High-toughness PET film and preparation method thereof

Abstract

The invention belongs to the technical field of polymer film materials. The invention relates to a PET film, in particular to a high-toughness PET film and a preparation method thereof. The preparation method comprises the following specific preparation steps: dissolving polyethylene glycol terephthalate resin with a solvent to obtain a PET solution with the mass fraction of 10-20%; adding nano boehmite, ethyl acetate and acetone into the PET solution, and uniformly dispersing to obtain a film forming solution; after the film forming liquid is subjected to curtain coating and blade coating forming, drying and hot press forming are conducted, and the high-toughness PET film is obtained; wherein the dosage of the nano boehmite is 10-15% of the mass of the polyethylene glycol terephthalate resin; the dosage of the ethyl acetate is 40-50% of the mass of the nano boehmite; the use amount of the acetone is 30-40% of the mass of the nano boehmite; the particle size distribution range of the nano boehmite is 2 to 150 nm, and D50 is 80 to 85 nm.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer thin film materials. More specifically, it relates to a high-toughness PET film and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) film, with its excellent thermal stability, mechanical strength, and chemical resistance, has become an ideal choice for high-performance packaging materials and has been widely used in the packaging of food, pharmaceuticals, and electronic products.

[0003] Nanoparticles exhibit unique physical and chemical properties, including a high specific surface area, significant surface energy, and excellent dispersion performance. These characteristics have enabled PET films to be widely used in the field of material modification. In the academic field of exploring PET film modification, commonly used nanomaterials by researchers include silicate (SiO2), zinc oxide (ZnO), silver nanoparticles (Ag), and titanium dioxide (TiO2), etc. These nanoparticles with nanoscale sizes can enter the molecular voids of PET films and effectively enhance the mechanical strength, barrier effect, and antibacterial function of the PET films at the microscopic level.

[0004] Generally speaking, although the addition of nanoparticles can improve the above-mentioned properties of PET films, the inventors have found that after actual addition, the PET film products do not always achieve the expected mechanical strength, especially the toughness of the film. Therefore, for PET films added with nanoparticles, how to obtain the expected mechanical strength remains one of the technical problems to be faced in this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: aiming at the problem that traditional PET films cannot obtain the expected mechanical properties after adding nanoparticles. The present invention provides a high-toughness PET film and a preparation method thereof.

[0006] The purpose of the present invention is to provide a preparation method of a high-toughness PET film.

[0007] Another purpose of the present invention is to provide a high-toughness PET film.

[0008] The above purposes of the present invention are achieved by the following technical solutions:

[0009] A preparation method of a high-toughness PET film, the specific preparation steps include:

[0010] Dissolve polyethylene terephthalate resin with a solvent to obtain a PET solution with a mass fraction of 10 - 20%.

[0011] Add nano-boehmite, ethyl acetate and acetone to the PET solution, disperse evenly to obtain a film-forming solution;

[0012] After the film-forming solution is cast and scraped into shape, it is dried and hot-pressed into a high-toughness PET film;

[0013] Among them, the dosage of nano-boehmite is 10-15% of the mass of polyethylene terephthalate resin;

[0014] The dosage of ethyl acetate is 40-50% of the mass of nano-boehmite;

[0015] The dosage of acetone is 30-40% of the mass of nano-boehmite;

[0016] The particle size distribution range of nano-boehmite is 2-150 nm, and D50 is 80-85 nm.

[0017] The beneficial effects of the above technical solutions are as follows:

[0018] The inventor found in the actual research process that directly adding nano-inorganic particles to the PET resin system will inevitably lead to the following problems during the actual film-forming process. For example, when using conventional melt co-extrusion processes or solvent casting film-forming methods, the agglomeration of nano-inorganic particles will occur, resulting in uneven dispersion of nano-inorganic particles in the PET film matrix, and ultimately forming stress concentration points in the product, leading to a decrease in the toughness of the PET film; another example is that the interfacial compatibility between nano-inorganic particles and PET resin is poor, resulting in limited bonding strength between the two. When subjected to external forces, the interface is prone to debonding or crack propagation, thus causing a decrease in the toughness of the product; in addition, if the particle raw materials are not selected properly, it is easy to have more internal defects during the film-forming process due to too high particle hardness or irregular shape, thereby reducing the toughness of the product;

