Production method of polyvinyl alcohol film

Abstract

The invention discloses a production method of a polyvinyl alcohol film, and relates to the technical field of polymer functional films. Three specific self-prepared functional components are compounded with a polyvinyl alcohol matrix, sol-gel, film casting and heat treatment are carried out, the multifunctional polyvinyl alcohol composite film with long-acting antibacterial property, high mechanical toughness, excellent hydrophobicity, efficient ultraviolet shielding and good weather resistance is prepared, and all the components generate a remarkable synergistic effect, so that the composite film has a good antibacterial property and good weather resistance. The problem of performance imbalance caused by single modification is solved.

Description

Technical Field

[0001] This invention relates to the field of polymer functional film technology, specifically a method for producing polyvinyl alcohol film. Background Technology

[0002] Polyvinyl alcohol (PVA) films have broad application prospects in food packaging, pharmaceutical carriers, and optical devices due to their excellent gas barrier properties, biocompatibility, biodegradability, and high transparency. However, the inherent characteristics of pure PVA films, such as strong hydrophilicity, poor moisture resistance, insufficient mechanical toughness (especially high brittleness in the dry state), and lack of functionality (such as antibacterial and UV shielding), limit their application in high-end and harsh environments.

[0003] To improve the performance of PVA films, existing technologies typically employ physical blending or chemical modification to introduce various additives. For example, inorganic nanoparticles (such as SiO2, TiO2, and cellulose nanocrystals) are added to enhance mechanical strength, thermal stability, or impart UV shielding; antibacterial agents (such as silver particles, quaternary ammonium salts, and chitosan) are blended to introduce antibacterial properties; or crosslinking agents are used to improve water resistance. However, these methods often face the following common challenges: First, the introduction of single-functional fillers can easily lead to performance imbalances; for example, increased rigidity is often accompanied by a decrease in toughness, and the addition of functional fillers may impair optical transparency or processing flowability. Second, most fillers have poor interfacial compatibility with the PVA matrix, easily leading to agglomeration, which not only affects performance uniformity but may also become stress concentration points, accelerating material failure. Third, physically blended functional components are prone to migration and dissolution, resulting in insufficient functional durability and potentially posing safety hazards. Furthermore, achieving multiple objectives such as high strength, high toughness, long-lasting antibacterial properties, stable UV shielding, and good moisture resistance in a single system, while maintaining the transparency and processability of the film, remains a technological challenge. Although some studies have attempted to construct core-shell structures or modify surfaces to improve filler compatibility, a systematic solution that can simultaneously regulate the interfacial interactions of multiple components and achieve functional synergy and long-term stability is still lacking.

[0004] Therefore, developing a PVA composite film preparation technology that can achieve uniform filler dispersion, strong interfacial bonding, multifunctional synergy, and long-term stability has become a key issue that urgently needs to be addressed in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing polyvinyl alcohol film to solve the problems mentioned in the background art.

[0006] This invention provides a method for producing a polyvinyl alcohol film, wherein the polyvinyl alcohol film comprises the following raw materials in parts by weight: 90-110 parts of polyvinyl alcohol; 800-1200 parts of deionized water; 5-15 parts of mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent; 5-20 parts of oxidized nanocellulose / dopamine modified chitosan dynamic hydrogel toughening particles; 3-10 parts of titanium dioxide nanotubes loaded with zinc stearate / polydopamine hydrophobic UV shielding agent; 0.5-2 parts of wetting and dispersing agent; 0.1-0.5 parts of defoamer; Leveling agent 0.2-1 part; Crosslinking accelerator 1-5 parts.

[0007] As a preferred embodiment of the present invention, the preparation method of the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent is as follows: A1. Tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were added to a mixture of ethanol and water, and ammonia was added dropwise. The mixture was stirred at room temperature for 24 hours, centrifuged, washed and dried to obtain aminated mesoporous silica nanospheres. The volume ratio of ethanol to water in the ethanol-water mixture is 4:1. The concentration of the ammonia water is 25-28%; The mass ratio of tetraethyl orthosilicate, hexadecyltrimethylammonium bromide, ethanol, water, and ammonia is 20:4:400:100:10. A2. The aminated mesoporous silica nanospheres obtained in step A1, polyhexamethylene guanidine aqueous solution, and glutaraldehyde were added to a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a pH of 8.5. The mixture was stirred at 50°C for 12 h, centrifuged, washed, and dried to obtain polyhexamethylene guanidine functionalized mesoporous silica microspheres. The mass ratio of the aminated mesoporous silica nanospheres, polyhexamethylene guanidine, glutaraldehyde, and tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 10:5:2:200. A3. Disperse the polyhexamethylene guanidine functionalized mesoporous silica microspheres obtained in A2 in an aqueous sodium alginate solution, add them dropwise to an aqueous calcium chloride solution while stirring, continue stirring for 1 hour, filter, wash and freeze dry to obtain a mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent. The mass ratio of the polyhexamethylene guanidine functionalized mesoporous silica microspheres, sodium alginate, and calcium chloride is 10:(1-3):(1-5). The concentration of the sodium alginate aqueous solution is 1-3%; The concentration of the calcium chloride aqueous solution is 1-5%.

