PET multilayer blister film and preparation method thereof

Abstract

The invention belongs to the field of plastic uptake composite film materials, and particularly relates to a PET multilayer plastic uptake film and a preparation method thereof. The composite material at least comprises a layer A, a layer B and a layer C. The layer A and the layer C are compounded through the layer B; the layer A and the layer C are prepared from the following raw materials in parts by weight: 60-80 parts of modified PETG, 10-20 parts of modified PET, 3-4 parts of an ultraviolet light absorber, 0.5-2 parts of a hindered amine light stabilizer, 0.5-1 part of an antioxidant, 5-10 parts of an auxiliary agent and 1-2 parts of a coupling agent; and the layer B is prepared from the following raw materials in parts by weight: 40-60 parts of modified PETG, 30-50 parts of modified PET and 10-20 parts of a toughening agent. According to the invention, the self-made polyester type liquid crystal polymer flexibilizer is cooperated with other auxiliary agents in the system, and the crystallinity is controlled through a specific gradient cooling process, so that the prepared PET multilayer blister film has better mechanical properties and excellent transparency, weather resistance and chemical resistance.

Description

Technical Field

[0001] The invention belongs to the field of blister composite film materials, and particularly relates to a PET multi-layer blister film and a preparation method thereof. Background Art

[0002] Blister film is a plastic film made through a blister process. The process involves heating a flat, rigid plastic sheet to soften it, applying vacuum to a mold, and then cooling it to form the film. This process allows the film to conform to various shapes, providing excellent packaging and protection. Blister film is made from a variety of raw materials, including polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyethylene (PE), and polystyrene (PS).

[0003] Traditional blister films (such as PVC, PET, etc.) are prone to embrittlement, yellowing, surface cracking or performance degradation when exposed to ultraviolet rays, high temperature, humidity or chemical corrosion environments for a long time, resulting in a short service life. This is because the existing blister films are insufficient in weather resistance and cannot effectively resist the erosion of factors such as ultraviolet rays and oxidation. Chinese invention patent CN117962448B provides a kind of UV-resistant PET composite film and its application in lighting tiles. Although the ultraviolet absorption performance is improved by adding auxiliary agents, it is difficult to take into account the synergistic improvement of toughness, weather resistance and chemical resistance, and the process is complicated and the cost is high. In addition, the existing blister films are prone to fracture during the secondary processing stretching process, which will limit the application of blister films on some complex-shaped products, because during the blister forming process, the blister film needs to withstand a certain tensile force. If the tensile strength is not enough, it is easy to break or deform.

[0004] In industries such as furniture, automobiles, and electronics, consumers demand not only good appearance but also high durability and reliability. However, existing blister films cannot fully meet these market demands in terms of high toughness, high weather resistance, and chemical resistance. Summary of the Invention

[0005] In response to the problems in the prior art, the first aspect of the present invention provides a PET multilayer blister film, comprising at least a layer A, a layer B, and a layer C, wherein the layer A and the layer C are composited via the layer B. The raw materials for preparing the layers A and C respectively comprise, by weight, 60-80 parts of modified PETG, 10-20 parts of modified PET, 3-4 parts of an ultraviolet absorber, 0.5-2 parts of a hindered amine light stabilizer, 0.5-1 part of an antioxidant, 5-10 parts of an auxiliary agent, and 1-2 parts of a coupling agent. The raw materials for preparing the layer B comprise 40-60 parts of modified PETG, 30-50 parts of modified PET, and 10-20 parts of a toughening agent.

[0006] In one embodiment, the thickness ratio of the layer A to the layer C and the layer B is (50-60):(40-60), which can be 60:40, 50:50, or 50:60.

[0007] In one embodiment, the brand of the modified PETG is selected from one or more of YH101, YH201, YH103, WS501, and SK2012.

[0008] In one embodiment, the brand of the modified PET is selected from one or more of YH600, BG80, BG85, FG600, and FG620.

[0009] In one embodiment, the ultraviolet absorber is a benzotriazole ultraviolet absorber, and the brand of the benzotriazole ultraviolet absorber is selected from one or more of UV-531, UV-571, UV-329, and UV-360.

[0010] In one embodiment, the antioxidant is a phosphite antioxidant, and the brand of the phosphite antioxidant is Irgafos 168.

