A bio-based antibacterial cool breathable film and its preparation method

Abstract

This application relates to the field of plastic films, specifically disclosing a bio-based antibacterial cooling and breathable film and its preparation method. A bio-based antibacterial cooling and breathable film comprises the following raw materials by weight percentage: 49-66.5% matrix resin, 30-40% pore-forming agent, 1-3% silane-modified cellulose nanofibers, 1-2% antibacterial agent, 1-5% composite cooling agent, and 0.5-1% additives; the matrix resin comprises PBAT resin and PLA resin in a mass ratio of 7:3-5:5; the composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 5-15:1. The bio-based antibacterial cooling and breathable film of this application can be used in medical dressings, disposable medical supplies, and baby products, etc., and has the advantages of good breathability and moisture permeability, strong and long-lasting antibacterial ability, high mechanical strength, high cooling coefficient, and comfortable wear without feeling stuffy.

Description

Technical Field

[0001] This application relates to the field of plastic film technology, and more specifically, to a bio-based antibacterial cooling and breathable film and its preparation method. Background Technology

[0002] As people's demand for green, environmentally friendly, healthy and safe products increases, higher requirements are being placed on the performance of functional films in fields such as packaging materials, hygiene products, and medical protection.

[0003] In the field of medical protective equipment, for example, the films used in protective clothing and dressings have poor breathability, causing wearers to feel stuffy and uncomfortable. The antibacterial ingredients are mostly chemical additives, which have irritation and biocompatibility issues. Long-term use may cause skin allergies, and they do not have a cooling function, which will exacerbate the physical discomfort of medical staff in high-temperature environments. In the field of hygiene products, such as diapers and sanitary napkins, the poor breathability can easily lead to local dampness and stuffiness. At the same time, they lack antibacterial ingredients, making it difficult to inhibit bacterial growth and increasing the health risks of users. In addition, consumers have an increasing demand for a cooling experience in products, hoping to bring a cool and comfortable feeling through the material properties.

[0004] Currently, the main preparation methods for antibacterial, cooling, and breathable membranes include: 1. Blending modification method: Cooling materials and antibacterial agents are directly melt-blended with the matrix resin, and then extruded, cast, or blown into film. This preparation process is simple, low-cost, and suitable for large-scale production. However, antibacterial agents are prone to agglomeration, affecting the uniformity of dispersion, and cooling materials are prone to decomposition during high-temperature processing. 2. Surface coating method: A coating containing antibacterial agents and cooling components is applied to the surface of the breathable membrane. This method can retain the breathability of the base membrane, and the functional layer is controllable. However, the coating is prone to wear and has poor durability, and the cooling components (such as menthol) are prone to volatilization and aging. 3. Electrospinning method: Antibacterial agents and cooling materials are dispersed in a polymer solution, and nanofiber membranes are formed by electrospinning. Although nanofiber membranes have high porosity and good breathability, mass production is difficult, inefficient, and has weak mechanical strength. Moreover, traditional films mostly use petroleum-based polymer materials (such as polyethylene, polypropylene, polyurethane, etc.) as raw materials. These materials are difficult to degrade in the natural environment, easily causing "white pollution," which contradicts the concept of global sustainable development. In response to the aforementioned technologies, the inventors discovered an urgent need for an antibacterial, cooling, and highly durable bio-based breathable membrane. Summary of the Invention

[0005] To improve wearing comfort and reduce white pollution, this application provides a bio-based breathable membrane that is highly effective in inhibiting bacteria, has a cooling and breathable feel, and is highly strong.

[0006] In a first aspect, this application provides a bio-based antibacterial cooling and breathable membrane, employing the following technical solution:

[0007] A bio-based antibacterial cooling and breathable membrane comprises the following raw materials by weight percentage: 49-66.5% matrix resin, 30-40% pore-forming agent, 1-3% silane-modified cellulose nanofibers, 1-2% antibacterial agent, 1-5% composite cooling agent, and 0.5-1% additives.

[0008] The matrix resin comprises PBAT resin and PLA resin in a mass ratio of 7:3 to 5:5.

[0009] The composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 5-15:1.

[0010] By adopting the above technical solution, using PBAT and PLA as matrix resins, PBAT resin has good flexibility and ductility, while PLA provides high strength and biodegradability. The blending of the two can balance the mechanical properties and bio-based properties of the membrane, enabling the produced film to have good tensile strength, complete degradation, and environmental friendliness. The pore-forming agent can form a continuous microporous structure in the membrane, directly improving the membrane's permeability. Cellulose nanofibers themselves have high strength and biocompatibility, but are prone to aggregation due to hydrogen bonding and are highly polar, making them incompatible with non-cellular materials. Polar matrix resins have poor compatibility. After silane modification, the surface hydroxyl content is reduced, and the interfacial bonding force with the matrix resin and composite cooling agent is enhanced, reducing agglomeration and improving the tensile strength, modulus and other mechanical properties of the film. At the same time, the nanoscale size of silane-modified cellulose nanofibers can refine the microporous structure and form a three-dimensional network structure, which improves the mechanical properties of the film and helps to form air-permeable channels to ensure air permeability. This avoids the reduction of mechanical properties caused by the addition of pore-forming agents to increase porosity and air permeability. The strength loss is compensated by the cellulose nanofiber reinforced network.

[0011] Using nano-aluminum nitride and graphene as cooling agents, nano-aluminum nitride has a high thermal conductivity, which can quickly conduct heat and give a cooling sensation upon contact. Graphene has extremely high thermal conductivity, and together with nano-aluminum nitride, they form a thermally conductive network, accelerating the diffusion of heat from the skin to the environment, enhancing the cooling sensation, and improving the mechanical strength and antibacterial properties of the film. Moreover, this thermal conductivity can be maintained for a long time, avoiding the problem of traditional chemical cooling agents (such as menthol) becoming ineffective due to volatilization. In addition, both nano-aluminum nitride and graphene have excellent chemical stability, and are not easily decomposed under acidic or alkaline environments, light, or temperature changes. They do not react chemically with PBAT and PLA, and can maintain structural integrity for a long time, ensuring the continuous effectiveness of the thermal conductivity and avoiding the problems of cooling agent loss and rapid functional decay.

