Antibacterial polyethylene composite packaging film and preparation method thereof

Abstract

The invention relates to the technical field of polyethylene packaging films, and particularly discloses an antibacterial polyethylene composite packaging film and a preparation method thereof.The antibacterial polyethylene composite packaging film comprises an inner layer, a middle layer and an outer layer, the inner layer is prepared from the following raw materials in parts by weight: 60 to 80 parts of low-density polyethylene, 25 to 35 parts of polypropylene, 4 to 6 parts of modified filler, 0.3 to 0.6 part of antioxidant and 1 to 3 parts of compatilizer; the middle layer is prepared from 62 to 75 parts of high-density polyethylene, 28 to 40 parts of ethylene-vinyl alcohol copolymer, 0.8 to 1 part of anti-binding agent and 2 to 5 parts of compatilizer; the outer layer comprises 55-70 parts of high-density polyethylene, 35-45 parts of metallocene polyethylene, 12-25 parts of nylon, 4-10 parts of antibacterial modified montmorillonite and 3-6 parts of compatilizer, the polyethylene composite packaging film has good processability and good stability, the composite film adopts a double-layer antibacterial design of the inner layer and the outer layer, the middle layer has excellent barrier property and good compactness, and the polyethylene composite packaging film is suitable for being used as a packaging film. The composite packaging film has excellent antibacterial performance and mechanical performance and good comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene packaging films, in particular to an antibacterial polyethylene composite packaging film and a preparation method thereof. Background Art

[0002] In the modern packaging industry, polyethylene is one of the most widely used packaging substrates due to its safety, non-toxicity, excellent mechanical properties, chemical stability, and cost advantages. However, traditional polyethylene packaging films are difficult to resist microbial attack during long-term use, and this defect is particularly prominent in the food packaging field. In the food packaging field, if the packaging film fails to inhibit the growth of microorganisms such as bacteria and mold during the storage and transportation of perishable foods such as fresh fruits and vegetables, meat, and dairy products, it can easily lead to food spoilage, causing not only economic losses but also food safety issues. In recent years, with the improvement of living standards and the strengthening of hygiene awareness, people have paid more and more attention to food safety issues, resulting in an increasing demand for antibacterial polyethylene packaging films.

[0003] Existing polyethylene films achieve antimicrobial properties by adding inorganic and organic antimicrobial agents. Inorganic antimicrobial agents generally have poor dispersion in the polyethylene matrix and are prone to agglomeration, resulting in reduced antimicrobial efficacy and mechanical properties of the polyethylene film. Organic antimicrobial agents offer broad-spectrum antimicrobial properties, but their compatibility with polyethylene is poor and they are prone to migration, posing safety risks.

[0004] Chinese patent application CN109054145A discloses an antimicrobial polyethylene food packaging film comprising at least one antimicrobial film layer. The polyethylene antimicrobial film layer is composed of a polyethylene substrate, a nanoscale inorganic antimicrobial agent, a compatibilizer, and a quaternary ammonium antimicrobial agent grafted onto nanocrystalline cellulose. The quaternary ammonium antimicrobial agent grafted onto nanocrystalline cellulose is prepared by irradiating the quaternary ammonium monomer methacryloyloxyethyl-benzyl-dimethylammonium chloride onto nanocrystalline cellulose. The antimicrobial polyethylene food packaging film utilizes a composite antimicrobial agent, combining an inorganic antimicrobial agent with an organic antimicrobial agent, exhibiting excellent antimicrobial properties while also improving the film's tensile strength and barrier properties. However, the inorganic antimicrobial agent has poor dispersibility, which affects the film's mechanical and processing properties. Furthermore, the cobalt source irradiation results in high production costs, limiting its application. Chinese patent application CN116278273A discloses an antibacterial polyethylene composite film comprising an outer film, a middle film, and an inner film adhered in sequence; the outer film comprises linear low-density polyethylene, a hydrophobic agent, modified mica powder, ethylene-propylene rubber, and a first low-density polyethylene; the middle film comprises a second low-density polyethylene, an organic antibacterial agent, mordenite, and oleamide; and the inner film comprises high-density polyethylene, a third low-density polyethylene, modified ceramic fiber, modified zirconium phosphate-loaded silver, and nano-zinc oxide. The polyethylene composite film utilizes a synergistic antibacterial mechanism, exhibiting good sterilization and antibacterial efficacy, and exhibiting good thermal stability and corrosion resistance. However, the organic antibacterial agent is prone to migration, affecting safety performance, while the inorganic antibacterial agent has poor dispersibility and easily becomes a stress concentration point when subjected to stress, resulting in a significant decrease in the tensile strength of the composite film, affecting the overall performance of the composite film, and increasing the cost.

[0005] Therefore, there is an urgent need to develop a polyethylene composite packaging film with excellent antibacterial efficacy and mechanical properties.

[0006] Summary of the invention (1) Technical problems solved In view of the shortcomings of the existing technology, the present invention provides an antibacterial polyethylene composite packaging film and a preparation method thereof, which solves the problems of poor antibacterial properties and general mechanical properties of polyethylene packaging films. The prepared polyethylene composite packaging film has long-lasting antibacterial properties.

