A low-temperature-resistant and puncture-resistant antibacterial composite film and its application in food packaging

Abstract

The present invention discloses a novel low-temperature-resistant, puncture-resistant and antibacterial composite film material. The composite film is a seven-layer co-extruded film, including raw materials such as polyamide (PA), polyethylene (PE) resin, polyethylene-vinyl alcohol copolymer (EVOH) resin, and polypropylene-ethylene octene polymer (PP / POE) resin. From the outside to the inside, the film comprises a PA layer, a PE layer, a PP / POE layer, an EVOH layer, a PE layer, a PA layer, and a PE layer. The innermost PE layer uses porous alumina as a carrier and is loaded with grafted nano-zinc oxide to achieve a highly efficient antibacterial function. At the same time, through the composite of different materials, functional characteristics such as low-temperature resistance, puncture resistance, high barrier properties, and corrosion and mildew resistance are achieved. The composite film has broad market prospects and has been applied in the actual production of litchi packaging.

Description

Technical Field

[0001] The invention belongs to the field of food packaging materials, and in particular relates to a low-temperature-resistant and puncture-resistant antibacterial composite film and an application thereof in food packaging. Background Art

[0002] Food packaging materials involve a wide range and are in high demand. They are an indispensable part of daily life. In recent years, more and more diverse packaging products have been launched to meet the different needs of consumers. If we focus on the field of food packaging, we will find that the requirements for food packaging are mainly the following: 1. Preservation: Preservation is often referred to as waterproofing, anti-oxidation, and anti-corrosion. The use of high-barrier materials can greatly reduce the penetration of oxygen and water vapor and retain the aroma of food; preservatives can effectively inhibit the growth of microorganisms; 2. Safety: Food packaging is not allowed to use any toxic and harmful substances, including cross-linked related intermediates, because there is a certain risk of shedding; 3. Temperature resistance: The development of cold chain logistics has made fresh food transportation universal. At the same time, some products need to be heated and steamed together with the bags before eating, such as self-heating rice, military rations, etc., so there are certain requirements for the changes in the mechanical properties of the corresponding materials at low or high temperatures; 4. Appearance: Consumers' first impression of a product is its appearance, which requires the product to have beautiful and clear printing and a smooth surface; 5. Heat sealability: Food packaging requires sealing, and the material needs to be heat-sealed at a lower temperature. The sealing layer with a lower melting point can reduce energy loss and save production costs. The performance of a single material cannot meet all requirements. The co-extrusion composite process can stack different film layers together to achieve the multifunctionality of the material. It is one of the most widely used composite film production processes.

[0003] Chinese patent CN101100123A discloses a seven-layer co-extruded high-barrier packaging film, comprising seven layers: the first being a printing layer composed of metallocene polyethylene (LLDPE), low-density polyethylene (LDPE), and a lubricant (FSU); the second being a light-shielding layer composed of polyethylene white masterbatch, linear low-density polyethylene (LLDPE), and low-density polyethylene (LDPE); the third being an adhesive layer composed of a TIE adhesive; the fourth being a barrier layer composed of ethylene-vinyl alcohol copolymer (EVOH); the fifth being an adhesive layer composed of a TIE adhesive; the sixth being a light-shielding layer composed of linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and a polyethylene black masterbatch; and the seventh being a heat-sealing layer composed of metallocene polyethylene (LLDPE), low-density polyethylene (LDPE), and a lubricant (FSU). This patent is primarily based on research into high-barrier materials and utilizes a separate adhesive layer, fundamentally different from the technical solution of this patent, representing two distinct composite films and research approaches.

[0004] Chinese patent CN103465584B discloses a low-temperature freezing multi-layer co-extruded film and a preparation method thereof. The film is a five-layer co-extruded film, and from the outer layer to the inner layer, there are the first PE layer, the second PE layer, the third PA layer, the fourth PE layer and the fifth PE layer. The thickness ratios of the five-layer co-extruded film from the outer layer to the inner layer are 1.5-2:1.25-1.75:1-2:1.25-1.75:1.5-2. The five-layer co-extrusion scheme used in the patent has different thickness and formula of each layer. At the same time, the functions of the prepared composite films are also quite different, and no anti-puncture and antibacterial effects are reflected.

