PETG / PET co-extrusion self-heat-sealing multilayer film and preparation method thereof

Abstract

The invention discloses a PETG / PET co-extrusion self-heat-sealing multilayer film and a preparation method thereof. The PETG / PET co-extrusion self-heat-sealing multilayer film comprises an outer layer, a gas barrier layer arranged at the bottom of the outer layer, a polymer middle layer arranged at the bottom of the gas barrier layer, a self-heat reaction layer arranged at the bottom of the polymer middle layer, and a base layer arranged at the bottom of the self-heat reaction layer. According to the PETG / PET co-extrusion self-heat-sealing multilayer film and the preparation method thereof, heat can be generated through physical stimulation under the condition that no external heat source exists, the sealing process is simplified, and packaging convenience is improved; compared with a traditional sealing mode needing an external heat source, energy consumption can be reduced through the self-heating technology, the modern environment-friendly requirement is met, the film is excellent in heat sealing performance and firm in sealing, has high tensile strength and impact resistance and can adapt to different packaging requirements, the functionality and stability of the film are effectively improved through the co-extrusion multi-layer structure, and the service life of the film is prolonged. Meanwhile, due to the combination of all the layers of materials, the film is excellent in heat sealing performance, impact resistance, transparency and the like.

Description

Technical Field

[0001] The invention relates to the technical field of heat-sealing multilayer film preparation, in particular to a PETG / PET co-extruded self-heat-sealing multilayer film and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) is a common thermoplastic resin. It is a milky white or light yellow highly crystalline polymer with a smooth and glossy surface and a density of 1.30 to 1.38 g / cm 3 , melting point is 255-260℃, difficult to burn, ignition point is 480℃, cracking temperature is 420℃. PET has good mechanical and optical properties, high tensile strength, good rigidity, resistance to stretching and bending, high dimensional stability, glossiness and transparency, and good barrier properties to gases (oxygen and carbon dioxide) and water vapor. It is often used to package food, distilled alcohol, carbonated beverages, non-carbonated beverages and cosmetics. In addition, PET has good wear resistance, weather resistance, creep resistance and abrasion resistance, and good acid and solvent resistance. However, PET has a narrow processing range, a large water absorption rate, and a decrease in characteristic viscosity after moisture absorption. Silver spots and bubbles will appear on the surface of the film after molding. In addition, PET has a low dielectric constant and poor conductivity.

[0003] A new type of copolyester made by copolymerizing three monomers: dimethyl ester (DMT), ethylene glycol (EG), and 1,4-cyclohexanedimethanol (CHDM). Compared with traditional PET, part of the glycol EG in the synthesis process of the new copolyester PETG is replaced by CHDM. When the CHDM content is less than 50% of the total amount of glycol, the copolyester is PETG. Due to the extremely low crystallinity of PETG or even no crystallization, its transparency is extremely high, and the toughness of PETG is also extremely excellent. The elongation at break of the industrialized PETG product of Eastman in the United States can reach about 300%, which is much higher than PET. PETG also has very good chemical resistance and is resistant to corrosion by dilute acids and alkalis. At the same time, PETG is resistant to γ-ray irradiation, does not change color after γ-ray irradiation, and can still maintain high transparency and stability. PETG film also has high barrier properties to gases (oxygen and carbon dioxide), and is suitable for packaging products with high requirements for gas barrier properties. The main application of PETG in film is to make high shrinkage film. The shrinkage rate of ordinary PET is about 30%, while the shrinkage rate of PETG film can reach 70%. It has the advantages of high plastic suction force, high transparency, high gloss, low haze, easy printing, not easy to fall off, and low natural shrinkage during storage. Among them, the biaxially stretched PETG film is suitable for high-end packaging, printing, electronic appliances, cable wrapping, insulation materials and high-quality substrates in various industrial fields. Uniaxially stretched PET heat shrinkable film is suitable for external labels of various cans, polyester bottles, various containers, etc.

[0004] Multi-layer co-extruded composite film is a new type of packaging material. It can make up for the performance defects of single-layer plastic film, give full play to the strengths of each layer of material, achieve the purpose of making up for each other's weaknesses, and has better comprehensive performance and outstanding certain packaging characteristics. It is one of the most ideal film materials that currently meet the special requirements of packaging contents.

