Bio-based antibacterial cool-feeling breathable film and preparation method thereof

Abstract

The invention relates to the field of plastic films, and particularly discloses a bio-based antibacterial cool-feeling breathable film and a preparation method thereof. The bio-based antibacterial cool-feeling breathable film is prepared from the following raw materials in percentage by weight: 49 to 66.5 percent of matrix resin, 30 to 40 percent of pore-foaming agent, 1 to 3 percent of silane modified cellulose nanofiber, 1 to 2 percent of antibacterial agent, 1 to 5 percent of composite cool-feeling agent and 0.5 to 1 percent of auxiliary agent, the matrix resin comprises PBAT resin and PLA resin in a mass ratio of (7: 3)-(5: 5); the composite cool feeling agent comprises nano aluminum nitride and graphene in a mass ratio of (5-15): 1. The bio-based antibacterial cool-feeling breathable film can be used for medical dressings, disposable medical supplies, mother and baby products and the like, and has the advantages of being good in breathability and moisture penetrability, high in antibacterial capacity, lasting in antibacterial effect, high in mechanical strength, high in cool-feeling coefficient, comfortable to wear and not prone to stuffiness.

Description

Technical Field

[0001] The present application relates to the technical field of plastic films, and more specifically, to a bio-based antibacterial cool breathable film and a preparation method thereof. Background Art

[0002] As people's demand for green environmental protection, health and safety continues to increase, packaging materials, sanitary products, medical protection and other fields have put forward higher requirements on the performance of functional films.

[0003] For example, in the field of medical protection, the films used in protective clothing, dressings, etc. have poor air permeability, which causes the wearer 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 the function of regulating the cooling sensation. In high-temperature environments, they will aggravate the physical discomfort of medical staff. In the field of sanitary products, such as diapers and sanitary napkins, the air permeability is poor, which can easily lead to local moisture and stuffiness. At the same time, the lack of antibacterial ingredients makes it difficult to inhibit bacterial reproduction, which increases the health risks of users. In addition, consumers have an increasing demand for a cool experience of products, hoping to use the characteristics of the materials to bring a cool and comfortable experience.

[0004] Currently, the main methods for preparing antibacterial, cooling breathable membranes include: 1. Blending and modification: Cooling agents and additives such as antimicrobial agents are directly melt-blended with the base resin and then formed by extrusion casting or blown film. This process is simple, low-cost, and suitable for large-scale production. However, the antimicrobial agent easily agglomerates, affecting uniform dispersion, and the cooling agent is susceptible to decomposition during high-temperature processing. 2. Surface coating: A coating containing an antimicrobial agent and a cooling agent is applied to the surface of the breathable membrane. This preserves the permeability of the base membrane and allows for controllable functional layers. However, the coating is susceptible to wear and has poor durability, and the cooling agent (such as menthol) is easily volatilized over time. 3. Electrospinning: Antimicrobial agents and cooling agents are dispersed in a polymer solution and electrospun to form nanofiber membranes. Although nanofiber membranes offer high porosity and excellent air permeability, they are difficult to mass-produce, have low efficiency, and exhibit weak mechanical strength. Furthermore, traditional membranes are often made from petroleum-based polymers (such as polyethylene, polypropylene, and polyurethane), which are difficult to degrade in the natural environment and contribute to "white pollution," which is contrary to global sustainable development concepts. In view of the above-mentioned related technologies, the inventors found that there is an urgent need to provide a bio-based breathable membrane that is antibacterial, has a cool feeling and is strong. Summary of the Invention

[0005] In order to improve wearing comfort and reduce white pollution, the present application provides a bio-based breathable membrane that is highly effective in antibacterial, has a cool feeling, is breathable, and has high strength.

[0006] In a first aspect, the present application provides a bio-based antibacterial cool breathable membrane, which adopts the following technical solution: A bio-based antibacterial cooling breathable film comprises the following raw materials in percentage by weight: 49-66.5% base resin, 30-40% porogen, 1-3% silane-modified cellulose nanofibers, 1-2% antibacterial agent, 1-5% composite cooling agent, and 0.5-1% additive. The matrix resin includes 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.

[0007] By adopting the above technical solution, PBAT and PLA are used as the matrix resin. PBAT resin has good flexibility and ductility, while PLA provides high strength and biodegradability. The blend of the two can balance the mechanical properties and bio-based properties of the membrane, so that the film has good tensile resistance, is completely degradable and environmentally friendly; the porogen can form a through microporous structure in the membrane, directly improving the air permeability of the membrane. The cellulose nanofiber itself has high strength and biocompatibility, but it is easy to agglomerate due to hydrogen bonding, and has strong polarity, which is not conducive to the formation of non- The polar matrix resin has poor compatibility. After silane modification, the surface hydroxyl content is reduced, the interfacial bonding force with the matrix resin and the composite cooling agent is enhanced, agglomeration is reduced, and the tensile strength, modulus and other mechanical properties of the film are improved. At the same time, the nanoscale size of the silane-modified cellulose nanofibers can refine the microporous structure and form a three-dimensional network structure. While improving the mechanical properties of the film, it assists in forming breathable channels to ensure air permeability and avoid the reduction of mechanical properties due to the increase in porosity and air permeability caused by the addition of porogens. The strength loss is compensated by the enhanced network of cellulose nanofibers.

