A high-toughness polyethylene composite film and its preparation method

Abstract

This invention discloses a high-toughness polyethylene composite film and its preparation method, belonging to the field of polymer materials. Its outer layer consists of linear low-density polyethylene, ethylene-butyl acrylate copolymer, antioxidant 1010, and ultraviolet absorber UV-531; the middle layer consists of linear low-density polyethylene, polyolefin elastomer, ethylene-butyl acrylate copolymer, stearic acid-modified calcium carbonate, antioxidant, and ultraviolet absorber; the inner layer consists of linear low-density polyethylene, ethylene-butyl acrylate copolymer, antioxidant 1010, and ultraviolet absorber UV-531. The raw materials are dried; heavy calcium carbonate and stearic acid are mixed; each layer is mixed at low speed according to the specified ratio; and the film is produced by three-layer co-extrusion blown film, biaxial stretching, corona treatment, and annealing. The composite film of this application has a surface tension of 40 mN / m, a maximum longitudinal and transverse tensile strength of 23 MPa, a tear strength of 120 kN / m, and an elongation at break of 700%, exhibiting performance superior to products produced by traditional casting and blow molding processes.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a high-toughness polyethylene composite film and its preparation method. Background Technology

[0002] Polyethylene composite films are key materials in packaging, protection, and medical fields, and their toughness directly determines their application reliability. The current market demands increasingly stringent high toughness from composite films, requiring not only excellent tensile and puncture resistance at room temperature but also performance stability in extreme environments, such as impact resistance during -40°C frozen storage, tear resistance after retorting at 121°C, and anti-aging properties for long-term outdoor use. However, in existing technologies, the toughness of linear low-density polyethylene (LLDPE) substrates has an inherent bottleneck; its elongation at break is typically below 600%, and its low-temperature impact strength is less than 20 kJ / m², making it difficult to adapt to high-end applications.

[0003] Polyethylene (PE) faces inherent contradictions in its molecular structure and physical properties, making it difficult to achieve high toughness. Different types of PE, due to differences in crystallinity, face a trade-off between strength and toughness. For example, HDPE has high strength but poor toughness, while LDPE has relatively good toughness, but the polar groups in EBA can synergistically enhance its toughness. Furthermore, excessively rapid cooling during processing reduces toughness, and PE is prone to stress cracking under chemical media or stress, all of which limit its ability to improve toughness.

[0004] To overcome the toughness bottleneck of polyethylene, composite film technology achieves performance improvement through multiple pathways. Multilayer co-extrusion and molecular chain regulation, such as gradient functional layer design and stretching orientation process, can optimize performance; in toughening agents and interface engineering, elastomer blending and rigid particle toughening can improve toughness; nanocomposites and biomimetic design, such as HAP nanosheet array reinforcement and biomimetic multilevel structures, also provide new ideas for improving toughness. Summary of the Invention

[0005] The present invention aims to solve the problem that polyethylene has excellent rigidity but the toughening agent has low heat resistance.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] A high-toughness polyethylene composite film, comprising the following components:

[0008] Outer layer: 70-75 parts linear low-density polyethylene, 15-20 parts ethylene-butyl acrylate copolymer, 0.1-0.5 parts antioxidant 1010, 0.2-1 parts ultraviolet absorber UV-531;

[0009] Middle layer: 60-65 parts linear low-density polyethylene, 20-25 parts polyolefin elastomer, 15-20 parts ethylene-butyl acrylate copolymer, 5 parts stearic acid modified calcium carbonate, 0.1-0.5 parts antioxidant 1010, and 0.2-1 parts ultraviolet absorber UV-531;

[0010] Inner layer: 75-80 parts linear low-density polyethylene, 15-20 parts ethylene-butyl acrylate copolymer, 0.1-0.5 parts antioxidant 1010, and 0.2-1 parts ultraviolet absorber UV-531.

[0011] Preferably, the stearic acid-modified calcium carbonate is obtained by combining and modifying heavy calcium carbonate with stearic acid.

