Co-extrusion composite barrier packaging film and preparation process thereof

Abstract

The invention discloses a co-extrusion composite barrier packaging film and a preparation process, and relates to the technical field of packaging films, the co-extrusion composite barrier packaging film comprises 50-60 parts of a polyvinyl alcohol resin layer, 23-27 parts of a bonding resin layer and 18-22 parts of a nylon layer which are sequentially attached and co-extruded from outside to inside; wherein the polyvinyl alcohol resin layer is prepared from the following raw materials in parts by weight: 70wt%-80wt% of polyvinyl alcohol resin, 7wt%-10wt% of antibacterial filler, 8wt%-12wt% of barrier filler and 5wt%-8wt% of modified lignin; and the bonding resin layer is ethylene acrylic resin. According to the co-extrusion composite barrier packaging film and the preparation process, the antibacterial liquid can be uniformly and stably dispersed in a system to form a compact and ordered structure, oxygen is difficult to diffuse due to close combination among molecules, so that the oxygen transmittance is reduced, the barrier property of the packaging film is improved, and meanwhile, tea polyphenol can be mutually matched with other components, so that the barrier property of the packaging film is improved. The ultraviolet blocking capability is enhanced, and the deterioration of products in the package due to ultraviolet irradiation is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging films, and in particular to a co-extruded composite barrier packaging film and a preparation process thereof. Background Art

[0002] Chinese Patent with the publication number CN107554016A discloses a high-toughness and high-barrier plastic packaging film, belonging to the field of packaging films. The high-toughness and high-barrier plastic packaging film includes a central layer and a composite layer; a composite layer is provided outside the central layer; a closed colloid is provided between the central layer and the composite layer; an elastomer is added to the central layer; the central layer and the composite layer are formed by multi-layer co-extrusion. The high-toughness and high-barrier plastic packaging film provided by this invention is further developed based on the films currently produced in the market, improving the toughness and barrier properties of the films. However, the antibacterial performance and degradation performance of the packaging films prepared by the above-mentioned existing technical solutions need to be improved; for this reason, the present invention provides a co-extruded composite barrier packaging film and a preparation process to solve the above problems. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a co-extruded composite barrier packaging film and a preparation process, solving the problems mentioned in the above background art.

[0004] To achieve the above objectives, the present invention is realized through the following technical solutions: A co-extruded composite barrier packaging film includes a polyvinyl alcohol resin layer of 50 - 60 parts, an adhesive resin layer of 23 - 27 parts, and a nylon layer of 18 - 22 parts, which are co-extruded and adhered to each other from outside to inside. Among them, the polyvinyl alcohol resin layer includes raw materials in the following weight parts: 70wt% - 80wt% of polyvinyl alcohol resin, 7wt% - 10wt% of antibacterial filler, 8wt% - 12wt% of barrier filler, and 5wt% - 8wt% of modified lignin; the adhesive resin layer is ethylene acrylic resin. The antibacterial filler is a composite of antibacterial liquid and tea polyphenols, and the mass ratio of antibacterial liquid to tea polyphenols is 4:(1 - 3).

[0005] Preferably, the preparation method of the antibacterial liquid is as follows: S1. Pour 1.5 - 4 g of chitosan into 150 - 160 mL of 1% glacial acetic acid solution, and stir at room temperature for 3.5 - 4 h; S2. Add 7.5 - 10 mL of bacterial cellulose dispersion liquid, heat the water bath to 55 - 65 °C, and stir under constant temperature for 1.8 - 2 h; S3. Add 15 - 20 g of glycerol, homogenize at a rotation speed of 20000 - 25000 r / min, and then perform ultrasonic treatment.

[0006] Preferably, in S3, after every 3 s of ultrasonic treatment, there is an intermittent period of 3 s. The ultrasonic treatment time is 25 - 30 min, and the ultrasonic power is 1000 - 1200 W.

