Damp-proof food packaging composite film preparation device and preparation process

Abstract

The invention discloses a damp-proof food packaging composite film preparation device and process, and the damp-proof food packaging composite film preparation device comprises a base table, a shell, a printing part, a pair of flattening mechanisms, a pair of linkage mechanisms and a pair of drying mechanisms. Wherein a winding mechanism is mounted on the base station. The shell is installed on the base table and arranged on the winding front side of the winding mechanism, and a plurality of guide rollers are installed in the shell. The printing part is installed in the shell and arranged on the upper side of the base table, a pair of telescopic air cylinders is installed on the shell, and the free ends of the telescopic air cylinders are connected with the printing part. The pair of flattening mechanisms is symmetrically installed on the pair of side walls of the printing part and can press the packaging film before the printing part under the action of gravity. Printing equipment of the packaging film can be optimized, then the printed packaging film can be pre-dried in time, printing ink is prevented from flowing or being wiped by other objects in the conveying process of the packaging film, and therefore the printing effect of the packaging film can be guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of composite film preparation technology, specifically relating to a moisture-proof food packaging composite film preparation device and preparation process. Background Technology

[0002] Food packaging composite films are packaging materials made of multiple layers of different materials through a lamination process. They are primarily used to protect food properties and facilitate transportation. Generally, they consist of an outer layer (such as polyester or nylon), a middle layer (such as aluminum foil or metallized film), and an inner layer (such as polyethylene), manufactured through processes such as printing and lamination. The combination of multiple materials gives composite films different properties, such as protection, durability, oxygen barrier properties, and heat insulation. Due to their stable structure, moisture resistance, transparency, and acid and alkali resistance, composite films are widely used in the food packaging industry.

[0003] The core processes in the production of existing food packaging composite films include printing, lamination, and slitting. The printing process involves using water-based inks to print patterns or markings on the outer material (such as plastic film), transferring the ink dots using gravure printing to ultimately form the designed pattern. For example, Chinese patent CN221272328U discloses a printing and coding device for food packaging bags. Its abutment structure allows the packaging bags to be neatly laid on a base, preventing wrinkles and ensuring subsequent printing quality. However, this device has a limited function and cannot pre-dry the printed packaging film immediately, causing the ink to easily flow or be wiped away, thus affecting the printing effect.

[0004] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a device and process for preparing moisture-proof food packaging composite film.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a moisture-proof food packaging composite film preparation device and preparation process, which can solve the problem that the printing equipment cannot pre-dry the packaging film ink in time.

[0007] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0008] A moisture-proof food packaging composite film preparation device includes a base, a shell, a printing section, a pair of flattening mechanisms, a pair of linkage mechanisms, and a pair of drying mechanisms. A winding mechanism is mounted on the base. The shell is mounted on the base and positioned before the winding mechanism, and multiple guide rollers are installed inside the shell. The printing section is installed inside the shell and positioned above the base, and a pair of telescopic cylinders are mounted on the shell, with their free ends connected to the printing section. The pair of flattening mechanisms are symmetrically mounted on a pair of sidewalls of the printing section. Under gravity, the flattening mechanisms can press the packaging film before the printing section and move relative to each other along the sidewalls of the printing section. The pair of linkage mechanisms are respectively mounted on the pair of flattening mechanisms and can be triggered when the flattening mechanisms move relative to each other along the sidewalls of the printing section. The pair of drying mechanisms are respectively mounted on the pair of flattening mechanisms and are triggered by the linkage mechanisms to dry the printed packaging film.

[0009] In one or more embodiments of the present invention, the flattening mechanism includes a mounting plate, a pair of guide rods, a linkage plate, a pair of guide grooves, a pair of connecting rods, and a pressing plate. The mounting plate is bolted to the printing section. The pair of guide rods are fixedly connected to the lower end face of the mounting plate. The linkage plate is slidably disposed between the pair of guide rods. The pair of guide grooves are mounted on the side wall of the printing section, and the linkage plate is slidably connected to the guide grooves. The pair of connecting rods are fixedly connected to the lower end face of the linkage plate. The pressing plate is fixedly connected to the end of the connecting rods away from the linkage plate.

[0010] In one or more embodiments of the present invention, a limiting ring is connected to the lower end of the guide rod, and the diameter of the limiting ring is larger than the diameter of the guide rod.

[0011] In one or more embodiments of the present invention, the length of the guide groove is less than the height of the printed portion and greater than the length of the guide rod.

