Food packaging recycled film geomembrane and method for preparing the same

Abstract

The application provides a food packaging recycled film regenerated geomembrane and a preparation method thereof. The food packaging recycled film regenerated geomembrane comprises an outermost layer, an intermediate layer and an innermost layer arranged in sequence. The outermost layer and the innermost layer are symmetrically distributed with the intermediate layer as an axis. The outermost layer and the innermost layer comprise, by weight percentage, 85.0-95.0% of high-density polyethylene, 1.0-10.0% of medium-density polyethylene, 1.0-5.0% of a first compatilizer and 0.5-2.0% of silane modified montmorillonite. The intermediate layer comprises 75.0-93.0% of food packaging recycled film, 5.0-20.0% of a second compatilizer and 2.0-8.0% of ethylene-vinyl acetate copolymer. On the basis of the silane modified montmorillonite, the PA and PET in the food packaging recycled film can improve the mechanical properties such as stiffness and strength of the geomembrane. Thus, the geomembrane has good performance in all aspects and can be used as a replacement product of the virgin geomembrane.

Description

Technical Field

[0001] This invention relates to the field of multilayer structure technology, and more particularly to a thin film, and even more particularly to a recycled geomembrane for food packaging and its preparation method. Background Technology

[0002] In daily life, the close relationship between food packaging and food is widely recognized. Beautifully designed and convenient food packaging is ubiquitous in stores, supermarkets, and homes. Like clothing worn close to the skin, food packaging is the final step in the modern food industry. It not only protects and promotes food but also facilitates its storage, transportation, and sale. To a large extent, food packaging has become an integral part of food, directly or indirectly influencing its quality.

[0003] Currently, food packaging films are typically composed of multi-layered composite materials, commonly PP / PA / PET / PE. Due to the significant differences in polarity and flow properties among these materials, food packaging films, even after recycling and cleaning, cannot be utilized at a high value and are usually only used as pallet filler. This represents a substantial waste of resources and contradicts current initiatives advocating for the recycling of waste film.

[0004] Therefore, how to maximize the value of recycled food packaging film is a problem that the industry urgently needs to solve. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a recycled geomembrane made from food packaging film and its preparation method. This invention transforms recycled food packaging film into a geomembrane, turning waste into treasure and maximizing the value of the recycled food packaging film. Furthermore, the resulting geomembrane exhibits superior performance in various aspects and can serve as a replacement for the original, unprocessed geomembrane.

[0006] To achieve the above objectives, a first aspect of the present invention provides a recycled geomembrane for food packaging film, comprising an outermost layer, a middle layer, and an innermost layer arranged sequentially. The outermost layer and the innermost layer are symmetrically distributed about the middle layer as an axis. By weight percentage, the outermost layer and the innermost layer comprise 85.0–95.0% high-density polyethylene, 1.0–10.0% medium-density polyethylene, 1.0–5.0% a first compatibilizer, and 0.5–2.0% silane-modified montmorillonite. The middle layer comprises 75.0–93.0% food packaging film, 5.0–20.0% a second compatibilizer, and 2.0–8.0% ethylene-vinyl acetate copolymer.

[0007] In the recycled geomembrane of the food packaging film of this invention, the outermost and innermost layers are symmetrically distributed with the middle layer as the axis, meaning the entire geomembrane has a symmetrical structure. When subjected to external forces, the layers in the geomembrane can maintain uniform stress distribution, preventing deformation or even tearing due to uneven stress. Simultaneously, the outermost and innermost layers, based on high-density polyethylene, incorporate a small amount of medium-density polyethylene, a first compatibilizer, and silane-modified montmorillonite. The silane-modified montmorillonite improves the mechanical properties of the geomembrane, while the first compatibilizer ensures uniform dispersion of the silane-modified montmorillonite within the high-density polyethylene, generating good interfacial interactions and enabling better composite bonding with the food packaging film in the middle layer. The middle layer, based on the food packaging film, adds a second compatibilizer and ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer adjusts the polarity of polyethylene, and the addition of the second compatibilizer further enhances the compatibility of PA, PET, and PP in the food packaging film with polyethylene, thereby enabling blown film processing. Based on silane-modified montmorillonite, combining it with PA, PET, and other materials from recycled food packaging films can improve the stiffness, strength, and other mechanical properties of geomembranes. This results in geomembranes with superior overall performance, making them a suitable replacement for untreated geomembranes.