[0012] The addition of pore-forming agents creates a micron-scale porous structure in the film. The pores not only improve breathability but also provide "storage sites" for the composite cooling agent. When the film comes into contact with the skin, heat is quickly conducted to the pores through graphene and nano-aluminum nitride, and then diffused through air convection, achieving a cycle of "continuous heat dissipation - cooling sensation retention" and avoiding the attenuation of cooling sensation due to the failure of a single heat conduction path.

[0013] Optionally, the composite cooling agent is pretreated with a silane coupling agent.

[0014] By adopting the above technical solution and using silane coupling agents to modify nano-aluminum nitride and graphene, the dispersibility of nano-aluminum nitride and graphene can be effectively improved, and they can be uniformly dispersed in the film, thereby rapidly conducting heat on the film surface and avoiding agglomeration that would reduce thermal conductivity.

[0015] Optionally, the raw material for the silane-modified cellulose nanofibers comprises cellulose nanofibers and 1-5 wt% of a silane coupling agent.

[0016] By adopting the above technical solution, the silane coupling agent mainly reacts with some of the hydroxyl groups on the surface of cellulose nanofibers, significantly reducing surface polarity and reducing the tight packing between fibers due to hydrogen bonds. At the same time, the organic segments of the silane molecules increase the spacing between fibers, forming more "interconnected micropores" and improving air permeability. In addition, the organic segments of the silane molecules can act as bridges to enhance the interfacial bonding force between cellulose nanofibers and the matrix resin, so that the compatibility between cellulose nanofibers and the matrix resin reaches the optimal state.

[0017] Optionally, the silane coupling agent is selected from at least one of KH560, KH550, KH570, vinyltriethoxysilane, phenyltrimethoxysilane, and methyltrimethoxysilane.

[0018] By adopting the above technical solution, the surface of nano-aluminum nitride is rich in hydroxyl groups. The amino groups in KH550 can react with the hydroxyl groups to form covalent bonds. At the same time, the amino groups can interact with the ester groups of PBAT / PLA to improve compatibility. This type of silane coupling agent can form an organic coating layer on the surface of nano-aluminum nitride and graphene, reduce its surface energy, reduce the van der Waals forces between particles, thereby inhibiting agglomeration, making the particles uniformly dispersed in the matrix resin, and enhancing the interfacial forces to improve the mechanical and thermal properties of the film.

[0019] Cellulose nanofibers are rich in hydroxyl groups on their surface. KH560 contains epoxy groups and trimethoxysilane. The epoxy groups can react with the hydroxyl groups of cellulose nanofibers to form ether bonds. At the same time, the remaining methoxy groups are hydrolyzed and combined with the matrix resin. After modification, the hydrophobicity of cellulose nanofibers is enhanced, and their compatibility with the matrix resin is better. The above silane coupling agent can reduce the hydrophilicity of the surface of cellulose nanofibers, improve their compatibility with the matrix resin, prevent them from forming agglomerates in the matrix resin, and retain the nanoscale reinforcement effect of cellulose nanofibers, thereby improving the mechanical properties and thermal stability of the film.

[0020] Optionally, the raw material of the antibacterial agent includes chitosan quaternary ammonium salt.

[0021] By adopting the above technical solution, the quaternary ammonium groups on the chitosan quaternary ammonium salt molecular chain are positively charged, which can adsorb the negatively charged bacterial cell membrane through electrostatic interaction, destroy the membrane structure and cause intracellular substances to leak out, thereby achieving contact sterilization.

[0022] Optionally, the antibacterial agent is prepared as follows:

[0023] Chitosan quaternary ammonium salt was added to a PVA solution with a concentration of 8-10 wt%, and electrospun to obtain primary fibers. After being pulverized, the fibers were dispersed in deionized water, and a photo-sterilizer was added. After mixing evenly, the mixture was filtered, cross-linked with glutaraldehyde vapor at room temperature, and freeze-dried to obtain an antibacterial agent. The mass ratio of polyvinyl alcohol, chitosan quaternary ammonium salt, and photo-sterilizer was 1:0.08-0.1:0.05-0.08.

[0024] By adopting the above technical solution, polyvinyl alcohol is used as the spinning matrix to form a fiber skeleton, which is combined with chitosan quaternary ammonium salt through hydrogen bonding to enhance fiber stability and refine fiber diameter. After the resulting primary fibers are mixed with a photo-sterilizer, when cross-linked with glutaraldehyde vapor, the hydroxyl groups of polyvinyl alcohol react with the amino groups of chitosan to form a cross-linked network, which improves the mechanical strength of the fibers. Moreover, the glutaraldehyde vapor cross-linking causes polyvinyl alcohol and chitosan quaternary ammonium salt to form a chemical cross-linked network, which works synergistically with the formed porous fiber structure to provide a three-dimensional loading space for chitosan quaternary ammonium salt and photo-sterilizer, reducing the direct exposure of antibacterial components, fixing the photo-sterilizer, preventing dissolution, and reducing migration and loss. Freeze-drying preserves the porous structure of the fibers, increases the specific surface area, and improves the interface area between the antibacterial agent and the matrix resin. The contact sterilization of chitosan quaternary ammonium salt and the photo-driven sterilization of the photo-sterilizer complement each other. Under lightless conditions, the sterilization mainly relies on chitosan quaternary ammonium salt, while the sterilization efficiency is improved under light.

