High-strength and high-toughness al-plastic reinforced polyester film and preparation method thereof

Abstract

The application relates to the field of high polymer synthesis and processing technology, and discloses a high-strength and high-toughness aluminum-plastic reinforced polyester film and a preparation method thereof. The film comprises a first surface film layer, a core film layer and a second surface film layer which are sequentially stacked in the thickness direction. The polyester film is a three-layer co-extrusion biaxial stretching film, and the total thickness is 12-75 microns. The first surface film layer and the second surface film layer both comprise PET polyester material, other polyester material and an opening agent. The core film layer comprises PET polyester material, other polyester material and a toughening agent. During preparation, the surface film layer material and the core film layer material are respectively mixed, melted, plasticized, filtered and extruded, three layers of co-extrusion are formed into a composite casting piece through a T-shaped die head, and then the polyester film is obtained through longitudinal stretching, transverse stretching, edge cutting and winding. Through the three-layer structure and the toughening regulation of the core film layer, the continuous bearing capacity of the film in the low elongation interval and the mechanical balance of different orientation directions are improved, and the film is suitable for being used as an outer layer reinforcing material of an aluminum-plastic film.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and processing technology, and more specifically, to a high-strength, high-toughness aluminum-plastic reinforced polyester film and its preparation method. Background Technology

[0002] Aluminum-plastic film developed alongside the rise of the lithium battery industry, initially used in food and pharmaceutical packaging. Later, due to the demand for lightweight and high-energy-density pouch batteries, it became a core packaging material. Currently, with the expansion of the 3C consumer electronics, electric vehicle, and energy storage industries, its demand continues to climb, with the Chinese market size reaching 6.3 billion yuan by 2025. The industry is in a phase of accelerated domestic substitution. With policy support, domestic companies are gradually breaking through high-end technology bottlenecks, driving the upgrading of aluminum-plastic film towards higher temperature resistance and higher barrier properties to meet the needs of new application scenarios such as solid-state batteries.

[0003] Aluminum-plastic film is a multi-layered composite functional film, primarily used in the packaging of soft-pack lithium batteries. Its structure employs a "sandwich" composite design, consisting of an outer barrier layer, a permeation barrier layer, and a heat-sealing layer from the outside in. Each layer is bonded together with an electrolyte-resistant adhesive, each performing its specific function and working synergistically. The permeation barrier layer, made of aluminum foil, isolates moisture and oxygen, serving as the core of protection. The heat-sealing layer, typically made of polypropylene film, is responsible for heat sealing during packaging and also resists electrolyte corrosion. The outer barrier layer, primarily made of nylon, possesses puncture and abrasion resistance, protecting the inner aluminum foil from damage. However, with the development of power and energy storage technologies, the outer nylon film cannot withstand long-term high-temperature and high-humidity environments, necessitating the search for new alternatives. Current market solutions involve bonding a PET film to the nylon film to enhance its weather resistance. However, ordinary PET film suffers from drawbacks such as a high tensile yield point, slow force increase after the yield point leading to poor impact resistance, and poor isotropy during stretching. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, high-toughness aluminum-plastic reinforced polyester film and its preparation method to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a high-strength and high-toughness aluminum-plastic reinforced polyester film, comprising a first surface film layer, a core film layer and a second surface film layer stacked sequentially along the thickness direction; The high-strength and high-toughness aluminum-plastic reinforced polyester film is a three-layer co-extruded biaxially oriented film with a total thickness of 12-75 μm. The thickness of each single layer of the first and second surface films is 1.2-7.5 μm. By weight, the materials of the first and second surface layers each include: 84-94 parts of PET polyester material, 0-15 parts of other polyester materials, and 1-3 parts of opening agent; By weight, the core film layer comprises: 72-81 parts of PET polyester material, 10-17 parts of other polyester materials, and 2-8 parts of toughening agent; The other polyester material is at least one of PETG, PCTG, PTT, PBAT, PBST and PBT.

[0006] Preferably, the PET polyester material is bottle-grade PET polyester or film-grade PET polyester.

[0007] Preferably, the toughening agent is at least one of PE, PP, EPDM, POE and PHA.

[0008] Preferably, the opening agent is silicon dioxide.

[0009] Preferably, the materials of the first and second surface films each include 85 parts of PET polyester material, 13 parts of PTT polyester material, and 2 parts of silica; the materials of the core film layer include 80 parts of PET polyester material, 15 parts of PTT polyester material, and 5 parts of EPDM.

