A light-proof aseptic packaging bag and its preparation method

Abstract

This invention belongs to the field of packaging bag composite material technology, and particularly relates to a light-proof aseptic packaging bag and its preparation method. From the outside to the inside, it comprises a base layer, a light-proof layer, an antibacterial layer, and a heat-sealing layer. A β-CD-Humulus lucidum / MOF-thymol complex is introduced as an antibacterial agent. By combining hummus carbon dots with β-cyclodextrin and thymol with MOF, the slow release of antibacterial substances from hummus and thymol can be achieved, resulting in a stable and long-lasting antibacterial effect.

Description

Technical Field

[0001] This invention belongs to the field of packaging bag composite material technology, specifically relating to a light-proof aseptic packaging bag and its preparation method. Background Technology

[0002] Early packaging bags had a relatively simple function, primarily focusing on wrapping and containing goods. With the gradual advancement of industrial technology, the requirements for packaging expanded from basic containment to include product protection and preservation. To prevent food from being contaminated by microorganisms during transportation and storage, methods such as high-temperature sterilization, ultraviolet disinfection, and chemical preservation were initially used, followed by the emergence of new aseptic packaging materials. As people's awareness of food safety and environmental protection has increased, aseptic packaging bags are moving towards greater efficiency and environmental friendliness. Chinese patent CN 118755242B discloses an anti-mold and fresh-keeping packaging bag and its preparation method. It uses PBAT material as the main substrate of the packaging bag and adds an anti-mold and antibacterial agent containing guanidine and halogenated amine structures. Combined with chitosan oligosaccharide as an antibacterial material, it further enhances the breadth and strength of antibacterial activity, effectively preventing premature degradation of PBAT by bacteria and thus reducing the mechanical properties of the product. Chinese patent CN 119305277B discloses a high-barrier antibacterial flexible packaging material and its preparation method. It consists of an outer layer, a barrier antibacterial layer, and an inner heat-sealing layer, arranged sequentially from the outside in. It adds amine organic molecular cage composite nano-silver as an antibacterial modifier, effectively preventing the growth of microorganisms in humid environments and improving the antibacterial performance of the flexible packaging material. However, how to achieve a stable and long-lasting antibacterial effect in the packaging bag still requires further research. Summary of the Invention

[0003] To address at least one of the above problems, the present invention provides a method for preparing a light-proof aseptic packaging bag, comprising the following steps:

[0004] S100: A base layer is prepared using raw materials including maleic anhydride-grafted polyethylene and polyethylene.

[0005] S200, using raw materials including carbon black and polyethylene terephthalate, a light-shielding layer is prepared;

[0006] S300 uses raw materials including β-cyclodextrin-hope compound, MOF-thymol compound, maleic anhydride-grafted polyethylene, and polyethylene to prepare an antibacterial layer.

[0007] S400: A heat-sealing layer is prepared using raw materials including ethylene-vinyl acetate copolymer.

[0008] S500: The base layer and the light-shielding layer are combined to obtain a base layer / light-shielding layer composite layer; the antibacterial layer and the heat-sealing layer are combined to obtain an antibacterial layer / heat-sealing layer composite layer; and the base layer / light-shielding layer composite layer and the antibacterial layer / heat-sealing layer composite layer are combined to obtain the light-shielding aseptic packaging bag.

[0009] Further, step S100 specifically includes: mixing polyethylene and maleic anhydride-grafted polyethylene in a certain proportion, and then melting and extruding them into a film using an extruder to obtain the base layer.

[0010] Further, step S200 specifically includes: mixing polyethylene terephthalate and carbon black in a certain proportion, adding a silane coupling agent, melting and extruding to form a film, and then activating the surface by ultraviolet irradiation to obtain a light-shielding layer.

[0011] Furthermore, step S300 specifically includes:

[0012] S310. Add β-cyclodextrin to deionized water and stir until completely dissolved to obtain a β-cyclodextrin solution. Then add hop carbon dots to the solution, stir evenly, and sonicate to obtain a mixture. Centrifuge to collect the supernatant, freeze-dry to obtain a β-cyclodextrin-hop complex.

[0013] S320. MOF powder is added to anhydrous ethanol and dispersed evenly to obtain MOF dispersion. Thymol mixture is added dropwise to it, stirred at room temperature and allowed to stand. The precipitate is collected by centrifugation, washed and dried to obtain MOF-thymol complex.

[0014] S330. The β-cyclodextrin-Humulus complex was dissolved in deionized water and dispersed evenly to obtain a β-cyclodextrin-Humulus complex dispersion. The MOF-thymol complex was dissolved in anhydrous ethanol and dispersed evenly to obtain a MOF-thymol complex dispersion. The MOF-thymol complex dispersion was added dropwise to the β-cyclodextrin-Humulus complex dispersion. After stirring at room temperature, the precipitate was collected by centrifugation, washed, and dried to obtain the β-CD-Humulus / MOF-thymol complex.

[0015] S340: β-CD-Humulus / MOF-thymol complex, polyethylene, and maleic anhydride-grafted polyethylene are mixed in a certain proportion and then melt-extruded into a film using a twin-screw extruder to obtain an antibacterial layer.

