Mildew-proof and antibacterial decorative film and preparation method thereof

Abstract

This application relates to the field of polyester biodegradable plastic film technology, mainly to an anti-mildew and antibacterial decorative film and its preparation method. An anti-mildew and antibacterial decorative film comprises: polylactic acid (PLA): 70-80 parts; polybutylene terephthalate (PET): 20-30 parts; silane coupling agent modified nano-silica: 1-3 parts; pH-sensitive chitosan-encapsulated silver ion microcapsules: 1-5 parts; diisocyanate: 0.1-1 parts; and catalyst: 0.001-0.02 parts. The preparation method includes: mixing PLA, PET, PET, silane coupling agent modified nano-silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules to obtain a mixture; the mixture, diisocyanate, and catalyst are melt-extruded to obtain a molten material; and the molten material is then formed into an anti-mildew and antibacterial decorative film. The film provided by this application has good mechanical properties, significant anti-mildew and antibacterial effects, and also possesses heat resistance.

Description

Technical Field

[0001] This application relates to the field of polyester biodegradable plastic film technology, and mainly to an anti-mildew and antibacterial decorative film and its preparation method. Background Technology

[0002] In the field of decorative films, polyester biodegradable plastics have attracted much attention due to their environmental friendliness. However, existing polyester biodegradable plastic decorative films face many challenges in practical applications.

[0003] First, the insufficient durability of antifungal and antibacterial properties is a significant problem. Traditional antifungal and antibacterial films typically achieve this by directly adding antibacterial agents to the polyester matrix, but this method has obvious drawbacks. Antibacterial agents easily migrate from the polyester matrix, especially in humid and high-temperature environments, where the migration rate is even faster. This leads to a rapid decrease in the concentration of antibacterial agents on the film surface, and the antifungal and antibacterial effect declines significantly over time. Furthermore, after long-term use, some microorganisms may develop resistance to a single antibacterial agent, further reducing the film's antibacterial efficacy.

[0004] Secondly, the poor mechanical properties of polyester biodegradable plastics limit their widespread application in decorative films. Compared to traditional general-purpose plastics such as polyethylene (PE) and polypropylene (PP), polyester biodegradable plastics, such as polylactic acid (PLA) and polybutylene adipate (PEG), typically have lower tensile strength, tear strength, and impact strength. This makes the film prone to damage or deformation under external forces, affecting its service life and aesthetics. For example, in applications such as furniture surfaces or wall decorations, the film needs to resist daily friction, scratches, and impacts. If its mechanical properties are insufficient, scratches and tears are likely to occur, significantly reducing its decorative effect and usability.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide an anti-mildew and antibacterial decorative film and its preparation method.

[0007] The technical solution of this application is as follows: An anti-mildew and antibacterial decorative film, comprising the following raw materials by weight: Polylactic acid: 70-80 parts; Polybutylene terephthalate (PET): 20-30 parts; Silane coupling agent modified nano-silica: 1-3 parts; pH-sensitive chitosan-encapsulated silver ion microcapsules: 1-5 parts; Diisocyanate: 0.1-1 part; Catalyst: 0.001-0.02 parts.

[0008] Furthermore, the preparation method of pH-sensitive chitosan-encapsulated silver ion microcapsules includes the following steps: Chitosan solution was prepared using chitosan and acetic acid. Prepare a silver ion antibacterial agent solution using water and silver ion antibacterial agent; Add the silver ion antibacterial agent solution dropwise to the chitosan solution and stir until homogeneous to obtain a mixed solution; pH-sensitive chitosan-encapsulated silver ion microcapsules were prepared by spray drying of the mixed solution; The weight ratio of silver ion antibacterial agent to chitosan is 1:(1-5).

[0009] Furthermore, the preparation method of silane coupling agent modified nano-silica includes the following steps: dispersing nano-silica in an alcohol solvent, stirring and reacting for 2-6 hours, and then filtering, washing and drying to obtain silane coupling agent modified nano-silica.

[0010] Furthermore, a 0.5-5% (w / v) chitosan solution is prepared using chitosan and acetic acid; The ratio of silver ion antibacterial agent to water is 1g: (90-110)mL.

[0011] Furthermore, the preparation of the chitosan solution includes: dissolving chitosan in a 0.1-2% (v / v) acetic acid solution and stirring until completely dissolved to obtain the chitosan solution.