[0008] Nano-aluminum nitride and graphene are used as cooling agents. Nano-aluminum nitride has a high thermal conductivity coefficient and can quickly conduct heat, giving a cool touch. Graphene has extremely high thermal conductivity and works together with nano-aluminum nitride to form a thermal conductivity 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 function can be maintained for a long time, avoiding the problem of traditional chemical cooling factors (such as menthol) becoming ineffective due to volatilization; and both nano-aluminum nitride and graphene have excellent chemical stability. They are not easily decomposed in acidic and alkaline environments, light or temperature changes, and do not react chemically with PBAT and PLA. They can maintain structural integrity for a long time, ensuring that the thermal conductivity function is continuously effective, avoiding the loss of cooling factors and rapid functional attenuation.

[0009] Due to the addition of porogens, a micron-scale porous structure is constructed 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, realizing a "continuous heat dissipation-cooling maintenance" cycle, avoiding the attenuation of cooling sensation caused by the failure of a single heat conduction path.

[0010] Optionally, the composite cooling agent is pre-treated by modification with a silane coupling agent.

[0011] By adopting the above technical solution and using a silane coupling agent to modify nano-aluminum nitride and graphene, the dispersibility of nano-aluminum nitride and graphene can be effectively improved, and they can be evenly dispersed in the film, thereby quickly conducting heat from the surface of the film and avoiding agglomeration and reducing thermal conductivity efficiency.

[0012] Optionally, the raw materials of the silane-modified cellulose nanofibers include cellulose nanofibers and 1-5 wt% of a silane coupling agent.

[0013] By adopting the above technical solution, the silane coupling agent mainly reacts with some hydroxyl groups on the surface of cellulose nanofibers, significantly reducing the surface polarity and reducing the tight stacking between fibers due to hydrogen bonds. At the same time, the organic chain segments of the silane molecules increase the distance between fibers, forming more "through micropores" and improving air permeability. At the same time, the organic chain segments of the silane molecules can act as bridges to enhance the interfacial bonding strength between cellulose nanofibers and the matrix resin, so that the compatibility between cellulose nanofibers and the matrix resin reaches the optimal state.

[0014] Optionally, the silane coupling agent is selected from at least one of KH560, KH550, KH570, vinyltriethoxysilane, phenyltrimethoxysilane and methyltrimethoxysilane.

[0015] 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 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, and reduce the van der Waals force between particles, thereby inhibiting agglomeration and making the particles evenly dispersed in the matrix resin. At the same time, it enhances the interfacial force and improves the mechanical properties and thermal conductivity of the film.

[0016] The surface of cellulose nanofibers is rich in hydroxyl groups. 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. The modified cellulose nanofibers have enhanced hydrophobicity and better compatibility with the matrix resin. The above silane coupling agents can reduce the hydrophilicity of the cellulose nanofiber surface and improve its compatibility with the matrix resin, thereby preventing it from forming agglomerate bundles in the matrix resin. At the same time, it retains the nanoscale reinforcement effect of cellulose nanofibers and improves the mechanical properties and thermal stability of the film.

[0017] Optionally, the raw material of the antibacterial agent comprises chitosan quaternary ammonium salt.

[0018] By adopting the above technical solution, the quaternary ammonium groups on the chitosan quaternary ammonium salt molecular chain are positively charged and can adsorb negatively charged bacterial cell membranes through electrostatic action, destroying the membrane structure and causing leakage of intracellular substances, thereby achieving contact sterilization.

[0019] Optionally, the preparation method of the antibacterial agent is as follows: Chitosan quaternary ammonium salt is added to a PVA solution with a concentration of 8-10wt%, and electrospun to obtain primary fibers. The fibers are then crushed and dispersed in deionized water. A light bactericide is added and mixed uniformly. The fibers are filtered, cross-linked with glutaraldehyde steam at room temperature, and freeze-dried to obtain an antibacterial agent. The mass ratio of polyvinyl alcohol, chitosan quaternary ammonium salt, and light bactericide is 1:0.08-0.1:0.05-0.08.

[0020] By adopting the above technical solution, polyvinyl alcohol is used as a spinning matrix to form a fiber skeleton, which is combined with chitosan quaternary ammonium salt through hydrogen bonds to enhance fiber stability and refine fiber diameter. After the prepared primary fiber is mixed with a light-irradiation bactericidal agent, when cross-linked by glutaraldehyde vapor, the hydroxyl groups of the polyvinyl alcohol react with the amino groups of the chitosan to form a cross-linked network, thereby improving the mechanical strength of the fiber. In addition, the glutaraldehyde vapor cross-linking causes the polyvinyl alcohol and the chitosan quaternary ammonium salt to form a chemical cross-linked network, which cooperates with the formed fiber porous structure to provide a three-dimensional loading space for the chitosan quaternary ammonium salt and the light-irradiation bactericidal agent, reducing direct exposure of the antibacterial component, fixing the light-irradiation bactericidal agent, preventing dissolution, and reducing migration and loss. The fiber porous structure is retained after freeze-drying, the specific surface area is increased, and the interface area between the antibacterial agent and the matrix resin is increased. The contact sterilization of the chitosan quaternary ammonium salt and the light-driven sterilization of the light-irradiation bactericidal agent complement each other. Under lightless conditions, the chitosan quaternary ammonium salt is mainly relied on, and the sterilization efficiency is improved under light.