[0019] Based on the findings in the above research process, in the above technical solution, by using boehmite with a relatively low Mohs hardness as the nano-filler, compared with conventional nano-aluminum oxide, nano-titanium dioxide, etc., its Mohs hardness is significantly lower. Therefore, due to the selection of raw materials with a relatively lower Mohs hardness at the raw material level, the internal defects during the film-forming process are reduced, and the toughness of the product will not decrease due to this;

[0020] Based on the selection of the boehmite raw materials, the inventors further studied and found that during the processing, the particle size distribution range of nano-boehmite must be regulated. This is because, for the method of casting and doctor blading to form a film, during the drying and hot pressing processes, boehmite particles with different particle sizes will redistribute in the thickness direction of the PET film under the action of solvent evaporation and their own gravity. Specifically, the smaller the particle size in the powder, the lighter its mass, and the relatively larger its specific surface area, and the stronger its interaction with the solvent. Therefore, it is easier to float during the solvent evaporation process, while the larger the particle size, the opposite. By selecting a relatively wide particle size distribution range for boehmite, especially within the above-defined range, a relatively uniform distribution in the thickness direction can be achieved, avoiding the over-concentration of the particle size distribution, resulting in a more concentrated dispersion in the thickness direction. A uniform distribution in the thickness direction is beneficial to the uniformity of the overall stress of the film, thereby making the mechanical properties of the product relatively better;

[0021] In addition, on the basis of the above technical solution, ethyl acetate and acetone are selected and combined. Among them, the ester groups in the molecular structure of ethyl acetate and the ester groups in the molecular structure of PET resin have good compatibility, which can promote the swelling and dispersion of PET resin. Moreover, ethyl acetate and acetone can form a miscible system, and this miscible system also has good compatibility with boehmite (γ-AlOOH) with polar functional groups, thereby assisting the uniform dispersion of boehmite in the PET solution; Most importantly, due to the interaction between the ethyl acetate and acetone miscible system and the hydroxyl groups on the surface of boehmite particles, during the drying process of the product, boehmite particles can achieve a uniform distribution in the thickness direction with the evaporation of such solvents, avoiding the settlement of boehmite particles at the bottom in the thickness direction due to gravity.

[0022] Furthermore, the solvent comprises the following raw materials in weight fractions:

[0023] 100 - 120 parts of phenol, 80 - 100 parts of carbon tetrachloride, 2 - 4 parts of plasticizer;

[0024] The plasticizer is selected from any one of epoxy soybean oil, pentaerythritol stearate, citrate, and diacetyl monoglyceride.

[0025] Furthermore, the specific preparation steps further include:

[0026] Pre-treat the nano-boehmite, and the pre-treatment steps specifically include:

[0027] Mix nano-boehmite, silane coupling agent, and sodium dodecylbenzenesulfonate and pour them into an ethanol solution. After ultrasonic dispersion, spray drying is carried out to obtain pre-treated nano-boehmite;

[0028] Add pretreated nano-boehmite, ethyl acetate and acetone to the PET solution, and shear and disperse evenly at a shear rate of 6000 - 8000 r / min to obtain a film-forming solution;

[0029] After the film-forming solution is cast and scraped into shape, it is dried and hot-pressed to obtain a high-toughness PET film.

[0030] The beneficial effects of the above technical solution are as follows:

[0031] Furthermore, the nano-boehmite is not directly added to the film-forming solution, but is first pretreated with a silane coupling agent and sodium dodecylbenzenesulfonate. Among them, the silane coupling agent can improve the interfacial compatibility between the nano-boehmite and the PET resin. Under the action of sodium dodecylbenzenesulfonate, it is easier to form spherical agglomerate particles during the spray drying process. However, in this agglomerate, the force between the boehmite particles actually shows soft agglomeration. During the high-speed shear dispersion process, the soft agglomeration is opened. Due to the combined action of shear force and the pulling of PET molecular chains during the shearing process, the soft agglomeration is caused to open, and the molecular chains are prone to entangle with the boehmite particles during this process, thereby strengthening the interaction force between the two.

[0032] Furthermore, the dosage of the silane coupling agent is 0.1 - 0.2 times the mass of the nano-boehmite;

[0033] The dosage of the sodium dodecylbenzenesulfonate is 0.03 - 0.05 times the mass of the nano-boehmite;

[0034] The mass fraction of the ethanol solution is 40 - 60%;

[0035] The dosage of the ethanol solution is 12 - 15 times the mass of the nano-boehmite.

