Polyethylene composite film suitable for automatic hot filling and preparation method thereof

Abstract

The present application relates to a polyethylene composite film suitable for automatic hot filling and a preparation method thereof, and relates to the technical field of polyethylene cast film. The polyethylene composite film comprises a corona layer, a core layer, and a heat-sealing layer. The corona layer comprises the following raw materials: linear low-density polyethylene; the core layer comprises the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene, and an imidazole-based ionic liquid containing a linear alkyl group with 6 to 8 carbon atoms; and the heat-sealing layer comprises the following raw materials: linear low-density polyethylene and mesoporous spherical silica. Based on existing polyethylene cast films, the present invention significantly improves the mechanical properties and thermal stability of the polyethylene cast film, such as flex crack resistance and tensile strength, by introducing ionic liquids with specific structures and mesoporous spherical silica into the core layer and heat-sealing layer formulations, thereby effectively avoiding problems such as fisheye blisters, breakage, and leakage of the polyethylene cast film during high-speed automatic hot filling.

Description

Technical Field

[0001] The present application relates to the technical field of polyethylene cast films, and in particular to a polyethylene composite film suitable for automatic hot filling and a preparation method thereof. Background Art

[0002] Polyethylene cast film, also known as non-stretched polyethylene film, abbreviated as CPE, is a flat extruded film primarily produced by casting a polyethylene melt and rapidly quenching it. Polyethylene cast film can be divided into single-layer and multi-layer films. Polyethylene cast film used for packaging on the market generally consists of a corona layer, a core layer, and a heat-seal layer. The corona layer is located on the surface of the film and undergoes corona treatment to increase surface polarity to meet the packaging printing requirements. The overall mechanical properties of the polyethylene cast film, such as puncture resistance, heat-seal strength, and tensile strength, are primarily determined by the core layer and heat-seal layer. Films composed of different formulations for the corona layer, core layer, and heat-seal layer are passed through multiple extruders through a multi-channel composite die head. After uniaxial stretching, they are composited together using chill rollers and further applied to packaging for food, pharmaceuticals, and daily necessities, especially for the rapid and automatic packaging of liquids and powders. They have a wide range of applications.

[0003] In recent years, with the development of the market, higher requirements have been put forward for the quality of polyethylene cast film, so people have continuously optimized the different formula compositions of each layer in the polyethylene cast film in order to achieve the purpose of improving its mechanical properties. For example, the existing patent CN112477347A - a polyethylene cast film resistant to 115 degrees boiling, its production method and packaging bag, by using "corona layer, first core layer, second core layer and heat sealing layer" for compounding and optimizing the formula composition of each layer, improves the high temperature resistance of the polyethylene cast film, and solves the problem of the packaging bag not being resistant to boiling, resulting in breakage, bloating and leakage in the existing technology. For another example, the existing patent CN110509646A - a high puncture resistance cast polyethylene film and its preparation method, by introducing mica powder and a five-layer composite method, significantly improves the puncture resistance of the polyethylene cast film. However, there are few reports in the existing technology on how to deal with the problems of poor flex crack resistance and poor tensile strength of polyethylene cast film, which leads to fish-eye bubbles, breakage and leakage of polyethylene cast film during high-speed automatic hot filling. Figure 1 Therefore, it is necessary to improve the mechanical properties of polyethylene cast film, such as flex crack resistance and tensile strength, to meet the requirements of various automatic packaging equipment. Summary of the Invention

[0004] To solve the above problems, the present application provides a polyethylene composite film suitable for automatic hot filling and a preparation method thereof.

[0005] In a first aspect, the present application provides a polyethylene composite film suitable for automatic hot filling, the polyethylene composite film comprising a corona layer, a core layer and a heat sealing layer;

[0006] The corona layer comprises the following materials: linear low-density polyethylene;

[0007] The core layer comprises the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and imidazole ionic liquid containing a linear alkyl group with a carbon number of 6 to 8;

[0008] The heat sealing layer comprises the following raw materials: linear low-density polyethylene and mesoporous spherical silica.

[0009] Furthermore, in terms of weight percentage, the polyethylene composite film comprises 20-30% of a corona layer, 40-55% of a core layer and 20-35% of a heat-sealing layer.