[0016] Further, the preparation method of hop carbon dots in step S310 is as follows: hop is wrapped in aluminum foil and placed in a sealed environment, and calcined at high temperature to obtain carbonized hop. It is then dissolved in deionized water and boiled. The resulting solution is filtered through a filter membrane to remove the precipitate and obtain a solution containing hop carbon dots. After concentration and freeze-drying, a solid powder is obtained, which is the hop carbon dots.

[0017] Further, the preparation method of MOF powder in step S320 is as follows: add zirconium nitrate and terephthalic acid to N,N-dimethylformamide, stir until completely dissolved, then add concentrated hydrochloric acid, transfer to a reaction vessel, react at high temperature, cool to room temperature, collect the precipitate by centrifugation, and obtain MOF powder after washing, soaking and drying.

[0018] Further, step S400 specifically includes: adding ethylene-vinyl acetate copolymer, maleic anhydride, and crosslinking agent to an extruder, melting and extruding the mixture into a film, and then treating it with plasma to obtain a heat-sealing layer.

[0019] Furthermore, step S500 specifically includes:

[0020] S510. Apply polyurethane adhesive between the base layer and the light-shielding layer, dry it, and then press it with a roller to obtain a base layer / light-shielding layer composite layer.

[0021] S520. The antibacterial layer and the heat-sealing layer are combined by a composite roller to obtain an antibacterial layer / heat-sealing layer composite layer.

[0022] S530. Apply polyurethane adhesive between the base layer / light-shielding layer composite layer and the antibacterial layer / heat-sealing layer composite layer, dry, and then press and roll to obtain the packaging bag.

[0023] A light-proof aseptic packaging bag is prepared using the method for preparing a light-proof aseptic packaging bag as described in any of the above technical solutions.

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

[0025] In the preparation of the base layer, maleic anhydride-grafted polyethylene was introduced, which enhances the entanglement of polyethylene molecular chains through intermolecular forces, reduces molecular chain slippage, and improves the mechanical properties of the base layer. During the preparation of the light-shielding layer, ultraviolet irradiation introduced polar active groups onto the surface and simultaneously formed a micro-rough structure, increasing interfacial bonding. In the preparation of the antibacterial layer, a β-CD-hummus / MOF-thymol complex was introduced as an antibacterial material. By combining hummus carbon dots with β-cyclodextrin and thymol with MOF, the slow release of antibacterial substances from hummus and thymol can be achieved, resulting in a stable and long-lasting antibacterial effect. In the preparation of the heat-sealing layer, plasma treatment introduced oxygen-containing functional groups onto its surface, effectively enhancing the interfacial bonding strength. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0027] Food production and consumption are asymmetrical in terms of time and space. Transportation can meet the needs of consumers in different regions, but food spoilage can occur during transportation and storage. Therefore, how to prevent food spoilage during transportation and storage is a common problem. Studies have shown that microbial contamination is a major cause of food spoilage. Traditional packaging bags mostly use chemical antibacterial agents (such as silver ions) and physical composite processes, which have issues with biosafety and insufficient interlayer bonding. While natural plant essential oils are FDA-approved safe antibacterial agents, their application is limited by their volatility and poor stability. Based on this, the present invention provides a method for preparing a light-proof aseptic packaging bag, including the following steps:

[0028] S100: A base layer is prepared using raw materials including maleic anhydride-grafted polyethylene and polyethylene.

[0029] S200, using raw materials including carbon black and polyethylene terephthalate, a light-shielding layer is prepared;

[0030] S300 uses raw materials including β-cyclodextrin-hope compound, MOF-thymol compound, maleic anhydride-grafted polyethylene, and polyethylene to prepare an antibacterial layer.

[0031] S400: A heat-sealing layer is prepared using raw materials including ethylene-vinyl acetate copolymer.

[0032] S500: The base layer and the light-shielding layer are combined to obtain a base layer / light-shielding layer composite layer; the antibacterial layer and the heat-sealing layer are combined to obtain an antibacterial layer / heat-sealing layer composite layer; and the base layer / light-shielding layer composite layer and the antibacterial layer / heat-sealing layer composite layer are combined to obtain the light-shielding aseptic packaging bag.

[0033] The packaging bag consists of, from the outside in, a base layer, a light-proof layer, an antibacterial layer, and a heat-sealing layer.

[0034] Step S100 specifically includes: mixing polyethylene and maleic anhydride-grafted polyethylene in a certain proportion, melting and extruding the mixture through an extruder, and casting it into a film to obtain the base layer. The mass ratio of polyethylene to maleic anhydride-grafted polyethylene is 70-100:8-12; the heating zone temperature of the twin-screw extruder is 160-180℃, and the screw speed is 150-200 rpm; the heating temperature of the casting machine is 40-60℃.

