High-barrier straight-line easy-tear thermoformed film and method for making same

Abstract

The application relates to the technical field of packaging materials, in particular to a high-barrier straight-line easy-to-tear thermoforming film which comprises a base film layer, a glue layer and a high-barrier heat-sealing layer, the base film layer and the high-barrier heat-sealing layer are straight-line easy-to-tear films, the base film layer is composed of eight or ten water-cooling downward-blowing co-extrusion polyethylene films, and the high-barrier heat-sealing layer is composed of seven or nine air-cooling upward-blowing co-extrusion polyethylene films. The base film layer and the high-barrier heat-sealing layer both have the straight-line easy-to-tear effect, the cost is reduced under the condition of guaranteeing excellent deep-drawing thermoforming performance, and the market blank is made up.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a high-barrier, straight-line, easy-tear thermoforming film and its preparation method. Background Technology

[0002] In recent years, with economic development, people's material lives have become increasingly richer, and the pace of life has accelerated. The food industry is also developing towards greater convenience and speed. This has led to new requirements for the packaging of staple and non-staple food semi-finished products: easy to open, pour, and remove; convenient to use; and high barrier properties to effectively maintain the quality of the packaged contents.

[0003] Currently available high-barrier thermoforming films on the market have high tear strength but lack the ability to be easily torn in a straight line; or they are easy to tear in a straight line but cannot be deeply stretched and thermoformed.

[0004] For example, Chinese patent CN109666292A describes a BOPA film with high barrier properties and easy tearing properties. It describes a nylon film with good barrier properties and easy tearing properties, and low production cost. It can improve the barrier properties of nylon film by more than 100%, and also has straight tearing properties. Compared with existing ordinary BOPA nylon film, the production cost is reduced by 50% compared with existing easy tearing nylon film.

[0005] The problem with the above technology is that although nylon film reduces material costs, it cannot be deeply stretched and thermoformed when actually used in food packaging bags, which limits the process design. Summary of the Invention

[0006] The purpose of this invention is to provide a high-barrier, straight-line easy-tear thermoforming film and its preparation method, which, while ensuring excellent thermoforming performance, is also low-cost and has a straight-line easy-tear effect, thus solving the problems existing in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-barrier straight-line easy-tear thermoformed film, comprising a base film layer, an adhesive layer, and a high-barrier heat-sealing layer, wherein the base film layer and the high-barrier heat-sealing layer are straight-line easy-tear films, wherein the base film layer is composed of eight to ten layers of water-cooled down-blown co-extruded polyethylene film, and the high-barrier heat-sealing layer is composed of five, seven, nine, eleven, or thirteen layers of air-cooled up-blown co-extruded polyethylene film.

[0008] Furthermore, the water-cooled downblown co-extruded polyethylene film consists of an eight- or ten-layer structure, with the main structure being: PE layer - TIE adhesive layer - PA layer - TIE adhesive layer - PE layer.

[0009] Furthermore, the thickness of the water-cooled downblown co-extruded polyethylene film is 50–250 μm.

[0010] Furthermore, the longitudinal traction ratio of the water-cooled downblown co-extruded polyethylene film is ≥4.

[0011] Furthermore, the air-cooled, top-blown co-extruded polyethylene film is composed of five, seven, nine, eleven, or thirteen layers, with the main structure being: PE layer - TIE adhesive layer - EVOH layer - TIE adhesive layer - PE layer.

[0012] Furthermore, the thickness of the air-cooled, top-blown co-extruded polyethylene film is 30–100 μm.

[0013] Furthermore, the adhesive layer is a solvent-free polyurethane adhesive layer.

[0014] Based on the same technical problem, the present invention further provides a method for preparing a high-barrier, straight-line, easy-tear thermoforming film, the steps of which are as follows:

[0015] S1. Preparation of the base film layer:

[0016] S11. The raw materials for each layer of the water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders, melt-mixed in the barrel of the extruder, and extruded through the die.

[0017] S12. After the raw material is extruded through the die head, it is blown into a film bubble with a transverse blow-up ratio ≥1.2. The film bubble is cooled by water cooling.

[0018] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled to be ≥4 to prepare a co-extruded polyethylene film.

[0019] S2. Preparation of a high-barrier heat-sealing layer:

[0020] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0021] S23. Blow molding into a film bubble with a lateral blow-up ratio ≥1.4. The film bubble is cooled by the action of the air ring, which is located below the film bubble, and the cold air is blown upward to the surface of the film bubble.

[0022] S23. The film bubble is squeezed into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled to be wound up under the action of the main traction roller to form the air-cooled top-blown co-extruded polyethylene high-barrier film.