[0010] On the other hand, the present invention provides a method for preparing the above-mentioned high-strength and high-toughness aluminum-plastic reinforced polyester film, comprising the following steps: The surface film material and the core film material are fed and mixed separately to obtain the surface film mixture and the core film mixture. The surface film layer mixture and the core film layer mixture are respectively melt-plasticized and filtered and extruded to obtain the surface film layer melt and the core film layer melt; The surface film layer melt and the core film layer melt are co-extruded in three layers through a T-die, and then cast into a three-layer composite sheet. The three-layer composite casting is subjected to longitudinal stretching, transverse stretching, edge trimming, and winding in sequence to obtain the high-strength and high-toughness aluminum-plastic reinforced polyester film.

[0011] Preferably, the filtration extrusion temperature of both the surface membrane material and the core membrane material is 275℃-290℃.

[0012] Preferably, the longitudinal stretching includes longitudinal preheating, longitudinal stretching, and longitudinal shaping; The longitudinal preheating temperature is 81-92℃, the longitudinal stretching temperature is 83-94℃, the longitudinal stretching ratio is 2.5-4.0 times, the longitudinal setting temperature is 75-80℃, and the total time for the longitudinal preheating, longitudinal stretching, and longitudinal setting is 2-5 seconds.

[0013] Preferably, the transverse stretching includes transverse preheating, transverse stretching, and transverse shaping; The temperature for lateral preheating is 80-88℃, the temperature for lateral stretching is 83-105℃, the lateral stretching ratio is 3.0-4.5 times, the temperature for lateral shaping is 145-189℃, the air volume power in the lateral shaping zone is 80-90%, the lateral stretching time is 3-5s, and the lateral shaping time is 10-15s.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The high-strength, high-toughness aluminum-plastic reinforced polyester film provided by this invention adopts a three-layer composite structure consisting of a first surface film layer, a core film layer, and a second surface film layer. By differentiating the materials of the surface film layer and the core film layer, the outer side of the film maintains the surface stability and processing adaptability required for polyester film, while the core film layer undertakes the role of toughness adjustment and tensile deformation buffering. This improves the problems of high yield point, discontinuous force growth after yielding, and uneven stress during deformation of ordinary PET film during stretching.

[0015] This invention introduces PET polyester material, other polyester materials, and an opening agent into the surface film layer, enabling the surface film layer to have a stable surface state and winding processing performance after co-extrusion biaxial stretching; and introduces PET polyester material, other polyester materials, and a toughening agent into the core film layer, enabling the core film layer to provide continuous deformation load-bearing capacity in the initial stretching stage and low elongation range, reducing the force plateau phenomenon in the stretching curve, and improving the force response of the film in the breaking elongation range within 30%.

[0016] This invention utilizes a three-layer co-extruded biaxial stretching structure to create a synergistic force-bearing structure in the thickness direction among the first surface film layer, the core film layer, and the second surface film layer. The toughness adjustment effect of the core film layer can be constrained and transmitted by the upper and lower surface film layers, which helps to reduce the mechanical property differences between different sampling directions such as MD, TD, 45°, and 135°, thereby improving the isotropic mechanical properties of the film.

[0017] The polyester film obtained by this invention can be used as an outer layer reinforcement material for aluminum-plastic films. During the subsequent lamination, deep drawing and packaging processes of aluminum-plastic films, it provides outer tensile, impact and puncture resistance protection for the aluminum foil barrier layer, reducing the risk of outer layer protection failure caused by ordinary PET films due to obvious stretching plateau, insufficient strength in the low elongation zone or excessive difference in directional properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The tensile stress-elongation curves for different orientation directions provided in Embodiment 1 of the present invention are shown.

[0020] Figure 2 The tensile stress-elongation curves for different orientation directions provided in Embodiment 2 of the present invention are shown.

[0021] Figure 3 The tensile stress-elongation curves for different orientations are shown in Comparative Example 1 of this invention.

[0022] Figure 4 The tensile stress-elongation curves for different orientations are shown in Comparative Example 2 of this invention.