[0025] Furthermore, the electrospun fibers of polyvinyl alcohol and chitosan quaternary ammonium salt have high aspect ratio and mechanical strength, which can serve as a reinforcing phase in the film. By dispersing stress concentration through the interfacial bonding between the fiber and the film matrix, the tensile strength of the film is improved. In particular, the porous structure of the fiber after freeze-drying increases interfacial bonding and improves the air permeability of the film. Moreover, the fiber network has a fixing effect on the composite cooling agent, which can reduce the migration of nano-aluminum nitride and graphene, making the cooling sensation more lasting.

[0026] Optionally, the photo-sterilizer is prepared using the following method:

[0027] The bacterial cellulose aqueous dispersion and tannic acid were mixed and stirred at 40-60℃ for 10-12 hours. Carbon dot powder was added and stirring was continued for 2-4 hours. The mixture was then freeze-dried under vacuum. The mass ratio of bacterial cellulose, tannic acid and carbon dot powder was 5:1-2:2-3.

[0028] By employing the above technical solution, tannic acid has a large number of phenolic hydroxyl groups distributed on its surface, providing various interaction binding sites. This gives tannic acid a strong bonding ability, enabling it to combine with other molecules through non-covalent interactions such as hydrogen bonds and hydrophobic interactions. The catechol groups on the tannic acid molecule, also known as catechin groups, can be used to bind with various substrates through reversible non-covalent interactions, thus endowing tannic acid with good adhesion properties. Moreover, phenolic structures are excellent hydrogen donors, providing superior antioxidant properties. Bacterial cellulose molecules are rich in hydroxyl groups, and the fiber network structure is loose, with exposed hydroxyl groups on the surface acting as hydrogen bond donors / acceptors. The phenolic hydroxyl groups in tannic acid can bind with bacterial cellulose... The hydroxyl groups of vitamin are linked by hydrogen bonds, anchoring tannic acid and carbon dots in the network framework of bacterial cellulose to form stable composite nanoparticles. Tannic acid itself is a natural antibacterial agent that can kill or inhibit bacteria by disrupting bacterial cell membranes, inhibiting enzyme activity, and chelating essential metal ions. Carbon dots have excellent photocatalytic activity and can generate a large amount of reactive oxygen species under light, which can disrupt bacterial cell membranes and achieve efficient sterilization. The porous structure of bacterial cellulose can also capture bacteria through physical adsorption, achieving a dual bactericidal effect of physical and chemical action. Some tannic acid may generate a small amount of reactive oxygen species (ROS) under light, which synergistically enhances the photocatalytic sterilization effect with the carbon dot photocatalytic bactericide.

[0029] The three-dimensional porous structure of bacterial cellulose provides a carrier for tannic acid and carbon dots, slowing down their release rate. The complex of tannic acid, bacterial cellulose, and carbon dots transforms the antibacterial effect of the cooling membrane from instantaneous to long-lasting. Furthermore, the natural antibacterial properties of tannic acid synergistically work with chitosan quaternary ammonium salts, resulting in a broader antibacterial spectrum, making it particularly suitable for skin-contact cooling membranes (such as cooling dressings and close-fitting cooling fabrics). Additionally, the bacterial cellulose fibers form a three-dimensional network through hydrogen bonds, exhibiting extremely high mechanical strength and flexibility. Tannic acid, acting as a cross-linking agent, connects bacterial cellulose to the matrix resin via hydrogen bonds, reducing interfacial defects, improving stress transfer efficiency, and enhancing the membrane's tensile strength and elongation at break. Moreover, the porosity of the bacterial cellulose network promotes the exchange of moisture and gas between the membrane's interior and exterior, improving breathability and water absorption, preventing discomfort caused by stuffiness during use. Both tannic acid and bacterial cellulose are natural biomass materials and do not introduce toxic components.

[0030] Optionally, the additive is selected from at least one of chain extenders, lubricants, and plasticizers.

[0031] Optionally, the chain extender is selected from at least one of BASF ADR4400, diphenylmethane diisocyanate, and hexamethylene diisocyanate;

[0032] The lubricant is selected from at least one of erucamide, stearic acid, pentaerythritol stearate and ethylene bis-stearamide;

[0033] The plasticizer is selected from at least one of tributyl citrate, acetylated tributyl citrate, epoxidized soybean oil, triacetin, and epoxidized fatty acid methyl ester.

[0034] Secondly, this application provides a method for preparing a bio-based antibacterial cooling and breathable membrane, using the following technical solution:

[0035] A method for preparing a bio-based antibacterial cooling and breathable membrane includes the following steps:

[0036] Preparation of silanized cellulose nanofibers: Cellulose nanofibers were dispersed in an ethanol / water mixed solution and ultrasonically treated to form a suspension;

[0037] The silane coupling agent was added to an ethanol / water mixture at a dosage of 1-5 wt% relative to the cellulose nanofibers. The pH was adjusted to 4-5, and the mixture was stirred until clear. The mixture was then added to the suspension and stirred at 60-80℃ for 4-6 hours. After cooling, centrifugation, washing with ethanol, and vacuum drying or freeze drying, silanized cellulose nanofibers were obtained.

[0038] Preparation of composite cooling agent: Nano-aluminum nitride and graphene are mixed, added to a silane coupling agent solution, ultrasonically dispersed, filtered and dried to obtain composite cooling agent;

[0039] Preparation of breathable masterbatch: The base resin, pore-forming agent, silane-modified cellulose nanofibers, antibacterial agent, composite cooling agent and additives are mixed and melt-extruded to obtain breathable masterbatch;

[0040] Preparation of breathable membrane: The breathable masterbatch is dried, hot-melted, and extruded to obtain a melt. The temperature of the feeding section is 155-165℃, the temperature of the die section is 165-175℃, and the screw speed is 40-70rpm. The melt is passed through the casting roller to form a casting sheet, which is then biaxially stretched, cooled and shaped, and wound up to obtain the breathable membrane.

