Antibacterial packaging material and preparation method thereof

Abstract

The invention provides an antibacterial packaging material and a preparation method thereof, and belongs to the technical field of packaging materials. After a layered metal oxide / bentonite compound is prepared, the layered metal oxide / bentonite compound is subjected to intercalation modification through sodium dodecyl sulfate, then the surface of the layered metal oxide / bentonite compound is modified through polydopamine, the layered metal oxide / bentonite compound, silica sol modified through a silane coupling agent, antibacterial peptide and carboxylated chitosan are subjected to a coupling reaction together, modified chitosan is prepared, the modified chitosan, polylactic acid and a film forming auxiliary material are added into water, and the film forming agent is prepared. And homogenizing, degassing, pouring into a wet film, drying, drying, rewetting, and uncovering the film to obtain the antibacterial packaging material. The antibacterial packaging material prepared by the preparation method disclosed by the invention has better degradability, is safe, non-toxic, green and environment-friendly, has better antibacterial property, mechanical property, temperature resistance, weather resistance, higher barrier property to oxygen and water vapor and good thermal stability, so that the shelf life of food is prolonged, the addition of preservatives in a food processing process can be reduced or even avoided, and the service life of the food is prolonged. The food safety is improved, and the application prospect is wide.

Description

Technical Field

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

[0002] In the prior art, fresh food, fruits and vegetables, Chinese medicinal materials and other products are very easy to spoil when packaged and stored. The main reason is contact with air. Whether it is bacteria in the air or insect eggs remaining on the surface of medicinal materials, fruits and vegetables, they will multiply due to three possible factors: temperature, humidity and oxygen. Air is mainly a mixture of 78% nitrogen, 21% oxygen, and 1% rare gases and impurities. Experimental tests have shown that the spoilage of food is mostly caused by oxidation reaction under the action of oxygen, which promotes the reproduction of microorganisms and bacteria, resulting in food spoilage.

[0003] If the packaging can effectively control oxygen, there will be only one suffocating inert gas, such as nitrogen, in the packaging space, or the vacuum method can be used to suffocate and inhibit the growth of bacteria in food, and the oxidation and respiration of bacteria and eggs can be stopped, achieving natural, effective and safe sterilization, insecticide and egg killing effects, and ultimately achieving the effect of extending the preservation and antibacterial effect. However, if the packaging material cannot effectively isolate the air, nitrogen will also allow oxygen in the air to enter the packaging bag through the packaging material through gas exchange over a long period of time, and air leakage will occur in the case of vacuuming, so that oxidation reactions will continue to occur.

[0004] Antimicrobial food packaging is a positive active packaging concept proposed for the purpose of food preservation. In order to inhibit the growth of spoilage bacteria in food, antimicrobial agents can be added to packaging materials or coated on the surface of packaging materials, and the purpose of antimicrobial preservation can be achieved through the contact between materials and food. The application of antimicrobial food packaging can reduce the amount of preservatives directly added to food and improve the safety of food consumption. At present, the antimicrobial agents used in various antimicrobial packaging (food or non-food packaging) can be divided into two major categories. One is inorganic, mainly composed of metal ions such as silver, copper, and zinc, and the other is organic, such as organic acids and their salts, organic esters, alcohols, phenols, antibiotics, etc., such as sorbic acid, benzoic acid, propionic acid and its salts, and nisin. In food, most inorganic metal antimicrobial agents are not allowed to be used or their application must be strictly controlled, while organic food preservatives have poor heat resistance, safety, and stability. If added to packaging materials, their antimicrobial properties may be partially affected. Many antimicrobial agents that are more suitable for adding to food packaging materials have begun to attract the attention of researchers. Especially as people's advocacy of nature and health has become popular, the development and application of efficient and safe food antimicrobial agents has become an important research field for food preservatives in the world today. According to relevant data, the toxicity of natural preservative ingredients in foods that people eat for a long time is far lower than that of artificially synthesized preservatives. Therefore, the research on seeking natural preservatives from nature has attracted great attention from scientists in various countries. Summary of the invention

[0005] The purpose of the present invention is to propose an antibacterial packaging material and a preparation method thereof, which has good biodegradability, is safe and non-toxic, is green and environmentally friendly, and has good antibacterial properties, mechanical properties, temperature resistance, weather resistance, high barrier properties to oxygen and water vapor, and good thermal stability, so as to extend the shelf life of food, reduce or even avoid the addition of preservatives during food processing, improve food safety, and has broad application prospects.

[0006] The technical solution of the present invention is achieved in this way: The invention provides a method for preparing an antibacterial packaging material. A layered metal oxide / bentonite composite is prepared, and then subjected to sodium dodecyl sulfate intercalation modification, and then the surface is modified by polydopamine, and then coupled with silica sol modified by a silane coupling agent, antibacterial peptide and carboxylated chitosan to obtain modified chitosan, and the modified chitosan is added with polylactic acid and a film-forming auxiliary material into water, and then homogenized, degassed, poured into a wet film, and dried, baked, rehumidified, and peeled off to obtain the antibacterial packaging material.