[0035] In this process, the molecular chains of polyethylene are only bound by weak van der Waals forces, resulting in relatively poor mechanical properties. Maleic anhydride-grafted polyethylene, by introducing maleic anhydride groups through grafting, can enhance the entanglement of polyethylene molecular chains through intermolecular forces, forming a partially compatible network with polyethylene, reducing molecular chain slippage, and thus improving the mechanical properties of the base layer. In addition, polyethylene is a non-polar polymer, and the interfacial forces with the polar material polyethylene terephthalate in the light-shielding layer are weak, making it prone to delamination. However, the polar maleic anhydride groups introduced through grafting can interact with the ester groups and hydroxyl groups on polyethylene terephthalate, providing a basis for subsequent composite with the light-shielding layer. At the same time, the grafting structure of maleic anhydride-grafted polyethylene can adjust the fluidity of the polyethylene melt, making the melt viscosity more stable and improving the film quality.

[0036] Step S200 specifically includes: mixing polyethylene terephthalate and carbon black in a certain proportion, adding a silane coupling agent, melt-extruding to form a film, and then activating the surface by ultraviolet irradiation to obtain a light-shielding layer. The mass ratio of polyethylene terephthalate, carbon black, and silane coupling agent is 90-100:8-12:4.7-5.5; the ultraviolet irradiation conditions are: wavelength 254nm, power 30W, treatment time 20-30s; the heating zone temperature of the twin-screw extruder is 260-280℃, and the screw speed is 250-350rpm; the heating temperature of the casting machine is 80-100℃.

[0037] In the above steps, carbon black and polyethylene terephthalate (PET) have poor compatibility. Therefore, a silane coupling agent is added to improve the dispersibility of carbon black in the PET melt. Irradiating the surface of the light-shielding layer with ultraviolet light introduces polar active groups onto the surface, while simultaneously causing slight degradation to form a micro-rough structure, providing an interfacial basis for subsequent composite processes.

[0038] Step S300 specifically includes:

[0039] S310. Add β-cyclodextrin to deionized water and stir until completely dissolved to obtain a β-cyclodextrin solution. Then add hop carbon dots to the solution, stir evenly, and sonicate to obtain a mixture. Centrifuge to collect the supernatant, freeze-dry to obtain a β-cyclodextrin-hop complex.

[0040] In this step, hops contain abundant flavonoids, which can induce bacteria to produce excessive reactive oxygen species, damaging biomolecules such as DNA and proteins, and accelerating cell apoptosis. In this invention, hops carbon dots were prepared using a hydrothermal method. During carbonization, the flavonoids, phenols, and other oxygen-rich components in hops retain a large number of polar functional groups on the surface of the carbon dots, while the core has a certain degree of hydrophobicity due to its carbon skeleton. However, because hops carbon dots are highly water-soluble, they are easily and rapidly dissolved in humid environments in contact with food, leading to a decrease in antibacterial activity in the short term and an inability to maintain long-term efficacy. β-Cyclodextrin is a cyclic oligosaccharide with a cavity that is hydrophilic on the outside and hydrophobic on the inside. The hydrophobic core of hops carbon dots can enter the hydrophobic cavity of β-cyclodextrin, forming a host-guest inclusion complex; the hydroxyl and carboxyl groups on the surface of hops carbon dots can form hydrogen bonds with the hydroxyl groups on the surface of β-cyclodextrin, further stabilizing the complex. The hydrophobic cavities of β-cyclodextrin regulate the "encapsulation-release" of hop carbon dots. In a dry state, the hop carbon dots are stably encapsulated within the β-cyclodextrin cavities. When the packaging comes into contact with food juices, water molecules permeate, causing the β-cyclodextrin conformation to loosen and slowly release the hop carbon dots, thus maintaining their antibacterial effect. The large molecular backbone of β-cyclodextrin encapsulates the hop carbon dots, forming a larger complex and reducing aggregation. Furthermore, the high thermal stability of β-cyclodextrin protects hops from damage during high-temperature processing.

[0041] S320. MOF powder is added to anhydrous ethanol and dispersed evenly to obtain MOF dispersion. Thymol mixture is added dropwise to it, stirred at room temperature and allowed to stand. The precipitate is collected by centrifugation, washed and dried to obtain MOF-thymol complex. The thymol mixture is prepared by dissolving thymol in anhydrous ethanol.

[0042] In this step, thymol, a monoterpene phenol, binds its phenolic hydroxyl groups to lipids in the phospholipid bilayer of the cell membrane, altering membrane fluidity and permeability, leading to leakage of intracellular electrolytes, proteins, and other substances. It also induces bacterial death by binding to the active sites of key bacterial metabolic enzymes, thus exerting an antibacterial effect. When combined with hops, thymol binds to cell membrane lipids through its phenolic hydroxyl groups, disrupting membrane fluidity. The antibacterial substances contained in the carbon dots of hops inhibit membrane lipid synthesis, blocking membrane repair and renewal. The combined effect dramatically increases cell membrane permeability, accelerating bacterial death. Thymol is effective against Gram-positive, Gram-negative bacteria, and fungi, with hops exhibiting stronger activity against Gram-positive bacteria; the combination broadens the antibacterial spectrum. However, thymol is highly volatile and easily lost during processing and storage, leading to a short-term decline in antibacterial activity, which cannot meet the requirements for long-term food preservation. Therefore, in this invention, thymol is compounded with MOF (Medium-Oxygen Fragrance). MOFs have regular nanopores, which can stably load thymol into the pores through physical adsorption or hydrogen bonding, reducing its volatilization rate. At the same time, thymol is a hydrophobic oily substance with poor compatibility with polymers. The particulate structure of MOFs can be uniformly dispersed in polymers, avoiding phase separation caused by the aggregation of thymol in the oil phase, thus ensuring the mechanical properties of the film.