[0021] Moreover, the electrospun fibers of polyvinyl alcohol and chitosan quaternary ammonium salt themselves have a high aspect ratio and mechanical strength, and can be used as a reinforcing phase in the film. The stress concentration is dispersed through the interface bonding between the fiber and the membrane matrix, thereby improving the tensile strength of the membrane. In particular, the porous structure of the fiber after freeze-drying increases the interface bonding and improves the air permeability of the film. In addition, 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 feeling more lasting.

[0022] Optionally, the light bactericide is prepared by the following method: The bacterial cellulose aqueous dispersion and tannic acid were mixed, stirred at 40-60°C for 10-12 hours, carbon dot powder was added, stirred for 2-4 hours, and vacuum freeze-dried. The mass ratio of bacterial cellulose, tannic acid and carbon dot powder was 5:1-2:2-3.

[0023] By adopting the above technical solution, a large number of phenolic hydroxyl groups are distributed on the surface of tannic acid, which can provide a variety of interactive binding sites, so that tannic acid has a strong bonding ability and can be combined with other molecules through non-covalent interactions such as hydrogen bonds and hydrophobic interactions. The catechol group on the tannic acid molecule is also called a catechol group, which can be combined with various substrates by reversible non-covalent interactions, thereby giving tannic acid good adhesion properties. In addition, the phenolic structure is an excellent hydrogen donor and provides excellent antioxidant properties. The bacterial cellulose molecules are rich in a large number of hydroxyl groups, and the fiber network structure is loose. The hydroxyl groups exposed on the surface can serve as hydrogen bond donors / acceptors. The phenolic hydroxyl groups in tannic acid can bind to bacterial cellulose. The hydroxyl groups of cellulose are combined through hydrogen bonds, so that tannic acid and carbon dots are anchored in the network skeleton of bacterial cellulose to form composite nanoparticles with stable structures. Tannic acid itself is a natural antibacterial agent that can kill or inhibit bacteria by destroying bacterial cell membranes, inhibiting enzyme activity, and chelating metal ions that bacteria must have. Carbon dots have excellent photocatalytic activity and can produce a large amount of reactive oxygen under light, destroying bacterial cell membranes and achieving efficient sterilization. The porous structure of bacterial cellulose can also capture bacteria through physical adsorption, achieving dual physical and chemical sterilization effects. Some tannic acid may produce a small amount of reactive oxygen (ROS) under light, which cooperates with the carbon dot light bactericide to further enhance the photocatalytic bactericidal effect.

[0024] The three-dimensional porous structure of bacterial cellulose provides a carrier for tannic acid and carbon dots, slowing their release rate. The tannic acid, bacterial cellulose, and carbon dot composite transforms the cooling film's antimicrobial effect from instantaneous to long-lasting, sustained-release. The natural antimicrobial properties of tannic acid synergize with chitosan quaternary ammonium salts to broaden the antimicrobial spectrum, making it particularly suitable for skin-contact cooling films (such as cooling dressings and next-to-skin cooling fabrics). Furthermore, the bacterial cellulose fibers form a three-dimensional network through hydrogen bonding, resulting in extremely high mechanical strength and flexibility. Tannic acid acts as a crosslinker, connecting the bacterial cellulose to the matrix resin through hydrogen bonds, reducing interfacial defects, enhancing stress transfer efficiency, and improving the membrane's tensile strength and elongation at break. Furthermore, the porosity of the bacterial cellulose network promotes water and gas exchange between the membrane and outside, improving breathability and water absorption, thereby avoiding discomfort caused by heat and humidity during use. Both tannic acid and bacterial cellulose are natural biomass materials and do not introduce toxic components.

[0025] Optionally, the auxiliary agent is selected from at least one of a chain extender, a lubricant and a plasticizer.

[0026] Optionally, 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 bisstearamide; The plasticizer is selected from at least one of tri-n-butyl citrate, acetyl tri-n-butyl citrate, epoxy soybean oil, triacetin and epoxy fatty acid methyl ester.

[0027] In a second aspect, the present application provides a method for preparing a bio-based antibacterial cool breathable membrane, which adopts the following technical solution: A method for preparing a bio-based antibacterial cool breathable film comprises the following steps: Preparation of silanized cellulose nanofibers: Cellulose nanofibers were dispersed in an ethanol / water mixed solution and ultrasonically treated to form a suspension; adding a silane coupling agent to an ethanol / water mixed solution in an amount of 1-5 wt % relative to the cellulose nanofibers, adjusting the pH to 4-5, stirring until clear, and then adding the mixture to the suspension, stirring at 60-80° C. for 4-6 hours, cooling, centrifuging, washing with ethanol, and vacuum drying or freeze-drying to obtain silanized cellulose nanofibers; Preparation of the composite cooling agent: mixing nano-aluminum nitride and graphene, adding the mixture to a silane coupling agent solution, ultrasonically dispersing the mixture, filtering the mixture, and drying the mixture to obtain the composite cooling agent; Preparation of breathable masterbatch: base resin, porogen, silane-modified cellulose nanofiber, antibacterial agent, composite cooling agent and additives are mixed and melt-extruded to prepare breathable masterbatch; Preparation of breathable film: The breathable masterbatch is dried, hot-melted, and extruded to obtain a melt. The feeding section temperature is 155-165°C, the die section temperature is 165-175°C, and the screw speed is 40-70rpm. The melt is formed into a cast sheet by a casting roller, and then biaxially stretched, cooled and shaped, and wound to obtain a breathable film.

