A biodegradable packaging film with secondary carrier carrying natural antibacterial agent and a preparation method thereof

Abstract

The application discloses a biodegradable packaging film with natural antibacterial agent and a preparation method thereof. The biodegradable film is prepared from the following components and weight fractions: 80-120 parts of a degradable base resin, 3-15 parts of a secondary carrier, 10-20 parts of a natural antibacterial agent, 0.5-6 parts of a slow-release agent and 0.05-1.5 parts of an emulsifier. The biodegradable packaging film is safe and non-toxic, can be directly contacted with food, and through 'on-demand' release of the antibacterial component, the utilization efficiency is maximized. The application further provides a preparation method of the biodegradable packaging film.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, and in particular relates to a biodegradable packaging film with a natural antibacterial agent carried on a secondary carrier and its preparation method. Background Technology

[0002] As the "white pollution," environmental damage, and health threats caused by traditional plastics become increasingly serious, countries around the world are developing green and environmentally friendly alternatives to non-degradable plastic packaging. The advantage of biodegradable plastics over traditional non-degradable plastics lies in the fact that the former can completely decompose into biomass, carbon dioxide, and water within 6 months under composting conditions, posing no pressure on the environment. Non-degradable plastics, on the other hand, are difficult to decompose even after hundreds of years in landfills, and their fragmentation process brings serious environmental hazards and threats to life and health. Biodegradable packaging films have great potential in replacing traditional plastic flexible packaging and can be widely used in food, pharmaceutical, and chemical industries. Biodegradable plastics are easily degraded under environmental conditions involving moisture, oxygen, or microorganisms. Therefore, to ensure the shelf life of biodegradable packaging and prevent microbial contamination of the contents, antimicrobial agents are usually added to inhibit microbial growth. Currently, most antimicrobial agents used in various packaging are organic or inorganic, with less research on adding natural antimicrobial agents. Natural antimicrobial agents have the advantages of being non-toxic, environmentally friendly, and highly biocompatible. They are widely available and abundant in nature, and are gradually becoming a hot research area in antimicrobial research.

[0003] Many natural antibacterial agents have unstable chemical structures and are sensitive to external factors such as temperature and light. Adding them directly during the melt extrusion process of packaging films will affect processing stability and the antibacterial properties of the final product. Patent CN105348614A discloses a controlled-release active modified atmosphere packaging material and its preparation method. This patent uses a method of melting and granulating a mixture of natural antibacterial agents, ethylene-vinyl acetate copolymer, and polyolefins to prepare antibacterial agent masterbatch, which is then mixed with a matrix and blown into film. However, this preparation method easily leads to instability in the blown film process, resulting in poor film surface smoothness and uneven thickness. Therefore, improving the heat resistance stability of natural antibacterial agents is of great significance for the practical application of antibacterial packaging.

[0004] Patent CN107913287A discloses a method for immobilizing natural antibacterial agents through attapulgite nanostructures. The nanocomposite antibacterial agent prepared by this invention has broad-spectrum antibacterial properties, thermal stability, and long-lasting antibacterial activity. When used as a feed additive, it can replace antibiotics used for a long time in animal breeding. However, if the composite antibacterial agent prepared by physical deposition is used in the thermoplastic processing of packaging films, it is easy to lose the connection with the carrier, reducing the protective efficacy of the carrier against the antibacterial agent.

[0005] Based on the above analysis, the problems and defects of the existing technology are as follows: when using natural antibacterial agents directly or solidified antibacterial agents prepared by physical adsorption or deposition in plastic thermoplastic packaging, it is difficult to maintain their thermal stability, processing suitability and long-lasting antibacterial properties, and they cannot meet the antibacterial requirements of biodegradable antibacterial food packaging. Summary of the Invention

[0006] In order to solve the problems mentioned in the background art, one of the objectives of the present invention is to provide a biodegradable packaging film with a secondary carrier carrying a natural antibacterial agent.

[0007] The first aspect of this invention provides a biodegradable packaging film with a secondary carrier carrying a natural antibacterial agent, the raw materials for which are prepared include:

[0008] 80-120 parts of biodegradable matrix resin

[0009] 3-15 copies of secondary carriers,

[0010] 5-20 parts of natural antibacterial agent

[0011] Sustained-release agent 0.5-6 parts,

[0012] Emulsifier 0.05-1.5 parts.

