A recyclable high barrier packaging film and preparation method thereof

Abstract

The present invention belongs to the technical field of packaging films, and provides a recyclable high-barrier packaging film and a preparation method thereof, wherein the recyclable high-barrier packaging film comprises an outer substrate layer, a barrier layer and an inner substrate layer from the outside to the inside; the barrier layer comprises the following raw materials by weight: 60-75 parts of ethylene-vinyl alcohol copolymer, 10-13 parts of polyvinyl alcohol, 2-5 parts of modified hexagonal boron nitride, 2-3 parts of maleic anhydride grafted polypropylene, 0.5-0.6 parts of plasticizer, and 0.01-0.1 parts of antioxidant; the preparation steps of modified hexagonal boron nitride are as follows: adding hexagonal boron nitride to an ethanol aqueous solution, heating to 65-70°C under a nitrogen atmosphere, reflux stirring, adding modified sodium lignin sulfonate, adjusting the pH value, continuing reflux stirring, cooling to room temperature, washing and filtering, and drying until constant weight to obtain modified hexagonal boron nitride. The recyclable high-barrier packaging film prepared by the present invention has excellent barrier properties, mechanical properties and antibacterial properties.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging films, and particularly relates to a recyclable high-barrier packaging film and a preparation method thereof. Background Art

[0002] Packaging films are widely used in various fields of life, such as food, medicine and cosmetics. Their main purpose is to protect products and prevent them from absorbing moisture, getting damp and oxidizing, which will lead to their deterioration. In different fields of use, there are different requirements for packaging films. For example, medical products usually require packaging films to have antibacterial and good water and oxygen barrier properties, while electronic products require packaging films to have puncture resistance and antistatic properties. However, for most food packaging films, water and oxygen barrier properties are an important indicator to measure the performance of packaging films, especially for some products that are easily affected by moisture and oxidation, such as biscuits, potato chips, etc. In today's booming industry, plastic packaging has become an indispensable part of food, medicine, daily chemical packaging and other systems. It should not only play the role of preserving quality and freshness, but also have the function of reducing its plastic footprint, and plastics should be recyclable or reusable.

[0003] At present, the high barrier packaging film on the market often uses aluminum foil as the water and oxygen barrier layer, and has a multi-layer composite structure of outer protective layer / adhesive / aluminum foil / adhesive / heat sealing layer. In actual application, this composite packaging film is easy to deform, break, and delaminate under the action of heat and external force, which damages the barrier performance of the composite film and greatly shortens its service life. In addition, although aluminum foil packaging film has excellent water and oxygen barrier performance, it is very difficult to recycle and reuse, and the sorting and classification process after use is cumbersome and difficult, and the recycling rate is low. Summary of the invention

[0004] The object of the present invention is to provide a recyclable high-barrier packaging film and a preparation method thereof, so as to solve the problem of poor barrier properties of the high-barrier packaging film.

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

[0006] The first aspect of the present invention provides a recyclable high barrier packaging film, which comprises an outer substrate layer, a barrier layer and an inner substrate layer from the outside to the inside; the barrier layer comprises the following raw materials in parts by weight:

[0007] 60-75 parts of ethylene-vinyl alcohol copolymer, 10-13 parts of polyvinyl alcohol, 2-5 parts of modified hexagonal boron nitride, 2-3 parts of maleic anhydride grafted polypropylene, 0.5-0.6 parts of plasticizer, 0.01-0.1 parts of antioxidant;

[0008] The preparation steps of the modified hexagonal boron nitride are as follows:

[0009] Add hexagonal boron nitride to ethanol aqueous solution, heat to 65-70°C under nitrogen atmosphere, reflux with stirring for 1-1.5h, add modified sodium lignin sulfonate, adjust the pH value to 3.0-3.2, continue reflux with stirring for 3-4h, cool to room temperature, wash and filter, and dry until constant weight to obtain modified hexagonal boron nitride.

[0010] In some embodiments of the present invention, the usage ratio of hexagonal boron nitride, ethanol aqueous solution and modified sodium lignin sulfonate is 6.0-7.0 g:500 mL:14-16 g.