[0011] In one embodiment, the auxiliary agent includes at least one of nano-silica and fluorinated polymer.

[0012] In one embodiment, the fluorinated polymer is selected from one or more of PTFE, ETFE, FEP, PVDF, PFA, and fluorinated acrylate.

[0013] In one embodiment, the toughening agent comprises a polyester liquid crystal polymer.

[0014] In one embodiment, the raw materials for preparing the polyester liquid crystal polymer include, by mole parts, 30-40 mole parts of hydroxy polyester, 40-50 mole parts of aromatic compound, 2-8 mole parts of acylating agent and 2-8 mole parts of catalyst.

[0015] In one embodiment, the raw materials for preparing the polyester liquid crystal polymer include, by mole parts, 36 mole parts of hydroxy polyester, 45 mole parts of aromatic compound, 5 mole parts of acylating agent and 5 mole parts of catalyst.

[0016] In one embodiment, the hydroxy polyester includes at least one of p-hydroxybenzoic acid and hydroxy acrylic acid modified polyester resin.

[0017] In one embodiment, the hydroxy polyester is p-hydroxybenzoic acid.

[0018] In one embodiment, the aromatic compound includes at least one of 6-hydroxy-2-naphthoic acid and 3-hydroxy-2-naphthoic acid.

[0019] In one embodiment, the aromatic compound is 6-hydroxy-2-naphthoic acid.

[0020] In one embodiment, the catalyst includes at least one of a polyester polymerization catalyst and an acetate catalyst.

[0021] In one embodiment, the catalyst is a polyester polymerization catalyst. The polyester polymerization catalyst includes at least one of antimony trioxide and tetrabutyl titanate.

[0022] In one embodiment, the catalyst is an acetate catalyst.

[0023] In one embodiment, the acetate catalyst includes at least one of zinc acetate, sodium acetate, magnesium acetate, and zinc acetate.

[0024] In one embodiment, the acetate catalyst is sodium acetate.

[0025] In one embodiment, the acylating agent comprises acetic anhydride.

[0026] In one embodiment, the polyester polymerization catalyst accounts for 1-2% of the mass of the acetylated monomer.

[0027] In one embodiment, the method for preparing the polyester liquid crystal polymer comprises at least the following steps:

[0028] S1, heating the hydroxy polyester, aromatic compound and acylating agent to 115°C and reacting for 1.5 hours to generate an acetylated monomer;

[0029] S2. Inert gas was introduced into the reactor, the acetylated monomer and the catalyst were added, and the temperature was slowly raised to 170° C. for prepolymerization; the temperature was further raised to 280° C. for 3.5 hours for polycondensation to obtain reaction product A;

[0030] S3. Using a rotary evaporator to evacuate, heating the reaction product A at 95° C. for 0.5-1 h and then cooling to room temperature to obtain a solid polymer, and crushing the solid polymer into particles or powder to obtain a polyester liquid crystal polymer.

[0031] In one embodiment, the prepolymerization reaction time is 1-1.5 hours.

[0032] In one embodiment, the rotary evaporator is evacuated to a pressure of less than 1 mmHg.

[0033] A second aspect of the present invention provides a method for preparing a PET multilayer blister film, comprising the following steps:

[0034] a. Dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix A; dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix C;

[0035] b. Dry-mixing the modified PETG, modified PET and toughening agent in a high-speed mixer, and drying to obtain premix B;

[0036] c. feeding premix A, premix B and premix C into a screw extruder respectively, and after plasticization, melting and extrusion, vacuuming and filtering, melts A, B and C are obtained. The melts A, B and C are subjected to three-layer composite extrusion molding, and then cooled by a chill roller to obtain a cast sheet;

[0037] d. The cast sheet is sequentially stretched longitudinally and transversely through guide rollers to obtain the PET multilayer blister film.

[0038] In one embodiment, the surface modification conditions in step a are: reaction at 60-80° C. for 40-60 min.

[0039] In one embodiment, the extrusion temperature of the three-layer composite extrusion molding in step c is 240-280° C., the temperature of the chill roll is 25-40° C., and the rotation speed is 80-100 m / min.

[0040] In one embodiment, the moisture contents of melts A, B and C in step c are all ≤50 ppm.

[0041] In one embodiment, the extrusion mass ratio of melts A, B and C in step c is 0.75:1:0.75.

