate, 0.3-0.7 parts of nano-silica, 65-70 parts of anhydrous ethanol, and 18-20 parts of tetrahydrofuran.

[0006] Preferably, the isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

[0007] A method for preparing a cellulose antibacterial coating involves weighing raw materials according to weight, adding heptadecafluorodecyltrimethoxysilane to tetrahydrofuran under an argon atmosphere, adding TPP-modified cellulose and ultrasonically dispersing for 5-10 min, adding nano-silica and isocyanate sequentially, and finally adding anhydrous ethanol. The mixture is then sheared and dispersed at 8000-12000 rpm for 5-15 min to prepare a cellulose antibacterial coating liquid, which is then coated onto the surface of a substrate and dried to form a cellulose antibacterial coating.

[0008] An application of a cellulose antibacterial coating involves applying TPP-modified cellulose to a residential fresh air system, including the following steps:

[0009] Stainless steel filter screen is selected. After ultrasonication at 50-70℃ for 10-30 min with a 5% sodium hydroxide solution and plasma activation, cellulose antibacterial coating liquid is electrostatically sprayed at 15 kV and 25 cm spray distance to form a 4-5 μm coating on the filter screen surface. After gradient curing, hexamethyldisilazane is vapor-deposited and then immersed in a 0.1 mol / L cold ammonium hexafluorophosphate acetone solution for 5-10 min. The filter screen is then installed downstream of the primary filter screen.

[0010] The preparation method of the TPP-modified cellulose includes the following steps:

[0011] (a) Silanization of cellulose surface: 1 eq of cellulose was placed in a vacuum drying oven and dried under vacuum at 110~120℃ for 20~24 h. It was then transferred to an argon glove box, and pre-hydrolyzed silane coupling agent was added. The reaction was carried out at 40~45℃ for 1~2 h. After that, it was washed three times by centrifugation with cold ethanol and cyclohexane to obtain silanized cellulose.

[0012] (b) TPP molecule grafting: Under an argon atmosphere, 1.2 eq of TPP molecules were dissolved in anhydrous N,N-dimethylformamide, cooled to 0°C in an ice bath, and 1.8 eq of condensing agent and 0.3 eq of HOAt were added dropwise. Then, silanized cellulose was added dropwise at 0°C, with the temperature controlled at ≤10°C. After the addition was complete, the reaction was carried out in the dark for 20-24 h. 1 eq of sodium bromide was added, and the reaction solution was precipitated with cold diethyl ether. The solution was washed with a pre-cooled sodium bicarbonate solution of 0.5 mol / L, an acetone solution of saturated ammonium bromide, and a 50% ethanol solution. After freeze-drying, TPP modified cellulose was obtained.

[0013] Preferably, the pre-hydrolyzed silane coupling agent is obtained by dissolving 0.6 eq of silane coupling agent in a mixed solution of ethanol and water in a volume ratio of 4:1, adding 0.1% acetic acid by mass, and stirring at 40°C for 1 h to obtain a silanol activated solution.

[0014] Preferably, the silane coupling agent is 3-aminopropyltriethoxysilane.

[0015] Preferably, the condensing agent is diisopropylcarbodiimide.

[0016] Preferably, the freeze-drying is performed at -70 to -80°C for 2 to 3 hours, followed by drying at -40 to -50°C for 10 to 12 hours, and finally drying at a temperature gradient of 0.5°C / min from -30°C to 25°C for 6 to 7 hours.

[0017] The method for preparing the TPP molecule includes the following steps:

[0018] (1) Synthesis of 2-carboxyethyltriphenylphosphonium: 1 eq of 1-bromopropionic acid and 1.5 eq of triphenylphosphine were mixed in acetonitrile and refluxed in an oil bath at 80 °C for 2 h. After the reaction was completed, the solvent was removed by vacuum distillation and 2-carboxyethyltriphenylphosphonium was obtained by silica gel column chromatography.

