Antibacterial fresh-keeping packaging film for food packaging and preparation method of antibacterial fresh-keeping packaging film

Abstract

The invention relates to the technical field of food packaging, in particular to an antibacterial fresh-keeping packaging film for food packaging and a preparation method of the antibacterial fresh-keeping packaging film, and aims at solving the problems that a traditional food packaging film is insufficient in antibacterial performance and not ideal in fresh-keeping effect. According to the preparation method, polyethylene resin and polylactic resin are taken as main raw materials, so that the packaging film is endowed with excellent mechanical property and barrier property, the oxidation process of food can be slowed down, the damage of oxygen to the food is reduced, the loss of nutritional ingredients in the food is prevented, and the freshness and nutritional ingredients of the food can be effectively kept; the modified nano-silver particles are added into the food, so that the growth and metabolic activities of microorganisms such as various bacteria and molds can be effectively inhibited, the risk that the food is polluted by the microorganisms is remarkably reduced, the deterioration of the food due to microbial decomposition is avoided, and the food quality is improved. Therefore, the quality and taste of the food are better maintained, and the shelf life of the food is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of food packaging, and in particular to an antibacterial fresh-keeping packaging film for food packaging and a preparation method thereof. Background Art

[0002] With the improvement of living standards, people have higher and higher requirements for food safety and freshness. Although traditional food packaging materials, such as polyethylene, polypropylene and other plastic films, have certain barrier properties and can effectively isolate the external environment and delay food spoilage to a certain extent, their antibacterial properties are limited and it is difficult to effectively inhibit the growth of microorganisms, which can easily lead to food spoilage.

[0003] How to improve the traditional food packaging film often has the shortcomings of insufficient antibacterial performance and unsatisfactory preservation effect, which cannot meet the needs of modern food packaging. Therefore, it is of great practical significance to develop an antibacterial fresh-keeping packaging film for food packaging and its preparation method. Summary of the invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide an antibacterial fresh-keeping packaging film for food packaging and a preparation method thereof: the antibacterial fresh-keeping packaging film for food packaging is obtained by uniformly mixing polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate, then melt-extruding through a twin-screw extruder, and blow-molding into a film through a blow molding machine, thereby solving the problem that traditional food packaging films often have insufficient antibacterial properties and unsatisfactory fresh-keeping effects, and cannot meet the needs of modern food packaging.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An antibacterial fresh-keeping packaging film for food packaging comprises the following components in parts by weight:

[0007] 80-90 parts of polyethylene resin, 30-40 parts of polylactic acid resin, 0.05-0.25 parts of modified nano silver particles and 1-3 parts of calcium stearate;

[0008] Wherein, the modified nano silver particles are prepared by the following steps:

[0009] Step a1: adding sodium alginate and deionized water into a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stirring and reacting for 10-15 minutes at a temperature of 20-25° C. and a stirring rate of 300-400 r / min, then adding silver nitrate solution dropwise while stirring, controlling the dropping rate to 1-2 drops / s, adding glucose after the dropwise addition and continuing to stir and react for 3-5 hours under the condition of heating to 60-70° C., cooling the reaction product to room temperature after the reaction is completed, then centrifuging, washing the precipitate with anhydrous ethanol for 2-3 times, then placing it in a vacuum drying oven, and drying it at a temperature of 40-50° C. for 2-3 hours to obtain nano silver particles;

[0010] Step a2: Add the performance enhancement modifier, ethanol solution and N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, stir and react for 20-30 minutes at a temperature of 20-25° C. and a stirring rate of 300-400 r / min, then adjust the pH to 4-5 with a hydrochloric acid solution, then add nanosilver particles and continue stirring and reacting for 5-6 hours under the condition of heating to 80-85° C. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with anhydrous ethanol for 2-3 times, and then placed in a vacuum drying oven and dried at a temperature of 40-50° C. for 6-8 hours to obtain modified nanosilver particles.

[0011] As a further solution of the present invention: the dosage ratio of the sodium alginate, deionized water, silver nitrate solution and glucose in step a1 is 0.1-0.2 g: 20-25 mL: 8-10 mL: 0.5-1.5 g.