[0008] It should be noted that the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent prepared in this invention has a core-shell structure with aminated mesoporous silica as the core, polyhexamethylene guanidine as the antibacterial agent, and calcium alginate as the encapsulating layer. Its preparation involves covalently anchoring polyhexamethylene guanidine to the mesoporous channels and surface via glutaraldehyde crosslinking, followed by ionic crosslinking of sodium alginate with calcium ions to form a coating layer on its exterior. This structure itself endows it with sustained-release properties of the antibacterial component, and the calcium alginate shell forms a dry gel layer with a network structure after drying. In polyvinyl alcohol films, its mechanism of action is dual: firstly, the hydrogen bonding between the calcium alginate shell and the hydroxyl groups of polyvinyl alcohol acts as a physical crosslinking point, enhancing the modulus of the film; secondly, the gradual swelling or degradation of the shell in a humid environment controls the combination of contact release and diffusion release of polyhexamethylene guanidine, providing continuous antibacterial properties that are not easily degraded by leaching.

[0009] As a preferred embodiment of the present invention, the preparation method of the oxidized nanocellulose / dopamine modified chitosan dynamic hydrogel toughening particles is as follows: B1. Microcrystalline cellulose, 2,2,6,6-tetramethylpiperidine-1-oxygen radical, and sodium hypochlorite were added to a sodium carbonate-sodium bicarbonate buffer solution with a pH of 10.5. The mixture was stirred at room temperature for 48 hours. After the reaction was completed, the pH was adjusted to neutral. The mixture was then dispersed by ultrasonication and purified by centrifugation to obtain an oxidized nanocellulose whisker dispersion. The mass ratio of the microcrystalline cellulose, 2,2,6,6-tetramethylpiperidine-1-oxygen radical, sodium hypochlorite, and sodium carbonate-sodium bicarbonate buffer solution is 10:0.1:20:500. B2. Chitosan was dissolved in dilute acetic acid solution, and dopamine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was stirred and reacted at room temperature and under nitrogen protection for 24 hours. After the reaction was completed, the mixture was dialyzed and freeze-dried to obtain dopamine-modified chitosan. The mass ratio of chitosan, dopamine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide is 10:5:6:3. B3. Dissolve the oxidized cellulose nanofiber whisker dispersion obtained in step B1 and the dopamine-modified chitosan obtained in step B2 in tris(hydroxymethyl)aminomethane hydrochloride buffer solution, mix evenly, and stir and react for 6 hours at pH 7.5 and 40℃ to obtain a precursor solution; spray dry the precursor solution to obtain oxidized cellulose nanofiber / dopamine-modified chitosan dynamic hydrogel toughened particles. The mass ratio of the oxidized nanocellulose whiskers, dopamine-modified chitosan, and tris(hydroxymethyl)aminomethane hydrochloride buffer is 5:10:300.

[0010] It should be noted that the oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles prepared in this invention are hydrogels constructed by the Schiff base reaction between the aldehyde groups on the surface of oxidized nanocellulose and the amino groups on the dopamine-modified chitosan chains, forming a dynamic covalent cross-linked network, and then spray-dried. The Schiff base bonds are reversible under mild conditions. The particle itself is a hydrophilic network rich in dynamic bonds and numerous hydroxyl groups. In polyvinyl alcohol films, its main mechanism of action is not the crack pinning of traditional rigid particles, but rather its role as an energy dissipation center: when the film is subjected to stress, the dynamic covalent bonds inside the particles can undergo reversible breakage and recombination, effectively absorbing and dispersing stress; simultaneously, the abundant functional groups on its surface form strong hydrogen bonds with the polyvinyl alcohol matrix, ensuring effective stress transfer. This toughening mechanism based on dynamic covalent bonds provides a different approach to improving the toughness of films while maintaining high transparency requirements.

[0011] As a preferred embodiment of the present invention, the preparation method of the titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent is as follows: C1. Add nano-titanium dioxide powder and sodium hydroxide to deionized water, place in a reaction vessel, and react at 130℃ for 48h. The reaction product is washed with hydrochloric acid and deionized water until neutral, and then dried to obtain titanium dioxide nanotubes. The mass ratio of the nano-titanium dioxide powder, sodium hydroxide, and deionized water is 5:40:200. C2. Add the titanium dioxide nanotubes obtained in step C1 to anhydrous ethanol containing zinc stearate, and impregnate them at 60°C and under vacuum for 4 hours. Then remove the ethanol by rotary evaporation and dry them to obtain zinc stearate-loaded titanium dioxide nanotubes. The mass ratio of the titanium dioxide nanotubes, zinc stearate and anhydrous ethanol is 10:8:(206-312); C3. Disperse 10g of zinc stearate-loaded titanium dioxide nanotubes obtained in step C2 in 200g of tris(hydroxymethyl)aminomethane hydrochloride buffer, add 2g of dopamine hydrochloride, stir and polymerize at room temperature for 24h, and centrifuge, wash and dry the reaction product to obtain titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent. The mass ratio of the zinc stearate-supported titanium dioxide nanotubes, dopamine hydrochloride, and tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 10:2:200.