[0041] By adopting the above technical solutions, cellulose nanofibers have a reinforcing effect on membrane materials. However, since they are hydrophilic materials, direct melt extrusion can easily lead to delamination. Therefore, modifying cellulose nanofibers with silanes can improve their interfacial compatibility and enhance the mechanical strength of the membrane material. At the same time, adding pore-forming agents can increase the breathability of the membrane material, accelerate sweat evaporation, keep the skin dry, and avoid stickiness. Cooling factors can produce a cooling sensation upon contact, relieving stuffiness and discomfort. Moreover, the addition of antibacterial agents can inhibit bacterial growth in the membrane material, reducing odor and the risk of cross-infection. Furthermore, bio-based materials are biodegradable, reducing plastic pollution, and have high potential application value in fields such as medical dressings, disposable medical supplies, and maternal and infant products.

[0042] In summary, this application has the following beneficial effects:

[0043] 1. Because this application uses silane-modified cellulose nanofibers, utilizes nano-aluminum nitride and graphene as composite cooling agents, and adds antibacterial agents and pore-forming agents to make a breathable membrane with microporous structure and antibacterial ability, it improves the mechanical strength, breathability and moisture permeability of the bio-based membrane and its ability to inhibit bacterial growth. In addition, the composite cooling agent can give the breathable membrane a cool feeling upon contact, reduce stuffiness, and improve comfort.

[0044] 2. In this application, chitosan quaternary ammonium salt is preferably added to a polyvinyl alcohol solution. After spinning, a photo-sterilizer is added, followed by glutaraldehyde vapor crosslinking. This allows the chitosan quaternary ammonium salt and polyvinyl alcohol to form a chemical crosslinking network, reducing the dissolution of the photo-sterilizer and improving the antibacterial durability. Furthermore, the fibers formed by polyvinyl alcohol and chitosan quaternary ammonium salt can also serve as a reinforcing phase, improving the tensile strength of the membrane. At the same time, the porous structure formed by freeze-drying can also fix the composite cooling agent, making the cooling sensation more lasting.

[0045] 3. In this application, tannic acid and bacterial cellulose are used to form composite particles, which are then mixed with carbon dot powder to prepare a photo-sterilizer. This achieves both physical and chemical sterilization, prolongs the sterilization effect, and increases mechanical strength and flexibility. Detailed Implementation

[0046] The following embodiments provide a further detailed description of this application.

[0047] Example I: 1.057 g of citric acid, 21.8 ml of silane coupling agent KH-792 and 40 ml of deionized water were mixed and reacted at 200 °C for 6 h. After cooling to room temperature, the mixture was dialyzed and dried.

[0048] Examples of Antibacterial Agent Preparation 1-8

[0049] Preparation Example 1: 30g of polyvinyl alcohol powder was added to deionized water to prepare a 10wt% PVA solution. 3g of chitosan quaternary ammonium salt was added to the PVA solution, and electrospinning was performed to obtain primary fibers. After pulverization, the fibers were dispersed in deionized water, and 2.4g of photo-sterilizing carbon dot powder was added. After mixing evenly, the mixture was filtered, crosslinked with glutaraldehyde vapor at room temperature for 24h, and then freeze-dried for 24h. The carbon dot powder was prepared in Preparation Example 1. The polyvinyl alcohol was type 17-99, and the chitosan quaternary ammonium salt was selected from Aisen Biotechnology, catalog number ASSW-250324125. The electrospinning speed was 0.5ml / h, the voltage was 20kV, and the receiving distance was 15cm.

[0050] Preparation Example 2: 30g of polyvinyl alcohol powder was added to deionized water to prepare a PVA solution with a concentration of 8wt%. 2.4g of chitosan quaternary ammonium salt was added to the PVA solution, and electrospinning was performed to obtain primary fibers. After being crushed, the fibers were dispersed in deionized water, and 1.5g of photo-sterilizing carbon dot powder was added. After mixing evenly, the mixture was filtered, crosslinked with glutaraldehyde vapor at room temperature for 24h, and then freeze-dried for 24h. The carbon dot powder was prepared in Preparation Example 1. The polyvinyl alcohol was of type 17-99, and the chitosan quaternary ammonium salt was selected from Aisen Biotechnology, catalog number ASSW-250324125. The electrospinning speed was 0.5ml / h, the voltage was 18kV, and the receiving distance was 10cm.

[0051] Preparation Example 3: The difference from Preparation Example 1 is that polyvinyl alcohol was not added. The specific method is as follows: 3g of chitosan quaternary ammonium salt and 2.4g of carbon dot powder were mixed evenly to prepare an antibacterial agent.

[0052] Preparation Example 4: The difference from Preparation Example 1 is that the photo-sterilizer is prepared by the following method: 5g of bacterial cellulose aqueous dispersion and 2g of tannic acid are mixed evenly, stirred at 60°C for 10h, 3g of carbon dot powder is added, stirring is continued for 4h, and then vacuum freeze-drying is performed. The bacterial cellulose aqueous dispersion is selected from Guilin Qihong Technology and has a solid content of 0.8%. The carbon dot powder is prepared by Preparation Example I.

[0053] Preparation Example 5: The difference from Preparation Example 1 is that the photo-sterilizer is prepared by the following method: 5g of bacterial cellulose aqueous dispersion and 1g of tannic acid are mixed evenly, stirred at 40°C for 12h, 2g of carbon dot powder is added, stirring is continued for 2h, and then vacuum freeze-drying is performed. The bacterial cellulose aqueous dispersion is selected from Guilin Qihong Technology and has a solid content of 0.8%. The carbon dot powder is prepared by Preparation Example I.

