Antibacterial composite bag for food and preparation method of antibacterial composite bag

Abstract

The invention relates to the field of packaging bags, and discloses an antibacterial composite bag for food and a preparation method thereof, the antibacterial composite bag for food comprises low density polyethylene, a functional additive, modified tetrapod-like zinc oxide whiskers and a lubricant; according to the functional additive, lignin nanoparticles are used as a core, polydopamine is used as a shell, graphene oxide is assembled to prepare a composite material, and gamma-aminopropyltriethoxysilane is used for amination grafting of the composite material. The nano cuprous oxide is loaded on the aminated composite material by adopting a one-step reduction method and reacts with glycidyl dodecyl dimethyl ammonium chloride; the modified tetrapod-like zinc oxide whisker is prepared by coating the surface of the tetrapod-like zinc oxide whisker with silver-doped zinc oxide through a hydrothermal synthesis method, and by adding the functional additive and the modified tetrapod-like zinc oxide whisker, the matrix material is endowed with good mechanical property, antibacterial property, ultraviolet resistance, heat resistance and flame retardance.

Description

Technical Field

[0001] This invention belongs to the field of packaging bag technology, specifically relating to an antibacterial composite bag for food and its preparation method. Background Technology

[0002] Plastic packaging and plastic packaging products are taking up an increasingly larger share of the market, especially composite plastic flexible packaging, which has been widely used in the food, pharmaceutical, and chemical industries. Among them, food packaging accounts for the largest proportion, such as beverage packaging, frozen food packaging, retortable food packaging, and fast food packaging. These products have brought great convenience to people's lives, and plastic packaging bags are one of the most widely used materials in plastic packaging.

[0003] Polyethylene, a typical thermoplastic, is an odorless, tasteless, and non-toxic flammable white powder. It has good chemical stability and can withstand solutions such as dilute nitric acid and dilute sulfuric acid at room temperature. It has a wide range of applications and is commonly used to make food plastic bags. However, ordinary food plastic bags have poor toughness and cannot withstand large tensile and load-bearing forces, which limits their use. Furthermore, existing polyethylene food plastic bags are highly flammable, have poor heat resistance, low UV resistance, and are prone to bacterial growth when in contact with food, severely restricting their widespread application. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide an antibacterial composite bag for food and its preparation method. By adding functional additives and modified tetra-needle zinc oxide whiskers, the matrix material is endowed with good mechanical properties, antibacterial properties, UV resistance, heat resistance and flame retardant properties.

[0005] The objective of this invention can be achieved through the following technical solutions: An antibacterial composite bag for food use comprises the following components in parts by weight: 80-95 parts of low-density polyethylene, 2-6 parts of functional additives, 1-3 parts of modified tetraneedle-shaped zinc oxide whiskers, and 0.5-1.5 parts of lubricant. The functional additive is prepared by obtaining lignin nanoparticles using a high-speed shearing method, then using lignin nanoparticles as the core and polydopamine as the shell, and then assembling graphene oxide to prepare a composite material. Then, the composite material is grafted with γ-aminopropyltriethoxysilane and nanocuprous oxide nanoparticles is loaded onto the aminated composite material using a one-step reduction method. Subsequently, the prepared modified composite material is reacted with glycidyl dodecyl dimethyl ammonium chloride to undergo a ring-opening reaction. The modified tetra-needle zinc oxide whiskers are made by coating the surface of the tetra-needle zinc oxide whiskers with silver-doped zinc oxide through a hydrothermal synthesis method using zinc nitrate hexahydrate and silver nitrate as raw materials.