[0007] Preferably, the preparation method of the barrier filler is as follows: (1) Add 80 - 100 μL of laccase to 42 - 50 mL of procyanidin solution, heat up to 37 - 40 °C, and under stirring conditions, introduce oxygen and react for 30 - 40 min to obtain solution A; (2) Add 8 - 10 mL of tetramethylpiperidine nitroxide solution and 80 - 100 μL of laccase solution to 95 - 100 mL of chitosan - acetic acid solution, introduce oxygen and react for 30 - 40 min to obtain solution B; (3) After mixing solutions A and B evenly, add 90 - 100 μL of laccase, heat up to 37 - 40 °C, and under stirring conditions, introduce oxygen and react for 10 - 12 h; (4) First, centrifuge at a speed of 6000 - 8000 r / min for 10 - 15 min, and then place it in a rotary evaporator at 55 - 65 °C to concentrate the supernatant; (5) Add absolute ethanol to precipitate the product. After filtering through a 0.4 - 0.55 μm microporous filter membrane, dissolve the solid product in deionized water, and again use a rotary evaporator to concentrate the filtrate. This step is repeated 2 - 3 times. Finally, dry the solid in a vacuum drying oven at 25 - 35 °C for 2.5 - 3 h to obtain the barrier filler.

[0008] Preferably, in (1) and (3), the stirring speed is 140 - 170 r / min.

[0009] Preferably, the preparation method of the modified lignin is as follows: Ⅰ. Crush and grind 20 - 25 g of corn straw, and then soak it in 1.5 - 2 L of sodium hydroxide solution with a pH value of 11; Ⅱ. Heat the water bath to 70 - 75 °C, soak for 4 - 4.5 h, and then take it out and filter; Ⅲ. Add 1.5 - 2.5 g of calcium chloride solution with a concentration of 0.1 mol / L to the filtrate, and under room temperature conditions, stir and react at a speed of 250 - 300 r / min for 10 - 12 h; Ⅳ. After centrifugation and freeze - drying, add 1 - 2 g of hydrochloric acid, then filter, wash, and freeze - dry to obtain the modified lignin.

[0010] Preferably, in Ⅳ, wash with deionized water 3 - 5 times.

[0011] A preparation process of a co - extruded composite barrier packaging film includes the following preparation steps: Step 1: Pour polyvinyl alcohol resin into 550 - 700 mL of deionized water and mix evenly. Step 2: Add the bacteriostatic solution, heat up to 85 - 95 °C, stir for 2.5 - 3 h, then cool down to 20 - 30 °C, add tea polyphenols and stir evenly. Step 3: Add the barrier filler and modified lignin in sequence, mix evenly, and then feed it into the first screw extruder. The screw temperature of the first screw extruder is 200 - 220 °C, the rotation speed is 35 - 40 r / min, the extrusion pressure is 25 - 30 MPa, and the extrusion temperature is 220 °C to obtain the polyvinyl alcohol resin layer. Step 4: Feed the adhesive resin into the second screw extruder. The screw temperature of the second screw extruder is 220 - 240 °C, the rotation speed is 35 - 37 r / min, the extrusion pressure is 26 - 28 MPa, and the extrusion temperature is 240 °C to obtain the adhesive resin layer. Step 5: Pour nylon particles into the third screw extruder according to the formula amount. The screw temperature of the third screw extruder is 230 - 245 °C, the rotation speed is 50 - 55 r / min, the extrusion pressure is 30 - 33 MPa, and the extrusion temperature is 245 °C to obtain the nylon layer. Step 6: Simultaneously transport the raw materials of the polyvinyl alcohol resin layer, the adhesive resin layer and the nylon layer to the die head of the three - layer co - extrusion machine, and co - extrude and blow - mold them into a film in a molten state to obtain the co - extruded composite barrier packaging film.

[0012] Beneficial Effects The present invention provides a co - extruded composite barrier packaging film and its preparation process. Compared with the prior art, it has the following beneficial effects: (1) For the co - extruded composite barrier packaging film and its preparation process, the bacteriostatic solution can be evenly and stably dispersed in the system to form a dense and orderly structure. The close combination between molecules makes it difficult for oxygen to diffuse, thereby reducing the oxygen transmission rate and improving the barrier performance of the packaging film. At the same time, tea polyphenols can cooperate with other components to enhance the ability to block ultraviolet rays and prevent the products in the package from deteriorating due to ultraviolet irradiation; after chitosan is grafted onto bacterial cellulose molecules, the combination is tighter, making the film denser, thereby reducing the hydrogen bonds combined with water molecules and resulting in a lower water content; due to the similar polysaccharide structure of chitosan and bacterial cellulose, strong interaction occurs between chitosan and glucose chains and bacterial cellulose at the interface, thereby improving the mechanical properties of the composite packaging film; chitosan itself has antibacterial properties and can inhibit the growth and reproduction of various bacteria and fungi, while tea polyphenols are a natural antioxidant with a strong ability to scavenge free radicals, which can prevent the oxidation and deterioration of the contents in the package, and can also inhibit the growth of microorganisms and extend the shelf life of the product.

