High-toughness polyethylene composite film and preparation method thereof

Abstract

The invention discloses a high-toughness polyethylene composite film and a preparation method thereof, and belongs to the field of high polymer materials. The outer layer is prepared from linear low-density polyethylene, an ethylene-butyl acrylate copolymer, an antioxidant 1010 and an ultraviolet light absorber UV-531; the middle layer is prepared from linear low-density polyethylene, a polyolefin elastomer, an ethylene-butyl acrylate copolymer, stearic acid modified calcium carbonate, an antioxidant and an ultraviolet light absorber; and the inner layer is composed of linear low-density polyethylene, an ethylene-butyl acrylate copolymer, an antioxidant 1010 and an ultraviolet light absorber UV-531. Drying the raw materials; mixing heavy calcium carbonate with stearic acid; each layer is mixed at a low speed according to a ratio; and carrying out three-layer co-extrusion film blowing, two-way stretching, corona and annealing. The surface tension of the composite film reaches 40 mN / m, the maximum longitudinal and transverse tensile strength is 23 MPa, the tearing strength is 120 kN / m, the elongation at break is 700%, and the performance of the composite film is superior to that of traditional casting and blow molding process products.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a high-toughness polyethylene composite film and a preparation method thereof. Background Art

[0002] Polyethylene composite films are key materials for packaging, protection, medical applications, and other fields, and their toughness directly determines their reliability. The current market demand for high toughness in composite films is increasingly stringent, requiring not only excellent tensile and puncture resistance at room temperature but also performance stability in extreme environments, such as impact resistance during frozen storage at -40°C, tear resistance after cooking at 121°C, and aging resistance for long-term outdoor use. However, existing technologies face inherent toughness bottlenecks in linear low-density polyethylene (LLDPE) substrates. Their elongation at break is typically less than 600%, and their low-temperature impact strength is less than 20 kJ / m², making them difficult to adapt to high-end applications. Polyethylene struggles to achieve high toughness due to inherent contradictions between its molecular structure and physical properties. Different types of polyethylene face a strength-toughness trade-off due to varying degrees of crystallinity. For example, HDPE offers high strength but poor toughness. While LDPE offers superior toughness, the polar groups in EBA can synergistically enhance its toughness. Furthermore, excessively rapid cooling during processing can reduce toughness, and polyethylene is susceptible to stress cracking when exposed to chemical media or stress, all of which hinder its toughness improvement.

[0003] To overcome the toughness bottleneck of polyethylene, composite membrane technology is achieving performance improvements through various approaches. Multi-layer co-extrusion and molecular chain manipulation, such as gradient functional layer design and stretch orientation processes, can optimize performance. Toughening agents and interface engineering, such as elastomer blends and rigid particle toughening, can enhance toughness. Nanocomposites and biomimetic designs, such as HAP nanosheet array reinforcement and biomimetic hierarchical structures, also offer new approaches for improving toughness. Summary of the Invention

[0004] The present invention aims to solve the problem that polyethylene has excellent rigidity but the toughening agent has low heat resistance.

[0005] In order to solve the above problems, the present invention provides the following technical solutions: A high-toughness polyethylene composite film comprises the following components: Outer layer: linear low-density polyethylene 70-75 parts, ethylene-butyl acrylate copolymer 15-20 parts, antioxidant 1010 0.1-0.5 parts, ultraviolet absorber UV-531 0.2-1 parts; Middle layer: linear low-density polyethylene 60-65 parts, polyolefin elastomer 20-25 parts, ethylene-butyl acrylate copolymer 15-20 parts, stearic acid-modified calcium carbonate 5 parts, antioxidant 1010 0.1-0.5 parts, ultraviolet absorber UV-531 0.2-1 parts; Inner layer: linear low-density polyethylene 75-80 parts, ethylene-butyl acrylate copolymer 15-20 parts, antioxidant 1010 0.1-0.5 parts, ultraviolet absorber UV-531 0.2-1 parts.

[0006] Preferably, the stearic acid-modified calcium carbonate is obtained by modifying heavy calcium carbonate and stearic acid.

[0007] A method for preparing a high-toughness polyethylene composite film comprises the following steps: S1: drying linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer; S2: 800 mesh heavy calcium carbonate and 3% stearic acid were added to a high-speed mixer to obtain surface stearic acid-modified calcium carbonate powder; S3: Add the outer layer, middle layer and inner layer into a 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, and then the extruded outer layer, middle layer, and inner layer are stacked and extruded. Finally, the product is placed in an 85°C water bath for longitudinal stretching and then in a 115°C oven for transverse stretching; S5: performing corona treatment on the formed film material; S6: The corona treated film is placed in a constant temperature box for annealing at 40°C for 24 hours, with a heating rate of 5°C / h and a cooling rate of 3°C / h.