[0008] As a technical solution of the present invention, the thickness ratio of the outermost layer, the middle layer and the innermost layer is 1~2:3~8:1~2.

[0009] As one technical solution of the present invention, the density of the high-density polyethylene is 0.956 g / cm³. 3 The melt flow index is ≤0.04g / 10min.

[0010] As one technical solution of the present invention, the density of the medium-density polyethylene is 0.935–0.950 g / cm³. 3 The melt flow index is <0.5g / 10min.

[0011] As a technical solution of the present invention, the first compatibilizer includes maleic anhydride-grafted polyethylene and / or maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer.

[0012] As a technical solution of the present invention, the silane-modified montmorillonite is montmorillonite modified by hexadecyltributylphosphonium bromide intercalation and modified by hexadecyltrimethoxysilane.

[0013] As one technical solution of the present invention, the second compatibilizer includes an ethylene-butyl acrylate-glycidyl methacrylate terpolymer and a maleic anhydride-grafted polyolefin compound.

[0014] As one technical solution of the present invention, the maleic anhydride-grafted polyolefin compounds include maleic anhydride-grafted polyolefin elastomers, maleic anhydride-grafted polyethylene, and ethylene propylene diene monomer (EPDM) rubber grafted with methyl methacrylate.

[0015] As one technical solution of the present invention, the content of vinyl acetate units in the ethylene-vinyl acetate copolymer is 10-20 wt.%.

[0016] The second aspect of the present invention provides a method for preparing recycled geomembrane from food packaging recycled film, wherein the raw materials of the outermost layer, the middle layer and the innermost layer are mixed evenly according to the formula ratio, and respectively fed to the extruder of a three-layer co-extrusion blown film unit, and then successively subjected to extrusion, water cooling, traction, heating and softening at 120-130°C, secondary blowing, and winding and shaping.

[0017] The preparation method of the present invention utilizes recycled food packaging film to produce geomembrane, turning waste into treasure and maximizing the value of recycled food packaging film. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the three-layer structure of the food packaging recycling film and recycled geomembrane of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further illustrated below through specific embodiments, but these do not constitute any limitation on the present invention.

[0020] For ease of description, some substances in this invention are abbreviated, such as polyethylene (PE), polyamide (PA), polyethylene terephthalate (PET), polypropylene (PP), high-density polyethylene (HDPE), medium-density polyethylene (MDPE), maleic anhydride-grafted polyethylene (PE-g-MAH), maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer (SEBS-g-MAH), ethylene-butyl acrylate-glycidyl methacrylate terpolymer (PTW), maleic anhydride-grafted polyolefin elastomer (POE-g-MAH), ethylene propylene diene monomer (EPDM-g-MMA) grafted with methyl methacrylate (EMA), ethylene-vinyl acetate copolymer (EVA), and vinyl acetate unit (VAc).

[0021] like Figure 1As shown, the recycled geomembrane for food packaging of the present invention comprises an outermost layer 1, a middle layer 2, and an innermost layer 3 arranged sequentially. The outermost layer 1 and the innermost layer 3 are symmetrically distributed about the middle layer 2. The thickness ratio of the outermost layer 1, the middle layer 2, and the innermost layer 3 is 1-2:3-8:1-2, preferably 1:3:1 or 1:4:1. Specifically, the thickness ratio of the three layers can be, but is not limited to, 1:3:1, 1:4:1, 1:5:1, 1:6:1, 1:7:1, 1:8:1, 2:3:2, 2:4:2, 2:5:2, and 2:7:2.