[0005] Chinese patent CN116178821B discloses an antibacterial and fresh-keeping composite film and its preparation method, which comprises the following raw material components, calculated by weight, 100 parts of polyethylene and 0.01-5 parts of a composite antibacterial agent; the composite antibacterial agent is prepared by the following method: a hydrophobic monofunctional polymerizable monomer, a hydrophobic multifunctional polymerizable monomer, an oil-soluble initiator and an emulsifier are uniformly mixed to obtain an oil phase; water is added to the oil phase to form an emulsion, and the temperature is raised to carry out a polymerization reaction; 10 minutes to 1 hour after the polymerization reaction begins, Quaternary ammonium salt modified inorganic filler; after the polymerization reaction is completed, cooled, and water is removed to obtain; the weight ratio of the hydrophobic monofunctional polymerizable monomer to the hydrophobic multifunctional polymerizable monomer is 100:0.05-2; the quaternary ammonium salt modified inorganic filler is an inorganic filler co-modified with a quaternary ammonium salt functional group and a carbon-carbon unsaturated double bond functional group; this patent uses a quaternary ammonium salt with broad-spectrum antibacterial properties to be grafted onto the surface of a cross-linked microsphere and added to a composite film. The grafting method and reaction mechanism are completely different from those of the present application, and twin-screw extrusion granulation plus film blowing is used.

[0006] Chinese patent CN111393751B discloses an environmentally friendly antibacterial plastic film and its preparation method. The film comprises the following raw materials by weight: 80-110 parts polypropylene, 10-20 parts calcium stearate, 20-40 parts polyvinyl alcohol, 10-20 parts biodegradable material, 5-8 parts calcium carbonate, 1-2 parts silane coupling agent, 2-5 parts curing agent, 7-10 parts plasticizer, 9-12 parts antibacterial agent, 2-4 parts talc, and 3-5 parts carboxymethyl cellulose. The antibacterial agent is a modified copper oxide-titanium dioxide-zinc oxide composite nanofiber. Firstly, the patent uses polypropylene as the film matrix, adding antibacterial fibers, plasticizers, toughening agents, and other fillers, focusing on improving the performance of the PP film itself through additives. Secondly, the patent uses a three-component oxide composite antibacterial agent. Summary of the Invention

[0007] In order to meet the above packaging requirements, the present invention provides a composite film that can achieve antibacterial effect without the use of additional preservatives, and can simultaneously meet the properties of low temperature resistance, puncture resistance, high barrier and antibacterial by relying solely on the film itself.

[0008] To achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A low-temperature-resistant, puncture-resistant antibacterial composite film is a co-extruded composite film of at least seven layers. From the outside to the inside, the first to seventh layers sequentially include a PA (polyamide) layer, a PE (polyethylene) layer, a PP / POE (polypropylene-ethylene octene copolymer) layer, an EVOH (polyethylene-vinyl alcohol copolymer) layer, a PE (polyethylene) layer, a PA (polyamide) layer and a PE (polyethylene) layer. The thickness ratio is (1-1.5): (1.5-2.5): (1-1.5): (0.5-1): (1.5-2.5): (1-1.5): (2-2.5). The total thickness of the composite film is 150μm-350μm.

[0010] Preferably, the first PA layer is made of PA6 (polyamide 6) with a density of 1.12-1.20 g / cm 3 , melting point 215-225℃, relative viscosity 2.85±0.3, water content <0.1%.

[0011] Preferably, the raw materials used for the second PE layer are HDPE (high-density polyethylene), LDPE (low-density polyethylene), LLDPE (linear low-density polyethylene) and TIE (adhesive resin), with a mass ratio of (30-40%): (10-20%): (40-60%): (1-5%), which are blended and then melt-extruded.

[0012] Preferably, the raw materials used for the third PP / POE layer are copolymerized PP and POE in a mass ratio of (30-40%): (60-70%), which are blended and then melt-extruded.

[0013] Preferably, the mass percentage of the ethylene segment (E) in the fourth EVOH layer is 30-45%, and the mass percentage of the vinyl alcohol segment (VA) is 55-70%.

[0014] Preferably, the raw materials used for the fifth PE layer are MLLDPE (metallocene linear low-density polyethylene), LDPE, LLDPE and TIE, with a mass ratio of (5-10%): (60-70%): (20-30%): (1-5%), which are blended and then melt-extruded.