[0013] (2) The co-extruded composite barrier packaging film and its preparation process can effectively prevent the packaged contents from being oxidized, delay the oxidative rancidity of oils and fats, and extend the shelf life of foods by adding barrier fillers. Moreover, in the packaging film, it can inhibit the growth and reproduction of microorganisms, has a good protective effect on perishable products, and reduces product spoilage caused by microbial growth. At the same time, it can enhance the toughness and strength of the packaging film, making it not easily break when subjected to external forces such as stretching and folding, and can better adapt to various operations during the packaging process and extrusion during transportation. And the barrier fillers will be filled in the polyvinyl alcohol resin to enhance the barrier ability to oxygen, water vapor, etc., so as to better maintain the environmental stability inside the package.

[0014] (3) The co-extruded composite barrier packaging film and its preparation process can form physical entanglements between components such as cellulose in corn straw and polyvinyl alcohol by adding modified lignin, increasing the mechanical strength of the film and making it less likely to break. Moreover, the addition of modified lignin changes the microstructure of the film, making it more dense, thereby improving the barrier performance of the film. Due to the addition of straw components, the film can also have certain biodegradability. Description of the Drawings

[0015] Figure 1 It is the infrared spectrum diagram of sodium montmorillonite and flame retardant filler provided by the present invention. Detailed Embodiments

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] A preparation process of a co-extruded composite barrier packaging film includes the following preparation steps: Step 1: Pour 49 g of polyvinyl alcohol resin into 550 mL of deionized water and mix evenly. Step 2: Add 4 g of bacteriostatic liquid, heat up to 85 °C, stir for 2.5 h, then cool down to 20 °C, add 1 g of tea polyphenol, and stir evenly. Among them, the preparation method of the bacteriostatic liquid is: Pour 1.5 g of chitosan into 150 mL of 1% glacial acetic acid solution, stir at room temperature for 3.5 h; add 7.5 mL of bacterial cellulose dispersion liquid, heat up to 55 °C in a water bath, and stir under constant temperature for 1.8 h; add 15 g of glycerol, homogenize at a speed of 20000 r / min, and then perform ultrasonic treatment. After every 3 s of ultrasonic treatment, there is an intermittent period of 3 s. The ultrasonic time is 25 min and the ultrasonic power is 1000 W. Step 3: 8.4 g of barrier filler and 5.6 g of modified lignin are added in sequence. After mixing evenly, they are fed into the first screw extruder. The screw temperature of the first screw extruder is 200 °C, the rotation speed is 35 r / min, the extrusion pressure is 25 MPa, and the extrusion temperature is 220 °C to obtain a polyvinyl alcohol resin layer; Among them, the preparation method of the barrier filler is as follows: 80 μL of laccase is added to 42 mL of proanthocyanidin solution, and the temperature is raised to 37 °C. Under the stirring condition with a rotation speed of 140 r / min, oxygen is introduced and reacted for 30 min to obtain solution A; 8 mL of tetramethylpiperidine nitroxide solution and 80 μL of laccase solution are added to 95 mL of chitosan-acetic acid solution, and oxygen is introduced and reacted for 30 min to obtain solution B; after mixing solutions A and B evenly, 90 μL of laccase is added, the temperature is raised to 37 °C, and under the stirring condition with a rotation speed of 140 r / min, oxygen is introduced and reacted for 10 h; first, centrifuge at a rotation speed of 6000 r / min for 10 min, and then place it in a rotary evaporator at 55 °C to concentrate the supernatant; anhydrous ethanol is added to precipitate the product, and after filtering through a 0.4-μm microporous filter membrane, the solid product is dissolved in deionized water, and the filtrate is concentrated again using a rotary evaporator. This step is repeated 2 times; finally, the solid is dried in a vacuum drying oven at 25 °C for 2.5 h to obtain the barrier filler; The preparation method of the modified lignin is as follows: 20 g of corn straw is crushed and ground, and then soaked in 1.5 L of sodium hydroxide solution with a pH value of 11; the water bath is heated to 70 °C, taken out and filtered after soaking for 4 h; 1.5 g of calcium chloride solution with a concentration of 0.1 mol / L is added dropwise to the filtrate, and under room temperature conditions, it is stirred and reacted at a rotation speed of 250 r / min for 10 h; after centrifugation and freeze-drying, 1 g of hydrochloric acid is added, and then filtered. After washing 3 times with deionized water, it is freeze-dried to obtain the modified lignin; Step 4: 23 g of ethylene acrylic resin is fed into the second screw extruder. The screw temperature of the second screw extruder is 220 °C, the rotation speed is 35 r / min, the extrusion pressure is 26 MPa, and the extrusion temperature is 240 °C to obtain an adhesive resin layer; Step 5: 18 g of nylon particles are poured into the third screw extruder according to the formula amount. The screw temperature of the third screw extruder is 230 °C, the rotation speed is 50 r / min, the extrusion pressure is 30 MPa, and the extrusion temperature is 245 °C to obtain a nylon layer; Step 6: The raw materials of the polyvinyl alcohol resin layer, the adhesive resin layer and the nylon layer are simultaneously transported to the head of a three-layer co-extrusion machine, and the three raw materials are co-extruded and blown into a film in a molten state to obtain a co-extruded composite barrier packaging film.