[0012] Furthermore, the ratio of nano-silica to alcohol solvent is 1g: (8-12)mL; The weight ratio of nano-silica to silane coupling agent is 1:(0.01-0.1).

[0013] Furthermore, the diisocyanate includes one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate; The catalyst includes one or a mixture of two or more of the following: organotin catalysts, titanium-based catalysts, and organobismuth catalysts.

[0014] This application also provides a method for preparing an anti-mildew and antibacterial decorative film, comprising the following steps: A mixture of polylactic acid, polybutylene terephthalate, silane coupling agent-modified nano-silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules was prepared to obtain a mixture. The mixture of raw materials, diisocyanate, and catalyst is melt-extruded to obtain a molten material; Molten materials are processed into anti-mildew and antibacterial decorative films using casting or blown film processes.

[0015] Furthermore, the thickness is 45-55 μm.

[0016] Furthermore, the casting film process includes: extruding molten material onto a cooling roller, with the temperature of the cooling roller controlled at 25±5℃ and the traction speed at 4-6m / min; The blown film process includes: extruding molten material into an annular die, inflating the film with compressed air, with an inflation ratio of (2-3):1 and a traction speed of 8-12 m / min.

[0017] Regarding its anti-mold effect: The anti-mold and antibacterial decorative film's anti-mold effect primarily stems from a multi-faceted synergistic antibacterial mechanism. Its core component, pH-sensitive chitosan, encapsulates silver ion microcapsules, which dissolve and release silver ions in acidic environments (such as the acidic microenvironment created by mold metabolism). These silver ions directly kill mold by disrupting microbial cell membranes, inhibiting enzyme activity, and interfering with DNA replication, achieving targeted antibacterial action and long-lasting sustained release. Chitosan itself possesses cationic properties, which can adsorb mold cell membranes, causing leakage of contents and creating a dual antibacterial effect. Silane coupling agent-modified nano-silica is uniformly dispersed in the matrix, serving as a carrier for the antibacterial components and filling the film pores, reducing the space for mold adhesion, while simultaneously enhancing film density through chemical bonding. The cross-linking reaction of diisocyanate (HDI) and polylactic acid / PBAT forms a stable network structure, enhancing the film's mechanical strength and water resistance, and reducing the penetration of external moisture and mold spores.

[0018] Synergistic effect of silane coupling agent modified nano-silica and pH-sensitive chitosan-encapsulated silver ion microcapsules: 1. Interface Enhancement and Distributed Collaboration: KH-550 (aminopropyltriethoxysilane) introduces organic functional groups (such as -NH2, -OCH2CH3) onto the surface of nano-SiO2 through a hydrolysis-condensation reaction, forming an "inorganic-organic hybrid layer". This hybrid layer forms hydrogen bonds or chemical bonds with the hydroxyl (-OH) / carboxyl (-COOH) groups in the PLA-PBAT matrix, and simultaneously forms electrostatic adsorption or covalent bonds with the amino (-NH2) groups of the chitosan microcapsules, achieving interfacial coupling between inorganic nanoparticles and organic antibacterial microcapsules.

[0019] The modified SiO2 prevents the aggregation of pH-sensitive chitosan-encapsulated silver ion microcapsules in the PLA-PBAT matrix through steric hindrance and charge repulsion, ensuring uniform dispersion of both.

[0020] Specifically, the aminopropyl group (-NH2) of KH-550 forms hydrogen bonds or electrostatic adsorption with the amino group (-NH2) of chitosan, while its ethoxy group (-OCH2CH3) undergoes hydrolysis and chemically bonds with the hydroxyl group (-OH) of the PLA-PBAT matrix, constructing a three-dimensional network of "SiO2-chitosan-matrix". This interfacial coupling transforms the pH response behavior of chitosan microcapsules from "free swelling" to "constrained swelling". In acidic environments (pH≤6.5), when chitosan is protonated to -NH3⁺, the interfacial bonds restrict excessive extension of the molecular chains, preventing excessive expansion of the microcapsules that could lead to a sudden release of silver ions. In neutral / alkaline environments (pH≥7), when deprotonation causes chitosan to expand, the interfacial bonds provide a reverse constraint, making the swelling-contraction transition more sensitive and improving the pH response rate and accuracy.