[0012] In one or more embodiments of the present invention, the distance between a pair of pressure plates is greater than the width of the printing section, and the pressure plates are made of metal.

[0013] In one or more embodiments of the present invention, the linkage plate is provided with a groove, and the linkage mechanism includes a rotating shaft, a pair of gears, and a pair of racks. The rotating shaft is rotatably connected to the groove. The pair of gears is fixedly connected to the rotating shaft. The pair of racks are both fixedly connected to the side wall of the printing section, the racks are coplanar with the guide grooves and are disposed between the pair of guide grooves, and the racks mesh with the gears.

[0014] In one or more embodiments of the present invention, the drying mechanism includes a pair of winding reels, a pull rope, and a drying hood. The pair of winding reels are disposed between a pair of gears. The pull rope is wound around the winding reels. The drying hood is disposed on the upper side of the linkage plate, one end of the pull rope is connected to the drying hood, and the side of the drying hood near the printing section has a mounting groove, in which a drying assembly is installed.

[0015] In one or more embodiments of the present invention, the pressure plate is provided with a cavity, and a plurality of air holes are provided on the side of a pair of pressure plates that are close to each other, and the cavity is connected to the outside through the air holes.

[0016] In one or more embodiments of the present invention, the preparation apparatus further includes an air blowing mechanism, which includes an impeller, an outer cover, and an air supply pipe. The impeller is mounted on the rotating shaft, and a pair of pull ropes are symmetrical about the impeller. The outer cover is disposed outside the impeller, the impeller is rotatably connected to the rotating shaft, and fixedly connected to the linkage plate, and the outer cover is provided with a ventilation section. One end of the air supply pipe is disposed inside the outer cover, and the other end is disposed inside the cavity.

[0017] A process for preparing a moisture-proof food packaging composite film, using the aforementioned preparation apparatus, includes the following steps:

[0018] S1. The outer layer material, the middle layer material and the inner layer material are melted and plasticized respectively. The outer layer material is polypropylene, the middle layer material includes ethylene-vinyl alcohol copolymer and 0.5-3 wt% melt-reactive crosslinking agent, and the inner layer material is modified polyethylene.

[0019] S2. The melt layers obtained in S1 are introduced into the multi-layer co-extrusion die head to merge and form a composite melt;

[0020] S3. In the melt flow channel inside the multi-layer co-extrusion die or adjacent to its outlet, the temperature is controlled at 180-210°C to allow the ethylene-vinyl alcohol copolymer in the intermediate layer material to undergo an in-situ crosslinking reaction with the melt reactive crosslinking agent for 15-90 seconds.

[0021] S4. The composite melt that has undergone in-situ crosslinking reaction is cooled and shaped by casting or blowing to obtain a composite film;

[0022] S5. Printing and winding the shaped composite film, wherein the printing device is the moisture-proof food packaging composite film preparation device mentioned above.

[0023] Compared with the prior art, the moisture-proof food packaging composite film preparation device and preparation process of the present invention can optimize the printing equipment of the packaging film, and thus can pre-dry the printed packaging film in time, avoiding the flow of printing ink or being wiped by other objects during the transportation of the packaging film, thereby ensuring the printing effect of the packaging film. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a perspective view of a moisture-proof food packaging composite film preparation device according to an embodiment of the present invention;

[0026] Figure 2 This is a first-angle schematic diagram of a partial structure of a moisture-proof food packaging composite film preparation device according to an embodiment of the present invention;

[0027] Figure 3 for Figure 2 Schematic diagram of the structure at point A in the middle;

[0028] Figure 4 This is a second-angle schematic diagram of a partial structure of a moisture-proof food packaging composite film preparation device according to an embodiment of the present invention;

[0029] Figure 5 This is a first-angle perspective view of the linkage mechanism in one embodiment of the present invention;

[0030] Figure 6 for Figure 5 Schematic diagram of the structure at point B;

[0031] Figure 7 This is a second perspective view of the linkage mechanism in one embodiment of the present invention;

[0032] Figure 8 This is a partial structural cross-sectional view of a moisture-proof food packaging composite film preparation device according to an embodiment of the present invention;

[0033] Figure 9 for Figure 8 Schematic diagram of the structure at point C;

[0034] Figure 10 This is a flowchart of a method for preparing a moisture-proof food packaging composite film according to an embodiment of the present invention.