[0018] Example 2 A preparation process of a co-extruded composite barrier packaging film includes the following preparation steps: Step 1: Pour 64 g of polyvinyl alcohol resin into 600 mL of deionized water and mix well. Step 2: Add 3.2 g of antibacterial liquid, heat up to 90 °C, stir for 2.7 h, then cool down to 25 °C, add 2.4 g of tea polyphenols and stir evenly. Among them, the preparation method of the antibacterial liquid is as follows: Pour 2.5 g of chitosan into 155 mL of 1% glacial acetic acid solution, and stir at room temperature for 3.8 h; add 9 mL of bacterial cellulose dispersion, heat up to 60 °C in a water bath, and stir under constant temperature for 1.9 h; add 18 g of glycerol, homogenize at a speed of 23000 r / min, then perform ultrasonic treatment, and after every 3 s of ultrasonic treatment, pause for 3 s. The ultrasonic time is 28 min and the ultrasonic power is 1100 W. Step 3: Add 6.4 g of barrier filler and 4 g of modified lignin in sequence, mix well, and then feed it into the first screw extruder. The screw temperature of the first screw extruder is 210 °C, the rotation speed is 38 r / min, the extrusion pressure is 28 MPa, and the extrusion temperature is 220 °C to obtain a polyvinyl alcohol resin layer. Among them, the preparation method of the barrier filler is as follows: Add 90 μL of laccase to 46 mL of proanthocyanidin solution, heat up to 38 °C, and under the stirring condition of a rotation speed of 150 r / min, introduce oxygen and react for 35 min to obtain solution A; add 9 mL of tetramethylpiperidine nitroxide solution and 90 μL of laccase solution to 96 mL of chitosan-acetic acid solution, introduce oxygen and react for 35 min to obtain solution B; mix solutions A and B evenly, add 95 μL of laccase, heat up to 38 °C, and under the stirring condition of a rotation speed of 160 r / min, introduce oxygen and react for 11 h; first centrifuge at a speed of 7000 r / min for 13 min, then place it in a rotary evaporator at 60 °C to concentrate the supernatant; add absolute ethanol to precipitate the product, filter it through a 0.5-μm microporous filter membrane, dissolve the solid product in deionized water, and concentrate the filtrate again using a rotary evaporator. This step is repeated 3 times, and finally dry the solid in a vacuum drying oven at 30 °C for 2.8 h to obtain the barrier filler. The preparation method of the modified lignin is as follows: Crush and grind 23 g of corn straw, and then soak it in 1.7 L of sodium hydroxide solution with a pH value of 11; heat up to 73 °C in a water bath, take it out and filter after soaking for 4.2 h; add 2 g of calcium chloride solution with a concentration of 0.1 mol / L to the filtrate, and stir and react at a rotation speed of 280 r / min at room temperature for 11 h; centrifuge and freeze-dry, then add 1.5 g of hydrochloric acid, filter again, wash 4 times with deionized water and then freeze-dry to obtain the modified lignin. Step 4: Feed 25 g of ethylene acrylic resin into the second screw extruder. The screw temperature of the second screw extruder is 230 °C, the rotation speed is 36 r / min, the extrusion pressure is 27 MPa, and the extrusion temperature is 240 °C to obtain the adhesive resin layer; Step 5: Pour 20 g of nylon particles into the third screw extruder according to the formula amount. The screw temperature of the third screw extruder is 240 °C, the rotation speed is 52 r / min, the extrusion pressure is 32 MPa, and the extrusion temperature is 245 °C to obtain the nylon layer; Step 6: Simultaneously convey the raw materials of the polyvinyl alcohol resin layer, the adhesive resin layer, and the nylon layer to the head of the three-layer co-extrusion machine, and co-extrusion blow molding is performed in a molten state of the three raw materials to obtain the co-extruded composite barrier packaging film.