[0006] Preferably, the preparation method of the functional additive includes the following steps: I. Disperse lignin nanoparticles ultrasonically in deionized water, add dopamine hydrochloride, then add Tris-HCl, adjust the pH of the system to 8.5 with ammonia, stir the reaction for 10-12 hours, and after the reaction is completed, centrifuge, wash and dry to prepare polydopamine-coated lignin nanoparticles. II. Graphene oxide was ultrasonically dispersed in anhydrous ethanol, and then polydopamine-coated lignin nanoparticles were added. The mixture was ultrasonically dispersed until uniform. The resulting suspension was evaporated at room temperature to remove the anhydrous ethanol, and then dried under vacuum and ground to prepare the composite material. Ⅲ. Take γ-aminopropyltriethoxysilane, ethanol and deionized water and stir to mix to obtain silane hydrolysate. Take the composite material and ultrasonically disperse it in the silane hydrolysate. Stir and react for 2-3 hours. After the reaction is completed, centrifuge, wash and dry to prepare the aminated composite material. IV. The aminated composite material was ultrasonically dispersed in deionized water, then anhydrous copper sulfate and sodium dodecyl sulfate were added, and the mixture was ultrasonically dispersed until uniform. After ultrasonication, ascorbic acid was added, and sodium hydroxide was added after stirring for 3-5 minutes. The mixture was stirred and reacted for 20-30 minutes. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified composite material. V. The modified composite material was ultrasonically dispersed in anhydrous ethanol, and then glycidyl dodecyl dimethyl ammonium chloride was added. The mixture was stirred at 65-80°C for 20-24 hours. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the functional additive.

[0007] Preferably, in step I, the mass ratio of lignin nanoparticles, dopamine hydrochloride, and Tris-HCl is 7~9:1:0.5.

[0008] Preferably, in step II, the mass ratio of graphene oxide to polydopamine-coated lignin nanoparticles is 0.05~0.12:1.

[0009] Preferably, in step IV, the mass ratio of the aminated composite material, anhydrous copper sulfate, sodium dodecyl sulfate, and ascorbic acid is 7~10:0.8:3:0.1.

[0010] Preferably, the preparation method of the lignin nanoparticles includes the following steps: alkali lignin is added to a mixed solution of acetone and deionized water, and after stirring and mixing, the solution is centrifuged at 5800~6200 r / min for 3~5 min. Then, the upper layer solution is sheared at 10000~19000 r / min using a high-shear dispersing emulsifier for 5~10 min. Subsequently, the solvent is recovered by a rotary evaporator to prepare lignin nanoparticles.

[0011] Preferably, the preparation method of the epoxypropyl dodecyl dimethyl ammonium chloride includes the following steps: dodecyl dimethyl tertiary amine is placed in a reactor, epichlorohydrin is slowly added dropwise using a dropping funnel, and the mixture is stirred and reacted at 55~65℃ for 2~3h. After the reaction is completed, the mixture is distilled under reduced pressure, recrystallized with acetone, washed and dried to obtain epoxypropyl dodecyl dimethyl ammonium chloride.

[0012] Preferably, the preparation method of the modified tetraneedle zinc oxide whiskers includes the following steps: ultrasonically dispersing tetraneedle zinc oxide whiskers in deionized water to form solution one; preparing solution two by taking zinc nitrate hexahydrate, silver nitrate and deionized water; heating solution one to 55~65℃; slowly adding solution two; maintaining the pH of the mixed solution at 8; continuously stirring the reaction for 2~3 hours; after the reaction is completed, washing, standing, precipitation, filtration and drying are performed; the obtained solid product is sintered at 300~350℃ for 0.5~1 hours to prepare the modified tetraneedle zinc oxide whiskers. The mass ratio of the tetraneedle-shaped zinc oxide whiskers, zinc nitrate hexahydrate, and silver nitrate is 2~4:3.5~6:0.04~0.08.

[0013] Preferably, the lubricant is one or a combination of two of stearyl stearate or polyethylene wax.

[0014] The preparation method of the antibacterial composite bag for food as described above includes the following steps: S1. Weigh each component according to the weight parts, and mechanically blend the low-density polyethylene, functional additives, modified tetra-needle zinc oxide whiskers and lubricant to obtain a mixture. S2. The mixture is melt-extruded through a twin-screw granulator, water-cooled and pelletized. The twin-screw temperature is set at 150~200℃ to obtain plastic masterbatch. S3. The plastic masterbatch is fed into the blown film machine for hot melt extrusion blow molding into a plastic film; S4. Cut the plastic film into plastic films of the required specifications and sizes, and use a bag making machine or heat sealing machine to cut and heat seal the plastic films to prepare antibacterial composite bags for food.