[0007] (2) Technical solution To achieve the above-mentioned object, the present invention discloses an antibacterial polyethylene composite packaging film, comprising an inner layer, an intermediate layer, and an outer layer. The inner layer comprises, by weight, 60-80 parts of low-density polyethylene, 25-35 parts of polypropylene, 4-6 parts of modified filler, 0.3-0.6 parts of antioxidant, and 1-3 parts of compatibilizer; the intermediate layer comprises 62-75 parts of high-density polyethylene, 28-40 parts of ethylene-vinyl alcohol copolymer, 0.8-1 parts of anti-adhesive agent, and 2-5 parts of compatibilizer; and the outer layer comprises 55-70 parts of high-density polyethylene, 35-45 parts of metallocene polyethylene, 12-25 parts of nylon, 4-10 parts of antibacterial modified montmorillonite, and 3-6 parts of compatibilizer. The modified filler in the inner layer raw material is antibacterial modified graphene, which is obtained by reacting carboxylated graphene with polyhexamethylene biguanide; The compatibilizer in the inner layer raw material is a maleic anhydride modified blend, and the maleic anhydride modified blend is a maleic anhydride modified polyethylene and polypropylene blend; The compatibilizer in the intermediate layer raw material is maleic anhydride grafted polyethylene; The compatibilizer in the outer layer raw material is ethylene-ethyl acrylate copolymer (EAA).

[0008] Preferably, the antioxidant in the inner layer raw material consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0009] Preferably, the anti-adhesive agent in the intermediate layer raw material is talc.

[0010] Preferably, the compatibilizer in the inner layer raw material is a maleic anhydride modified blend, and the preparation method of the maleic anhydride modified blend is as follows: 10g polyethylene, 8g polypropylene, 10mL acetone, 1g maleic anhydride and 0.2g dicumyl peroxide are mixed evenly, after the acetone is volatilized, transferred to a twin-screw extruder, and melt blended at 205°C. After the melt blending is completed, it is extruded and cooled to obtain the maleic anhydride modified blend.

[0011] Preferably, the method for preparing the antibacterial modified graphene comprises the following steps: S1. Ultrasonic dispersion of graphene oxide in deionized water to obtain a suspension after uniform dispersion, addition of sodium hydroxide and chloroacetic acid, water bath ultrasonication, filtration, washing with deionized water, and drying to obtain carboxylated graphene; S2. Ultrasonic dispersion of carboxylated graphene in N,N-dimethylformamide. After uniform dispersion, polyhexamethylene biguanide, 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and N,N-diisopropylethylamine are added. The mixture is heated to react. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried to obtain antibacterial modified graphene.

[0012] Preferably, the addition ratio of graphene oxide, deionized water, sodium hydroxide and chloroacetic acid in S1 is 100 mg: 100-120 mL: 1-1.5 g: 0.8-1.25 g.

[0013] Preferably, the water bath ultrasound time in S1 is 2-4 hours.

[0014] Preferably, the addition ratio of carboxylated graphene, N,N-dimethylformamide, polyhexamethylene biguanide, 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and N,N-diisopropylethylamine in S2 is 1 g: 400-450 mL: 1.2-2 g: 0.35-0.4 g: 0.2-0.25 g.

[0015] Preferably, the reaction temperature in S2 is 95-105° C., and the reaction time is 8-12 h.

[0016] Preferably, the preparation method of the antibacterial modified montmorillonite comprises the following steps: Step (1), ultrasonically dispersing the nano-montmorillonite into an ethanol solution, adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane after uniform dispersion, adjusting the pH to 4-5 with glacial acetic acid, heating, reacting, filtering, washing with anhydrous ethanol, and drying to obtain epoxidized montmorillonite; Step (2), ultrasonically dispersing the epoxidized montmorillonite in deionized water, adding 5-aminopentyl-dimethyl-amine after uniform dispersion, stirring and mixing, reacting, filtering, washing with deionized water, and drying to obtain modified montmorillonite; Step (3), ultrasonically dispersing the modified montmorillonite in deionized water, adding vinylbenzyl chloride and hydrochloric acid after the reaction is uniform, condensing and refluxing, reacting, centrifuging, washing with anhydrous ethanol and deionized water, and drying to obtain antibacterial modified montmorillonite.

[0017] Preferably, in step (1), the addition ratio of nano-montmorillonite, ethanol solution, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 10 g: 250-320 mL: 1.2-2 g.

[0018] Preferably, the reaction temperature in step (1) is 75-85° C., and the reaction time is 2-4 h.

[0019] Preferably, the ethanol solution in step (1) is a 50% wt ethanol aqueous solution.

[0020] Preferably, in step (2), the addition ratio of epoxidized montmorillonite, deionized water, and 5-aminopentyl-dimethyl-amine is 10 g: 480-600 mL: 15-21 g.

[0021] Preferably, the reaction temperature in step (2) is 20-35° C., and the reaction time is 18-24 h.

[0022] Preferably, in step (3), the addition ratio of modified montmorillonite, deionized water, vinylbenzyl chloride and hydrochloric acid is 10 g: 750-950 mL: 5-8 g: 1.5-2 g.

[0023] Preferably, the reaction temperature in step (3) is 80-95° C., and the reaction time is 6-9 h.