[0036] Furthermore, the silane coupling agent is selected from any one of silane coupling agent KH-540, silane coupling agent KH-550, silane coupling agent KH-560, silane coupling agent KH-570, and silane coupling agent KH-580.

[0037] Furthermore, the specific preparation steps further include:

[0038] Cast and scrape the film-forming solution into shape to obtain a wet film with a thickness of 0.3 - 0.5 mm, and then dry it to constant weight at a temperature of 170 - 180 °C to obtain a dry film;

[0039] Hot-press the dry film at a temperature of 150 - 160 °C and a pressure of 0.3 - 0.5 MPa for 10 - 15 min, and then cool it to obtain a high-toughness PET film.

[0040] Further, the specific preparation steps further include:

[0041] The dried film is continuously hot-pressed for 10 - 15 min under the conditions of a temperature of 150 - 160 °C and a pressure of 0.3 - 0.5 MPa, and then cooled once to obtain a once-hot-pressed film;

[0042] The once-hot-pressed film is continuously hot-pressed for 10 - 15 min under the conditions of a temperature of 100 - 110 °C and a pressure of 0.6 - 0.7 MPa, and then cooled twice to obtain a high-toughness PET film.

[0043] Further, the first cooling is: slowly cooling to 100 - 110 °C at a cooling rate of 0.1 - 0.2 °C / min;

[0044] The second cooling is: quickly cooling to room temperature at a cooling rate of 2 - 4 °C / min.

[0045] A high-toughness PET film is prepared by the above preparation method. Specific Embodiments

[0046] The following specific examples are used to further illustrate the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0047] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0048] Example 1

[0049] Pretreatment of nano-boehmite:

[0050] The nano-boehmite, silane coupling agent, and sodium dodecylbenzenesulfonate are mixed and poured into an ethanol solution. Under the conditions of a temperature of 30 °C and an ultrasonic frequency of 80 kHz, after ultrasonic dispersion for 20 min, a dispersion liquid is obtained. Then the dispersion liquid is transported to a spray dryer and spray-dried under the conditions of an inlet air temperature of 140 °C, an outlet air temperature of 120 °C, a feeding rate of 80 g / min, and a main disk rotation speed of 7000 r / min to obtain pretreated nano-boehmite;

[0051] Among them, the particle size distribution range of the nano-boehmite is 2 - 150 nm, and D50 is 80 nm;

[0052] The dosage of the silane coupling agent is 0.1 times the mass of the nano-boehmite;

[0053] The dosage of the sodium dodecylbenzenesulfonate is 0.03 times the mass of the nano-boehmite;

[0054] The mass fraction of the ethanol solution is 40%;

[0055] The dosage of the ethanol solution is 12 times the mass of the nano-boehmite;

[0056] The silane coupling agent is selected from silane coupling agent KH-540;

[0057] Preparation of the film-forming solution:

[0058] Dissolve the polyethylene terephthalate resin with a solvent to obtain a PET solution with a mass fraction of 10%;

[0059] The solvent consists of the following raw materials by weight fraction:

[0060] 100 parts of phenol, 80 parts of carbon tetrachloride, 2 parts of plasticizer;

[0061] The plasticizer is selected from epoxy soybean oil;

[0062] Add the pretreated nano-boehmite, ethyl acetate and acetone to the PET solution, and shear and disperse evenly under the condition of a shear rate of 6000 r / min to obtain a film-forming solution;

[0063] The dosage of the pretreated nano-boehmite is 10% of the mass of the polyethylene terephthalate resin;

[0064] The dosage of ethyl acetate is 40% of the mass of the nano-boehmite;

[0065] The dosage of acetone is 30% of the mass of the nano-boehmite;

[0066] Casting and blade coating to form a film:

[0067] Cast and blade coat the film-forming solution to obtain a wet film with a thickness of 0.3 mm, and then dry it to constant weight at a temperature of 170 °C to obtain a dry film;

[0068] Heat press the dry film at a temperature of 150 °C and a pressure of 0.3 MPa for 10 min, and cool it once to obtain a once heat-pressed film;

[0069] Heat press the once heat-pressed film at a temperature of 100 °C and a pressure of 0.6 MPa for 10 min, and cool it twice to obtain a high-toughness PET film;

[0070] The first cooling is: slowly cooling down to 100 °C at a cooling rate of 0.1 °C / min;

[0071] The second cooling is: quickly cooling down to room temperature at a cooling rate of 2 °C / min.