[0015] The beneficial effects of this invention are: This invention first uses a high-speed shearing method to obtain lignin nanoparticles, then deposits polydopamine on the surface of the lignin nanoparticles, and utilizes hydrogen bonds and π-π conjugation between graphene oxide and polydopamine to assemble graphene oxide onto the surface of polydopamine-coated lignin nanoparticles to prepare a composite material. Then, the composite material is grafted with γ-aminopropyltriethoxysilane and a one-step reduction method is used to load nano-cuprous oxide onto the aminated composite material to prepare a modified composite material. Subsequently, a ring-opening reaction is carried out between glycidyl dodecyl dimethyl ammonium chloride and the amino groups on the surface of the modified composite material to prepare a quaternized ammonium modified functional additive.

[0016] Lignin is an abundant biomass macromolecule polymer with environmentally friendly and biodegradable properties. Lignin nanoparticles formed using lignin have a high degree of cross-linking and contain many UV chromophores, exhibiting outstanding UV shielding performance. Furthermore, the phenolic hydroxyl functional groups in lignin nanoparticles can induce bacterial death, demonstrating a certain antibacterial effect. This invention utilizes lignin nanoparticles as the core and polydopamine as the shell. The polyphenolic structure of polydopamine is not only a good char-forming agent, but its catechol has a good free radical scavenging effect during combustion. It is then assembled with graphene oxide, which has good mechanical and barrier properties, to prepare a flame-retardant and toughened composite material. The loading of nano-cuprous oxide and the grafting of quaternary ammonium salt functional groups synergistically enhance the antibacterial performance of the material. In addition, the grafting reaction helps the composite material to be relatively uniformly dispersed in the matrix material, greatly improving the interfacial compatibility between the composite material and the matrix material, which is conducive to the effective performance of its comprehensive properties, while avoiding performance defects caused by the aggregation of nanoparticles.

[0017] This invention utilizes zinc nitrate hexahydrate and silver nitrate as raw materials to coat silver-doped zinc oxide onto the surface of tetra-needle zinc oxide whiskers via a hydrothermal synthesis method. Tetra-needle zinc oxide whiskers, as a type of single-crystal fiber with a unique three-dimensional structure, possess comprehensive properties such as high strength, high modulus, heat resistance, wear resistance, antibacterial properties, and non-toxicity. The coating of silver-doped zinc oxide improves the dispersibility of the tetra-needle zinc oxide whiskers while imparting excellent antibacterial properties to the material. Simultaneously, the zinc oxide shell itself provides UV shielding and photocatalytic activity. This invention, through the addition of functional additives and modified tetra-needle zinc oxide whiskers, endows the matrix material with excellent mechanical properties, antibacterial properties, UV resistance, heat resistance, and flame retardant properties. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing a functional additive includes the following steps: Ⅰ. Take 8g of lignin nanoparticles and ultrasonically disperse them in 300mL of deionized water. At the same time, add 1g of dopamine hydrochloride and then add 0.5g of Tris-HCl. Adjust the pH of the system to 8.5 with ammonia water and stir for 12h. After the reaction is completed, centrifuge, wash and dry to prepare polydopamine-coated lignin nanoparticles. II. Take 0.5g of graphene oxide and ultrasonically disperse it in 100mL of anhydrous ethanol. Then add 5g of polydopamine-coated lignin nanoparticles and continue to ultrasonically disperse it evenly. Volatilize the anhydrous ethanol from the resulting suspension at room temperature, and then grind it after vacuum drying to prepare the composite material. Ⅲ. Take 3g of γ-aminopropyltriethoxysilane, 95mL of ethanol and 5mL of deionized water and stir to mix to obtain silane hydrolysate. Take 5g of composite material and ultrasonically disperse it in silane hydrolysate. Stir and react for 3h. After the reaction is completed, centrifuge, wash and dry to prepare aminated composite material. IV. Take 5g of the aminated composite material and ultrasonically disperse it in 120mL of deionized water. Then add 0.4g of anhydrous copper sulfate and 1.5g of sodium dodecyl sulfate. Continue to ultrasonically disperse it evenly. After ultrasonication, add 0.05g of ascorbic acid and stir for 4min. Then add 0.08g of sodium hydroxide and continue to stir and react for 30min. After the reaction is completed, centrifuge, wash and dry to prepare the modified composite material. V. Take 5g of the modified composite material and ultrasonically disperse it in 120mL of anhydrous ethanol. Then add 1.2g of glycidyl dodecyl dimethyl ammonium chloride and stir at 70℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare the functional additive. The preparation method of lignin nanoparticles includes the following steps: 10g of alkali lignin is added to a mixed solution of acetone and deionized water with a volume ratio of 7:3. After stirring and mixing, the solution is centrifuged at 6000r / min for 5min. Then, the upper layer solution is sheared at 16000r / min for 10min using a high-shear dispersion emulsifier. Subsequently, the solvent is recovered by rotary evaporator to prepare lignin nanoparticles. The preparation method of glycidyl dodecyl dimethyl ammonium chloride includes the following steps: 10.7g of dodecyl dimethyl tertiary amine is placed in a reactor, and 23.3g of epichlorohydrin is slowly added dropwise using a dropping funnel. The mixture is stirred at 60°C for 2 hours. After the reaction is completed, the mixture is distilled under reduced pressure, recrystallized with acetone, washed and dried to obtain glycidyl dodecyl dimethyl ammonium chloride.