[0024] Preferably, the hydrochloric acid in step (3) is hydrochloric acid with a mass fraction of 36.5%.

[0025] A method for preparing an antibacterial polyethylene composite packaging film comprises the following steps: Step 1: melt-blending the inner layer raw materials of low-density polyethylene, polypropylene, modified filler, antioxidant, and compatibilizer to obtain an inner layer melt; drying the ethylene-vinyl alcohol copolymer at 80°C for 4 hours, and melt-blending the middle layer raw materials of high-density polyethylene, ethylene-vinyl alcohol copolymer, anti-adhesive agent, and compatibilizer to obtain an middle layer melt; drying the nylon at 80°C for 4 hours, and melt-blending the outer layer raw materials of high-density polyethylene, metallocene polyethylene, nylon, antibacterial modified montmorillonite, and compatibilizer to obtain an outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die head, cooled by a chilled roller, and then biaxially stretched. After the stretching is completed, the film is pulled, rolled, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

[0026] Preferably, in the step 1, the melt blending of the inner layer, the middle layer and the outer layer is carried out in a three-layer co-extrusion film blowing machine, the temperature of the inner layer melt blending is 165-185°C, the screw speed is 35r / min, the temperature of the middle layer melt blending is 190-205°C, the screw speed is 40r / min, and the temperature of the outer layer melt blending is 210-230°C, and the screw speed is 42r / min.

[0027] Preferably, during the extrusion molding process in step 2, the die temperature is 185-205° C., the melt pressure is 18-25 MPa, the biaxial stretching longitudinal stretching ratio is 2.5-3.5 times, the transverse stretching ratio is 3-4 times, and the pulling speed is 10-12 m / min.

[0028] (3) Beneficial technical effects Compared with the prior art, the present invention has the following beneficial effects: (1) The inner layer of the present invention uses a blend of low-density polyethylene, polypropylene, modified fillers, antioxidants, and a compatibilizer, maleic anhydride, as raw materials, wherein low-density polyethylene can provide softness and heat sealing properties, and polypropylene can enhance rigidity, complementing low-density polyethylene to improve the mechanical properties of the matrix. The added modified filler is antibacterial modified graphene. Due to its small size, graphene oxide has a nano-size effect and has excellent antibacterial properties. It can cut cells and destroy cell membranes, thereby killing bacteria quickly and efficiently. After the graphene oxide is carboxylated, the carboxyl groups on the carboxylated graphene react with the amino groups on the polyhexamethylene biguanide to undergo an amidation reaction, and the long-term antibacterial agent polyhexamethylene biguanide is loaded on the graphene oxide to obtain antibacterial modified graphene, which has long-term antibacterial efficacy and is not easily dissolved. Furthermore, the amide bond introduced during the reaction can generate electrostatic effects with the ions on the bacterial cells, and through mutual attraction, it combines with the cell membrane of the bacterial cells, thereby killing the bacteria and further improving the antibacterial effect. Polyhexamethylene biguanide, through its positive charge, adsorbs onto microbial cell membranes, disrupting the membrane structure and leading to leakage of intracellular substances. Maleic anhydride-modified blends interact with the guanidine groups on the surface of antimicrobial-modified graphene, promoting the dispersion of graphene oxide. They also exhibit excellent compatibility with low-density polyethylene and polypropylene.

[0029] (2) The intermediate layer in the present invention uses high-density polyethylene, ethylene-vinyl alcohol copolymer, anti-adhesive talc powder, and compatibilizer maleic anhydride grafted polyethylene as raw materials. The high-density polyethylene has strong rigidity and can provide mechanical support. The ethylene-vinyl alcohol copolymer has high barrier properties, the ethylene chain segment provides flexibility, and the vinyl alcohol group forms a crystalline area through hydrogen bonding, which has a strong barrier effect on small molecules such as oxygen and water vapor.

[0030] (3) The outer layer of the present invention uses high-density polyethylene, metallocene polyethylene, nylon, antibacterial modified montmorillonite, and a compatibilizer. Among them, high-density polyethylene and metallocene polyethylene can provide strength, improve the toughness of the matrix, play a role in structural support, and reduce stress concentration. Metallocene polyethylene has the characteristics of high heat resistance, and at the same time has excellent mechanical properties and chemical stability, which can improve the toughness of the outer layer and effectively prevent brittle cracking. Nylon has excellent mechanical strength and can improve the wear resistance and puncture resistance of the matrix. Nano-montmorillonite has low cost. Nano-montmorillonite is modified by introducing epoxy groups on its surface. The epoxy groups on the epoxidized montmorillonite react with the amino groups on 5-aminopentyl-dimethyl-amine to obtain modified montmorillonite. The modified montmorillonite reacts with vinylbenzyl chloride to introduce quaternary ammonium salts on the montmorillonite to obtain antibacterial modified montmorillonite. The quaternary ammonium salts are not easy to migrate and precipitate, can be slowly released, and have high safety. Nano-montmorillonite can fill the gaps between resin molecular chains, reduce the permeation channels of small molecules, and improve barrier properties. The quaternary ammonium salts introduced on the surface of montmorillonite, the cations on the quaternary ammonium salts can be adsorbed on the cell membrane surface of negatively charged bacteria, thereby changing the permeability of the bacterial cell wall, causing an imbalance in the cell membrane charge and effectively killing the bacteria.