[0022] By weight percentage, the outermost layer 1 and the innermost layer 3 comprise 85.0–95.0% high-density polyethylene, 1.0–10.0% medium-density polyethylene, 1.0–5.0% first compatibilizer, and 0.5–2.0% silane-modified montmorillonite.

[0023] The content of high-density polyethylene (HDPE) can be, but is not limited to, 85.0%, 85.5%, 86.0%, 86.5%, 87.0%, 87.5%, 88.0%, 88.5%, 89.0%, 89.5%, 90.0%, 90.5%, 91.0%, 91.5%, 92.0%, 92.5%, 93.0%, 93.5%, 94.0%, 94.5%, and 95.0%. The density of HDPE is 0.956 g / cm³. 3 The melt flow index is ≤0.04 g / 10 min. The content of medium-density polyethylene (MDPE) can be, but is not limited to, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, or 10.0%. The density of MPE is 0.935–0.950 g / cm³. 3 The melt flow index is <0.5g / 10min.

[0024] The content of the first compatibilizer may be, but is not limited to, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5.0%. The first compatibilizer includes maleic anhydride-grafted polyethylene and / or maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer. Maleic anhydride-grafted polyethylene can improve the tensile strength of the outermost and innermost polyethylene layers and has good thermal stability, while maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer can significantly increase the elongation at break of the outermost and innermost polyethylene layers. The synergistic effect of adding both compatibilizers helps to obtain outermost and innermost layers with good overall performance; although the strength decreases slightly, the elongation at break is significantly improved.

[0025] The content of silane-modified montmorillonite can be, but is not limited to, 0.5%, 1.0%, 1.5%, or 2.0%. Silane-modified montmorillonite is montmorillonite modified by hexadecyltributylphosphonium bromide intercalation and modified with hexadecyltrimethoxysilane.

[0026] The preparation steps of silane-modified montmorillonite may include: dissolving hexadecyltributylphosphonium bromide intercalating agent in an acetone / water mixture and magnetically stirring the mixture at room temperature; simultaneously dispersing montmorillonite in a three-necked flask containing an ethanol / water mixture; heating and stirring for a certain time; adding the prepared hexadecyltributylphosphonium bromide solution to the montmorillonite suspension; heating and stirring for a certain time; filtering; and washing the filter cake several times alternately with ethanol and water until bromide ions are undetectable by silver nitrate; drying and grinding to obtain organo-intercalated montmorillonite (HMMT). Alternatively, adjusting the pH of the hexadecyltrimethoxysilane and ethanol / water mixture to 4-5 with acetic acid and stirring at room temperature to prepare a pre-hydrolyzed silane solution; dispersing HMMT in an ethanol / water mixture; adding the pre-hydrolyzed silane solution to the HMMT solution; heating and stirring for a certain time; and treating the suspension in the same way as HMMT, followed by drying and grinding to obtain silane-modified montmorillonite (FMMT).

[0027] The intermediate layer 2 comprises 75.0–93.0% of recycled food packaging film, 5.0–20.0% of a second compatibilizer, and 2.0–8.0% of ethylene-vinyl acetate copolymer.

[0028] The content of recycled food packaging film can be, but is not limited to, 75.0%, 77.0%, 79.0%, 80.0%, 82.0%, 84.0%, 86.0%, 88.0%, 90.0%, 91.0%, and 93.0%. The recycled food packaging film can be conventional recycled food packaging film, or a composite of PA, PET, PP, and PE.