[0015] Preferably, the sixth PA layer is made of PA6 with a density of 1.12-1.20 g / cm 3 , melting point 215-225℃, relative viscosity 2.85±0.3, water content <0.1%.

[0016] Preferably, the raw materials used for the seventh PE layer are MLLDPE, LDPE, LLDPE, TIE, and a nano-zinc oxide antibacterial agent in a mass ratio of (5-10%): (55-65%): (20-30%): (4-6%): (1-3%), which are blended and melt-extruded. The nano-zinc oxide antibacterial agent is prepared by the following steps: dispersing nano-zinc oxide and glutamic acid in water, ball milling for 8-12 hours (to a particle size of 20-100 nm), then adding porous alumina (particle size of 20-80 μm) as a catalyst carrier, mixing, and drying at 140-160°C. The mass ratio of the nano-zinc oxide, glutamic acid, and porous alumina is (8-12):1:(35-45).

[0017] The preparation method of the low-temperature-resistant and puncture-resistant antibacterial composite film of the present invention comprises the following steps: melt-extruding seven raw materials through seven extruders respectively, converging them at a co-extrusion die head, and then blowing, cooling, pulling, drying, and winding to finally obtain a finished product.

[0018] The present invention has the following positive and beneficial effects:

[0019] 1. The bonding between the films of the present invention uses natural adhesive resin, without the need for any solvent, and the base materials and additives used are non-toxic and harmless, meeting the requirements of green, safe, and food-grade contact.

[0020] 2. The preparation process of the composite film of the present invention is simple and easy to operate. The seven layers of film can be extruded by co-extrusion. The antibacterial material can be mixed, ground and dispersed using a ball mill. No additional process is required, and it is easy to realize industrial application.

[0021] 3. To prevent accidental ingestion by children, the composite film of the present invention does not require the addition of additional preservatives and mildew inhibitors. It can be simply melt-extruded through the antimicrobial agent and the seventh PE layer. When the antimicrobial agent comes into contact with bacteria, the released zinc ions can react with the protein groups in the bacterial cells, thereby destroying the spatial structure of the protein, inactivating the protease in the cells and killing the bacteria. After the destruction, the zinc ions will be freed from the bacteria, repeating the sterilization process, and having a long-lasting anti-corrosion and mildew-proof effect.

[0022] 4. The composite film of the present invention has good low-temperature resistance. In actual production, people usually use liquid nitrogen, frozen impregnation liquid and other methods to preserve fruits, so as to inhibit biological respiration, slow down the decay and oxidation rate, and have high requirements for the low-temperature resistance of the material. The composite materials used in the present invention have good low-temperature resistance and low brittle temperature. After the composite film of the present invention is quick-frozen in liquid nitrogen at -80°C, it is transferred to a freezer and stored for 1-14 days. The changes in the mechanical properties of the material are continuously tested, and it is found that the material still has high tensile strength and elongation at break in an ultra-low temperature environment, and there is no cliff-like decline. It can be judged that the film material can be used in liquid nitrogen quick freezing and other frozen storage scenarios.

[0023] 5. The composite film of the present invention has strong puncture resistance. Through multi-layer composite, using highly puncture-resistant material PA as the outer layer and the middle layer, and preparing a PP / POE buffer layer at the same time, the impact resistance and puncture resistance during the vacuum heat sealing process can be greatly improved.

[0024] 6. The composite film of the present invention has a low heat-sealing temperature. Since PE is the innermost material, the composite film can be heat-sealed at temperatures below 110°C, with high heat-sealing strength and good sealing properties. Its application in actual production can reduce energy consumption, thus saving energy and costs.

[0025] 7. The composite film of the present invention has high barrier properties. Using high oxygen barrier materials such as PA and EVOH can effectively retain food odors; using high moisture barrier materials such as PE can effectively prevent water loss.

[0026] Material selection basis

[0027] 1. PA offers excellent toughness, tensile strength, tear resistance, impact resistance, and puncture resistance. It also boasts excellent temperature resistance, is non-toxic, tasteless, and odorless. It also offers excellent barrier properties, fragrance retention, and oil resistance. It also boasts high transparency, excellent gloss, and excellent printability, making it easy to ink and convenient to print. The order of film layers is determined primarily based on PA's printability, low-temperature resistance, and puncture resistance, with PA being used as the outermost layer.