[0031] (4) The antibacterial polyethylene composite packaging film prepared by the three-layer composite structure in the present invention has good processing performance and good stability. Biaxial stretching can induce molecular chain orientation crystallization and improve mechanical properties. The composite film material adopts a double-layer antibacterial design of the inner layer and the outer layer. The synergistic effect can further inhibit the growth of bacteria and kill bacteria. The antibacterial agent is bonded to the matrix, which effectively increases the effective period of the antibacterial effect and avoids the precipitation of the antibacterial agent, thereby improving safety performance. The middle layer has excellent barrier properties and good density, which can reduce the permeability of oxygen and water vapor. The introduced graphene oxide and nano-montmorillonite also have excellent mechanical properties. After modification, they effectively avoid agglomeration and can improve the mechanical strength of the matrix. The polyethylene composite packaging film has excellent antibacterial and mechanical properties and good comprehensive performance. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Example 1

[0033] A method for preparing antibacterial modified graphene comprises the following steps: S1. Ultrasonic dispersion of 100 mg of graphene oxide in 100 mL of deionized water was performed to obtain a suspension after uniform dispersion. 1 g of sodium hydroxide and 0.8 g of chloroacetic acid were added, and the suspension was ultrasonicated in a water bath for 2 h. The suspension was filtered, washed with deionized water, and dried to obtain carboxylated graphene. S2. Ultrasonic disperse 1 g of carboxylated graphene in 400 mL of N,N-dimethylformamide. After uniform dispersion, add 1.2 g of polyhexamethylene biguanide, 0.35 g of 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and 0.2 g of N,N-diisopropylethylamine. Heat and react at 95 °C for 12 h. After the reaction is completed, filter, wash with anhydrous ethanol, and dry to obtain antibacterial modified graphene. Example 2

[0034] A method for preparing antibacterial modified graphene comprises the following steps: S1. Ultrasonic dispersion of 100 mg of graphene oxide in 110 mL of deionized water was performed to obtain a suspension after uniform dispersion. 1.2 g of sodium hydroxide and 0.96 g of chloroacetic acid were added, and the mixture was ultrasonicated in a water bath for 3 h. The mixture was filtered, washed with deionized water, and dried to obtain carboxylated graphene. S2. Ultrasonic disperse 1 g of carboxylated graphene in 420 mL of N,N-dimethylformamide. After uniform dispersion, add 1.8 g of polyhexamethylene biguanide, 0.38 g of 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and 0.24 g of N,N-diisopropylethylamine. Heat and react at 100 ° C for 10 h. After the reaction is completed, filter, wash with anhydrous ethanol, and dry to obtain antibacterial modified graphene. Example 3

[0035] A method for preparing antibacterial modified graphene comprises the following steps: S1. Ultrasonic dispersion of 100 mg of graphene oxide in 120 mL of deionized water was performed to obtain a suspension after uniform dispersion. 1.5 g of sodium hydroxide and 1.25 g of chloroacetic acid were added, and the mixture was ultrasonicated in a water bath for 4 h. The mixture was filtered, washed with deionized water, and dried to obtain carboxylated graphene. S2. Ultrasonic disperse 1 g of carboxylated graphene in 450 mL of N,N-dimethylformamide. After uniform dispersion, add 2 g of polyhexamethylene biguanide, 0.4 g of 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and 0.25 g of N,N-diisopropylethylamine. Heat and react at 105 °C for 8 h. After the reaction is completed, filter, wash with anhydrous ethanol, and dry to obtain antibacterial modified graphene. Example 4

[0036] A method for preparing antibacterial modified montmorillonite comprises the following steps: Step (1), ultrasonically dispersing 10 g of nano-montmorillonite into 250 mL of ethanol solution, wherein the ethanol solution is a 50% wt ethanol aqueous solution, adding 1.2 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane after uniform dispersion, adjusting the pH to 4 with glacial acetic acid, heating, reacting at 75 ° C for 4 h, filtering, washing with anhydrous ethanol, and drying to obtain epoxidized montmorillonite; Step (2), ultrasonically disperse 10 g of epoxidized montmorillonite in 480 mL of deionized water, and after uniform dispersion, add 15 g of 5-aminopentyl-dimethyl-amine, stir and mix, react at 20° C. for 24 h. After the reaction is completed, filter, wash with deionized water, and dry to obtain modified montmorillonite; Step (3), ultrasonically disperse 10g of modified montmorillonite in 750mL of deionized water, and after uniform reaction, add 5g of vinylbenzyl chloride and 1.5g of hydrochloric acid, wherein the hydrochloric acid is 36.5% by mass, condense and reflux, react at 80°C for 9h, after the reaction is completed, centrifuge, wash with anhydrous ethanol and deionized water, and dry to obtain antibacterial modified montmorillonite. Example 5