[0013] According to some embodiments of the present invention, the biodegradable matrix resin comprises at least two of polybutylene terephthalate-adipate copolymer, polylactic acid, polyglycolic acid, poly-ε-caprolactone, polyhydroxy fatty acid ester, poly-β-hydroxybutyric acid, polymethylethylene carbonate, polycaprolactone-lactide copolymer, and poly(ethylene lactide) copolymer.

[0014] According to some embodiments of the present invention, the secondary carrier includes at least one of epichlorohydrin, carboxymethyl cellulose, chitosan, β-cyclodextrin, stearic acid, sodium alginate, fatty acid, nano-clay, and fumed nano-silica.

[0015] According to some embodiments of the present invention, the natural antibacterial agent includes at least one selected from rosemary extract, olive leaf extract, grape seed extract, nano-lignin particles, tea polyphenols, catechins, carvacrol, thymol, cinnamaldehyde, vanillin, potassium sorbate, limonene, artemisinin, green-lipped mussel extract, eugenol, chlorogenic acid, and cinnamon essential oil.

[0016] According to some embodiments of the present invention, the sustained-release agent includes at least one selected from gallic acid ester, benzoin, patchouli, nutmeg, cinnamon, sandalwood, cedarwood, vetiver, and sage.

[0017] According to some embodiments of the invention, the emulsifier comprises at least two of hexaglycerol monolaurate, docosyl alcohol, sucrose fatty acid ester, hydrogenated castor oil, and PEG 40.

[0018] A second aspect of the present invention provides a method for preparing a biodegradable packaging film, comprising the following steps:

[0019] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent according to the ratio, add solvent, add the secondary carrier, stir thoroughly, heat and react, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h to obtain polyphenolic natural antibacterial agent loaded on secondary carrier;

[0020] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the secondary carrier loaded with polyphenolic natural antibacterial agent, slow-release agent and emulsifier, mix them, and then extrude, stretch, cool and granulate to obtain antibacterial masterbatch of natural antibacterial agent loaded with secondary carrier;

[0021] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, irradiation and winding to obtain the biodegradable film with natural antibacterial agent carried by the secondary carrier.

[0022] According to some embodiments of the present invention, in step (1), the solvent includes a KOH solution.

[0023] According to some embodiments of the present invention, in step (1), the temperature of the heating reaction is 50-90°C; and / or, the time of the heating reaction is 1h to 6h.

[0024] According to some embodiments of the present invention, in step (3), the irradiation includes at least one of plasma treatment, ozone ionization and short-wave ultraviolet radiation, in order to further enhance the affinity between the secondary carrier and the natural antibacterial agent and enhance the antibacterial stability.

[0025] Beneficial effects of the present invention

[0026] This invention utilizes the reactivity between a secondary carrier and a polyphenolic natural antibacterial agent to graft the polyphenolic natural antibacterial agent onto the secondary carrier through a chemical reaction. This solves the technical problems of easy oxidation, poor thermal stability, and poor processability of polyphenolic natural antibacterial agents in biodegradable plastic flexible packaging. The biodegradable film prepared by this invention is safe and non-toxic, and can come into direct contact with food. Its utilization efficiency is maximized through the "on-demand" release of antibacterial components. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the embodiments. The application of the present invention is not limited to the following embodiments, and any modifications made to the present invention will fall within the protection scope of the present invention.

[0028] It should be noted that all actual materials and raw materials used in the embodiments were obtained from commercially available sources.

[0029] Example 1

[0030] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0031] 30 parts of polybutylene terephthalate-adipate copolymer

[0032] 10 parts of poly-ε-caprolactone

[0033] 40 parts of polycaprolactone-lactide copolymer

[0034] Two parts epichlorohydrin

[0035] 1 part carboxymethyl cellulose

[0036] Four parts of nano-lignin particles,

[0037] 1 part catechin,

[0038] Patchouli 0.5 parts,

[0039] 0.1 parts of sucrose fatty acid ester.

[0040] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0041] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 30 mL of 0.1 mol / L KOH solution as solvent and catalyst, add secondary carrier, stir thoroughly, gradually heat to 50 °C, react for 1 h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60 °C for 48 h.