[0012] It should be noted that the titanium dioxide nanotubes prepared in this invention, loaded with zinc stearate / polydopamine hydrophobic UV shielding agent, construct a three-layer composite structure: zinc stearate is loaded onto the nanotube cavity and surface through solution impregnation and crystallization, and the outermost layer is coated with a polydopamine coating. The preparation process involves, sequentially, the impregnation and filling of zinc stearate in a solution (in anhydrous ethanol at 60°C) within the nanotubes followed by crystallization, and the oxidative self-polymerization of dopamine under weakly alkaline conditions to form a film. This structure integrates the functions of each component: the titanium dioxide nanotubes provide UV scattering and absorption; zinc stearate, as a phase change material, can store and release heat through solid-liquid phase transition and reduce surface energy; the polydopamine coating further enhances UV absorption and improves adhesion to the substrate. In polyvinyl alcohol (PVA) films, the mechanism of action is synergistic: titanium dioxide and polydopamine jointly construct a broad-spectrum UV shielding barrier; zinc stearate on the surface, together with polydopamine, imparts hydrophobicity to the particle surface, and when distributed in a hydrophilic film matrix, it can block water vapor permeation to a certain extent; simultaneously, the phase transition behavior of zinc stearate can buffer local temperature rise. This method of integrating UV shielding, hydrophobic modification, and thermal management functions into a single modifier simplifies the functional formulation design of films.

[0013] As a preferred embodiment of the present invention, the wetting and dispersing agent is a hydrophilic modified ammonium polyacrylate.

[0014] As a preferred embodiment of the present invention, the defoamer is a mineral oil-based defoaming polymer.

[0015] As a preferred embodiment of the present invention, the leveling agent is a polyether-modified polysiloxane.

[0016] As a preferred embodiment of the present invention, the crosslinking accelerator is citric acid.

[0017] A method for preparing a polyvinyl alcohol film specifically includes the following steps: S1. Add polyvinyl alcohol to deionized water and stir at 90-95℃ until dissolved to obtain a polyvinyl alcohol matrix solution. Cool the solution to 70℃ and keep it warm for later use. S2. To the polyvinyl alcohol matrix solution obtained in step S1, add in sequence the following: mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent, oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles, titanium dioxide nanotube-supported zinc stearate / polydopamine hydrophobic UV shielding agent, and hydrophilic modified ammonium polyacrylate wetting and dispersing agent; shear and disperse the above mixture at 65-75℃ and a rotation speed of 1500-2500 r / min for 20-40 min; add mineral oil-based defoaming polymer defoamer, polyether-modified polysiloxane leveling agent, and citric acid crosslinking accelerator, and continue stirring at 60℃ for 2-3 h to obtain the composite film solution; S3. The composite film liquid obtained in step S2 is cast onto a clean polyethylene terephthalate substrate and placed in an oven at 50°C for initial drying for 2 hours until the surface is set. Then, the temperature is raised to 90-95°C and heat-treated for another 1-2 hours. After the heat treatment is completed, the film is allowed to cool naturally to room temperature and peeled off from the substrate to obtain the polyvinyl alcohol film.

[0018] It should be noted that when the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent exists alone in the polyvinyl alcohol composite film, its rigid core-shell structure mainly serves as a physical crosslinking point, which can improve the modulus and thermal stability of the film to a certain extent, and provide antibacterial properties through contact and slow release mechanisms; however, its rigid particles may also serve as stress concentration points, inducing microcracks when the film is subjected to large deformation, which has a negative impact on the elongation at break of the film.

[0019] When oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles exist alone in polyvinyl alcohol composite films, their three-dimensional network rich in dynamic bonds can efficiently dissipate energy through reversible bond breaking and recombination, significantly improving the toughness, elongation at break and impact resistance of the film; however, the mechanical strength of the particles themselves is limited, and their contribution to improving the initial modulus, hardness and heat resistance of the film is relatively weak.

[0020] When titanium dioxide nanotubes loaded with zinc stearate / polydopamine hydrophobic UV shielding agent exist alone in polyvinyl alcohol composite films, they mainly provide effective UV shielding and impart certain moisture resistance to the film through surface hydrophobic components. However, the high aspect ratio and surface hydrophobicity of the nanotubes may lead to uneven dispersion in the hydrophilic polyvinyl alcohol matrix, making them prone to aggregation, which negatively affects the transparency and mechanical uniformity of the film.