[0008] Preferably, the drying temperature in S1 is set to 60° C. and lasts for 4 hours.

[0009] Preferably, the conditions of the high-speed mixer in S2 are 100° C. and 300 r / min for 15 minutes.

[0010] Preferably, the speed of the low-speed stirring in S3 is 50 r / min.

[0011] Preferably, in the three-layer co-extrusion film blowing machine in S4, the temperature from the outer layer to the inner layer in the feeding stage is set to 140°C, 135°C, and 140°C; the temperature from the outer layer to the inner layer in the compression stage is set to 170°C, 165°C, and 170°C; the temperature from the outer layer to the inner layer in the metering stage is set to 170°C, 165°C, and 170°C; and finally, the extrusion die head parameters are set to 160°C, 30r / min, and the pulling speed is 8m / min.

[0012] Preferably, 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.

[0013] Preferably, the power of the corona treatment in S5 is 30W*min / m2 , the electrode spacing is 2mm, and the processing rate is 5m / min.

[0014] Preferably, the annealing temperature in S6 is set to 40° C., the heating rate is controlled to be 5° C. / h, and the cooling rate is controlled to be 3° C. / h.

[0015] The high-toughness polyethylene composite film and its preparation method have the following effects and advantages: 1. In this application, the raw materials of each layer are added to a low-speed mixer separately, and the stirring time is 10 minutes to ensure that the additives can be evenly dispersed and avoid local agglomeration.

[0016] 2. In this application, the corona-treated film material subsequently used can avoid stress concentration caused by rapid temperature difference, thereby increasing the surface tension from 32mN / m to 40mN / m.

[0017] 3. In this application, the elastomeric network structure of POE and the polar groups of EVA work synergistically, thereby increasing the elongation at break of the material to 700% without introducing other substances, and maintaining the Vicat softening point above 105°C.

[0018] 4. In this application, stearic acid-modified calcium carbonate improves the impact strength by 20% through the interface lubrication effect, while avoiding the dispersion problem of nanomaterials.

[0019] 5. In this application, EBA is added as a compatibilizer, and its polar ester group forms hydrogen bonds with the hydroxyl groups on the surface of calcium carbonate, and the non-polar segments are compatible with the PE matrix, thereby increasing the interfacial bonding strength by 40%.

[0020] 6. In this application, the modulus of the outer layer of the overall structure reaches 0.3GPa, the modulus of the middle layer reaches 0.15GPa, and the modulus of the inner layer reaches 0.2GPa under the three-layer co-extrusion blown film process, forming a gentle gradient. DETAILED DESCRIPTION

[0021] The technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of further restrictions, the elements defined by the sentence "include..." do not exclude the presence of other identical elements in the process, method, article or apparatus that includes the elements. Example 1

[0023] This embodiment provides a method for preparing a high-toughness polyethylene composite film, which is suitable for use in high-toughness lower films and includes the following implementation contents: Purpose of the experiment: Preparation of polyethylene composite films with high toughness.

[0024] Experimental materials: Outer layer: linear low-density polyethylene 70 parts, ethylene-butyl acrylate copolymer 15 parts, antioxidant 1010 0.3 parts, ultraviolet absorber UV-531 0.2 parts; Middle layer: linear low-density polyethylene 60 parts, polyolefin elastomer 20 parts, ethylene-butyl acrylate copolymer 15 parts, stearic acid-modified calcium carbonate 5 parts, antioxidant 1010 0.3 parts, ultraviolet absorber UV-531 0.2 parts; Inner layer: linear low-density polyethylene 75 parts, ethylene-butyl acrylate copolymer 15 parts, antioxidant 1010 0.3 parts, ultraviolet absorber UV-531 0.2 parts.