[0035] Explanation of key figure labels:

[0036] 1-Base, 101-Winding mechanism, 2-Outer shell, 201-Guide roller, 3-Printing section, 301-Telescopic cylinder, 4-Pressing mechanism, 401-Mounting plate, 402-Guide rod, 403-Linkage plate, 404-Guide groove, 405-Connecting rod, 406-Pressing plate, 4061-Cavity, 4062-Air hole, 5-Linkage mechanism, 501-Rotating shaft, 502-Gear, 503-Rack, 6-Drying mechanism, 601-Winding reel, 602-Pull rope, 603-Drying hood, 604-Drying assembly, 7-Blowing mechanism, 701-Impeller, 702-Outer cover, 703-Ventilation section, 704-Air supply pipe. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0038] like Figures 1 to 9 As shown, an embodiment of the present invention provides a moisture-proof food packaging composite film preparation device, comprising a base 1, a housing 2, a printing section 3, a pair of flattening mechanisms 4, a pair of linkage mechanisms 5, and a pair of drying mechanisms 6. A winding mechanism 101 is mounted on the base 1. The housing 2 is mounted on the base 1 and located on the front side of the winding mechanism 101, and multiple guide rollers 201 are installed inside the housing 2. The printing section 3 is installed inside the housing 2 and located on the upper side of the base 1. A pair of telescopic cylinders 301 are mounted on the housing 2, with their free ends connected to the printing section 3. The pair of flattening mechanisms 4 are symmetrically mounted on a pair of sidewalls of the printing section 3. Under the action of gravity, the flattening mechanisms 4 can press the packaging film before the printing section 3 and move relative to each other along the sidewalls of the printing section 3. The pair of linkage mechanisms 5 are respectively mounted on the pair of flattening mechanisms 4 and can be triggered when the flattening mechanisms 4 move relative to each other along the sidewalls of the printing section 3. A pair of drying mechanisms 6 are respectively installed on a pair of flattening mechanisms 4. The drying mechanism 6 is triggered by the linkage mechanism 5 to dry the printed packaging film.

[0039] The packaging film is guided by multiple guide rollers 201 at one end and then wound onto the winding mechanism 101. When printing is required on the packaging film, the telescopic cylinder 301 is extended, causing the printing unit 3, the flattening mechanism 4, the linkage mechanism 5, and the drying mechanism 6 to descend. Simultaneously, the flattening mechanism 4, under the influence of gravity, can press the packaging film before the printing unit 3, such as... Figure 8As shown, at this time, the flattening mechanism 4 can press the packaging film on both sides of the printing section 3 to prevent wrinkles from appearing during printing. When the flattening mechanism 4 contacts the packaging film, if the printing section 3 continues to descend, the flattening mechanism 4 can move relative to the side wall of the printing section 3 until the printing section 3 contacts the packaging film, completing the printing.

[0040] During the relative movement of the printing section 3 and the flattening mechanism 4, the linkage mechanism 5 can be triggered, causing the drying mechanism 6 to descend closer to the packaging film. The drying mechanism 6 operates while the printing section 3 is printing. When the printing section 3 completes printing and rises, because the printing section 3 and the flattening mechanism 4 can move relative to each other, the flattening mechanism 4 continues to press down on the packaging film, and the drying mechanism 6 rises slowly. During this slow ascent, the printed area of ​​the packaging film is dried, accelerating the drying efficiency of the printing ink and preventing subsequent ink flow or wiping issues.

[0041] When the printing section 3 rises to a certain height, the printing section 3 drives the flattening mechanism 4 and the drying mechanism 6 to rise. At this time, the flattening mechanism 4 disengages from pressing the packaging film.

[0042] like Figures 1 to 9 As shown, the flattening mechanism 4 includes a mounting plate 401, a pair of guide rods 402, a linkage plate 403, a pair of guide grooves 404, a pair of connecting rods 405, and a pressing plate 406. The mounting plate 401 is bolted to the printing section 3. The pair of guide rods 402 are fixedly connected to the lower end face of the mounting plate 401. The linkage plate 403 is slidably disposed between the pair of guide rods 402. The pair of guide grooves 404 are mounted on the side wall of the printing section 3, and the linkage plate 403 is slidably connected to the guide grooves 404. The pair of connecting rods 405 are fixedly connected to the lower end face of the linkage plate 403. The pressing plate 406 is fixedly connected to the end of the connecting rod 405 away from the linkage plate 403. The mounting plate 401 is bolted to the printing section 3, ensuring a secure connection between the mounting plate 401 and the printing section 3. The linkage plate 403 slides on the guide rod 402, which allows the pressure plate 406 to move relative to the printing section 3. That is, the pressure plate 406 can contact the packaging film before the printing section 3 to press the packaging film. Then the printing section 3 continues to descend, and the linkage plate 403 slides on the guide rod 402 until the printing section 3 contacts the packaging film to complete the printing.