[0021] When mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent and oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles work together, the soft network of dynamic hydrogel particles can wrap around or bridge the rigid antibacterial particles, effectively alleviating stress concentration. More importantly, the amino and other functional groups on the surface of the hydrogel particles may generate strong electrostatic interactions or hydrogen bonds with the carboxyl groups of the outer layer of calcium alginate of the antibacterial agent. This interfacial coupling not only enhances the binding force between the filler and the matrix, and between fillers, but may also synergistically regulate the release kinetics of the antibacterial components by constructing additional diffusion barriers and affinity sites, thereby achieving better toughness and improved antibacterial durability.

[0022] When mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent and titanium dioxide nanotubes-supported zinc stearate / polydopamine hydrophobic UV shielding agent work together, the polydopamine and calcium alginate on the outer layers of both are rich in polar groups, improving the compatibility and dispersibility of the hydrophobic UV shielding agent in the matrix. In this composite system, titanium dioxide nanotubes may exhibit photocatalytic activity under UV irradiation, and the interfacial reactions they induce (such as the generation of reactive oxygen species) may promote a more stable bond at the interface between the calcium alginate shell and the polyvinyl alcohol matrix. At the same time, the presence of polyhexamethylene guanidine may quench some of the reactive oxygen species generated by titanium dioxide to a certain extent, thereby potentially reducing photo-oxidative damage to the matrix. This mutual protective effect is not present when used alone.

[0023] When oxidized cellulose nanoparticles / dopamine-modified chitosan dynamic hydrogel toughening particles and titanium dioxide nanotubes loaded with zinc stearate / polydopamine hydrophobic UV shielding agents work together, the dynamic network structure of the toughening particles provides a soft interface layer and steric hindrance for the rigid and easily aggregated nanotubes, promoting their nanoscale dispersion in the matrix. On the other hand, the catechol structure of polydopamine on the UV shielding agent surface and the amino and imine bonds on the chitosan chains in the toughening particles may form multiple reversible interactions, constructing a through-and-through, dynamic secondary cross-linked network. This network structure not only helps to enhance the toughness recovery ability of the film, but may also, through its dynamic adaptive properties, better maintain the dispersion state and surface properties of the functional filler during film deformation, achieving simultaneous improvement in functional durability and mechanical durability.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention, through the structural design of three self-prepared components, effectively overcomes the limitations of improving the performance of single-functional fillers in polyvinyl alcohol (PVA) films. The components generate a synergistic effect beyond simple addition through specific interfacial interactions. The PVA film system prepared by this invention introduces a dynamic reversible network based on dynamic covalent bonds and multiple physical interactions, endowing the material with certain intelligent response and adaptive characteristics. This not only effectively dissipates stress and improves damage tolerance but also helps maintain the dispersion and interfacial bonding of the functional filler after environmental stress or deformation, thereby enabling the film to achieve better functional durability and mechanical durability, broadening its potential application prospects in flexible packaging, biomedicine, and other fields. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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] Preparation Example 1 The preparation method of the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent is as follows: A1. Add 20g of tetraethyl orthosilicate and 4g of hexadecyltrimethylammonium bromide to a mixture of 400g of ethanol and 100g of water, add 10g of 25% ammonia water dropwise, stir and react at room temperature for 24h, centrifuge, wash and dry to obtain aminated mesoporous silica nanospheres. A2. Add 10g of the aminated mesoporous silica nanospheres obtained in step A1, 5g of polyhexamethylene guanidine aqueous solution, and 2g of glutaraldehyde to 200g of tris(hydroxymethyl)aminomethane hydrochloride buffer solution with pH 8.5. Stir the reaction at 50°C for 12h, centrifuge, wash and dry to obtain polyhexamethylene guanidine functionalized mesoporous silica microspheres. A3. Disperse 10g of polyhexamethylene guanidine functionalized mesoporous silica microspheres obtained in A2 in 100g of sodium alginate aqueous solution with a concentration of 2%, and add it dropwise to 250g of calcium chloride aqueous solution with a concentration of 2% while stirring. Continue stirring for 1 hour, filter, wash and freeze dry to obtain mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent. Preparation Example 2 The preparation method of oxidized cellulose nanoparticles / dopamine-modified chitosan dynamic hydrogel toughening particles is as follows: B1. Add 10g microcrystalline cellulose, 0.1g 2,2,6,6-tetramethylpiperidine-1-oxy radical, and 20g sodium hypochlorite to 500g sodium carbonate-sodium bicarbonate buffer solution with pH 10.5. Stir and react at room temperature for 48h. After the reaction is completed, adjust the pH to neutral. After ultrasonic dispersion and centrifugation purification, oxidized nanocellulose whisker dispersion is obtained. The total molar concentration of the sodium carbonate-sodium bicarbonate buffer solution is 0.1 mol / L, wherein the molar ratio of sodium carbonate to sodium bicarbonate is 1:4. B2. Dissolve 10g of chitosan in dilute acetic acid solution, add 5g of dopamine hydrochloride, 6g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 3g of N-hydroxysuccinimide, stir and react for 24h at room temperature and under nitrogen protection, dialyze and freeze dry after the reaction to obtain dopamine modified chitosan. B3. Dissolve 5g of the oxidized cellulose nanofiber whisker dispersion obtained in step B1 and 10g of the dopamine-modified chitosan obtained in step B2 in 300g of tris(hydroxymethyl)aminomethane hydrochloride buffer solution, mix evenly, and stir and react for 6h at pH 7.5 and 40℃ to obtain a precursor solution; spray dry the precursor solution to obtain oxidized cellulose nanofiber / dopamine-modified chitosan dynamic hydrogel toughened particles; The concentration of the trihydroxymethylaminomethane hydrochloride buffer solution is 0.1 mol / L.