[0019] Example 3 A preparation process of a co-extruded composite barrier packaging film includes the following preparation steps: Step 1: Pour 52.5 g of polyvinyl alcohol resin into 700 mL of deionized water and mix evenly; Step 2: Add 5 g of bacteriostatic liquid, heat up to 95 °C, stir for 3 h, then cool down to 30 °C, and add 2.5 g of tea polyphenols and stir evenly; Among them, the preparation method of the bacteriostatic liquid is: Pour 4 g of chitosan into 160 mL of 1% glacial acetic acid solution, stir at room temperature for 4 h; add 10 mL of bacterial cellulose dispersion liquid, heat up to 65 °C in a water bath, and stir under constant temperature for 2 h; add 20 g of glycerol, homogenize at a rotation speed of 25000 r / min, and then perform ultrasonic treatment. After every 3 s of ultrasonic treatment, there is an intermittent period of 3 s. The ultrasonic time is 30 min and the ultrasonic power is 1200 W; Step 3: Add 9 g of barrier filler and 6 g of modified lignin in sequence, mix evenly, and feed it into the first screw extruder. The screw temperature of the first screw extruder is 220 °C, the rotation speed is 40 r / min, the extrusion pressure is 30 MPa, and the extrusion temperature is 220 °C to obtain the polyvinyl alcohol resin layer; Among them, the preparation method of the barrier filler is as follows: Add 100 μL of laccase to 50 mL of proanthocyanidin solution, heat up to 40 °C, and under the stirring condition with a rotation speed of 170 r / min, introduce oxygen and react for 40 min to obtain solution A; Add 10 mL of tetramethylpiperidine nitroxide solution and 100 μL of laccase solution to 100 mL of chitosan-acetic acid solution, introduce oxygen and react for 40 min to obtain solution B; After mixing solutions A and B evenly, add 100 μL of laccase, heat up to 40 °C, and under the stirring condition with a rotation speed of 170 r / min, introduce oxygen and react for 12 h; First, centrifuge at a rotation speed of 8000 r / min for 15 min, then place it in a rotary evaporator at 65 °C to concentrate the supernatant; Add absolute ethanol to precipitate the product, filter it through a 0.55-μm microporous filter membrane, dissolve the solid product in deionized water, and concentrate the filtrate again using a rotary evaporator. This step is repeated 3 times. Finally, dry the solid in a vacuum drying oven at 35 °C for 3 h to obtain the barrier filler; The preparation method of the modified lignin is as follows: Crush and grind 25 g of corn straw, and then soak it in 2 L of sodium hydroxide solution with a pH value of 11; Heat up the water bath to 75 °C, take it out and filter after soaking for 4.5 h; Drop 2.5 g of calcium chloride solution with a concentration of 0.1 mol / L into the filtrate, and under room temperature conditions, stir and react at a rotation speed of 300 r / min for 12 h; After centrifugation and freeze-drying, add 2 g of hydrochloric acid, then filter, wash 5 times with deionized water and then freeze-dry to obtain the modified lignin; Step Four: Feed 27 g of ethylene acrylic resin into the second screw extruder. The screw temperature of the second screw extruder is 240 °C, the rotation speed is 37 r / min, the extrusion pressure is 28 MPa, and the extrusion temperature is 240 °C to obtain the adhesive resin layer; Step Five: Pour 22 g of nylon particles into the third screw extruder according to the formula amount. The screw temperature of the third screw extruder is 245 °C, the rotation speed is 55 r / min, the extrusion pressure is 33 MPa, and the extrusion temperature is 245 °C to obtain the nylon layer; Step Six: Simultaneously transport the raw materials of the polyvinyl alcohol resin layer, the adhesive resin layer, and the nylon layer to the head of the three-layer co-extrusion machine, and co-extrusion and blow molding are carried out in a molten state to obtain the co-extruded composite barrier packaging film.