[0043] The guide groove 404 serves to stabilize the linkage plate 403, ensuring its stability during vertical sliding. The pressure plate 406 is connected to the linkage plate 403 via a connecting rod 405, thus connecting the linkage plate 403, connecting rod 405, and pressure plate 406 into a whole. The pressure plate 406 is used to press the packaging film, preventing wrinkles in the packaging film during printing by the printing unit 3.

[0044] The lower end of the guide rod 402 is connected to a limit ring, the diameter of which is larger than that of the guide rod 402. The limit ring serves to limit movement and prevent the linkage plate 403 from sliding off the guide rod 402.

[0045] In this embodiment, the length of the guide groove 404 is less than the height of the printing part 3 and greater than the length of the guide rod 402, which can limit the displacement distance between the pressure plate 406 and the printing part 3.

[0046] In addition, the distance between the pair of pressure plates 406 is greater than the width of the printing section 3, and the pressure plates 406 are made of metal. This design ensures the effective pressing of the pressure plates 406 onto the packaging film.

[0047] like Figures 1 to 9 As shown, the linkage plate 403 has a groove, and the linkage mechanism 5 includes a rotating shaft 501, a pair of gears 502, and a pair of racks 503. The rotating shaft 501 is rotatably connected to the groove. The pair of gears 502 are fixedly connected to the rotating shaft 501. The pair of racks 503 are both fixedly connected to the side wall of the printing section 3. The racks 503 are coplanar with the guide grooves 404 and are located between the pair of guide grooves 404. The racks 503 mesh with the gears 502, that is... Figure 7 As shown. When the linkage plate 403 moves relative to the side wall of the printing section 3, the rotating shaft 501 can rotate because the gear 502 meshes with the rack 503, and the gear 502 is rotatably mounted on the linkage plate 403, while the rack 503 is fixedly mounted on the side wall of the printing section 3.

[0048] like Figures 1 to 9 As shown, the drying mechanism 6 includes a pair of winding reels 601, a pull rope 602, and a drying hood 603. The pair of winding reels 601 are positioned between a pair of gears 502. The pull rope 602 is wound around the winding reels 601. The drying hood 603 is located on the upper side of the linkage plate 403. One end of the pull rope 602 is connected to the drying hood 603. The drying hood 603 has a mounting groove on the side near the printing section 3, in which a drying assembly 604 is installed. The winding reels 601 are used to wind the pull rope 602, and the pull rope 602 is used to pull the drying hood 603, thereby controlling the raising and lowering of the drying hood 603. The drying hood 603 is used to mount the drying assembly 604. The drying assembly 604 is used to dry the printed area of ​​the packaging film.

[0049] When the rotating shaft 501 rotates, the winding reel 601 can rotate synchronously. When the linkage plate 403 descends relative to the printing section 3, the winding reel 601 can release the pull rope 602, and the drying hood 603 can descend and approach the packaging film. When the linkage plate 403 rises relative to the printing section 3, the winding reel 601 can wind the pull rope 602 and raise the drying hood 603.

[0050] The drying assembly 604 only starts operating when the drying hood 603 approaches the packaging film. The operating drying assembly 604 can dry the printing ink on the packaging film to accelerate the drying efficiency of the printing ink and prevent the printing ink from flowing or being wiped off.

[0051] The pressure plate 406 has a cavity 4061 inside. Each of the two pressure plates 406 has multiple air holes 4062 on the side that is close to each other. The cavity 4061 is connected to the outside through the air holes 4062.

[0052] like Figures 1 to 9 As shown, the preparation apparatus also includes an air blowing mechanism 7, which includes an impeller 701, an outer cover 702, and an air delivery pipe 704. The impeller 701 is mounted on a rotating shaft 501, and a pair of pull ropes 602 are symmetrical about the impeller 701. The outer cover 702 is located outside the impeller 701, and the impeller 701 is rotatably connected to the rotating shaft 501 and fixedly connected to the linkage plate 403. An air exchange section 703 is provided on the outer cover 702. One end of the air delivery pipe 704 is located inside the outer cover 702, and the other end is located inside the cavity 4061. The impeller 701 rotates with the rotating shaft 501, generating airflow. The outer cover 702 is used to cover the impeller 701, thus protecting it. The air exchange section 703 is used to balance the air pressure. The air delivery pipe 704 is used to deliver the air generated when the impeller 701 rotates.