[0007] As a further improvement of the present invention, the following steps are included: S1. Preparation of layered metal oxide / bentonite composite: copper nitrate and iron nitrate are dissolved in water, bentonite is added, and the bentonite is uniformly dispersed by ultrasonic treatment. Then, an alkali solution is added dropwise, and the mixture is heated for crystallization. After that, the precipitate is separated by filtration, and impurities are removed by washing. Finally, the washed product is dried and calcined to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: adding the layered metal oxide / bentonite composite obtained in step S1 to water, mixing uniformly by stirring, then adding sodium dodecyl sulfate, ultrasonically dispersing uniformly, then separating the product by centrifugation, washing and drying, to obtain an intercalated layered metal oxide / bentonite composite; S3. Polydopamine modification: adding the intercalated layered metal oxide / bentonite complex obtained in step S2 to water, adding dopamine hydrochloride and a catalyst, stirring the reaction under heating conditions, and after the reaction is completed, centrifuging, washing and drying to obtain a modified intercalated layered metal oxide / bentonite complex; S4. Preparation of modified silica sol: adding alkyl orthosilicate to ethanol, adding a silane coupling agent, then adding hydrochloric acid and water, stirring the reaction, and after the reaction is completed, a modified silica sol is obtained; S5. Preparation of carboxylated chitosan: dissolving chitosan in an acid solution, then adding α-ketoglutaric acid, heating to a first temperature and stirring to react, then adding sodium borohydride, continuing the reaction, then adding ethanol to precipitate, adding the precipitate and sodium hydroxide together to water, adding chloroacetic acid, heating to a second temperature and stirring to react, after the reaction is completed, adding ethanol to precipitate again, filtering, washing and drying to obtain carboxylated chitosan; S6. Preparation of modified chitosan: adding the antimicrobial peptide and the carboxylated chitosan obtained in step S5 to water, adding NHS and EDC, stirring for activation, then adding the modified intercalated layered metal oxide / bentonite composite obtained in step S3 and the modified silica sol obtained in step S4, stirring for reaction, and after the reaction, filtering, washing and drying to obtain modified chitosan; S7. Preparation of antibacterial packaging material: The modified chitosan obtained in step S6 is added to water, polylactic acid is added to obtain a suspension, and then a film-forming auxiliary material is added, and the mixture is homogenized using a colloid mill. After degassing, the mixture is poured into a wet film, and after drying, drying, rewetting, and peeling, an antibacterial packaging material is obtained.

[0008] As a further improvement of the present invention, the mass ratio of copper nitrate, iron nitrate and bentonite in step S1 is (3-5): (5-7): 10, the pH value of the solution is adjusted to 7.5-8.5 by dropping alkali solution, the temperature of the heating crystallization is 85-95°C, the time is 30-50min, and the temperature of the calcination is 650-750°C, and the time is 1-3h.

[0009] As a further improvement of the present invention, the mass ratio of the layered metal oxide / bentonite composite to sodium dodecyl sulfate in step S2 is 10:1-2.

[0010] As a further improvement of the present invention, in step S3, the mass ratio of the intercalated layered metal oxide / bentonite composite, dopamine hydrochloride and catalyst is 10: (3-4): (0.5-1), the catalyst is a Tris-HCl solution with a pH of 8.5-9.5, and the temperature of the stirring reaction under the heating conditions is 40-50°C for 3-5h.

[0011] As a further improvement of the present invention, the alkyl orthosilicate in step S4 is methyl orthosilicate or ethyl orthosilicate, the mass ratio of the alkyl orthosilicate, ethanol, silane coupling agent, hydrochloric acid and water is (12-15): (80-120): (3-5): (7-10): (3-5), the concentration of the hydrochloric acid is 1-3 mol / L, the stirring reaction time is 7-10 h, and the silane coupling agent is selected from at least one of KH550, KH560, KH602 and KH792, preferably, it is a mixture of KH550 and KH560, and the mass ratio is 4-6:3.

[0012] As a further improvement of the present invention, in step S5, the mass ratio of chitosan, α-ketoglutaric acid, sodium borohydride, sodium hydroxide and chloroacetic acid is 2: (3-4): (0.5-1): (1-1.5): (0.07-0.12), the acid solution is 2-3wt% acetic acid or lactic acid solution, the first temperature is 35-40°C, and the second temperature is 55-65°C.

[0013] As a further improvement of the present invention, the mass ratio of the carboxylated chitosan, antimicrobial peptide, NHS, EDC, modified intercalated layered metal oxide / bentonite composite and modified silica sol in step S6 is (5-7): (3-4): (2-3): (2-3): 10: (2-3), the stirring activation time is 30-40 min, the stirring reaction temperature is 40-50° C., and the time is 12-15 h.