[0028] 2. PE is commonly found in packaging, including HDPE, LDPE, LLDPE, and MLLDPE. They offer excellent low-temperature resistance, good heat-sealing properties, and low cost. HDPE offers high impact strength, while LDPE is soft, has excellent toughness, and offers excellent UV resistance, water, and moisture resistance. The order of film layers is determined by considering PE's excellent heat-sealing properties, low-temperature resistance, and low cost, respectively, with PE being used as the innermost and middle layers.

[0029] 3. PP / POE Composites: Copolymer PP has higher tensile strength, yield strength, and impact strength than standard PP, but its low-temperature toughness is poor. Modifying PP with POE can significantly improve the composite's low-temperature toughness. POE also provides excellent adhesion, acting as a binder to enhance bonding strength with other layers. PP and POE belong to the same polyolefin family and are highly compatible. Adding POE can further enhance the film's gloss and transparency. Considering the film layer sequence, PP / POE is used as the buffer material for the middle layer due to its strong adhesion and high impact strength.

[0030] 4. EVOH has excellent barrier properties and excellent gas barrier effect, making it one of the most commonly used fragrance preservation materials. However, due to its poor moisture resistance, moisture will have a significant impact on its barrier properties, so the film layer sequence should be after the PA or PE layer.

[0031] 5. Due to the miniaturization of nano zinc oxide particles, nano zinc oxide powder produces surface effects, small size effects, quantum effects, etc. that the bulk material does not have. Nano zinc oxide is a common antibacterial agent that kills bacteria by releasing zinc ions to contact proteins. However, when unmodified zinc oxide quantum dots are grafted onto polymers, there are certain problems in biocompatibility and stability. In addition, due to the strong surface activity of zinc oxide quantum dots, they are prone to agglomeration, which deteriorates the dispersion and greatly reduces the antibacterial effect. Therefore, the advantage of using glutamic acid to graft nano zinc oxide is that glutamic acid-modified nano zinc oxide has better biocompatibility and stability than unmodified ones. The principle is that the amino and carboxyl groups on the surface of glutamic acid can form stable chemical bonds with zinc oxide quantum dots. This modification not only improves the biocompatibility of quantum dots, but also enhances their water solubility in the dispersion medium, so that a highly dispersed quantum dot aqueous solution can be obtained. After sufficient dispersion, porous alumina is used for loading and then dried to obtain a porous loaded nano antibacterial agent with a hollow porous nanostructure. The TEM image is shown in the figure below. Figure 2 As shown, the principle diagram of glutamic acid modified nano zinc oxide is as follows Figure 3 shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a processing flow chart of the composite film of the present invention.

[0033] Figure 2 This is a TEM image of the nano zinc oxide antibacterial agent used in the composite film of the present invention.

[0034] Figure 3 This is a schematic diagram of the principle of glutamate-modified nano-zinc oxide.

[0035] Figure 4is a cross-sectional view of the composite film of the present invention;

[0036] Figure 4 Marked as:

[0037] 1-first PA layer;

[0038] 2- second PE layer;

[0039] 3- third PP / POE layer;

[0040] 4- fourth EVOH layer;

[0041] 5-fifth PE layer;

[0042] 6-sixth PA layer;

[0043] 7-Seventh PE layer.

[0044] Figure 5 The graphs of the mechanical properties of the composite film of the present invention when stored at -38°C and at room temperature are corresponding to numbers 1-4 in Table 4;

[0045] Figure 6 This is a comparison of the antibacterial effects of the composite film of comparative example 1 and the composite film of the present invention; the left half is the antibacterial effect of the composite film of comparative example 1, and the right half is the antibacterial effect of the composite film of the present invention.