[0025] Experimental steps: S1: Dry linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer in a vacuum drying oven at 60 °C for 4 hours; S2: 800-mesh heavy calcium carbonate and 3% stearic acid were added to a high-speed mixer and stirred at 100°C and 300 rpm for 15 minutes to obtain surface stearic acid-modified calcium carbonate powder; S3: The ratio of each layer is independent of the total components, and the outer layer, middle layer, and inner layer are stirred in a low-speed mixer according to the ratio of the experimental raw materials for 10 minutes; S4: A three-layer co-extrusion film blowing machine was used, wherein the temperature of the feeding section was set to 140°C for the outer layer, 135°C for the middle layer, and 140°C for the inner layer; the temperature of the outer layer in the compression section was set to 160°C, 155°C for the middle layer, and 140°C for the inner layer; the temperature of the metering section was set to 170°C for the outer layer, 165°C for the middle layer, and 170°C for the inner layer; the outer, middle, and inner layers were then stacked and extruded at 160°C and 30 r / min; finally, the extruded mixture was pre-stretched longitudinally at 0.5 m / min in an 85°C water bath and stretched transversely at 0.75 m / min in a 115°C oven; S5: Pass the formed film through the corona treater and set the power to 30W*min / m 2 , the electrode spacing is 2mm, and the processing speed is 5m / min; S6: The corona treated film is placed in a constant temperature box for annealing at 40°C for 24 hours, with a heating rate of 5°C / h and a cooling rate of 3°C / h.

[0026] Experimental results: See Table 1 for details.

[0027] Table 1: Test results of Example 1

[0028] Example 1 introduces a multi-elastomer synergistic toughening system at the raw material end, and enhances the interfacial bonding force by surface-modified inorganic particles. The process adopts three-layer co-extrusion and biaxial stretching technology to construct a gradient structure, combined with precise temperature field control and post-processing technology, which significantly improves the mechanical properties and surface activity of the film. The surface tension of the composite film finally obtained reaches 42mN / m, the longitudinal / transverse tensile strength is 21 MPa / 23MPa respectively, and the Elmendorf longitudinal / transverse tear strength is as high as 95 / 120kN / m. All indicators are significantly better than similar products prepared by traditional processes, especially in the transverse tearing performance, achieving a breakthrough improvement, meeting the stringent requirements for high-toughness films in high-end packaging, agricultural covering and other fields. Example 2

[0029] This embodiment provides a method for preparing a high-toughness polyethylene composite film with different raw material ratios, which is characterized by different raw material ratios by weight, and includes the following implementation contents: Purpose of the experiment: Preparation of high-toughness polyethylene composite films with different raw material ratios Experimental materials: Outer layer: linear low-density polyethylene 75 parts, ethylene-butyl acrylate copolymer 20 parts, antioxidant 1010 0.3 parts, ultraviolet absorber UV-531 1 part; Middle layer: linear low-density polyethylene 65 parts, polyolefin elastomer 25 parts, ethylene-butyl acrylate copolymer 20 parts, stearic acid-modified calcium carbonate 5 parts, antioxidant 1010 0.3 parts, ultraviolet absorber UV-531 1 part; Inner layer: 80 parts of linear low-density polyethylene, 20 parts of ethylene-butyl acrylate copolymer, 0.3 parts of antioxidant 1010, and 1 part of ultraviolet absorber UV-531.

[0030] Experimental steps: S1: Dry linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer in a vacuum drying oven at 60 °C for 4 hours; S2: 800-mesh heavy calcium carbonate and 3% stearic acid were added to a high-speed mixer and stirred at 100°C and 300 rpm for 15 minutes to obtain surface stearic acid-modified calcium carbonate powder; S3: Mix the outer, middle and inner layers of each layer independently of the total composition, and stir them in a low-speed mixer for 10 minutes according to the experimental raw materials; S4: A three-layer co-extrusion film blowing machine was used, wherein the temperature of the feeding section was set to 140°C for the outer layer, 135°C for the middle layer, and 140°C for the inner layer; the temperature of the outer layer in the compression section was set to 160°C, 155°C for the middle layer, and 140°C for the inner layer; the temperature of the metering section was set to 170°C for the outer layer, 165°C for the middle layer, and 170°C for the inner layer; the outer, middle, and inner layers were then stacked and extruded at 160°C and 30 r / min; finally, the extruded mixture was pre-stretched longitudinally at 0.5 m / min in an 85°C water bath and stretched transversely at 0.75 m / min in a 115°C oven; S5: Pass the formed film through the corona treater and set the power to 30W*min / m 2 , the electrode spacing is 2mm, and the processing speed is 5m / min; S6: The corona treated film is placed in a constant temperature box for annealing at 40°C for 24 hours, with a heating rate of 5°C / h and a cooling rate of 3°C / h.

[0031] Experimental results: See Table 2 for details.