[0020] Example 2 A method for preparing modified tetraneedle-shaped zinc oxide whiskers includes the following steps: 3g of tetraneedle-shaped zinc oxide whiskers are ultrasonically dispersed in 100mL of deionized water to form solution one; 5g of zinc nitrate hexahydrate, 0.07g of silver nitrate, and 20mL of deionized water are used to prepare solution two; solution one is heated to 60℃, and solution two is slowly added dropwise, maintaining the pH of the mixed solution at 8, and the reaction is continuously stirred for 2.5h; after the reaction is completed, the mixture is washed, allowed to stand, precipitated, filtered, and dried; the obtained solid product is sintered at 320℃ for 0.5h to obtain modified tetraneedle-shaped zinc oxide whiskers.

[0021] Example 3 An antibacterial composite bag for food, comprising the following components by weight: 82 parts of low-density polyethylene, 2.2 parts of the functional additive prepared in Example 1, 1.1 parts of the modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 0.6 parts of the lubricant stearate octadecyl ester.

[0022] The preparation method of the above-mentioned antibacterial composite bag for food includes the following steps: S1. Weigh each component according to the weight parts, and mechanically blend the low-density polyethylene, functional additives, modified tetra-needle zinc oxide whiskers and lubricant to obtain a mixture. S2. The mixture is melt-extruded through a twin-screw granulator, water-cooled and pelletized. The twin-screw temperature is set at 150~200℃ to obtain plastic masterbatch. S3. The plastic masterbatch is fed into the blown film machine for hot melt extrusion blow molding into a plastic film; S4. Cut the plastic film into plastic films of the required specifications and sizes, and use a bag making machine or heat sealing machine to cut and heat seal the plastic films to prepare antibacterial composite bags for food.

[0023] Example 4 An antibacterial composite bag for food, comprising the following components by weight: 88 parts of low-density polyethylene, 3.5 parts of the functional additive prepared in Example 1, 2.1 parts of the modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 0.9 parts of the lubricant stearate octadecyl ester.

[0024] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0025] Example 5 An antibacterial composite bag for food, comprising the following components by weight: 93 parts of low-density polyethylene, 5.6 parts of the functional additive prepared in Example 1, 2.6 parts of the modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 1.2 parts of the lubricant stearate 1 / 2 ester.