[0043] S330. The β-cyclodextrin-Humulus complex was dissolved in deionized water and dispersed evenly to obtain a β-cyclodextrin-Humulus complex dispersion. The MOF-thymol complex was dissolved in anhydrous ethanol and dispersed evenly to obtain a MOF-thymol complex dispersion. The MOF-thymol complex dispersion was added dropwise to the β-cyclodextrin-Humulus complex dispersion. After stirring at room temperature, the precipitate was collected by centrifugation, washed, and dried to obtain the β-CD-Humulus / MOF-thymol complex.

[0044] In this step, the β-CD-Humulus complex and the MOF-thymol complex are prone to agglomeration when the polymer melts due to differences in their surface properties. By binding the β-CD-Humulus complex and the MOF-thymol complex together through coordination bonds, secondary agglomeration during mixing can be avoided, thereby improving their dispersibility in the polymer matrix.

[0045] S340: β-CD-Humulus / MOF-thymol complex, polyethylene, and maleic anhydride-grafted polyethylene are mixed in a certain proportion and then melt-extruded through a twin-screw extruder to form an antibacterial layer. The mass ratio of β-CD-Humulus / MOF-thymol complex, polyethylene, and maleic anhydride-grafted polyethylene is 8-12:75-85:8-12; the heating zone temperature of the twin-screw extruder is 170-190℃, and the screw speed is 350-450 rpm; the heating temperature of the casting machine is 50-70℃.

[0046] The preparation method of hop carbon dots in step S310 is as follows: fresh and cleaned hops are wrapped in aluminum foil and placed in a sealed environment. They are then calcined at high temperature to obtain carbonized hops. The carbonized hops are then dissolved in deionized water and boiled. The resulting solution is filtered through a filter membrane to remove the precipitate and obtain a solution containing hop carbon dots. After concentration and freeze-drying, a solid powder is obtained, which is the hop carbon dots.

[0047] The preparation method of MOF powder in step S320 is as follows: zirconium nitrate and terephthalic acid are added to N,N-dimethylformamide and stirred until completely dissolved. Then concentrated hydrochloric acid is added to it, and the mixture is transferred to a reaction vessel. After high-temperature reaction, it is cooled to room temperature, centrifuged to collect the precipitate, and after washing, soaking and drying, MOF powder is obtained.

[0048] Step S400 specifically includes: adding ethylene-vinyl acetate copolymer, maleic anhydride, and crosslinking agent to an extruder, melting and extruding the mixture, casting it into a film, and then treating it with plasma to obtain a heat-sealing layer. The crosslinking agent is one or a mixture of several of the following: dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, diphenylmethane diisocyanate, toluene diisocyanate, and vinyltriethoxysilane; the mass ratio of ethylene-vinyl acetate copolymer, maleic anhydride, and crosslinking agent is 90-100:4-8:1-3; the heating zone temperature of the twin-screw extruder is 140-160℃, and the screw speed is 200-300 rpm; the heating temperature of the casting machine is 40-60℃; the plasma treatment conditions are: oxygen atmosphere, power 30-60W, and treatment time 40-80s.

[0049] Step S500 specifically includes:

[0050] S510. Apply polyurethane adhesive to the substrate surface using an adhesive applicator, controlling the adhesive application rate to 4-5 g / m². 2 Dry at 50-70℃ for 30-40 seconds, then laminate with the light-shielding layer at the pressure roller. The pressure roller temperature is 55-65℃ and the pressure is 0.3-0.4MPa. The laminated film is then wound up to obtain the base layer / light-shielding layer composite layer.

[0051] In this process, the solvent in the adhesive is evaporated by drying, while the isocyanate groups react with the maleic anhydride groups of the base layer to form covalent bonds. Then, pressure is applied to bring the two layers into close contact, further promoting the interaction between the interfaces and forming a stable bond.

[0052] S520. Use an extruder to melt polyethylene resin, and extrude the molten polyethylene as a film onto the surface of the antibacterial layer through a die as an adhesive layer with a thickness of 3-5μm. Then, the heat-sealing layer is plasma-treated and coated with the antibacterial layer at a composite roller. The temperature of the composite roller is 75-85℃ and the pressure is 0.2-0.3MPa. The composite film is then wound up to obtain the antibacterial layer / heat-sealing layer composite layer.

[0053] During this process, the ester groups in the ethylene-vinyl acetate copolymer form coordination bonds with the MOF material, and the molten polyethylene adhesive layer promotes the bonding between the antibacterial layer and the heat-sealing layer, making the bond between the two stronger.