[0042] In one embodiment, the heat treatment zone length for longitudinal stretching in step d is 8-15 m, the temperature of the preheating zone is 60-90° C., the time is 10-20 s, and the stretching ratio is 1-1.1 times.

[0043] In one embodiment, the transverse stretching in step d is divided into a preheating zone, a stretching zone, a heat setting zone and a cooling zone; the cooling zone adopts a gradient cooling process, the fan power of the cooling zone 1 is 60-70%, the fan power of the cooling zone 2 is 70-80%, and the fan power of the cooling zone 3 is 80-90%, the cooling rate is 15°C / min, and the stretching ratio is 2.0-4.5 times.

[0044] In one embodiment, in the transverse stretching step d, the preheating temperature is 100-120°C, the stretching temperature is 70-90°C, and the heat setting temperature is 80-90°C.

[0045] Beneficial effects

[0046] 1. The present invention uses a homemade polyester liquid crystal polymer toughening agent that has good compatibility with PET and PETG, and forms a uniformly dispersed fiber phase through blending and modification. This uniformly dispersed fiber phase forms a physical cross-linked network between molecular chains, which can improve the crystallization and mechanical properties of the material, increase tensile strength and impact strength, and cooperate with other additives in the system to prepare a blister film with high toughness, good weather resistance and chemical resistance.

[0047] 2. The method for preparing a PET multilayer blister film provided by the present invention controls crystallinity through a specific gradient cooling process, avoiding the brittle defects caused by traditional rapid cooling. The temperature gradient not only affects the crystallization behavior but also has a significant impact on the final performance of the material. By optimizing the temperature gradient, the crystallization uniformity of the material can be improved, thereby enhancing its mechanical properties and durability.

[0048] 3. The present invention controls the moisture content of melts A, B and C to be ≤50 ppm. On the one hand, it can avoid the generation of defects such as bubbles and pinholes on the surface or inside the film during the preparation of the blister film; on the other hand, by controlling the moisture content, it can ensure the mechanical properties of the film such as tensile strength and elongation at break, as well as the processing stability during the extrusion or blow molding process.

[0049] 4. The preparation process of the PET multi-layer blister film provided by the present invention is simple to operate and easy to control the thickness, which can effectively reduce production and product costs. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The experimental methods for which specific conditions are not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used for which the manufacturer is not specified are all conventional products that can be purchased commercially.

[0051] Example 1

[0052] A first aspect of this embodiment provides a PET multilayer blister film, comprising a layer A, a layer B, and a layer C, wherein layer A and layer C are compounded via layer B; the raw materials for preparing layers A and C each comprise, by weight, 80 parts of modified PETG, 10 parts of modified PET, 3 parts of an ultraviolet absorber, 0.5 parts of a hindered amine light stabilizer, 0.5 parts of an antioxidant, 6 parts of an auxiliary agent, and 2 parts of a coupling agent; the raw materials for preparing layer B comprise 60 parts of modified PETG, 30 parts of modified PET, and 10 parts of a toughening agent.

[0053] The thickness ratio of the A layer to the C layer and to the B layer is 60:40.

[0054] The modified PETG is of the brand YH101, purchased from Henan Yuanhong Polymer New Materials Co., Ltd.

[0055] The modified PET is of the brand YH600, purchased from Henan Yuanhong Polymer New Materials Co., Ltd.

[0056] The modified UV absorber is a benzotriazole UV absorber, which is UV-571 and purchased from Fujian Disheng Technology Co., Ltd.

[0057] The antioxidant is a phosphite antioxidant. The phosphite antioxidant is Irgafos 168, purchased from BASF.

[0058] The auxiliary agent is nano-silicon dioxide, purchased from Jiangsu Tianxing New Materials Co., Ltd.

[0059] The toughening agent is a polyester liquid crystal polymer, and the raw materials for preparing the polyester liquid crystal polymer include: 36 parts by mole of hydroxy polyester, 45 parts by mole of aromatic compound, 5 parts by mole of acylating agent and 5 parts by mole of catalyst.

[0060] The hydroxy polyester is p-hydroxybenzoic acid, and the p-hydroxybenzoic acid comes from Shanghai Lianzu Biotechnology Co., Ltd.

[0061] The aromatic compound is 6-hydroxy-2-naphthoic acid, and the 6-hydroxy-2-naphthoic acid comes from Weihai Ziteng Biotechnology Co., Ltd.