[0019] (2) Synthesis of aminocarboxylic acid compounds: 1 eq of N-Boc-L-phenylalanine was dissolved in N,N-dimethylformamide. The mixture was cooled in an ice-water bath at 0°C. 1.2 eq of glycine methyl ester hydrochloride was neutralized, extracted with ethyl acetate, and concentrated to obtain glycine methyl ester. This solution was added to the reaction system, and 1.2 eq of N,N'-dicyclohexylcarbodiimide and 1.2 eq of 1-hydroxybenzotriazole were added sequentially. The reaction solution was stirred in an ice bath for 30-36 h. Then, it was filtered and extracted through a sintered glass frit funnel, and Boc-L-phenylalanylglycine methyl ester was obtained by silica gel column chromatography. 1 eq of the product from the previous step was dissolved in methanol, and 1.7 eq of 1 mol / L NaOH solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, methanol was removed by vacuum distillation. The residue was dissolved in water and washed with diethyl ether. The aqueous phase was separated by silica gel column chromatography. The pH was adjusted to 2.0–2.5 with mol / L hydrochloric acid solution, and the target compound was obtained by extraction and silica gel column chromatography. 1 eq of the product from the previous step was dissolved in a 1:1 mixture of N,N-dimethylformamide and ethyl acetate, and cooled to 0°C in an ice-water bath. 1.2 eq of 1-hydroxybenzotriazole, 1 eq of 6-aminohexanoic acid dissolved in ethyl acetate, and finally 1.2 eq of N,N'-dicyclohexylcarbodiimide were added sequentially. The ice bath was removed, and the reaction system was brought to room temperature and stirred continuously for 24 h. The reaction solution was filtered to remove the byproduct N,N-dicyclohexylurea. The organic phase was washed and extracted sequentially with 1 mol / L hydrochloric acid solution, and the target product was obtained as a white powder by silica gel column chromatography. 1 eq of the product from the previous step was placed in a reaction vessel, 20 eq of formic acid was added, and the mixture was stirred at room temperature for 24 h. h; After the reaction was completed, formic acid was removed by vacuum distillation, the residue was dissolved in water, the pH of the aqueous phase was adjusted to 7.5-8.5 with saturated sodium carbonate solution, extracted with ethyl acetate, and the target product, aminocarboxylic acid compound, was obtained by alkaline alumina column chromatography.

[0020] (3) Synthesis of TPP molecule: 1 eq of the aminocarboxylic acid compound from the previous step was dissolved in a mixed solvent of DMF and ethyl acetate in a volume ratio of 1:1. 1 eq of 2-carboxyethyltriphenylphosphonium obtained in step (1) was added. After cooling the mixture in an ice-water bath at 0°C, 0.8 eq of N,N'-dicyclohexylcarbodiimide and 0.8 eq of 1-hydroxybenzotriazole were added sequentially. The reaction system was gradually raised to room temperature under ice bath conditions and stirred continuously for 48 h. After filtration and extraction, the target product TPP molecule was obtained by silica gel column chromatography. Its structure is shown in the following formula:

[0021] .

[0022] Preferably, the extraction includes the following steps: washing the organic phase with saturated brine, combining the organic phases and extracting with ethyl acetate, drying with anhydrous sodium sulfate, and concentrating under reduced pressure to obtain the crude product.

[0023] Beneficial effects

[0024] The present invention has the following beneficial effects:

[0025] This invention, through the design of TPP-modified cellulose, achieves improvements in the longevity, safety, and functional integration of cellulose antibacterial coatings. Its core advantages are reflected in the following aspects:

[0026] 1. Enhanced antibacterial properties: Through the synergistic effect of quaternary phosphonium salt cations and long alkyl chains, the coating achieves deep destruction of bacteria: phosphonium cations disrupt the bacterial membrane potential and increase membrane permeability through positive and negative charge interactions, while alkyl chains insert into the bacterial lipid bilayer to form physical membrane disruption; this composite mechanism significantly enhances antibacterial efficacy, achieving an inhibition rate of 99.99% against Staphylococcus aureus and Klebsiella pneumoniae.

[0027] 2. Superior durability and environmental stability

[0028] The coating forms Si-OC covalent bonds through silane pre-hydrolysis directional grafting technology, resulting in high antibacterial durability, which is superior to traditional physical adsorption coatings.

[0029] 3. Improved anti-mildew performance

[0030] The superhydrophobic surface constructed from heptadecafluorodecyltrimethoxysilane enables the coating to achieve a mold resistance rating of 0, effectively inhibiting microbial adhesion and proliferation.