[0072] Example 2

[0073] Pretreatment of nano - boehmite:

[0074] Mix nano - boehmite, silane coupling agent and sodium dodecylbenzenesulfonate, and pour them into an ethanol solution. Under the conditions of a temperature of 35 °C and an ultrasonic frequency of 100 kHz, after ultrasonic dispersion for 25 min, a dispersion liquid is obtained. Then, the dispersion liquid is transported to a spray dryer and spray - dried under the conditions of an inlet air temperature of 140 °C, an outlet air temperature of 120 °C, a feeding rate of 80 g / min, and a main disk rotation speed of 7000 r / min, thus obtaining pretreated nano - boehmite;

[0075] Among them, the particle size distribution range of the nano - boehmite is 2 - 150 nm, and D50 is 82 nm;

[0076] The dosage of the silane coupling agent is 0.15 times the mass of the nano - boehmite;

[0077] The dosage of the sodium dodecylbenzenesulfonate is 0.04 times the mass of the nano - boehmite;

[0078] The mass fraction of the ethanol solution is 50%;

[0079] The dosage of the ethanol solution is 14 times the mass of the nano - boehmite;

[0080] The silane coupling agent is selected from silane coupling agent KH - 550;

[0081] Preparation of the film - forming liquid:

[0082] Dissolve polyethylene terephthalate resin with a solvent to obtain a PET solution with a mass fraction of 15%;

[0083] The solvent consists of the following raw materials by weight fraction:

[0084] 110 parts of phenol, 90 parts of carbon tetrachloride, 3 parts of plasticizer;

[0085] The plasticizer is selected from pentaerythritol stearate;

[0086] Add pretreated nano - boehmite, ethyl acetate and acetone to the PET solution, and shear and disperse evenly under the condition of a shear rate of 7000 r / min to obtain a film - forming liquid;

[0087] The dosage of pretreated nano - boehmite is 12% of the mass of polyethylene terephthalate resin;

[0088] The dosage of ethyl acetate is 45% of the mass of nano - boehmite;

[0089] The dosage of acetone is 34% of the mass of nano - boehmite;

[0090] Doctor blade casting film formation:

[0091] The film-forming solution is doctor blade cast into a film to obtain a wet film with a thickness of 0.4 mm, and then dried to a constant weight at a temperature of 175 °C to obtain a dried film;

[0092] The dried film is continuously hot-pressed for 12 min at a temperature of 155 °C and a pressure of 0.4 MPa, and then cooled once to obtain a once hot-pressed film;

[0093] The once hot-pressed film is continuously hot-pressed for 12 min at a temperature of 105 °C and a pressure of 0.65 MPa, and then cooled twice to obtain a high-toughness PET film;

[0094] The first cooling is: slowly cooling to 105 °C at a cooling rate of 0.15 °C / min;

[0095] The second cooling is: quickly cooling to room temperature at a cooling rate of 3 °C / min.

[0096] Example 3

[0097] Pretreatment of nano-boehmite:

[0098] The nano-boehmite, silane coupling agent and sodium dodecylbenzenesulfonate are mixed and poured into an ethanol solution. Under the conditions of a temperature of 45 °C and an ultrasonic frequency of 120 kHz, after ultrasonic dispersion for 30 min, a dispersion is obtained. Then the dispersion is fed into a spray dryer and spray-dried under the conditions of an inlet air temperature of 140 °C, an outlet air temperature of 120 °C, a feeding rate of 80 g / min, and a main disk rotation speed of 7000 r / min to obtain pretreated nano-boehmite;

[0099] Among them, the particle size distribution range of the nano-boehmite is 2 - 150 nm, and D50 is 85 nm;

[0100] The dosage of the silane coupling agent is 0.2 times the mass of the nano-boehmite;

[0101] The dosage of the sodium dodecylbenzenesulfonate is 0.05 times the mass of the nano-boehmite;

[0102] The mass fraction of the ethanol solution is 60%;

[0103] The dosage of the ethanol solution is 15 times the mass of the nano-boehmite;

[0104] The silane coupling agent is selected from silane coupling agent KH-560;

[0105] Preparation of the film-forming solution:

[0106] Dissolve polyethylene terephthalate resin in a solvent to obtain a PET solution with a mass fraction of 20%;