[0014] As a further improvement of the present invention, the mass ratio of the modified chitosan, polylactic acid and film-forming auxiliary material in step S7 is (10-15): (3-4): (2-3), and the film-forming auxiliary material is selected from at least one of polyvinyl alcohol, carbomer or sodium alginate.

[0015] The present invention further protects an antibacterial packaging material prepared by the above preparation method.

[0016] The present invention has the following beneficial effects: Layered metal oxide is a layered inorganic solid. Embedding nano-bentonite in food packaging film can reduce the gas transmission rate of the material to maintain the freshness of the food and extend the shelf life of the food. Bentonite is a layered substance that can form a complex with layered metal oxides. After the surfactant sodium dodecyl sulfate is intercalated, the interlayer spacing increases, which is beneficial to the modification of polydopamine, so that the surface of the prepared composite has rich amino groups and is easy to react with carboxylated chitosan to obtain modified chitosan, so that the mechanical properties, barrier properties, thermal stability, flame retardancy, hydrophilicity, controlled drug delivery and antibacterial activity of the composite material are significantly improved.

[0017] Alkyl orthosilicate undergoes a sol-gel reaction through acid catalysis. Under the modification of a silane coupling agent, it has amino and epoxy groups on its surface, which can react with carboxylated chitosan to modify the chitosan, further improving the mechanical properties, high temperature resistance and barrier properties of the composite material.

[0018] Polysaccharides have good biocompatibility and biodegradability. Compared with lipid and protein matrices, polysaccharides can obtain the desired properties through the interaction of functional groups with antibacterial substances. Their fiber structure can also maintain good stability at high temperatures, which can significantly improve the stability and utilization rate of natural antibacterial substances. Chitosan is a type of polysaccharide with good antibacterial and film-forming properties. It can adsorb on the surface of negatively charged microbial cells. On the one hand, it may form a layer of polymer film to prevent nutrients from being transported into the cells. On the other hand, it makes the negative charge on the cell wall and cell membrane unevenly distributed, destroys the synthesis and dissolution balance of the cell wall, dissolves the cell wall, and thus has an antibacterial and bactericidal effect; and it forms a viscous film-forming solution through intramolecular and intermolecular hydrogen bonds, and can form a highly transparent edible film after cast drying. However, chitosan has poor solubility in water. Therefore, the present invention prepares carboxylated chitosan through reaction, which greatly improves its water solubility on the one hand, while its antibacterial property and film-forming property remain unchanged, and on the other hand, can significantly improve its coupling reaction with antimicrobial peptides, amino groups of modified intercalated layered metal oxide / bentonite composites modified with surface polydopamine, and silica sol modified with coupling agent, so that the antibacterial property of the prepared modified chitosan is further enhanced, and at the same time, the barrier property after film formation is significantly improved, and the mechanical properties, temperature resistance and weather resistance of the film-formed material are significantly improved.

[0019] The antibacterial packaging material prepared by the present invention has good degradability, is safe and non-toxic, is green and environmentally friendly, and has good antibacterial properties, mechanical properties, temperature resistance, and weather resistance. It has high barrier properties to oxygen and water vapor and good thermal stability, so as to extend the shelf life of food, reduce or even avoid the addition of preservatives during food processing, improve food safety, and has broad application prospects. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0021] NHS, N-hydroxysuccinimide; EDC, 1-ethyl-(3-dimethylaminopropyl)carbodiimide; antimicrobial peptides, purchased from Hangzhou Gutuo Biotechnology Co., Ltd.; bentonite, water content 28%, compressive strength 1675 MPa, whiteness 80-83, purchased from Lingshou Yongshun Mineral Products Processing Plant; chitosan, mesh size 80 mesh, deacetylation degree>80%, purchased from Shaanxi Rankang Biotechnology Co., Ltd.

