Packaging film for liquid hot filling and method for its production

Abstract

This invention discloses a packaging film for hot-filling liquids, which is a co-extruded film comprising, from the outside to the inside, a puncture-resistant outer layer, a polyethylene composite layer, a first connecting layer, a barrier core layer, a second connecting layer, and a heat-sealing layer stacked sequentially. Both the puncture-resistant outer layer and the heat-sealing layer comprise puncture-resistant metallocene polyethylene, high-strength metallocene polyethylene, and low-density polyethylene. The barrier core layer comprises at least one barrier unit layer, which includes homopolymer nylon and copolymer nylon. The polyethylene composite layer comprises at least one medium-density polyethylene layer. This packaging film combines strength, toughness, stiffness, and processability to prevent damage from external forces during transportation and stacking, ensuring a smooth appearance during filling.

Description

Technical Field

[0001] This invention relates to the field of hot liquid packaging film technology, specifically to a packaging film for hot liquid filling and its preparation method. Background Technology

[0002] Liquid hot-fill bags and films are a widely used type of packaging material, covering common liquids such as water, beverages, and juices, as well as viscous sauces, egg liquids, seasonings, and oils, solids, and powders. It is an efficient, convenient, and safe packaging form.

[0003] To develop products that meet the needs of the aforementioned industries and possess characteristics such as temperature resistance, rapid heat sealing, and high strength to cover more application scenarios, while also considering production costs, nylon was chosen as the barrier core layer. However, its barrier performance is inferior to EVOH, and its mechanical properties deteriorate after exposure to moisture. Therefore, it is necessary to optimize and improve the performance of nylon barrier packaging films. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a packaging film for liquid hot filling that combines strength, toughness, stiffness and processability to prevent damage from external forces during transportation and stacking, and to ensure a smooth appearance during filling.

[0005] To achieve the above-mentioned process effects, the technical solution of the present invention is as follows: a packaging film for liquid hot filling, which is a co-extruded film, comprising, from the outside to the inside, a puncture-resistant outer layer, a polyethylene composite layer, a first connecting layer, a barrier core layer, a second connecting layer and a heat-sealing layer stacked sequentially. Both the puncture-resistant outer layer and the heat-sealing layer comprise puncture-resistant metallocene polyethylene, high-strength metallocene polyethylene, and low-density polyethylene. The barrier core layer includes at least one barrier unit layer, and the barrier unit layer includes homopolymer nylon and copolymer nylon; The polyethylene composite layer includes at least one medium-density polyethylene layer.

[0006] The preferred technical solution is that, by weight, the puncture-resistant outer layer comprises 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene, and 16-22 parts of low-density polyethylene. The heat-sealing layer comprises 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene, 16-22 parts of low-density polyethylene, and 0.4-0.8 parts of an opening agent; The barrier unit layer comprises 45-55 parts of homopolymer nylon and 45-55 parts of copolymer nylon.

[0007] A preferred technical solution is that at least one of the barrier unit layers further includes modified montmorillonite, wherein the modified montmorillonite accounts for 0.5% to 3% of the total mass of the homopolymer nylon and copolymer nylon.

[0008] The preferred technical solution is that the modified montmorillonite is prepared by: subjecting montmorillonite to an amination intercalation treatment; The second method for preparing the modified montmorillonite involves first aminated intercalation of montmorillonite, then activating the aminated montmorillonite with isophorone diisocyanate, and finally capping it with caprolactam.

[0009] The preferred technical solution is that the homopolymer nylon is PA6 or PA66; the copolymer nylon is PA6 / 66.

[0010] A preferred technical solution is that the polyethylene composite layer includes layer A and layer B, with layer A being close to the puncture-resistant outer layer; By mass fractions, the composition of layer A includes 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene and 16-22 parts of low-density polyethylene; Alternatively, layer A may be a medium-density polyethylene layer; The B layer is a medium-density polyethylene layer.

[0011] A preferred technical solution is that the thickness ratio of the puncture-resistant outer layer, layer A, and layer B is 1:(0.82~1):(0.82~0.92), the thickness of the puncture-resistant outer layer accounts for 11%~13% of the total thickness of the packaging film; the thickness of the heat-sealing layer accounts for 31%~35% of the total thickness of the packaging film; and the total thickness of the packaging film is 70~150μm.