[0023] S3. Film forming: The base film layer and the high-barrier heat-sealing layer are bonded together by the adhesive layer.

[0024] Furthermore, in step S11, the raw materials of the water-cooled downblown co-extruded polyethylene film have a PA content of 20% to 45%, a PE content of 55% to 80%, and a TIE content of 5% to 15%.

[0025] Furthermore, in step S21, the raw material of the air-cooled top-blown co-extruded polyethylene film has a PE content of 80% to 95%, a TIE content of 5% to 15%, and an EVOH content of 3% to 20%.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention uses water-cooled down-blown co-extruded polyethylene film to form the base film layer and air-cooled up-blown co-extruded polyethylene film to form the high-barrier heat-sealing layer. Both the base film layer and the high-barrier heat-sealing layer have a straight tear-resistant effect. While ensuring excellent deep stretching and thermoforming performance, the cost is reduced, filling a market gap. Attached Figure Description

[0027] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 This is a schematic diagram of the structure of the high-barrier, straight, easy-tear thermoforming film of the present invention.

[0029] The components are: 1. Base film layer; 2. Adhesive layer; 3. High-barrier heat seal layer. Detailed Implementation

[0030] 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.

[0031] Please see Figure 1 A high-barrier, straight-line, easy-tear thermoformed film is disclosed, comprising a base film layer 1, an adhesive layer 2, and a high-barrier heat-sealing layer 3. Both the base film layer 1 and the high-barrier heat-sealing layer 3 are straight-line, easy-tear films. The base film layer 1 is composed of eight or ten layers of water-cooled down-blown co-extruded polyethylene film. The main structure of the water-cooled down-blown co-extruded polyethylene film is PE / TIE / PA / TIE / PE in sequence. The eight or ten layers refer to the addition of PE or PA layers to the main structure, with the PE or PA layers connected by a TIE adhesive layer. Each PE or PA layer after synthesis counts as one layer, totaling eight or ten layers. The raw materials for the water-cooled down-blown co-extruded polyethylene film contain 20%–45% PA, 55%–80% PE, and 5%–15% TIE.

[0032] The high-barrier heat-sealing layer 3 consists of five, seven, nine, eleven, or thirteen layers of air-cooled, top-blown co-extruded polyethylene film. The main structure of the air-cooled, top-blown co-extruded polyethylene film is PE / TIE / EVOH / TIE / PE. PE layers are added accordingly to the main structure, and the PE layers are connected to the main structure through TIE adhesive layers. Each PE layer and EVOH layer after synthesis counts as one layer, totaling five, seven, nine, eleven, or thirteen layers. The raw materials for the air-cooled, top-blown co-extruded polyethylene film have a PE content of 80%–95%, a TIE content of 5%–15%, and an EVOH content of 3%–20%. The EVOH layer provides oxygen barrier properties, and the PE layer provides water barrier properties, further enhancing the water and oxygen barrier properties of the high-barrier, straight-line, easy-tear thermoforming film.

[0033] A method for preparing a high-barrier, straight-line, easy-tear thermoforming film, comprising the following steps:

[0034] S1. Preparation of the base film layer:

[0035] S11. The raw materials for each layer of the water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders, melt-mixed in the barrel of the extruder, and extruded through the die.

[0036] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio ≥1.2. The bubble is cooled by the air ring, which is located above the bubble. The cold air is blown downward to the surface of the bubble.

[0037] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled to be ≥4 to prepare a co-extruded polyethylene film.

[0038] S2. Preparation of a high-barrier heat-sealing layer:

[0039] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0040] S22. Blow molding into a film bubble with a lateral blow-up ratio ≥1.4. The film bubble is cooled by the action of the air ring, which is located below the film bubble, and the cold air is blown upward to the surface of the film bubble.

[0041] S23. The film bubble is squeezed into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller and then air-cooled to form an air-cooled top-blown co-extruded polyethylene high-barrier film.

[0042] S3. Thin film forming: The base film layer and the high-barrier heat seal layer are bonded together with an adhesive layer.

[0043] Traditionally, easy-tear thermoforming films have been made from biaxially stretched films such as BOPA and BOPET. However, biaxially stretched films cannot undergo further deep stretching or thermoforming. In contrast, the method described in this embodiment uses downblowing and water cooling to form the film, eliminating the need for biaxial stretching. Therefore, the easy-tear thermoforming film prepared by this method exhibits excellent deep stretching and thermoforming properties.