[0022] Example 1 This embodiment provides a method for preparing an antibacterial packaging material, comprising the following steps: S1. Preparation of layered metal oxide / bentonite composite: 3 g copper nitrate and 5 g ferric nitrate were dissolved in 200 mL water, 10 g bentonite was added, ultrasonic dispersion was performed at 1000 W for 15 min, 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 7.5, the solution was heated to 85 ° C, crystallized for 30 min, filtered, washed, dried, and calcined at 650 ° C for 1 h to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: 10 g of layered metal oxide / bentonite composite was added to 200 mL of water, stirred for 10 min, 1 g of sodium dodecyl sulfate was added, ultrasonically dispersed at 1000 W for 15 min, centrifuged, washed, and dried to obtain an intercalated layered metal oxide / bentonite composite; S3. Polydopamine modification: 10 g of intercalated layered metal oxide / bentonite composite was added to water, 3 g of dopamine hydrochloride and 0.5 g of catalyst were added, heated to 40°C, stirred for reaction for 3 h, centrifuged, washed, and dried to obtain a modified intercalated layered metal oxide / bentonite composite; The catalyst has a pH of 8.5 in a Tris-HCl solution; S4 Preparation of modified silica sol: 12g of methyl orthosilicate was added to 80g of ethanol, 3g of silane coupling agent was added, 7g of 1mol / L hydrochloric acid and 3g of water were added, and the reaction was stirred for 7h to obtain a modified silica sol; The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 4:3; S5. Preparation of carboxylated chitosan: 2 g of chitosan was dissolved in 100 mL of 2 wt% acetic acid solution, 3 g of α-ketoglutaric acid was added, the mixture was heated to 35°C, the reaction was stirred for 24 h, 0.5 g of sodium borohydride was added, the reaction was continued for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, the mixture was precipitated for 1 h, the product and 1 g of sodium hydroxide were added to 100 mL of water, 0.07 g of chloroacetic acid was added, the mixture was heated to 55°C, the reaction was stirred for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, the mixture was precipitated for 1 h, the mixture was filtered, washed, and dried to obtain carboxylated chitosan; S6. Preparation of modified chitosan: 5 g of carboxylated chitosan and 3 g of antimicrobial peptide were added to 200 mL of water, 2 g of NHS and 2 g of EDC were added, and the mixture was stirred and activated for 30 min. 10 g of modified intercalated layered metal oxide / bentonite composite and 2 g of modified silica sol were added, and the mixture was stirred and reacted at 40 ° C for 12 h. The mixture was filtered, washed, and dried to obtain modified chitosan. S7. Preparation of antibacterial packaging material: Add 10g modified chitosan to 200mL water, add 3g polylactic acid to prepare a suspension, add 2g polyvinyl alcohol, use a colloid mill for homogenization for 5min, ultrasonic degassing for 10min, degassing for 30min under vacuum of 0.1MPa, adjust the temperature of the degassed film liquid to 45℃, pour it into the center of a clean and dry glass, let the film liquid flow into a film on the glass plate by itself, control the wet film thickness to be about 2mm, place it in an electric blast drying oven at 60℃ to dry, then place the dried film-carrying glass plate on a boiling water bath to rewet, steam for 10min, remove the film, place it in a sealed box after drying at room temperature, and store it in a desiccator to obtain the antibacterial packaging material.

[0023] Example 2 This embodiment provides a method for preparing an antibacterial packaging material, comprising the following steps: S1. Preparation of layered metal oxide / bentonite composite: 5 g copper nitrate and 7 g ferric nitrate were dissolved in 200 mL water, 10 g bentonite was added, ultrasonic dispersion was performed at 1000 W for 15 min, 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 8.5, the solution was heated to 95 ° C, crystallized for 50 min, filtered, washed, dried, and calcined at 750 ° C for 3 h to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: 10 g of layered metal oxide / bentonite composite was added to 200 mL of water, stirred and mixed for 10 min, 2 g of sodium dodecyl sulfate was added, ultrasonically dispersed at 1000 W for 15 min, centrifuged, washed, and dried to obtain an intercalated layered metal oxide / bentonite composite; S3. Polydopamine modification: 10 g of intercalated layered metal oxide / bentonite composite was added to water, 4 g of dopamine hydrochloride and 1 g of catalyst were added, heated to 50°C, stirred for reaction for 5 h, centrifuged, washed, and dried to obtain a modified intercalated layered metal oxide / bentonite composite; The catalyst has a pH of 9.5 in a Tris-HCl solution; S4 Preparation of modified silica sol: 15g of tetraethyl orthosilicate was added to 120g of ethanol, 5g of silane coupling agent was added, 10g of 3mol / L hydrochloric acid and 5g of water were added, and the reaction was stirred for 10h to obtain a modified silica sol; The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 6:3; S5. Preparation of carboxylated chitosan: 2 g of chitosan was dissolved in 100 mL of 3 wt% lactic acid solution, 4 g of α-ketoglutaric acid was added, the mixture was heated to 40°C, stirred and reacted for 24 h, 1 g of sodium borohydride was added, the reaction was continued for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, the product and 1.5 g of sodium hydroxide were added to 100 mL of water, 0.12 g of chloroacetic acid was added, the mixture was heated to 65°C, stirred and reacted for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, filtering, washing, and drying were carried out to obtain carboxylated chitosan; S6. Preparation of modified chitosan: 7 g of carboxylated chitosan and 4 g of antimicrobial peptide were added to 200 mL of water, 3 g of NHS and 3 g of EDC were added, and the mixture was stirred and activated for 40 min. 10 g of modified intercalated layered metal oxide / bentonite composite and 3 g of modified silica sol were added, and the mixture was stirred and reacted at 50 ° C for 15 h. The mixture was filtered, washed, and dried to obtain modified chitosan. S7. Preparation of antibacterial packaging material: Add 15g modified chitosan to 200mL water, add 4g polylactic acid to prepare a suspension, add 3g carbomer, use a colloid mill for homogenization for 5min, ultrasonic degassing for 10min, degas at a vacuum degree of 0.1MPa for 30min, adjust the temperature of the degassed film liquid to 45℃, pour it into the center of a clean and dry glass, let the film liquid flow into a film on the glass plate by itself, control the wet film thickness to be about 2mm, place it in an electric blast drying oven at 60℃ to dry, then place the dried film-carrying glass plate on a boiling water bath to rewet, steam for 10min, remove the film, place it in a sealed box after drying at room temperature, and store it in a desiccator to obtain the antibacterial packaging material.