[0053] When the shaft 501 rotates, it drives the impeller 701 to rotate. The rotating impeller 701 generates air, which is delivered to the cavity 4061 through the air pipe 704 and ejected through the air hole 4062, blowing towards the printing area of ​​the packaging film.

[0054] With this configuration, the impeller 701 rotates and generates airflow as the linkage plate 403 rises or falls relative to the printing section 3. Specifically, when the linkage plate 403 rises relative to the printing section 3 (i.e., during the descent of the printing section 3), the airflow generated by the rotating impeller 701 blows towards the packaging film below the printing section 3, removing any dust that may be present on the film and improving subsequent printing results. When the linkage plate 403 falls relative to the printing section 3 (i.e., during the descent of the printing section 3), the impeller 701 rotates in the opposite direction and generates airflow. This airflow disperses the heat generated by the drying assembly 604 towards the printing area of ​​the packaging film, aiding in the drying of the printing ink and preventing the heat from the drying assembly 604 from becoming too concentrated and damaging the packaging film.

[0055] In summary, this application uses multiple guide rollers 201 to initially fix the packaging film, and the printing unit 3 can then print on the packaging film. The pressure plate 406 presses down on both sides of the printed area of ​​the packaging film, preventing wrinkles during printing. The pressure plate 406 can be displaced relative to the printing unit 3, triggering the rotation of the shaft 501, which in turn causes the winding reel 601 to wind or release the pull cord 602. When the pull cord 602 is released, the drying hood 603 descends, and the drying assembly 604 approaches the packaging film to dry the printed area. When the pull cord 602 is wound, the drying hood 603 rises away from the packaging film. The rotation of the shaft 501 also causes the impeller 701 to rotate and generate airflow; the impeller 701 can rotate in both directions. When the printing unit 3 descends, the airflow generated by the rotating impeller 701 removes dust from the surface of the packaging film, ensuring good subsequent printing results. When the printing section 3 rises, the air generated by the rotation of the impeller 701 can disperse the heat generated by the drying component 604 towards the printing area of ​​the packaging film. This not only helps the printing ink to dry, but also prevents the heat generated by the drying component 604 from being too concentrated and damaging the packaging film.

[0056] like Figure 10 As shown, a process for preparing a moisture-proof food packaging composite film according to an embodiment of the present invention includes the following steps:

[0057] S1. The outer layer material, the intermediate layer material, and the inner layer material are melt-plasticized respectively. The outer layer material is polypropylene, the intermediate layer material includes ethylene-vinyl alcohol copolymer and 0.5-3 wt% melt-reactive crosslinking agent, and the inner layer material is modified polyethylene. The thickness of the intermediate layer material accounts for 10%-25% of the total thickness of the composite film.

[0058] S2. The melt layers obtained in S1 are introduced into the multi-layer co-extrusion die head to merge and form a composite melt;

[0059] S3. In the multi-layer co-extrusion die or in the melt flow channel adjacent to its outlet, control the temperature at 180-210°C to allow the ethylene-vinyl alcohol copolymer in the intermediate layer material to undergo an in-situ crosslinking reaction with the melt reactive crosslinking agent for 15-90 seconds.

[0060] S4. The composite melt that has undergone in-situ crosslinking reaction is cooled and shaped by casting or blowing to obtain a composite film;

[0061] S5. Printing and winding the shaped composite film, wherein the printing device is the moisture-proof food packaging composite film preparation device mentioned above.

[0062] Among them, the melt-reactive crosslinking agent in S1 is a multifunctional epoxy polymer.

[0063] In addition, after the composite melt cools and solidifies, the process includes an online heat treatment step for the composite film, with a heat treatment temperature of 70-110°C and a time of 5-60 seconds.