[0062] The acylating agent is acetic anhydride, and the acetic anhydride is from Zhejiang Ningbo Wanglong Technology Co., Ltd.

[0063] The catalyst is sodium acetate, which comes from Suzhou Xinshengyuan Chemical Technology Co., Ltd.

[0064] The preparation method of the polyester liquid crystal polymer comprises the following steps:

[0065] S1, heating the hydroxy polyester, aromatic compound and acylating agent to 115°C and reacting for 1.5 hours to generate an acetylated monomer;

[0066] S2. Inert nitrogen gas was introduced into the reactor, the acetylated monomer and the catalyst were added, and the temperature was slowly raised to 170° C. for a prepolymerization reaction for 1 hour; the temperature was further raised to 280° C. for a condensation reaction for 3.5 hours to obtain a reaction product A;

[0067] S3. Using a rotary evaporator to evacuate, heating the reaction product A at 95° C. for 1 h and then cooling it to room temperature to obtain a solid polymer, and crushing the solid polymer into powder to obtain a polyester liquid crystal polymer.

[0068] A second aspect of this embodiment provides a method for preparing a PET multilayer blister film, comprising the following steps:

[0069] a. Dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix A; dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix C;

[0070] b. Dry-mixing the modified PETG, modified PET and toughening agent in a high-speed mixer, and drying to obtain premix B;

[0071] c. Premix A, premix B, and premix C are respectively fed into a screw extruder, and after plasticization, melting, and extrusion, vacuuming, and filtering, melts A, B, and C are obtained. The melts A, B, and C are subjected to three-layer composite extrusion molding at an extrusion temperature of 260° C., and then cooled by a chill roll at a temperature of 30° C. and a rotation speed of 90 m / min to obtain a cast sheet;

[0072] d. The cast sheet is sequentially stretched longitudinally and transversely through guide rollers to obtain the PET multilayer blister film.

[0073] The surface modification conditions in step a are: reaction at 70° C. for 50 min.

[0074] In the step c, the moisture contents of melts A, B and C are all ≤50 ppm.

[0075] In the step c, the extrusion mass ratio of melts A, B and C is 0.75:1:0.75.

[0076] The heat treatment zone length for longitudinal stretching in step d is 10 m, the temperature of the preheating zone is 80° C., the time is 15 s, and the longitudinal stretching ratio is 1.1 times.

[0077] The transverse stretching in step d is divided into a preheating zone, a stretching zone, a heat setting zone and a cooling zone; the preheating temperature is 105°C, the stretching temperature is 80°C, and the heat setting temperature is 85°C.

[0078] The cooling zone adopts a gradient cooling process, the fan power of the cooling zone 1 is 65%, the fan power of the cooling zone 2 is 75%, the fan power of the cooling zone 3 is 85%, the cooling rate is 15°C / min, and the transverse stretching ratio is 2.5 times.

[0079] The thickness of the PET multi-layer blister film is 50 μm.

[0080] Example 2

[0081] The specific implementation of this embodiment is the same as that of Example 1, except that the nano-silica is replaced by fluorinated acrylate, which is perfluorohexylethyl acrylate purchased from Zhejiang Juhua Co., Ltd.

[0082] Comparative Example 1

[0083] The specific implementation manner of this comparative example is the same as that of Example 1, except that, in parts by weight, the raw materials for preparing the A layer and the C layer both include: 70 parts of modified PETG, 20 parts of modified PET, 1 part of ultraviolet absorber, 0.5 parts of hindered amine light stabilizer, 0.5 parts of antioxidant, 8 parts of auxiliary agent and 2 parts of coupling agent.

[0084] The raw materials for preparing the B layer include: 40 parts of modified PETG, 50 parts of modified PET and 10 parts of toughening agent.

[0085] Comparative Example 2

[0086] The specific implementation of this comparative example is the same as that of Example 1, except that, in parts by weight, the raw materials for preparing the A layer and the C layer both include: 80 parts of modified PETG, 10 parts of modified PET, 3 parts of ultraviolet absorber, 2 parts of hindered amine light stabilizer, 0.5 parts of antioxidant, 1 part of auxiliary agent and 2 parts of coupling agent;

[0087] The raw materials for preparing the B layer include: 60 parts of modified PETG, 30 parts of modified PET and 10 parts of toughening agent.