[0021] Due to the aminopropyl matrix protonation of KH-550, the surface of the silane coupling agent-modified nano-silica is positively charged. This allows it to form electrostatic repulsion with the -NH3⁺ of the chitosan on the surface of pH-sensitive chitosan-encapsulated silver ion microcapsules. In acidic environments, this promotes the contraction of the microcapsule shell, reducing silver ion release. In neutral / alkaline environments, the increased negative charge on the surface of the silane coupling agent-modified nano-silica (ethoxy groups hydrolyze to produce -OH) forms electrostatic attraction with the deprotonated -NH2 of the chitosan on the surface of pH-sensitive chitosan-encapsulated silver ion microcapsules, promoting shell expansion. This achieves "charge-driven" pH response regulation, making the silver ion release rate linearly correlated with pH changes.

[0022] 2. Multiple enhancements of antibacterial properties through physical adsorption and chemical synergy: Modified SiO2 has a higher specific surface area, which allows it to better capture free silver ions (Ag⁺) through physical adsorption and electrostatic interactions, forming a "SiO2-Ag⁺" complex. This delays the burst release of silver ions and prolongs the antibacterial durability. Simultaneously, the rigid structure of SiO2 can mechanically penetrate microbial cell membranes, forming a three-tiered antibacterial mechanism of "physical-chemical-biological" action with silver ions (which disrupt DNA replication) and chitosan (which disrupts thiol groups in the cell membrane).

[0023] In acidic environments (such as mold-prone areas, pH ≤ 6.5), chitosan is protonated to -NH3⁺, and the molecular chains contract to encapsulate silver ions. At this time, the surface charge (positive charge) of the modified SiO2 and the positive charge of chitosan generate electrostatic repulsion, driving the microcapsule shell to contract, reducing silver ion release, and preventing excessive consumption. In neutral / alkaline environments (pH ≥ 7), chitosan deprotonates, the molecular chains extend, and the negatively charged surface of the silane coupling agent-modified nano-silica adsorbs anions, forming a "charge buffer layer," promoting the controlled release of silver ions and maintaining stable antibacterial activity within the pH range of 5-8.

[0024] 3. Balance between mechanical properties and functional stability: Silane coupling agent-modified nano-silica serves as a "nano-reinforcing phase," enhancing the mechanical properties and thermal stability of the film through its three-dimensional network structure. Simultaneously, the chitosan shell encapsulating silver ion microcapsules, composed of pH-sensitive chitosan, forms a "flexible protective layer" on the surface of the silane coupling agent-modified nano-silica. This alleviates stress concentration in the nanoparticles during processing, reduces microcrack formation, and improves the impact resistance and tear resistance of the antifungal and antibacterial decorative film.

[0025] The synergistic effect of silane coupling agent-modified nano-silica and pH-sensitive chitosan-encapsulated silver ion microcapsules slows down the initial degradation rate, ensuring the antibacterial function remains effective throughout the film's service life. In the later stages of degradation, the silane coupling agent-modified nano-silica, as an inorganic filler, can be slowly mineralized by soil microorganisms, avoiding environmental pollution.

[0026] Regarding heat resistance: the interfacial coupling between SiO2-chitosan-matrix can make the cross-linked network denser, improve heat conduction efficiency, and reduce the risk of local overheating.

[0027] Silane coupling agent-modified nano-silica, with its high specific surface area and rigid structure, forms a "nanoframework" in the film, which can effectively inhibit the slippage and recombination of molecular chains at high temperatures and reduce thermal shrinkage deformation. Its positive surface charge (in acidic environment) generates electrostatic repulsion with the -NH3⁺ of chitosan microcapsules, promoting the shrinkage of the microcapsule shell and avoiding local degradation caused by the sudden release of silver ions at high temperatures.

[0028] Compared with the prior art, this application has the following beneficial effects: 1. pH-sensitive chitosan-encapsulated silver ion microcapsules, in acidic environments (such as microenvironments with pH ≤ 6.5 produced by mold metabolism), cause chitosan to protonate to -NH3⁺, leading to molecular chain contraction and triggering the directional release of silver ions. Silver ions directly kill mold by disrupting the integrity of mold cell membranes, inhibiting respiratory chain enzyme activity, and interfering with DNA replication. The positive charge on the surface of silane-modified nano-silica generates electrostatic repulsion with the chitosan -NH3⁺, driving the microcapsule shell to contract and reducing the burst release of silver ions; simultaneously, its three-dimensional network structure fills the pores of the film, reducing the space for mold adhesion. The cross-linking network (reaction of HDI with PLA and PBAT) enhances the film's density, blocking external moisture and spore penetration, forming a three-dimensional anti-mold system of "release-blockage-inhibition" to ensure long-term anti-mold effects.