[0010] Furthermore, the raw material of the corona layer is linear low-density polyethylene.

[0011] Furthermore, the core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 in a weight ratio of (60 to 70): (25 to 30): (5 to 10).

[0012] Furthermore, the heat sealing layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of (80-90):(1-5).

[0013] Furthermore, the imidazolium ionic liquid containing a linear alkyl group with 6 to 8 carbon atoms is at least one selected from 1-pentyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide and 1-heptyl-3-methylimidazolium bromide.

[0014] Furthermore, the property parameters of the mesoporous spherical silica include: a pore diameter of 5-20 nm and a particle size of 5-9 um.

[0015] In a second aspect, the present application provides a method for preparing a polyethylene composite film suitable for automatic hot filling according to any one of the first aspects, the preparation method comprising the following steps:

[0016] Accurately weigh the raw materials of the corona layer, the core layer and the heat-sealing layer in order according to the ratio to obtain the first raw material, the second raw material and the third raw material respectively;

[0017] The first raw material, the second raw material and the third raw material are respectively fed into a first extruder, a second extruder and a third extruder in sequence, and the polyethylene composite film suitable for automatic hot filling is obtained by extrusion casting.

[0018] Furthermore, the working condition parameters of the extrusion casting include: extrusion volume of 280-310 kg / hour; the temperatures of the first to fifth zones of the extruder screw section processing temperature are 140-150°C, 180-190°C, 200-210°C, 200-210°C, and 200-210°C; the melt pump temperature is 195-200°C; the distributor temperature is 195-200°C; the die head temperature is 190-195°C; extrusion parameters: main engine speed 45-50HZ, melt pump speed 65-70HZ; winding parameters: traction is 15-20HZ, winding is 48-55HZ; cooling parameters: roller surface temperature is 25-32°C.

[0019] The above technical solution provided by the embodiment of the present application has at least the following advantages compared with the prior art:

[0020] The embodiments of the present application provide a polyethylene composite film suitable for automatic hot filling. Based on the existing polyethylene cast film, the present invention significantly improves the mechanical properties and thermal stability of the polyethylene cast film, such as flex crack resistance and tensile strength, by introducing ionic liquids and mesoporous spherical silica of specific structures into the core layer and heat-sealing layer formulas, respectively. This effectively avoids problems such as fish-eye bubbles, breakage, and leakage of the polyethylene cast film during high-speed automatic hot filling. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 This is a schematic diagram of fish-eye bubbles appearing on the polyethylene cast film during the automatic hot filling process in an embodiment of the present application.

[0024] Figure 2 A schematic flow chart of a method for preparing a polyethylene composite film suitable for automatic hot filling provided in an embodiment of the present application; DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] In a first aspect, the present application provides a polyethylene composite film suitable for automatic hot filling, the polyethylene composite film comprising a corona layer, a core layer and a heat sealing layer;

[0028] The corona layer comprises the following materials: linear low-density polyethylene;

[0029] The core layer comprises the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and imidazole ionic liquid containing a linear alkyl group with a carbon number of 6 to 8;

[0030] The heat sealing layer comprises the following raw materials: linear low-density polyethylene and mesoporous spherical silica.

[0031] The embodiments of the present application provide a polyethylene composite film suitable for automatic hot filling. Based on the existing polyethylene cast film, the present invention significantly improves the mechanical properties and thermal stability of the polyethylene cast film, such as flex crack resistance and tensile strength, by introducing ionic liquids and mesoporous spherical silica of specific structures into the core layer and heat-sealing layer formulas, respectively. This effectively avoids problems such as fish-eye bubbles, breakage, and leakage of the polyethylene cast film during high-speed automatic hot filling.

[0032] In this application, linear low-density polyethylene (LLDPE) is a copolymer of ethylene and a small amount of α-olefins (such as 1-butene, 1-octene, etc.), and has a molecular structure with very short comonomer branches on a linear ethylene main chain. The density range is 0.918-0.935 g / cm 3 Specifically, you can choose LL6101XR, LL6201XR (Exxon Chemical), 45200 / 4570 (Pureman) and other existing commercially available products, preferably LL6201XR (Exxon Chemical).