[0020] Comparative Example 1 Compared with Example 1, the difference is that the antibacterial filler is not added; the rest remains unchanged.

[0021] Comparative Example 2 Compared with Example 1, the difference is that tea polyphenols are not added; the rest remains unchanged.

[0022] Comparative Example 3 Compared with Example 1, the difference is that no barrier filler is added; the rest remains unchanged.

[0023] Comparative Example 4 Compared with Example 1, the difference is that no modified lignin is added; the rest remains unchanged.

[0024] Oxygen barrier property test: The test was carried out according to the standard of GB / T1000.4-2008; the results are shown in Table 1; the calculation formula for the oxygen transmission coefficient is: ; In the formula, is the oxygen transmission coefficient, cm 3 ·m / (m 2 ·d·Pa); is the oxygen transmission rate, cm 3 / (cm 2 ·d); is the film thickness, m; is the oxygen pressure difference on both sides of the film, Pa.

[0025] Water vapor barrier property test: The test was carried out according to the standard of GB / T26253-2010, the relative humidity RH was 50%, the test temperature was 25 °C, and the moisture permeability test was started after preheating and equilibration for 1 h; the water vapor transmission rate was directly output by the instrument, and the water vapor transmission coefficient was calculated (the results are shown in Table 1): ; In the formula, is the water vapor transmission coefficient, g·m / (m 2 ·s·Pa); is the water vapor transmission rate, g / (m 2 ·d); is the film thickness, m; is the oxygen pressure difference on both sides of the film, Pa; is the saturated vapor pressure of water at the measurement temperature, Pa; is the relative humidity in the upper part of the test chamber, %; is the relative humidity in the lower part of the test chamber, %.

[0026] Table 1 Tensile strength test: The test was carried out according to the standard of GB / T1040.1-2006; the results are shown in Table 2.

[0027] Antibacterial property test: Using the foodborne pathogen Staphylococcus aureus (S. aureus, Gram-positive bacteria) as the test strain, the test was carried out according to the standard of GB / T21510-2008; the results are shown in Table 2.

[0028] Degradation test: Samples measuring 50 mm × 100 mm were weighed, completely buried in soil samples, and kept at a constant temperature of 23 °C with a constant soil humidity of 17.46%. After 10 days, 20 days, and 40 days, the buried composite films were taken out of the soil, rinsed with deionized water to remove solids such as soil, dried in an oven at 60 °C for 24 h, weighed, and the weight loss rate of the samples was calculated; the results are shown in Table 2.

[0029] Table 2 As Figure 1 shown, sodium-based montmorillonite and modified lignin have some common infrared absorption peaks, namely the -OH stretching vibration peaks (around 3600, 3400 cm -1 ), the Si-O stretching vibration peak (around 1011 cm -1 ), and the Al-O stretching vibration peak (around 696 cm -1 ). The presence of these peaks proves that the basic structure of sodium-based montmorillonite was not damaged during the reaction. Different from this, new absorption peaks appear at 2368.5, 2322.2, 1635.6, 910.42, 802.38 cm -1 etc. in the phosphocholine-modified sodium-based montmorillonite. These peaks correspond to the absorption peaks of -CH 3 , -CH 2 , -N-CH 3 , P=O, and P-O, which are all characteristic peaks of phosphocholine, indicating that the phosphocholine group is inserted into the interlayer of sodium-based montmorillonite to form a phosphocholine sodium-based montmorillonite composite material.

[0030] Meanwhile, the content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0031] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including", or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or device.

[0032] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A co-extruded composite barrier packaging film, characterized in that: The invention comprises 70-80 parts of a coextruded polyvinyl alcohol resin layer, 23-27 parts of an adhesive resin and 18-22 parts of nylon particles which are sequentially attached from outside to inside; The polyvinyl alcohol resin layer comprises the following raw materials in parts by weight: polyvinyl alcohol resin 70wt%-80wt%, antibacterial filler 7wt%-10wt%, modified lignin 8wt%-12wt%, modified lignin 5wt%-8wt%; the adhesive resin is ethylene acrylic resin; The antibacterial filler is a complex of antibacterial liquid and tea polyphenols, and the mass ratio of the antibacterial liquid to the tea polyphenols is 4:(1-3).