[0012] As a further solution of the present invention: the molar concentration of the silver nitrate solution in step a1 is 0.1-0.2 mol / L.

[0013] As a further solution of the present invention: the usage ratio of the performance enhancing modifier, ethanol solution, N,N-dimethylformamide and nano-silver particles in step a2 is 0.5-3.5 g: 50-55 mL: 20-25 mL: 1 g.

[0014] As a further solution of the present invention: the volume fraction of the ethanol solution in step a2 is 85-90%; the mass fraction of the hydrochloric acid solution is 15-20%.

[0015] As a further solution of the present invention: the performance enhancing modifier is prepared by the following steps:

[0016] Step b1: adding perylene anhydride and concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stirring the reaction for 10-15 minutes at a temperature of 20-25° C. and a stirring rate of 300-400 r / min, then heating to 40-45° C. and continuing to stir the reaction for 4-5 hours, then adding iodine and adding liquid bromine dropwise while stirring, controlling the dropping rate to 1-2 drops / s, and heating to 100-110° C. after the dropwise addition is completed, and continuing to stir the reaction for 25-30 hours. After the reaction is completed, the reaction product is cooled to room temperature, then added to ice water, allowed to stand to precipitate, then vacuum filtered, and the filter cake is purified by silica gel column chromatography using a mixed solvent to obtain intermediate 1;

[0017] Step b2: Add intermediate 1, tributylphosphine and N,N-dimethylacetamide into a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, introduce nitrogen protection, stir the reaction at a temperature of 20-25° C. and a stirring rate of 300-400 r / min for 20-30 min, then heat to 130-140° C. and continue stirring the reaction for 8-10 h. After the reaction is completed, cool the reaction product to room temperature, and then remove the solvent by rotary evaporation to obtain intermediate 2;

[0018] Step b3: Add intermediate 2, ethanolamine and N,N-dimethylacetamide to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, introduce nitrogen protection, stir the reaction at a temperature of 20-25°C and a stirring rate of 300-400r / min for 20-30min, then heat to 90-100°C and continue stirring the reaction for 5-6h. After the reaction is completed, cool the reaction product to room temperature, then rotary evaporate to remove the solvent, then wash with anhydrous ethanol 2-3 times, then place in a vacuum drying oven, and dry at a temperature of 50-60°C for 3-5h to obtain intermediate 3;

[0019] Step b4: Add intermediate 3, 3-chloropropyltrimethoxysilane, anhydrous potassium carbonate, potassium iodide and anhydrous toluene to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, introduce nitrogen protection, stir the reaction for 10-20 minutes at a temperature of -5-0°C and a stirring rate of 300-400r / min, then heat the temperature to 80-90°C and continue stirring the reaction for 10-12 hours. After the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtered, and the filtrate is rotary evaporated to remove the solvent, and then placed in a vacuum drying oven and dried at a temperature of 50-60°C for 3-5 hours to obtain a performance enhancing modifier.

[0020] As a further solution of the present invention: the usage ratio of the perylene anhydride, concentrated sulfuric acid, iodine and liquid bromine in step b1 is 1 g: 40-50 mL: 0.05-0.1 g: 2-3 g.

[0021] As a further solution of the present invention: the mass fraction of the concentrated sulfuric acid in step b1 is 98%, and the mixed solvent is formed by mixing n-hexane and dichloromethane in an equal mass ratio.

[0022] As a further scheme of the present invention: the usage ratio of the intermediate 1, tributylphosphine and N,N-dimethylacetamide in step b2 is 10 mmol:40 mmol:40-50 mL.

[0023] As a further solution of the present invention: the usage ratio of the intermediate 2, ethanolamine and N,N-dimethylacetamide in step b3 is 10 mmol:30-35 mmol:60-80 mL.

[0024] As a further scheme of the present invention: the usage ratio of the intermediate 3, 3-chloropropyltrimethoxysilane, anhydrous potassium carbonate, potassium iodide and anhydrous toluene in step b4 is 10 mmol: 22-25 mmol: 30-35 mmol: 1.2-2.4 g: 100-120 mL.