[0044] The above-mentioned high-barrier straight-line easy-tear thermoforming film and its preparation method are further described in detail below with reference to Examples 1 to 3.

[0045] Example 1

[0046] The raw material composition of the high-barrier, straight-line, easy-tear thermoforming film is as follows:

[0047] Base film layer: The eight-layer water-cooled downblown co-extruded polyethylene film structure is as follows: PE layer-PE layer-TIE adhesive layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; PA content: 20%; thickness 100μm.

[0048] High-barrier heat-sealing layer: The five-layer structure of the air-cooled top-blown co-extruded polyethylene film consists of a PE layer, a TIE adhesive layer, an EVOH layer, a TIE adhesive layer, and a PE layer, with a thickness of 50μm.

[0049] Adhesive layer: The two film layers are bonded together using a solvent-free polyurethane adhesive;

[0050] The preparation process of the high-barrier, straight-line, easy-tear thermoforming film is as follows:

[0051] S1. Preparation of the base film layer:

[0052] S11. The component raw materials of each layer of water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders in proportion, melt-mixed in the barrel of the extruder, and extruded through the die.

[0053] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio of 1.25. The bubble is cooled by the air ring, which is located above the bubble. The cold air is blown downwards to the surface of the bubble.

[0054] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled at 4.25 to prepare a co-extruded polyethylene film.

[0055] S2. Preparation of a high-barrier heat-sealing layer:

[0056] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0057] S22, blow molding into a film bubble with a lateral blow-up ratio of 1.5. The film bubble is cooled by the action of the air ring, which is located below the film bubble. The cold air is blown upward to the surface of the film bubble.

[0058] S23. The film bubble is squeezed into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller to co-extrude polyethylene film.

[0059] S3. Film forming: The base film layer and the high-barrier heat-sealing layer are bonded together with an adhesive layer to obtain a high-barrier straight-line easy-tear thermoformed film.

[0060] Example 2

[0061] The raw material composition of the high-barrier, straight-line, easy-tear thermoforming film II is as follows:

[0062] Base film layer: The ten-layer structure is as follows: PE layer-PE layer-TIE adhesive layer-PA layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; PA content: 30%, thickness 100μm.

[0063] Adhesive layer: The two films above are bonded together using a solvent-free polyurethane adhesive.

[0064] High-barrier heat-sealing layer: The five-layer air-cooled top-blown co-extruded polyethylene film consists of a PE layer, a TIE adhesive layer, an EVOH layer, a TIE adhesive layer, a PE layer, a TIE adhesive layer, and a PE layer, with a thickness of 50 μm.

[0065] The preparation method of the high-barrier, straight-line, easy-tear thermoforming film II is as follows:

[0066] S1. Preparation of the base film layer:

[0067] S11. The component raw materials of each layer of water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders in proportion, melt-mixed in the barrel of the extruder, and extruded through the die.

[0068] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio of 1.25. The bubble is cooled by the air ring, which is located above the bubble. The cold air is blown downwards to the surface of the bubble.

[0069] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled at 4.25 to prepare a co-extruded polyethylene film.

[0070] S2. Preparation of a high-barrier heat-sealing layer:

[0071] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0072] S22, blow molding into a film bubble with a lateral blow-up ratio of 1.5. The film bubble is cooled by the action of the air ring, which is located below the film bubble. The cold air is blown upward to the surface of the film bubble.

[0073] S23. The film bubble is squeezed into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller to co-extrude polyethylene high barrier film.

[0074] S3. Film forming: The base film layer and the high-barrier heat-sealing layer are bonded together with an adhesive layer to obtain a high-barrier straight-line easy-tear thermoformed film II.

[0075] Example 3

[0076] The raw material composition of the high-barrier, straight-line, easy-tear thermoforming film 3 is as follows:

[0077] Base film layer: The ten-layer structure is as follows: PE layer-PE layer-TIE adhesive layer-PA layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; PA content: 35%, thickness 100μm.

[0078] Adhesive layer: The two films above are bonded together using a solvent-free polyurethane adhesive.

[0079] High-barrier heat-sealing layer: The five-layer structure of the air-cooled top-blown co-extruded polyethylene film consists of a PE layer, a TIE adhesive layer, an EVOH layer, a TIE adhesive layer, and a PE layer, with a thickness of 50μm.

[0080] The preparation method of high-barrier straight-line easy-tear thermoforming film 3 is as follows:

[0081] S1. Preparation of the base film layer:

[0082] S11. The component raw materials of each layer of water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders in proportion, melt-mixed in the barrel of the extruder, and extruded through the die.