[0005] The prior art has the following defects or problems: The prior art has a publication number of CN112848580B, a PETG / PET co-extruded self-heat-sealing multilayer film and a preparation method thereof, which comprises five film layers, including a base layer 1, an adhesive layer 1, a barrier layer, an adhesive layer 2 and a base layer 2 in sequence; wherein the base layer 1 is a heat-sealing layer, comprising metallocene PE and PETG; the base layer 2 is a lower surface layer, comprising PET, an anti-blocking agent and a slip agent; the adhesive layer 1 and the adhesive layer 2 have the same components, comprising maleic anhydride grafted polypropylene, PETG and nano-carbon fibers; the barrier layer is an intermediate layer, comprising PA and PETG;

[0006] The film composed of the above components cannot generate heat through physical stimulation, the heat sealing process is cumbersome, the packaging is not convenient enough, and the tensile strength and impact resistance cannot meet the packaging requirements.

[0007] It should be noted that the above contents belong to the technical knowledge of the inventor and do not necessarily constitute prior art. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a PETG / PET co-extruded self-heat-sealing multilayer film and a preparation method thereof, which solve the existing problems.

[0009] To achieve the above object, the present invention provides the following technical solution: a PETG / PET co-extruded self-heat-sealing multilayer film, comprising:

[0010] The outer layer has a gas barrier layer at the bottom, a polymer middle layer is arranged at the bottom of the gas barrier layer, the polymer middle layer is made of polyamide, a self-heating reaction layer is arranged at the bottom of the polymer middle layer, the self-heating reaction layer is composed of a mixture of iron powder and salt compounds, and a base layer is arranged at the bottom of the self-heating reaction layer.

[0011] As a preferred technical solution of the present invention, the outer layer is made of polyethylene terephthalate material and the outer surface is sprayed with a polyether antistatic agent, and the thickness of the outer layer needs to be controlled within 12-30 microns.

[0012] As a preferred technical solution of the present invention, the base layer is specifically made by co-extruding polyethylene terephthalate and polybutadiene materials in a mixing ratio of 1:0.08, and the thickness of the base layer needs to be controlled within 10-25 microns.

[0013] As a preferred technical solution of the present invention, the gas barrier layer is specifically made of ethylene-vinyl alcohol copolymer, and the thickness is controlled to be 10-50 microns.

[0014] Another technical problem to be solved by the present invention is to provide a method for preparing a PETG / PET co-extruded self-heat-sealing multilayer film, comprising the following steps:

[0015] Step 1: Pre-treat each raw material particle to remove impurities, moisture and air inside it;

[0016] Step 2: Send the processed raw material particles into the barrel of the extruder through a conveying pipe;

[0017] Step 3: The extruder pushes the raw material forward through the rotating motion of the screw. With the help of the shearing action of the screw, the raw material particles are heated to a molten state. The extruder has multiple sets of heating zones built in, and the temperature of each heating zone is different;

[0018] Step 4: The molten fluids of different raw materials are extruded through the flow channel of the die head and stacked together at the die head outlet. During the co-extrusion process, the material flow rate of each flow channel needs to be strictly controlled to ensure that the proportion and thickness of each layer of material meet the requirements;

[0019] Step 5: The coextruded molten film enters the cooling zone, and the film is blown out of the mouth film by air to form an airbag shape. The film blowing will further stretch the film, and due to the push of the gas, the thickness of the film will gradually become uniform;

[0020] Step 6: The blown molten film passes through the cooling zone to achieve qualitative control, quickly reducing the temperature of the film so that the film can solidify and maintain a stable shape;

[0021] Step 7: heat-treating the molten film to further shape it;

[0022] Step 8: During the co-extrusion process, use a film thickness measuring instrument to monitor the film thickness online to ensure that the thickness of each layer of the film is uniform, and test the film's transparency, appearance, tensile strength, elongation at break, heat sealing performance, and air permeability;

[0023] Step nine: After the surface of the tested film is coated with a polyether antistatic agent, it is then rolled into a film roll by a winder.