2. The co-extruded composite barrier packaging film according to claim 1, characterized in that: The preparation method of the antibacterial liquid is: S1. Pour 1.5-4 g of chitosan into 150-160 mL of 1% glacial acetic acid solution and stir at room temperature for 3.5-4 h; S2, add 7.5-10mL of bacterial cellulose dispersion, heat to 55-65°C in a water bath, and stir at a constant temperature for 1.8-2h; S3. Add 15-20 g of glycerol, homogenize at a speed of 20,000-25,000 r / min, and then perform ultrasonic treatment.

3. The co-extruded composite barrier packaging film according to claim 2, characterized in that: In S3, after each ultrasonic treatment for 3 seconds, there is a rest period of 3 seconds. The ultrasonic time is 25-30 minutes and the ultrasonic power is 1000-1200W.

4. The co-extruded composite barrier packaging film according to claim 1, characterized in that: The preparation method of the barrier filler is: (1) adding 80-100 μL of laccase to 42-50 mL of proanthocyanidin solution, heating to 37-40° C., introducing oxygen under stirring for 30-40 min to prepare solution A; (2) adding 8-10 mL of tetramethylpiperidinium N-oxide solution and 80-100 μL of laccase solution to 95-100 mL of chitosan-acetic acid solution, introducing oxygen to react for 30-40 min, and preparing solution B; (3) After mixing solutions A and B evenly, add 90-100 μL of laccase, raise the temperature to 37-40°C, and introduce oxygen under stirring for 10-12 hours; (4) centrifuging at 6000-8000 r / min for 10-15 min, and then concentrating the supernatant in a rotary evaporator at 55-65° C.; (5) Anhydrous ethanol is added to precipitate the product, and after filtering through a 0.4-0.55 um microporous filter membrane, the solid product is dissolved in deionized water, and the filtrate is concentrated again using a rotary evaporator. This step is repeated 2-3 times, and finally the solid is dried in a vacuum drying oven at 25-35° C. for 2.5-3 hours to obtain a barrier filler.

5. The co-extruded composite barrier packaging film according to claim 4, characterized in that: In (1) and (3), the rotation speed during stirring is 140-170 r / min.

6. The co-extruded composite barrier packaging film according to claim 1, characterized in that: The preparation method of the modified lignin is: Ⅰ. Grind 20-25g corn stalks, and then soak them in 1.5-2L sodium hydroxide solution with a pH value of 11; Ⅱ. Heat the water bath to 70-75℃, soak for 4-4.5h, then take out and filter; III. Add 1.5-2.5 g of 0.1 mol / L calcium chloride solution to the filtrate, and stir at 250-300 r / min for 10-12 h at room temperature; IV. After centrifugation and freeze-drying, add 1-2 g of hydrochloric acid, filter, wash and freeze-dry to obtain modified lignin.

7. The co-extruded composite barrier packaging film according to claim 6, characterized in that: In the IV, deionized water is used for washing 3-5 times.

8. A process for preparing the co-extruded composite barrier packaging film according to claim 1, characterized in that: The method comprises the following preparation steps: Step 1: Pour polyvinyl alcohol resin into 550-700 mL of deionized water and mix well; Step 2: Add antibacterial solution, raise the temperature to 85-95°C, stir for 2.5-3h, then cool to 20-30°C, add tea polyphenols, and stir evenly; Step 3: adding barrier filler and modified lignin in sequence, mixing, and then feeding into a first screw extruder, wherein the screw temperature of the first screw extruder is 200-220°C, the speed is 35-40r / min, the extrusion pressure is 25-30MPa, and the extrusion temperature is 220°C, to obtain a polyvinyl alcohol resin layer; Step 4: feeding the adhesive resin into a second screw extruder, wherein the screw temperature of the second screw extruder is 220-240° C., the rotation speed is 35-37 r / min, the extrusion pressure is 26-28 MPa, and the extrusion temperature is 240° C., to obtain an adhesive resin layer; Step 5, pouring nylon particles into the third screw extruder according to the formula amount, the screw temperature of the third screw extruder is 230-245°C, the speed is 50-55r / min, the extrusion pressure is 30-33MPa, and the extrusion temperature is 245°C to obtain a nylon layer; Step 6: The raw materials of the polyvinyl alcohol resin layer, the adhesive resin layer and the nylon layer are simultaneously conveyed to the die head of the three-layer co-extruder, and the three raw materials are co-extruded in a molten state to form a blown film, thereby obtaining a co-extruded composite barrier packaging film.

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