[0011] In some embodiments of the present invention, the preparation steps of the modified sodium lignin sulfonate are as follows:

[0012] Sodium lignin sulfonate is added to deionized water, ultrasonically dispersed until uniform, octadecylamine and formaldehyde are added, the pH value is adjusted to 10-12, the temperature is raised to 80-85°C, refluxed and stirred for reaction for 10-11 hours, cooled to room temperature, precipitated by ethanol, centrifuged, washed, and vacuum dried to obtain modified sodium lignin sulfonate. Since sodium lignin sulfonate contains a large number of hydroxyl groups and has a large hygroscopicity, the present invention grafts octadecylamine on sodium lignin sulfonate through a chemical reaction, and the surface energy of octadecylamine with a long alkyl chain is low, which improves the hydrophobicity and stability of sodium lignin sulfonate and further improves the dispersibility in the polymer.

[0013] In some embodiments of the present invention, the usage ratio of sodium lignin sulfonate, deionized water, octadecylamine and formaldehyde is 0.30-0.32 g:100 mL:0.85-0.90 g:0.45-0.50 g.

[0014] In some embodiments of the present invention, the plasticizer is one of triethyl citrate, tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. The addition of the plasticizer can improve the elongation, flexibility and toughness of the material.

[0015] In some embodiments of the present invention, the antioxidant is one of antioxidant 1010, antioxidant 168, and antioxidant 1076. The addition of the antioxidant not only improves the antioxidant capacity of EVOH, but also improves the flexibility and tensile strength of the film material.

[0016] In some embodiments of the present invention, the outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0017] 60-75 parts of low-density polyethylene, 8-12 parts of high-density polyethylene, 3-5 parts of ethylene-vinyl acetate copolymer, and 1-3 parts of maleic anhydride grafted polyethylene.

[0018] In some embodiments of the present invention, the density of the low-density polyethylene is 0.91-0.92 g / cm3 The density of high-density polyethylene is 0.95-0.96g / cm 3 The blending of low-density polyethylene and high-density polyethylene can not only improve the mechanical properties and comprehensive properties of the membrane material, but also optimize the processing performance and improve the chemical resistance and durability of the membrane material.

[0019] In some embodiments of the present invention, the thickness of the outer substrate layer is 30-45 μm, the thickness of the barrier layer is 20-35 μm, and the thickness of the inner substrate layer is 30-45 μm.

[0020] A second aspect of the present invention provides a method for preparing a recyclable high-barrier packaging film, comprising the following steps:

[0021] Step 1, respectively mixing the raw materials of the outer substrate layer, the barrier layer and the inner substrate layer in parts by weight, and respectively adding them into a twin-screw extruder for melt plasticization;

[0022] Step 2, the melted and plasticized raw materials of the outer substrate layer, the barrier layer and the inner substrate layer are respectively extruded from the corresponding twin-screw extruders to converge into a die head to form a three-layer composite structure, and then cooled by a cooling roller to form a film with a three-layer co-extruded structure;

[0023] Step 3, preheating the obtained film, biaxially stretching it, and heat setting it;

[0024] Step 4: The stretched film is corona treated or flame treated and then rolled up to obtain a recyclable high barrier packaging film.

[0025] Beneficial effects of the present invention:

[0026] The recyclable high barrier packaging film provided in the present invention comprises an outer substrate layer, a barrier layer and an inner substrate layer from the outside to the inside, and is subjected to co-extrusion blow molding and biaxial stretching, and the recyclable high barrier packaging film finally prepared has excellent barrier properties, mechanical properties and antibacterial properties. At the same time, the preparation method is simple, easy to operate, suitable for large-scale production, and when recycled, the separation between layers can be easily achieved, and each film layer can be reused after separation and recycling, which is beneficial to the environment and saves resources.