[0012] A method for preparing a high-toughness polyethylene composite film includes the following steps:

[0013] S1: Dry the linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer;

[0014] S2: Take 800-mesh heavy calcium carbonate and 3% stearic acid and add them to a high-speed mixing machine to obtain surface stearic acid modified calcium carbonate powder;

[0015] S3: Add the outer layer, middle layer and inner layer to the low-speed mixer according to the raw material ratio and stir for 10 minutes;

[0016] S4: Using a three-layer co-extrusion blown film machine, the outer layer, middle layer and inner layer are first extruded at different temperatures. Then, the extruded outer layer, middle layer and inner layer are stacked and extruded again. Finally, the product is placed in an 85℃ water bath for longitudinal stretching and then in an 115℃ oven for transverse stretching.

[0017] S5: Perform corona treatment on the molded film material;

[0018] S6: Place the corona-treated membrane material in a 40℃ constant temperature oven for annealing for 24 hours, controlling its heating rate at 5℃ / h and cooling rate at 3℃ / h.

[0019] Preferably, the drying temperature in S1 is set to 60°C and lasts for 4 hours.

[0020] Preferably, the conditions for the high-speed mixer in S2 are 100°C, 300 r / min, for 15 minutes.

[0021] Preferably, the low-speed stirring speed in S3 is 50 r / min.

[0022] Preferably, in the three-layer co-extrusion blown film mill in S4, the feeding stage temperature is set to 140℃, 135℃, and 140℃ from the outer layer to the inner layer; the compression stage temperature is set to 170℃, 165℃, and 170℃ from the outer layer to the inner layer; the metering stage temperature is set to 170℃, 165℃, and 170℃ from the outer layer to the inner layer; and finally, the extrusion die parameters are set to 160℃, 30r / min, and a traction speed of 8m / min.

[0023] Preferably, in step S4, the longitudinal stretching is performed at a rate of 0.5 m / min, and the transverse stretching is performed at a rate of 0.75 m / min.

[0024] Preferably, the power of the corona treatment in S5 is set to 30W*min / m. 2 The electrode spacing is 2mm and the processing rate is 5m / min.

[0025] Preferably, the annealing temperature in step S6 is set to 40°C, and the heating rate is controlled at 5°C / h and the cooling rate is 3°C / h.

[0026] The present invention discloses a high-toughness polyethylene composite film and its preparation method, and its effects and advantages are as follows:

[0027] 1. In this application, the raw materials of each layer are added to a low-speed mixer and the mixing time is 10 minutes to ensure that the additives can be evenly dispersed and avoid local agglomeration.

[0028] 2. In this application, the corona-treated film material used subsequently can avoid stress concentration caused by rapid temperature difference, thereby increasing the surface tension from 32mN / m to 40mN / m.

[0029] 3. In this application, the elastomer network structure of POE and the polar groups of EBA work synergistically to increase the elongation at break of the material to 700% without introducing other substances, and the Vicat softening point is maintained above 105°C.

[0030] 4. In this application, stearic acid modified calcium carbonate improves impact strength by 20% through interfacial lubrication effect, while avoiding the dispersion problem of nanomaterials.

[0031] 5. In this application, the added EBA is used as a compatibilizer. Its polar ester groups form hydrogen bonds with the hydroxyl groups on the surface of calcium carbonate, and its non-polar segments are compatible with the PE matrix, thereby increasing the interfacial bonding strength by 40%.

[0032] 6. In this application, the three-layer co-extrusion blown film process achieves a gradual gradient in the overall structure, with the outer layer modulus reaching 0.3 GPa, the middle layer modulus reaching 0.15 GPa, and the inner layer modulus reaching 0.2 GPa. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Example 1

[0035] This embodiment provides a method for preparing a high-toughness polyethylene composite film, suitable for use in high-toughness films, including the following implementation details:

[0036] Experimental objective:

[0037] Prepare a polyethylene composite film with high toughness.

[0038] Experimental materials:

[0039] Outer layer: 70 parts linear low-density polyethylene, 15 parts ethylene-butyl acrylate copolymer, 0.3 parts antioxidant 1010, and 0.2 parts ultraviolet absorber UV-531;

[0040] Middle layer: 60 parts linear low-density polyethylene, 20 parts polyolefin elastomer, 15 parts ethylene-butyl acrylate copolymer, 5 parts stearic acid modified calcium carbonate, 0.3 parts antioxidant 1010, and 0.2 parts ultraviolet absorber UV-531;

[0041] Inner layer: 75 parts linear low-density polyethylene, 15 parts ethylene-butyl acrylate copolymer, 0.3 parts antioxidant 1010, and 0.2 parts ultraviolet absorber UV-531.