[0028] By adopting the above technical solution, cellulose nanofibers have a reinforcing effect on membrane materials. However, since they are hydrophilic materials themselves, direct melt-mixing and extrusion can easily produce stratification. Therefore, silane is used to modify the cellulose nanofibers, which is beneficial to improving their interfacial compatibility and improving the mechanical strength of the membrane material. At the same time, the addition of porogens can increase the air permeability of the membrane material, accelerate sweat evaporation, keep the skin dry, and avoid stickiness. The cooling factor can produce a cool touch upon contact, relieve stuffiness and discomfort, and the addition of antibacterial agents enables the membrane material to inhibit bacterial growth, reduce odor and cross-infection risks, and bio-based materials are biodegradable, reducing plastic pollution. It has high potential application value in medical dressings, disposable medical supplies, maternal and child products and other fields.

[0029] In summary, this application has the following beneficial effects: 1. Since the present application adopts silane-modified cellulose nanofibers, utilizes nano-aluminum nitride and graphene as composite cooling agents, and adds antibacterial agents and porogens to make a breathable membrane with a microporous structure and antibacterial ability, the mechanical strength, air permeability and moisture permeability and ability to inhibit bacterial growth of the bio-based membrane are improved, and the composite cooling agent can give the breathable membrane a cool touch feeling, reduce the feeling of stuffiness, and improve comfort.

[0030] 2. In the present application, chitosan quaternary ammonium salt is preferably added to a polyvinyl alcohol solution, a light bactericidal agent is added after spinning, and then glutaraldehyde steam is cross-linked to form a chemical cross-linked network between the chitosan quaternary ammonium salt and the polyvinyl alcohol, thereby reducing the dissolution of the light bactericidal agent and improving the antibacterial persistence. Moreover, the fiber formed by the polyvinyl alcohol and the chitosan quaternary ammonium salt can also serve as a reinforcing phase to improve the tensile strength of the film. At the same time, the porous structure formed by freeze drying can also fix the composite cooling agent, making the cooling sensation more lasting.

[0031] 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 light bactericidal agent, achieving dual physical and chemical bactericidal effects, prolonging the bactericidal effect, and increasing mechanical strength and flexibility. DETAILED DESCRIPTION

[0032] The following examples further illustrate the present application in detail.

[0033] Preparation Example I of carbon dot powder: 1.057 g of citric acid, 21.8 ml of silane coupling agent KH-792 and 40 ml of deionized water were mixed, reacted at 200° C. for 6 h, cooled to room temperature, dialyzed and dried.

[0034] Preparation Examples 1-8 of Antibacterial Agents

[0035] Preparation Example 1: 30g of polyvinyl alcohol powder was added to deionized water to obtain a PVA solution with a concentration of 10wt%, 3g of chitosan quaternary ammonium salt was added to the PVA solution, and electrospun to obtain primary fibers. The fibers were pulverized and dispersed in deionized water, and 2.4g of light disinfectant carbon dot powder was added. After mixing, the fibers were filtered, cross-linked with glutaraldehyde steam at room temperature for 24h, and freeze-dried for 24h. The carbon dot powder was prepared by Preparation Example 1, the polyvinyl alcohol was 17-99 type, the chitosan quaternary ammonium salt was selected from Aisen Biotechnology, the article number was ASSW-250324125, the electrospinning speed was 0.5ml / h, the voltage was 20kv, and the receiving distance was 15cm.

[0036] Preparation Example 2: 30g of polyvinyl alcohol powder was added to deionized water to obtain 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. The fibers were pulverized and dispersed into deionized water, 1.5g of light disinfectant carbon point powder was added, mixed, filtered, and cross-linked with glutaraldehyde steam at room temperature for 24h, and freeze-dried for 24h. The carbon point powder was prepared by Preparation Example 1, the polyvinyl alcohol was 17-99 type, the chitosan quaternary ammonium salt was selected from Aisen Biotechnology, the article number was ASSW-250324125, the electrospinning speed was 0.5ml / h, the voltage was 18kv, and the receiving distance was 10cm.

[0037] Preparation Example 3: The difference from Preparation Example 1 is that polyvinyl alcohol is not added. The specific method is as follows: 3 g of chitosan quaternary ammonium salt and 2.4 g of carbon dot powder are evenly mixed to prepare an antibacterial agent.

[0038] Preparation Example 4: The difference from Preparation Example 1 is that the light disinfectant is prepared by the following method: 5 g of bacterial cellulose aqueous dispersion and 2 g of tannic acid are mixed evenly, stirred at 60°C for 10 hours, 3 g of carbon dot powder is added, stirring is continued for 4 hours, and vacuum freeze-dried. 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.

[0039] Preparation Example 5: The difference from Preparation Example 1 is that the light disinfectant is prepared by the following method: 5 g of bacterial cellulose aqueous dispersion and 1 g of tannic acid are mixed evenly, stirred at 40°C for 12 hours, 2 g of carbon dot powder is added, stirring is continued for 2 hours, and vacuum freeze-dried. 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.

[0040] 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, that is, 7 g of bacterial cellulose aqueous dispersion is mixed evenly with 3 g of carbon dot powder, stirred at 60°C for 4 h, and vacuum freeze-dried. 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 according to Preparation Example I.