[0029] 2. Silver ions, as the core antibacterial agent, directly kill bacteria and fungi by disrupting cell membranes, inhibiting enzyme activity, and interfering with DNA replication. Chitosan's cationic properties adsorb negatively charged microbial cell membranes, causing leakage of contents and creating a synergistic chemical antibacterial effect. Silane coupling agent-modified nano-silica, with its high specific surface area, physically adsorbs silver ions to form a "SiO2-Ag⁺ complex," delaying silver ion release and prolonging the antibacterial effect. Its rigid structure can mechanically penetrate microbial cell membranes, enhancing physical antibacterial activity. Within the pH range of 5-8, through charge-driven response regulation, the silver ion release rate is linearly correlated with pH changes, ensuring stable and long-lasting antibacterial activity and forming a multi-layered antibacterial barrier of "chemical-physical-biological."

[0030] 3. Diisocyanate (HDI) chemically crosslinks with PLA and PBAT to form a three-dimensional network structure, significantly improving the tensile strength, impact resistance, and tear resistance of the film. Silane coupling agent-modified nano-silica serves as a "nano-reinforcing phase," constructing a "SiO2-chitosan-matrix" three-dimensional network through interfacial coupling (chemical bonding between the aminopropyl groups of KH-550 and the hydroxyl groups of the matrix, and electrostatic adsorption with the amino groups of chitosan). This alleviates processing stress concentration and reduces microcrack formation. Simultaneously, the chitosan shell forms a "flexible protective layer" on the surface of the nanoparticles, further enhancing the film's impact resistance and toughness, ensuring structural integrity under complex stress environments, and extending service life.

[0031] 4. Silane coupling agent-modified nano-silica forms a three-dimensional network structure with the matrix through chemical bonding, enhancing thermal conductivity and reducing the risk of degradation caused by localized overheating. The cross-linked network maintains structural stability at high temperatures, reducing thermo-oxidative degradation and ensuring that the film maintains excellent anti-mildew and antibacterial properties in high-temperature environments (such as indoor environments in summer). Detailed Implementation

[0032] To facilitate understanding of this application, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of this application.

[0033] This application provides an anti-mildew and antibacterial decorative film, comprising the following raw materials by weight: Polylactic acid: 70-80 parts; Polybutylene terephthalate (PET): 20-30 parts; Silane coupling agent modified nano-silica: 1-3 parts; pH-sensitive chitosan-encapsulated silver ion microcapsules: 1-5 parts; Diisocyanate: 0.1-1 part; Catalyst: 0.001-0.02 parts.

[0034] Diisocyanates include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), and diphenylmethane diisocyanate (MDI); preferably hexamethylene diisocyanate (HDI).

[0035] The catalyst includes organotin catalysts, titanium-based catalysts, and organobismuth catalysts; preferably organotin catalysts; more preferably dibutyltin dilaurate.

[0036] The preparation method of silane coupling agent modified nano-silica includes the following steps: Disperse nano-silica in an alcohol solvent and sonicate for 20-60 minutes. The ratio of nano-silica to alcohol solvent is 1g:(8-12)mL.

[0037] While stirring, slowly add the silane coupling agent dropwise and continue stirring for 2-6 hours. The weight ratio of nano-silica to silane coupling agent is 1:(0.01-0.1).

[0038] The mixture was filtered, washed multiple times with anhydrous ethanol, and vacuum dried for 12-24 hours to obtain silane coupling agent modified nano-silica.

[0039] The preparation method of pH-sensitive chitosan-encapsulated silver ion microcapsules includes the following steps: Step a: Prepare a 0.5-5% (w / v) chitosan solution: Chitosan (degree of deacetylation ≥ 90%) is dissolved in 0.1-2% (v / v) acetic acid solution and stirred until completely dissolved to obtain chitosan solution.

[0040] Step b: Prepare silver ion antibacterial agent solution: Dissolve commercially available silver ion antibacterial agent in deionized water to obtain a silver ion antibacterial agent solution.

[0041] The ratio of silver ion antibacterial agent to water is 1g: (90-110)mL.

[0042] The weight ratio of silver ion antibacterial agent to chitosan is 1:(1-5).

[0043] Step c: Slowly add the silver ion antibacterial agent solution dropwise to the chitosan solution, stir evenly, and obtain a mixed solution.