[0027] Preparation Example 3 The preparation method of titanium dioxide nanotubes loaded with zinc stearate / polydopamine hydrophobic UV shielding agent is as follows: C1. Add 5g of nano titanium dioxide powder and 40g of sodium hydroxide to 200g of deionized water, place them in a reaction vessel, and react at 130℃ for 48h. The reaction product is washed with hydrochloric acid and deionized water until neutral, and then dried to obtain titanium dioxide nanotubes. C2. Add 10g of titanium dioxide nanotubes obtained in step C1 to 260g of anhydrous ethanol containing 8g of zinc stearate, and impregnate them at 60℃ and under vacuum for 4h. Then remove the ethanol by rotary evaporation and dry to obtain zinc stearate-loaded titanium dioxide nanotubes. C3. Disperse 10g of zinc stearate-loaded titanium dioxide nanotubes obtained in step C2 in 200g of tris(hydroxymethyl)aminomethane hydrochloride buffer, add 2g of dopamine hydrochloride, stir and polymerize at room temperature for 24h, and centrifuge, wash and dry the reaction product to obtain titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent.

[0028] Example 1

[0029] A method for preparing a polyvinyl alcohol film specifically includes the following steps: S1. By weight, add 100 parts of polyvinyl alcohol to 1000 parts of deionized water and stir at 95°C until completely dissolved to obtain a polyvinyl alcohol matrix solution. Cool down to 70°C and keep warm for later use. S2. To the polyvinyl alcohol matrix solution obtained in step S1, add 10 parts of mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent, 12.5 parts of oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles, 6.5 parts of titanium dioxide nanotube-supported zinc stearate / polydopamine hydrophobic UV shielding agent, and 1.3 parts of hydrophilic modified ammonium polyacrylate wetting and dispersing agent; shear and disperse the above mixture at 70°C and 2000 r / min for 30 min; add 0.3 parts of mineral oil-based defoaming polymer defoamer, 0.6 parts of polyether-modified polysiloxane leveling agent, and 3 parts of citric acid crosslinking accelerator, and continue stirring at 60°C for 2 h to obtain a uniform, stable, bubble-free composite film solution; S3. The composite film liquid obtained in step S2 is cast onto a clean polyethylene terephthalate substrate and placed in an oven at 50°C for initial drying for 2 hours until the surface is set. Then, the temperature is raised to 90°C and heat-treated for another 1.5 hours. After the heat treatment is completed, the film is allowed to cool naturally to room temperature and peeled off from the substrate to obtain the polyvinyl alcohol film.

[0030] In this embodiment, some of the raw materials used are the same as those obtained in Preparation Examples 1-3, and the other examples are the same.

[0031] Example 2

[0032] S1. By weight, add 90 parts of polyvinyl alcohol to 800 parts of deionized water and stir at 95°C until completely dissolved to obtain a polyvinyl alcohol matrix solution. Cool the solution to 70°C and keep it warm for later use. S2. To the polyvinyl alcohol matrix solution obtained in step S1, add 5 parts of mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent, 5 parts of oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles, 3 parts of titanium dioxide nanotube-supported zinc stearate / polydopamine hydrophobic UV shielding agent, and 0.5 parts of hydrophilic modified ammonium polyacrylate wetting and dispersing agent; shear and disperse the above mixture at 70°C and 2000 r / min for 30 min; add 0.1 parts of mineral oil-based defoaming polymer defoamer, 0.2 parts of polyether-modified polysiloxane leveling agent, and 1 part of citric acid crosslinking accelerator, and continue stirring at 60°C for 2 h to obtain a uniform, stable, bubble-free composite film solution; S3. The composite film liquid obtained in step S2 is cast onto a clean polyethylene terephthalate substrate and placed in an oven at 50°C for initial drying for 2 hours until the surface is set. Then, the temperature is raised to 90°C and heat-treated for another 1.5 hours. After the heat treatment is completed, the film is allowed to cool naturally to room temperature and peeled off from the substrate to obtain the polyvinyl alcohol film.