[0031] 4. Wide range of applications

[0032] This technology is adaptable to a variety of substrates such as cotton fabrics, filter membranes, and medical dressings. It achieves precise control of the coating thickness of stainless steel filter screens through electrostatic spraying and vapor deposition, demonstrating strong cross-scale applicability and significant economic and social benefits.

[0033] In summary, this invention is the first to design a combination of flexible alkyl chains and rigid quaternary phosphonium salt TPP molecules, overcoming the limitations of traditional single-mechanism antibacterial agents; silane pre-hydrolysis directional grafting technology achieves chemical bond anchoring; and the combination of electrostatic spraying and vapor deposition enables efficient coating preparation on substrates across scales. This technology, through multi-mechanism synergy, chemical bonding, and intelligent surface design, provides a reliable solution for the large-scale application of cellulose antibacterial coatings in medical, food packaging, and environmental engineering fields. Attached Figure Description

[0034] Figure 1 The synthetic route for TPP-modified cellulose;

[0035] Figure 2 The nuclear magnetic resonance spectrum of TPP molecule 1;

[0036] Figure 3 Infrared spectra of cellulose, TPP molecule 1, and TPP-modified cellulose 1. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0039] The raw materials and equipment used in the embodiments and comparative examples are described below:

[0040] 2-Carboxyethyltriphenylphosphonium: Prepared in-house, the preparation method is as follows:

[0041] 1 eq of 1-bromopropionic acid and 1.5 eq of triphenylphosphine were mixed in acetonitrile and refluxed in an oil bath at 80 °C for 2 h. After the reaction was completed, the solvent was removed by vacuum distillation, and 2-carboxyethyltriphenylphosphine was obtained by silica gel column chromatography.

[0042] Aminocarboxylic acid compound 1: prepared in-house, as follows:

[0043] 1 eq of N-Boc-L-phenylalanine was dissolved in N,N-dimethylformamide. The mixture was cooled in an ice-water bath at 0°C. 1.2 eq of glycine methyl ester hydrochloride was neutralized, extracted with ethyl acetate, and concentrated to obtain glycine methyl ester. This solution was added to the reaction system, and immediately 1.2 eq of N,N'-dicyclohexylcarbodiimide and 1.2 eq of 1-hydroxybenzotriazole were added sequentially. The reaction solution was stirred in an ice bath for 30–36 h, then filtered and extracted through a sintered glass frit funnel, and Boc-L-phenylalanylglycine methyl ester was obtained by silica gel column chromatography. 1 eq of the product from the previous step was dissolved in methanol, and 1.7 eq of 1 mol / L NaOH solution was added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, methanol was removed by vacuum distillation, the residue was dissolved in water, washed with diethyl ether, and the pH of the aqueous phase was adjusted to 2 with 1 mol / L hydrochloric acid solution. The target compound was obtained by extraction and silica gel column chromatography. The product from the previous step was dissolved in a 1:1 mixture of N,N-dimethylformamide and ethyl acetate, and then cooled to 0°C in an ice-water bath. 1.2 eq of 1-hydroxybenzotriazole, 1 eq of 6-aminohexanoic acid dissolved in ethyl acetate, and finally 1.2 eq of N,N'-dicyclohexylcarbodiimide were added sequentially. The ice bath was removed, and the reaction system was brought to room temperature and stirred continuously for 24 h. The reaction solution was filtered to remove the byproduct N,N-dicyclohexylurea. The organic phase was washed and extracted sequentially with 1 mol / L hydrochloric acid solution, and the target product was obtained as a white powder by silica gel column chromatography. 1 eq of the product from the previous step was placed in a reaction vessel, and 20 eq of formic acid was added. The mixture was stirred at room temperature for 24 h. After the reaction was complete, the formic acid was removed by vacuum distillation. The residue was dissolved in water, and the pH of the aqueous phase was adjusted to 7.5–8.5 with saturated sodium carbonate solution. Extraction with ethyl acetate and alkaline alumina column chromatography were used to obtain the white solid target product, aminocarboxylic acid compound 1.