[0042] Experimental steps:

[0043] S1: Dry linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer in a vacuum drying oven at 60°C for 4 hours.

[0044] S2: Take 800-mesh heavy calcium carbonate and 3% stearic acid and add them to a high-speed mixer. Stir at 100℃ and 300r / min for 15 minutes to obtain surface stearic acid modified calcium carbonate powder.

[0045] S3: Mix each layer independently of the total components. The outer, middle and inner layers are mixed in a low-speed mixer for 10 minutes according to the proportions in the experimental raw materials.

[0046] S4: A three-layer co-extrusion blown film machine is used. The temperature of the feeding section is set to 140℃ for the outer layer, 135℃ for the middle layer, and 140℃ for the inner layer. The temperature of the compression section is set to 160℃ for the outer layer, 155℃ for the middle layer, and 140℃ for the inner layer. The temperature of the metering section is set to 170℃ for the outer layer, 165℃ for the middle layer, and 170℃ for the inner layer. The outer, middle, and inner layers are then stacked and extruded at 160℃ and 30r / min. Finally, the extruded mixture is pre-stretched longitudinally in an 85℃ water bath at 0.5m / min and then transversely stretched in a 115℃ oven at 0.75m / min.

[0047] S5: Pass the formed film material through a corona treatment machine, setting the power to 30W*min / m. 2 The electrode spacing is 2mm and the processing speed is 5m / min;

[0048] S6: Place the corona-treated membrane material in a 40℃ constant temperature oven for annealing for 24 hours, controlling its heating rate at 5℃ / h and cooling rate at 3℃ / h.

[0049] Experimental results: See Table 1 for details.

[0050] Table 1: Test Results of Example 1

[0051]

[0052] Example 1 introduces a multi-elastomer synergistic toughening system at the raw material end and enhances interfacial bonding through surface-modified inorganic particles. The process employs a three-layer co-extrusion and biaxial stretching technique to construct a gradient structure, combined with precise temperature field control and post-processing, significantly improving the mechanical properties and surface activity of the film. The resulting composite film exhibits a surface tension of 42 mN / m, longitudinal / transverse tensile strengths of 21 MPa / 23 MPa, and Elemandorf longitudinal / transverse tear strengths of 95 / 120 kN / m. All indicators are significantly superior to similar products prepared using traditional processes, especially achieving a breakthrough improvement in transverse tear performance, meeting the stringent requirements for high-toughness films in high-end packaging, agricultural covering, and other fields. Example 2

[0053] This embodiment provides a method for preparing high-toughness polyethylene composite films with different raw material ratios, characterized by different raw material weight ratios, including the following implementation details:

[0054] Experimental objective:

[0055] High-toughness polyethylene composite film prepared by different raw material ratios

[0056] Experimental materials:

[0057] Outer layer: 75 parts linear low-density polyethylene, 20 parts ethylene-butyl acrylate copolymer, 0.3 parts antioxidant 1010, 1 part ultraviolet absorber UV-531;

[0058] Middle layer: 65 parts linear low-density polyethylene, 25 parts polyolefin elastomer, 20 parts ethylene-butyl acrylate copolymer, 5 parts stearic acid modified calcium carbonate, 0.3 parts antioxidant 1010, and 1 part ultraviolet absorber UV-531;

[0059] Inner layer: 80 parts linear low-density polyethylene, 20 parts ethylene-butyl acrylate copolymer, 0.3 parts antioxidant 1010, and 1 part ultraviolet absorber UV-531.

[0060] Experimental steps:

[0061] S1: Dry linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer in a vacuum drying oven at 60°C for 4 hours.

[0062] S2: Take 800-mesh heavy calcium carbonate and 3% stearic acid and add them to a high-speed mixer. Stir at 100℃ and 300r / min for 15 minutes to obtain surface stearic acid modified calcium carbonate powder.

[0063] S3: Mix each layer independently of the total components. Mix the outer, middle and inner layers of the experimental raw materials in a low-speed mixer for 10 minutes.