[0029] The content of the second compatibilizer may be, but is not limited to, 5.0%, 7.0%, 9.0%, 10.0%, 12.0%, 14.0%, 16.0%, 18.0%, or 20.0%. The second compatibilizer includes an ethylene-butyl acrylate-glycidyl methacrylate terpolymer and maleic anhydride-grafted polyolefin compounds. Maleic anhydride-grafted polyolefin compounds include maleic anhydride-grafted polyolefin elastomers, maleic anhydride-grafted polyethylene, and ethylene propylene diene monomer (EPDM) rubber-grafted methyl methacrylate. The content of maleic anhydride-grafted polyolefin elastomers, maleic anhydride-grafted polyethylene, and EPDM rubber-grafted methyl methacrylate may be 4–6%, 4–6%, and 1–5%, respectively. The addition of the ethylene-butyl acrylate-glycidyl methacrylate terpolymer increases interfacial interactions and promotes the refinement of dispersed phase particles, thereby improving the system compatibility. Maleic anhydride-grafted polyolefin elastomers and maleic anhydride-grafted polyethylenes are beneficial for improving the heat resistance, tensile strength, and impact strength of the system. EPDM-grafted methyl methacrylate (MDMA) can improve the impact performance of food packaging recycling films and polyethylene composite films. EPDM-grafted MDMA has good adhesion to polypropylene and high-density polyethylene in food packaging recycling films, increasing the number of bonded molecules between the PP and HDPE crystal phases, forming a continuous two-phase structure. This improves interphase adhesion, refines crystal structure, and thus enhances impact performance.

[0030] The content of the ethylene-vinyl acetate copolymer can be, but is not limited to, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, and 8.0%. The content of vinyl acetate units in the ethylene-vinyl acetate copolymer is 10–20 wt.%, and can be, but is not limited to, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, and 20 wt.%.

[0031] The recycled geomembrane made from the food packaging film of this invention can be prepared by the following method: the raw materials for the outermost, middle, and innermost layers are mixed evenly according to the formula ratio, and then fed separately to the extruder of a three-layer co-extrusion blown film unit. The mixture is then sequentially extruded, cooled with water, drawn, softened by heating at 120-130°C, undergoes secondary inflation, and is wound and shaped. The material for the middle layer needs to be blended using plasticizing equipment with good blending effect, such as a three-screw extruder or a stretch rheological extruder. The secondary inflation ratio can be 5-9, preferably up to 7. The recycled food packaging film used for the middle layer is not a whole piece of film, but rather the recycled food packaging film is crushed and ground before being used as raw material.

[0032] The following detailed description of the food packaging recycling film and recycled geomembrane of the present invention will be provided through specific embodiments, but the scope of the present invention is not limited thereto.

[0033] Example 1

[0034] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0035] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0036] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0037] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0038] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0039] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0040] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0041] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0042] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0043] The parameters for various materials are as follows:

[0044] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0045] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0046] The preparation of silane-modified montmorillonite can be as follows: 2.28 g of hexadecyltributylphosphonium bromide intercalating agent is dissolved in 50 mL of acetone / water (volume ratio 1 / 1), and the mixture is magnetically stirred for 1 h at room temperature. Simultaneously, 5 g of MMT is dispersed in a three-necked flask containing 100 mL of ethanol / water (volume ratio 1 / 1) mixed solvent. After stirring at 70 °C for 0.5 h, the prepared hexadecyltributylphosphonium bromide solution is added to the montmorillonite suspension. After stirring at 70 °C for 8 h, the mixture is filtered, and the filter cake is washed several times alternately with ethanol and water until bromide ions are no longer detectable with silver nitrate. The product is dried at 60 °C for 24 h and then ground to obtain organo-intercalated montmorillonite (HMMT). A pre-hydrolyzed silane solution is prepared by adjusting the pH of a solution of 5 mL of hexadecyltrimethoxysilane and 50 mL of ethanol / water (volume ratio 9 / 1) to 4–5 with acetic acid and stirring at room temperature for 1 h. 5 g of HMMT was dispersed in 100 mL of an ethanol / water mixture. A pre-hydrolyzed silane solution was added to the HMMT solution, and the mixture was heated to 45 °C and stirred for 24 h. The suspension was treated in the same way as the HMMT solution, and after drying and grinding, silane-modified montmorillonite was obtained.

[0047] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0048] Example 2

[0049] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 42 μm. The performance parameters of each layer are as follows.