[0023] Figure 5 The tensile stress-elongation curves for different orientations are shown in Comparative Example 3 of this invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In this invention, the mechanical properties of the film are tested as follows: sample strips are cut along the MD direction, 45° direction, TD direction and 135° direction respectively, 10 sample strips are cut in each direction, and the sample strip size is 20cm×1.5cm; a universal tensile testing machine is used to perform tensile testing on the sample strips at a tensile speed of 50mm / min, and the yield point force value, the force value corresponding to the elongation at break reaching 30% and the range of elongation at break of the force plateau are recorded.

[0026] Isotropy is represented by the difference between the maximum and minimum stress values ​​in the MD, 45°, TD, and 135° directions when the elongation at break reaches 30%. A difference not exceeding 10N indicates that the isotropy of the film meets the usage requirements. The force plateau elongation at break range refers to the length of the interval in the tensile curve where the force value does not increase with increasing elongation at break (i.e., the slope is 0). A larger force plateau elongation at break range indicates a more pronounced plateauing phenomenon in the film during the tensile process.

[0027] In the following examples and comparative examples, the PET polyester material used is polyethylene terephthalate (PET) chips. The PET chips are formed by polycondensation of terephthalic acid or dimethyl terephthalate with ethylene glycol via esterification or transesterification, and the polymer backbone contains repeating PET structural units. The PET chips are film-grade chips with an intrinsic viscosity of 0.62 dL / g-0.70 dL / g, a melting point of 250℃-260℃, and a terminal carboxyl group content not exceeding 35 mol / t. Before use, they are dried to a moisture content not exceeding 50 ppm.

[0028] PTT polyester material uses polypropylene terephthalate chips. These polypropylene terephthalate chips are formed by the condensation polymerization of terephthalic acid or dimethyl terephthalate with 1,3-propanediol after esterification or transesterification, and the polymer backbone contains repeating terephthalate structural units. The intrinsic viscosity of the polypropylene terephthalate chips is 0.85 dL / g-1.05 dL / g, the melting point is 220℃-230℃, and they are dried to a moisture content not exceeding 80 ppm before use.

[0029] The PETG polyester material is made from terephthalic acid-based copolyester chips modified with ethylene glycol and 1,4-cyclohexanediethanol. In the PETG polyester material, the dicarboxylic acid structural units include terephthalic acid structural units, and the diol structural units include ethylene glycol and 1,4-cyclohexanediethanol structural units; based on the total molar amount of diol structural units, the content of 1,4-cyclohexanediethanol structural units is 20 mol%-40 mol%, and the content of ethylene glycol structural units is 60 mol%-80 mol%. The glass transition temperature of the PETG polyester material is 75℃-85℃, the melt flow rate is 8 g / 10 min-20 g / 10 min, and the test conditions are 230℃ and 2.16 kg.

[0030] EPDM is made from ethylene-propylene-5-ethylene-2-norbornene terpolymer granules. In the ethylene-propylene-5-ethylene-2-norbornene terpolymer granules, the mass content of ethylene structural units is 50%-70%, the mass content of propylene structural units is 25%-47%, and the mass content of 5-ethylene-2-norbornene structural units is 3%-8%; the Mooney viscosity ML(1+4) at 125℃ is 40-70. The EPDM does not contain mineral oil filler components, and the ash content is not higher than 1.0%.

[0031] The PE used is ethylene-1-butene copolymerized linear low-density polyethylene granules. These ethylene-1-butene copolymerized linear low-density polyethylene granules are formed by copolymerizing ethylene and 1-butene. The polymer backbone has a linear polyethylene structure, and the molecular chain contains short branched structures introduced by 1-butene. The density of the PE is 0.915 g / cm³-0.935 g / cm³, the melt flow rate is 1 g / 10 min-10 g / 10 min, and the test conditions are 190℃ and 2.16 kg.

[0032] The silica opening agent uses amorphous precipitated silica powder. This amorphous precipitated silica powder is obtained by reacting sodium silicate with an inorganic acid to form hydrated silica, followed by washing, drying, and pulverizing. Its main component is SiO2; by mass percentage, the SiO2 content is not less than 98%, the average particle size D50 is 2μm-5μm, the oil absorption value is 180mL / 100g-280mL / 100g, and the loss on ignition is not higher than 5%. This silica opening agent is used to reduce interlayer adhesion of the film and improve the film winding and unfolding properties.

[0033] Unless otherwise stated, the raw materials with the same name in the following examples and comparative examples are of the same specifications to eliminate the influence of differences in raw material specifications on the test results.