[0025] As a further solution of the present invention: a method for preparing an antibacterial fresh-keeping packaging film for food packaging comprises the following steps:

[0026] Step 1: Weigh 80-90 parts of polyethylene resin, 30-40 parts of polylactic acid resin, 0.05-0.25 parts of modified nano silver particles and 1-3 parts of calcium stearate according to weight, and set aside;

[0027] Step 2: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050±0.002mm.

[0028] As a further solution of the present invention: the model of the polyethylene resin is LDPE 2426H; the model of the polylactic acid resin is PLA 4043D.

[0029] Beneficial effects of the present invention:

[0030] The invention discloses an antibacterial fresh-keeping packaging film for food packaging and a preparation method thereof. The antibacterial fresh-keeping packaging film for food packaging is prepared by uniformly mixing polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate, then melting and extruding through a twin-screw extruder, and blowing into a film through a blow molding machine. The preparation method uses polyethylene resin and polylactic acid resin as main raw materials, and gives the packaging film excellent mechanical properties and barrier properties, which can slow down the oxidation process of food, reduce the damage of oxygen to food, prevent the loss of nutrients in food, and effectively maintain the freshness and nutrients of food, thereby better maintaining the quality and taste of food, and will not cause pollution to food. After adding modified nano silver particles thereto, the growth and metabolic activities of microorganisms such as various bacteria and molds can be more effectively inhibited, and the risk of food being contaminated by microorganisms is significantly reduced, and food is prevented from being deteriorated due to microbial decomposition, thereby better maintaining the quality and taste of food, and extending the shelf life of food. Moreover, the packaging film has a wide range of application prospects and is suitable for the packaging of various foods, such as meat, vegetables, fruits, etc.

[0031] In the process of preparing the antibacterial fresh-keeping packaging film for food packaging, a modified nano silver particle is first prepared, and perylene anhydride and liquid bromine are used to react. The liquid bromine is used as a brominating agent to introduce bromine atoms to the benzene ring of perylene anhydride to obtain intermediate 1. Then, intermediate 1 and tributylphosphine are reacted. The bromine atom on intermediate 1 reacts with tributylphosphine to form a quaternary phosphonium group to obtain intermediate 2. Then, intermediate 2 and ethanolamine are reacted. The anhydride group on intermediate 2 reacts with the amino group on ethanolamine to form a perylene imide structure, and a hydroxyl group is introduced at the same time to obtain intermediate 3. Then, intermediate 3 and 3-chloropropyltrimethoxysilane are reacted. The hydroxyl group on intermediate 3 reacts with the chlorine atom on 3-chloropropyltrimethoxysilane to introduce a large number of siloxane groups to obtain a performance enhancement modifier. Then, sodium alginate is used as a protective agent, and glucose is used as a reducing agent to reduce silver ions in a silver nitrate solution into nano silver particles. Then, the nano silver particles are treated with the performance enhancement modifier. Siloxane groups are hydrolyzed to form silanols which are grafted onto the particle surface of nanosilver particles to obtain modified nanosilver particles. The modified nanosilver particles use nanosilver particles as "cores". The nanosilver particles can release silver ions, which can be effectively adsorbed on the cell walls of bacteria, increase the osmotic pressure of the cells, and combine with bacterial proteins or enzymes, thereby causing bacterial death without causing drug resistance. The particles are reusable and have excellent long-term antibacterial properties. After being treated with a performance-enhancing modifier, an organic "shell" can be wrapped around the outside of the "core" to improve the dispersibility of the nanosilver particles, making it difficult to agglomerate and evenly distributed in the packaging film, and significantly improving the antibacterial properties. At the same time, a large number of quaternary phosphonium groups are introduced, which can also be effectively adsorbed on the cell walls of bacteria, further enhancing the antibacterial activity of the nanosilver particles, enabling them to more effectively inhibit the growth of a variety of microorganisms such as bacteria and molds, significantly reducing the risk of food being contaminated by microorganisms and extending the shelf life of food. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1:

[0034] This embodiment is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0035] Step S1: 1 g of perylene anhydride and 40 mL of 98% concentrated sulfuric acid are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction at a temperature of 20° C. and a stirring rate of 300 r / min for 10 min, and then the mixture is heated to 40° C. and the stirring reaction is continued for 4 h, and then 0.05 g of iodine is added and 2 g of liquid bromine is added dropwise while stirring, and the dropping rate is controlled to be 1 drop / s. After the addition is completed, the mixture is heated to 100° C. and the stirring reaction is continued for 25 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to ice water, and the precipitate is allowed to stand, and then vacuum filtered. The filter cake is purified by silica gel column chromatography using a mixed solvent prepared by mixing n-hexane and dichloromethane in an equal mass ratio to obtain an intermediate 1;

[0036] Step S2: 10 mmol of intermediate 1, 40 mmol of tributylphosphine and 40 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at a temperature of 20° C. and a stirring rate of 300 r / min for 20 min, and then the temperature was raised to 130° C. and the stirring reaction was continued for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0037] Step S3: 10 mmol of intermediate 2, 30 mmol of ethanolamine and 60 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 20°C and a stirring rate of 300 r / min for 20 min, and then the mixture was heated to 90°C and stirred for 5 h. After the reaction, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 50°C for 3 h to obtain intermediate 3;

[0038] Step S4: 10 mmol of intermediate 3, 22 mmol of 3-chloropropyltrimethoxysilane, 30 mmol of anhydrous potassium carbonate, 1.2 g of potassium iodide and 100 mL of anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The reaction was stirred at a temperature of -5°C and a stirring rate of 300 r / min for 10 minutes, and then the temperature was raised to 80°C and the stirring reaction was continued for 10 hours. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, the filtrate was rotary evaporated to remove the solvent, and then placed in a vacuum drying oven and dried at a temperature of 50°C for 3 hours to obtain a performance enhancement modifier;

[0039] Step S5: 0.1 g of sodium alginate and 20 mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction at a temperature of 20° C. and a stirring rate of 300 r / min for 10 min, and then 8 mL of a silver nitrate solution with a molar concentration of 0.1 mol / L is added dropwise while stirring, and the dropping rate is controlled to be 1 drop / s. After the addition is completed, 0.5 g of glucose is added and the mixture is heated to 60° C. and stirred for reaction for 3 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at a temperature of 40° C. for 2 h to obtain nanosilver particles;

[0040] Step S6: 0.5 g of a performance enhancing modifier, 50 mL of an ethanol solution with a volume fraction of 85%, and 20 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 20° C. and a stirring rate of 300 r / min for 20 min, and then adjusted to pH 4 with a hydrochloric acid solution with a mass fraction of 15%, and then 1 g of nanosilver particles were added and the temperature was raised to 80° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature and then centrifuged. The precipitate was washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at a temperature of 40° C. for 6 h to obtain modified nanosilver particles;

[0041] Step S7: weighing 80 parts of polyethylene resin with a model number of LDPE 2426H, 30 parts of polylactic acid resin with a model number of PLA 4043D, 0.05 parts of modified nano silver particles and 1 part of calcium stearate according to weight parts for later use;

[0042] Step S8: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0043] Embodiment 2:

[0044] This embodiment is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0045] Step S1: 1 g of perylene anhydride and 45 mL of 98% concentrated sulfuric acid are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred at 22° C. and a stirring rate of 350 r / min for 12 min, and then the mixture is heated to 42° C. and the stirring reaction is continued for 4.5 h. Then, 0.08 g of iodine is added and 2.5 g of liquid bromine is added dropwise while stirring, and the dropping rate is controlled to be 1 drop / s. After the addition is completed, the mixture is heated to 105° C. and the stirring reaction is continued for 28 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to ice water, and the mixture is allowed to stand to precipitate, and then vacuum filtered. The filter cake is purified by silica gel column chromatography using a mixed solvent prepared by mixing n-hexane and dichloromethane in an equal mass ratio to obtain an intermediate 1.