[0054] S530. Apply polyurethane adhesive to the surface of the base layer / light-shielding layer composite layer using an adhesive applicator, controlling the adhesive application amount to 3-4 g / m². 2 The film is dried at 50-70℃ for 30-40 seconds, and then laminated with the antibacterial layer / heat-sealing layer composite layer at the pressure roller. The pressure roller temperature is 60-70℃ and the pressure is 0.3-0.4MPa. The laminated film is then wound up and bagged to obtain the packaging bag. The heat-sealing temperature is 130-140℃, the pressure is 0.3-0.4MPa, and the time is 1-3 seconds.

[0055] The polyethylene (model BE0400) used in this invention was purchased from Suzhou Fengjuan Plastic Raw Materials Co., Ltd., and the maleic anhydride grafting rate in the maleic anhydride-grafted polyethylene was 1.2%-1.5%. The carbon black was commercially available industrial grade. The polyethylene terephthalate (model 543-LBK) was purchased from Dongguan Baojia Plastics Co., Ltd., and the VA content in the ethylene-vinyl acetate copolymer was 15%-20%. The polyurethane adhesive contained 2.5% NCO groups. The β-cyclodextrin (model C104384) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0056] Example 1

[0057] A method for preparing a light-proof aseptic packaging bag includes the following steps:

[0058] S1. Mix 85 parts by weight of polyethylene and 10 parts by weight of maleic anhydride-grafted polyethylene, then melt-extrude the mixture through a twin-screw extruder and cast it into a film to obtain the base layer. The heating zone temperature of the twin-screw extruder is 160-180℃, and the screw speed is 180rpm. The heating temperature of the casting machine is 50℃.

[0059] S2. Mix 95 parts by weight of polyethylene terephthalate with 10 parts by weight of carbon black, then add 5.2 parts by weight of KH550. After melt extrusion to form a film, the surface is activated by ultraviolet irradiation to obtain a light-shielding layer. The ultraviolet irradiation conditions are: wavelength 254nm, power 30W, treatment for 30s, heating zone temperature of twin-screw extruder 260-280℃, screw speed 300rpm; casting machine heating temperature 90℃.

[0060] S3. Wrap 100 parts by weight of hops in aluminum foil and place them in a crucible. Cover the crucible to form a sealed environment and calcine it in a muffle furnace at 320°C for 2 hours. Then, dissolve it completely in 150 parts by weight of deionized water and boil it twice, 2 hours each time. Filter the resulting solution through a filter membrane (0.45μm, 0.22μm) to remove the precipitate and obtain a solution containing hops carbon dots. Concentrate and freeze-dry it into a solid powder to obtain hops carbon dots.

[0061] S4. Add 10 parts by weight of β-cyclodextrin to 150 parts by weight of deionized water and stir until completely dissolved to obtain a β-cyclodextrin solution. Then add 2 parts by weight of hop carbon dots to the solution, stir evenly, and sonicate at 300W for 30 min. Then stir at 40℃ for 24 h to obtain a mixture. Centrifuge at 4000rpm for 10 min, take the supernatant, freeze dry to obtain the β-cyclodextrin-hop complex.

[0062] S5. Add 10 parts by weight of zirconium nitrate and 5 parts by weight of terephthalic acid to 120 parts by weight of N,N-dimethylformamide, stir until completely dissolved, add 0.8 parts by weight of concentrated hydrochloric acid, transfer to a reaction vessel, react at 120℃ for 24 h, cool to room temperature, collect the precipitate by centrifugation at 5000 rpm for 10 min, wash 3 times with N,N-dimethylformamide, soak in methanol for 24 h, and then dry in a vacuum drying oven at 50℃ for 12 h to obtain MOF powder;

[0063] S6. Add 6 parts by weight of MOF powder to 60 parts by weight of anhydrous ethanol, and disperse by ultrasonication for 10 min to obtain MOF dispersion; add 2 parts by weight of thymol to 10 parts by weight of anhydrous ethanol, and mix evenly to obtain thymol mixture; add the thymol mixture dropwise to MOF dispersion, stir at room temperature for 24 h, centrifuge at 2000 rpm for 10 min, collect the precipitate, wash twice with anhydrous ethanol, and dry in a vacuum drying oven at 40℃ for 8 h to obtain MOF-thymol complex.

[0064] S7. Dissolve 8 parts by weight of β-cyclodextrin-Humulus complex in 80 parts by weight of deionized water and disperse evenly to obtain β-cyclodextrin-Humulus complex dispersion. Dissolve 8 parts by weight of MOF-thymol complex in 80 parts by weight of anhydrous ethanol and disperse evenly to obtain MOF-thymol complex dispersion. Add MOF-thymol complex dispersion dropwise to β-cyclodextrin-Humulus complex dispersion, stir at room temperature for 4 h, centrifuge at 2000 rpm for 15 min, collect the precipitate, wash twice with 50% ethanol aqueous solution, and dry in a vacuum drying oven at 50℃ for 12 h to obtain β-CD-Humulus / MOF-thymol complex.

[0065] S6. Mix 10 parts by weight of β-CD-Humulus / MOF-thymol complex, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melt-extrude the mixture using a twin-screw extruder to form an antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, and the screw speed is 400rpm. The heating temperature of the casting machine is 60℃.