[0107] The solvent consists of the following raw materials by weight fraction:

[0108] 120 parts of phenol, 100 parts of tetrachloromethane, 4 parts of plasticizer;

[0109] The plasticizer is selected from citrate;

[0110] After adding pretreated nano-boehmite, ethyl acetate and acetone to the PET solution, shear and disperse evenly at a shear rate of 8000 r / min to obtain a film-forming solution;

[0111] The dosage of pretreated nano-boehmite is 15% of the mass of polyethylene terephthalate resin;

[0112] The dosage of ethyl acetate is 50% of the mass of nano-boehmite;

[0113] The dosage of acetone is 40% of the mass of nano-boehmite;

[0114] Cast and scrape to form a film:

[0115] Cast and scrape the film-forming solution to form a wet film with a thickness of 0.5 mm, and then dry it to constant weight at a temperature of 180 °C to obtain a dried film;

[0116] Heat press the dried film at a temperature of 160 °C and a pressure of 0.5 MPa for 15 min, and cool it once to obtain a once heat-pressed film;

[0117] Heat press the once heat-pressed film at a temperature of 110 °C and a pressure of 0.7 MPa for 15 min, and cool it twice to obtain a high-toughness PET film;

[0118] The first cooling is: slowly cool down to 110 °C at a cooling rate of 0.2 °C / min;

[0119] The second cooling is: quickly cool down to room temperature at a cooling rate of 4 °C / min.

[0120] Example 4

[0121] The difference between this example and Example 1 is that the nano-boehmite is not pretreated and is directly added to the film-forming solution, and the other conditions remain unchanged.

[0122] Example 5

[0123] The difference between this example and Example 1 is that during the drying process of the pretreated nano-boehmite, conventional oven drying is used instead of spray drying. Specifically:

[0124] Mix nano - boehmite, silane coupling agent and sodium dodecylbenzenesulfonate, pour them into an ethanol solution, and under the conditions of a temperature of 30 °C and an ultrasonic frequency of 80 kHz, after ultrasonic dispersion for 20 min, a dispersion liquid is obtained. Filter the dispersion liquid, collect the filter cake, and transfer the obtained filter cake into an oven, and dry it to a constant weight at a temperature of 100 °C to obtain pretreated nano - boehmite;

[0125] Keep the remaining conditions unchanged.

[0126] Example 6

[0127] Compared with Example 1, the difference in this example is that: the cooling rate of the primary cooling is 2 °C / min, and the remaining conditions remain unchanged.

[0128] Example 7

[0129] Compared with Example 1, the difference in this example is that: the cooling rate of the secondary cooling is 0.1 °C / min, and the remaining conditions remain unchanged.

[0130] Comparative Example 1

[0131] Compared with Example 1, the difference in this comparative example is that:

[0132] Use an equal mass of nano - titanium dioxide to replace nano - boehmite, and keep the remaining conditions unchanged.

[0133] Comparative Example 2

[0134] Compared with Example 1, the difference in this comparative example is that:

[0135] Use an equal mass of nano - aluminum oxide to replace nano - boehmite, and keep the remaining conditions unchanged.

[0136] Comparative Example 3

[0137] Compared with Example 1, the difference in this comparative example is that:

[0138] Do not add ethyl acetate and acetone, and keep the remaining conditions unchanged.

[0139] Perform performance tests on the products obtained from the above examples and comparative examples. The specific test methods and test results are as follows:

[0140] Refer to GB / T 1040.3 - 2006 "Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets" to test the elongation at break of the products;

[0141] Specifically, samples of different embodiments and comparative examples were respectively made into dumbbell-shaped specimens that met the standards. The specimens were clamped in the fixtures of a tensile testing machine to ensure firm clamping and no stress concentration, and were stretched at a rate of 50 mm / min. The stretching process was carried out at room temperature;

[0142] For each product of the embodiments, 10 groups of parallel samples were made according to the above test method, and the average value, as well as the maximum and minimum values, were obtained. The detailed results are shown in Table 1;

[0143] Table 1: Test results of the elongation at break performance of the product

[0144] Average value / % Maximum value / % Minimum value / % Example 1 106.6 110.6 98.7 Example 2 107.2 115.1 100.2 Example 3 108.9 117.7 101.1 Example 4 99.1 107.6 88.1 Example 5 102.1 109.2 93.1 Example 6 100.3 107.9 92.9 Example 7 99.9 105.9 90.8 Comparative Example 1 94.4 101.2 82.2 Comparative Example 2 93.1 99.2 80.1 Comparative Example 3 103.2 112.2 90.1

[0145] It can be seen from the test results in Table 1 that the PET film obtained by the preparation method of the present invention has a relatively higher elongation at break, and during the stretching process of multiple parallel samples, the deviation between the values is also relatively smaller. Thus, it can be seen that the performance consistency of the product is relatively better.