[0012] A preferred technical solution is that the barrier core layer comprises a first barrier unit outer layer, a barrier unit core layer, and a second barrier unit outer layer with a layer thickness ratio of (1~1.2):1:(1~1.2). The layer thickness of the barrier core layer accounts for 19%~22% of the total film thickness of the packaging film. Both the first and second barrier unit outer layers contain modified montmorillonite. In the barrier core layer composed of multiple barrier unit layers, the outer layer contains modified montmorillonite, which, while ensuring improved barrier performance, balances the haze and light transmittance of the packaging film, and improves the adhesion between the barrier core layer and the adjacent first and second connecting layers.

[0013] A preferred technical solution is that both the first connecting layer and the second connecting layer comprise linear low-density polyethylene and maleic anhydride-grafted linear low-density polyethylene in a mass ratio of (70~75):(25~30).

[0014] The second objective of this invention is to overcome the deficiencies in the prior art and provide a method for preparing a packaging film for liquid hot filling. The packaging film is a multilayer co-extruded film. The extrusion feed temperature of the puncture-resistant outer layer is 75~215℃, and the extrusion die temperature is 213~218℃. The highest extrusion feed temperature in the polyethylene composite layer is 75~215℃, and the extrusion die temperature is 213~218℃. The lowest extrusion feed temperature in the polyethylene composite layer is 75~205℃, and the extrusion die temperature is... The extrusion temperature of the first connecting layer is 75~225℃, and the extrusion die temperature is 223~228℃; the extrusion temperature of the barrier unit layer in the barrier core layer is 205~265℃, and the extrusion die temperature is 263~268℃; the extrusion temperature of the second connecting layer is 75~225℃, and the extrusion die temperature is 223~228℃; the extrusion temperature of the heat-sealing layer is 75~215℃, and the extrusion die temperature is 213~218℃.

[0015] The advantages and beneficial effects of this invention are as follows: The puncture-resistant outer layer combines strength, toughness, and processability to prevent damage from external forces during transportation and stacking. The high crystallinity of medium-density polyethylene results in higher modulus and stiffness, ensuring that the packaging film resists deformation during cooling, maintaining its flatness and wrinkle resistance; as well as maintaining the flat appearance of the packaging film and filling efficiency during filling. The core layer, a combination of homopolymer nylon and copolymer nylon, improves the flexibility and processability of the packaging film, and also enhances its puncture resistance, preventing the packaging film from cracking during drops or rubbing. The combined heat-sealing layer exhibits stable heat-sealing strength and good resistance to contamination during heat sealing. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of filling egg liquid with the packaging film for hot filling of liquid according to the present invention. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] model High-strength metallocene polyethylene (mLLDPE) is manufactured by ExxonMobil and has the trade name 1018MF. Puncture-resistant metallocene polyethylene (mLLDPE) is manufactured by ExxonMobil, with the trade name XP8784MK. Low-density polyethylene (LDPE) is produced by SABIC, with the trade name HP2025JN; Linear low-density polyethylene (LLDPE) is produced by Fujian United Petrochemical and its trade name is FL201XV; The adhesive was produced by Guangdong Hecheng Materials Technology Co., Ltd., with the trade name HS3-405H3. The copolymer nylon is produced by Huafeng Group, with the trade name HF2440B. The homopolymer nylon was produced by Nantong Weiming New Materials Co., Ltd., with the trade name J36TFE; The opening agent is produced by Shanghai Hongwei Plastics Co., Ltd., with the trade name TGN160.

[0019] Puncture-resistant outer layer The puncture-resistant outer layer comprises puncture-resistant metallocene polyethylene, high-strength metallocene polyethylene, and low-density polyethylene. The puncture-resistant metallocene polyethylene contains slip agents and anti-blocking agents, making the film surface smoother and facilitating smooth operation on high-speed packaging lines, thus ensuring low surface friction of the packaging film. The blend of puncture-resistant and high-strength metallocene polyethylene improves tensile strength, impact resistance, and puncture resistance, effectively preventing packaging damage during transportation and handling. Furthermore, it allows for a thinner film while maintaining the same level of protection, saving raw material costs and aligning with the trend towards lightweight and environmentally friendly packaging. The addition of low-density polyethylene improves the processing performance of the puncture-resistant outer layer, enhances film bubble stability, and reduces the risk of melt fracture.

[0020] Polyethylene composite layer Combination of polyethylene composite layers: Layer A consists of puncture-resistant metallocene polyethylene, high-strength metallocene polyethylene, and low-density polyethylene; Layer B is a medium-density polyethylene layer.

[0021] Combination 2 of polyethylene composite layers: Both layer A and layer B are medium-density polyethylene layers.