[0046] Figure 7 This is a picture of the composite film of the present invention being applied to lychee packaging; DETAILED DESCRIPTION

[0047] The manufacturers and performance parameters of the raw materials used in the following embodiments are shown in Table 1. To facilitate the understanding of those skilled in the art, the following is described in conjunction with Examples 1-5 and Comparative Example 1 in Table 2. The temperatures of the extruders for each layer are as follows: the processing temperature of the first and sixth PA layers is 230-240°C; the processing temperature of the second and fifth PE layers is 140-150°C; the processing temperature of the third PP / POE layer is 150-160°C, the processing temperature of the fourth EVOH layer is 180-190°C, and the processing temperature of the seventh PE layer is 170-180°C. The ratio of the thickness of each film layer in the following Examples 1-5 and Comparative Example 1 is uniformly 1:2.5:1.5:1:2.5:1:2.5, and the blow-up ratio is controlled at 2.2-3.0. Furthermore, the nano zinc oxide antibacterial agent (abbreviated as NanoZnO in the table) was prepared as follows: 5 g of nano zinc oxide and 0.5 g of glutamic acid were weighed, dispersed in 300 mL of deionized water, and thoroughly ground in a ball mill for 12 hours. The mixed slurry was then blended with 20 g of porous alumina and spray-dried at 150° C. to obtain a nano zinc oxide antibacterial powder. Comparative Example 1 served as a blank control sample for the antibacterial test. A 7-layer coextruded composite film was extruded using the same method as Example 5, except that no antibacterial agent or additive was added.

[0048] Table 1 Performance parameters of raw materials in the embodiments of the present invention

[0049] Original manufacturer relative density Melt index (190℃, g / 10min) Melting point (℃) PA6 Hunan Yuehua 1.156 - 215-220 HDPE ExxonMobil 0.961 0.70 131 LDPE ExxonMobil 0.912 3.0 112 LLDPE ExxonMobil 0.918 2.8 120 MLLDPE ExxonMobil 0.918 3.5 123 PP Guangzhou Petrochemical 0.900 12 146 POE Mitsui Chemicals 0.870 1.5 85-90 EVOH Japan Kuraray 1.190 1.9 187 TIE DuPont 0.950 2.0 135

[0050] Table 2 Recipe parameters of the embodiment of the present invention

[0051]

[0052]

[0053] After preparing the corresponding composite films, we tested the material properties of Examples 1-5. As shown in Table 3, it can be seen that due to the use of the composite process, Examples 1-5 have excellent comprehensive performance, high tensile strength and toughness, and are good tensile materials; the low water and oxygen permeability reflects the high barrier properties of the composite film, and the high light transmittance improves the overall appearance of the product, allowing the internal color and gloss to be clearly observed when packaging fruits or seafood; the puncture resistance is stronger from the inside to the outside than from the outside to the inside, which can meet the actual vacuum application scenario. Because vacuuming will cause the film to shrink instantly, the inner layer will preferentially contact the part with the thorns for better results.

[0054] Table 3 Material performance test

[0055]

[0056]

[0057] In order to simulate the scenario of low-temperature sealing and storage of food after quick freezing in actual production, we selected the composite film of Example 5, cut it, and placed it in a liquid nitrogen line at -80°C for quick freezing for 15-20 minutes, and then stored it at -38°C for 3-14 days. The sample films were taken out on the 3rd, 7th and 14th days respectively, and the mechanical properties were compared with those of the composite film that was not passed through the quick freezing line and was directly placed at room temperature, and the change trend was shown. The results are as follows: Figure 5 As shown in Table 4 ( Figure 5 The abscissa corresponds to the numbering in Table 4. It can be seen that the tensile strength and elongation at break of the composite film decreased slightly after 3 days of low-temperature storage compared to room temperature, with the tensile strength decreasing by 9.87% and the elongation at break decreasing by 11.96%. However, the mechanical properties did not decrease significantly with continued storage at low temperatures. Compared to 3 days of storage, the tensile strength decreased by 1.46% and the elongation at break decreased by 7.47% after 7 days of low-temperature storage. Compared to 7 days of storage, the tensile strength decreased by 0.74% and the elongation at break decreased by 2.2% after 14 days of low-temperature storage. This indicates that the rate of decline in the film's toughness and strength slowed significantly under low-temperature storage, exhibiting a parabolic pattern with a gradually decreasing slope. This suggests that the material has the potential for long-term storage and packaging at temperatures of -38°C or above, as the mechanical properties do not experience a cliff-like decline at this temperature.