[0066] S7. Add 90 parts by weight of ethylene-vinyl acetate copolymer, 6 parts by weight of maleic anhydride, and 2 parts by weight of dicumyl peroxide to an extruder. Melt extrusion is performed in the extruder, followed by casting to form a film. The film is then treated with plasma to obtain a heat-sealing layer. The heating zone temperature of the twin-screw extruder is 140-160℃, and the screw speed is 250rpm. The heating temperature of the casting machine is 50℃. The plasma treatment conditions are: oxygen atmosphere, power 40W, and treatment time 60s.

[0067] S8. Apply polyurethane adhesive to the substrate surface using an adhesive applicator, controlling the adhesive application rate to 4.5 g / m². 2 The film is dried at 60℃ for 40 seconds and then laminated with the light-shielding layer at the pressure roller. The pressure roller temperature is 60℃ and the pressure is 0.4MPa. The laminated film is then wound up to obtain the base layer / light-shielding layer composite layer.

[0068] S9. Use an extruder to melt polyethylene resin, and extrude the molten polyethylene as a film onto the surface of the antibacterial layer as an adhesive layer through a die. The thickness is controlled to be 4μm. Then, the heat-sealing layer is plasma-treated and coated with the antibacterial layer at a composite roller. The temperature of the composite roller is 80℃ and the pressure is 0.3MPa. The composite film is then wound up to obtain the antibacterial layer / heat-sealing layer composite layer.

[0069] S10. Apply polyurethane adhesive to the surface of the base layer / light-shielding layer composite layer using an adhesive applicator, controlling the adhesive application amount to 3.5 g / m². 2The film is dried at 60°C for 40 seconds, and then laminated with the antibacterial / heat-sealing composite layer at the pressure roller. The pressure roller temperature is 65°C and the pressure is 0.4MPa. The laminated film is then wound up and bagged to obtain the packaging bag. The heat-sealing temperature is 130°C, the pressure is 0.4MPa, and the time is 2 seconds.

[0070] Example 2

[0071] This embodiment differs from Embodiment 1 in the following ways:

[0072] In step S1, by weight, there are 70 parts of polyethylene and 8 parts of maleic anhydride-grafted polyethylene; in step S2, there are 90 parts of polyethylene terephthalate, 8 parts of carbon black, and 4.7 parts of silane coupling agent; in step S8, there are 8 parts of β-CD-Humulus / MOF-thymol complex, 75 parts of polyethylene, and 8 parts of maleic anhydride-grafted polyethylene; in step S9, there are 90 parts of ethylene-vinyl acetate copolymer, 4 parts of maleic anhydride, and 1 part of crosslinking agent.

[0073] Example 3

[0074] This embodiment differs from Embodiment 1 in the following ways:

[0075] In step S1, by weight, there are 100 parts of polyethylene and 12 parts of maleic anhydride-grafted polyethylene; in step S2, there are 100 parts of polyethylene terephthalate, 12 parts of carbon black, and 5.5 parts of silane coupling agent; in step S8, there are 12 parts of β-CD-Humulus / MOF-thymol complex, 85 parts of polyethylene, and 12 parts of maleic anhydride-grafted polyethylene; in step S9, there are 100 parts of ethylene-vinyl acetate copolymer, 8 parts of maleic anhydride, and 3 parts of crosslinking agent.

[0076] Example 4

[0077] This embodiment differs from Embodiment 1 in the following ways:

[0078] In step S1, by weight, there are 78 parts of polyethylene and 9 parts of maleic anhydride-grafted polyethylene; in step S2, there are 92 parts of polyethylene terephthalate, 8.5 parts of carbon black, and 4.9 parts of silane coupling agent; in step S8, there are 9 parts of β-CD-hummus / MOF-thymol complex, 78 parts of polyethylene, and 9 parts of maleic anhydride-grafted polyethylene; in step S9, there are 92 parts of ethylene-vinyl acetate copolymer, 5 parts of maleic anhydride, and 1.6 parts of crosslinking agent.

[0079] Example 5

[0080] Compared with Example 1, this embodiment differs in the following way: when preparing the antibacterial layer, the β-cyclodextrin-Humulus complex is replaced with Humulus carbon dots, specifically:

[0081] The antibacterial layer is prepared by mixing 5 parts by weight of hop carbon dots, 5 parts by weight of MOF-thymol complex, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melting and extruding the mixture into a film using a twin-screw extruder to obtain the antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, and the screw speed is 400rpm. The heating temperature of the casting machine is 60℃.

[0082] Example 6

[0083] Compared with Example 1, this embodiment differs in the following way: when preparing the antibacterial layer, the MOF-thymol complex is replaced with thymol, specifically:

[0084] The antibacterial layer is prepared as follows: 5 parts by weight of β-CD-Humulus complex, 5 parts by weight of thymol, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene are mixed and then melt-extruded into a film using a twin-screw extruder to obtain the antibacterial layer; the heating zone temperature of the twin-screw extruder is 170-190℃, the screw speed is 400rpm, and the heating temperature of the casting machine is 60℃.