[0033] In the present application, low-density polyethylene (LDPE) is the lightest variety of polyethylene resin, with a density between 0.910 and 0.925 g / mL; specifically, existing commercially available products such as LDPE 2426K, LDPE 2047K, and LDPE530A from Dow Chemical can be selected, with LDPE 530A from Dow Chemical being preferred.

[0034] In this application, metallocene linear low-density polyethylene (mLLDPE) is a linear low-density polyethylene obtained by polymerization reaction initiated by metallocene catalyst. Its molecular structure has long side chains. Compared with ordinary linear low-density polyethylene, mLLDPE has weaker intermolecular interaction and relatively larger interchain distance. Specifically, mLLDPE SP1520 produced by Mitsui Chemicals, Evolue series produced by Japan Prime, and Evolue series produced by Japan Prime can be used. TM SP1520、Evolue TM SP0510、Evolue TM SP2040、Evolue TM SP1020、Evolue TM SP0540) and other currently available products on the market, preferably Evolue produced by Japan Preman TM SP0540.

[0035] In the present application, mesoporous spherical silica is a nano-scale porous material with high pore volume, high specific surface area and good pore size distribution characteristics, and is currently commercially available from Hangzhou Jikang New Materials Co., Ltd. and Xinda (brand name).

[0036] In some specific embodiments, the polyethylene composite film comprises, by weight percentage, 20-30% of a corona layer, 40-55% of a core layer, and 20-35% of a heat-sealing layer.

[0037] In some specific embodiments, the raw material of the corona layer is linear low-density polyethylene.

[0038] In some specific embodiments, the core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 in a weight ratio of (60-70): (25-30): (5-10).

[0039] In some specific embodiments, the heat-sealing layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of (80-90):(1-5).

[0040] In some specific embodiments, the imidazolium ionic liquid containing a linear alkyl group with 6 to 8 carbon atoms is selected from at least one of 1-pentyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide and 1-heptyl-3-methylimidazolium bromide.

[0041] In some specific embodiments, the property parameters of the mesoporous spherical silica include: a pore diameter of 5-20 nm and a particle size of 5-9 um.

[0042] In a second aspect, the present application provides a method for preparing a polyethylene composite film suitable for automatic hot filling according to any one of the first aspects, such as Figure 2 As shown, the preparation method comprises the following steps:

[0043] Accurately weigh the raw materials of the corona layer, the core layer and the heat-sealing layer in order according to the ratio to obtain the first raw material, the second raw material and the third raw material respectively;

[0044] The first raw material, the second raw material and the third raw material are respectively fed into a first extruder, a second extruder and a third extruder in sequence, and the polyethylene composite film suitable for automatic hot filling is obtained by extrusion casting.

[0045] The method for preparing a polyethylene composite film suitable for automatic hot filling provided in this application is simple to operate, requires no additional specialized equipment, and is suitable for industrial production. Furthermore, this method for preparing a polyethylene composite film suitable for automatic hot filling is based on the polyethylene composite film suitable for automatic hot filling described in any of the first aspects above, and thus possesses at least all the beneficial effects of the technical solutions of the aforementioned embodiments, which will not be further elaborated here.

[0046] In some specific embodiments, the working condition parameters of the extrusion casting include: extrusion volume of 280-310 kg / h; the temperatures of the first to fifth zones of the extruder screw section processing temperature are 140-150°C, 180-190°C, 200-210°C, 200-210°C, 200-210°C; the melt pump temperature is 195-200°C; the distributor temperature is 195-200°C; the die head temperature is 190-195°C; extrusion parameters: main engine speed 45-50HZ, melt pump speed 65-70HZ; winding parameters: traction is 15-20HZ, winding is 48-55HZ; cooling parameters: roller surface temperature is 25-32°C.

[0047] It should be noted that, unless otherwise specified or explained, the components and raw materials used in the polyethylene composite film suitable for automatic hot filling provided in the examples of this application can be directly commercially available products. Furthermore, unless otherwise specified or explained, the operating steps and parameters involved in the preparation of the polyethylene composite film suitable for automatic hot filling provided in the examples of this application can be carried out according to existing polyethylene cast film preparation processes or using existing equipment.