[0044] Aminocarboxylic acid compound 2: prepared in-house, the preparation method is the same as that of aminocarboxylic acid compound 1, except that 6-aminohexanoic acid is replaced with β-alanine, while all other conditions remain unchanged, to obtain aminocarboxylic acid compound 2.

[0045] Aminoalkyl compound 3: prepared in-house, the preparation method is the same as that of aminocarboxylic acid compound 1, except that the added 6-aminohexanoic acid is replaced with n-hexylamine;

[0046] Silane coupling agent: 3-aminopropyltriethoxysilane, product number A107147, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Condensing agent: diisopropylcarbodiimide, commercially available;

[0048] Triphenylphosphine: Product number T104475, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0049] N-Boc-L-phenylalanine: Purchased from Beijing Bainiannuan Technology Co., Ltd.;

[0050] Glycine methyl ester hydrochloride: Product number G810396, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0051] N,N'-Dicyclohexylcarbodiimide: Product No. D106074, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0052] 1-Hydroxybenzotriazole: Product No. 1059815, purchased from Tianjin Xiens Biochemical Technology Co., Ltd.;

[0053] 6-Aminohexanoic acid: Product number A800336, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0054] Cellulose: Microcrystalline cellulose, 40-60 μm, product number 1091391, purchased from Shanghai Haohong Biomedical Technology Co., Ltd.

[0055] HOAt: Product number H890201, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0056] Nano silica: 50 nm, product number S817567, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0057] n-Hexylamine: Product number H105333, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0058] Heptadecafluorodecyltrimethoxysilane: namely trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, product number 1111125, purchased from Shanghai Haohong Biomedical Technology Co., Ltd.

[0059] Isocyanate: Diphenylmethane diisocyanate, namely 4,4'-methylenebis(phenyl isocyanate), product number M106783, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0060] TPP molecule 1: Self-made, preparation method is as follows:

[0061] 1 eq of aminocarboxylic acid compound 1 was dissolved in a mixed solvent of DMF:ethyl acetate in a volume ratio of 1:1. 1 eq of 2-carboxyethyltriphenylphosphonium obtained in step (1) was added. After cooling the mixture in an ice-water bath at 0°C, 0.8 eq of N,N'-dicyclohexylcarbodiimide and 0.8 eq of 1-hydroxybenzotriazole were added sequentially. The reaction system was gradually raised to room temperature under ice bath conditions and stirred continuously for 48 h. After filtration and extraction, the target product TPP molecule was obtained by silica gel column chromatography. Its structure is shown in the following formula:

[0062] .

[0063] TPP molecule 2: Prepared in-house. The preparation method differs from that of TPP molecule 1 in that aminocarboxylic acid compound 1 is replaced with aminocarboxylic acid compound 2, while other conditions remain unchanged. The resulting TPP molecule 2 has the structure shown in the following formula:

[0064] .

[0065] TPP molecule 3: Prepared in-house. The preparation method differs from that of TPP molecule 1 in that the added aminocarboxylic acid compound 1 is replaced with aminoalkyl compound 3, while all other conditions remain unchanged. The resulting TPP molecule 3 has the structure shown in the following formula:

[0066] .

[0067] Molecular 4: Prepared in-house, the method differs from that of TPP molecule 1 in that the added 2-carboxyethyltriphenylphosphonium is replaced with hexanoic acid, while all other conditions remain unchanged, resulting in TPP molecule 4, the structure of which is shown below:

[0068] ;

[0069] Preparation Example

[0070] Preparation Example 1

[0071] TPP modified cellulose 1: Self-made, preparation method is as follows:

[0072] (a) Silanization of cellulose surface: 1 eq of cellulose was placed in a vacuum drying oven and dried under vacuum at 120°C for 24 h. It was then transferred to an argon glove box, and pre-hydrolyzed silane coupling agent was added. The mixture was reacted at 40°C for 1-2 h. After that, it was washed three times by centrifugation with cold ethanol and cyclohexane to obtain silanized cellulose.