[0042] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0043] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, plasma irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0044] Example 2

[0045] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0046] 42 parts of polylactic acid

[0047] 54 parts of poly(ethylene glycol) lactide copolymer

[0048] 24 parts of polymethyl ethylene carbonate,

[0049] 9 parts epichlorohydrin

[0050] 6 parts nano clay

[0051] 12 parts of tea polyphenols

[0052] 8 parts of catechins

[0053] Two parts of gallate,

[0054] 4 parts nutmeg

[0055] 0.03 parts hydrogenated castor oil,

[0056] PEG 40 0.02 parts.

[0057] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0058] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 80mL of 0.1mol / L KOH solution as solvent and catalyst, add 9 parts of epichlorohydrin and 6 parts of nano clay, stir thoroughly, gradually heat to 90℃, react for 3h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h;

[0059] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0060] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, ozone ionization irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0061] Example 3

[0062] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0063] 80 parts of poly-β-hydroxybutyric acid

[0064] 10 parts polylactic acid

[0065] 4 parts of polyhydroxyalkanoate,

[0066] 5 parts of β-cyclodextrin

[0067] 5 parts of fumed nano silica

[0068] 9 parts of green-lipped mussel extract,

[0069] Eugenol 4 parts,

[0070] 6 parts vetiver

[0071] 0.78 parts of dodecyl alcohol,

[0072] 0.72 parts of hexaglycerol monolaurate.

[0073] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0074] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 60mL of 0.1mol / L KOH solution as solvent and catalyst, add 5 parts of β-cyclodextrin and 5 parts of fumed nano silica, stir thoroughly, gradually heat to 60℃, react for 6h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h;

[0075] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0076] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, short-wave ultraviolet irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0077] Example 4

[0078] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0079] 30 parts of polybutylene terephthalate-adipate copolymer

[0080] 10 parts of poly-ε-caprolactone

[0081] 40 parts of polycaprolactone-lactide copolymer

[0082] Two parts epichlorohydrin

[0083] 1 part carboxymethyl cellulose

[0084] Four parts of nano-lignin particles,

[0085] 1 part catechin,

[0086] Patchouli 0.5 parts,

[0087] 0.1 parts of sucrose fatty acid ester.

[0088] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0089] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 30 mL of aqueous solution as solvent and catalyst for reaction, add 10 parts of secondary carrier, stir thoroughly, gradually heat to 50℃, react for 1 h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72 h.

[0090] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0091] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, plasma irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0092] Example 5

[0093] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0094] 42 parts of polylactic acid

[0095] 54 parts of poly(ethylene glycol) lactide copolymer

[0096] 24 parts of polymethyl ethylene carbonate,

[0097] 9 parts epichlorohydrin

[0098] 6 parts nano clay

[0099] 12 parts of tea polyphenols

[0100] 8 parts of catechins

[0101] Two parts of gallate,

[0102] 4 parts nutmeg

[0103] 0.03 parts hydrogenated castor oil,

[0104] PEG 40 0.02 parts.

[0105] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0106] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 80mL of 0.1mol / L KOH solution as solvent and catalyst, add 9 parts of epichlorohydrin and 6 parts of nano clay, stir thoroughly at room temperature and react for 3h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h;

[0107] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0108] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, ozone ionization irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0109] Example 6

[0110] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0111] 42 parts of polylactic acid

[0112] 54 parts of poly(ethylene glycol) lactide copolymer

[0113] 24 parts of polymethyl ethylene carbonate,

[0114] 9 parts epichlorohydrin

[0115] 6 parts nano clay

[0116] 20 parts of tea polyphenols

[0117] Two parts of gallate,

[0118] 4 parts nutmeg

[0119] 0.03 parts hydrogenated castor oil,

[0120] PEG 40 0.02 parts.

[0121] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0122] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 80mL of 0.1mol / L KOH solution as solvent and catalyst, add 9 parts of epichlorohydrin and 6 parts of nano clay, stir thoroughly, gradually heat to 90℃, react for 3h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h;

[0123] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0124] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, ozone ionization irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0125] Example 7

[0126] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0127] 30 parts of polybutylene terephthalate-adipate copolymer

[0128] 10 parts of poly-ε-caprolactone

[0129] 40 parts of polycaprolactone-lactide copolymer

[0130] Two parts epichlorohydrin

[0131] 1 part carboxymethyl cellulose

[0132] Four parts of nano-lignin particles,

[0133] 1 part catechin,

[0134] Patchouli 0.5 parts,

[0135] 0.1 parts of sucrose fatty acid ester.