[0048] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0049] Example 1

[0050] This example provides a polyethylene composite film suitable for automatic hot filling, wherein, in terms of weight percentage, the polyethylene composite film comprises 25% of a corona layer, 45% of a core layer, and 30% of a heat-sealing layer;

[0051] The raw material of the corona layer is linear low-density polyethylene;

[0052] The core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and imidazole ionic liquid containing a linear alkyl group with a carbon number of 6 to 8 in a weight ratio of 65:27:8;

[0053] The heat seal layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of 85:3;

[0054] The linear low-density polyethylene is LL6201XR (Exxon Chemical), the low-density polyethylene is LDPE530A (Dow Chemical), and the metallocene linear low-density polyethylene is Evolue TM SP0540 (Japan Puruiman), the imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 is selected from 1-hexyl-3-methylimidazolium bromide, and the property parameters of the mesoporous spherical silica include: pore diameter of 5-20nm, particle size of 5-9um.

[0055] The method for preparing the polyethylene composite film suitable for automatic hot filling comprises the following steps:

[0056] Accurately weigh the raw materials of the corona layer, the core layer and the heat-sealing layer in order according to the ratio to obtain the first raw material, the second raw material and the third raw material respectively;

[0057] The first raw material, the second raw material and the third raw material are respectively fed into a first extruder, a second extruder and a third extruder in sequence, and the polyethylene composite film suitable for automatic hot filling is obtained by extrusion casting;

[0058] The working condition parameters of the extrusion casting include: extrusion volume of 300 kg / h; the temperatures of the first to fifth zones of the extruder screw section processing temperature are 145°C, 185°C, 206°C, 206°C, and 206°C; the melt pump temperature is 198°C; the distributor temperature is 198°C; the die head temperature is 192°C; the extrusion parameters are: main engine speed 48HZ, melt pump speed 67HZ; winding parameters: traction is 16HZ, winding is 50HZ; cooling parameters: roller surface temperature is 28°C.

[0059] Example 2

[0060] This example provides a polyethylene composite film suitable for automatic hot filling and a preparation method thereof. The only difference from Example 1 is that, in terms of weight percentage, the polyethylene composite film comprises a corona layer of 20%, a core layer of 55% and a heat-sealing layer of 25%; the raw material of the corona layer is linear low-density polyethylene; the core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene and an imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 in a weight ratio of 60:30:10; the heat-sealing layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of 90:3; the imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 is 1-heptyl-3-methylimidazolium bromide; the remaining steps and parameters are the same.

[0061] Example 3

[0062] This example provides a polyethylene composite film suitable for automatic hot filling and a preparation method thereof. The only difference from Example 1 is that, in terms of weight percentage, the polyethylene composite film comprises a 30% corona layer, a 40% core layer, and a 30% heat-sealing layer; the raw material of the corona layer is linear low-density polyethylene; the core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene, and an imidazole ionic liquid containing a linear alkyl group with a carbon number of 6 to 8 in a weight ratio of 60:30:10; the heat-sealing layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of 90:3; the imidazole ionic liquid containing a linear alkyl group with a carbon number of 6 to 8 is 1-heptyl-3-methylimidazolium bromide; the remaining steps and parameters are the same.

[0063] Comparative Example 1

[0064] This example provides a polyethylene composite film and a preparation method thereof. The only difference from Example 1 is that the core layer is composed of the following raw materials: low-density polyethylene and metallocene linear low-density polyethylene in a weight ratio of 65:27 (i.e., no imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 is added); the remaining steps and parameters are the same.

[0065] Comparative Example 2

[0066] This example provides a polyethylene composite film and a preparation method thereof. The only difference from Example 1 is that the heat-sealing layer is linear low-density polyethylene (ie, no mesoporous spherical silica is added); the remaining steps and parameters are the same.

[0067] Comparative Example 3

[0068] This example provides a polyethylene composite film and a preparation method thereof, which differs from Example 1 only in that: the raw material of the corona layer is linear low-density polyethylene; the core layer is composed of the following raw materials: low-density polyethylene and metallocene linear low-density polyethylene in a weight ratio of 65:27; the heat-sealing layer is composed of the following raw materials: linear low-density polyethylene, mesoporous spherical silica and imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 in a weight ratio of 85:3:8 (that is, the mesoporous spherical silica and the imidazole ionic liquid containing a linear alkyl carbon number of 6 to 8 are both introduced into the heat-sealing layer); the remaining steps and parameters are the same.