[0024] Furthermore, the raw material particle pretreatment includes:

[0025] Rinse the raw material particles to remove dirt from the surface of each raw material particle;

[0026] Place the cleaned raw material particles into the drum and use hot air drying equipment to dry the moisture inside the particles;

[0027] The dried raw material particles are placed in a vacuum environment to remove the gas impurities remaining inside.

[0028] Furthermore, the temperature of the internal heating zone of the extruder can be divided into 4 zones, wherein the temperature of the melting zone during the preparation of the outer layer and the base layer needs to be controlled at 260-290 degrees Celsius;

[0029] During the preparation of the gas barrier layer, the temperature of the melting area needs to be controlled at 150-200 degrees Celsius;

[0030] During the preparation of the polymer intermediate layer, the temperature of the melting zone needs to be controlled at 220-240 degrees Celsius;

[0031] During the preparation of the self-heating reaction layer, the temperature of the melting zone needs to be controlled at 150-180 degrees Celsius.

[0032] Furthermore, the co-extrusion die has multiple flow channels, each flow channel corresponds to an extruder, which is used to introduce molten fluids of different raw materials into the die and merge them through the die outlet. The extrusion pressure of the extruder needs to be controlled at 1500-2200 bar, and the die temperature is controlled at 250-300 degrees Celsius.

[0033] Furthermore, the film blowing ratio needs to be controlled at 1:3-6, the stretching rate is controlled at 10-30 m / min, the gas pressure is controlled at 1.5-2.5 bar, and the cooling water temperature is maintained at 15-25 degrees Celsius.

[0034] Compared with the prior art, the present invention provides a PETG / PET co-extruded self-heat-sealing multilayer film and a preparation method thereof, which has the following beneficial effects:

[0035] The PETG / PET co-extruded self-heat-sealing multilayer film and the preparation method thereof can generate heat through physical stimulation without an external heat source, thereby simplifying the sealing process and increasing the convenience of packaging. Compared with the traditional sealing method requiring an external heat source, the use of the self-heating technology can reduce energy consumption and meet modern environmental protection requirements. The film has excellent heat-sealing performance, firm sealing, high tensile strength and impact resistance, and can adapt to different packaging requirements. The co-extruded multilayer structure effectively improves the functionality and stability of the film. At the same time, the combination of the materials of each layer makes the film excellent in heat sealing, impact resistance, transparency and other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of a PETG / PET co-extruded self-heat-sealing multilayer film of the present invention.

[0037] In the figure: 1. Outer layer; 2. Base layer; 3. Gas barrier layer; 4. Polymer middle layer; 5. Self-heating reaction layer. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Embodiment 1

[0040] See also Figure 1 In this embodiment: a PETG / PET co-extruded self-heat-sealing multilayer film, comprising:

[0041] The outer layer 1 has a gas barrier layer 3 at the bottom, a polymer intermediate layer 4 is provided at the bottom of the gas barrier layer 3, the polymer intermediate layer 4 is made of polyamide, a self-heating reaction layer 5 is provided at the bottom of the polymer intermediate layer 4, the self-heating reaction layer 5 is composed of a mixture of iron powder and salt compounds, and a base layer 2 is provided at the bottom of the self-heating reaction layer 5.

[0042] It should be noted that the outer layer 1 is made of polyethylene terephthalate material and the outer surface is sprayed with a polyether antistatic agent, and the thickness of the outer layer 1 needs to be controlled within 20 microns.

[0043] The base layer 2 is specifically made of polyethylene terephthalate and polybutadiene materials mixed and co-extruded, and the mixing ratio of the two is 1:0.08. The thickness of the base layer 2 needs to be controlled at 15 microns.

[0044] The gas barrier layer 3 is specifically made of ethylene-vinyl alcohol copolymer, and the thickness is controlled at 10 microns.