[0044] Step d: Microcapsules were prepared using spray drying. The mixed solution was spray-dried using a spray dryer to collect pH-sensitive chitosan-encapsulated silver ion microcapsules.

[0045] Spray drying parameters: inlet air temperature 125-135℃, outlet air temperature 75-85℃, spray pressure 0.1-0.2MPa.

[0046] This application also provides a method for preparing an anti-mildew and antibacterial decorative film, comprising the following steps: Step 1: Dry polylactic acid and polybutylene terephthalate under vacuum at 75-85℃ for 12-36 hours.

[0047] Step 2: Add the dried polylactic acid, polybutylene terephthalate-adipate, silane coupling agent modified nano-silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules into a high-speed mixer and mix at 950-1100 rpm for 1-10 minutes to obtain the mixture.

[0048] Step 3: The mixture is melt-extruded through a twin-screw extruder; during the extrusion process, diisocyanate (hexamethylene diisocyanate) and catalyst (dibutyltin dilaurate) are added to carry out chemical cross-linking.

[0049] The material is obtained by extrusion.

[0050] The extruder temperatures are set as follows: 155-165℃ (feed zone), 165-175℃, 175-185℃, 180-190℃, 185-195℃ (die). The screw speed is set to 140-160 rpm.

[0051] The design employs a temperature gradient of 160-190℃ to ensure that PLA and PBAT are fully melted and mixed, and that the cross-linking reaction is complete, forming a stable chemical cross-linking network and improving thermal stability.

[0052] Step 4: The molten material is processed into an anti-mildew and antibacterial decorative film using a casting or blown film process, specifically as follows: Cast film: Molten material is extruded onto a cooling roller, the temperature of which is controlled at 25±5℃, and the traction speed is 4-6m / min, to obtain a mildew-proof and antibacterial decorative film with a thickness of 45-55μm.

[0053] Film blowing: The molten material is extruded into an annular die head, and the film is blown up by compressed air. The blowing ratio is (2-3):1, and the traction speed is 8-12m / min, to obtain a mildew-proof and antibacterial decorative film with a thickness of 45-55μm.

[0054] Further, step 5: cooling: cast film is cooled by cooling rollers, and blown film is cooled by air rings to ensure rapid cooling and shaping of the anti-mildew and antibacterial decorative film.

[0055] The present application will be further described below through specific embodiments. Example 1

[0056] An anti-mildew and antibacterial decorative film, comprising the following raw materials: Polylactic acid: 75 kg, purchased in this example from Ingeo 4043D, NatureWorks LLC; Polybutylene terephthalate (PET): 25 kg, purchased from Ecoflex F Blend C1200, BASF in this example; Silane coupling agent modified nano-silica: 1.5 kg; pH-sensitive chitosan-encapsulated silver ion microcapsules: 3kg; Diisocyanate: 0.3 kg; Catalyst: 0.01 kg.

[0057] The diisocyanate is hexamethylene diisocyanate (HDI).

[0058] The catalyst is dibutyltin dilaurate.

[0059] The preparation method of silane coupling agent modified nano-silica includes the following steps: 5 kg of nano silica (Evonik's AEROSIL 200) was dispersed in 50 L of anhydrous ethanol and ultrasonically dispersed for 30 minutes.

[0060] While stirring, slowly add 0.3 kg of KH-550 (commercially available) dropwise, and continue stirring for 4 hours.

[0061] The sample was filtered, washed three times with anhydrous ethanol, and vacuum dried for 12 hours to obtain silane coupling agent modified nano-silica.

[0062] The preparation method of pH-sensitive chitosan-encapsulated silver ion microcapsules includes the following steps: Step a: Prepare chitosan solution: Dissolve 1 kg of chitosan (degree of deacetylation ≥ 90%, commercially available) in 100 L of 1% (v / v) acetic acid solution and stir until completely dissolved to obtain a chitosan solution.

[0063] Step b: Prepare silver ion antibacterial agent solution: 0.5 kg of silver ion antibacterial agent (commercially available; in this example, it was purchased from Sanitary in Switzerland, model BCA21-61) was dissolved in 50 L of deionized water to obtain a silver ion antibacterial agent solution.

[0064] Step c: Slowly add the silver ion antibacterial agent solution dropwise to the chitosan solution, stir evenly, and obtain a mixed solution.

[0065] Step d: Microcapsules were prepared using spray drying. The mixed solution was spray-dried using a spray dryer to collect pH-sensitive chitosan-encapsulated silver ion microcapsules.