[0064] S4: A three-layer co-extrusion blown film machine is used. The temperature of the feeding section is set to 140℃ for the outer layer, 135℃ for the middle layer, and 140℃ for the inner layer. The temperature of the compression section is set to 160℃ for the outer layer, 155℃ for the middle layer, and 140℃ for the inner layer. The temperature of the metering section is set to 170℃ for the outer layer, 165℃ for the middle layer, and 170℃ for the inner layer. The outer, middle, and inner layers are then stacked and extruded at 160℃ and 30r / min. Finally, the extruded mixture is pre-stretched longitudinally in an 85℃ water bath at 0.5m / min and then transversely stretched in a 115℃ oven at 0.75m / min.

[0065] S5: Pass the formed film material through a corona treatment machine, setting the power to 30W*min / m. 2The electrode spacing is 2mm and the processing speed is 5m / min;

[0066] S6: Place the corona-treated membrane material in a 40℃ constant temperature oven for annealing for 24 hours, controlling its heating rate at 5℃ / h and cooling rate at 3℃ / h.

[0067] Experimental results: See Table 2 for details.

[0068] Table 2: Test Results of Example 2

[0069]

[0070] Example 2 prepared a high-toughness polyethylene composite film under the same process conditions as Example 1 by adjusting the raw material ratio. Experimental results showed that the composite film had a surface tension of 41 mN / m, a longitudinal tensile strength of 19 MPa, a transverse tensile strength of 21 MPa, and an Elemandorf tear strength of 90 / 110 kN / m. Compared with Example 1, due to the reduced amount of elastomer and stearic acid-modified calcium carbonate, the properties decreased slightly, but it still maintained high surface activity and mechanical toughness. This indicates that adjusting the raw material ratio has a significant impact on the performance of the composite film. Reducing the toughening components leads to a moderate decrease in toughness, but its performance is still superior to products produced by traditional processes. It is suitable for applications where cost control is more critical and toughness requirements are slightly lower, verifying the feasibility of formula optimization in balancing performance and cost. Comparative Example 1

[0071] A method for preparing a conventional high-toughness polyethylene composite film is provided, comprising the following embodiments:

[0072] Experimental materials:

[0073] 40 parts linear low-density polyethylene, 30 parts low-density polyethylene, 10 parts ethylene-vinyl acetate copolymer, 0.2 parts antioxidant 1010, and 0.3 parts calcium stearate.

[0074] Experimental objective:

[0075] A traditional high-toughness polyethylene composite film was prepared.

[0076] Experimental steps:

[0077] S1: Dry LLDPE, LDPE, and EVA granules in a 60℃ oven for 2-3 hours, then add all raw materials to a high-speed mixer and mix at 300-500 rpm for 10-15 minutes;

[0078] S2: Set the screw speed to 150-200 rpm and the temperature gradient to 140℃-160℃-170℃-180℃. The extruded melt is water-cooled and pelletized to obtain blended pellets. The pellets are then placed in a 60℃ oven to dry for 2 hours.

[0079] S3: Using a single-screw extrusion casting machine with a T-type flat die, set its base temperature to 170-190℃, screw speed to 80-120rpm, and finally cool the casting roller temperature to 20-30℃ to obtain a single-layer tough PE film with a thickness of 50-100μm.

[0080] Experimental results: See Table 3 for details.

[0081] Table 3: Test Results of Comparative Example 1

[0082]

[0083] Comparative Example 1 uses a traditional process to prepare a high-toughness polyethylene composite film. The main raw materials are 40% LLDPE, 30% LDPE, and 10% EVA, with a small amount of antioxidant and lubricant added. A single-layer PE film is obtained through a simple drying, mixing, melt granulation, and single-screw casting process. Experimental results show that the composite film has a surface tension of 31 mN / m, a longitudinal tensile strength of 9.5 MPa, a transverse tensile strength of 8 MPa, and an Elemandorf tear strength of 45 / 50 kN / m. As a representative of the traditional preparation method, its characteristics include a simple raw material system and a single molding process, resulting in significant performance limitations. The surface tension is low, and the tensile strength and tear toughness are far lower than those of Examples 1 and 2, which use a multi-elastomer composite, multi-layer co-extrusion, and biaxial stretching process. This comparative example clearly demonstrates the bottleneck of the traditional process in improving the overall performance of polyethylene composite films, providing a benchmark for comparing the advantages of the new preparation method. Comparative Example 2

[0084] A method for preparing a conventional high-toughness polyethylene composite film is provided, comprising the following embodiments:

[0085] Experimental materials:

[0086] Linear low-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer, high-density polyethylene, antioxidant, ethylene bis-stearamide

[0087] Experimental objective:

[0088] Traditional high-toughness polyethylene composite film is prepared by blow molding process.