[0083] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio of 1.4. The bubble is cooled by the air ring, which is located above the bubble. The cold air is blown downwards to the surface of the bubble.

[0084] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled at 4.3 to prepare a co-extruded polyethylene film.

[0085] S2. Preparation of a high-barrier heat-sealing layer:

[0086] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0087] S22, blow molding into a film bubble with a lateral blow-up ratio of 1.7. The film bubble is cooled by the action of the air ring, which is located below the film bubble. The cold air is blown upward to the surface of the film bubble.

[0088] S23. The film bubble is squeezed into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller to co-extrude polyethylene high barrier film.

[0089] S3. Film forming: The base film layer and the high-barrier heat-sealing layer are bonded together with an adhesive layer to obtain a high-barrier, straight, easy-tear thermoformed film.

[0090] Example 4

[0091] The raw material composition of the high-barrier, straight-line, easy-tear thermoforming film 3 is as follows:

[0092] Base film layer: The ten-layer structure is as follows: PE layer-PE layer-TIE adhesive layer-PA layer-PA layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; PA content: 45%, thickness 75μm.

[0093] Adhesive layer: The two films above are bonded together using a solvent-free polyurethane adhesive.

[0094] High-barrier heat-sealing layer: The seven-layer air-cooled top-blown co-extruded polyethylene film structure consists of PE layer-PE layer-TIE adhesive layer-EVOH layer-TIE adhesive layer-PE layer, with a thickness of 75μm.

[0095] The preparation method of high-barrier straight-line easy-tear thermoforming film 4 is as follows:

[0096] S1. Preparation of the base film layer:

[0097] S11. The component raw materials of each layer of water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders in proportion, melt-mixed in the barrel of the extruder, and extruded through the die.

[0098] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio of 1.4. The bubble is cooled by the air ring, which is located above the bubble. The cold air is blown downwards to the surface of the bubble.

[0099] S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretching ratio is controlled at 4.2 to prepare a co-extruded polyethylene film.

[0100] S2. Preparation of a high-barrier heat-sealing layer:

[0101] S21. The component raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders in proportion and melt-mixed in the barrel of the extruder.

[0102] S22, blow molding into a film bubble with a lateral blow-up ratio of 1.7. The film bubble is cooled by the action of the air ring, which is located below the film bubble. The cold air is blown upward to the surface of the film bubble.

[0103] S23. The film bubble is squeezed into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller to co-extrude polyethylene high barrier film.

[0104] S3. Film forming: A high-barrier, straight, easy-tear thermoformed film is obtained by solvent-free lamination of the base film layer and the high-barrier heat-sealing layer.

[0105] Comparative Example 1

[0106] The structure of membrane 1 in Comparative Example 1 is as follows: PA / TIE / PA / EVOH / PA / TIE / PE, with a thickness of 150 μm and a PA content of 35%.

[0107] The preparation method of membrane 1 in Comparative Example 1 is as follows:

[0108] The raw materials of each layer of water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders in proportion, melt-mixed in the barrel of the extruder, and extruded through the die.

[0109] S12. After the raw material is extruded through the die head, it is blown up with a transverse blow-up ratio of 1.4. The film bubble is cooled by cooling water.

[0110] S13. The film bubble is extruded into a sheet film under the action of the clamping plate and the traction guide roller. The film is pulled under the action of the main traction roller with a longitudinal traction ratio of 4.0 to form a water-cooled downblown co-extruded polyethylene film. After co-extrusion, film one is obtained.

[0111] Comparative Example 2

[0112] The structure of membrane 2 in Comparative Example 2 is as follows: BOPA / PE, BOPA 25μm, polyethylene PE membrane 125μm, total thickness 150μm.

[0113] The preparation method of membrane 2 in Comparative Example 2 is as follows:

[0114] S1. Material preparation;

[0115] S2, BOPA film forming: After mixing the raw materials prepared in the first step, the mixture is fed into a twin-screw or single-screw extruder for melting and plasticizing. The mixture is then extruded through a die onto a cold roller with a surface temperature of 15°C to form a thick sheet. After preheating at 150°C, the sheet is biaxially stretched at 190°C and then heat-set and corona-treated at 150°C to produce a 25μm BOPA film.

[0116] S3. A 125μm polyethylene (PE) film was prepared by a down-blowing water-cooling process.

[0117] S4. Membrane II is obtained by solvent-free composite of BOPA membrane and PE membrane.

[0118] The films prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to tear strength testing according to standard GB / T 16578.1-2008. The forming depth was tested using a thermoforming machine under the same mold. The test results are shown in the table below.