[0027] The barrier layer in the present invention uses ethylene-vinyl alcohol copolymer (EVOH) as the main material, and adds polyvinyl alcohol, modified hexagonal boron nitride, polypropylene grafted maleic anhydride, plasticizer and antioxidant. The prepared barrier layer has higher strength and toughness than the traditional polyethylene layer, and the oxygen permeability is also greatly reduced. At the same time, it also has a certain antibacterial effect. Although ethylene-vinyl alcohol copolymer has very good processability and very good oxygen barrier properties, it has the defects of insufficient mechanical strength and heat resistance. Therefore, the present invention adds modified hexagonal boron nitride, and the modified hexagonal boron nitride can not only effectively improve the barrier properties of the composite material, but also enhance the mechanical strength and heat resistance of ethylene-vinyl alcohol copolymer. In addition, the antibacterial properties of the barrier layer are also enhanced.

[0028] Hexagonal boron nitride is introduced as a filler, which has excellent barrier properties for oxygen and water vapor small molecules, and also has excellent thermal conductivity. Introducing hexagonal boron nitride into the raw material can effectively improve the barrier properties and thermal stability. However, due to the strong interlayer force of two-dimensional materials, adding boron nitride is prone to agglomeration, increasing the interface pore defects between boron nitride and polymer and the interface pore defects between boron nitride and boron nitride, which leads to a decrease in the barrier properties of the composite material. Therefore, the present invention adopts modified sodium lignin sulfonate to improve the dispersibility of hexagonal boron nitride. Sodium lignin sulfonate with a benzene ring structure produces a strong π-π interaction with hexagonal boron nitride. At the same time, the modified sodium lignin sulfonate has excellent hydrophobic properties, which enhances the hydrophobic interaction between sodium lignin sulfonate and hexagonal boron nitride, so that the modified sodium lignin sulfonate is effectively adsorbed on the surface of hexagonal boron nitride, thereby providing a "pulling" driving force for the peeling of hexagonal boron nitride, expanding the interlayer spacing of hexagonal boron nitride, improving the dispersibility and compatibility of hexagonal nitride, making it uniformly dispersed in the polymer, forming a tight cross-linking with ethylene-vinyl alcohol copolymer, and constructing a dense barrier network, further reducing the oxygen permeability and water vapor permeability. At the same time, the mechanical properties of the barrier layer are enhanced. In addition, since sodium lignin sulfonate has excellent antibacterial properties, it gives hexagonal boron nitride a certain antibacterial effect, thereby enhancing the antibacterial property of the barrier film. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a modified hexagonal boron nitride, and the preparation steps are as follows:

[0032] S1. Add 0.30 g of sodium lignin sulfonate to 100 mL of deionized water, disperse it evenly by ultrasonication, add 0.85 g of octadecylamine and 0.45 g of formaldehyde, adjust the pH value to 10 with sodium hydroxide solution, heat to 80 ° C, reflux and stir to react for 10 h, cool to room temperature, precipitate the product with ethanol, centrifuge, wash, and dry in a vacuum drying oven at 45 ° C for 24 h to obtain modified sodium lignin sulfonate;

[0033] S2. Add 6.0 g of hexagonal boron nitride to 500 mL of ethanol-water solution (the volume ratio of anhydrous ethanol to deionized water is 1:4), heat to 65 °C under nitrogen atmosphere, reflux with stirring for 1 h, add 14 g of modified sodium lignin sulfonate, adjust the pH value to 3.0 with dilute hydrochloric acid, continue to reflux with stirring for 3 h, cool to room temperature, wash with deionized water and filter, dry until constant weight, and finally obtain modified hexagonal boron nitride.

[0034] Example 2

[0035] This embodiment provides a modified hexagonal boron nitride, and the preparation steps are as follows:

[0036] S1. Add 0.3 g of sodium lignin sulfonate to 100 mL of deionized water, disperse it by ultrasonication until it is uniform, add 0.88 g of octadecylamine and 0.45 g of formaldehyde, adjust the pH value to 10 with sodium hydroxide solution, heat to 80 ° C, reflux and stir to react for 10 hours, cool to room temperature, precipitate the product with ethanol, centrifuge, wash, and place in a vacuum drying oven at 45 ° C for 24 hours to obtain modified sodium lignin sulfonate;

[0037] S2. Add 6.5 g of hexagonal boron nitride to 500 mL of ethanol-water solution (the volume ratio of anhydrous ethanol to deionized water is 1:4), heat to 65 °C under nitrogen atmosphere, reflux with stirring for 1 h, add 15 g of modified sodium lignin sulfonate, adjust the pH value to 3.0 with dilute hydrochloric acid, continue to reflux with stirring for 3 h, cool to room temperature, wash with deionized water and filter, dry until constant weight, and finally obtain modified hexagonal boron nitride.