[0073] (b) TPP molecule grafting: Under an argon atmosphere, 1.2 eq of TPP molecule 1 was dissolved in anhydrous N,N-dimethylformamide and cooled to 0°C in an ice bath. 1.8 eq of condensing agent and 0.3 eq of HOAt were added dropwise, followed by the dropwise addition of silanized cellulose at 0°C, with the temperature controlled at ≤10°C. After the addition was complete, the reaction was carried out in the dark for 24 h. 1 eq of sodium bromide was added, and the reaction solution was precipitated with cold diethyl ether. The solution was washed with a pre-cooled sodium bicarbonate solution of 0.5 mol / L, an acetone solution of saturated ammonium bromide, and a 50% ethanol solution. After freeze-drying, TPP modified cellulose 1 was obtained.

[0074] Preparation Example 2

[0075] TPP modified cellulose 2: self-made, the preparation method is the same as that of TPP modified cellulose 1, the difference is that the TPP molecule 1 used in step (2) is replaced with TPP molecule 2, and other conditions remain unchanged, to obtain TPP modified cellulose 2;

[0076] Preparation Example 3

[0077] TPP modified cellulose 3: self-made, the preparation method is the same as that of TPP modified cellulose 1, the difference is that the TPP molecule 1 used in step (2) is replaced with TPP molecule 3, and other conditions remain unchanged, to obtain TPP modified cellulose 3;

[0078] Preparation Example 4

[0079] TPP modified cellulose 4: self-made, the preparation method is the same as that of TPP modified cellulose 1, the difference is that the TPP molecule 1 used in step (2) is replaced with molecule 4, and other conditions remain unchanged, to obtain TPP modified cellulose 4;

[0080] Preparation Example 5

[0081] TPP modified cellulose 5: self-made, the preparation method is the same as that of TPP modified cellulose 1, the difference is that step (1) silanization of cellulose surface is not performed, and other conditions are unchanged, to obtain TPP modified cellulose 5;

[0082] Preparation Example 6

[0083] TPP-modified cellulose 6: In-house, 1 eq of dried microcrystalline cellulose, 1.2 eq of TPP-modified molecule 1 and 0.6 eq of pre-hydrolyzed silane coupling agent were added to a high-speed mixer and dry-mixed at 1000 rpm for 5 min; then wet-mixed with 0.5 eq of anhydrous ethanol for 10 min, and then melt-mixed at 80℃ for 200 rpm for 3 min in a twin-screw extruder. After water cooling and pelletizing, it was compressed into tablets to obtain TPP-modified cellulose 6.

[0084] Example

[0085] Examples 1-5 and Comparative Examples 1-3

[0086] Cellulose antibacterial coating: Weigh the raw materials according to the weight parts, add 1.5 parts of heptadecafluorodecyltrimethoxysilane to 19.8 parts of tetrahydrofuran under an argon atmosphere, add 8 parts of TPP modified cellulose and ultrasonically disperse for 5 min, then add 0.5 parts of nano silica, 1.2 parts of isocyanate, and finally add 69 parts of anhydrous ethanol. Disperse the mixture at 10000 rpm for 10 min to prepare the cellulose antibacterial coating liquid.

[0087] Table 1. Formulations of Examples 1-5 and Comparative Examples 1-3 (by weight)

[0088]

[0089] The following are the test methods for performance parameters involved in this invention:

[0090] 1. NMR spectrum: 400 MHz NMR spectrometer (Bruker, Germany);

[0091] 2. Fourier transform infrared spectroscopy (FTIR) measurement: Model Spectrum two, PerkinElmer, USA;

[0092] 3. Antibacterial rate: Tested according to GB / T 21866-2008, the test species are Staphylococcus aureus (AS1.89) and Klebsiella pneumoniae (AS1.1736).

[0093] 4. Antibacterial durability: The test was conducted according to GB / T 21866-2008 "Determination of antibacterial properties and antibacterial effect of antibacterial coatings (films)". A 30W ultraviolet lamp with a wavelength of 253.7nm was used. The ultraviolet lamp conformed to GB19258. The antibacterial coating test plate was placed 0.8m~1.0m away from the ultraviolet lamp and irradiated for 100h.

[0094] 5. Anti-mildew performance: Tested according to GB / T 1741-2020 "Determination of resistance to mold and mildew of paint film".