[0034] Example 1

[0035] This embodiment provides a high-strength, high-toughness aluminum-plastic reinforced polyester film, which is prepared by a three-layer co-extrusion biaxial stretching process.

[0036] In this embodiment, the PET polyester material is made from the above-mentioned polyethylene terephthalate chips, the PTT polyester material is made from the above-mentioned polyethylene terephthalate chips, the toughening agent is made from the above-mentioned ethylene-propylene-5-ethylidene-2-norbornene terpolymer granules, and the opening agent is made from the above-mentioned amorphous precipitated silica powder.

[0037] The total thickness of the film is 25 μm, of which the thickness of the first and second surface films is 2.5 μm each, and the thickness of the core film is 20 μm.

[0038] By weight, the materials of both the first and second outer film layers include: 85 parts of polyethylene terephthalate chips, 13 parts of propylene terephthalate chips, and 2 parts of amorphous precipitated silica powder.

[0039] By weight, the core film material includes: 80 parts of polyethylene terephthalate chips, 15 parts of propylene terephthalate chips, and 5 parts of ethylene-propylene-5-ethylidene-2-norbornene terpolymer granules.

[0040] The preparation process is as follows: The raw materials for the surface film layer and the core film layer are mixed evenly according to the formula, and then fed into the corresponding twin-screw extruder for melt plasticizing and filtration extrusion. The extrusion temperature of the core film layer is 280℃, and the extrusion temperature of the surface film layer is 275℃. The extruded melt is co-extruded through a T-die and then cast to obtain a three-layer composite sheet.

[0041] The three-layer composite casting sheet was sequentially stretched longitudinally and laterally. During longitudinal stretching, the preheating temperature was 85℃, the stretching temperature was 87℃, the stretching ratio was 3.0 times, the setting temperature was 77℃, and the total time for preheating, stretching, and setting was 3 seconds. During transverse stretching, the preheating temperature was 85℃, the stretching temperature was 85℃, the stretching ratio was 3.5 times, the setting temperature was 168℃, the airflow rate in the setting zone was 85%, the stretching time was 3 seconds, and the setting time was 12 seconds. After stretching, the film was trimmed and wound up to obtain the high-strength, high-toughness aluminum-plastic reinforced polyester film.

[0042] See Figure 1 As shown, the obtained film was tested, and the results showed that the yield point forces in the MD direction, 45° direction, TD direction, and 135° direction were 25.3N, 25.3N, 25.3N, and 24.9N, respectively; the stress values ​​at 30% elongation at break were 49.7N, 58.5N, 58.0N, and 58.5N, respectively; the isotropic difference was 8.8N; and the force plateau range at 0% elongation at break was 0% in all directions. This indicates that the film obtained in this embodiment exhibits a continuous force increase characteristic in the low elongation range, and the mechanical differences between different orientation directions meet the application requirements.

[0043] Example 2

[0044] This embodiment is basically the same as Embodiment 1, except that the toughening agent in the core film material is replaced by ethylene-propylene-5-ethylidene-2-norbornene terpolymer granules with ethylene-1-butene copolymer linear low-density polyethylene granules.

[0045] By weight, the core film material includes: 80 parts of polyethylene terephthalate chips, 15 parts of propylene terephthalate chips, and 5 parts of ethylene-1-butene copolymer linear low-density polyethylene granules.

[0046] The formulation, layer structure, thickness, and preparation process parameters of the remaining surface film materials are the same as those in Example 1.

[0047] See Figure 2As shown, the obtained film was tested, and the results showed that the yield point forces in the MD, 45°, TD, and 135° directions were 26.1N, 26.1N, 25.5N, and 26.2N, respectively; the stress values ​​at 30% elongation at break were 57.3N, 57.7N, 48.5N, and 57.1N, respectively; the isotropic difference was 9.2N; and the force plateau range at elongation at break in all directions was 0%. This indicates that when ethylene-1-butene copolymer linear low-density polyethylene granules are used as a toughening agent for the core film layer, they can still improve the stress continuity of the film in the low elongation range and control the isotropic difference within 10N.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that no other polyester materials were added to the first surface film layer, the second surface film layer, and the core film layer.

[0050] The total thickness of the film is 25 μm, of which the thickness of the first and second surface films is 2.5 μm each, and the thickness of the core film is 20 μm.