[0024] Example 3 This embodiment provides a method for preparing an antibacterial packaging material, comprising the following steps: S1. Preparation of layered metal oxide / bentonite composite: 4 g copper nitrate and 6 g ferric nitrate were dissolved in 200 mL water, 10 g bentonite was added, ultrasonic dispersion was performed at 1000 W for 15 min, 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 8, the solution was heated to 90 ° C, crystallized for 40 min, filtered, washed, dried, and calcined at 700 ° C for 2 h to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: 10 g of layered metal oxide / bentonite composite was added to 200 mL of water, stirred for 10 min, 1.5 g of sodium dodecyl sulfate was added, ultrasonically dispersed at 1000 W for 15 min, centrifuged, washed, and dried to obtain an intercalated layered metal oxide / bentonite composite; S3. Polydopamine modification: 10 g of intercalated layered metal oxide / bentonite composite was added to water, 3.5 g of dopamine hydrochloride and 0.7 g of catalyst were added, heated to 45°C, stirred for 4 h, centrifuged, washed, and dried to obtain a modified intercalated layered metal oxide / bentonite composite; A Tris-HCl solution of the catalyst with a pH of 9; S4 Preparation of modified silica sol: 13g of ethyl orthosilicate was added to 100g of ethanol, 4g of silane coupling agent was added, 8g of 2mol / L hydrochloric acid and 4g of water were added, and the reaction was stirred for 8h to obtain a modified silica sol; The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 5:3; S5. Preparation of carboxylated chitosan: 2 g of chitosan was dissolved in 100 mL of 2.5 wt% acetic acid solution, 3.4 g of α-ketoglutaric acid was added, the mixture was heated to 37 ° C, stirred and reacted for 24 h, 0.7 g of sodium borohydride was added, the reaction was continued for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, the product and 1.2 g of sodium hydroxide were added to 100 mL of water, 0.1 g of chloroacetic acid was added, the mixture was heated to 60 ° C, stirred and reacted for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, filtering, washing, and drying to obtain carboxylated chitosan; S6. Preparation of modified chitosan: 6 g of carboxylated chitosan and 3.5 g of antimicrobial peptide were added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred and activated for 35 min. 10 g of modified intercalated layered metal oxide / bentonite composite and 2.5 g of modified silica sol were added, and the mixture was stirred and reacted at 45 ° C for 13 h. The mixture was filtered, washed, and dried to obtain modified chitosan. S7. Preparation of antibacterial packaging material: Add 12g of modified chitosan to 200mL of water, add 3.5g of polylactic acid to prepare a suspension, add 2.5g of sodium alginate, use a colloid mill for homogenization for 5min, ultrasonic degassing for 10min, degassing for 30min under a vacuum degree of 0.1MPa, adjust the temperature of the degassed membrane liquid to 45℃, pour it into the center of a clean and dry glass, let the membrane liquid flow into a film on the glass plate by itself, control the wet film thickness to be about 2mm, place it in an electric blast drying oven at 60℃ to dry, then place the dried film-carrying glass plate on a boiling water bath to rewet, steam for 10min, remove the film, place it in a sealed box after drying at room temperature, and store it in a desiccator to obtain the antibacterial packaging material.

[0025] Example 4 Compared with Example 3, the difference is that the silane coupling agent is a single KH550.

[0026] Example 5 Compared with Example 3, the difference is that the silane coupling agent is a single KH560.

[0027] Comparative Example 1 Compared with Example 3, the difference is that bentonite is not added in step S1.

[0028] The details are as follows: S1. Preparation of layered metal oxides: 8 g of copper nitrate and 12 g of ferric nitrate were dissolved in 200 mL of water, and ultrasonically dispersed at 1000 W for 15 min. 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 8. The solution was heated to 90 ° C, crystallized for 40 min, filtered, washed, dried, and calcined at 700 ° C for 2 h to obtain layered metal oxides.

[0029] Comparative Example 2 Compared with Example 3, the difference is that step S2 is not performed.