[0022] The B layer, made of medium-density polyethylene, improves the rigidity and stiffness of the packaging film, making it less prone to collapse and suitable for packaging liquid materials while maintaining its shape.

[0023] Barrier Core The barrier core layer includes at least one barrier unit layer, which includes homopolymer nylon and copolymer nylon.

[0024] Among them, homopolymer nylon is PA6 or PA66. PA6 has a regular molecular chain and high crystallinity, so it has better oxygen barrier properties and high stiffness, but slightly less flexibility. Both PA6 and PA66 are extremely hygroscopic, with PA6 having a saturated water absorption rate of 9% to 10% and PA66 having a saturated water absorption rate of 3% to 4%. The core advantages of PA66 are its strength and heat resistance. Its mechanical strength, rigidity, wear resistance, and creep resistance are all superior to PA6, but it is more expensive, more difficult to process, and relatively brittle.

[0025] Common copolymer nylons include PA6 / 66, PA6 / 12, PA6 / 9, PA12 / 66, and PA66 / 610. Among them, PA6 / 66 is the most basic copolymer nylon, with the core principle of "lowering the melting point and improving transparency." By introducing PA66 segments into PA6, the melting point is lowered, the processing window is wider, and the good mechanical properties of PA6 are retained, while improving the dimensional stability and toughness of PA6. At the same time, copolymerization disrupts the regularity of the molecular chain, reduces crystallinity, and significantly improves its transparency.

[0026] The barrier core layer is a blend of homopolymer nylon and copolymer nylon. Homopolymer nylon serves as the skeleton to ensure the barrier effect, while copolymer nylon is used to improve toughness, puncture resistance, and processing stability.

[0027] At least one barrier unit layer also includes modified montmorillonite. The addition of modified montmorillonite can reduce the water absorption of PA6 or PA66 and improve the elastic modulus, yield strength and barrier properties, but the elongation at break will decrease.

[0028] Furthermore, there are two methods for preparing modified montmorillonite: Method 1: Amide intercalation treatment of montmorillonite; Method 2: Amide intercalation of montmorillonite, followed by activation of the amide montmorillonite with isophorone diisocyanate, and then end-capping with caprolactam.

[0029] Method 1 for preparing modified montmorillonite: Aminoation of montmorillonite. Take 25g of polyetheramine (weight average molecular weight 2000), heat to 55℃ to reduce its viscosity, then add 5g of γ-methacryloyloxypropyltrimethoxysilane (KH570) dropwise and mix. Heat to 75℃ and react for 4h to obtain a mixture containing macromolecular aminosilane. Disperse 10g of montmorillonite evenly in a mixed solution of 100g ethanol and 20g deionized water. Then add the above-obtained mixture containing macromolecular aminosilane dropwise. Heat the reaction solution to 78℃ and react for 5h. Adjust the pH of the reaction solution to 3-4 with acetic acid and continue to keep it at the temperature for 3h. After the reaction is completed, wash, dry, grind and sieve to obtain the product.

[0030] Method 2 for preparing modified montmorillonite: The above-mentioned aminated montmorillonite is activated by taking aminated montmorillonite and isophorone diisocyanate in a mass ratio of 1:10. First, the aminated montmorillonite is impregnated with anhydrous toluene, and then isophorone diisocyanate and stannous octoate catalyst are added. The amount of stannous octoate catalyst added is 0.08% of the total mass of the reactants. The temperature is raised to 55℃ and reacted for 8 hours. Then, caprolactam with a molar ratio of 1.2:1 to isophorone diisocyanate is added, and the temperature is raised to 85℃ and reacted for 12 hours. After the reaction is completed, anhydrous formaldehyde is added for washing, centrifugation and drying, and the powder is prepared for later use.

[0031] Modification Principle: A short-chain olefin silane KH570 and polyetheramine are combined via nucleophilic addition to form a macromolecular aminosilane. Part of this macromolecular aminosilane is then used for surface grafting onto montmorillonite, while another part is converted to ammonium ions after proton acidification of the amino group. This leads to cationic intercalation modification of montmorillonite, resulting in aminated montmorillonite with interlayer anchoring polymer chains. Further activation with isophorone diisocyanate expands the interlayer spacing of montmorillonite and facilitates caprolactam grafting. Expanding the interlayer spacing improves compatibility with nylon, thereby promoting the insertion of nylon molecular chains into the interlayer. Caprolactam-grafted montmorillonite further enhances its compatibility with nylon. The amino group has high reactivity; by selecting isophorone diisocyanate with two isocyanate groups (NCO) exhibiting different reactivity, the reaction activity can be controlled, allowing for the precise acquisition of the desired graft.