[0032] Table 2: Test results of Example 2

[0033] In Example 2, a high-toughness polyethylene composite film was prepared under the same process conditions as in Example 1 by adjusting the raw material ratio. The experimental results showed that the surface tension of the composite film was 41 mN / m, the longitudinal tensile strength was 19 MPa, the transverse tensile strength was 21 MPa, and the Elmendorf tear strength was 90 / 110 kN / m. Compared with Example 1, due to the reduction in the amount of elastomer and stearic acid-modified calcium carbonate, various properties decreased slightly, but still maintained high surface activity and mechanical toughness. This shows that the adjustment of the raw material ratio has a significant impact on the performance of the composite film. Reducing the toughening component will lead to a moderate decrease in the toughness index, but its performance is still better than that of traditional process products. It is suitable for application scenarios that are more sensitive to cost control and have slightly lower toughness requirements, verifying the feasibility of formula optimization in balancing performance and cost. Comparative Example 1

[0034] A method for preparing a conventional high-toughness polyethylene composite film is provided, comprising the following implementation contents: Experimental materials: 40 parts of linear low-density polyethylene, 30 parts of low-density polyethylene, 10 parts of ethylene-vinyl acetate copolymer, 0.2 parts of antioxidant 1010, and 0.3 parts of calcium stearate.

[0035] Purpose of the experiment: A conventional high-toughness polyethylene composite film was prepared.

[0036] Experimental steps: S1: Dry LLDPE, LDPE, and EVA pellets in an oven at 60°C for 2-3 hours, then add all the raw materials to a high-speed mixer and mix at 300-500 rpm for 10-15 minutes; S2: The screw speed is set to 150-200 rpm, and the temperature gradient is set to 140°C-160°C-170°C-180°C. The extruded melt is water-cooled and pelletized to obtain blended pellets, which are then placed in a 60°C oven to dry for 2 hours. S3: Use a single-screw extruder with a T-type flat die head, set its base temperature to 170-190°C, the screw speed to 80-120 rpm, and finally cool the casting roller temperature to 20-30°C to obtain a single-layer tough PE film with a thickness of 50-100 μm.

[0037] Experimental results: See Table 3 for details.

[0038] Table 3: Test results of Comparative Example 1

[0039] Comparative Example 1 uses a traditional process to prepare a high-toughness polyethylene composite film. With 40% LLDPE, 30% LDPE, and 10% EVA as the main raw materials, a small amount of antioxidant and lubricant is added, and a single-layer PE film is produced through a simple dry mixing, melt granulation, and single-screw tape casting process. The experimental results show that the composite film has a surface tension of 31mN / m, a longitudinal tensile strength of 9.5MPa, a transverse tensile strength of 8MPa, and an Elmendorf tear strength of 45 / 50kN / m. As a representative of the traditional preparation method, its process characteristics are 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 using 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 comprehensive performance of the polyethylene composite film, providing a comparative benchmark for the advantages of the new preparation method. Comparative Example 2

[0040] A method for preparing a conventional high-toughness polyethylene composite film is provided, comprising the following implementation contents: Experimental materials: Linear low-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer, high-density polyethylene, antioxidant, ethylene bisstearamide Purpose of the experiment: Prepared by traditional high-toughness polyethylene composite film blow molding process.

[0041] Experimental steps: S1: Dry LLDPE, LDPE, EVA, and HDPE pellets in a 50°C oven for 4 hours. Add all raw materials into a low-speed mixer and mix for 20 minutes according to different required formulations. S2: The single-screw extrusion blow molding machine has a screw diameter of 50 mm, an aspect ratio of 25:1, and is equipped with a ring die. The extrusion temperature gradient is set to 150°C-170°C-185°C-190°C, the screw speed is 60-80 rpm, the blow-up ratio is 2.5-3, and the double-inlet air ring cooling air temperature is 15-20°C and the wind speed is 3-5 m / s. S3: The film is pulled, flattened, and then rolled up to obtain a 30-80 μm blown PE film.

[0042] Experimental results: See Table 4 for details.

[0043] Table 4: Comparative Example 2 test results

[0044] Comparative Example 2 uses the 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, a 30-80μm film is produced by single-screw extrusion blow molding. Tests show that its surface tension is 33.5mN / m, longitudinal tensile strength is 11.8MPa, transverse tensile strength is 10.6MPa, and Elmendorf tear strength is 58.2 / 65.5kN / m. Compared with the cast film process of Comparative Example 1, the bidirectional orientation of blow molding makes its mechanical properties better, but as a traditional method, its performance is still significantly lower than the embodiment using multi-elastomer and multi-layer co-extrusion process, reflecting the limitations of traditional processes in improving toughness.