[0030] The details are as follows: S1. Preparation of layered metal oxide / bentonite composite: 4 g copper nitrate and 6 g ferric nitrate were dissolved in 200 mL water, 10 g bentonite was added, ultrasonic dispersion was performed at 1000 W for 15 min, 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 8, the solution was heated to 90 ° C, crystallized for 40 min, filtered, washed, dried, and calcined at 700 ° C for 2 h to obtain a layered metal oxide / bentonite composite; S2. Polydopamine modification: 10 g of a layered metal oxide / bentonite composite was added to water, 3.5 g of dopamine hydrochloride and 0.7 g of a catalyst were added, heated to 45° C., stirred for 4 h, centrifuged, washed, and dried to obtain a modified layered metal oxide / bentonite composite; A Tris-HCl solution of the catalyst with a pH of 9; S3. Preparation of modified silica sol: 13 g of ethyl orthosilicate was added to 100 g of ethanol, 4 g of a silane coupling agent was added, 8 g of 2 mol / L hydrochloric acid and 4 g of water were added, and the reaction was stirred for 8 h to obtain a modified silica sol; The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 5:3; S4. Preparation of carboxylated chitosan: 2 g of chitosan was dissolved in 100 mL of 2.5 wt% acetic acid solution, 3.4 g of α-ketoglutaric acid was added, the mixture was heated to 37 ° C, stirred and reacted for 24 h, 0.7 g of sodium borohydride was added, the reaction was continued for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, the product and 1.2 g of sodium hydroxide were added to 100 mL of water, 0.1 g of chloroacetic acid was added, the mixture was heated to 60 ° C, stirred and reacted for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, filtering, washing, and drying to obtain carboxylated chitosan; S5. Preparation of modified chitosan: 6 g of carboxylated chitosan and 3.5 g of antimicrobial peptide were added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred and activated for 35 min. 10 g of modified layered metal oxide / bentonite composite and 2.5 g of modified silica sol were added, and the mixture was stirred and reacted at 45 ° C for 13 h. The mixture was filtered, washed, and dried to obtain modified chitosan. S6. Preparation of antibacterial packaging material: Add 12g modified chitosan to 200mL water, add 3.5g polylactic acid to prepare a suspension, add 2.5g sodium alginate, use a colloid mill for homogenization for 5min, ultrasonic degassing for 10min, degassing for 30min under vacuum of 0.1MPa, adjust the temperature of the degassed membrane liquid to 45℃, pour it into the center of a clean and dry glass, let the membrane liquid flow into a film on the glass plate by itself, control the wet film thickness to be about 2mm, place it in an electric blast drying oven at 60℃ to dry, then place the dried film-carrying glass plate on a boiling water bath to rewet, steam for 10min, remove the film, place it in a sealed box after drying at room temperature, and store it in a desiccator to obtain the antibacterial packaging material.

[0031] Comparative Example 3 Compared with Example 3, the difference is that step S3 is not performed.

[0032] The details are as follows: S1. Preparation of layered metal oxide / bentonite composite: 4 g copper nitrate and 6 g ferric nitrate were dissolved in 200 mL water, 10 g bentonite was added, ultrasonic dispersion was performed at 1000 W for 15 min, 2 mol / L NaOH was added dropwise to adjust the pH value of the solution to 8, the solution was heated to 90 ° C, crystallized for 40 min, filtered, washed, dried, and calcined at 700 ° C for 2 h to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: 10 g of layered metal oxide / bentonite composite was added to 200 mL of water, stirred for 10 min, 1.5 g of sodium dodecyl sulfate was added, ultrasonically dispersed at 1000 W for 15 min, centrifuged, washed, and dried to obtain an intercalated layered metal oxide / bentonite composite; S3. Preparation of modified silica sol: 13 g of ethyl orthosilicate was added to 100 g of ethanol, 4 g of a silane coupling agent was added, 8 g of 2 mol / L hydrochloric acid and 4 g of water were added, and the reaction was stirred for 8 h to obtain a modified silica sol; The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 5:3; S4. Preparation of carboxylated chitosan: 2 g of chitosan was dissolved in 100 mL of 2.5 wt% acetic acid solution, 3.4 g of α-ketoglutaric acid was added, the mixture was heated to 37 ° C, stirred and reacted for 24 h, 0.7 g of sodium borohydride was added, the reaction was continued for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, the product and 1.2 g of sodium hydroxide were added to 100 mL of water, 0.1 g of chloroacetic acid was added, the mixture was heated to 60 ° C, stirred and reacted for 10 h, ethanol was added until the ethanol content of the system was 80 wt%, precipitation was carried out for 1 h, filtering, washing, and drying to obtain carboxylated chitosan; S5. Preparation of modified chitosan: 6 g of carboxylated chitosan and 3.5 g of antimicrobial peptide were added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred and activated for 35 min. 10 g of intercalated layered metal oxide / bentonite composite and 2.5 g of modified silica sol were added, and the mixture was stirred and reacted at 45 ° C for 13 h, filtered, washed, and dried to obtain modified chitosan. S6. Preparation of antibacterial packaging material: Add 12g modified chitosan to 200mL water, add 3.5g polylactic acid to prepare a suspension, add 2.5g sodium alginate, use a colloid mill for homogenization for 5min, ultrasonic degassing for 10min, degassing for 30min under vacuum of 0.1MPa, adjust the temperature of the degassed membrane liquid to 45℃, pour it into the center of a clean and dry glass, let the membrane liquid flow into a film on the glass plate by itself, control the wet film thickness to be about 2mm, place it in an electric blast drying oven at 60℃ to dry, then place the dried film-carrying glass plate on a boiling water bath to rewet, steam for 10min, remove the film, place it in a sealed box after drying at room temperature, and store it in a desiccator to obtain the antibacterial packaging material.