[0089] Experimental steps:

[0090] S1: Dry LLDPE, LDPE, EVA and HDPE granules in a 50℃ oven for 4 hours. Add all raw materials to a low-speed mixer and mix for 20 minutes according to the different required formulas.

[0091] S2: The screw diameter of the single-screw extrusion blow molding machine is 50mm, the length-to-diameter ratio is 25:1, and it is equipped with an annular die. The extrusion temperature gradient is set to 150℃-170℃-185℃-190℃, the screw speed is 60-80rpm, the blow-up ratio is 2.5-3, the dual-outlet air ring cooling air temperature is 15-20℃, and the air velocity is 3-5m / s.

[0092] S3: After stretching, flattening and winding, a blown PE film of 30-80μm is obtained.

[0093] Experimental results: See Table 4 for details.

[0094] Table 4: Test Results of Comparative Example 2

[0095]

[0096] Comparative Example 2 uses a traditional blow molding process to prepare a high-toughness polyethylene composite film. The raw materials include LLDPE, LDPE, EVA, HDPE and additives. After drying at 50°C and low-speed mixing, the film is blow-molded by a single screw to obtain a 30-80μm film. The test results show that its surface tension is 33.5mN / m, longitudinal tensile strength is 11.8MPa, transverse tensile strength is 10.6MPa, and Elemandorf tear strength is 58.2 / 65.5kN / m. Compared with the casting process of Comparative Example 1, the bidirectional orientation of blow molding makes its mechanical properties better. However, as a traditional method, its performance is still significantly lower than that of the example using a multi-elastomer and multi-layer co-extrusion process, which reflects the limitations of traditional processes in improving toughness.

[0097] Example 1 uses LLDPE, POE, EBA, etc., in specific proportions as raw materials. Through drying, surface-stearned calcium carbonate modification, multilayer mixing in different proportions, three-layer co-extrusion blown film, biaxial stretching, corona treatment, and annealing, a high-toughness polyethylene composite film is obtained. Its surface tension reaches 42 mN / m, and its longitudinal and transverse tensile strengths are 21 MPa and 23 MPa, respectively. The Elemandorf tear strength is 95 / 120 kN / m (longitudinal / transverse). This example significantly improves the mechanical properties and surface activity of the composite film through synergistic toughening with multiple elastomers, multilayer co-extrusion, and biaxial stretching processes, making it suitable for high-end packaging, agricultural covering, and other applications requiring stringent high toughness.

[0098] Example 2 adjusted the raw material ratio, reducing the amounts of POE, EBA, heavy calcium carbonate, and stearic acid, and prepared a composite film under the same process conditions as Example 1. The results showed a surface tension of 41 mN / m, longitudinal and transverse tensile strengths of 19 MPa and 21 MPa, and an Elemandorf tear strength of longitudinal / transverse = 90 / 110 kN / m. Due to the reduction in toughening components, the performance was slightly lower than in Example 1, but still remained at a high level, making it suitable for scenarios where cost control is more critical and toughness requirements are slightly lower. This verifies the feasibility of formula optimization in balancing performance and cost.

[0099] Comparative Example 1 uses LLDPE, LDPE, EVA, and other raw materials as a traditional casting process to produce a single-layer PE film through drying, mixing, melt granulation, and single-screw casting. Its surface tension is 31 mN / m, longitudinal and transverse tensile strengths are 9.5 MPa and 8 MPa respectively, and tear strength is 45 / 50 kN / m. Due to the simple raw material system and single process, its performance is significantly limited, highlighting the bottleneck of traditional processes.

[0100] Comparative Example 2 used a traditional blow molding process. The raw materials included LLDPE, LDPE, EVA, and HDPE. After drying and mixing, the PE film was produced by single-screw extrusion blow molding. Tests showed a surface tension of 33.5 mN / m, longitudinal and transverse tensile strengths of 11.8 MPa and 10.6 MPa, and a tear strength of 58.2 / 65.5 kN / m. Although the bidirectional orientation of the blow molding process made its performance better than Comparative Example 1, it was still significantly lower than the example, indicating that the traditional process has limitations in improving toughness.