[0088] Comparative Example 3

[0089] The specific implementation of this comparative example is the same as that of Example 1, except that, based on weight percentage, the raw materials for preparing the B layer include: 60 parts of modified PETG, 35 parts of modified PET and 5 parts of toughening agent.

[0090] Comparative Example 4

[0091] The specific implementation of this comparative example is the same as that of Example 1, except that the toughening agent is methyl methacrylate-butadiene-styrene copolymer. The brand of the methyl methacrylate-butadiene-styrene copolymer is EM500, purchased from LG Corporation.

[0092] Comparative Example 5

[0093] The specific implementation of this comparative example is the same as that of Example 1, except that the raw materials for preparing the A layer and the C layer do not contain ultraviolet absorbers, antioxidants and additives; and the raw materials for preparing the B layer do not contain toughening agents.

[0094] Comparative Example 6

[0095] The specific implementation of this comparative example is the same as that of Example 1, except that the raw materials for preparing the A layer and the C layer do not contain an ultraviolet absorber.

[0096] Comparative Example 7

[0097] The specific implementation of this comparative example is the same as that of Example 1, except that the UV absorber in the raw materials for preparing the layers A and C is a benzophenone-based UV absorber, which is BP-2 and purchased from BASF.

[0098] Comparative Example 8

[0099] The specific implementation of this comparative example is the same as that of Example 1, except that the raw materials for preparing the A layer and the C layer do not contain auxiliary agents.

[0100] Comparative Example 9

[0101] The specific implementation of this comparative example is the same as that of Example 1, except that the auxiliary agent in the raw materials for preparing layers A and C is a silane coupling agent. The silane coupling agent is γ-aminopropyltriethoxysilane, the brand of which is BP-550, purchased from Dongguan Huiyi Chemical Materials Co., Ltd.

[0102] Comparative Example 10

[0103] The specific implementation of this comparative example is the same as that of Example 1, except that the raw materials for preparing the B layer do not contain a toughening agent.

[0104] Comparative Example 11

[0105] The specific implementation of this comparative example is the same as that of Example 1, except that the toughening agent is a styrene-ethylene-butylene block copolymer. The model of the styrene-ethylene-butylene block copolymer is SEBS, which is purchased from Dongguan Changhe Chemical.

[0106] Comparative Example 12

[0107] The specific implementation of this comparative example is the same as that of Example 1, except that the fan powers of the cooling zone 1, the cooling zone 2 and the cooling zone 3 in the transverse stretching cooling zone are all 75%.

[0108] Performance Testing

[0109] Sample: PET multilayer blister film prepared in each embodiment and comparative example.

[0110] 1. Tensile strength and elongation at break: According to the provisions of GB / T13022-1991 Test method for tensile properties of plastic films, the specimen is a strip with a length of 150 mm and a width of (15 ± 0.1) mm. The distance between the fixtures is 100 mm and the test speed is (250 ± 25) mm / min.

[0111] 2. Light transmittance and haze: Test in accordance with GB / T 2410-2008 Test method for light transmittance and haze of transparent plastics;

[0112] 3. Weathering resistance testing: Test according to ASTM G154, Practice for Accelerated Exposure of Nonmetallic Materials in Artificial Weathering. Specimens should be standard size 75 x 150 mm. Ensure the sample surface is clean and free of contamination. Set the sample surface temperature to 60°C and the condensation temperature to 50°C. Place the sample in a QUV weathering chamber equipped with a UVA-340 light source for 1000 hours, and run the test according to the specified parameters. Regularly check the sample status and record the data during the test. Evaluate weathering resistance by observing color change, strength loss, and other indicators. The yellowing index test method is divided into the following categories according to the yellowing degree △Yi: Level 0: no discoloration, △Yi≤1.5; Level 1: very slight discoloration, 1.6<△Yi≤3.0; Level 2: slight discoloration, 3.1<△Yi≤6.0; Level 3: obvious discoloration, 6.1<△Yi≤9.0; Level 4: larger discoloration, 9.1<△Yi≤12.0; Level 5: severe discoloration, 12.0<△Yi.

[0113] 4. Chemical Resistance Testing: Refer to the requirements of GB / T 13542.4-2009 Electrical Insulation Film. Samples are taken at regular intervals (300mm) from the film roll to ensure they are free of defects. Butyl acetate is used for solvent resistance testing. Testing includes appearance inspection, thickness measurement, tensile strength testing, and gas permeability testing.