[0066] Spray drying parameters: inlet air temperature 130℃, outlet air temperature 80℃, spray pressure 0.15MPa.

[0067] This embodiment also provides a method for preparing an anti-mildew and antibacterial decorative film, including the following steps: Step 1: Dry polylactic acid and polybutylene terephthalate under vacuum at 80°C for 12 hours.

[0068] Step 2: Add the dried polylactic acid, polybutylene terephthalate-adipate, silane coupling agent modified nano-silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules to a high-speed mixer and mix at 1000 rpm for 10 minutes to obtain the mixture.

[0069] Step 3: The mixture is melt-extruded through a twin-screw extruder; during the extrusion process, diisocyanate (hexamethylene diisocyanate) and catalyst (dibutyltin dilaurate) are added to carry out chemical cross-linking.

[0070] The material is obtained by extrusion.

[0071] The extruder temperatures are set as follows: 160℃ (feed zone), 170℃, 180℃, 185℃, 190℃ (die). The screw speed is set to 150 rpm.

[0072] Step 4: The molten material is processed into an anti-mildew and antibacterial decorative film using a blown film process, including: The molten material is extruded into an annular die, and the film is inflated by compressed air at an inflation ratio of 2:1 and a traction speed of 10m / min to obtain a 50μm thick anti-mildew and antibacterial decorative film.

[0073] Step 5: Cooling: Use air ring cooling to ensure rapid cooling and shaping of the anti-mildew and antibacterial decorative film.

[0074] Performance testing: 1. Tensile strength: Tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The test speed is 50 mm / min.

[0075] 2. Antibacterial properties: Tested according to GB / T 21510-2008 "Test Method for Antibacterial Properties of Nano-Inorganic Materials". The test strain was Escherichia coli.

[0076] 3. Anti-mildew performance: Referring to the standard GB / T24128-2009 "Test method for anti-mildew performance of plastics", Aspergillus niger AS3.315 is used as the test object. The growth of mold on the standard strips made of anti-mildew and antibacterial decorative film is tested and rated.

[0077] 4. Moisture and heat resistance: The anti-mildew and antibacterial decorative film was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 7 days. After removal, the tensile strength and antibacterial properties were tested again.

[0078] Test results: 1. Tensile strength: 42MPa.

[0079] 2. Antibacterial properties: 99.5% (24 hours).

[0080] 3. Anti-mildew performance: Grade 0.

[0081] 4. Resistance to damp heat: 40MPa, 99.0% (24 hours).

[0082] Comparative Example 1 An anti-mildew and antibacterial decorative film, comprising the following raw materials: Polylactic acid (Ingeo 4043D, NatureWorks LLC): 75kg; Polybutylene terephthalate (Ecoflex F Blend C1200, BASF): 25 kg; Modified nano-silica: 1.5 kg; Silane coupling agent: 0.1 kg pH-sensitive chitosan-encapsulated silver ion microcapsules: 3kg; Diisocyanate: 0.3 kg; Catalyst: 0.01 kg.

[0083] The diisocyanate is hexamethylene diisocyanate (HDI).

[0084] The catalyst is dibutyltin dilaurate.

[0085] The preparation method of modified nano-silica includes the following steps: 5 kg of nano silica (Evonik's AEROSIL 200) was dispersed in 50 L of anhydrous ethanol and ultrasonically dispersed for 30 minutes.

[0086] Continue stirring and reacting for 4 hours.

[0087] The mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried for 12 hours to obtain modified nano-silica.

[0088] The preparation method of pH-sensitive chitosan-encapsulated silver ion microcapsules includes the following steps: Step a: Prepare chitosan solution: Dissolve 1 kg of chitosan (degree of deacetylation ≥ 90%, commercially available) in 100 L of 1% (v / v) acetic acid solution and stir until completely dissolved to obtain a chitosan solution.

[0089] Step b: Prepare silver ion antibacterial agent solution: 0.5 kg of silver ion antibacterial agent (commercially available; in this example, it was purchased from Sanitary in Switzerland, model BCA21-61) was dissolved in 50 L of deionized water to obtain a silver ion antibacterial agent solution.

[0090] Step c: Slowly add the silver ion antibacterial agent solution dropwise to the chitosan solution, stir evenly, and obtain a mixed solution.