[0033] Example 3

[0034] S1. By weight, add 110 parts of polyvinyl alcohol to 1200 parts of deionized water and stir at 95°C until completely dissolved to obtain a polyvinyl alcohol matrix solution. Cool down to 70°C and keep warm for later use. S2. To the polyvinyl alcohol matrix solution obtained in step S1, add 15 parts of mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent, 20 parts of oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles, 10 parts of titanium dioxide nanotube-supported zinc stearate / polydopamine hydrophobic UV shielding agent, and 2 parts of hydrophilic modified ammonium polyacrylate wetting and dispersing agent; shear and disperse the above mixture at 70°C and 2000 r / min for 30 min; add 0.5 parts of mineral oil-based defoaming polymer defoamer, 1 part of polyether-modified polysiloxane leveling agent, and 5 parts of citric acid crosslinking accelerator, and continue stirring at 60°C for 2 h to obtain a uniform, stable, bubble-free composite film solution; S3. The composite film liquid obtained in step S2 is cast onto a clean polyethylene terephthalate substrate and placed in an oven at 50°C for initial drying for 2 hours until the surface is set. Then, the temperature is raised to 90°C and heat-treated for another 1.5 hours. After the heat treatment is completed, the film is allowed to cool naturally to room temperature and peeled off from the substrate to obtain the polyvinyl alcohol film.

[0035] Comparative Example 1 The difference between this comparative example and Example 1 is that the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent prepared in Example 1 was not added. Instead, an equal weight of composite powder 1, obtained by simple physical mixing and drying of polyhexamethylene guanidine and aminated mesoporous silica nanospheres, was added. This was only a physical blending, and the polyhexamethylene guanidine was only physically adsorbed onto the silica surface and did not have a calcium alginate shell.

[0036] Comparative Example 2 The difference between this comparative example and Example 1 is that the oxidized nanocellulose / dopamine modified chitosan dynamic hydrogel toughening particles prepared in Example 2 were not added. Instead, an equal weight of composite powder 2, which is obtained by simple physical mixing and spray drying of oxidized nanocellulose whiskers and chitosan, was added, which is only a physical blending.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that the titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent prepared in Example 3 was not added. Instead, an equal weight of composite powder 3 obtained by simple physical mixing and grinding of nano-titanium dioxide and zinc stearate was added, which was only a physical blending.

[0038] test: I. Long-lasting antibacterial performance test The film application method in GB / T 31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials" was adopted and modified to evaluate the long-term effectiveness.

[0039] Test strain: Staphylococcus aureus (ATCC 6538).

[0040] Test method: Place the film sample (5cm×5cm) in a sterile Petri dish, and add 0.1mL of bacterial suspension (concentration approximately 1×10⁻⁶) to the sample surface. 5 The bacterial solution (CFU / mL) was covered with a sterile polyethylene film to ensure uniform contact between the bacterial solution and the sample surface. After 7 and 14 days of contact, the bacterial solution was eluted with neutralization solution and cultured for counting to calculate the antibacterial rate. A blank control group (sterile polyethylene film) was also included.

[0041] The test results are shown in Table 1.

[0042] II. Mechanical Property Testing The test was conducted according to GB / T 1040.3-2006, "Determination of tensile properties of plastics".

[0043] Testing equipment: Universal testing machine.

[0044] Sample specifications: Cut into dumbbell-shaped standard strips (approximately 0.1 mm thick).

[0045] Test conditions: tensile speed 50 mm / min, room temperature (23±2℃). Each test group had at least 5 parallel samples. The test indicators were tensile strength (MPa) and elongation at break (%).

[0046] The test results are shown in Table 1.

[0047] III. Surface hydrophobicity and water vapor permeability test Water contact angle test: The sitting drop method was used, and the contact angle measuring instrument was used to measure 5 times at different positions on the film surface and the average value was taken.

[0048] Water vapor transmission rate test: The test was conducted according to GB / T 26253-2010 Determination of water vapor transmission rate of plastic films and sheets by infrared detector, under the conditions of 38℃ and 90%RH.

[0049] The test results are shown in Table 1.

[0050] IV. Ultraviolet Shielding Performance Test UV-Vis transmittance spectrum: Using a UV-Vis spectrophotometer, the transmittance of the film in the wavelength range of 200-800 nm was measured, and the average transmittance in the long-wave ultraviolet (UVA) band (315-400 nm) and medium-wave ultraviolet (UVB) band (280-315 nm) and the average transmittance in the visible light region (400-800 nm) were calculated.