[0037] A method for preparing antibacterial modified montmorillonite comprises the following steps: Step (1), ultrasonically dispersing 10 g of nano-montmorillonite into 280 mL of ethanol solution, wherein the ethanol solution is a 50% wt ethanol aqueous solution, adding 1.8 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane after uniform dispersion, adjusting the pH to 4.5 with glacial acetic acid, heating, reacting at 80° C. for 3 h, filtering after the reaction, washing with anhydrous ethanol, and drying to obtain epoxidized montmorillonite; Step (2), ultrasonically disperse 10 g of epoxidized montmorillonite in 550 mL of deionized water, and after uniform dispersion, add 18 g of 5-aminopentyl-dimethyl-amine, stir and mix, and react at 30° C. for 22 h. After the reaction is completed, filter, wash with deionized water, and dry to obtain modified montmorillonite; Step (3), ultrasonically disperse 10g of modified montmorillonite in 850mL of deionized water, and after uniform reaction, add 7g of vinylbenzyl chloride and 1.8g of hydrochloric acid, wherein the hydrochloric acid is 36.5% by mass, condense and reflux, react at 90°C for 8h, after the reaction is completed, centrifuge, wash with anhydrous ethanol and deionized water, and dry to obtain antibacterial modified montmorillonite. Example 6

[0038] A method for preparing antibacterial modified montmorillonite comprises the following steps: Step (1), ultrasonically dispersing 10 g of nano-montmorillonite into 320 mL of ethanol solution, wherein the ethanol solution is a 50% wt ethanol aqueous solution, adding 2 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane after uniform dispersion, adjusting the pH to 5 with glacial acetic acid, heating, reacting at 85° C. for 2 h, filtering after the reaction, washing with anhydrous ethanol, and drying to obtain epoxidized montmorillonite; Step (2), ultrasonically dispersing 10 g of epoxidized montmorillonite into 600 mL of deionized water, adding 21 g of 5-aminopentyl-dimethyl-amine after uniform dispersion, stirring and mixing, reacting at 35° C. for 18 h. After the reaction is completed, filtering, washing with deionized water, and drying to obtain modified montmorillonite; Step (3), ultrasonically disperse 10g of modified montmorillonite in 950mL of deionized water, and after uniform reaction, add 8g of vinylbenzyl chloride and 2g of hydrochloric acid, wherein the hydrochloric acid is 36.5% by mass, condense and reflux, react at 95°C for 6h, after the reaction is completed, centrifuge, wash with anhydrous ethanol and deionized water, and dry to obtain antibacterial modified montmorillonite. Example 7

[0039] A method for preparing an antibacterial polyethylene composite packaging film comprises the following steps: Step 1: melt-blend 60 parts of low-density polyethylene, 25 parts of polypropylene, 4 parts of antibacterial modified graphene, 0.3 parts of antioxidant, and 1 part of compatibilizer maleic anhydride modified blend as the inner layer raw material, wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, the temperature of the inner layer melt blending is 165°C, the screw speed is 35r / min, and the inner layer melt is obtained; dry the ethylene-vinyl alcohol copolymer at 80°C for 4h, and mix 62 parts of high-density polyethylene, 28 parts of ethylene-vinyl alcohol as the intermediate layer raw materials, ... The copolymer, 0.8 parts of anti-blocking agent talc, and 2 parts of compatibilizer maleic anhydride grafted polyethylene were melt-blended, the temperature of the middle layer melt blending was 190°C, and the screw speed was 40r / min to obtain the middle layer melt; the nylon was dried at 80°C for 4h, and the outer layer raw materials 55 parts of high-density polyethylene, 35 parts of metallocene polyethylene, 12 parts of nylon, 4 parts of antibacterial modified montmorillonite, and 3 parts of compatibilizer ethylene-ethyl acrylate copolymer were melt-blended by weight, the temperature of the outer layer melt blending was 210°C, and the screw speed was 42r / min to obtain the outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die. During the extrusion molding process, the die temperature is 185°C and the melt pressure is 25 MPa. After cooling by a chilled roller, biaxial stretching is performed. The longitudinal stretching ratio of the biaxial stretching is 2.5 times and the transverse stretching ratio is 3 times. After stretching is completed, traction is performed at a traction speed of 10 m / min, and the film is wound, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

[0040] The preparation method of the antibacterial modified graphene is the same as the preparation method of the antibacterial modified graphene in Example 1, and the preparation method of the antibacterial modified montmorillonite is the same as the preparation method of the antibacterial modified montmorillonite in Example 4. Example 8

[0041] A method for preparing an antibacterial polyethylene composite packaging film comprises the following steps: Step 1: melt-blend 68 parts of low-density polyethylene, 28 parts of polypropylene, 4.8 parts of antibacterial modified graphene, 0.4 parts of antioxidant, and 1.8 parts of compatibilizer maleic anhydride modified blend as the inner layer raw material, wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, the temperature of the inner layer melt blending is 175°C, the screw speed is 35r / min, and the inner layer melt is obtained; dry the ethylene-vinyl alcohol copolymer at 80°C for 4h, and mix 68 parts of high-density polyethylene, 32 parts of ethylene-vinyl alcohol as the intermediate layer raw materials, ... The copolymer, 0.9 parts of anti-blocking agent talc, and 3.5 parts of compatibilizer maleic anhydride grafted polyethylene were melt-blended, the temperature of the middle layer melt blending was 195°C, and the screw speed was 40r / min to obtain the middle layer melt; the nylon was dried at 80°C for 4h, and 60 parts of high-density polyethylene, 38 parts of metallocene polyethylene, 15 parts of nylon, 6 parts of antibacterial modified montmorillonite, and 4.5 parts of compatibilizer ethylene-ethyl acrylate copolymer were melt-blended by weight, the temperature of the outer layer melt blending was 215°C, and the screw speed was 42r / min to obtain the outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die. During the extrusion molding process, the die temperature is 195°C and the melt pressure is 21 MPa. After cooling by a chilled roller, biaxial stretching is performed. The longitudinal stretching ratio of the biaxial stretching is 3 times and the transverse stretching ratio is 3.5 times. After stretching is completed, traction is performed at a traction speed of 11 m / min, and the film is wound, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