[0045] Based on the above-mentioned PETG / PET co-extruded self-heat-seal multilayer film, a PETG / PET co-extruded self-heat-seal multilayer film and a preparation method thereof are proposed, comprising the following steps:

[0046] Step 1: Pre-treat each raw material particle to remove impurities, moisture and air inside it;

[0047] Raw material particle pretreatment includes:

[0048] Rinse the raw material particles to remove dirt from the surface of each raw material particle;

[0049] Place the cleaned raw material particles into the drum and use hot air drying equipment to dry the moisture inside the particles;

[0050] The dried raw material particles are placed in a vacuum environment to remove the residual gas impurities inside;

[0051] Step 2: Send the processed raw material particles into the barrel of the extruder through a conveying pipe;

[0052] Step 3: The extruder pushes the raw material forward through the rotating motion of the screw. With the help of the shearing action of the screw, the raw material particles are heated to a molten state. The extruder has multiple sets of heating zones built in, and the temperature of each heating zone is different;

[0053] The temperature of the heating zone inside the extruder can be divided into 4 zones, among which the temperature of the melting zone during the preparation of the outer layer 1 and the base layer 2 needs to be controlled at 260 degrees Celsius;

[0054] During the preparation of the gas barrier layer 3, the temperature of the melting area needs to be controlled at 160 degrees Celsius;

[0055] During the preparation of the polymer intermediate layer 4, the temperature of the melting area needs to be controlled at 220 degrees Celsius;

[0056] During the preparation of the self-heating reaction layer 5, the temperature of the melting area needs to be controlled at 150 degrees Celsius;

[0057] Step 4: The molten fluids of different raw materials are extruded through the flow channel of the die head and stacked together at the die head outlet. During the co-extrusion process, the material flow rate of each flow channel needs to be strictly controlled to ensure that the proportion and thickness of each layer of material meet the requirements;

[0058] The co-extrusion die has multiple flow channels, each of which corresponds to an extruder, which is used to introduce the molten fluid of different raw materials into the die and merge them through the die outlet. The extrusion pressure of the extruder needs to be controlled at 1600ar and the die temperature at 250 degrees Celsius.

[0059] Step 5: The coextruded molten film enters the cooling zone, and the film is blown out of the mouth film by air to form an airbag shape. The film blowing will further stretch the film, and due to the push of the gas, the thickness of the film will gradually become uniform;

[0060] The film blowing ratio needs to be controlled at 1:4, the stretching rate at 15m / min, the gas pressure at 1.5bar, and the cooling water temperature at 15 degrees Celsius;

[0061] Step 6: The blown molten film passes through the cooling zone to achieve qualitative control, quickly reducing the temperature of the film so that the film can solidify and maintain a stable shape;

[0062] Step 7: heat-treating the molten film to further shape it;

[0063] Step 8: During the co-extrusion process, use a film thickness measuring instrument to monitor the film thickness online to ensure that the thickness of each layer of the film is uniform, and test the film's transparency, appearance, tensile strength, elongation at break, heat sealing performance, and air permeability;

[0064] Step nine: After the surface of the tested film is coated with a polyether antistatic agent, it is then rolled into a film roll by a winder.

[0065] Embodiment 2

[0066] See also Figure 1 In this embodiment: a PETG / PET co-extruded self-heat-sealing multilayer film, comprising:

[0067] The outer layer 1 has a gas barrier layer 3 at the bottom, a polymer intermediate layer 4 is provided at the bottom of the gas barrier layer 3, the polymer intermediate layer 4 is made of polyamide, a self-heating reaction layer 5 is provided at the bottom of the polymer intermediate layer 4, the self-heating reaction layer 5 is composed of a mixture of iron powder and salt compounds, and a base layer 2 is provided at the bottom of the self-heating reaction layer 5.

[0068] It should be noted that the outer layer 1 is made of polyethylene terephthalate material and the outer surface is sprayed with a polyether antistatic agent, and the thickness of the outer layer 1 needs to be controlled within 25 microns.

[0069] The base layer 2 is specifically made of polyethylene terephthalate and polybutadiene materials mixed and co-extruded, and the mixing ratio of the two is 1:0.08. The thickness of the base layer 2 needs to be controlled at 20 microns.

[0070] The gas barrier layer 3 is specifically made of ethylene-vinyl alcohol copolymer, and the thickness is controlled at 15 microns.