[0054] Preparation Example 6: The difference from Preparation Example 4 is that an equal amount of bacterial cellulose aqueous dispersion is used instead of tannic acid. Specifically, 7g of bacterial cellulose aqueous dispersion is mixed with 3g of carbon dot powder, stirred at 60°C for 4h, and then freeze-dried under vacuum. The bacterial cellulose aqueous dispersion is selected from Guilin Qihong Technology and has a solid content of 0.8%. The carbon dot powder is prepared from Preparation Example I.

[0055] Preparation Example 7: The difference from Preparation Example 4 is that an equal amount of tannic acid was used instead of the bacterial cellulose aqueous dispersion. Specifically, 7g of tannic acid and 3g of carbon dot powder were mixed evenly, stirred at 60°C for 4 hours, and then freeze-dried under vacuum. The bacterial cellulose aqueous dispersion was selected from Guilin Qihong Technology and had a solid content of 0.8%. The carbon dot powder was prepared from Preparation Example I.

[0056] Preparation Example 8: The difference from Preparation Example 4 is that no carbon dot powder was added. 5g of bacterial cellulose aqueous dispersion and 2g of tannic acid were mixed evenly, stirred at 60°C for 10h, and then freeze-dried under vacuum. The bacterial cellulose aqueous dispersion was selected from Guilin Qihong Technology and had a solid content of 0.8%. Example

[0057] Example 1: A bio-based antibacterial cooling and breathable membrane, the raw material amounts of which are shown in Table 1. The matrix resin includes PBAT resin and PLA resin in a mass ratio of 7:3. The PBAT resin is selected from Lanshan Tunhe, brand name TH801T, and the PLA resin is selected from Nature Works, USA, brand name 2003D. The antibacterial agent is chitosan quaternary ammonium salt, which is selected from Aisen Biotechnology, catalog number ASSW-250324125. The composite cooling agent includes nano-aluminum nitride and graphene in a mass ratio of 6:1 and is pretreated with silane coupling agent KH550. The additives include chain extender and lubricant in a mass ratio of 2:3. The chain extender is BASF ADR4400, and the lubricant is erucamide.

[0058] The preparation method of the above-mentioned bio-based antibacterial cooling and breathable membrane includes the following steps:

[0059] S1. Preparation of silanized cellulose nanofibers:

[0060] 1) Disperse 100g of dried cellulose nanofibers in 2000g of ethanol / water mixed solvent (volume ratio 8:1), and sonicate at 300W for 30min to form a uniform suspension.

[0061] 2) Add 30g of silane coupling agent KH560 to an ethanol / water mixed solution (volume ratio 9:1) at 3wt% relative to the mass of cellulose nanofibers, adjust the pH to 4 with hydrochloric acid, stir at 40℃ for 1h until the solution is clear, and prepare a silane solution.

[0062] 3) Dissolve silane and slowly add it to the suspension, heat to 60°C, stir continuously for 6 hours, cool to room temperature, centrifuge at 8000 rpm for 10 minutes, collect the precipitate, wash it 3 times with ethanol to remove unreacted silane coupling agent, and vacuum dry at 60°C for 12 hours to obtain silanized cellulose nanofibers.

[0063] S2. Preparation of the composite cooling agent:

[0064] Nano-aluminum nitride and graphene were mixed at a mass ratio of 6:1 and placed in a 3wt% aqueous solution of silane coupling agent. The mixture was sonicated at 300W for 30 minutes, filtered, and dried to obtain a surface-modified composite cooling agent.

[0065] S3. Preparation of air-permeable masterbatch:

[0066] The matrix resin, pore-forming agent, silane-modified cellulose nanofibers, antibacterial agent, cooling agent and additives are mixed evenly and then hot-melt extruded at 175°C to obtain air-permeable masterbatch.

[0067] S4. Preparation of the breathable membrane:

[0068] The permeable masterbatch was dried at 80℃ for 12 hours, then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 160℃, the die section temperature was 170℃, and the screw speed was 70 rpm. The melt was then passed through a casting roller at 20℃ to form a casting sheet. The casting sheet was then subjected to biphase stretching at 110℃, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4. After cooling, shaping, and winding, a basis weight of 30.5 g / m³ was obtained. 2 A breathable membrane.

[0069] Table 1 Raw material usage of bio-based antibacterial cooling and breathable membrane

[0070]

[0071] Example 2: A bio-based antibacterial cooling and breathable membrane, the raw material amounts of which are shown in Table 1. The matrix resin includes PBAT resin and PLA resin in a mass ratio of 5:5. The PBAT resin is selected from Lanshan Tunhe, brand name TH801T, and the PLA resin is selected from Nature Works, USA, brand name 2003D. The antibacterial agent is chitosan quaternary ammonium salt, which is selected from Aisen Biotechnology, catalog number ASSW-250324125. The composite cooling agent includes nano-aluminum nitride and graphene in a mass ratio of 10:1 and is pretreated with silane coupling agent KH550. The additives include chain extender and lubricant in a mass ratio of 1:4. The chain extender is BASF ADR4400, and the lubricant is erucamide.

[0072] The preparation method of the above-mentioned bio-based antibacterial cooling and breathable membrane includes the following steps:

[0073] S1. Preparation of silanized cellulose nanofibers:

[0074] 1) Disperse 100g of dried cellulose nanofibers in 2000g of ethanol / water mixed solvent (volume ratio 8:1), and sonicate at 300W for 30min to form a uniform suspension.

[0075] 2) Add 30g of silane coupling agent KH560 to an ethanol / water mixed solution (volume ratio 9:1) at 5wt% relative to the mass of cellulose nanofibers, adjust the pH to 5 with hydrochloric acid, stir at 40℃ for 2h until the solution is clear, and prepare a silane solution.