[0042] The preparation method of the antibacterial modified graphene is the same as the preparation method of the antibacterial modified graphene in Example 2, and the preparation method of the antibacterial modified montmorillonite is the same as the preparation method of the antibacterial modified montmorillonite in Example 5. Example 9

[0043] A method for preparing an antibacterial polyethylene composite packaging film comprises the following steps: Step 1: melt-blend the inner layer raw materials of 75 parts of low-density polyethylene, 32 parts of polypropylene, 5.5 parts of antibacterial modified graphene, 0.5 parts of antioxidant, and 2.5 parts of compatibilizer maleic anhydride modified blend, by mass, wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1, the temperature of the inner layer melt blending is 180 ° C, the screw speed is 35r / min, and the inner layer melt is obtained; the ethylene-vinyl alcohol copolymer is dried at 80 ° C for 4h, and the intermediate layer raw materials of 72 parts of high-density polyethylene, 36 parts of ethylene-ethylene The alcohol copolymer, 0.9 parts of anti-blocking agent talc, and 4.5 parts of compatibilizer maleic anhydride grafted polyethylene were melt blended, the temperature of the middle layer melt blending was 200°C, and the screw speed was 40r / min to obtain the middle layer melt; the nylon was dried at 80°C for 4h, and 65 parts of high-density polyethylene, 42 parts of metallocene polyethylene, 20 parts of nylon, 8 parts of antibacterial modified montmorillonite, and 5 parts of compatibilizer ethylene-ethyl acrylate copolymer were melt blended by weight, the temperature of the outer layer melt blending was 225°C, and the screw speed was 42r / min to obtain the outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die. During the extrusion molding process, the die temperature is 195°C and the melt pressure is 21 MPa. After cooling by a chilled roller, biaxial stretching is performed. The longitudinal stretching ratio of the biaxial stretching is 3 times and the transverse stretching ratio is 3.5 times. After stretching is completed, traction is performed at a traction speed of 11 m / min, and the film is wound, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

[0044] The preparation method of the antibacterial modified graphene is the same as the preparation method of the antibacterial modified graphene in Example 2, and the preparation method of the antibacterial modified montmorillonite is the same as the preparation method of the antibacterial modified montmorillonite in Example 5. Example 10

[0045] A method for preparing an antibacterial polyethylene composite packaging film comprises the following steps: Step 1: melt-blend 80 parts of low-density polyethylene, 35 parts of polypropylene, 6 parts of antibacterial modified graphene, 0.6 parts of antioxidant, and 3 parts of compatibilizer maleic anhydride modified blend as the inner layer raw material, wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, the temperature of the inner layer melt blending is 185°C, the screw speed is 35r / min, and the inner layer melt is obtained; dry the ethylene-vinyl alcohol copolymer at 80°C for 4h, and mix 75 parts of high-density polyethylene, 40 parts of ethylene-vinyl alcohol as the intermediate layer raw materials, and 1010 and 168 as the compatibilizer, respectively. The copolymer, 1 part of anti-adhesive talc, and 5 parts of compatibilizer maleic anhydride grafted polyethylene were melt-blended, the temperature of the middle layer melt blending was 205°C, and the screw speed was 40r / min to obtain the middle layer melt; the nylon was dried at 80°C for 4h, and the outer layer raw materials 70 parts of high-density polyethylene, 45 parts of metallocene polyethylene, 25 parts of nylon, 10 parts of antibacterial modified montmorillonite, and 6 parts of compatibilizer ethylene-ethyl acrylate copolymer were melt-blended by mass, the temperature of the outer layer melt blending was 230°C, and the screw speed was 42r / min to obtain the outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die. During the extrusion molding process, the die temperature is 205°C and the melt pressure is 18 MPa. After cooling by a chilled roller, biaxial stretching is performed. The longitudinal stretching ratio of the biaxial stretching is 3.5 times and the transverse stretching ratio is 4 times. After stretching is completed, traction is performed at a traction speed of 12 m / min, and the film is wound, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

[0046] The preparation method of the antibacterial modified graphene is the same as the preparation method of the antibacterial modified graphene in Example 3, and the preparation method of the antibacterial modified montmorillonite is the same as the preparation method of the antibacterial modified montmorillonite in Example 6. Comparative Example 1

[0047] A method for preparing a polyethylene composite packaging film. Compared with Example 9, the antibacterial modified graphene prepared in Example 9 is replaced by 2 parts of graphene oxide and 3.5 parts of polyhexamethylene biguanide, and the remaining components and preparation method are exactly the same as those in Example 9. Comparative Example 2

[0048] A method for preparing a polyethylene composite packaging film. Compared with Example 9, the antibacterial modified montmorillonite prepared in Example 9 is replaced by nano-montmorillonite in equal amounts, and the remaining components and preparation method are completely consistent with Example 9. Comparative Example 3

[0049] A method for preparing a polyethylene composite packaging film. Compared with Example 9, the compatibilizer maleic anhydride-modified blend in the inner layer raw material and the ethylene-ethyl acrylate copolymer in the outer layer raw material in Example 9 are replaced with maleic anhydride-grafted polyethylene in equal amounts. The remaining components and preparation method are exactly the same as those in Example 9.