[0041] Preparation Example 7: The difference from Preparation Example 4 is that an equal amount of tannic acid is used instead of the bacterial cellulose aqueous dispersion, that is, 7 g of tannic acid is evenly mixed with 3 g of carbon dot powder, stirred at 60°C for 4 h, and vacuum freeze-dried. 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 according to Preparation Example I.

[0042] Preparation Example 8: The difference from Preparation Example 4 is that no carbon dot powder is added. 5 g of bacterial cellulose aqueous dispersion and 2 g of tannic acid are evenly mixed, stirred at 60°C for 10 h, and vacuum freeze-dried. The bacterial cellulose aqueous dispersion is selected from Guilin Qihong Technology and has a solid content of 0.8%. Example

[0043] Example 1: A bio-based antibacterial cool breathable film, the raw material usage is shown in Table 1, wherein the base resin comprises PBAT resin and PLA resin in a mass ratio of 7:3, the PBAT resin is selected from Lanshan Tunhe, brand TH801T, the PLA resin is selected from Nature Works of the United States, brand 2003D, the antibacterial agent is chitosan quaternary ammonium salt, the chitosan quaternary ammonium salt is selected from Aisen Biotechnology, product number ASSW-250324125, the composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 6:1, and is pretreated with silane coupling agent KH550, the auxiliary agent comprises a chain extender and a lubricant in a mass ratio of 2:3, the chain extender is BASF ADR4400, and the lubricant is erucamide.

[0044] The preparation method of the above-mentioned bio-based antibacterial cool breathable film comprises the following steps: S1. Preparation of silanized cellulose nanofibers: 1) Disperse 100 g of dry cellulose nanofibers in 2000 g of ethanol / water mixed solvent (volume ratio 8:1) and ultrasonicate at 300 W for 30 min to form a uniform suspension. 2) 30 g of silane coupling agent KH560 was added to an ethanol / water mixture (9:1 volume ratio) at 3 wt% relative to the mass of the cellulose nanofibers. The pH was adjusted to 4 with hydrochloric acid. The mixture was stirred at 40°C for 1 h until the solution became clear, thereby preparing a silane solution. 3) Dissolve the silane and slowly add it to the suspension, heat it to 60°C, stir it continuously for 6 hours, cool it to room temperature, centrifuge it at 8000 rpm for 10 minutes, collect the precipitate, wash it three times with ethanol to remove the unreacted silane coupling agent, and dry it in vacuum at 60°C for 12 hours to obtain silanized cellulose nanofibers; S2. Preparation of composite cooling agent: Nano-aluminum nitride and graphene were mixed in a mass ratio of 6:1, placed in a 3 wt% aqueous solution of a silane coupling agent, ultrasonicated at a power of 300 W for 30 min, filtered, and dried to obtain a surface-modified composite cooling agent; S3. Preparation of breathable masterbatch: The base resin, porogen, silane-modified cellulose nanofiber, antibacterial agent, cooling agent and additives are mixed evenly and hot-melt extruded at 175°C to prepare a breathable masterbatch; S4. Preparation of breathable membrane: The breathable masterbatch was dried at 80 ° C for 12 hours, and then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 160 ° C, the die section temperature was 170 ° C, and the screw speed was 70 rpm. The melt was passed through a casting roller at a temperature of 20 ° C to form a cast sheet. The cast sheet was subjected to two-phase stretching at 110 ° C, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4, and then cooled, shaped, and rolled to obtain a gram weight of 30.5 g / m 2 breathable membrane.

[0045] Table 1 Raw material dosage of bio-based antibacterial cool breathable membrane

[0046] Example 2: A bio-based antibacterial cool breathable film, the raw material usage is shown in Table 1, wherein the base resin comprises PBAT resin and PLA resin in a mass ratio of 5:5, the PBAT resin is selected from Lanshan Tunhe, brand TH801T, the PLA resin is selected from Nature Works of the United States, brand 2003D, the antibacterial agent is chitosan quaternary ammonium salt, the chitosan quaternary ammonium salt is selected from Aisen Biotechnology, product number ASSW-250324125, the composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 10:1, and is pretreated with silane coupling agent KH550, the auxiliary agent comprises a chain extender and a lubricant in a mass ratio of 1:4, the chain extender is BASF ADR4400, and the lubricant is erucamide.

[0047] The preparation method of the above-mentioned bio-based antibacterial cool breathable film comprises the following steps: S1. Preparation of silanized cellulose nanofibers: 1) Disperse 100 g of dry cellulose nanofibers in 2000 g of ethanol / water mixed solvent (volume ratio 8:1) and ultrasonicate at 300 W for 30 min to form a uniform suspension. 2) 30 g of silane coupling agent KH560 was added to an ethanol / water mixture (volume ratio 9:1) at 5 wt% relative to the mass of the cellulose nanofibers. The pH was adjusted to 5 with hydrochloric acid. The mixture was stirred at 40°C for 2 h until the solution became clear, thereby preparing a silane solution. 3) Dissolve silane and slowly add it to the suspension, heat it to 80°C, stir it continuously for 4 hours, cool it to room temperature, centrifuge it at 8000 rpm for 10 minutes, collect the precipitate, wash it three times with ethanol to remove the unreacted silane coupling agent, and dry it in vacuum at 60°C for 12 hours to obtain silanized cellulose nanofibers; S2. Preparation of composite cooling agent: Nano-aluminum nitride and graphene were mixed in a mass ratio of 10:1, placed in a 5 wt% aqueous solution of a silane coupling agent, ultrasonicated at a power of 300 W for 30 min, filtered, and dried to obtain a surface-modified composite cooling agent; S3. Preparation of breathable masterbatch: The base resin, porogen, silane-modified cellulose nanofiber, antibacterial agent, cooling agent and additives are mixed evenly and hot-melt extruded at 165°C to obtain a breathable masterbatch; S4. Preparation of breathable membrane: The breathable masterbatch was dried at 80 ° C for 12 hours, and then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 165 ° C, the die section temperature was 175 ° C, and the screw speed was 60 rpm. The melt was passed through a casting roller at a temperature of 20 ° C to form a cast sheet. The cast sheet was subjected to two-phase stretching at 110 ° C, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4, and then cooled, shaped, and rolled to obtain a 30 g / m 2 breathable membrane.