[0069] Comparative Example 4

[0070] This example provides a polyethylene composite film and a preparation method thereof, which differs from Example 1 only in that 1-hexyl-3-methylimidazolium bromide is replaced by 1-decyl-3-methylimidazolium bromide; the remaining steps and parameters are the same.

[0071] Test Case

[0072] In this example, the performance of the polyethylene composite films obtained in Examples 1 to 3 and Comparative Examples 1 to 4 was tested.

[0073] 1. Flex Crack Resistance Test: The polyethylene composite films obtained in Examples 1-3 and Comparative Examples 1-3 were tested using a Gelbo flex tester according to ASTM F-392. The films were subjected to 8,100 cycles in 1 minute before counting pinholes on paper. The test results are shown in Table 1. A higher number of pinholes indicates poorer flex crack resistance.

[0074] 2. Tensile Strength Test: The polyethylene composite films obtained in Examples 1 to 3 were tested according to ASTM D638-03. The test results are shown in Table 2.

[0075] Table 1

[0076] Test samples Pinhole count (number) Example 1 1 Example 2 4 Example 3 5 Comparative Example 1 36 Comparative Example 2 29 Comparative Example 3 23 Comparative Example 4 21

[0077] Table 2

[0078]

[0079]

[0080] As shown in Tables 1 and 2, the polyethylene composite films provided in Examples of the present invention exhibit excellent properties such as flex crack resistance and tensile strength. Furthermore, the polyethylene composite film obtained in Example 1 was tested for fisheye blisters in accordance with GB / T 6595-86. The test results indicate that the polyethylene composite film obtained in Example 1 did not exhibit fisheye blisters.

[0081] In summary, the embodiments of the present application provide a polyethylene composite film suitable for automatic hot filling and a preparation method thereof. By introducing ionic liquids and mesoporous spherical silica with specific structures into the core layer and heat sealing layer formulas respectively, the mechanical properties and thermal stability of the polyethylene cast film, such as flex crack resistance and tensile strength, are significantly improved, thereby effectively avoiding problems such as fish-eye bubbles, breakage and leakage of the polyethylene cast film during high-speed automatic hot filling.

[0082] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0083] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0084] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. 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 present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A polyethylene composite film suitable for automatic hot filling, characterized in that: The polyethylene composite film comprises a corona layer, a core layer and a heat sealing layer; The raw material of the corona layer is linear low-density polyethylene; The core layer is composed of the following raw materials: low-density polyethylene, metallocene linear low-density polyethylene, and an imidazole ionic liquid containing a linear alkyl group with 6 to 8 carbon atoms in a weight ratio of (60-70): (25-30): (5-10), wherein the imidazole ionic liquid containing a linear alkyl group with 6 to 8 carbon atoms is selected from at least one of 1-pentyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide, and 1-heptyl-3-methylimidazolium bromide; The heat-sealing layer is composed of the following raw materials: linear low-density polyethylene and mesoporous spherical silica in a weight ratio of (80-90): (1-5).

2. The polyethylene composite film suitable for automatic hot filling according to claim 1, characterized in that: In terms of weight percentage, the polyethylene composite film comprises 20-30% of a corona layer, 40-55% of a core layer and 20-35% of a heat sealing layer.

3. The polyethylene composite film suitable for automatic hot filling according to claim 1, characterized in that: The property parameters of the mesoporous spherical silica include: a pore diameter of 5-20 nm and a particle size of 5-9 μm.

4. A method for preparing a polyethylene composite film suitable for automatic hot filling according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Accurately weigh the raw materials of the corona layer, the core layer and the heat-sealing layer in order according to the ratio to obtain the first raw material, the second raw material and the third raw material respectively; The first raw material, the second raw material and the third raw material are respectively fed into a first extruder, a second extruder and a third extruder in sequence, and the polyethylene composite film suitable for automatic hot filling is obtained by extrusion casting.

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