[0046] Step S2: 10 mmol of intermediate 1, 40 mmol of tributylphosphine and 45 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 22° C. and a stirring rate of 350 r / min for 25 min, and then the mixture was heated to 135° C. and stirred for 9 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0047] Step S3: 10 mmol of intermediate 2, 32 mmol of ethanolamine and 70 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 22°C and a stirring rate of 350 r / min for 25 min, and then the mixture was heated to 95°C and stirred for 5.5 h. After the reaction, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 55°C for 4 h to obtain intermediate 3;

[0048] Step S4: 10 mmol of intermediate 3, 24 mmol of 3-chloropropyltrimethoxysilane, 32 mmol of anhydrous potassium carbonate, 1.8 g of potassium iodide and 110 mL of anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The reaction was stirred for 15 minutes at a temperature of -3°C and a stirring rate of 350 r / min, and then the temperature was raised to 85°C and the stirring reaction was continued for 11 hours. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, the filtrate was rotary evaporated to remove the solvent, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 4 hours to obtain a performance enhancement modifier;

[0049] Step S5: 0.15 g of sodium alginate and 22 mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction for 12 min at a temperature of 22° C. and a stirring rate of 350 r / min, and then 9 mL of a silver nitrate solution with a molar concentration of 0.15 mol / L is added dropwise while stirring, and the dropping rate is controlled to be 1 drop / s. After the addition is completed, 1 g of glucose is added and the mixture is heated to 65° C. and the stirring reaction is continued for 4 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at a temperature of 45° C. for 2.5 h to obtain nanosilver particles;

[0050] Step S6: 2 g of a performance enhancing modifier, 52 mL of an ethanol solution with a volume fraction of 88%, and 22 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 22° C. and a stirring rate of 350 r / min for 25 min, and then adjusted to a pH of 4.5 with a hydrochloric acid solution with a mass fraction of 18%, and then 1 g of nanosilver particles was added and the temperature was raised to 82° C. and the stirring reaction was continued for 5.5 h. After the reaction was completed, the reaction product was cooled to room temperature and then centrifuged. The precipitate was washed twice with anhydrous ethanol, and then placed in a vacuum drying oven and dried at a temperature of 45° C. for 7 h to obtain modified nanosilver particles;

[0051] Step S7: weighing 85 parts of polyethylene resin with a model number of LDPE 2426H, 35 parts of polylactic acid resin with a model number of PLA 4043D, 0.15 parts of modified nano silver particles and 2 parts of calcium stearate according to weight parts for later use;

[0052] Step S8: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0053] Embodiment 3:

[0054] This embodiment is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0055] Step S1: 1 g of perylene anhydride and 50 mL of 98% concentrated sulfuric acid are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction at a temperature of 25° C. and a stirring rate of 400 r / min for 15 min, and then the mixture is heated to 45° C. and the stirring reaction is continued for 5 h, and then 0.1 g of iodine is added and 3 g of liquid bromine is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the dropwise addition is completed, the mixture is heated to 110° C. and the stirring reaction is continued for 30 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to ice water, and the precipitate is allowed to stand, and then vacuum filtered. The filter cake is purified by silica gel column chromatography using a mixed solvent prepared by mixing n-hexane and dichloromethane in an equal mass ratio to obtain intermediate 1;

[0056] Step S2: 10 mmol of intermediate 1, 40 mmol of tributylphosphine and 50 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 140° C. and the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0057] Step S3: 10 mmol of intermediate 2, 35 mmol of ethanolamine and 80 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred for reaction at 25°C and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 100°C and stirred for reaction for 6 h. After the reaction, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at 60°C for 5 h to obtain intermediate 3;

[0058] Step S4: 10 mmol of intermediate 3, 25 mmol of 3-chloropropyltrimethoxysilane, 35 mmol of anhydrous potassium carbonate, 2.4 g of potassium iodide and 120 mL of anhydrous toluene are added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen is introduced for protection. The reaction is stirred for 20 minutes at a temperature of 0°C and a stirring rate of 400 r / min, and then the temperature is raised to 90°C and the stirring reaction is continued for 12 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, the filtrate is rotary evaporated to remove the solvent, and then placed in a vacuum drying oven and dried at a temperature of 60°C for 5 hours to obtain a performance enhancement modifier;