[0038] Example 3

[0039] This embodiment provides a modified hexagonal boron nitride, and the preparation steps are as follows:

[0040] S1. Add 0.32 g of sodium lignin sulfonate to 100 mL of deionized water, disperse it evenly by ultrasonication, add 0.90 g of octadecylamine and 0.50 g of formaldehyde, adjust the pH value to 10 with sodium hydroxide solution, heat to 80 ° C, reflux and stir to react for 10 h, cool to room temperature, precipitate the product with ethanol, centrifuge, wash, and dry in a vacuum drying oven at 45 ° C for 24 h to obtain modified sodium lignin sulfonate;

[0041] S2. Add 7.0 g of hexagonal boron nitride to 500 mL of ethanol-water solution (the volume ratio of anhydrous ethanol to deionized water is 1:4), heat to 65 °C under nitrogen atmosphere, reflux with stirring for 1 h, add 16 g of modified sodium lignin sulfonate, adjust the pH value to 3.0 with dilute hydrochloric acid, continue to reflux with stirring for 3 h, cool to room temperature, wash with deionized water and filter, dry until constant weight, and finally obtain modified hexagonal boron nitride.

[0042] Comparative Example 1

[0043] This comparative example provides a modified hexagonal boron nitride, and the preparation steps are as follows:

[0044] 6.0 g of hexagonal boron nitride was added to 500 mL of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 1:4), the temperature was raised to 65 ° C under nitrogen atmosphere, refluxed and stirred for 1 h, 14 g of sodium lignin sulfonate was added, the pH value was adjusted to 3.0 with dilute hydrochloric acid, refluxed and stirred for 3 h, cooled to room temperature, washed with deionized water and filtered, dried until constant weight, and finally modified hexagonal boron nitride was obtained.

[0045] Comparative Example 2

[0046] This comparative example provides a modified hexagonal boron nitride, and the preparation steps are as follows:

[0047] 6.0 g of hexagonal boron nitride was added to 500 mL of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 1:4), the temperature was raised to 65°C under nitrogen atmosphere, refluxed and stirred for 4 h, cooled to room temperature, washed with deionized water and filtered, and dried until constant weight was obtained to obtain modified hexagonal boron nitride.

[0048] Example 4

[0049] This embodiment provides a recyclable high barrier packaging film:

[0050] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0051] The barrier layer comprises the following raw materials in parts by weight:

[0052] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 2 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010;

[0053] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0054] Low-density polyethylene (density 0.91g / cm3 ) 60 parts, high-density polyethylene (density 0.95g / cm 3 ) 8 parts, ethylene-vinyl acetate copolymer 3 parts, maleic anhydride grafted polyethylene 1 part.

[0055] The preparation steps of the above-mentioned recyclable high barrier packaging film are as follows:

[0056] Step 1, respectively mixing the raw materials of the outer substrate layer, the barrier layer and the inner substrate layer in parts by weight, and respectively adding them into a twin-screw extruder for melt plasticization;

[0057] Step 2, the melted and plasticized raw materials of the outer substrate layer, the barrier layer and the inner substrate layer are respectively extruded from the corresponding twin-screw extruders to converge into a die head to form a three-layer composite structure, and then cooled by a cooling roller to form a film with a three-layer co-extruded structure;

[0058] Step 3, preheating the obtained film, biaxially stretching it, and heat setting it;

[0059] Step 4: The stretched film is corona treated or flame treated and then rolled up to obtain a recyclable high barrier packaging film.