[0048] Example 3: A bio-based antibacterial cool breathable film, the raw material usage is shown in Table 1, wherein the base resin comprises PBAT resin and PLA resin in a mass ratio of 6:4, the PBAT resin is selected from Lanshan Tunhe, brand TH801T, the PLA resin is selected from Nature Works of the United States, brand 2003D, the antibacterial agent is chitosan quaternary ammonium salt, the chitosan quaternary ammonium salt is selected from Aisen Biotechnology, product number ASSW-250324125, the composite cooling agent comprises nano-aluminum nitride and graphene in a mass ratio of 15:1, and is pretreated with silane coupling agent KH550, the auxiliary agent comprises a chain extender and a lubricant in a mass ratio of 5:5, the chain extender is BASF ADR4400, and the lubricant is erucamide.

[0049] The preparation method of the above-mentioned bio-based antibacterial cool breathable film comprises the following steps: S1. Preparation of silanized cellulose nanofibers: 1) Disperse 100 g of dry cellulose nanofibers in 2000 g of ethanol / water mixed solvent (volume ratio 8:1) and ultrasonicate at 300 W for 30 min to form a uniform suspension. 2) 30 g of silane coupling agent KH560 was added to an ethanol / water mixture (volume ratio 9:1) at 1 wt% relative to the mass of the cellulose nanofibers. The pH was adjusted to 5 with hydrochloric acid. The mixture was stirred at 40°C for 2 h until the solution became clear, thereby preparing a silane solution. 3) Dissolve the silane and slowly add it to the suspension, heat it to 70°C, stir it continuously for 5 hours, cool it to room temperature, centrifuge it at 8000 rpm for 10 minutes, collect the precipitate, wash it three times with ethanol to remove the unreacted silane coupling agent, and dry it in vacuum at 60°C for 12 hours to obtain silanized cellulose nanofibers; S2. Preparation of composite cooling agent: Nano-aluminum nitride and graphene were mixed in a mass ratio of 15:1, placed in a 1 wt% aqueous solution of a silane coupling agent, ultrasonicated at a power of 300 W for 30 min, filtered, and dried to obtain a surface-modified composite cooling agent; S3. Preparation of breathable masterbatch: The base resin, porogen, silane-modified cellulose nanofiber, antibacterial agent, cooling agent and additives are mixed evenly, and hot-melt extruded at 160°C to prepare a breathable masterbatch; S4. Preparation of breathable membrane: The breathable masterbatch was dried at 80 ° C for 12 hours, and then hot-melted and extruded through a screw extruder to obtain a melt. The feeding section temperature was 155 ° C, the die section temperature was 165 ° C, and the screw speed was 40 rpm. The melt was passed through a casting roller at a temperature of 20 ° C to form a cast sheet. The cast sheet was subjected to two-phase stretching at 110 ° C, with a longitudinal stretching ratio of 4 and a transverse stretching ratio of 4. It was then cooled, shaped, and rolled to obtain a gram weight of 30.3 g / m 2 breathable membrane.

[0050] Example 4: A bio-based antibacterial cooling breathable film, which differs from Example 1 in that the composite cooling agent is not pretreated with a silane coupling agent KH550 aqueous solution.

[0051] Example 5: A bio-based antibacterial cool breathable film, 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.

[0052] Example 6: A bio-based antibacterial cool breathable film, which differs from Example 1 in that the antibacterial agent is prepared by Preparation Example 1.

[0053] Example 7: A bio-based antibacterial cool breathable film, which differs from Example 1 in that the antibacterial agent is prepared by Preparation Example 2.

[0054] Example 8: A bio-based antibacterial cool breathable film, which differs from Example 6 in that the antibacterial agent is prepared by Preparation Example 3.

[0055] Example 9: A bio-based antibacterial cool breathable film, which differs from Example 6 in that the antibacterial agent is prepared by Preparation Example 4.

[0056] Example 10: A bio-based antibacterial cool breathable film, which differs from Example 6 in that the antibacterial agent is prepared according to Preparation Example 5.

[0057] Example 11: A bio-based antibacterial cool breathable film, which differs from Example 9 in that the antibacterial agent is prepared by Preparation Example 6.

[0058] Example 12: A bio-based antibacterial cool breathable film, which differs from Example 9 in that the antibacterial agent is prepared by Preparation Example 7.

[0059] Example 13: A bio-based antibacterial cool breathable film, which differs from Example 9 in that the antibacterial agent is prepared by Preparation Example 8.