[0051] The test results are shown in Table 2.

[0052] V. Weather Resistance (UV Aging) Test The film was subjected to accelerated ultraviolet aging using GB / T 16422.3-2022 Plastics Laboratory Light Source Exposure Test Method Part 3: Fluorescent Ultraviolet Lamp.

[0053] Conditions: UVA-340 lamp tube, irradiation at 60℃ for 8 hours, followed by condensation at 50℃ for 4 hours as one cycle.

[0054] Evaluation: After aging for 0, 72, and 144 hours respectively, the tensile strength retention rate and elongation at break retention rate of the film were tested.

[0055] The test results are shown in Table 2.

[0056] VI. Summary of Results Table 1

[0057] Table 2

[0058] VII. Discussion of Results As shown in Table 1, the polyvinyl alcohol composite films prepared in Examples 1-3 of the present invention have excellent long-lasting antibacterial properties, high mechanical strength and toughness, good hydrophobicity, high efficiency in UV shielding and excellent UV aging stability.

[0059] Compared to Examples 1-3, Comparative Example 1 showed acceptable initial antibacterial properties, but its long-lasting antibacterial performance significantly decreased, with an antibacterial rate of less than 50% after 14 days, and extremely low performance retention after immersion in water. Although its elongation at break was high, its hydrophobicity and UV aging resistance were both poor. This indicates that simple physical mixing cannot achieve a sustained and controlled release of antibacterial components.

[0060] Compared to Examples 1-3, the mechanical properties of the film in Comparative Example 2 were significantly deteriorated, with both tensile strength and elongation at break being significantly lower than those in the examples. Furthermore, it exhibited poor hydrophobicity and low strength retention after UV aging. This indicates that the dynamic network prepared in Example 2 is crucial for dissipating stress and improving toughness, and that its interfacial interactions with other components significantly contribute to maintaining the overall structural stability and durability of the film.

[0061] Compared to Examples 1-3, Comparative Example 3 exhibits severely insufficient UV shielding performance, with a significant increase in UVA / UVB transmittance, leading to a sharp decline in UV aging resistance. Furthermore, its hydrophobicity and water vapor barrier properties are weaker than those of the Examples. This demonstrates that the unique three-layer composite structure of Preparation Example 3 is the core of achieving efficient and durable UV shielding and hydrophobic functions, and the interfacial enhancement provided by its polydopamine coating is crucial for ensuring functional durability.

[0062] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the scope defined by the invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A method for producing a polyvinyl alcohol film, characterized in that: The polyvinyl alcohol film comprises the following raw materials by weight: 90-110 parts of polyvinyl alcohol; 800-1200 parts of deionized water; 5-15 parts of mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent; 5-20 parts of oxidized nanocellulose / dopamine modified chitosan dynamic hydrogel toughening particles; 3-10 parts of titanium dioxide nanotubes loaded with zinc stearate / polydopamine hydrophobic UV shielding agent; 0.5-2 parts of wetting and dispersing agent; 0.1-0.5 parts of defoamer; Leveling agent 0.2-1 part; Crosslinking accelerator 1-5 parts.

2. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: Specifically, the following steps are included: S1. Add polyvinyl alcohol to deionized water and stir at 90-95℃ until dissolved to obtain a polyvinyl alcohol matrix solution. Cool the solution to 70℃ and keep it warm for later use. S2. To the polyvinyl alcohol matrix solution obtained in step S1, add in sequence the following: mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent, oxidized nanocellulose / dopamine-modified chitosan dynamic hydrogel toughening particles, titanium dioxide nanotube-supported zinc stearate / polydopamine hydrophobic UV shielding agent, and wetting and dispersing agent; shear and disperse the above mixture at 65-75℃ and a rotation speed of 1500-2500 r / min for 20-40 min; add defoamer, leveling agent, and crosslinking promoter, and continue stirring at 60℃ for 2-3 h to obtain the composite film solution; S3. The composite film liquid obtained in step S2 is cast onto a clean polyethylene terephthalate substrate and placed in an oven at 50°C for initial drying for 2 hours until the surface is set. Then, the temperature is raised to 90-95°C and heat-treated for another 1-2 hours. After the heat treatment is completed, the film is allowed to cool naturally to room temperature and peeled off from the substrate to obtain the polyvinyl alcohol film.

3. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The preparation method of the mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent is as follows: A1. Tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were added to a mixture of ethanol and water, and ammonia was added dropwise. The mixture was stirred at room temperature for 24 hours, centrifuged, washed and dried to obtain aminated mesoporous silica nanospheres. The volume ratio of ethanol to water in the ethanol-water mixture is 4:

1. The concentration of the ammonia water is 25-28%; The mass ratio of tetraethyl orthosilicate, hexadecyltrimethylammonium bromide, ethanol, water, and ammonia is 20:4:400:100:

10. A2. The aminated mesoporous silica nanospheres obtained in step A1, polyhexamethylene guanidine aqueous solution, and glutaraldehyde were added to a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a pH of 8.