[0085] Comparative Example 1

[0086] Compared with Example 1, this comparative example differs in the following way: when preparing the antibacterial layer, the β-CD-Humulus / MOF-thymol complex was replaced with the β-CD-Humulus complex, specifically:

[0087] The antibacterial layer is prepared by mixing 10 parts by weight of β-CD-Humulus complex, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melting and extruding the mixture into a film using a twin-screw extruder to obtain the antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, and the screw speed is 400rpm. The heating temperature of the casting machine is 60℃.

[0088] Comparative Example 2

[0089] Compared with Example 1, this comparative example differs in the following way: when preparing the antibacterial layer, the β-CD-Humulus / MOF-thymol complex was replaced with the MOF-thymol complex, specifically:

[0090] The antibacterial layer is prepared by mixing 10 parts by weight of MOF-thymol complex, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melting and extruding the mixture into a film using a twin-screw extruder to obtain the antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, and the screw speed is 400rpm. The heating temperature of the casting machine is 60℃.

[0091] Comparative Example 3

[0092] This comparative example differs from Example 1 in the following way: when preparing the antibacterial layer, the β-CD-Humulus / MOF-thymol complex is replaced with hummus and thymol, specifically:

[0093] The antibacterial layer is prepared by mixing 5 parts by weight of hop carbon dots, 5 parts by weight of thymol, 80 parts by weight of polyethylene, and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melting and extruding the mixture through a twin-screw extruder to form a film to obtain the antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, the screw speed is 400rpm, and the heating temperature of the casting machine is 60℃.

[0094] Comparative Example 4

[0095] Compared with Example 1, this comparative example differs in the following specific ways:

[0096] During the preparation of the light-shielding layer, it is not subjected to ultraviolet irradiation treatment. Specifically, 95 parts by weight of polyethylene terephthalate and 10 parts by weight of carbon black are mixed and then 5.2 parts by weight of KH550 are added. The mixture is melt-extruded to form a film to obtain the light-shielding layer. The heating zone temperature of the twin-screw extruder is 260-280℃ and the screw speed is 300rpm. The heating temperature of the casting machine is 90℃.

[0097] In the preparation of the heat-sealing layer, no plasma treatment is performed. Specifically, 95 parts by weight of ethylene-vinyl acetate copolymer, 6 parts by weight of maleic anhydride, and 2 parts by weight of dicumyl peroxide are added to an extruder, and the mixture is melt-extruded and cast into a film. The heating zone temperature of the twin-screw extruder is 140-160℃, and the screw speed is 250rpm. The heating temperature of the casting machine is 50℃. The plasma treatment conditions are: oxygen atmosphere, power 40W, and treatment time 60s.

[0098] Comparative Example 5

[0099] This comparative example differs from Example 1 in the following ways:

[0100] In the preparation of the base layer, maleic anhydride-grafted polyethylene is not added. Specifically, 100 parts by weight of polyethylene are melt-extruded by a twin-screw extruder and cast into a film to obtain the base layer. The heating zone temperature of the twin-screw extruder is 160-180℃, and the screw speed is 180rpm. The heating temperature of the casting machine is 50℃.

[0101] In the preparation of the light-shielding layer, no silane coupling agent is added. Specifically, 95 parts by weight of polyethylene terephthalate and 10 parts by weight of carbon black are mixed, melt-extruded into a film, and then the surface is activated by ultraviolet irradiation to obtain the light-shielding layer. The ultraviolet irradiation conditions are: wavelength 254nm, power 30W, treatment for 30s, heating zone temperature of twin-screw extruder of 260-280℃, screw speed of 300rpm; and casting machine heating temperature of 90℃.

[0102] In the preparation of the heat-sealing layer, maleic anhydride and crosslinking agent are not added. Specifically, 100 parts by weight of ethylene-vinyl acetate copolymer are added to the extruder, melt-extruded, cast into a film, and then treated with plasma to obtain the heat-sealing layer. The heating zone temperature of the twin-screw extruder is 140-160℃, and the screw speed is 250rpm. The heating temperature of the casting machine is 50℃. The plasma treatment conditions are: oxygen atmosphere, power 40W, and treatment time 60s.

[0103] Comparative Example 6

[0104] This comparative example differs from Example 1 in the following ways: During the preparation of the antibacterial layer, 10 parts by weight of the β-CD-Humulus / MOF-thymol complex were not added. Specifically:

[0105] The antibacterial layer is prepared by mixing 90 parts by weight of polyethylene and 10 parts by weight of maleic anhydride-grafted polyethylene, and then melting and extruding the mixture through a twin-screw extruder to form a film to obtain the antibacterial layer. The heating zone temperature of the twin-screw extruder is 170-190℃, the screw speed is 400rpm, and the heating temperature of the casting machine is 60℃.

[0106] Related tests

[0107] Peel strength performance test: The peel strength (N / 15mm) of the packaging bags obtained in the examples and comparative examples was tested according to the relevant records in GB / T 10004-2008 "Dry lamination and extrusion lamination of plastic composite films and bags for packaging". The test results are shown in Table 1.

[0108] Transmittance test: The transmittance of the packaging bags obtained in the examples and comparative examples was tested according to the relevant records in GB / T2410-2008 "Determination of transmittance and haze of transparent plastics". The test results are shown in Table 1.