[0095] Table 2 Performance test results of Examples 1-5 and Comparative Examples 1-3

[0096]

[0097] As shown in Table 2, Example 1 exhibits the best overall performance, achieving an antibacterial rate of 99.99% against Staphylococcus aureus and Klebsiella pneumoniae. This is attributed to the membrane penetration capability of the alkyl chain in TPP molecule 1, combined with the efficient destruction of the peptidoglycan layer by the quaternary phosphonium salt cation. The antibacterial durability is attributed to the Si-O-Si covalent bonds formed by silanization. The Grade 0 antifungal performance is attributed to the superhydrophobic surface imparted by heptadecafluorodecyltrimethoxysilane. In Example 2, the addition of less TPP-modified cellulose 1 by weight resulted in a slight decrease in antibacterial rate. In Example 3, the antibacterial rate remained at 99.74%, but the durability was slightly reduced, possibly due to steric hindrance. The antibacterial rate of Example 4 was lower than that of Example 1, presumably because its alkyl chain was too short, resulting in insufficient membrane penetration depth. In Example 5, the lack of carboxyl groups prevented the reaction with the silane coupling agent, leading to uneven coating distribution and a decrease in antifungal performance. The antibacterial rate of Comparative Example 1 plummeted to 68.2%, demonstrating that the ion-mediated membrane breaking mechanism is irreplaceable. Comparative Example 2, dominated by physical adsorption, had a durability of only 71% of that of Example 1. Although Comparative Example 3 maintained an initial antibacterial rate of 92% due to fluorosilane, the processing disrupted the cellulose hydrogen bond network, causing the durability to drop sharply to 52.8%.

[0098] In summary, the performance triangle of this antibacterial coating—highly efficient sterilization, long-lasting durability, and mildew prevention—must simultaneously satisfy the quaternary phosphonium salt ion membrane-breaking mechanism, C6-C8 alkyl chain membrane penetration, and silane covalent anchoring. The three-dimensional synergistic effect of Example 1 is currently the optimal solution, while the structural defects in the comparative example verify the irreplaceability of the above mechanism.

[0099] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cellulose antibacterial coating, characterized in that, By weight, it includes the following components: 8-15 parts of TPP modified cellulose, 1-2 parts of heptadecafluorodecyltrimethoxysilane, 1-1.5 parts of isocyanate, 0.3-0.7 parts of nano silica, 65-70 parts of anhydrous ethanol, and 18-20 parts of tetrahydrofuran. The preparation method of the TPP-modified cellulose includes the following steps: (a) Silanization of cellulose surface: cellulose is placed in a vacuum drying oven, and after vacuum drying, it is transferred to an argon glove box, pre-hydrolyzed silane coupling agent is added, and the mixture is heated to 40~45℃. After the reaction is completed, the silanized cellulose is obtained by washing. (b) TPP molecule grafting: TPP molecules were dissolved in anhydrous N,N-dimethylformamide under an argon atmosphere. A condensing agent and HOAt were added dropwise under ice bath conditions. Then, silanized cellulose was added dropwise under ice bath conditions, with the temperature controlled at ≤10℃. After the addition was completed, the reaction was carried out in the dark for 20~24 h. Sodium bromide was added. The reaction solution was washed and freeze-dried to obtain TPP modified cellulose. The structure of the TPP-modified cellulose is shown in Formula 1: Equation 1.

2. The cellulose antibacterial coating as described in claim 1, characterized in that, The isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

3. The cellulose antibacterial coating as described in claim 1, characterized in that, The pre-hydrolyzed silane coupling agent is prepared by dissolving the silane coupling agent in a mixed solution of ethanol and water, adding an aqueous solution of acetic acid, and stirring at 30-50°C to obtain a silanol activated solution; the silane coupling agent is 3-aminopropyltriethoxysilane; the condensing agent is diisopropylcarbodiimide; the freeze-drying is performed by drying at -70 to -80°C for 2-3 hours, then drying at -40 to -50°C for 10-12 hours, and finally drying at a gradient temperature of 0.5°C / min from -30°C to 25°C for 6-7 hours.