[0146] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a high-toughness PET film, characterized in that: The specific preparation steps include: Dissolving polyethylene terephthalate resin with a solvent to obtain a PET solution with a mass fraction of 10-20%; Adding nano-boehmite, ethyl acetate and acetone to the PET solution and dispersing them evenly to obtain a film-forming solution; After the film-forming liquid is cast and coated, it is dried and hot-pressed to obtain a high-toughness PET film; Wherein, the dosage of nano-boehmite is 10-15% of the mass of polyethylene terephthalate resin; The amount of ethyl acetate used is 40-50% of the mass of the nano-boehmite; The amount of acetone used is 30-40% of the mass of nano-boehmite; The particle size distribution range of nano-boehmite is 2-150nm, and D50 is 80-85nm.

2. The method for preparing a high-toughness PET film according to claim 1, characterized in that: The solvent comprises the following raw material compositions by weight: 100-120 parts of phenol, 80-100 parts of tetrachloromethane, 2-4 parts of plasticizer; The plasticizer is selected from any one of epoxidized soybean oil, pentaerythritol stearate, citrate, and diacetyl monoacylglycerol.

3. The method for preparing a high-toughness PET film according to claim 1, characterized in that: The specific preparation steps also include: The nano-boehmite is pretreated, and the pretreatment step specifically includes: The nano-boehmite, silane coupling agent and sodium dodecylbenzene sulfonate are mixed and poured into an ethanol solution, ultrasonically dispersed uniformly, and then spray-dried to obtain the pretreated nano-boehmite; After adding pretreated nano-boehmite, ethyl acetate and acetone to the PET solution, shearing and dispersing the solution uniformly at a shear rate of 6000-8000 r / min to obtain a film-forming solution; The film-forming liquid is cast and coated, dried, and hot-pressed to obtain a high-toughness PET film.

4. The method for preparing a high-toughness PET film according to claim 3, characterized in that: The amount of the silane coupling agent is 0.1-0.2 times the mass of the nano-boehmite; The amount of sodium dodecylbenzene sulfonate used is 0.03-0.05 times the mass of the nano-boehmite; The mass fraction of the ethanol solution is 40-60%; The amount of the ethanol solution used is 12-15 times the mass of the nano-boehmite.

5. The method for preparing a high-toughness PET film according to any one of claims 3 or 4, characterized in that: The silane coupling agent is selected from any one of silane coupling agent KH-540, silane coupling agent KH-550, silane coupling agent KH-560, silane coupling agent KH-570 and silane coupling agent KH-580.

6. The method for preparing a high-toughness PET film according to claim 1, characterized in that: The specific preparation steps also include: The film-forming liquid is cast and coated to obtain a wet film with a thickness of 0.3-0.5 mm, and then dried to a constant weight at a temperature of 170-180° C. to obtain a dry film; The dried film is subjected to hot pressing for 10-15 minutes at a temperature of 150-160°C and a pressure of 0.3-0.5 MPa, and then cooled to obtain a high-toughness PET film.

7. The method for preparing a high-toughness PET film according to claim 6, characterized in that: The specific preparation steps also include: The dried film is subjected to continuous hot pressing for 10-15 minutes at a temperature of 150-160°C and a pressure of 0.3-0.5 MPa, and cooled once to obtain a hot pressed film; The primary hot pressing film is subjected to a temperature of 100-110°C and a pressure of 0.6-0.7 MPa for 10-15 minutes, and then cooled for a secondary time to obtain a high-toughness PET film.

8. The method for preparing a high-toughness PET film according to claim 7, characterized in that: The primary cooling is: slowly cooling to 100-110°C at a cooling rate of 0.1-0.2°C / min; The secondary cooling is: rapidly cooling to room temperature at a cooling rate of 2-4°C / min.

9. A high-toughness PET film, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.