[0050] The preparation method of the compatibilizer maleic anhydride modified blend in the inner layer raw material in the examples and comparative examples of the present invention is as follows: 10g of polyethylene, 8g of polypropylene, 10mL of acetone, 1g of maleic anhydride and 0.2g of dicumyl peroxide are uniformly mixed, and after the acetone is volatilized, transferred to a twin-screw extruder and melt blended at 205°C. After the melt blending is completed, it is extruded and cooled to obtain a maleic anhydride modified blend.

[0051] The low-density polyethylene used in the examples of the present invention and the comparative examples was purchased from Sinopec Yangzi Petrochemical Co., Ltd., model 2426K; polypropylene was purchased from PetroChina Daqing Petrochemical Company, model T30S; graphene oxide is multilayer graphene oxide, purchased from Suzhou Hengqiu Technology Co., Ltd. (purity>95wt%, thickness of 3.4-8nm, and layer diameter of 10-50μm); polyhexamethylene biguanide was purchased from Shanghai Gaoju Biotechnology Co., Ltd.; high-density polyethylene was purchased from Sinopec Maoming Branch, brand 2200JP; ethylene-vinyl alcohol copolymer was purchased from Kuraray Co., Ltd. of Japan, model L171B; metallocene polyethylene was purchased from Dongguan Mingyuan Plastic Co., Ltd., brand Dow NG5401B; nylon was purchased from Sinopec Baling Petrochemical Co., Ltd., model YH800; nano-montmorillonite was purchased from Zhejiang Baina Chemical Co., Ltd., with a particle size of 50-100nm; other undisclosed reagents were all commercially available.

[0052] The polyethylene composite packaging films prepared in Examples 7-10 and Comparative Examples 1-3 were used as samples to conduct relevant performance tests. The test results are shown below: (1) Antibacterial performance test: The composite antibacterial film was cut into discs with a diameter of 6 mm, sterilized by ultraviolet light, and placed in a sterile container. The purified Escherichia coli and Staphylococcus aureus were inoculated in nutrient broth and cultured at 37°C for 12 h. The bacterial solution was diluted according to the proportion and evenly spread on a surface dish coated with agar. The solution was cultured in an incubator at 37°C for 24 h. After the culture was completed, the diameter of the inhibition zone was measured. (2) Mechanical properties test: The test method refers to GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for films and sheets". Each group of samples was tested three times, and the tensile strength and elongation at break of the composite film were recorded; The above test results are shown in Table 1; Table 1

[0053] As shown in the test results in Table 1, the polyethylene composite packaging films prepared in Examples 7-10 have excellent antibacterial efficacy and mechanical properties. The sample corresponding to Example 9 has an inhibition zone diameter of 12.9 mm against Escherichia coli and 11.6 mm against Staphylococcus aureus, a tensile strength of 52.4 MPa, and an elongation at break of 432.9%. In Comparative Example 1, graphene oxide was modified, while in Comparative Example 2, nano-montmorillonite was not modified. This reduced the dispersibility of the two films, resulting in poor compatibility with the substrate and reduced mechanical properties. Although polyhexamethylene biguanide was directly added to Comparative Example 1, graphene oxide aggregates when in contact with bacteria, resulting in a loss of active surface area and limiting activity, leading to a decrease in antibacterial efficacy. In Comparative Example 2, quaternary ammonium salts were not introduced into the nano-montmorillonite, resulting in reduced antibacterial performance. In Comparative Example 3, the same compatibilizer was used, resulting in poor substrate compatibility and reduced overall performance.

[0054] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. An antibacterial polyethylene composite packaging film, comprising an inner layer, an intermediate layer, and an outer layer, characterized in that: In parts by mass, the raw materials of the inner layer include 60-80 parts of low-density polyethylene, 25-35 parts of polypropylene, 4-6 parts of modified filler, 0.3-0.6 parts of antioxidant, and 1-3 parts of compatibilizer; the middle layer includes 62-75 parts of high-density polyethylene, 28-40 parts of ethylene-vinyl alcohol copolymer, 0.8-1 parts of anti-adhesive agent, and 2-5 parts of compatibilizer; the outer layer includes 55-70 parts of high-density polyethylene, 35-45 parts of metallocene polyethylene, 12-25 parts of nylon, 4-10 parts of antibacterial modified montmorillonite, and 3-6 parts of compatibilizer; The modified filler in the inner layer raw material is antibacterial modified graphene, which is obtained by reacting carboxylated graphene with polyhexamethylene biguanide; The compatibilizer in the inner layer raw material is a maleic anhydride modified blend, and the maleic anhydride modified blend is a maleic anhydride modified polyethylene and polypropylene blend; The compatibilizer in the intermediate layer raw material is maleic anhydride grafted polyethylene; The compatibilizer in the outer layer raw material is ethylene-ethyl acrylate copolymer.