[0064] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure 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 this disclosure 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 this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for preparing a moisture-proof food packaging composite film, characterized in that, include: A base platform on which a winding mechanism is mounted; The outer casing is mounted on the base and located on the front side of the winding mechanism. Multiple guide rollers are installed inside the outer casing. The printing unit is installed inside the housing and located on the upper side of the base. A pair of telescopic cylinders are installed on the housing, and the free ends of the telescopic cylinders are connected to the printing unit. A pair of flattening mechanisms are symmetrically installed on a pair of side walls of the printing section. Under the action of gravity, the flattening mechanisms can press the packaging film before the printing section and move relative to each other along the side walls of the printing section. A pair of linkage mechanisms are respectively installed on a pair of flattening mechanisms, and can be triggered when the flattening mechanisms move relative to each other along the side wall of the printing section; A pair of drying mechanisms are respectively installed on a pair of flattening mechanisms. The drying mechanisms are triggered by a linkage mechanism to dry the printed packaging film.

2. The apparatus for preparing a moisture-proof food packaging composite film according to claim 1, characterized in that, The flattening mechanism includes: Mounting plate, which is bolted to the printed part; A pair of guide rods are fixedly connected to the lower end face of the mounting plate; A linkage plate is slidably disposed between a pair of guide rods; A pair of guide grooves are installed on the side wall of the printing section, and the linkage plate is slidably connected to the guide grooves; A pair of connecting rods are fixedly connected to the lower end face of the linkage plate; A pressure plate is fixedly connected to the end of the connecting rod away from the linkage plate.

3. The apparatus for preparing a moisture-proof food packaging composite film according to claim 2, characterized in that, The lower end of the guide rod is connected to a limiting ring, and the diameter of the limiting ring is larger than the diameter of the guide rod.

4. The apparatus for preparing a moisture-proof food packaging composite film according to claim 2, characterized in that, The length of the guide groove is less than the height of the printing section, but greater than the length of the guide rod.

5. The apparatus for preparing a moisture-proof food packaging composite film according to claim 2, characterized in that, The distance between the pair of pressure plates is greater than the width of the printing section, and the pressure plates are made of metal.

6. The apparatus for preparing a moisture-proof food packaging composite film according to claim 2, characterized in that, The linkage plate is provided with a groove, and the linkage mechanism includes: The rotating shaft is rotatably connected within the groove. A pair of gears are fixedly connected to the rotating shaft; A pair of racks are fixedly connected to the side wall of the printing section. The racks are coplanar with the guide grooves and are located between the pair of guide grooves. The racks mesh with gears.

7. The apparatus for preparing a moisture-proof food packaging composite film according to claim 6, characterized in that, The drying mechanism includes: A pair of winding reels, the pair of winding reels being disposed between a pair of gears; The pull rope is wound around the winding reel; A drying hood is located on the upper side of the linkage plate. One end of the pull rope is connected to the drying hood. The side of the drying hood near the printing section is provided with a mounting groove, and a drying component is installed in the mounting groove.

8. The apparatus for preparing a moisture-proof food packaging composite film according to claim 7, characterized in that, The pressure plate has a cavity inside, and each of the two pressure plates has multiple air holes on the side that is close to each other. The cavity is connected to the outside through the air holes.

9. The apparatus for preparing a moisture-proof food packaging composite film according to claim 8, characterized in that, The preparation apparatus further includes an air blowing mechanism, which comprises: An impeller is mounted on the rotating shaft, and a pair of the pull ropes are symmetrical about the impeller; An outer cover is provided on the outside of the impeller. The impeller is rotatably connected to the rotating shaft and fixedly connected to the linkage plate. An air exchange section is provided on the outer cover. The gas supply pipe has one end located inside the outer cover and the other end located inside the cavity.

10. A method for preparing a moisture-proof food packaging composite film, using the preparation apparatus according to any one of claims 1-9, characterized in that, Includes the following steps: S1. The outer layer material, the middle layer material and the inner layer material are melted and plasticized respectively. The outer layer material is polypropylene, the middle layer material includes ethylene-vinyl alcohol copolymer and 0.5-3 wt% melt-reactive crosslinking agent, and the inner layer material is modified polyethylene. S2. The melt layers obtained in S1 are introduced into the multi-layer co-extrusion die head to merge and form a composite melt; S3. In the melt flow channel inside the multi-layer co-extrusion die or adjacent to its outlet, the temperature is controlled at 180-210°C to allow the ethylene-vinyl alcohol copolymer in the intermediate layer material to undergo an in-situ crosslinking reaction with the melt reactive crosslinking agent for 15-90 seconds. S4. The composite melt that has undergone in-situ crosslinking reaction is cooled and shaped by casting or blowing to obtain a composite film; S5. Printing and winding the shaped composite film, wherein the printing device is the moisture-proof food packaging composite film preparation device according to any one of claims 1-9.

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