[0033] Comparative Example 4 Compared with Example 3, the difference is that no silane coupling agent is added in step S4.

[0034] The details are as follows: S4. Preparation of silica sol: 13 g of tetraethyl orthosilicate was added to 100 g of ethanol, 8 g of 2 mol / L hydrochloric acid and 4 g of water were added, and the mixture was stirred for 8 h to obtain silica sol.

[0035] Comparative Example 5 Compared with Example 3, the difference is that no antimicrobial peptide is added in step S6.

[0036] The details are as follows: S6. Preparation of modified chitosan: 9.5 g of carboxylated chitosan was added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred and activated for 35 min. 10 g of modified intercalated layered metal oxide / bentonite composite and 2.5 g of modified silica sol were added, and the mixture was stirred and reacted at 45 °C for 13 h. The mixture was filtered, washed and dried to obtain modified chitosan.

[0037] Comparative Example 6 Compared with Example 3, the difference is that no modified silica sol is added in step S6.

[0038] The details are as follows: S6. Preparation of modified chitosan: 6 g of carboxylated chitosan and 3.5 g of antimicrobial peptide were added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred and activated for 35 min. 12.5 g of modified intercalated layered metal oxide / bentonite composite was added, and the mixture was stirred and reacted at 45 °C for 13 h. The mixture was filtered, washed, and dried to obtain modified chitosan.

[0039] Comparative Example 7 Compared with Example 3, the difference is that no modified intercalated layered metal oxide / bentonite composite is added in step S6.

[0040] The details are as follows: S6. Preparation of modified chitosan: 6 g of carboxylated chitosan and 3.5 g of antimicrobial peptide were added to 200 mL of water, 2.5 g of NHS and 2.5 g of EDC were added, and the mixture was stirred for activation for 35 min. 12.5 g of modified silica sol was added, and the mixture was stirred for reaction at 45 °C for 13 h. The mixture was filtered, washed, and dried to obtain modified chitosan.

[0041] Test Example 1 The antibacterial and mildew-proof properties of the antibacterial packaging materials prepared in Examples 1-5 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0042] Antibacterial performance test: According to GB / T 31402-2015 "Test method for antibacterial performance of plastic surface", the test method adopts the film method, and the test bacteria are: Escherichia coli ATCC25922, Staphylococcus aureus ATCC29213; the same sample is tested 5 times and the average value is taken.

[0043] Anti-mildew performance test: refer to GB / T24128-2009 for anti-mildew test. Test bacteria: Aspergillus niger AS3.315, Penicillium funiculum AS3.3875, Chaetomium globosum AS3.3601, repeat the test of 5 samples of the same sample and take the average value.

[0044] Table 1

[0045] It can be seen from the above table that the antibacterial packaging materials prepared in Examples 1-3 of the present invention have good antibacterial and mildew resistance.

[0046] Test Example 2 The antibacterial packaging materials prepared in Examples 1-5 and Comparative Examples 1-7 were tested for mechanical properties. The results are shown in Table 2.

[0047] The tensile strength and elongation at break of the film were measured using a universal material testing machine. The measuring conditions were: tensile rate of 100 mm / min, spacing of 30 mm, measuring environment of 23±2°C, and relative humidity of 50±2%.

[0048] Table 2

[0049] It can be seen from the above table that the antibacterial packaging materials prepared in Examples 1-3 of the present invention have good mechanical properties.

[0050] Test Example 3 The antibacterial packaging materials prepared in Examples 1-5 and Comparative Examples 1-7 were tested for barrier properties. The results are shown in Table 3.