[0059] Step S5: 0.2 g of sodium alginate and 25 mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction for 15 min at a temperature of 25° C. and a stirring rate of 400 r / min, and then 10 mL of a silver nitrate solution with a molar concentration of 0.2 mol / L is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the addition is completed, 1.5 g of glucose is added and the mixture is heated to 70° C. and stirred for reaction for 5 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed 3 times with anhydrous ethanol, and then placed in a vacuum drying oven and dried at a temperature of 50° C. for 3 h to obtain nanosilver particles;

[0060] Step S6: 3.5 g of a performance enhancement modifier, 55 mL of an ethanol solution with a volume fraction of 90%, and 25 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 25° C. and a stirring rate of 400 r / min for 30 min, and then adjusted to pH 5 with a 20% hydrochloric acid solution, and then added 1 g of nanosilver particles and continued to stir and react for 6 h under the condition of heating to 85° C. After the reaction was completed, the reaction product was cooled to room temperature and then centrifuged, and the precipitate was washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 50° C. for 8 h to obtain modified nanosilver particles;

[0061] Step S7: weighing 90 parts of polyethylene resin with a model number of LDPE 2426H, 40 parts of polylactic acid resin with a model number of PLA 4043D, 0.25 parts of modified nano silver particles and 3 parts of calcium stearate according to weight parts for later use;

[0062] Step S8: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0063] Comparative Example 1:

[0064] This comparative example is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0065] Step S1: weigh 90 parts of polyethylene resin with a model number of LDPE 2426H, 40 parts of polylactic acid resin with a model number of PLA 4043D, and 3 parts of calcium stearate according to weight parts, and set them aside;

[0066] Step S2: The polyethylene resin, the polylactic acid resin and the calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0067] Comparative Example 2:

[0068] This comparative example is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0069] Step S1: 0.2 g of sodium alginate and 25 mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction for 15 min at a temperature of 25° C. and a stirring rate of 400 r / min, and then 10 mL of a silver nitrate solution with a molar concentration of 0.2 mol / L is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the addition is completed, 1.5 g of glucose is added and the mixture is heated to 70° C. and stirred for reaction for 5 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 50° C. for 3 h to obtain nanosilver particles;

[0070] Step S2: weighing 90 parts of polyethylene resin with a model number of LDPE 2426H, 40 parts of polylactic acid resin with a model number of PLA 4043D, 0.25 parts of nano silver particles and 3 parts of calcium stearate according to weight parts for later use;

[0071] Step S3: The polyethylene resin, polylactic acid resin, nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0072] Comparative Example 3:

[0073] This comparative example is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0074] Step S1: 1 g of perylene anhydride and 50 mL of 98% concentrated sulfuric acid are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction at a temperature of 25° C. and a stirring rate of 400 r / min for 15 min, and then the mixture is heated to 45° C. and the stirring reaction is continued for 5 h, and then 0.1 g of iodine is added and 3 g of liquid bromine is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the dropwise addition is completed, the mixture is heated to 110° C. and the stirring reaction is continued for 30 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to ice water, and the precipitate is allowed to stand, and then vacuum filtered. The filter cake is purified by silica gel column chromatography using a mixed solvent prepared by mixing n-hexane and dichloromethane in an equal mass ratio to obtain intermediate 1;

[0075] Step S2: 10 mmol of intermediate 1, 40 mmol of tributylphosphine and 50 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 140° C. and the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0076] Step S3: 10 mmol of intermediate 2, 35 mmol of ethanolamine and 80 mL of N, N-dimethylacetamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred for reaction at 25°C and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 100°C and stirred for reaction for 6 h. After the reaction, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at 60°C for 5 h to obtain intermediate 3;

[0077] Step S4: 10 mmol of intermediate 3, 25 mmol of 3-chloropropyltrimethoxysilane, 35 mmol of anhydrous potassium carbonate, 2.4 g of potassium iodide and 120 mL of anhydrous toluene are added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen is introduced for protection. The reaction is stirred for 20 minutes at a temperature of 0°C and a stirring rate of 400 r / min, and then the temperature is raised to 90°C and the stirring reaction is continued for 12 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, the filtrate is rotary evaporated to remove the solvent, and then placed in a vacuum drying oven and dried at a temperature of 60°C for 5 hours to obtain a performance enhancement modifier;