[0060] Example 5

[0061] This embodiment provides a recyclable high barrier packaging film, which is different from the embodiment 4 only in that:

[0062] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0063] The barrier layer comprises the following raw materials in parts by weight:

[0064] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 3.5 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010;

[0065] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0066] Low-density polyethylene (density 0.91g / cm 3 ) 60 parts, high-density polyethylene (density 0.95g / cm 3 ) 8 parts, ethylene-vinyl acetate copolymer 3 parts, maleic anhydride grafted polyethylene 1 part.

[0067] Example 6

[0068] This embodiment provides a recyclable high barrier packaging film, which is different from the embodiment 4 only in that:

[0069] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0070] The barrier layer comprises the following raw materials in parts by weight:

[0071] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 5 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010;

[0072] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0073] Low-density polyethylene (density 0.91g / cm 3 ) 60 parts, high-density polyethylene (density 0.95g / cm 3 ) 8 parts, ethylene-vinyl acetate copolymer 3 parts, maleic anhydride grafted polyethylene 1 part.

[0074] Example 7

[0075] This embodiment provides a recyclable high barrier packaging film, which is different from the embodiment 4 only in that:

[0076] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0077] The barrier layer comprises the following raw materials in parts by weight:

[0078] 75 parts of ethylene-vinyl alcohol copolymer, 13 parts of polyvinyl alcohol, 5 parts of modified hexagonal boron nitride in Example 2, 3 parts of maleic anhydride grafted polypropylene, 0.6 parts of triethyl citrate, and 0.1 parts of antioxidant 1010;

[0079] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0080] Low-density polyethylene (density 0.91g / cm 3 ) 75 parts, high-density polyethylene (density 0.95g / cm 3 ) 12 parts, ethylene-vinyl acetate copolymer 5 parts, maleic anhydride grafted polyethylene 3 parts.

[0081] Example 8

[0082] This embodiment provides a recyclable high barrier packaging film, which is different from the embodiment 4 only in that:

[0083] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0084] The barrier layer comprises the following raw materials in parts by weight:

[0085] 65 parts of ethylene-vinyl alcohol copolymer, 13 parts of polyvinyl alcohol, 2 parts of modified hexagonal boron nitride in Example 3, 3 parts of maleic anhydride grafted polypropylene, 0.55 parts of triethyl citrate, and 0.03 parts of antioxidant 1010;

[0086] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0087] Low-density polyethylene (density 0.92g / cm 3 ) 65 parts, high-density polyethylene (density 0.96g / cm 3 ) 10 parts, ethylene-vinyl acetate copolymer 5 parts, maleic anhydride grafted polyethylene 2 parts.

[0088] Example 9

[0089] This embodiment provides a recyclable high barrier packaging film, which is different from the embodiment 4 only in that:

[0090] A recyclable high-barrier packaging film comprises, from outside to inside, an outer substrate layer (30 μm thick), a barrier layer (20 μm thick) and an inner substrate layer (30 μm thick).

[0091] The barrier layer comprises the following raw materials in parts by weight:

[0092] 75 parts of ethylene-vinyl alcohol copolymer, 13 parts of polyvinyl alcohol, 5 parts of modified hexagonal boron nitride in Example 3, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.04 parts of antioxidant 1010;

[0093] The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight:

[0094] Low-density polyethylene (density 0.92g / cm 3 ) 65 parts, high-density polyethylene (density 0.95g / cm 3 ) 10 parts, ethylene-vinyl acetate copolymer 4 parts, maleic anhydride grafted polyethylene 2 parts.