[0051] By weight, the materials of both the first and second outer film layers include: 98 parts of polyethylene terephthalate chips and 2 parts of amorphous precipitated silica powder.

[0052] By weight, the core membrane material includes: 95 parts of polyethylene terephthalate chips and 5 parts of ethylene-propylene-5-ethylidene-2-norbornene terpolymer granules.

[0053] The preparation process parameters are the same as in Example 1.

[0054] See Figure 3 As shown, the obtained film was tested, and the results showed that the yield point forces in the MD direction, 45° direction, TD direction, and 135° direction were 30.3N, 29.5N, 30.9N, and 30.3N, respectively; the stress values ​​at 30% elongation at break were 60.5N, 60.2N, 50.9N, and 59.1N, respectively; the isotropic difference was 9.6N; and force plateaus of 3% and 2% elongation at break appeared in the 45° and TD directions, respectively. Compared with Example 1, this comparative example, in the absence of other polyester materials, although some force indicators still reached a certain level, a force plateau began to appear during the stretching process, indicating that other polyester materials are beneficial to reducing the plateau phenomenon of the stretching curve.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that no toughening agent was added to the core film layer material.

[0057] By weight, the materials of both the first and second outer film layers include: 85 parts of polyethylene terephthalate chips, 13 parts of propylene terephthalate chips, and 2 parts of amorphous precipitated silica powder.

[0058] By weight, the core film material includes: 85 parts of polyethylene terephthalate chips and 15 parts of propylene terephthalate chips.

[0059] The structure, thickness, and preparation process parameters of the remaining layers are the same as in Example 1.

[0060] See Figure 4 As shown, the obtained film was tested, and the results showed that the yield point forces in the MD direction, 45° direction, TD direction, and 135° direction were 29.6N, 29.7N, 28.3N, and 29.9N, respectively; the stress values ​​at 30% elongation at break were 56.7N, 57.3N, 47.5N, and 57.8N, respectively; the isotropic difference was 10.3N; and force plateaus of 2% and 5% elongation at break appeared in the TD direction and 135° direction, respectively. Compared with Example 1, this comparative example, in the absence of toughening agent, showed an isotropic difference exceeding 10N, and force plateaus appeared in some directions, indicating that the toughening agent in the core film layer is beneficial to improving the stress balance between different orientation directions.

[0061] Comparative Example 3

[0062] The difference between this comparative example and Example 1 is that the longitudinal stretching ratio is adjusted to 2.0 times.

[0063] The specifications of the polyethylene terephthalate chips, polyethylene terephthalate chips, ethylene-propylene-5-ethylidene-2-norbornene terpolymer granules, and amorphous precipitated silica powder used in this comparative example are the same as those in Example 1; the formulations of the surface film material, the core film material, the layer structure, the thickness, and the preparation process parameters except for the longitudinal stretching ratio are all the same as those in Example 1.

[0064] See Figure 5As shown, the obtained film was tested, and the results showed that the yield point forces in the MD, 45°, TD, and 135° directions were 23.5 N, 24.5 N, 29.9 N, and 25.8 N, respectively; the stress values ​​at 30% elongation at break were 47.9 N, 47.7 N, 59.9 N, and 50.7 N, respectively; the isotropic difference was 12.2 N; and force plateaus at 8%, 10%, 5%, and 9% of the elongation at break were observed in the MD, 45°, TD, and 135° directions, respectively. Compared with Example 1, in this comparative example, when the longitudinal stretching ratio was less than 2.5 times, the isotropic difference significantly exceeded 10 N, and force plateaus appeared in all directions, indicating that insufficient longitudinal stretching ratio weakens the orientation uniformity of the three-layer composite film in different directions.

[0065] The test results of the above embodiments and comparative examples are summarized and shown in Table 1.

[0066] Table 1

[0067] Test Result Analysis

[0068] The test results of Examples 1-2 and Comparative Examples 1-3 show that the three-layer co-extruded biaxially oriented film composed of PET polyester material, other polyester materials and toughening agent can improve the force value when the elongation at break reaches 30% while keeping the yield point force value within a suitable range, reduce the force value plateau in the tensile curve, and reduce the mechanical property differences between the MD direction, 45° direction, TD direction and 135° direction.