[0071] Based on the above-mentioned PETG / PET co-extruded self-heat-seal multilayer film, a PETG / PET co-extruded self-heat-seal multilayer film and a preparation method thereof are proposed, comprising the following steps:

[0072] Step 1: Pre-treat each raw material particle to remove impurities, moisture and air inside it;

[0073] Raw material particle pretreatment includes:

[0074] Rinse the raw material particles to remove dirt from the surface of each raw material particle;

[0075] Place the cleaned raw material particles into the drum and use hot air drying equipment to dry the moisture inside the particles;

[0076] The dried raw material particles are placed in a vacuum environment to remove the residual gas impurities inside;

[0077] Step 2: Send the processed raw material particles into the barrel of the extruder through a conveying pipe;

[0078] Step 3: The extruder pushes the raw material forward through the rotating motion of the screw. With the help of the shearing action of the screw, the raw material particles are heated to a molten state. The extruder has multiple sets of heating zones built in, and the temperature of each heating zone is different;

[0079] The temperature of the heating zone inside the extruder can be divided into 4 zones, among which the temperature of the melting zone during the preparation of the outer layer 1 and the base layer 2 needs to be controlled at 280 degrees Celsius;

[0080] During the preparation of the gas barrier layer 3, the temperature of the melting area needs to be controlled at 180 degrees Celsius;

[0081] During the preparation of the polymer intermediate layer 4, the temperature of the melting area needs to be controlled at 220 degrees Celsius;

[0082] During the preparation of the self-heating reaction layer 5, the temperature of the melting area needs to be controlled at 150 degrees Celsius;

[0083] Step 4: The molten fluids of different raw materials are extruded through the flow channel of the die head and stacked together at the die head outlet. During the co-extrusion process, the material flow rate of each flow channel needs to be strictly controlled to ensure that the proportion and thickness of each layer of material meet the requirements;

[0084] The co-extrusion die has multiple flow channels, each of which corresponds to an extruder, which is used to introduce the molten fluid of different raw materials into the die and merge them through the die outlet. The extrusion pressure of the extruder needs to be controlled at 2200 bar and the die temperature at 250 degrees Celsius.

[0085] Step 5: The coextruded molten film enters the cooling zone, and the film is blown out of the mouth film by air to form an airbag shape. The film blowing will further stretch the film, and due to the push of the gas, the thickness of the film will gradually become uniform;

[0086] The film blowing ratio needs to be controlled at 1:5, the stretching rate at 25m / min, the gas pressure at 2.5bar, and the cooling water temperature at 20 degrees Celsius;

[0087] Step 6: The blown molten film passes through the cooling zone to achieve qualitative control, quickly reducing the temperature of the film so that the film can solidify and maintain a stable shape;

[0088] Step 7: heat-treating the molten film to further shape it;

[0089] Step 8: During the co-extrusion process, use a film thickness measuring instrument to monitor the film thickness online to ensure that the thickness of each layer of the film is uniform, and test the film's transparency, appearance, tensile strength, elongation at break, heat sealing performance, and air permeability;

[0090] Step nine: After the surface of the tested film is coated with a polyether antistatic agent, it is then rolled into a film roll by a winder.

[0091] The average thickness, transparency, appearance, tensile strength, elongation at break, heat sealing performance and air permeability of the co-extruded self-heat-seal multi-layer films prepared in Examples 1-2 were tested respectively.

[0092] The test results can be found in the following table:

[0093]

[0094] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0095] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A PETG / PET co-extruded self-heat-sealing multilayer film, characterized in that: include: An outer layer (1), a gas barrier layer (3) is arranged at the bottom of the outer layer (1), a polymer intermediate layer (4) is arranged at the bottom of the gas barrier layer (3), the polymer intermediate layer (4) is selected from polyamide, a self-heating reaction layer (5) is arranged at the bottom of the polymer intermediate layer (4), the self-heating reaction layer (5) is composed of a mixture of iron powder and salt compounds, and a base layer (2) is arranged at the bottom of the self-heating reaction layer (5).

2. A PETG / PET co-extruded self-heat-seal multilayer film according to claim 1, characterized in that: The outer layer (1) is made of polyethylene terephthalate material and the outer surface is sprayed with a polyether antistatic agent. The thickness of the outer layer (1) needs to be controlled within 12-30 microns.