[0095] Comparative Example 3

[0096] Compared with Example 4, the only difference is that the modified hexagonal boron nitride used in the barrier layer raw material is different:

[0097] The barrier layer comprises the following raw materials in parts by weight:

[0098] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 2 parts of modified hexagonal boron nitride in Comparative Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0099] Comparative Example 4

[0100] Compared with Example 4, the only difference is that the modified hexagonal boron nitride used in the barrier layer raw material is different:

[0101] The barrier layer comprises the following raw materials in parts by weight:

[0102] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 2 parts of modified hexagonal boron nitride in Comparative Example 2, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0103] Comparative Example 5

[0104] Compared with Example 4, the only difference is that no modified hexagonal boron nitride is added to the barrier layer raw material:

[0105] The barrier layer comprises the following raw materials in parts by weight:

[0106] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0107] Comparative Example 6

[0108] Compared with Example 4, the only difference is that the amount of modified boron nitride in the barrier layer raw material is different:

[0109] The barrier layer comprises the following raw materials in parts by weight:

[0110] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 0.5 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0111] Comparative Example 7

[0112] Compared with Example 4, the only difference is that the amount of modified boron nitride in the barrier layer raw material is different:

[0113] The barrier layer comprises the following raw materials in parts by weight:

[0114] 60 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 6.5 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0115] Comparative Example 8

[0116] Compared with Example 4, the only difference is that the amount of the barrier layer raw material is different:

[0117] The barrier layer comprises the following raw materials in parts by weight:

[0118] 45 parts of ethylene-vinyl alcohol copolymer, 10 parts of polyvinyl alcohol, 2 parts of modified hexagonal boron nitride in Example 1, 2 parts of maleic anhydride grafted polypropylene, 0.5 parts of triethyl citrate, and 0.01 parts of antioxidant 1010.

[0119] Comparative Example 9

[0120] Compared with Example 4, the only difference is that the amount of raw materials used in the outer substrate layer and the inner substrate layer is different:

[0121] Low-density polyethylene (density 0.91g / cm 3 ) 40 parts, high-density polyethylene (density 0.95g / cm 3 ) 8 parts, ethylene-vinyl acetate copolymer 3 parts, maleic anhydride grafted polyethylene 1 part.

[0122] The recyclable high barrier packaging films obtained in Examples 4 to 9 and Comparative Examples 3 to 9 were subjected to the following performance tests: mechanical properties test according to GB / T 10801-2006 standard; water vapor transmission rate test according to GB / T 1037-1988 standard; oxygen transmission rate test according to GB / T 1038-1988 standard; antibacterial performance test according to GB / T 37206-2018 standard. The test results are shown in Table 1:

[0123]

[0124] It can be seen from the data in Table 1 that the recyclable high barrier packaging films prepared in Examples 4-9 have excellent tensile strength, elongation at break and antibacterial properties, and the oxygen permeability is not higher than 0.09 mL / m 2 24h, water vapor transmission rate is not higher than 0.17g / m 2 24h, with excellent barrier properties.

[0125] It can be seen from Comparative Examples 3-5 and Example 4 that the modified hexagonal boron nitride in Comparative Example 1 is added to the barrier layer raw material in Comparative Example 3 (only sodium lignin sulfonate is used for intercalation modification), the modified boron nitride in Comparative Example 2 is added to the barrier layer raw material in Comparative Example 4 (modified sodium lignin sulfonate is not used for intercalation modification), and the modified hexagonal boron nitride is not added to the barrier layer raw material in Comparative Example 5. The mechanical properties, antibacterial properties and barrier properties of the finally obtained recyclable high barrier packaging film are all lower than those in Example 4. It can be seen that the hexagonal boron nitride modified by the intercalation of modified sodium lignin sulfonate can be uniformly dispersed in the barrier layer raw material, and at the same time, the compatibility of hexagonal boron nitride with the polymer is greatly improved, so that the hexagonal boron nitride can effectively improve the barrier properties of the composite material, and can also enhance the mechanical strength and heat resistance of the ethylene-vinyl alcohol copolymer and the antibacterial properties of the barrier layer.

[0126] It can be seen from Comparative Examples 6-9 and Example 4 that the amount of modified boron nitride in the barrier layer raw materials in Comparative Examples 6-7 is outside the range provided in the present invention, the amount of raw materials in the barrier layer raw materials in Comparative Example 8 is outside the range provided in the present invention, and the amount of raw materials in the outer substrate layer and the inner substrate layer in Comparative Example 9 is outside the range provided in the present invention. It can be seen from the data in Table 1 that the mechanical properties, antibacterial properties and barrier properties in Comparative Examples 6-9 are also lower than those in Example 4. Therefore, the use and proportion of raw materials in each layer in the process of preparing a recyclable high-barrier packaging film will affect the mechanical properties, antibacterial properties and barrier properties of the packaging film.