[0026] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0027] Comparative Example 1: A method for preparing a functional additive includes the following steps: Ⅰ. Take 3g of γ-aminopropyltriethoxysilane, 95mL of ethanol and 5mL of deionized water and stir to mix to obtain silane hydrolysate. Take 5g of graphene oxide and ultrasonically disperse it in the silane hydrolysate. Stir and react for 3h. After the reaction is completed, centrifuge, wash and dry to prepare aminated graphene oxide. II. Take 5g of aminated graphene oxide and ultrasonically disperse it in 120mL of deionized water. Then add 0.4g of anhydrous copper sulfate and 1.5g of sodium dodecyl sulfate. Continue to ultrasonically disperse it evenly. After ultrasonication, add 0.05g of ascorbic acid and stir for 4min. Then add 0.08g of sodium hydroxide and continue to stir and react for 30min. After the reaction is completed, centrifuge, wash and dry to prepare modified graphene oxide. III. Take 5g of modified graphene oxide and ultrasonically disperse it in 120mL of anhydrous ethanol. Then add 1.2g of glycidyl dodecyl dimethyl ammonium chloride prepared in Example 1. Stir and react at 70℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare the functional additive.

[0028] Comparative Example 2: An antibacterial composite bag for food use, comprising the following components in parts by weight: 93 parts of low-density polyethylene, 5.6 parts of the modified composite material prepared in Example 1, 2.6 parts of the modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 1.2 parts of the lubricant stearate 1 / 2 ester.

[0029] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0030] Comparative Example 3: An antibacterial composite bag for food use, comprising the following components in parts by weight: 93 parts of low-density polyethylene, 5.6 parts of the composite material prepared in Example 1, 2.6 parts of modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 1.2 parts of stearyl stearate lubricant.

[0031] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0032] Comparative Example 4: An antibacterial composite bag for food use, comprising the following components by weight: 93 parts of low-density polyethylene, 5.6 parts of functional additives prepared in Comparative Example 1, 2.6 parts of modified tetraneedle-shaped zinc oxide whiskers prepared in Example 2, and 1.2 parts of octadecyl stearate lubricant.

[0033] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0034] Comparative Example 5: An antibacterial composite bag for food use, comprising the following components in parts by weight: 93 parts of low-density polyethylene, 5.6 parts of the functional additive prepared in Example 1, 2.6 parts of tetraneedle-shaped zinc oxide whiskers, and 1.2 parts of stearyl stearate lubricant.

[0035] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0036] Comparative Example 6: An antibacterial composite bag for food use, comprising the following components in parts by weight: 93 parts of low-density polyethylene, 5.6 parts of the functional additive prepared in Example 1, and 1.2 parts of the lubricant stearyl stearate.

[0037] The preparation method of the above-mentioned antibacterial composite bag for food is the same as that in Example 3.

[0038] Performance testing The composite bags prepared in Examples 3-5 and Comparative Examples 2-6 were subjected to performance testing: (1) Mechanical property test: The prepared composite bag was cut into long strips with a width of 15 mm and a length of ≥150 mm. The tensile strength and elongation at break were tested on a universal testing machine in accordance with GB / T 1040.3-2006. The tensile speed was set to 200 mm / min. The data results are shown in Table 1.

[0039] (2) UV resistance test: The mechanical properties of the sample were tested after aging under a 20W UV lamp for 72 hours. The sample emitted short-wave UV light with a characteristic wavelength of 253.7nm, and the UV irradiance at 20cm vertically from the center of the lamp was 1400μw / cm. 2 The sample was placed parallel to the light source in a fixed position for UV resistance testing, and the data results are shown in Table 1.

[0040] (3) Heat resistance test: Thermogravimetric analysis was used to test the thermal stability under nitrogen atmosphere and heating rate of 10℃ / min. The data results are shown in Table 1.

[0041] (4) Antibacterial performance test: The antibacterial performance was tested in accordance with QB / T 2591-2003. The test strains were Staphylococcus aureus and Escherichia coli. The data results are shown in Table 1.

[0042] (5) Flame retardant performance test: The flame retardant performance of the samples was evaluated by the limiting oxygen index, and the data results are shown in Table 1.