[0076] 3) Dissolve silane and slowly add it to the suspension, heat to 80°C, stir continuously for 4 hours, cool to room temperature, centrifuge at 8000 rpm for 10 minutes, collect the precipitate, wash it 3 times with ethanol to remove unreacted silane coupling agent, and vacuum dry at 60°C for 12 hours to obtain silanized cellulose nanofibers.

[0077] S2. Preparation of the composite cooling agent:

[0078] Nano-aluminum nitride and graphene were mixed at a mass ratio of 10:1 and placed in a 5wt% aqueous solution of silane coupling agent. The mixture was sonicated at 300W for 30 minutes, filtered, and dried to obtain a surface-modified composite cooling agent.

[0079] S3. Preparation of air-permeable masterbatch:

[0080] The matrix resin, pore-forming agent, silane-modified cellulose nanofibers, antibacterial agent, cooling agent and additives are mixed evenly and then hot-melt extruded at 165°C to obtain air-permeable masterbatch.

[0081] S4. Preparation of the breathable membrane:

[0082] The permeable masterbatch was dried at 80℃ for 12 hours, then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 165℃, the die section temperature was 175℃, and the screw speed was 60 rpm. The melt was then passed through a casting roller at 20℃ to form a casting sheet. The casting sheet was then subjected to biphase stretching at 110℃, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4. After cooling, shaping, and winding, a sheet with a basis weight of 30 g / m³ was obtained. 2 A breathable membrane.

[0083] Example 3: A bio-based antibacterial cooling and breathable membrane, the raw material amounts of which are shown in Table 1. The matrix resin includes PBAT resin and PLA resin in a mass ratio of 6:4. The PBAT resin is selected from Lanshan Tunhe, brand name TH801T, and the PLA resin is selected from Nature Works, USA, brand name 2003D. The antibacterial agent is chitosan quaternary ammonium salt, which is selected from Aisen Biotechnology, catalog number ASSW-250324125. The composite cooling agent includes nano-aluminum nitride and graphene in a mass ratio of 15:1 and is pretreated with silane coupling agent KH550. The additives include chain extender and lubricant in a mass ratio of 5:5. The chain extender is BASF ADR4400, and the lubricant is erucamide.

[0084] The preparation method of the above-mentioned bio-based antibacterial cooling and breathable membrane includes the following steps:

[0085] S1. Preparation of silanized cellulose nanofibers:

[0086] 1) Disperse 100g of dried cellulose nanofibers in 2000g of ethanol / water mixed solvent (volume ratio 8:1), and sonicate at 300W for 30min to form a uniform suspension.

[0087] 2) Add 30g of silane coupling agent KH560 to an ethanol / water mixed solution (volume ratio 9:1) at 1wt% relative to the mass of cellulose nanofibers, adjust the pH to 5 with hydrochloric acid, stir at 40℃ for 2h until the solution is clear, and prepare a silane solution.

[0088] 3) Dissolve silane and slowly add it to the suspension, heat to 70°C, stir continuously for 5 hours, cool to room temperature, centrifuge at 8000 rpm for 10 minutes, collect the precipitate, wash it three times with ethanol to remove unreacted silane coupling agent, and vacuum dry at 60°C for 12 hours to obtain silanized cellulose nanofibers.

[0089] S2. Preparation of the composite cooling agent:

[0090] Nano-aluminum nitride and graphene were mixed at a mass ratio of 15:1 and placed in a 1wt% aqueous solution of silane coupling agent. The mixture was sonicated at 300W for 30 minutes, filtered, and dried to obtain a surface-modified composite cooling agent.

[0091] S3. Preparation of air-permeable masterbatch:

[0092] The matrix resin, pore-forming agent, silane-modified cellulose nanofibers, antibacterial agent, cooling agent and additives are mixed evenly and then hot-melt extruded at 160°C to obtain air-permeable masterbatch.

[0093] S4. Preparation of the breathable membrane:

[0094] The permeable masterbatch was dried at 80℃ for 12 hours, then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 155℃, the die section temperature was 165℃, and the screw speed was 40 rpm. The melt was then passed through a casting roller at 20℃ to form a casting sheet. The casting sheet was then subjected to biphase stretching at 110℃, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4. After cooling, shaping, and winding, a basis weight of 30.3 g / m³ was obtained. 2 A breathable membrane.

[0095] Example 4: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that the composite cooling agent is not pretreated with an aqueous solution of silane coupling agent KH550.

[0096] Example 5: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that the amount of silane coupling agent KH560 in the silane-modified cellulose nanofibers is 15 wt% of the mass of the cellulose nanofibers.

[0097] Example 6: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that the antibacterial agent is prepared in Preparation Example 1.

[0098] Example 7: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that the antibacterial agent is prepared by Example 2.

[0099] Example 8: A bio-based antibacterial cooling and breathable membrane, which differs from Example 6 in that the antibacterial agent is prepared by Preparation Example 3.

[0100] Example 9: A bio-based antibacterial cooling and breathable membrane, which differs from Example 6 in that the antibacterial agent is prepared by Example 4.

[0101] Example 10: A bio-based antibacterial cooling and breathable membrane, which differs from Example 6 in that the antibacterial agent is prepared by Example 5.

[0102] Example 11: A bio-based antibacterial cooling and breathable membrane, which differs from Example 9 in that the antibacterial agent is prepared by Preparation Example 6.

[0103] Example 12: A bio-based antibacterial cooling and breathable membrane, which differs from Example 9 in that the antibacterial agent is prepared by Example 7.

[0104] Example 13: A bio-based antibacterial cooling and breathable membrane, which differs from Example 9 in that the antibacterial agent is prepared by Example 8.

[0105] Comparative Example

[0106] Comparative Example 1: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that the composite cooling agent includes nano-aluminum nitride and graphene in a mass ratio of 1:6, and has not been pretreated with silane coupling agent KH550.

[0107] Comparative Example 2: A bio-based antibacterial cooling and breathable membrane, which differs from Example 1 in that it uses cellulose nanofibers that have not been modified with silane.