4. The cellulose antibacterial coating as described in claim 1, characterized in that, The method for preparing the TPP molecule includes the following steps: (1) Synthesis of 2-carboxyethyltriphenylphosphonium bromide: Bromopropionic acid and triphenylphosphine were mixed in acetonitrile and refluxed; after the reaction was completed, the solvent was removed by vacuum distillation, and 2-carboxyethyltriphenylphosphonium bromide was obtained by silica gel column chromatography. (2) Synthesis of aminocarboxylic acid compounds: N-Boc-L-phenylalanine was dissolved and cooled in an ice-water bath. Glycine methyl ester hydrochloride was neutralized, extracted, and concentrated to obtain glycine methyl ester. Glycine methyl ester was added to the reaction system. N,N'-dicyclohexylcarbodiimide and 1-hydroxybenzotriazole were added sequentially. The mixture was stirred in an ice bath, filtered and extracted through a sintered glass frit funnel, and Boc-L-phenylalanylglycine methyl ester was obtained by silica gel column chromatography. The methyl ester was then dissolved in methanol, and NaOH solution was added. The mixture was stirred at room temperature. After the reaction was completed, methanol was removed by vacuum distillation. The residue was dissolved in water and washed with diethyl ether. The pH of the aqueous phase was adjusted to 2.0-2.5 with hydrochloric acid solution. The target compound was obtained by extraction and silica gel column chromatography. The product from the previous step was subjected to N,N'-dicyclohexylcarbodiimide and 1-hydroxybenzotriazole. - Dimethylformamide: After dissolving in a mixed solvent of ethyl acetate, the mixture was placed in an ice-water bath. 1-Hydroxybenzotriazole, 6-aminohexanoic acid dissolved in ethyl acetate, and finally N,N'-dicyclohexylcarbodiimide were added sequentially. The ice bath was removed, and the reaction system was brought to room temperature with continuous stirring. The reaction solution was filtered to remove the byproduct N,N-dicyclohexylurea. The organic phase was washed and extracted sequentially with hydrochloric acid solution, and the target product was obtained by silica gel column chromatography. The product from the previous step was placed in a reaction vessel, formic acid was added, and the mixture was stirred at room temperature. After the reaction was complete, the formic acid was removed by vacuum distillation. The residue was dissolved in water, and the pH of the aqueous phase was adjusted to 7.5-8.5 with saturated sodium carbonate solution. Extraction with ethyl acetate and alkaline alumina column chromatography were used to obtain the white solid target product, an aminocarboxylic acid compound. (3) Synthesis of TPP molecule: The aminocarboxylic acid compound produced in the previous step was dissolved in a mixed solvent of DMF and ethyl acetate. 2-Carboxyethyltriphenylphosphonium bromide obtained in step (1) was added. After cooling in an ice-water bath, N,N'-dicyclohexylcarbodiimide and 1-hydroxybenzotriazole were added in sequence. The reaction system was gradually raised to room temperature under ice bath conditions and stirred continuously. After filtration and extraction, the target product TPP molecule was obtained by silica gel column chromatography. Its structure is shown in Formula 2: Equation 2.

5. A method for preparing a cellulose antibacterial coating as described in any one of claims 1 to 4, characterized in that, Weigh the raw materials according to the weight parts, add heptadecafluorodecyltrimethoxysilane to tetrahydrofuran under an argon atmosphere, add TPP modified cellulose and ultrasonically disperse for 5-10 min, add nano silica and isocyanate in sequence, and finally add anhydrous ethanol. The mixture is then sheared and dispersed at 8000-12000 rpm for 5-15 min to prepare a cellulose antibacterial coating liquid. Coat the substrate surface with the liquid and dry it to form a cellulose antibacterial coating.

6. The application of a cellulose antibacterial coating as described in any one of claims 1 to 4, characterized in that, The application of TPP-modified cellulose in residential fresh air systems includes the following steps: Stainless steel filter screen is selected, and after being ultrasonically activated with sodium hydroxide solution at 50~70℃ for 10~30 min and plasma activated, cellulose antibacterial coating liquid is electrostatically sprayed to form a 4~5 μm coating on the surface of the filter screen. After gradient curing, hexamethyldisilazane is vapor-deposited and then immersed in cold ammonium hexafluorophosphate acetone solution. The filter screen is then installed downstream of the primary filter screen.

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