[0058] Table 4 Changes in mechanical properties of materials stored at -38℃

[0059] serial number Storage conditions Storage days Average tensile strength / (N / 15mm) Average elongation at break % 1 Room temperature 0 152 669 2 -38℃ 3 137 589 3 -38℃ 7 135 545 4 -38℃ 14 134 533

[0060] In order to observe the antibacterial effect of the antibacterial film, the film materials prepared in Example 5 and Comparative Example 1 were subjected to antibacterial tests, and the selected bacterial species were Staphylococcus aureus CMCC(B)26003 and Escherichia coli CMCC(B)44102. Figure 6 It reflects the changes in the number of colonies before and after bacterial culture. The first line shows the changes in the number of Escherichia coli colonies before and after, and the second line shows the changes in the number of Staphylococcus aureus colonies before and after. After 24 hours of bacterial culture, the surface of the composite film plastic plate of Comparative Example 1 is covered with colonies, indicating that the composite film without adding an antibacterial agent has no antibacterial property. After 24 hours of bacterial culture, the plastic plate prepared by the nano-antibacterial material composite film of Example 5 has very few bacteria growing on the surface, indicating that the composite film of Example 5 has obvious inhibitory effects on both Escherichia coli and Staphylococcus aureus, indicating that it has excellent antibacterial properties.

[0061] Figure 7 This is an application example of the present invention in products. It is currently mainly used in lychee packaging. It can be used to package lychee varieties with sharp thorns, such as Feizishao and Guiwei, and can achieve good shaping and puncture resistance effects.

[0062] The above embodiments are only representative of the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Various technical features or parameters can be arbitrarily combined. Due to limited space, they are not described in detail here. However, any combination can be made according to the thickness range, component ratio, etc. specified in the present invention. In addition, equivalent changes and modifications, combinations, substitutions, etc. made in accordance with the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A low-temperature-resistant and puncture-resistant antibacterial composite film, comprising at least seven layers of co-extruded composite film, characterized by: The first to seventh layers of the seven-layer co-extruded composite film from the outside to the inside sequentially include a PA layer, a PE layer, a PP / POE layer, an EVOH layer, a PE layer, a PA layer and a PE layer, and the thickness ratio is (1-1.5): (1.5-2.5): (1-1.5): (0.5-1): (1.5-2.5): (1-1.5): (2-2.5); The raw materials used for the second PE layer are high-density polyethylene, low-density polyethylene, linear low-density polyethylene and natural adhesive resin, with a mass ratio of (30-40%): (10-20%): (40-60%): (1-5%), and the sum of the percentages of the above components is 100%; The raw materials used for the fifth PE layer are metallocene linear low-density polyethylene, low-density polyethylene, linear low-density polyethylene and natural adhesive resin, with a mass ratio of (5-10%): (60-70%): (20-30%): (1-5%), and the sum of the percentages of the above components is 100%; The raw materials used for the seventh PE layer are metallocene linear low-density polyethylene, low-density polyethylene, linear low-density polyethylene, natural adhesive resin and nano-zinc oxide antibacterial agent, with a mass ratio of (5-10%): (55-65%): (20-30%): (4-6%): (1-3%), and the sum of the percentages of the above components is 100%; The nano zinc oxide antibacterial agent is prepared by the following steps: dispersing nano zinc oxide and glutamic acid in water, ball milling for 8-12 hours, then adding porous alumina as a catalytic carrier, mixing and drying at 140-160° C. The mass ratio of the nano zinc oxide, glutamic acid and porous aluminum oxide is (8-12):1:(35-45).

2. The antibacterial composite film according to claim 1, characterized in that: The raw material used for the first and sixth PA layers is polyamide 6 with a density of 1.12-1.20 g / cm 3 , melting point 215-225℃, relative viscosity 2.85±0.3, water content <0.1%.

3. The antibacterial composite film according to claim 1, characterized in that: The raw materials used for the third PP / POE layer are copolymerized polypropylene and copolymerized ethylene octene, with a mass ratio of (30-40%): (60-70%).

4. The antibacterial composite film according to claim 1, characterized in that: The raw material of the fourth EVOH layer is ethylene-vinyl alcohol copolymer, wherein the mass percentage of the ethylene segment is 30-45%, and the mass percentage of the vinyl alcohol segment is 55-70%.

5. Use of the antibacterial composite film according to any one of claims 1 to 4 in food packaging.

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