[0108] Performance testing

[0109] Bio-based antibacterial cooling and breathable membranes were prepared according to the methods in the examples and comparative examples, and their performance was tested according to the following methods. The test results are recorded in Table 2.

[0110] 1. Contact Cooling Coefficient: A breathable membrane measuring 200mm × 200mm was cut and conditioned for 24 hours in a constant temperature and humidity chamber according to GB / T6529-2008. The contact cooling coefficient of the breathable membrane was then tested using a KES-F7 contact cooling and warming tester. The test method adopted GB / T35263-2017 "Test and Evaluation of Instantaneous Cooling Performance of Textiles". The temperature of the sample stage was 20±0.5℃, the temperature of the thermal testing plate was 35±0.5℃, and the temperature difference between the plate and the sample stage was 15℃. Five locations were selected for testing for each type of sample, and the average value was taken.

[0111] 2. Breaking strength and elongation: The test was conducted in accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Tests on films and sheets". The sample size was 150 mm long × 10 mm wide, the initial distance between the clamps was 50 mm, the test speed was 500 mm / min, and the test continued until the sample broke. The maximum tensile load was measured to an accuracy of 0.01 N. The test was repeated 5 times and the average value was taken.

[0112] 3. Moisture permeability: Tested according to GB / T 21529-2008 "Test of water vapor transmission rate of plastic films and sheets - Electrolytic sensor method", with a test temperature of 38℃, a relative humidity of 90%, a sample diameter of 10cm, and a test area of ​​63.58cm². 2 .

[0113] 4. Antibacterial rate: Antibacterial performance was evaluated according to AATCC 100-2012 "Evaluation Methods for Antimicrobial Textiles". Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) were selected as test bacteria. The breathable membrane was cut into uniformly sized circular samples and placed in a 24-well plate. The absorbance of the bacterial solution was measured using a UV spectrophotometer, ensuring it was within the range of 0.25-0.35. 0.1 ml of bacterial solution was added to the sample, and the plate was placed under light conditions (xanthium lamp, wavelength > 420 nm) for 30 min and 28 days, respectively. 0.9 mL of PBS was added and the mixture was shaken well. Then, 0.1 ml of the original bacterial solution and the bacterial solution on the sample were serially diluted 1×10⁻⁶ in centrifuge tubes. 6 (Each sample was tested in 3 parallel groups). 50 μL of each dilution gradient solution was dropped onto a culture medium plate and then incubated in a 37℃ constant temperature incubator for 24 h. Finally, the colony count of each group was recorded, and the inhibition rate was calculated according to the following formula: Inhibition rate = N0 - N1 / N0 × 100%, where N0 is the maximum number of colonies in the original bacterial solution that can be counted, and N1 is the colony value of the sample after antibacterial treatment at the corresponding gradient of the original bacterial solution.

[0114] Table 2 Performance test results of bio-based antibacterial cooling and breathable membrane

[0115]

[0116] A comparison of the data from Examples 1-3 and Table 2 shows that the membrane material made using the raw material amounts in Examples 1-3 has a high contact cooling coefficient and moisture permeability, good contact cooling sensation, and is not prone to stuffiness. It also has strong tensile strength and elongation at break, high mechanical strength, and strong antibacterial ability.

[0117] In Example 4, no silane coupling agent KH550 was used to pretreat the composite cooling agent. It can be seen that the membrane material prepared in Example 4 has a slightly lower tensile strength and a smaller contact cooling coefficient compared with Example 1. This indicates that the silane coupling agent pretreatment can improve the compatibility between the composite cooling agent and the matrix resin and increase the dispersibility of the composite cooling agent.

[0118] Compared with Example 1, Example 5 shows an increase in the amount of silane coupling agent KH560 in the silane-modified cellulose nanofibers. It can be seen that the tensile strength and elongation of the membrane material prepared in Example 5 are slightly reduced, the contact cooling coefficient is reduced, the cool tactile sensation is worse, and the moisture permeability is reduced. This indicates that excessive silane coupling agent will lead to interface defects or pore blockage, affecting the air permeability of the membrane material.

[0119] Compared with Example 1, Examples 6 and 7 used the antibacterial agents prepared in Examples 1 and 2 of this application, respectively. Compared with the chitosan quaternary ammonium salt in Example 1, polyvinyl alcohol spinning was also used, and carbon dot powder was added. In addition, glutaraldehyde vapor crosslinking was also used. As can be seen from the data comparison in Table 2, the membrane materials prepared in Examples 6 and 7 have enhanced antibacterial durability, slightly increased tensile strength, and improved moisture permeability. This indicates that the antibacterial agent prepared in this application not only improves antibacterial ability but also improves antibacterial durability, while also increasing the moisture permeability and mechanical strength of the membrane material.

[0120] Compared to Example 6, Example 8 used the antibacterial agent prepared in Preparation Example 3. In Preparation Example 3, no polyvinyl alcohol was added and no electrospinning was performed. The antibacterial agent was prepared by mixing chitosan quaternary ammonium salt and carbon dot powder. It can be seen that the initial antibacterial rate of the prepared membrane material did not change much, but the decrease rate of the antibacterial rate after 28 days was greater than that in Example 6, the antibacterial long-term effect was weakened, and the tensile strength and elongation of the membrane material decreased.

[0121] Compared with Example 6, Examples 9 and 10 used antibacterial agents prepared in Preparation Examples 4 and 5, respectively. The photo-sterilizing agents not only contained carbon dot powder, but also added bacterial cellulose and tannic acid. The data in Table 2 show that the membrane materials prepared in Examples 9 and 10 have increased tensile strength and elongation, improved antibacterial ability, and further improved antibacterial durability.