[0109] Table 1. Results of peel strength and light transmittance tests

[0110]

[0111] Table 2 Antibacterial performance test results

[0112]

[0113] The test results above show that ultraviolet irradiation of the light-shielding layer and plasma treatment of the heat-sealing layer can enhance the peel strength; adding a silane coupling agent during the preparation of the light-shielding layer can promote more uniform dispersion of carbon black; and the addition of β-CD-hummus / MOF-thymol complex has a more durable antibacterial effect compared with the addition of hummus carbon dots and thymol alone.

[0114] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0115] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a light-proof aseptic packaging bag, characterized in that, Includes the following steps: S100: A base layer is prepared using raw materials including maleic anhydride-grafted polyethylene and polyethylene. S200, using raw materials including carbon black and polyethylene terephthalate, a light-shielding layer is prepared; S300 uses raw materials including β-cyclodextrin-hope compound, MOF-thymol compound, maleic anhydride-grafted polyethylene, and polyethylene to prepare an antibacterial layer. S400: A heat-sealing layer is prepared using raw materials including ethylene-vinyl acetate copolymer. S500, The base layer and the light-shielding layer are combined to obtain a base layer / light-shielding layer composite layer, the antibacterial layer and the heat-sealing layer are combined to obtain an antibacterial layer / heat-sealing layer composite layer, and the base layer / light-shielding layer composite layer and the antibacterial layer / heat-sealing layer composite layer are combined to obtain the light-shielding aseptic packaging bag; Step S300 specifically includes: S310. Add β-cyclodextrin to deionized water and stir until completely dissolved to obtain a β-cyclodextrin solution. Then add hop carbon dots to the solution, stir evenly, and sonicate to obtain a mixture. Centrifuge to collect the supernatant, freeze-dry to obtain a β-cyclodextrin-hop complex. S320. MOF powder is added to anhydrous ethanol and dispersed evenly to obtain MOF dispersion. Thymol mixture is added dropwise to it, stirred at room temperature and allowed to stand. The precipitate is collected by centrifugation, washed and dried to obtain MOF-thymol complex. S330. The β-cyclodextrin-Humulus complex was dissolved in deionized water and dispersed evenly to obtain a β-cyclodextrin-Humulus complex dispersion. The MOF-thymol complex was dissolved in anhydrous ethanol and dispersed evenly to obtain a MOF-thymol complex dispersion. The MOF-thymol complex dispersion was added dropwise to the β-cyclodextrin-Humulus complex dispersion. After stirring at room temperature, the precipitate was collected by centrifugation, washed, and dried to obtain the β-CD-Humulus / MOF-thymol complex. S340: β-CD-Humulus / MOF-thymol complex, polyethylene, and maleic anhydride-grafted polyethylene are mixed in proportion and then melt-extruded into a film using a twin-screw extruder to obtain an antibacterial layer. The preparation method of hop carbon dots in step S310 is as follows: hop is wrapped in aluminum foil and placed in a sealed environment, and calcined at high temperature to obtain carbonized hop. It is then dissolved in deionized water and boiled. The resulting solution is filtered through a filter membrane to remove the precipitate and obtain a solution containing hop carbon dots. After concentration and freeze-drying, a solid powder is obtained, which is the hop carbon dots. The preparation method of MOF powder in step S320 is as follows: add zirconium nitrate and terephthalic acid to N,N-dimethylformamide, stir until completely dissolved, then add concentrated hydrochloric acid, transfer to a reaction vessel, react at high temperature, cool to room temperature, collect the precipitate by centrifugation, and obtain MOF powder after washing, soaking and drying.

2. The method for preparing a light-proof aseptic packaging bag according to claim 1, characterized in that, Step S100 specifically includes: mixing polyethylene and maleic anhydride-grafted polyethylene in a certain proportion, and then melting and extruding them into a film using an extruder to obtain the base layer.

3. The method for preparing a light-proof aseptic packaging bag according to claim 1, characterized in that, Step S200 specifically includes: mixing polyethylene terephthalate and carbon black in a certain proportion, adding silane coupling agent, melting and extruding to form a film, and then activating the surface by ultraviolet irradiation to obtain a light-shielding layer.

4. The method for preparing a light-proof aseptic packaging bag according to claim 1, characterized in that, Step S400 specifically includes: adding ethylene-vinyl acetate copolymer, maleic anhydride, and crosslinking agent to an extruder, melting and extruding the mixture into a film, and then treating it with plasma to obtain a heat-sealing layer.

5. The method for preparing a light-proof aseptic packaging bag according to claim 1, characterized in that, Step S500 specifically includes: S510. Apply polyurethane adhesive between the base layer and the light-shielding layer, dry it, and then press it with a roller to obtain a base layer / light-shielding layer composite layer. S520. The antibacterial layer and the heat-sealing layer are combined by a composite roller to obtain an antibacterial layer / heat-sealing layer composite layer. S530. Apply polyurethane adhesive between the base layer / light-shielding layer composite layer and the antibacterial layer / heat-sealing layer composite layer, dry, and then press and roll to obtain the packaging bag.

6. A light-proof aseptic packaging bag, characterized in that, It is prepared using the method for preparing light-proof aseptic packaging bags as described in any one of claims 1-5.

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