[0119] Table 1. Test results of tear strength and forming depth of the films in Examples 1-4 and Comparative Examples 1-2.

[0120]

[0121] The data in the table show that the trouser tear strength MD(N) of the high-barrier straight-line easy-tear thermoformed films of Examples 1-4 is better than that of Comparative Example 1. The trouser tear strength MD(N) of Example 3 is the same as that of Comparative Example 2, with Examples 3 and 4 showing better trouser tear strength MD(N) results. The trouser tear strength TD(N) of the high-barrier straight-line easy-tear thermoformed films of Examples 1-4 is better than that of Comparative Examples 1-2, with Examples 2-4 showing more stable trouser tear strength TD(N) results. The forming depth of the high-barrier straight-line easy-tear thermoformed films of Examples 1-4 is the same as that of Comparative Example 1 and better than that of Comparative Example 2. In summary, the high-barrier straight-line easy-tear thermoformed films of Examples 1-4 can improve tearability and straight-line tear performance.

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-barrier, straight-line, easy-tear thermoforming film, comprising a base film layer (1), an adhesive layer (2), and a high-barrier heat-sealing layer (3), characterized in that, The base film layer (1) and the high-barrier heat-sealing layer (3) are straight, easy-tear films. The base film layer (1) is composed of eight or ten layers of water-cooled down-blown co-extruded polyethylene film. The structure of the eight-layer water-cooled down-blown co-extruded polyethylene film is PE layer-PE layer-TIE adhesive layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; the structure of the ten-layer water-cooled down-blown co-extruded polyethylene film is PE layer-PE layer-TIE adhesive layer-PA layer-PA layer-TIE adhesive layer-PE layer-PE layer-PE layer; and the longitudinal traction ratio of the water-cooled down-blown co-extruded polyethylene film is ≥4. The high-barrier heat-sealing layer (3) is composed of five layers of air-cooled top-blown co-extruded polyethylene film, which are in sequence PE layer-TIE adhesive layer-EVOH layer-TIE adhesive layer-PE layer.

2. The high-barrier, straight-line, easy-tear thermoformed film according to claim 1, characterized in that, The thickness of the water-cooled downblown co-extruded polyethylene film is 50–250 μm.

3. The high-barrier, straight-line, easy-tear thermoformed film according to claim 1, characterized in that, The thickness of the air-cooled, top-blown co-extruded polyethylene film is 30–100 μm.

4. The high-barrier, straight-line, easy-tear thermoformed film according to claim 1, characterized in that, The adhesive layer (2) is a solvent-free polyurethane adhesive layer.

5. A method for preparing a high-barrier, straight-line, easy-tear thermoforming film according to any one of claims 1 to 4, characterized in that, The steps are as follows: S1. Preparation of the base film layer (1): S11. The raw materials for each layer of the water-cooled downblown co-extruded polyethylene film are added to the corresponding extruders, melt-mixed in the barrel of the extruder, and extruded through the die. S12. After the raw material is extruded through the die head, it is blown into a film bubble with a transverse blow-up ratio ≥1.

2. The film bubble is cooled by cooling water. S13. The membrane bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled under the action of the main traction roller. The longitudinal stretch ratio is controlled to be ≥4 to prepare a co-extruded polyethylene film. S2. Preparation of a high-barrier heat seal layer (3): S21. The raw materials of each layer of the air-cooled and top-blown co-extruded polyethylene film are added to the corresponding extruders and melt-mixed in the barrel of the extruder. S22. Blow molding into a film bubble with a lateral blow-up ratio ≥1.

4. The film bubble is cooled by the action of the air ring, which is located below the film bubble, and the cold air is blown upward to the surface of the film bubble. S23. The film bubble is extruded into a sheet film under the action of the herringbone plate and the traction guide roller. The film is pulled to the winding under the action of the main traction roller to prepare a co-extruded polyethylene high barrier film. S3, film forming: the base film layer (1) and the high-barrier heat-sealing layer (3) are bonded together by the adhesive layer (2).

6. The method for preparing a high-barrier, straight-line, easy-tear thermoforming film according to claim 5, characterized in that, In step S11, the raw materials of the water-cooled downblown co-extruded polyethylene film have a PA content of 20% to 45%, a PE content of 55% to 80%, and a TIE content of 5% to 15%.

7. The method for preparing a high-barrier, straight-line, easy-tear thermoforming film according to claim 5, characterized in that, In step S21, the raw materials of the air-cooled top-blown co-extruded polyethylene film have a PE content of 80% to 95%, a TIE content of 5% to 15%, and an EVOH content of 3% to 20%.

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