[0050] Outermost layer: 7μm thick, comprising 86.0% high-density polyethylene, 8.0% medium-density polyethylene,

[0051] 2.5% maleic anhydride-grafted polyethylene, 1.5% maleic anhydride-grafted styrene-ethylene-

[0052] Butene-styrene block copolymer and 2.0% silane-modified montmorillonite.

[0053] Intermediate layer: 28μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0054] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0055] Innermost layer: 7μm thick, comprising 86.0% high-density polyethylene and 8.0% medium-density polyethylene.

[0056] 2.5% maleic anhydride-grafted polyethylene, 1.5% maleic anhydride-grafted styrene-ethylene-

[0057] Butene-styrene block copolymer and 2.0% silane-modified montmorillonite.

[0058] The parameters for various materials are as follows:

[0059] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0060] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0061] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0062] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0063] Example 3

[0064] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 41 μm. The performance parameters of each layer are as follows.

[0065] Outermost layer: 8μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0066] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0067] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0068] Intermediate layer: 25μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0069] The composition consists of PE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 20 wt.%.

[0070] Innermost layer: 8μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0071] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0072] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0073] The parameters for various materials are as follows:

[0074] The density of high-density polyethylene is 0.956 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0075] The density of medium-density polyethylene is 0.950 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0076] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0077] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0078] Example 4

[0079] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0080] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0081] 4.0% maleic anhydride-grafted polyethylene and 1.5% silane-modified montmorillonite.

[0082] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0083] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0084] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0085] 4.0% maleic anhydride-grafted polyethylene and 1.5% silane-modified montmorillonite.

[0086] The parameters for various materials are as follows:

[0087] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0088] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0089] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0090] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0091] Example 5

[0092] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0093] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0094] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0095] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0096] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 8% POE-g-MAH,

[0097] 5% EPDM-MMA and 5.0% ethylene-vinyl acetate copolymer, wherein the ethylene-vinyl acetate copolymer contains 15 wt.% vinyl acetate units.

[0098] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0099] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0100] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0101] The parameters for various materials are as follows:

[0102] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0103] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0104] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0105] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0106] Example 6

[0107] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0108] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0109] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0110] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0111] Intermediate layer: 21 μm thick, comprising 82.0% food packaging recycled film, 13% EPDM-MMA and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0112] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0113] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0114] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0115] The parameters for various materials are as follows:

[0116] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0117] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0118] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0119] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0120] Comparative Example 1

[0121] The thickness of the food packaging recycled film is 35 μm. The film consists of 82.0% food packaging recycled film, 5.0% PTW, 5% POE-g-MAH, 3% EPDM-MMA and 5.0% ethylene-vinyl acetate copolymer, and the content of vinyl acetate units in the ethylene-vinyl acetate copolymer is 15 wt.%.

[0122] The raw materials are mixed evenly according to the formula, sent to the extruder, and then successively extruded, cooled with water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0123] Comparative Example 2

[0124] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0125] Outermost layer: 7 μm thick, comprising 93.5% high-density polyethylene, 5.0% medium-density polyethylene, and 1.5% silane-modified montmorillonite.

[0126] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0127] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0128] Innermost layer: 7 μm thick, comprising 93.5% high-density polyethylene, 5.0% medium-density polyethylene, and 1.5% silane-modified montmorillonite.

[0129] The parameters for various materials are as follows:

[0130] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0131] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0132] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0133] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0134] Comparative Example 3

[0135] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0136] Outermost layer: 7μm thick, comprising 91.5% high-density polyethylene and 5.0% medium-density polyethylene.

[0137] 1.5% maleic anhydride-grafted polyethylene and 2.0% maleic anhydride-grafted styrene-ethylene-

[0138] Butene-styrene block copolymer.

[0139] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0140] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0141] Innermost layer: 7μm thick, comprising 91.5% high-density polyethylene and 5.0% medium-density polyethylene.