5. The mixture was stirred at 50°C for 12 h, centrifuged, washed, and dried to obtain polyhexamethylene guanidine functionalized mesoporous silica microspheres. The mass ratio of the aminated mesoporous silica nanospheres, polyhexamethylene guanidine, glutaraldehyde, and tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 10:5:2:

200. A3. Disperse the polyhexamethylene guanidine functionalized mesoporous silica microspheres obtained in A2 in an aqueous sodium alginate solution, add them dropwise to an aqueous calcium chloride solution while stirring, continue stirring for 1 hour, filter, wash and freeze dry to obtain a mesoporous silica-supported polyhexamethylene guanidine / calcium alginate core-shell antibacterial agent. The mass ratio of the polyhexamethylene guanidine functionalized mesoporous silica microspheres, sodium alginate, and calcium chloride is 10:(1-3):(1-5).

4. The method for producing a polyvinyl alcohol film according to claim 3, characterized in that: In step A3, the concentration of the sodium alginate aqueous solution is 1-3%; the concentration of the calcium chloride aqueous solution is 1-5%.

5. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The preparation method of the oxidized cellulose nanoparticles / dopamine-modified chitosan dynamic hydrogel toughening particles is as follows: B1. Microcrystalline cellulose, 2,2,6,6-tetramethylpiperidine-1-oxygen radical, and sodium hypochlorite were added to a sodium carbonate-sodium bicarbonate buffer solution with a pH of 10.

5. The mixture was stirred at room temperature for 48 hours. After the reaction was completed, the pH was adjusted to neutral. The mixture was then dispersed by ultrasonication and purified by centrifugation to obtain an oxidized nanocellulose whisker dispersion. The mass ratio of the microcrystalline cellulose, 2,2,6,6-tetramethylpiperidine-1-oxygen radical, sodium hypochlorite, and sodium carbonate-sodium bicarbonate buffer solution is 10:0.1:20:

500. B2. Chitosan was dissolved in dilute acetic acid solution, and dopamine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was stirred and reacted at room temperature and under nitrogen protection for 24 hours. After the reaction was completed, the mixture was dialyzed and freeze-dried to obtain dopamine-modified chitosan. The mass ratio of chitosan, dopamine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide is 10:5:6:

3. B3. Dissolve the oxidized cellulose nanofiber whisker dispersion obtained in step B1 and the dopamine-modified chitosan obtained in step B2 in tris(hydroxymethyl)aminomethane hydrochloride buffer solution, mix evenly, and stir and react for 6 hours at pH 7.5 and 40℃ to obtain a precursor solution; spray dry the precursor solution to obtain oxidized cellulose nanofiber / dopamine-modified chitosan dynamic hydrogel toughened particles. The mass ratio of the oxidized nanocellulose whiskers, dopamine-modified chitosan, and tris(hydroxymethyl)aminomethane hydrochloride buffer is 5:10:

300.

6. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The preparation method of the titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent is as follows: C1. Add nano-titanium dioxide powder and sodium hydroxide to deionized water, place in a reaction vessel, and react at 130℃ for 48h. The reaction product is washed with hydrochloric acid and deionized water until neutral, and then dried to obtain titanium dioxide nanotubes. The mass ratio of the nano-titanium dioxide powder, sodium hydroxide, and deionized water is 5:40:

200. C2. Add the titanium dioxide nanotubes obtained in step C1 to anhydrous ethanol containing zinc stearate, and impregnate them at 60°C and under vacuum for 4 hours. Then remove the ethanol by rotary evaporation and dry them to obtain zinc stearate-loaded titanium dioxide nanotubes. The mass ratio of the titanium dioxide nanotubes, zinc stearate and anhydrous ethanol is 10:8:(206-312); C3. Disperse the zinc stearate-loaded titanium dioxide nanotubes obtained in step C2 in tris(hydroxymethyl)aminomethane hydrochloride buffer, add dopamine hydrochloride, stir and polymerize at room temperature for 24 h, and centrifuge, wash and dry the reaction product to obtain titanium dioxide nanotube-loaded zinc stearate / polydopamine hydrophobic UV shielding agent. The mass ratio of the zinc stearate-supported titanium dioxide nanotubes, dopamine hydrochloride, and tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 10:2:

200.

7. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The wetting and dispersing agent is a hydrophilic modified ammonium polyacrylate.

8. The method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The defoamer is a mineral oil-based defoaming polymer.

9. A method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The leveling agent is a polyether-modified polysiloxane.

10. A method for producing a polyvinyl alcohol film according to claim 1, characterized in that: The cross-linking accelerator is citric acid.

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