[0043] Table 1 Sample performance test results

[0044] As can be seen from the data in Table 1, the composite bags prepared in Examples 3-5 of this invention have high tensile strength, are not easily broken, and still possess high tensile strength and elongation at break after 72 hours of UV aging, exhibiting excellent UV resistance, as well as good heat resistance, antibacterial properties, and flame retardant properties. In Comparative Example 2, the functional additive components were replaced with an equal amount of modified composite material, and in Comparative Example 3, the functional additive components were replaced with an equal amount of composite material. The measured antibacterial properties in Comparative Examples 2-3 were lower than those in Examples 3-5, with Comparative Example 3 showing a significant decrease compared to Comparative Example 2. This is because the loading of nano-cuprous oxide and the grafting of quaternary ammonium salt functional groups synergistically enhance the antibacterial properties of the material. Furthermore, the measured tensile strength and elongation at break in Comparative Example 3 were lower than those in Examples 3-5, due to the agglomeration of the composite material leading to a decrease in mechanical properties. In Comparative Example 4, the added functional additives did not introduce polydopamine-coated lignin nanoparticles, resulting in lower measured mechanical properties and mechanical properties after UV aging. The mechanical properties, antibacterial rate, and limiting oxygen index of the materials were lower than those of Examples 3-5, indicating that the introduction of polydopamine-coated lignin nanoparticles is beneficial to improving the mechanical properties, UV resistance, antibacterial properties, and flame retardant properties of the materials. In Comparative Example 5, no modification treatment was performed on the tetra-needle zinc oxide whiskers, and no modified tetra-needle zinc oxide whisker component was added to Comparative Example 6. The mechanical properties, as well as the mechanical properties after UV aging, the initial thermal decomposition temperature, and the antibacterial rate of Comparative Examples 5-6 were lower than those of Examples 3-5. Moreover, the decrease in various properties in Comparative Example 6 was more significant than that in Comparative Example 5, indicating that the addition of modified tetra-needle zinc oxide whiskers has greatly improved the mechanical properties, UV resistance, heat resistance, and antibacterial properties of the materials to a certain extent.

[0045] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A food-grade antibacterial composite bag, characterized in that, It includes the following components by weight: 80-95 parts of low-density polyethylene, 2-6 parts of functional additives, 1-3 parts of modified tetraneedle-shaped zinc oxide whiskers, and 0.5-1.5 parts of lubricant; The functional additive is prepared by obtaining lignin nanoparticles using a high-speed shearing method, then using lignin nanoparticles as the core and polydopamine as the shell, and then assembling graphene oxide to prepare a composite material. Then, the composite material is grafted with γ-aminopropyltriethoxysilane and nanocuprous oxide nanoparticles is loaded onto the aminated composite material using a one-step reduction method. Subsequently, the prepared modified composite material is reacted with glycidyl dodecyl dimethyl ammonium chloride to undergo a ring-opening reaction. The modified tetra-needle zinc oxide whiskers are made by coating the surface of the tetra-needle zinc oxide whiskers with silver-doped zinc oxide through a hydrothermal synthesis method using zinc nitrate hexahydrate and silver nitrate as raw materials.

2. The antibacterial composite bag for food use according to claim 1, characterized in that, The preparation method of the functional additive includes the following steps: I. Disperse lignin nanoparticles ultrasonically in deionized water, add dopamine hydrochloride, then add Tris-HCl, adjust the pH of the system to 8.5 with ammonia, stir the reaction for 10-12 hours, and after the reaction is completed, centrifuge, wash and dry to prepare polydopamine-coated lignin nanoparticles. II. Graphene oxide was ultrasonically dispersed in anhydrous ethanol, and then polydopamine-coated lignin nanoparticles were added. The mixture was ultrasonically dispersed until uniform. The resulting suspension was evaporated at room temperature to remove the anhydrous ethanol, and then dried under vacuum and ground to prepare the composite material. Ⅲ. Take γ-aminopropyltriethoxysilane, ethanol and deionized water and stir to mix to obtain silane hydrolysate. Take the composite material and ultrasonically disperse it in the silane hydrolysate. Stir and react for 2-3 hours. After the reaction is completed, centrifuge, wash and dry to prepare the aminated composite material. IV. The aminated composite material was ultrasonically dispersed in deionized water, then anhydrous copper sulfate and sodium dodecyl sulfate were added, and the mixture was ultrasonically dispersed until uniform. After ultrasonication, ascorbic acid was added, and sodium hydroxide was added after stirring for 3-5 minutes. The mixture was stirred and reacted for 20-30 minutes. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified composite material. V. The modified composite material was ultrasonically dispersed in anhydrous ethanol, and then glycidyl dodecyl dimethyl ammonium chloride was added. The mixture was stirred at 65-80°C for 20-24 hours. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the functional additive.