[0091] Step d: Microcapsules were prepared using spray drying. The mixed solution was spray-dried using a spray dryer to collect pH-sensitive chitosan-encapsulated silver ion microcapsules.

[0092] Spray drying parameters: inlet air temperature 130℃, outlet air temperature 80℃, spray pressure 0.15MPa.

[0093] This embodiment also provides a method for preparing an anti-mildew and antibacterial decorative film, including the following steps: Step 1: Dry polylactic acid and polybutylene terephthalate under vacuum at 80°C for 12 hours.

[0094] Step 2: Add the dried polylactic acid, polybutylene terephthalate, silane coupling agent, modified nano silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules into a high-speed mixer and mix at 1000 rpm for 10 minutes to obtain the mixture.

[0095] Step 3: The mixture is melt-extruded through a twin-screw extruder; during the extrusion process, diisocyanate (hexamethylene diisocyanate) and catalyst (dibutyltin dilaurate) are added to carry out chemical cross-linking.

[0096] The material is obtained by extrusion.

[0097] The extruder temperatures are set as follows: 160℃ (feed zone), 170℃, 180℃, 185℃, 190℃ (die). The screw speed is set to 150 rpm.

[0098] Step 4: The molten material is processed into an anti-mildew and antibacterial decorative film using a blown film process, including: The molten material is extruded into an annular die, and the film is inflated by compressed air at an inflation ratio of 2:1 and a traction speed of 10m / min to obtain a 50μm thick anti-mildew and antibacterial decorative film.

[0099] Step 5: Cooling: Use air ring cooling to ensure rapid cooling and shaping of the anti-mildew and antibacterial decorative film.

[0100] Test results: 1. Tensile strength: 36MPa.

[0101] 2. Antibacterial properties: 96.5% (24 hours).

[0102] 3. Anti-mildew performance: Level 1.

[0103] 4. Resistance to damp heat: 32.5MPa, 91.0% (24 hours).

[0104] Compared to Example 1, the nano-silica modified using non-specific methods in Comparative Example 1 tends to agglomerate, forming stress concentration points and exhibiting weak interfacial bonding, leading to a decline in mechanical properties. Although the pH-sensitive chitosan-encapsulated silver ion microcapsules are still present, the lack of interfacial regulation means that silver ion release may experience localized bursts or inadequate release due to environmental pH fluctuations, resulting in decreased antibacterial durability. Uneven dispersion of the modified nano-silica leads to a decrease in the local density of the antifungal and antibacterial decorative film, making it easier for mold to attach and grow in weak areas. While the pH-responsive release of silver ion microcapsules from the pH-sensitive chitosan-encapsulated silver ion microcapsules remains partially effective, the overall antifungal effect is weaker than that of Example 1. The modified nano-silica prepared using non-specific methods has high interfacial thermal resistance with the substrate, making it prone to detachment under humid and hot environments, further reducing tensile strength.

[0105] Comparative Example 2 The difference from Example 1 is that the pH-sensitive chitosan-encapsulated silver ion microcapsules were replaced with a silver ion antibacterial agent (commercially available, purchased from Sanitary in Switzerland, model BCA21-61).

[0106] Test results: 1. Tensile strength: 39MPa.

[0107] 2. Antibacterial properties: 98.0% (24 hours).

[0108] 3. Anti-mildew performance: Level 1.

[0109] 4. Resistance to damp heat: 34MPa, 83.0% (24 hours).

[0110] The silane coupling agent-modified nano-silica exhibits uniform dispersion and strong interfacial bonding, resulting in initial mechanical properties close to those of Example 1. However, commercially available silver ion antibacterial agents lack the flexible protection of chitosan, affecting local stress distribution. These agents lack a pH-responsive release mechanism, exhibiting high initial antibacterial efficiency, but their activity diminishes over time due to silver ion oxidation or loss. The lack of pH-sensitive release regulation from chitosan prevents targeted release of silver ions in acidic environments (mold metabolic zones), leading to a weaker antifungal effect compared to Example 1. While nano-modification improves density, it cannot completely compensate for the lack of release regulation; furthermore, the loss of the SiO2-chitosan-matrix interfacial coupling results in poor heat resistance. Consequently, Comparative Example 2 shows a significant difference in overall performance compared to Example 1.

[0111] Comparative Example 3 The difference from Comparative Example 1 is that the pH-sensitive chitosan-encapsulated silver ion microcapsules were replaced with a silver ion antibacterial agent (commercially available, purchased from Sanitary in Switzerland, model BCA21-61).