[0142] 1.5% maleic anhydride-grafted polyethylene and 2.0% maleic anhydride-grafted styrene-ethylene-

[0143] Butene-styrene block copolymer.

[0144] The parameters for various materials are as follows:

[0145] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0146] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0147] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0148] Comparative Example 4

[0149] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0150] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0151] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0152] Butene-styrene block copolymer and 1.5% montmorillonite.

[0153] Intermediate layer: 21μm thick, comprising 82.0% food packaging recycled film, 5.0% PTW, and 5%...

[0154] The composition consists of POE-g-MAH, 3% EPDM-MMA, and 5.0% ethylene-vinyl acetate copolymer, with the vinyl acetate unit content in the ethylene-vinyl acetate copolymer being 15 wt.%.

[0155] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0156] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0157] Butene-styrene block copolymer and 1.5% montmorillonite.

[0158] The parameters for various materials are as follows:

[0159] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0160] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0161] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0162] Comparative Example 5

[0163] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0164] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0165] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0166] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0167] Intermediate layer: 21 μm thick, comprising 92.0% food packaging recycled film and 8.0% ethylene-vinyl acetate copolymer, wherein the ethylene-vinyl acetate copolymer contains vinyl acetate units of [missing information].

[0168] 15 wt.%.

[0169] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0170] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0171] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0172] The parameters for various materials are as follows:

[0173] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0174] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0175] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0176] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0177] Comparative Example 6

[0178] The recycled geomembrane from food packaging film consists of an outermost layer, a middle layer, and an innermost layer. The total thickness of the recycled geomembrane is 35 μm. The performance parameters of each layer are as follows.

[0179] Outermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0180] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0181] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0182] Intermediate layer: 21μm thick, comprising 87.0% recycled food packaging film, 5.0% PTW, and 5%...

[0183] POE-g-MAH and 3% EPDM-MMA.

[0184] Innermost layer: 7μm thick, comprising 90.0% high-density polyethylene and 5.0% medium-density polyethylene.

[0185] 1.5% maleic anhydride-grafted polyethylene, 2.0% maleic anhydride-grafted styrene-ethylene-

[0186] Butene-styrene block copolymer and 1.5% silane-modified montmorillonite.

[0187] The parameters for various materials are as follows:

[0188] The density of high-density polyethylene is 0.958 g / cm³. 3 The melt flow index is 0.03 g / 10 min;

[0189] The density of medium-density polyethylene is 0.940 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0190] The preparation of silane-modified montmorillonite can be the same as in Example 1.

[0191] The raw materials corresponding to the three layers are mixed evenly according to the formula and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 125±3℃, blown in a second time, and wound up and shaped.

[0192] The recycled geomembranes of food packaging recycled films prepared in Examples 1-6 and Comparative Examples 1-6 were subjected to drop impact tests, tensile tests, and tear tests, respectively. The test methods are as follows.

[0193] Drop impact performance: The drop impact strength was tested according to the standard GB / T 9639-1988 "Test method for impact resistance of plastic films and sheets - free-falling dart method" and the corresponding drop impact strength was obtained.

[0194] Tensile property test: The tensile strength and elongation at break were obtained by testing according to the standard GB13022-1991 "Test Method for Tensile Properties of Plastic Films".

[0195] Tear resistance: The tear resistance was tested according to the standard GB / T16578.1-2008 Determination of tear resistance of plastic films and sheets, and the corresponding tear strength value was obtained.