[0032] Example 1

[0033] The packaging film for liquid hot filling is a co-extruded film, which includes, from the outside to the inside, a puncture-resistant outer layer, a polyethylene composite layer, a first connecting layer, a barrier core layer, a second connecting layer, and a heat-sealing layer stacked sequentially. The polyethylene composite layer includes layer A and layer B. The barrier core layer consists of three barrier unit layers, namely the outer layer of the first barrier unit, the core layer of the barrier unit, and the outer layer of the second barrier unit.

[0034] By weight, the puncture-resistant outer layer consists of 40 parts of puncture-resistant metallocene polyethylene, 40 parts of high-strength metallocene polyethylene, and 20 parts of low-density polyethylene.

[0035] By mass fraction, layer A consists of 40 parts puncture-resistant metallocene polyethylene, 40 parts high-strength metallocene polyethylene, and 20 parts low-density polyethylene; layer B is a medium-density polyethylene layer.

[0036] The heat-sealing layer consists of 40 parts of puncture-resistant metallocene polyethylene, 40 parts of high-strength metallocene polyethylene, 19.5 parts of low-density polyethylene, and 0.5 parts of an opening agent.

[0037] The outer layers of both the first and second barrier units consist of 50 parts homopolymer nylon, 50 parts copolymer nylon, and 1.5 parts modified montmorillonite. The core layer of the barrier unit consists of 50 parts homopolymer nylon and 50 parts copolymer nylon. The homopolymer nylon is PA6, and the copolymer nylon is PA6 / 66. The modified montmorillonite is aminated and intercalated, then activated with isophorone diisocyanate, and finally capped with caprolactam.

[0038] Both the first and second connecting layers comprise linear low-density polyethylene and maleic anhydride-grafted linear low-density polyethylene in a mass ratio of 75:25.

[0039] The total thickness of the packaging film for liquid hot filling is 91 μm, of which the thickness of the puncture-resistant outer layer is 10.01 μm, the thickness of layer A in the polyethylene composite layer is 10.01 μm, the thickness of layer B in the polyethylene composite layer is 9.1 μm, the thickness of the first connecting layer is 7.28 μm, the thickness of the outer layer of the first barrier unit in the barrier core layer is 6.37 μm, the thickness of the core layer of the barrier unit is 5.46 μm, the thickness of the outer layer of the second barrier unit is 6.37 μm, the thickness of the second connecting layer is 7.28 μm, and the thickness of the heat-sealing layer is 29.12 μm.

[0040] The packaging film for liquid hot filling is a multi-layer co-extruded film, which is extruded through a die. The extrusion temperature in the co-extrusion equipment, in the order of feeding section, plasticizing section, homogenizing section, two-stage extrusion section, and die, is as follows: Puncture-resistant outer layer: 75℃-215℃-215℃-215℃-215℃-215℃; A layer: 75℃-215℃-215℃-215℃-215℃-215℃; Layer B: 75℃-185℃-195℃-205℃-205℃-205℃; First connecting layer: 75℃-225℃-225℃-225℃-225℃-225℃; 75℃-225℃-225℃-225℃-225℃-225℃; Barrier core layer: 205℃-265℃-265℃-265℃-265℃-265℃; Second connecting layer: 75℃-225℃-225℃-225℃-225℃-225℃; Heat seal layer: 75℃-215℃-215℃-215℃-215℃-215℃.

[0041] Example 2

[0042] Example 2 is based on Example 1, except that layer A in the polyethylene composite layer is a medium-density polyethylene layer, which is the same as layer B; all other layers remain unchanged, the preparation process parameters of layer A and layer B are the same, and other processes remain unchanged.

[0043] Example 3

[0044] Example 3 is based on Example 1, except that the outer layers of both the first and second barrier units consist of 50 parts homopolymer nylon, 50 parts copolymer nylon, and 3 parts modified montmorillonite, while the composition of the other layers remains unchanged. The process remains the same.

[0045] Example 4

[0046] Example 4 is based on Example 1, except that the outer layer of the first barrier unit consists of 50 parts homopolymer nylon, 50 parts copolymer nylon, and 1.5 parts modified montmorillonite, while the outer layer of the second barrier unit consists of 50 parts homopolymer nylon, 50 parts copolymer nylon, and 0.5 parts modified montmorillonite. The composition of the other layers remains unchanged. The process remains the same.