[0112] Test results: 1. Tensile strength: 32MPa.

[0113] 2. Antibacterial properties: 94.0% (24 hours).

[0114] 3. Anti-mildew performance: Level 2.

[0115] 4. Resistance to damp heat: 26MPa, 73.5% (24 hours).

[0116] Modified nano-silica not prepared according to specific methods exhibits severe agglomeration, weak interfacial bonding, and a significant decrease in mechanical properties. Poor nano-dispersion leads to uneven distribution of silver ions and a lack of pH-responsive release regulation, resulting in weak and easily decaying antibacterial effects. Unmodified nanomaterials result in poor film density, making it easy for mold to adhere and grow over large areas; commercially available silver ion antibacterial agents lack targeted release capabilities, and their anti-mold effect is significantly weaker than that of Example 1. Furthermore, poor interfacial thermal stability with the substrate makes them prone to debonding and degradation under humid and hot environments, leading to a significant decrease in tensile strength.

[0117] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A mildew-proof and antibacterial decorative film, characterized in that, The following raw materials are included in the preparation according to parts by weight: Polylactic acid: 70-80 parts; Polybutylene terephthalate (PET): 20-30 parts; Silane coupling agent modified nano-silica: 1-3 parts; pH-sensitive chitosan-encapsulated silver ion microcapsules: 1-5 parts; Diisocyanate: 0.1-1 part; Catalyst: 0.001-0.02 parts.

2. The anti-mildew and antibacterial decorative film according to claim 1, characterized in that, The preparation method of pH-sensitive chitosan-encapsulated silver ion microcapsules includes the following steps: Chitosan solution was prepared using chitosan and acetic acid. Prepare a silver ion antibacterial agent solution using water and silver ion antibacterial agent; Add the silver ion antibacterial agent solution dropwise to the chitosan solution and stir until homogeneous to obtain a mixed solution; pH-sensitive chitosan-encapsulated silver ion microcapsules were prepared by spray drying of the mixed solution; The weight ratio of silver ion antibacterial agent to chitosan is 1:(1-5).

3. The anti-mildew and antibacterial decorative film according to claim 1, characterized in that, The preparation method of silane coupling agent modified nano-silica includes the following steps: dispersing nano-silica in an alcohol solvent, stirring and reacting for 2-6 hours, and then filtering, washing and drying to obtain silane coupling agent modified nano-silica.

4. The anti-mildew and antibacterial decorative film according to claim 2, characterized in that, Prepare a 0.5-5% (w / v) chitosan solution using chitosan and acetic acid; The ratio of silver ion antibacterial agent to water is 1g: (90-110)mL.

5. The anti-mildew and antibacterial decorative film according to claim 2, characterized in that, The preparation of chitosan solution includes: dissolving chitosan in 0.1-2% (v / v) acetic acid solution and stirring until completely dissolved to obtain chitosan solution.

6. The anti-mildew and antibacterial decorative film according to claim 3, characterized in that, The ratio of nano-silica to alcohol solvent is 1g: (8-12)mL; The weight ratio of nano-silica to silane coupling agent is 1:(0.01-0.1).

7. The anti-mildew and antibacterial decorative film according to claim 1, characterized in that, Diisocyanates include one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate; The catalyst includes one or a mixture of two or more of the following: organotin catalysts, titanium-based catalysts, and organobismuth catalysts.

8. A method for preparing an anti-mildew and antibacterial decorative film according to any one of claims 1-7, characterized in that, Includes the following steps: A mixture of polylactic acid, polybutylene terephthalate, silane coupling agent-modified nano-silica, and pH-sensitive chitosan-encapsulated silver ion microcapsules was prepared to obtain a mixture. The mixture of raw materials, diisocyanate, and catalyst is melt-extruded to obtain a molten material; Molten materials are processed into anti-mildew and antibacterial decorative films using casting or blown film processes.

9. The method for preparing the anti-mildew and antibacterial decorative film according to claim 8, characterized in that, The thickness is 45-55μm.

10. The method for preparing the anti-mildew and antibacterial decorative film according to claim 8, characterized in that, The casting film process includes: extruding molten material onto a cooling roller, with the temperature of the cooling roller controlled at 25±5℃ and the traction speed at 4-6m / min; The blown film process includes: extruding molten material into an annular die, inflating the film with compressed air, with an inflation ratio of (2-3):1 and a traction speed of 8-12 m / min.