2. The antibacterial polyethylene composite packaging film according to claim 1, characterized in that: The preparation method of the antibacterial modified graphene comprises the following steps: S1. Ultrasonic dispersion of graphene oxide in deionized water to obtain a suspension after uniform dispersion, addition of sodium hydroxide and chloroacetic acid, water bath ultrasonication, filtration, washing, and drying to obtain carboxylated graphene; S2. Ultrasonic dispersion of carboxylated graphene in N,N-dimethylformamide. After uniform dispersion, polyhexamethylene biguanide, 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and N,N-diisopropylethylamine are added, and the mixture is heated to react. After the reaction is completed, the mixture is filtered, washed, and dried to obtain antibacterial modified graphene.

3. The antibacterial polyethylene composite packaging film according to claim 2, characterized in that: The addition ratio of carboxylated graphene, N,N-dimethylformamide, polyhexamethylene biguanide, 2-(7-azobenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate, and N,N-diisopropylethylamine in S2 is 1 g: 400-450 mL: 1.2-2 g: 0.35-0.4 g: 0.2-0.25 g.

4. The antibacterial polyethylene composite packaging film according to claim 2, characterized in that: The reaction temperature in S2 is 95-105° C., and the reaction time is 8-12 h.

5. The antibacterial polyethylene composite packaging film according to claim 1, characterized in that: The preparation method of the antibacterial modified montmorillonite comprises the following steps: Step (1), ultrasonically dispersing the nano-montmorillonite into an ethanol solution, adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane after uniform dispersion, adjusting the pH to 4-5 with glacial acetic acid, heating, reacting, filtering, washing, and drying after the reaction is completed to obtain epoxidized montmorillonite; Step (2), ultrasonically dispersing the epoxidized montmorillonite in deionized water, adding 5-aminopentyl-dimethyl-amine after uniform dispersion, stirring and mixing, reacting, filtering, washing with deionized water, and drying to obtain modified montmorillonite; Step (3), ultrasonically dispersing the modified montmorillonite in deionized water, adding vinylbenzyl chloride and hydrochloric acid after the reaction is uniform, condensing and refluxing, reacting, centrifuging, washing, and drying after the reaction is completed to obtain the antibacterial modified montmorillonite.

6. The antibacterial polyethylene composite packaging film according to claim 5, characterized in that: In step (2), the addition ratio of epoxidized montmorillonite, deionized water, and 5-aminopentyl-dimethyl-amine is 10 g:480-600 mL:15-21 g, the reaction temperature is 20-35° C., and the reaction time is 18-24 h.

7. The antibacterial polyethylene composite packaging film according to claim 5, characterized in that: In step (3), the addition ratio of modified montmorillonite, deionized water, vinylbenzyl chloride, and hydrochloric acid is 10 g:750-950 mL:5-8 g:1.5-2 g, the reaction temperature is 80-95° C., and the reaction time is 6-9 h.

8. A method for preparing an antibacterial polyethylene composite packaging film according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: melt-blending the inner layer raw materials of low-density polyethylene, polypropylene, modified filler, antioxidant, and compatibilizer to obtain an inner layer melt; drying the ethylene-vinyl alcohol copolymer at 80°C for 4 hours, and melt-blending the middle layer raw materials of high-density polyethylene, ethylene-vinyl alcohol copolymer, anti-adhesive agent, and compatibilizer to obtain an middle layer melt; drying the nylon at 80°C for 4 hours, and melt-blending the outer layer raw materials of high-density polyethylene, metallocene polyethylene, nylon, antibacterial modified montmorillonite, and compatibilizer to obtain an outer layer melt; Step 2: The inner layer melt, the middle layer melt, and the outer layer melt are extruded into shape by a three-layer co-extrusion composite die head, cooled by a chilled roller, and then biaxially stretched. After the stretching is completed, the film is pulled, rolled, slit, and allowed to stand at a constant temperature of 40°C for 24 hours to obtain an antibacterial polyethylene composite packaging film.

9. The method for preparing an antibacterial polyethylene composite packaging film according to claim 8, characterized in that: In the step 1, the inner layer, the middle layer and the outer layer are melt-blended in a three-layer co-extrusion film blowing machine, the temperature of the inner layer melt-blending is 165-185°C, the screw speed is 35r / min, the temperature of the middle layer melt-blending is 190-205°C, the screw speed is 40r / min, and the temperature of the outer layer melt-blending is 210-230°C, and the screw speed is 42r / min.

10. The method for preparing an antibacterial polyethylene composite packaging film according to claim 8, characterized in that: During the extrusion molding process in step 2, the die temperature is 185-205° C., the melt pressure is 18-25 MPa, the biaxial stretching longitudinal stretching ratio is 2.5-3.5 times, the transverse stretching ratio is 3-4 times, and the pulling speed is 10-12 m / min.

Images