[0060] Comparative Example Comparative Example 1: A bio-based antibacterial cool 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 is not pretreated with the silane coupling agent KH550.

[0061] Comparative Example 2: A bio-based antibacterial cool breathable membrane, which differs from Example 1 in that cellulose nanofibers are used without being modified with silane.

[0062] Performance testing A bio-based antibacterial cool breathable membrane was prepared according to the methods in the examples and comparative examples, and performance tests were performed according to the following methods. The test results are recorded in Table 2.

[0063] 1. Contact cooling coefficient: Cut a breathable film with a size of 200mm×200mm and adjust the humidity in a constant temperature and humidity chamber for 24 hours according to GB / T6529-2008. The contact cooling coefficient of the breathable film is tested using a KES-F7 contact cooling and heating tester. The test method adopts GB / T35263-2017 "Test and evaluation of the instantaneous cooling performance of textiles". The sample platform temperature is 20±0.5℃, the heat detection plate temperature is 35±0.5℃, and the temperature difference with the sample platform is 15℃. Five positions are selected for each sample for testing, and the average value is taken.

[0064] 2. Breaking strength and elongation: The test is conducted in accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics Part 3: Tests on film and sheeting". The sample size is 150 mm long × 10 mm wide, the initial distance between the clamps is 50 mm, the test speed is 500 mm / min, and the maximum tensile load is measured until the sample breaks, accurate to 0.01 N. The measurement is repeated 5 times and the average value is taken.

[0065] 3. Water vapor transmission rate: Tested in accordance with GB / T 21529-2008 "Plastic film and sheeting water vapor transmission rate test method - electrolytic sensor method", the test temperature is 38 ° C, the test relative humidity is 90%, the sample diameter is 10 cm, and the test area is 63.58 cm 2 .

[0066] 4. Antibacterial rate: Refer to AATCC100-2012 "Evaluation Methods for Antibacterial Textiles" for antibacterial performance evaluation. Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli were selected as test strains. The breathable membrane was cut into uniform circular specimens and placed in a 24-well plate. The absorbance of the bacterial solution was measured using a UV spectrophotometer to ensure that it was within the range of 0.25-0.35. 0.1 ml of bacterial solution was added to the sample and placed under illumination conditions (xenon lamp, wavelength > 420 nm) for 30 minutes and 28 days, respectively. 0.9 mL of PBS was added and shaken. Then, 0.1 ml of the original bacterial solution and the bacterial solution on the sample were diluted in a centrifuge tube in an equal gradient of 1 × 10 6 times (three parallel tests were performed for each sample), 50 μL of each dilution gradient solution was dropped on the culture medium plate, and then placed in a constant temperature incubator at 37°C for 24 h. Finally, the number of colonies in 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 colony count in the original bacterial solution, and N1 is the colony count value of the sample under the corresponding gradient with the original bacterial solution after antibacterial treatment.

[0067] Table 2 Performance test results of bio-based antibacterial cool breathable membrane

[0068] From the comparison of the data in Examples 1-3 and Table 2, it can be seen that the film material made using the raw materials in Examples 1-3 has a higher contact coolness coefficient and moisture permeability, a good contact coolness, and is not prone to stuffiness. At the same time, it has strong breaking strength and elongation at break, high mechanical strength, and strong antibacterial ability.

[0069] In Example 4, the composite cooling agent was not pretreated with silane coupling agent KH550. It can be seen that the breaking strength of the film material prepared in Example 4 is slightly lower than that in Example 1, and the contact cooling coefficient is reduced, indicating that the silane coupling agent pretreatment can improve the compatibility of the composite cooling agent with the matrix resin and increase the dispersibility of the composite cooling agent.

[0070] Compared with Example 1, the amount of silane coupling agent KH560 in the silane-modified cellulose nanofibers is increased. It can be seen that the breaking strength and elongation of the membrane material prepared in Example 5 are slightly decreased, the contact coolness coefficient is reduced, the cool tactile sensation is worse, and the moisture permeability is reduced, indicating that excessive silane coupling agent will cause interface defects or pore blockage, affecting the air permeability of the membrane material.

[0071] Compared with Example 1, Examples 6 and 7 respectively use the antibacterial agents prepared in Preparation Examples 1 and 2 of the present application. Compared with the chitosan quaternary ammonium salt in Example 1, polyvinyl alcohol spinning is also used, and carbon dot powder is added. In addition, glutaraldehyde steam cross-linking is also used. Comparison of the data in Table 2 shows that the antibacterial persistence of the membrane materials prepared in Examples 6 and 7 is enhanced, and the breaking strength is slightly increased, and the moisture permeability is improved. This shows that the antibacterial agent prepared in the present application not only has improved antibacterial ability, but also improved antibacterial persistence, and also increases the moisture permeability and mechanical strength of the membrane material.

[0072] Compared with Example 6, Example 8 uses the antibacterial agent prepared in Preparation Example 3. In Preparation Example 3, no polyvinyl alcohol is added, and no electrospinning is performed. Only chitosan quaternary ammonium salt and carbon dot powder are mixed to prepare the antibacterial agent. It can be seen that the initial antibacterial rate of the prepared membrane material does not change much, but the decrease rate of the 28d antibacterial rate is greater than that of Example 6, the long-term antibacterial effect is weakened, and the breaking strength and elongation of the membrane material are reduced.