[0127] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0128] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0129] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0130] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A recyclable high barrier packaging film, characterized in that: From outside to inside, it includes an outer substrate layer, a barrier layer and an inner substrate layer; the barrier layer includes the following raw materials by weight: 60-75 parts of ethylene-vinyl alcohol copolymer, 10-13 parts of polyvinyl alcohol, 2-5 parts of modified hexagonal boron nitride, 2-3 parts of maleic anhydride grafted polypropylene, 0.5-0.6 parts of plasticizer, 0.01-0.1 parts of antioxidant; The preparation steps of the modified hexagonal boron nitride are as follows: Add hexagonal boron nitride to ethanol aqueous solution, heat to 65-70°C under nitrogen atmosphere, reflux and stir for 1-1.5h, add modified sodium lignin sulfonate, adjust pH to 3.0-3.2, continue reflux and stir for 3-4h, cool to room temperature, wash and filter, and dry until constant weight to obtain modified hexagonal boron nitride; The preparation steps of the modified sodium lignin sulfonate are as follows: Sodium lignin sulfonate is added into deionized water, ultrasonically dispersed until uniform, octadecylamine and formaldehyde are added, the pH value is adjusted to 10-12, the temperature is raised to 80-85° C., refluxed and stirred for reaction for 10-11 hours, cooled to room temperature, precipitated the product with ethanol, centrifuged, washed, and vacuum dried to obtain modified sodium lignin sulfonate.

2. The recyclable high barrier packaging film according to claim 1, characterized in that: The dosage ratio of hexagonal boron nitride, ethanol aqueous solution and modified sodium lignin sulfonate is 6.0-7.0 g: 500 mL: 14-16 g.

3. The recyclable high barrier packaging film according to claim 1, characterized in that: The dosage ratio of sodium lignin sulfonate, deionized water, octadecylamine and formaldehyde is 0.30-0.32 g: 100 mL: 0.85-0.90 g: 0.45-0.50 g.

4. The recyclable high barrier packaging film according to claim 1, characterized in that: The plasticizer is one of triethyl citrate, tributyl citrate, acetyl triethyl citrate and acetyl tributyl citrate.

5. The recyclable high barrier packaging film according to claim 1, characterized in that: The antioxidant is one of antioxidant 1010, antioxidant 168 and antioxidant 1076.

6. The recyclable high barrier packaging film according to claim 1, characterized in that: The outer substrate layer and the inner substrate layer include the following raw materials in parts by weight: 60-75 parts of low-density polyethylene, 8-12 parts of high-density polyethylene, 3-5 parts of ethylene-vinyl acetate copolymer, and 1-3 parts of maleic anhydride grafted polyethylene.

7. The recyclable high barrier packaging film according to claim 6, characterized in that: The density of the low-density polyethylene is 0.91-0.92 g / cm 3 The density of high-density polyethylene is 0.95-0.96g / cm 3 .

8. The recyclable high barrier packaging film according to claim 1, characterized in that: The thickness of the outer substrate layer is 30-45 μm, the thickness of the barrier layer is 20-35 μm, and the thickness of the inner substrate layer is 30-45 μm.

9. The method for preparing a recyclable high barrier packaging film according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1, respectively mixing the raw materials of the outer substrate layer, the barrier layer and the inner substrate layer in parts by weight, and respectively adding them into a twin-screw extruder for melt plasticization; Step 2, the melted and plasticized raw materials of the outer substrate layer, the barrier layer and the inner substrate layer are respectively extruded from the corresponding twin-screw extruders to converge into a die head to form a three-layer composite structure, and then cooled by a cooling roller to form a film with a three-layer co-extruded structure; Step 3, preheating the obtained film, biaxially stretching it, and heat setting it; Step 4: The stretched film is corona treated or flame treated and then rolled up to obtain a recyclable high barrier packaging film.

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