[0047] Example 5

[0048] Example 5 is based on Example 1, except that the barrier unit layers do not include modified montmorillonite. The composition of the other layers remains unchanged. The process remains the same.

[0049] Example 6

[0050] Example 6 is based on Example 1, except that the modified montmorillonite in the outer layers of the first and second barrier units undergoes only aminolation intercalation treatment, while other components remain unchanged, as do the compositions of the other layers. The process remains the same.

[0051] Comparative Example 1 Comparative Example 1 is based on Example 1, except that, by mass parts, the A layer of the polyethylene composite layer consists of 70 parts HDPE (F920A) and 30 parts LLDPE (1002XBU), while the other layers remain unchanged; the extrusion temperature of the A layer of the polyethylene composite layer in the co-extrusion equipment is as follows, in the order of feeding section, plasticizing section, homogenizing section, two-stage extrusion section, and die head: 80℃, 235℃, 235℃, 235℃, 235℃, 235℃; other processes remain unchanged.

[0052] Comparative Example 2 Comparative Example 2 is based on Example 1, except that, by mass parts, the composition of the puncture-resistant outer layer includes 80 parts of puncture-resistant metallocene polyethylene and 20 parts of low-density polyethylene, while the other layers remain unchanged; other processes remain unchanged.

[0053] Performance testing of packaging film samples in the examples and comparative examples: 1. Tensile strength and elongation at break: determined according to standard GB / T 1040.3-2006; 2. Haze and transparency: Measured according to standard GB / T 2410-1980; 3. Oxygen permeability: Measured according to standard GB / T1038-2000; 4. Puncture resistance: Tested according to standard GB / T 37841; puncture test was conducted using a 1mm needle at a speed of 60mm / min. 5. Stiffness: Take a sample 10cm long and 1cm wide. On a horizontal measuring platform, use a pressure block to press one end of the sample film firmly, while the other end extends freely. The extension length is fixed at 5cm. The extended part will naturally droop under its own weight. After the sample film has drooped and stabilized, measure the vertical distance of the lowest point of the film head relative to the horizontal reference plane. This distance is marked as the droop dimension L0. Stiffness = L0 / 5*100%. The smaller the value, the smaller the droop dimension, which means that the sample film can remain straighter under gravity and has better stiffness.

[0054] The performance test results of the examples and comparative examples are as follows:

[0055] Compared to Example 1, in Example 2, when both layer A and layer B are medium-density polyethylene layers, although the stiffness of the packaging film is improved, the toughness and puncture resistance are reduced.

[0056] Compared to Example 1, Example 3 shows that the content of modified montmorillonite in the outer layers of the first and second barrier units is increased, resulting in better dispersibility, improved barrier performance, and increased stiffness. However, the optical properties and toughness are reduced.

[0057] Compared to Example 1, Example 4 shows a difference in the content of modified montmorillonite in the outer layers of the first and second barrier units, resulting in smaller performance fluctuations and a positive impact on optical performance. However, experiments revealed that during the peeling test between the connecting layer and the barrier core layer, the side with a higher montmorillonite content exhibited stronger adhesion, forming a microscopic uneven structure and more polar groups at the interface, which is beneficial for the adhesion between the barrier core layer and the connecting layer.

[0058] Compared to Example 1, Example 6 introduces amino groups into the aminated intercalated montmorillonite, which can chemically interact with the terminal carboxyl or amide groups of nylon, forming chemical crosslinks between the montmorillonite sheets and the nylon molecular chains, resulting in superior mechanical properties and better toughness. The modified montmorillonite prepared by Method 2 has a larger interlayer spacing, which facilitates the tight entanglement of nylon molecular chains and polyetheramine long chains, thereby strengthening the interfacial bonding between the two. The grafted caprolactam improves the compatibility with nylon molecules, and the hydrogen bonding between the urethane bond and the amide group of nylon provides excellent mechanical properties.

[0059] Compared to Example 1, Comparative Example 1, composed of HDPE and LLDPE, showed improved moisture resistance, increased stiffness and tensile strength in the A layer of the packaging film, but decreased toughness, puncture resistance, optical haze and transparency.

[0060] Compared to Example 1, Comparative Example 2 has an increased content of puncture-resistant metallocene polyethylene, which improves performance but increases processing difficulty and extrusion pressure load.