[0122] In Example 11, the antibacterial agent prepared in Preparation Example 6 was used, with bacterial cellulose aqueous dispersion used instead of tannic acid. The antibacterial ability decreased, but the decrease in antibacterial rate after 28 days was not much different from that in Example 9, indicating that tannic acid can increase the antibacterial ability. In Example 12, the antibacterial agent prepared in Preparation Example 7 was used, with tannic acid used to replace bacterial cellulose in an equal amount. Table 2 shows that the membrane material prepared in Example 12 had a lower antibacterial durability compared to Example 9, indicating that the combination of bacterial cellulose and tannic acid can improve the antibacterial ability and antibacterial durability of the membrane material, as well as improve the moisture permeability and mechanical strength of the membrane material.

[0123] In Comparative Example 1, the amount of graphene in the composite cooling agent was increased, and it was not modified with a silane coupling agent. The resulting membrane material had a lower cooling coefficient and reduced tensile strength. This indicates that even if the amount of graphene is increased, it will not significantly increase the cooling coefficient. This is because excessive graphene will cause agglomeration in the matrix resin, resulting in rapid local heat loss. The agglomerates lack effective heat conduction paths, leading to uneven cooling. It will also reduce mechanical strength and moisture permeability.

[0124] In Comparative Example 2, no silane was used to modify the cellulose nanofibers. As can be seen, the membrane material produced in Comparative Example 2 had a lower tensile strength and reduced moisture permeability compared to Example 1. This indicates that silane modification can increase the compatibility between cellulose nanofibers and the matrix resin and improve the mechanical strength of the membrane material.

[0125] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A bio-based antibacterial cooling and breathable membrane, characterized in that, The raw materials include the following weight percentages: 49-66.5% matrix resin, 30-40% pore-forming agent, 1-3% silane-modified cellulose nanofibers, 1-2% antibacterial agent, 1-5% composite cooling agent, and 0.5-1% additives. The matrix resin comprises PBAT resin and PLA resin in a mass ratio of 7:3 to 5:

5. The composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 5-15:1; The raw material of the antibacterial agent includes chitosan quaternary ammonium salt; The method for preparing the antibacterial agent is as follows: Chitosan quaternary ammonium salt was added to a PVA solution with a concentration of 8-10 wt%, and electrospun to obtain primary fibers. After being pulverized, the fibers were dispersed in deionized water, and a photo-sterilizer was added. After mixing evenly, the mixture was filtered, cross-linked with glutaraldehyde vapor at room temperature, and freeze-dried to obtain an antibacterial agent. The mass ratio of polyvinyl alcohol, chitosan quaternary ammonium salt, and photo-sterilizer was 1:0.08-0.1:0.05-0.

08.

2. The bio-based antibacterial cooling and breathable membrane according to claim 1, characterized in that: The composite cooling agent is pretreated with a silane coupling agent.

3. The bio-based antibacterial cooling and breathable membrane according to claim 1, characterized in that: The raw material for the silane-modified cellulose nanofibers includes cellulose nanofibers and 1-5 wt% of a silane coupling agent.

4. The bio-based antibacterial cooling and breathable membrane according to claim 2 or 3, characterized in that: The silane coupling agent is selected from at least one of KH560, KH550, KH570, vinyltriethoxysilane, phenyltrimethoxysilane, and methyltrimethoxysilane.

5. The bio-based antibacterial cooling and breathable membrane according to claim 1, characterized in that: The photo-sterilizer is prepared using the following method: The bacterial cellulose aqueous dispersion and tannic acid were mixed and stirred at 40-60℃ for 10-12 hours. Carbon dot powder was added and stirring was continued for 2-4 hours. The mixture was then freeze-dried under vacuum. The mass ratio of bacterial cellulose, tannic acid and carbon dot powder was 5:1-2:2-3.

6. The bio-based antibacterial cooling and breathable membrane according to claim 1, characterized in that: The additive is selected from at least one of chain extenders, lubricants, and plasticizers.

7. The bio-based antibacterial cooling and breathable membrane according to claim 6, characterized in that: The chain extender is selected from at least one of BASF ADR4400, diphenylmethane diisocyanate and hexamethylene diisocyanate; The lubricant is selected from at least one of erucamide, stearic acid, pentaerythritol stearate and ethylene bis-stearamide; The plasticizer is selected from at least one of tributyl citrate, acetylated tributyl citrate, epoxidized soybean oil, triacetin, and epoxidized fatty acid methyl ester.

8. A method for preparing the bio-based antibacterial cooling and breathable membrane according to any one of claims 1-7, characterized in that: Includes the following steps: Preparation of silane-modified cellulose nanofibers: Cellulose nanofibers were dispersed in an ethanol / water mixed solution and ultrasonically treated to form a suspension; The silane coupling agent was added to an ethanol / water mixture at a dosage of 1-5 wt% relative to the cellulose nanofibers. The pH was adjusted to 4-5, and the mixture was stirred until clear. The mixture was then added to the suspension and stirred at 60-80℃ for 4-6 hours. After cooling, centrifugation, washing with ethanol, and vacuum drying or freeze drying, silanized cellulose nanofibers were obtained. Preparation of composite cooling agent: Nano-aluminum nitride and graphene are mixed, added to a silane coupling agent solution, ultrasonically dispersed, filtered, and dried to obtain composite cooling agent; Preparation of breathable masterbatch: The base resin, pore-forming agent, silane-modified cellulose nanofibers, antibacterial agent, composite cooling agent and additives are mixed and melt-extruded to obtain breathable masterbatch; Preparation of breathable membrane: The breathable masterbatch is dried, hot-melted, and extruded to obtain a melt. The temperature of the feeding section is 155-165℃, the temperature of the die section is 165-175℃, and the screw speed is 40-70rpm. The melt is passed through the casting roller to form a casting sheet, which is then biaxially stretched, cooled and shaped, and wound up to obtain the breathable membrane.

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