[0114] The test results are detailed in Table 1 and Table 2:

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120]

[0121] As shown in the table, the PET multilayer blister film prepared in the present application has a synergistic improvement in toughness, weather resistance and chemical resistance compared to the comparative example, has better mechanical properties and excellent transparency, weather resistance and chemical resistance, and has good application prospects in the blister field.

Claims

1. A PET multilayer blister film, characterized in that: The invention comprises at least a layer A, a layer B and a layer C, wherein the layer A and the layer C are compounded via the layer B. The raw materials for preparing the layers A and C respectively comprise, by weight, 60-80 parts of modified PETG, 10-20 parts of modified PET, 3-4 parts of ultraviolet absorber, 0.5-2 parts of hindered amine light stabilizer, 0.5-1 part of antioxidant, 5-10 parts of auxiliary agent and 1-2 parts of coupling agent. The raw materials for preparing the layer B comprise 40-60 parts of modified PETG, 30-50 parts of modified PET and 10-20 parts of toughening agent.

2. The PET multilayer blister film according to claim 1, wherein The ultraviolet absorber is a benzotriazole ultraviolet absorber.

3. The PET multilayer blister film according to claim 1, wherein The toughening agent includes a polyester liquid crystal polymer.

4. The PET multilayer blister film according to claim 3, wherein Calculated by molar parts, the raw materials for preparing the polyester liquid crystal polymer include: 30-40 molar parts of hydroxy polyester, 40-50 molar parts of aromatic compound, 2-8 molar parts of acylating agent and 2-8 molar parts of catalyst.

5. The PET multilayer blister film according to claim 4, characterized in that: The preparation method of the polyester liquid crystal polymer comprises at least the following steps: S1, heating the hydroxy polyester, aromatic compound and acylating agent to 115°C and reacting for 1.5 hours to generate an acetylated monomer; S2. Inert gas was introduced into the reactor, the acetylated monomer and the catalyst were added, and the temperature was raised to 170° C. for prepolymerization; the temperature was further raised to 280° C. for 3.5 hours for polycondensation to obtain reaction product A; S3. Using a rotary evaporator to evacuate, heat the reaction product A at 95° C. for 0.5-1 h and then cool to room temperature to obtain a solid polymer, and crush the solid polymer into particles or powder to obtain a polyester liquid crystal polymer.

6. The PET multilayer blister film according to claim 1, characterized in that: The auxiliary agent includes at least one of nano silicon dioxide and fluorinated polymer.

7. A method for preparing a PET multilayer blister film according to any one of claims 1 to 6, characterized in that: The following steps are involved: a. Dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix A; dry-mixing modified PETG, modified PET, an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, and an additive in a high-speed mixer, adding a coupling agent for surface modification, and drying to obtain premix C; b. Dry-mixing the modified PETG, modified PET and toughening agent in a high-speed mixer, and drying to obtain premix B; c. feeding premix A, premix B and premix C into a screw extruder respectively, and after plasticization, melting and extrusion, vacuum filtration is performed to obtain melts A, B and C, and the melts A, B and C are subjected to three-layer composite extrusion molding, and then cooled by a chill roller to obtain a cast sheet; d. The cast sheet is sequentially stretched longitudinally and transversely through guide rollers to obtain the PET multilayer blister film.

8. The method for preparing the PET multilayer blister film according to claim 7, wherein: In the step c, the extrusion temperature of the three-layer composite extrusion molding is 240-280° C., the temperature of the chill roller is 25-40° C., and the rotation speed is 80-100 m / min.

9. The method for preparing a PET multilayer blister film according to claim 7, wherein: The heat treatment zone length of the longitudinal stretching in step d is 8-15 m, the temperature of the preheating zone is 60-90° C., the time is 10-20 s, and the stretching ratio is 1-1.1 times.

10. The method for preparing the PET multi-layer blister film according to claim 7, wherein: In the step d, the transverse stretching is divided into a preheating zone, a stretching zone, a heat setting zone and a cooling zone; the cooling zone adopts a gradient cooling process, the fan power of the cooling zone 1 is 60-70%, the fan power of the cooling zone 2 is 70-80%, the fan power of the cooling zone 3 is 80-90%, and the cooling rate is 15°C / min.

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