[0073] Compared with Example 6, Examples 9 and 10 respectively use the antibacterial agents prepared in Preparation Example 4 and Preparation Example 5. The light bactericides not only contain carbon dot powder, but also contain bacterial cellulose and tannic acid. The data in Table 2 show that the film materials prepared in Examples 9 and 10 have increased breaking strength and elongation, enhanced antibacterial ability, and further improved antibacterial durability.

[0074] In Example 11, the antibacterial agent prepared in Preparation Example 6 was used, and a bacterial cellulose aqueous dispersion was used instead of tannic acid. The antibacterial ability decreased, but the antibacterial rate decreased by a similar amount after 28 days as 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, in which an equal amount of tannic acid was used instead of bacterial cellulose. Table 2 shows that the antibacterial persistence of the membrane material prepared in Example 12 decreased compared with that in Example 9, indicating that the combination of bacterial cellulose and tannic acid can improve the antibacterial ability and antibacterial persistence of the membrane material, and improve the moisture permeability and mechanical strength of the membrane material.

[0075] In Comparative Example 1, the amount of graphene in the composite cooling agent is increased, and the film material prepared without modification by a silane coupling agent has a lower cooling coefficient and a weakened breaking strength, etc., indicating that even if the amount of graphene is increased, the cooling coefficient will not be significantly increased, because excessive graphene will agglomerate in the matrix resin, resulting in rapid local heat loss, and a lack of effective heat conduction paths around the agglomerates, resulting in uneven cooling, and also leading to a decrease in mechanical strength and moisture permeability.

[0076] In Comparative Example 2, silane was not used to modify the cellulose nanofibers. It can be seen that the prepared membrane material has a lower breaking strength and a weaker moisture permeability than that of Example 1, indicating that silane modification can increase the compatibility of cellulose nanofibers with the matrix resin and improve the mechanical strength of the membrane material.

[0077] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A bio-based antibacterial cool breathable membrane, characterized in that: The invention comprises the following raw materials in the following weight percentages: 49-66.5% base resin, 30-40% porogen, 1-3% silane-modified cellulose nanofiber, 1-2% antibacterial agent, 1-5% composite cooling agent, and 0.5-1% auxiliary agent; The matrix resin includes 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 raw materials of the antibacterial agent include chitosan quaternary ammonium salt; The preparation method of the antibacterial agent is as follows: Chitosan quaternary ammonium salt is added to a PVA solution with a concentration of 8-10wt%, and electrospun to obtain primary fibers. The fibers are then crushed and dispersed in deionized water. A light bactericide is added and mixed uniformly. The fibers are filtered, cross-linked with glutaraldehyde steam at room temperature, and freeze-dried to obtain an antibacterial agent. The mass ratio of polyvinyl alcohol, chitosan quaternary ammonium salt, and light bactericide is 1:0.08-0.1:0.05-0.

08.

2. The bio-based antibacterial cool breathable membrane according to claim 1, characterized in that: The composite cooling agent is pre-treated by modification with a silane coupling agent.

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

4. The bio-based antibacterial cool 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 cool breathable membrane according to claim 1, characterized in that: The light bactericide is prepared by the following method: The bacterial cellulose aqueous dispersion and tannic acid were mixed, stirred at 40-60°C for 10-12 hours, carbon dot powder was added, stirred for 2-4 hours, and vacuum freeze-dried. The mass ratio of bacterial cellulose, tannic acid and carbon dot powder was 5:1-2:2-3.

6. The bio-based antibacterial cool breathable membrane according to claim 1, characterized in that: The auxiliary agent is selected from at least one of a chain extender, a lubricant and a plasticizer.

7. The bio-based antibacterial cool 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 bisstearamide; The plasticizer is selected from at least one of tri-n-butyl citrate, acetyl tri-n-butyl citrate, epoxy soybean oil, triacetin and epoxy fatty acid methyl ester.

8. The method for preparing the bio-based antibacterial cool breathable membrane according to any one of claims 1 to 7, characterized in that: The following steps are involved: Preparation of silane-modified cellulose nanofibers: Cellulose nanofibers were dispersed in an ethanol / water mixed solution and ultrasonically treated to form a suspension; adding a silane coupling agent to an ethanol / water mixed solution in an amount of 1-5 wt % relative to the cellulose nanofibers, adjusting the pH to 4-5, stirring until clear, and then adding the mixture to the suspension, stirring at 60-80° C. for 4-6 hours, cooling, centrifuging, washing with ethanol, and vacuum drying or freeze-drying to obtain silanized cellulose nanofibers; Preparation of the composite cooling agent: mixing nano-aluminum nitride and graphene, adding the mixture to a silane coupling agent solution, ultrasonically dispersing the mixture, filtering the mixture, and drying the mixture to obtain the composite cooling agent; Preparation of breathable masterbatch: base resin, porogen, silane-modified cellulose nanofiber, antibacterial agent, composite cooling agent and additives are mixed and melt-extruded to prepare breathable masterbatch; Preparation of breathable film: The breathable masterbatch is dried, hot-melted, and extruded to obtain a melt. The feeding section temperature is 155-165°C, the die section temperature is 165-175°C, and the screw speed is 40-70rpm. The melt is formed into a cast sheet by a casting roller, and then biaxially stretched, cooled and shaped, and wound to obtain a breathable film.

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