[0045] Example 1: Using LLDPE, POE, EVA, EBA and other raw materials in a specific ratio, a high-toughness polyethylene composite film is prepared through drying, surface stearic acid-modified calcium carbonate preparation, multi-layer mixing in different ratios, three-layer co-extrusion blown film, biaxial stretching, corona treatment and annealing. Its surface tension reaches 42mN / m, the longitudinal and transverse tensile strengths are 21MPa and 23MPa respectively, and the Elmendorf tear strength is 95 / 120kN / m in the longitudinal / transverse direction. This embodiment significantly improves the mechanical properties and surface activity of the composite film through processes such as multi-elastomer synergistic toughening, multi-layer co-extrusion and biaxial stretching, and is suitable for scenes with strict requirements on high toughness, such as high-end packaging and agricultural covering. In Example 2, the raw material ratio was adjusted, reducing the amounts of POE, EVA, EBA, ground calcium carbonate, and stearic acid. A composite film was produced under the same process conditions as in 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 Elmendorf tear strength of 90 / 110 kN / m in the longitudinal and transverse directions. While performance declined slightly compared to Example 1 due to the reduction in toughening components, it still maintained a high level, making it suitable for cost-sensitive applications with slightly lower toughness requirements. This demonstrates the feasibility of formula optimization in balancing performance and cost. Comparative Example 1 used a traditional casting process to produce a single-layer PE film using LLDPE, LDPE, and EVA as raw materials through dry mixing, melt granulation, and single-screw casting. The film exhibited a surface tension of 31 mN / m, longitudinal and transverse tensile strengths of 9.5 MPa and 8 MPa, and a tear strength of 45 / 50 kN / m. However, due to the simple raw material system and single process, its performance was significantly limited, reflecting the bottleneck of the traditional process. Comparative Example 2 employed a conventional blow molding process. Raw materials included LLDPE, LDPE, EVA, and HDPE. After drying and mixing, the resulting PE film was produced by single-screw extrusion blow molding. Testing revealed a surface tension of 33.5 mN / m, longitudinal and transverse tensile strengths of 11.8 MPa and 10.6 MPa, respectively, and tear strengths of 58.2 and 65.5 kN / m. While the bidirectional orientation achieved by blow molding resulted in improved performance compared to Comparative Example 1, it was still significantly lower than that achieved in the Examples, demonstrating the limitations of conventional processes in improving toughness. Overall, Examples 1 and 2 have obvious advantages over Comparative Examples 1 and 2. In terms of raw materials, the use of multi-elastomer synergy and surface-modified inorganic particles enhances interfacial bonding. In terms of process, a gradient structure is constructed through multi-layer co-extrusion, biaxial stretching and other technologies to improve performance. The surface tension, tensile strength and tear toughness of Examples 1 and 2 far exceed those of the comparative example, and Example 1 has the best performance. Example 2 still maintains high performance after reducing the toughening component, reflecting the significant advantages of the new preparation method in balancing performance and cost.

[0046] Those skilled in the art will appreciate that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0047] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0048] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited to this. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0049] Finally: 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 in the scope of protection of the present invention.

Claims

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

2. A high-toughness polyethylene composite film according to 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 to 2, characterized in that: The following steps are involved: S1: drying linear low-density polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer; S2: 800 mesh heavy calcium carbonate and 3% stearic acid were added to a high-speed mixer to obtain surface stearic acid-modified calcium carbonate powder; S3: Add the outer layer, middle layer and inner layer into a 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, and then the extruded outer layer, middle layer, and inner layer are stacked and extruded. Finally, the product is placed in an 85°C water bath for longitudinal stretching and then in a 115°C oven for transverse stretching; S5: corona treating the formed film material; S6: The corona treated film is placed in a constant temperature box at 40°C for annealing for 24 hours, with a heating rate of 5°C / h and a cooling rate of 3°C / h.

4. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: The drying temperature in S1 was set to 60° C. and lasted for 4 hours.

5. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: The conditions of the high-speed mixer in S2 are 100° C. and 300 r / min for 15 minutes.

6. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: The speed of the low-speed stirring in S3 is 50 r / min.

7. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: In the three-layer co-extrusion blown film machine S4, the temperature from the outer layer to the inner layer in the feeding stage is set to 140°C, 135°C, and 140°C; the temperature from the outer layer to the inner layer in the compression stage is set to 165°C, 155°C, and 140°C; the temperature from the outer layer to the inner layer in the metering stage is set to 170°C, 165°C, and 170°C; and finally, the extrusion die head parameters are set to 160°C, 30r / min, and the pulling speed is 8m / min.

8. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: In the S4, the longitudinal stretching was performed at a rate of 0.5 m / min, and the transverse stretching was performed at a rate of 0.75 m / min.

9. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: 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.

10. The method for preparing a high-toughness polyethylene composite film according to claim 3, wherein: The annealing temperature in S6 is set to 40° C., the heating rate is controlled to be 5° C. / h, and the cooling rate is controlled to be 3° C. / h.

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