[0196] Table 1. Performance of recycled geomembranes from food packaging recycled films in Examples 1-6 and Comparative Examples 1-6

[0197]

[0198]

[0199] As shown in Table 1, the recycled geomembranes from food packaging film in Examples 1-6 exhibit better drop impact strength, tensile strength, elongation at break, and tear strength than those in Comparative Examples 1-6. This indicates that the mechanical properties of the recycled geomembranes from food packaging film in Examples 1-6 are superior to those in Comparative Examples 1-6. This is mainly due to the addition of small amounts of medium-density polyethylene, a first compatibilizer, and silane-modified montmorillonite to the outermost and innermost layers based on high-density polyethylene. Silane-modified montmorillonite improves the mechanical properties of the geomembrane, while the first compatibilizer ensures uniform dispersion of the silane-modified montmorillonite within the high-density polyethylene, resulting in good interfacial interaction and better composite with the intermediate food packaging film. The intermediate layer adds a second compatibilizer and ethylene-vinyl acetate copolymer to the food packaging film. The ethylene-vinyl acetate copolymer adjusts the polarity of polyethylene, and the addition of the second compatibilizer allows the PA, PET, and PP in the food packaging film to achieve good compatibility with polyethylene, thus enabling blown film processing. Based on silane-modified montmorillonite, combining it with PA, PET, and other materials from recycled food packaging films can improve the stiffness, strength, and other mechanical properties of geomembranes.

[0200] Comparing Examples 1 and 4, it can be seen that when the first compatibilizer is a blend of maleic anhydride-grafted polyethylene and / or maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer, the resulting recycled geomembrane for food packaging has better performance.

[0201] Comparing Examples 1 and 5-6, it can be seen that when the second compatibilizer is a blend of ethylene-butyl acrylate-glycidyl methacrylate terpolymer and maleic anhydride-grafted polyolefin compound, the resulting recycled geomembrane for food packaging is of better performance.

[0202] The above description of the disclosed embodiments is intended to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles disclosed herein.

Claims

1. A recycled geomembrane for food packaging film, comprising an outermost layer, a middle layer, and an innermost layer arranged sequentially, characterized in that, The outermost and innermost layers are symmetrically distributed about the intermediate layer. The outermost and innermost layers have the same formulation and thickness. By weight percentage, the outermost or innermost layer comprises 85.0-95.0% high-density polyethylene, 1.0-10.0% medium-density polyethylene, 1.0-5.0% first compatibilizer, and 0.5-2.0% silane-modified montmorillonite. The intermediate layer comprises 75.0-93.0% food packaging recycled film, 5.0-20.0% second compatibilizer, and 2.0-8.0% ethylene-vinyl acetate copolymer. The first compatibilizer comprises maleic anhydride-grafted polyethylene and maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer. The second compatibilizer comprises ethylene-butyl acrylate-glycidyl methacrylate terpolymer, maleic anhydride-grafted polyolefin elastomer, maleic anhydride-grafted polyethylene, and ethylene propylene diene monomer (EPDM) rubber-grafted methyl methacrylate.

2. The recycled geomembrane for food packaging film as described in claim 1, characterized in that, The thickness ratio of the outermost layer, the middle layer, and the innermost layer is 1~2:3~8:1~2.

3. The recycled geomembrane for food packaging film as described in claim 1, characterized in that, The density of the high-density polyethylene is 0.956 g / cm³. 3 The melt flow index is ≤0.04g / 10min.

4. The recycled geomembrane for food packaging film as described in claim 1, characterized in that, The density of the medium-density polyethylene is 0.935~0.950 g / cm³. 3 The melt flow index is <0.5g / 10min.

5. The recycled geomembrane for food packaging film as described in claim 1, characterized in that, The silane-modified montmorillonite is montmorillonite modified by hexadecyltributylphosphonium bromide intercalation and modified by hexadecyltrimethoxysilane.

6. The recycled geomembrane for food packaging film as described in claim 1, characterized in that, The vinyl acetate unit content in the ethylene-vinyl acetate copolymer is 10~20 wt.

7. The method for preparing recycled geomembrane from food packaging recycled film according to any one of claims 1 to 6, characterized in that, include: The raw materials of the outermost layer, the middle layer and the innermost layer are mixed evenly according to the formula ratio and sent to the extruder of the three-layer co-extrusion blown film unit. Then, they are sequentially extruded, cooled by water, drawn, heated and softened at 120~130℃, blown in a second time, and wound up and shaped.

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