[0136] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0137] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 30 mL of 0.1 mol / L KOH solution as solvent and catalyst, add 10 parts of secondary carrier, stir thoroughly, gradually heat to 50℃, react for 1 h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72 h;

[0138] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0139] (3) Processing and shaping: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0140] Example 8

[0141] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0142] 80 parts of poly-β-hydroxybutyric acid

[0143] 10 parts polylactic acid

[0144] 4 parts of polyhydroxyalkanoate,

[0145] 10 parts of fumed nano silica

[0146] 9 parts of green-lipped mussel extract,

[0147] Eugenol 4 parts,

[0148] 6 parts vetiver

[0149] 0.78 parts of dodecyl alcohol,

[0150] 0.72 parts of hexaglycerol monolaurate.

[0151] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0152] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 60 mL of 0.1 mol / L KOH solution as solvent and catalyst, add 10 parts of fumed nano silica, stir thoroughly, gradually heat to 60℃, react for 6 h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72 h;

[0153] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0154] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, short-wave ultraviolet irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0155] Example 9

[0156] A biodegradable packaging film carrying a natural antibacterial agent on a secondary carrier is made from the following components and parts by weight:

[0157] 30 parts of polybutylene terephthalate-adipate copolymer

[0158] 10 parts of poly-ε-caprolactone

[0159] 40 parts of polycaprolactone-lactide copolymer

[0160] Two parts epichlorohydrin

[0161] 1 part carboxymethyl cellulose

[0162] Four parts of nano-lignin particles,

[0163] One part of catechin.

[0164] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0165] (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent, add 30 mL of 0.1 mol / L KOH solution as solvent and catalyst, add 10 parts of secondary carrier, stir thoroughly, gradually heat to 50℃, react for 1 h, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72 h;

[0166] (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the natural antibacterial agent, the slow-release agent and the emulsifier carried on the secondary carrier according to the weight parts of the above components. Stir evenly in a high-speed mixer, put into a screw extruder, extrude, draw into strips, cool, and pelletize to obtain the antibacterial masterbatch of natural antibacterial agent carried on the secondary carrier.

[0167] (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, plasma irradiation and winding to obtain a packaging film with natural antibacterial agent carried by a secondary carrier.

[0168] Comparative Example

[0169] A biodegradable film with a secondary carrier carrying a polyphenolic natural antibacterial agent is made from the following components and parts by weight: 42 parts polylactic acid,

[0170] 54 parts of poly(ethylene glycol) lactide copolymer

[0171] 24 parts of polymethyl ethylene carbonate,

[0172] 12 parts of tea polyphenols

[0173] 8 parts of catechins

[0174] Two parts of gallate,

[0175] 4 parts nutmeg

[0176] 0.03 parts hydrogenated castor oil,

[0177] PEG 40 0.02 parts.

[0178] The method for preparing the biodegradable packaging film with a natural antibacterial agent carried by the above-mentioned secondary carrier includes the following steps:

[0179] According to the weight parts of the above components, polylactic acid, poly(ethylene lactide) copolymer, polymethyl ethylene carbonate, tea polyphenols, catechins, gallate, nutmeg, hydrogenated castor oil, and PEG 40 are mixed evenly in a high-speed mixer, fed into a screw extruder, extruded, drawn into strands, cooled, and pelleted to obtain antibacterial masterbatch.

[0180] The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, plasma irradiation, and winding to obtain a packaging film.

[0181] Example of effect

[0182] Table 1 shows the antibacterial effects of the packaging films obtained in Examples 1-9 and the comparative examples against Staphylococcus aureus and Escherichia coli, their ability to scavenge 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) free radicals, and their preservation effects on strawberries.

[0183] As shown in Table 1, after the packaging film was immersed in a suspension of Gram-positive bacteria (Staphylococcus aureus and Escherichia coli) for 48 hours, the antibacterial properties of the packaging film increased with the increase of polyphenolic antibacterial agents. For the control group with directly added polyphenolic antibacterial agents, the antibacterial effect was poor because the thermoplastic processing destroyed the structure of the antibacterial agent and reduced its antibacterial properties.