[0061] The experiment also found that when the content of high-strength metallocene polyethylene in the puncture-resistant outer layer increased and replaced the puncture-resistant metallocene polyethylene, the stiffness of the packaging film decreased.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A packaging film for liquid hot filling, which is a co-extruded film, characterized in that, From the outside to the inside, it includes a puncture-resistant outer layer, a polyethylene composite layer, a first connecting layer, a barrier core layer, a second connecting layer, and a heat-sealing layer, stacked sequentially. Both the puncture-resistant outer layer and the heat-sealing layer comprise puncture-resistant metallocene polyethylene, high-strength metallocene polyethylene, and low-density polyethylene. The barrier core layer includes at least one barrier unit layer, and the barrier unit layer includes homopolymer nylon and copolymer nylon; The polyethylene composite layer includes at least one medium-density polyethylene layer.

2. The packaging film for liquid hot filling according to claim 1, characterized in that, By mass fraction, the puncture-resistant outer layer comprises 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene, and 16-22 parts of low-density polyethylene. The heat-sealing layer comprises 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene, 16-22 parts of low-density polyethylene, and 0.4-0.8 parts of an opening agent; The barrier unit layer comprises 45-55 parts of homopolymer nylon and 45-55 parts of copolymer nylon.

3. The packaging film for liquid hot filling according to claim 1 or 2, characterized in that, At least one of the barrier unit layers further includes modified montmorillonite, which accounts for 0.5% to 3% of the total mass of the homopolymer nylon and copolymer nylon.

4. The packaging film for liquid hot filling according to claim 3, characterized in that, The first method for preparing the modified montmorillonite is to subject the montmorillonite to an amination intercalation treatment. The second method for preparing the modified montmorillonite involves first aminated intercalation of montmorillonite, then activating the aminated montmorillonite with isophorone diisocyanate, and finally capping it with caprolactam.

5. The packaging film for liquid hot filling according to claim 3, characterized in that, The homopolymer nylon is PA6 or PA66; the copolymer nylon is PA6 / 66.

6. The packaging film for liquid hot filling according to claim 1, characterized in that, The polyethylene composite layer includes layer A and layer B, with layer A being close to the puncture-resistant outer layer; By mass fractions, the composition of layer A includes 36-42 parts of puncture-resistant metallocene polyethylene, 36-42 parts of high-strength metallocene polyethylene and 16-22 parts of low-density polyethylene; Alternatively, layer A may be a medium-density polyethylene layer; The B layer is a medium-density polyethylene layer.

7. The packaging film for liquid hot filling according to claim 6, characterized in that, The thickness ratio of the puncture-resistant outer layer, layer A, and layer B is 1:(0.82~1):(0.82~0.92), the thickness of the puncture-resistant outer layer accounts for 11%~13% of the total thickness of the packaging film; the thickness of the heat-sealing layer accounts for 31%~35% of the total thickness of the packaging film; and the total thickness of the packaging film is 70~150μm.

8. The packaging film for liquid hot filling according to claim 3, characterized in that, The barrier core layer comprises a first barrier unit outer layer, a barrier unit core layer, and a second barrier unit outer layer with a layer thickness ratio of (1~1.2):1:(1~1.2). The layer thickness of the barrier core layer accounts for 19%~22% of the total film thickness of the packaging film. Both the first barrier unit outer layer and the second barrier unit outer layer contain modified montmorillonite.

9. The packaging film for liquid hot filling according to claim 1, characterized in that, Both the first connecting layer and the second connecting layer comprise linear low-density polyethylene and maleic anhydride-grafted linear low-density polyethylene in a mass ratio of (70~75):(25~30).

10. A method for preparing a packaging film for liquid hot filling, characterized in that, The packaging film is a multilayer co-extruded film. The extrusion feed temperature of the puncture-resistant outer layer is 75~215℃, and the extrusion die temperature is 213~218℃. The highest extrusion feed temperature in the polyethylene composite layer is 75~215℃, and the extrusion die temperature is 213~218℃. The lowest extrusion feed temperature in the polyethylene composite layer is 75~205℃, and the extrusion die temperature is 203~208℃. The extrusion feed temperature of the first connecting layer is 75~225℃, and the extrusion die temperature is 223~228℃. The extrusion feed temperature of the barrier unit layer in the barrier core layer is 205~265℃, and the extrusion die temperature is 263~268℃. The extrusion feed temperature of the second connecting layer is 75~225℃, and the extrusion die temperature is 223~228℃. The extrusion feed temperature of the heat-sealing layer is 75~215℃, and the extrusion die temperature is 213~218℃.

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