[0101] In summary, Examples 1 and 2 have significant advantages over Comparative Examples 1 and 2. Regarding raw materials, the use of multi-elastomer synergy and surface-modified inorganic particles enhances interfacial bonding. In terms of process, the gradient structure constructed through multi-layer co-extrusion and biaxial stretching techniques improves performance. The surface tension, tensile strength, and tear toughness of Examples 1 and 2 far exceed those of the comparative examples, with Example 1 exhibiting the best performance. Example 2 maintains high performance even after reducing toughening components, demonstrating the significant advantage of the novel preparation method in balancing performance and cost.

[0102] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0103] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0104] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0105] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-toughness polyethylene composite film, characterized in that, Includes the following components: Outer layer: 70-75 parts linear low-density polyethylene, 15-20 parts ethylene-butyl acrylate copolymer, 0.1-0.5 parts antioxidant 1010, 0.2-1 parts ultraviolet absorber UV-531; Middle layer: 60-65 parts linear low-density polyethylene, 20-25 parts polyolefin elastomer, 15-20 parts ethylene-butyl acrylate copolymer, 5 parts stearic acid modified calcium carbonate, 0.1-0.5 parts antioxidant 1010, and 0.2-1 parts ultraviolet absorber UV-531; Inner layer: 75-80 parts linear low-density polyethylene, 15-20 parts ethylene-butyl acrylate copolymer, 0.1-0.5 parts antioxidant 1010, and 0.2-1 parts ultraviolet absorber UV-531.

2. The high-toughness polyethylene composite film as described in claim 1, characterized in that, The stearic acid-modified calcium carbonate is prepared by modifying heavy calcium carbonate with stearic acid.

3. The method for preparing a high-toughness polyethylene composite film according to any one of claims 1-2, characterized in that, Includes the following steps: S1: Dry the linear low-density polyethylene, polyolefin elastomer, and ethylene-butyl acrylate copolymer; S2: Take 800-mesh heavy calcium carbonate and 3% stearic acid and add them to a high-speed mixing machine to obtain surface stearic acid modified calcium carbonate powder; S3: Add the outer layer, middle layer and inner layer to the low-speed mixer according to the raw material ratio and stir for 10 minutes; S4: Using a three-layer co-extrusion blown film machine, the outer layer, middle layer and inner layer are first extruded at different temperatures. Then, the extruded outer layer, middle layer and inner layer are stacked and extruded again. Finally, the product is placed in an 85℃ water bath for longitudinal stretching and then in an 115℃ oven for transverse stretching. S5: Perform corona treatment on the molded film material; S6: Place the corona-treated membrane material in a 40℃ constant temperature oven for annealing for 24 hours, controlling its heating rate at 5℃ / h and cooling rate at 3℃ / h.

4. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, The drying temperature in S1 is set to 60°C and lasts for 4 hours.

5. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, The conditions for the high-speed mixer in S2 are 100℃, 300r / min, for 15 minutes.

6. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, The stirring speed in S3 is 50 r / min.

7. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, In the three-layer co-extrusion blown film mill of S4, the feeding stage temperature is set to 140℃, 135℃, and 140℃ from the outer layer to the inner layer; the compression stage temperature is set to 165℃, 155℃, and 140℃ from the outer layer to the inner layer; the metering stage temperature is set to 170℃, 165℃, and 170℃ from the outer layer to the inner layer; and finally, the extrusion die parameters are set to 160℃, 30r / min, and traction speed of 8m / min.

8. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, In S4, the longitudinal stretching is performed at a rate of 0.5 m / min, and the transverse stretching is performed at a rate of 0.75 m / min.

9. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, The power setting for the corona treatment in S5 is 30W*min / m. 2 The electrode spacing is 2mm and the processing rate is 5m / min.

10. The method for preparing a high-toughness polyethylene composite film as described in claim 3, characterized in that, In S6, the annealing temperature is set to 40℃, and the heating rate is controlled at 5℃ / h and the cooling rate is 3℃ / h.

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