[0184] Comparing Example 1 and Example 7 regarding irradiation treatment, Example 1 used plasma irradiation, while Example 7 did not undergo irradiation treatment. The results show that irradiation treatment has a positive effect on the antibacterial properties or free radical scavenging ability of the film.

[0185] Examples 2 and 6 employed two methods for using natural antibacterial agents: a combination of catechins and tea polyphenols, and the use of tea polyphenols alone. The results demonstrated that the combination of antibacterial agents had a synergistic effect, and the antibacterial effect was more pronounced when used in combination.

[0186] Examples 3 and 8 employed two methods on a secondary carrier: a combination of fumed silica and β-cyclodextrin, and fumed silica alone. The results demonstrated that the combination of the secondary carriers had a synergistic effect, and the antibacterial effect was more pronounced when the combination was used.

[0187] In Examples 4 and 5, water was used as the solvent and the reaction was carried out at room temperature during the preparation of the natural antibacterial agent loaded on the secondary carrier. The results showed that the secondary carrier and the antibacterial agent had poor reactivity in neutral solution or at room temperature. Therefore, the secondary carrier could not effectively protect the antibacterial activity of the antibacterial agent, resulting in poor antibacterial effect after melt extrusion processing.

[0188] Examples 1 and 9 compared the effects of using slow-release agents and emulsifiers. Example 1 used patchouli and sucrose fatty acid esters as slow-release agents and emulsifiers, while Example 10 did not use either. Experimental data showed that the slow-release agents and emulsifiers had beneficial effects on the antibacterial, antioxidant and preservation effects of the film. In Examples 1-3, the packaging film made after the effective reaction of the secondary carrier and antibacterial agent had a free radical scavenging capacity of 89-93%, which could effectively extend the shelf life of strawberries to 19 days.

[0189] The packaging film prepared by this invention has important guiding significance for the application of biodegradable food packaging.

[0190] Table 1. Antibacterial, antioxidant, and strawberry preservation effects of packaging film.

[0191]

[0192] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A biodegradable packaging film with a secondary carrier carrying a natural antibacterial agent, characterized in that, It is made from the following components and parts by weight: Biodegradable matrix resin: 42 parts polylactic acid, 54 parts poly(ethylene lactide) copolymer, and 24 parts polymethyl ethylene carbonate. Secondary carrier: 9 parts epichlorohydrin and 6 parts nano-clay, Natural antibacterial agents: 12 parts tea polyphenols and 8 parts catechins. Sustained-release agent: 2 parts gallate and 4 parts nutmeg. Emulsifiers: 0.03 parts hydrogenated castor oil and 0.02 parts PEG 40.

2. A method for preparing the biodegradable packaging film as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of polyphenolic natural antibacterial agent loaded on secondary carrier: Weigh the natural antibacterial agent according to the ratio, add solvent, add the secondary carrier, stir thoroughly, heat and react, filter the product under vacuum until dry and wash with toluene, wash with water until neutral, and freeze dry at -60℃ for 36-72h to obtain polyphenolic natural antibacterial agent loaded on secondary carrier; (2) Preparation of antibacterial masterbatch: Weigh the biodegradable matrix resin, the secondary carrier loaded with polyphenolic natural antibacterial agent, slow-release agent and emulsifier, mix them, and then extrude, stretch, cool and granulate to obtain antibacterial masterbatch of natural antibacterial agent loaded with secondary carrier; (3) Processing and molding: The antibacterial masterbatch is subjected to unidirectional casting extrusion stretching, cooling, traction, edge trimming, irradiation and winding to obtain the biodegradable film with natural antibacterial agent carried by the secondary carrier.

3. The method according to claim 2, characterized in that, In step (1), the solvent includes a KOH solution.

4. The method according to claim 2, characterized in that, In step (1), the temperature of the heating reaction is 50-90℃; and / or the heating reaction time is 1h to 6h.

5. The method according to claim 2, characterized in that, In step (3), the irradiation includes at least one of plasma treatment, ozone ionization and shortwave ultraviolet radiation.

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