[0078] Step S5: weighing 90 parts of polyethylene resin with a model number of LDPE 2426H, 40 parts of polylactic acid resin with a model number of PLA 4043D, 0.25 parts of a performance enhancing modifier and 3 parts of calcium stearate according to weight parts for later use;

[0079] Step S6: The polyethylene resin, polylactic acid resin, performance enhancing modifier and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0080] Comparative Example 4:

[0081] This comparative example is a method for preparing an antibacterial fresh-keeping packaging film for food packaging, comprising the following steps:

[0082] Step S1: 0.2 g of sodium alginate and 25 mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and the mixture is stirred for reaction for 15 min at a temperature of 25° C. and a stirring rate of 400 r / min, and then 10 mL of a silver nitrate solution with a molar concentration of 0.2 mol / L is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the addition is completed, 1.5 g of glucose is added and the mixture is heated to 70° C. and stirred for reaction for 5 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 50° C. for 3 h to obtain nanosilver particles;

[0083] Step S2: 3.5 g of 3-chloropropyltrimethoxysilane, 55 mL of 90% ethanol solution by volume, and 25 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 25° C. and a stirring rate of 400 r / min for 30 min, and then adjusted to pH 5 with a 20% hydrochloric acid solution by mass, and then 1 g of nanosilver particles was added and the temperature was raised to 85° C. and the stirring reaction was continued for 6 h. After the reaction was completed, the reaction product was cooled to room temperature and then centrifuged. The precipitate was washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 50° C. for 8 h to obtain modified nanosilver particles;

[0084] Step S3: weighing 90 parts of polyethylene resin with a model number of LDPE 2426H, 40 parts of polylactic acid resin with a model number of PLA 4043D, 0.25 parts of modified nano silver particles and 3 parts of calcium stearate according to weight parts for later use;

[0085] Step S4: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050 mm.

[0086] The antibacterial fresh-keeping packaging films for food packaging of Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the test results are shown in the following table:

[0087]

[0088] Among them, the antibacterial performance is tested by the antibacterial fresh-keeping packaging film for food packaging being left to stand at room temperature for 10 days, then washed and dried, and then its antibacterial rate is tested.

[0089] Among them, the preservation performance is to peel and wash the whole fresh pineapple under sterile conditions, cut it into equal-sized pieces and divide it into 7 parts, then fully cover it with antibacterial preservation packaging film for food packaging, move it to a 4°C refrigerator for refrigeration, and measure the total number of colonies before coating, the total number of colonies after 7 days of coating, and the weight loss rate after 7 days.

[0090] Referring to the data in the above table, it can be known that the antibacterial fresh-keeping packaging film for food packaging of the present application has excellent antibacterial and antimicrobial properties and food preservation properties.

[0091] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0092] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined in this application, they shall all fall within the protection scope of the present invention.

Claims

1. An antibacterial fresh-keeping packaging film for food packaging, characterized in that: It includes the following components by weight: 80-90 parts of polyethylene resin, 30-40 parts of polylactic acid resin, 0.05-0.25 parts of modified nano silver particles and 1-3 parts of calcium stearate; Wherein, the modified nano silver particles are prepared by the following steps: Step a1: Sodium alginate and deionized water are stirred for reaction, and then silver nitrate solution is added dropwise while stirring, and glucose is added after the addition is completed and the stirring reaction is continued. After the reaction is completed, the reaction product is cooled, and then centrifuged, and the precipitate is washed and dried to obtain nano silver particles; Step a2: Stirring the performance enhancement modifier, ethanol solution and N,N-dimethylformamide for reaction, then adjusting the pH with hydrochloric acid solution, then adding nanosilver particles and continuing to stir the reaction, cooling the reaction product after the reaction is completed, then centrifuging, washing and drying the precipitate to obtain modified nanosilver particles.