3. The antibacterial composite bag for food use according to claim 2, characterized in that, In step I, the mass ratio of lignin nanoparticles, dopamine hydrochloride, and Tris-HCl is 7~9:1:0.

5.

4. The antibacterial composite bag for food use according to claim 2, characterized in that, In step II, the mass ratio of graphene oxide to polydopamine-coated lignin nanoparticles is 0.05~0.12:

1.

5. The antibacterial composite bag for food use according to claim 2, characterized in that, In step IV, the mass ratio of the aminated composite material, anhydrous copper sulfate, sodium dodecyl sulfate, and ascorbic acid is 7-10:0.8:3:0.

1.

6. The antibacterial composite bag for food use according to claim 2, characterized in that, The preparation method of the lignin nanoparticles includes the following steps: alkali lignin is added to a mixed solution of acetone and deionized water, and after stirring and mixing, the solution is centrifuged at 5800~6200 r / min for 3~5 min. Then, the upper layer solution is sheared at 10000~19000 r / min for 5~10 min using a high shear dispersion emulsifier. Subsequently, the solvent is recovered by rotary evaporator to prepare lignin nanoparticles.

7. The antibacterial composite bag for food use according to claim 2, characterized in that, The preparation method of the epoxypropyl dodecyl dimethyl ammonium chloride includes the following steps: dodecyl dimethyl tertiary amine is placed in a reactor, epichlorohydrin is slowly added dropwise using a dropping funnel, and the mixture is stirred and reacted at 55~65℃ for 2~3h. After the reaction is completed, the mixture is distilled under reduced pressure, recrystallized with acetone, washed and dried to prepare epoxypropyl dodecyl dimethyl ammonium chloride.

8. The antibacterial composite bag for food use according to claim 1, characterized in that, The method for preparing the modified tetra-needle zinc oxide whiskers includes the following steps: ultrasonically dispersing the tetra-needle zinc oxide whiskers in deionized water to form solution one; preparing solution two by taking zinc nitrate hexahydrate, silver nitrate and deionized water; heating solution one to 55~65℃; slowly adding solution two; maintaining the pH of the mixed solution at 8; continuously stirring the reaction for 2~3 hours; after the reaction is completed, washing, settling, precipitation, filtration and drying are performed; the obtained solid product is sintered at 300~350℃ for 0.5~1 hours to prepare the modified tetra-needle zinc oxide whiskers. The mass ratio of the tetraneedle-shaped zinc oxide whiskers, zinc nitrate hexahydrate, and silver nitrate is 2~4:3.5~6:0.04~0.

08.

9. The antibacterial composite bag for food use according to claim 1, characterized in that, The lubricant is one or a combination of two of stearyl stearate or polyethylene wax.

10. A method for preparing an antibacterial composite bag for food according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Weigh each component according to the weight parts, and mechanically blend the low-density polyethylene, functional additives, modified tetra-needle zinc oxide whiskers and lubricant to obtain a mixture. S2. The mixture is melt-extruded through a twin-screw granulator, water-cooled and pelletized. The twin-screw temperature is set at 150~200℃ to obtain plastic masterbatch. S3. The plastic masterbatch is fed into the blown film machine for hot melt extrusion blow molding into a plastic film; S4. Cut the plastic film into plastic films of the required specifications and sizes, and use a bag making machine or heat sealing machine to cut and heat seal the plastic films to prepare antibacterial composite bags for food.

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