[0051] Table 3

[0052] It can be seen from the above table that the antibacterial packaging materials prepared in Examples 1-3 of the present invention have good barrier properties.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial packaging material, characterized in that: The following steps are involved: S1. Preparation of layered metal oxide / bentonite composite: copper nitrate and iron nitrate are dissolved in water, bentonite is added, and the bentonite is uniformly dispersed by ultrasonic treatment. Then, an alkali solution is added dropwise, and the mixture is heated for crystallization. After that, the precipitate is separated by filtration, and impurities are removed by washing. Finally, the washed product is dried and calcined to obtain a layered metal oxide / bentonite composite; S2. Preparation of intercalated layered metal oxide / bentonite composite: adding the layered metal oxide / bentonite composite obtained in step S1 to water, mixing uniformly by stirring, then adding sodium dodecyl sulfate, ultrasonically dispersing uniformly, then separating the product by centrifugation, washing and drying, to obtain an intercalated layered metal oxide / bentonite composite; S3. Polydopamine modification: adding the intercalated layered metal oxide / bentonite complex obtained in step S2 to water, adding dopamine hydrochloride and a catalyst, stirring the reaction under heating conditions, and after the reaction is completed, centrifuging, washing and drying to obtain a modified intercalated layered metal oxide / bentonite complex; S4. Preparation of modified silica sol: adding alkyl orthosilicate to ethanol, adding a silane coupling agent, then adding hydrochloric acid and water, stirring the reaction, and after the reaction is completed, a modified silica sol is obtained; S5. Preparation of carboxylated chitosan: dissolving chitosan in an acid solution, then adding α-ketoglutaric acid, heating to a first temperature and stirring to react, then adding sodium borohydride, continuing the reaction, then adding ethanol to precipitate, adding the precipitate and sodium hydroxide together to water, adding chloroacetic acid, heating to a second temperature and stirring to react, after the reaction is completed, adding ethanol to precipitate again, filtering, washing and drying to obtain carboxylated chitosan; S6. Preparation of modified chitosan: adding the antimicrobial peptide and the carboxylated chitosan obtained in step S5 to water, adding NHS and EDC, stirring for activation, then adding the modified intercalated layered metal oxide / bentonite composite obtained in step S3 and the modified silica sol obtained in step S4, stirring for reaction, and after the reaction, filtering, washing and drying to obtain modified chitosan; S7. Preparation of antibacterial packaging material: The modified chitosan obtained in step S6 is added to water, polylactic acid is added to obtain a suspension, and then a film-forming auxiliary material is added, and the mixture is homogenized using a colloid mill. After degassing, the mixture is poured into a wet film, and after drying, drying, rewetting, and peeling, an antibacterial packaging material is obtained.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of copper nitrate, iron nitrate and bentonite is (3-5): (5-7): 10, the pH value of the solution is adjusted to 7.5-8.5 by dropping alkali solution, the heating crystallization temperature is 85-95°C, the time is 30-50min, and the calcination temperature is 650-750°C, and the time is 1-3h.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of the layered metal oxide / bentonite composite to sodium dodecyl sulfate is 10:1-2.

4. The preparation method according to claim 1, characterized in that In step S3, the mass ratio of the intercalated layered metal oxide / bentonite composite, dopamine hydrochloride and catalyst is 10: (3-4): (0.5-1), the catalyst is a Tris-HCl solution with a pH of 8.5-9.5, and the stirring reaction temperature under the heating condition is 40-50° C. for 3-5 hours.

5. The preparation method according to claim 1, characterized in that: In step S4, the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate, the mass ratio of the alkyl orthosilicate, ethanol, silane coupling agent, hydrochloric acid and water is (12-15): (80-120): (3-5): (7-10): (3-5), the concentration of the hydrochloric acid is 1-3 mol / L, the stirring reaction time is 7-10 h, and the silane coupling agent is selected from at least one of KH550, KH560, KH602 and KH792.

6. The preparation method according to claim 5, characterized in that: The silane coupling agent is a mixture of KH550 and KH560, with a mass ratio of 4-6:

3.

7. The preparation method according to claim 1, characterized in that: In step S5, the mass ratio of chitosan, α-ketoglutaric acid, sodium borohydride, sodium hydroxide and chloroacetic acid is 2: (3-4): (0.5-1): (1-1.5): (0.07-0.12), the acid solution is 2-3wt% acetic acid or lactic acid solution, the first temperature is 35-40°C, and the second temperature is 55-65°C.

8. The preparation method according to claim 1, characterized in that: In step S6, the mass ratio of carboxylated chitosan, antimicrobial peptide, NHS, EDC, modified intercalated layered metal oxide / bentonite composite and modified silica sol is (5-7): (3-4): (2-3): (2-3): 10: (2-3), the stirring activation time is 30-40 minutes, the stirring reaction temperature is 40-50°C, and the time is 12-15 hours.

9. The preparation method according to claim 1, characterized in that: In step S7, the mass ratio of the modified chitosan, polylactic acid and film-forming auxiliary material is (10-15): (3-4): (2-3), and the film-forming auxiliary material is selected from at least one of polyvinyl alcohol, carbomer or sodium alginate.

10. An antibacterial packaging material prepared by the preparation method according to any one of claims 1 to 9.

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