2. The antibacterial fresh-keeping packaging film for food packaging according to claim 1, characterized in that: The dosage ratio of the sodium alginate, deionized water, silver nitrate solution and glucose in step a1 is 0.1-0.2 g: 20-25 mL: 8-10 mL: 0.5-1.5 g; the molar concentration of the silver nitrate solution is 0.1-0.2 mol / L.

3. The antibacterial fresh-keeping packaging film for food packaging according to claim 1, characterized in that: The usage ratio of the performance enhancing modifier, ethanol solution, N,N-dimethylformamide and nano-silver particles in step a2 is 0.5-3.5 g: 50-55 mL: 20-25 mL: 1 g; the volume fraction of the ethanol solution is 85-90%; and the mass fraction of the hydrochloric acid solution is 15-20%.

4. The antibacterial fresh-keeping packaging film for food packaging according to claim 1, characterized in that: The performance enhancing modifier is prepared by the following steps: Step b1: stirring perylene anhydride and concentrated sulfuric acid for reaction, then adding iodine and adding liquid bromine dropwise while stirring, continuing to stir the reaction after the addition is complete, cooling the reaction product after the reaction is complete, then adding it to ice water, standing to precipitate, then vacuum filtering, and purifying the filter cake by silica gel column chromatography with a mixed solvent to obtain intermediate 1; Step b2: stirring the intermediate 1, tributylphosphine and N,N-dimethylacetamide to react, cooling the reaction product after the reaction is completed, and then rotary evaporating to obtain the intermediate 2; Step b3: stirring the intermediate 2, ethanolamine and N,N-dimethylacetamide to react, cooling the reaction product after the reaction is completed, then rotary evaporating, then washing and drying to obtain the intermediate 3; Step b4: Stir and react the intermediate 3, 3-chloropropyltrimethoxysilane, anhydrous potassium carbonate, potassium iodide and anhydrous toluene. After the reaction is completed, cool the reaction product, then vacuum filter it, rotary evaporate the filtrate, and then dry it to obtain a performance enhancing modifier.

5. The antibacterial fresh-keeping packaging film for food packaging according to claim 4, characterized in that: The usage ratio of the perylene anhydride, concentrated sulfuric acid, iodine and liquid bromine in step b1 is 1g:40-50mL:0.05-0.1g:2-3g; the mass fraction of the concentrated sulfuric acid is 98%, and the mixed solvent is formed by mixing n-hexane and dichloromethane in equal mass ratios.

6. The antibacterial fresh-keeping packaging film for food packaging according to claim 4, characterized in that: The usage ratio of the intermediate 1, tributylphosphine and N,N-dimethylacetamide in step b2 is 10mmol:40mmol:40-50mL.

7. The antibacterial fresh-keeping packaging film for food packaging according to claim 4, characterized in that: The usage ratio of the intermediate 2, ethanolamine and N,N-dimethylacetamide in step b3 is 10 mmol: 30-35 mmol: 60-80 mL.

8. The antibacterial fresh-keeping packaging film for food packaging according to claim 4, characterized in that: The usage ratio of the intermediate 3, 3-chloropropyltrimethoxysilane, anhydrous potassium carbonate, potassium iodide and anhydrous toluene in step b4 is 10 mmol: 22-25 mmol: 30-35 mmol: 1.2-2.4 g: 100-120 mL.

9. A method for preparing an antibacterial fresh-keeping packaging film for food packaging, characterized in that: The following steps are involved: Step 1: Weigh 80-90 parts of polyethylene resin, 30-40 parts of polylactic acid resin, 0.05-0.25 parts of modified nano silver particles and 1-3 parts of calcium stearate according to weight, and set aside; Step 2: The polyethylene resin, polylactic acid resin, modified nano silver particles and calcium stearate are mixed evenly, and then melt-extruded through a twin-screw extruder, and blow-molded into a film through a blow molding machine to obtain an antibacterial fresh-keeping packaging film for food packaging with a thickness of 0.050±0.002mm.

10. The method for preparing an antibacterial fresh-keeping packaging film for food packaging according to claim 9, characterized in that: The model of the polyethylene resin is LDPE 2426H; the model of the polylactic acid resin is PLA 4043D.

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