[0069] Comparative Example 1, without the addition of other polyester materials, showed force plateaus in the 45° and TD directions, indicating that other polyester materials help reduce these force plateaus. Comparative Example 2, without the addition of a toughening agent, showed an isotropic difference of 10.3 N and force plateaus in some directions, indicating that the toughening agent helps improve the tensile deformation coordination of the core film layer. Comparative Example 3 had a longitudinal stretching ratio lower than the range specified in this invention, an isotropic difference of 12.2 N, and force plateaus in all directions, indicating that insufficient longitudinal stretching ratio leads to uneven film orientation.

[0070] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A high-strength, high-toughness aluminum-plastic reinforced polyester film, characterized in that, It includes a first surface film layer, a core film layer, and a second surface film layer, which are sequentially stacked along the thickness direction; The high-strength and high-toughness aluminum-plastic reinforced polyester film is a three-layer co-extruded biaxially oriented film with a total thickness of 12-75 μm. The thickness of each single layer of the first and second surface films is 1.2-7.5 μm. By weight, the materials of the first and second surface layers each include: 84-94 parts of PET polyester material, 0-15 parts of other polyester materials, and 1-3 parts of opening agent; By weight, the core film layer comprises: 72-81 parts of PET polyester material, 10-17 parts of other polyester materials, and 2-8 parts of toughening agent; The other polyester material is at least one of PETG, PCTG, PTT, PBAT, PBST and PBT.

2. The high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 1, characterized in that, The PET polyester material is either bottle-grade PET polyester or film-grade PET polyester.

3. The high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 1, characterized in that, The toughening agent is at least one of PE, PP, EPDM, POE and PHA.

4. The high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 1, characterized in that, The opening agent is silicon dioxide.

5. The high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 1, characterized in that, The materials of the first and second surface films each include 85 parts of PET polyester material, 13 parts of PTT polyester material, and 2 parts of silica; the materials of the core film layer include 80 parts of PET polyester material, 15 parts of PTT polyester material, and 5 parts of EPDM.

6. The high-strength, high-toughness rate-reinforced polyester film according to claim 1, characterized in that, The high-strength, high-toughness, rate-reinforced polyester film was used as a sample strip. Sample strips were cut along the MD direction, 45° direction, TD direction, and 135° direction, with multiple sample strips cut in each direction. The sample strip size was 20cm × 1.5cm. Tensile tests were performed on the sample strips at a tensile speed of 50mm / min. The yield point force, the force value corresponding to the elongation at break reaching 30%, and the range of elongation at break at the force plateau were recorded. The high-strength, high-toughness rate-reinforced polyester film has a yield point force ≤28N and a force plateau elongation at break range of 0%.

7. A method for preparing a high-strength, high-toughness aluminum-plastic reinforced polyester film as described in any one of claims 1-6, characterized in that, Includes the following steps: The surface film material and the core film material are fed and mixed separately to obtain the surface film mixture and the core film mixture. The surface film layer mixture and the core film layer mixture are respectively melt-plasticized and filtered and extruded to obtain the surface film layer melt and the core film layer melt; The surface film layer melt and the core film layer melt are co-extruded in three layers through a T-die, and then cast into a three-layer composite sheet. The three-layer composite casting is subjected to longitudinal stretching, transverse stretching, edge trimming, and winding in sequence to obtain the high-strength and high-toughness aluminum-plastic reinforced polyester film.

8. The method for preparing high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 7, characterized in that, The filtration extrusion temperature of both the surface membrane material and the core membrane material is 275℃-290℃.

9. The method for preparing high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 7, characterized in that, The longitudinal stretching includes longitudinal preheating, longitudinal stretching, and longitudinal shaping; The longitudinal preheating temperature is 81-92℃, the longitudinal stretching temperature is 83-94℃, the longitudinal stretching ratio is 2.5-4.0 times, the longitudinal setting temperature is 75-80℃, and the total time for the longitudinal preheating, longitudinal stretching, and longitudinal setting is 2-5 seconds.

10. The method for preparing high-strength, high-toughness aluminum-plastic reinforced polyester film according to claim 7, characterized in that, The transverse stretching includes transverse preheating, transverse stretching, and transverse shaping; The temperature for lateral preheating is 80-88℃, the temperature for lateral stretching is 83-105℃, the lateral stretching ratio is 3.0-4.5 times, the temperature for lateral shaping is 145-189℃, the air volume power in the lateral shaping zone is 80-90%, the lateral stretching time is 3-5s, and the lateral shaping time is 10-15s.

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