3. A PETG / PET co-extruded self-heat-seal multilayer film and a preparation method thereof according to claim 1, characterized in that: The base layer (2) is specifically made of polyethylene terephthalate and polybutadiene materials mixed and co-extruded, and the mixing ratio of the two is 1:0.

08. The thickness of the base layer (2) needs to be controlled within 10-25 microns.

4. A PETG / PET co-extruded self-heat-sealing multilayer film and a preparation method thereof according to claim 1, characterized in that: The gas barrier layer (3) is specifically made of ethylene-vinyl alcohol copolymer, and its thickness is controlled to be 10-50 microns.

5. A method for preparing a PETG / PET co-extruded self-heat-sealable multilayer film according to claims 1-3, characterized in that: The steps include: Step 1: Pre-treat each raw material particle to remove impurities, moisture and air inside it; Step 2: Send the processed raw material particles into the barrel of the extruder through a conveying pipe; Step 3: The extruder pushes the raw material forward through the rotating motion of the screw. With the help of the shearing action of the screw, the raw material particles are heated to a molten state. The extruder has multiple sets of heating zones built in, and the temperature of each heating zone is different; Step 4: The molten fluids of different raw materials are extruded through the flow channel of the die head and stacked together at the die head outlet. During the co-extrusion process, the material flow rate of each flow channel needs to be strictly controlled to ensure that the proportion and thickness of each layer of material meet the requirements; Step 5: The coextruded molten film enters the cooling zone, and the film is blown out of the mouth film by air to form an airbag shape. The film blowing will further stretch the film, and due to the push of the gas, the thickness of the film will gradually become uniform; Step 6: The blown molten film passes through the cooling zone to achieve qualitative control, quickly reducing the temperature of the film so that the film can solidify and maintain a stable shape; Step 7: heat-treating the molten film to further shape it; Step 8: During the co-extrusion process, use a film thickness measuring instrument to monitor the film thickness online to ensure that the thickness of each layer of the film is uniform, and test the film's transparency, appearance, tensile strength, elongation at break, heat sealing performance, and air permeability; Step nine: After the surface of the tested film is coated with a polyether antistatic agent, it is then rolled into a film roll by a winder.

6. The method for preparing a PETG / PET co-extruded self-heat-sealing multilayer film according to claim 5, characterized in that: The raw material particle pretreatment in step 1 includes: Rinse the raw material particles to remove dirt from the surface of each raw material particle; Place the cleaned raw material particles into the drum and use hot air drying equipment to dry the moisture inside the particles; The dried raw material particles are placed in a vacuum environment to remove the gas impurities remaining inside.

7. The method for preparing a PETG / PET co-extruded self-heat-sealing multilayer film according to claim 5, characterized in that: The temperature of the internal heating zone of the extruder in step 3 can be divided into 4 zones, wherein the temperature of the melting zone during the preparation of the outer layer (1) and the base layer (2) needs to be controlled at 260-290 degrees Celsius; During the preparation of the gas barrier layer (3), the temperature of the melting zone needs to be controlled at 150-200 degrees Celsius; During the preparation of the polymer intermediate layer (4), the temperature of the melting zone needs to be controlled at 220-240 degrees Celsius; During the preparation of the self-heating reaction layer (5), the temperature of the melting area needs to be controlled at 150-180 degrees Celsius.

8. The method for preparing a PETG / PET co-extruded self-heat-sealing multilayer film according to claim 5, characterized in that: The co-extrusion die described in step 4 has multiple flow channels, each flow channel corresponds to an extruder, which is used to introduce the molten fluid of different raw materials into the die and merge them through the die outlet. The extrusion pressure of the extruder needs to be controlled at 1500-2200 bar, and the die temperature is controlled at 250-300 degrees Celsius.

9. The method for preparing a PETG / PET co-extruded self-heat-sealing multilayer film according to claim 5, characterized in that: In step 5, the film blowing ratio needs to be controlled at 1:3-6, the stretching rate is controlled at 10-30 m / min, the gas pressure is controlled at 1.5-2.5 bar, and the cooling water temperature is maintained at 15-25 degrees Celsius.

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