Preparation method and preparation system for in-film net-making film

Abstract

The invention provides an in-film net-making film preparation method and system, and the method comprises the following steps: S1, extruding a molten and plasticized raw material through a sawtooth-shaped die head to form a tubular film bubble with an inner convex strip on the inner wall; the sawtooth-shaped die head comprises an inner circle part and an outer ring part which are concentrically arranged; in the step S2, a rotary traction device arranged at the top pulls the tubular bubble to rotate upwards, so that the trend of an inner convex strip on the inner wall of the tubular bubble is spiral; in the step S3, the single-layer tubular film bubbles are folded or oppositely pressed, hot pressing is conducted through a heating pressing roller area, then cooling shaping is conducted through a cold water pressing roller area, a double-layer flat film is formed, and the inner protruding strips are overlapped in a crossed mode to form a film built-in net; and in the step S4, the double-layer flat film is directly wound on the top. The thickness of the film can be remarkably reduced, the raw material cost of film preparation is reduced, and meanwhile good film physical performance is kept.

Description

Technical Field

[0001] The present invention relates to the field of thin film preparation, and specifically, to a method and a preparation system for preparing a film with an in-membrane mesh Background Art

[0002] Blown multi-layer co-extruded films are widely used in packaging, chemical industry, automotive, medical, and agricultural fields due to their flexible material combination and high cost performance. However, the films prepared by this process have significant anisotropic mechanical properties, and their longitudinal (MD) tensile strength is usually much higher than the transverse (TD) strength. To meet the application requirements of high strength and high toughness, the prior art achieves this by replacing high-strength materials. However, high-strength materials (such as special engineering plastics or modified resins) are costly, significantly increasing the usage cost for end-users. The prior art also increases the film thickness to improve the film strength and toughness, but increasing the thickness leads to an increase in material consumption, conflicting with the global "plastic limit and reduction" policy.

[0003] Under the above contradictions, the industry urgently needs a breakthrough technology that takes into account both the film strength and the preparation cost, avoiding reliance on high-cost materials or complex post-treatment processes. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a method and a preparation system for preparing a film with an in-membrane mesh, aiming to significantly reduce the film thickness, reduce the raw material cost of film preparation, and at the same time maintain good physical properties of the film.

[0005] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0006] According to the first aspect of the present invention, there is provided a method for preparing a film with an in-membrane mesh, including the following steps:

[0007] In step S1, the molten and plasticized raw material is extruded through a serrated die head to form a tubular film bubble with inner convex strips on the inner wall; the serrated die head includes an inner circular part and an outer ring part arranged concentrically, and an annular gap is formed between the inner circular part and the outer ring part; the inner circular part is also provided with a wind tunnel for blowing air upward to form a tubular film bubble; a plurality of saw teeth are arranged on the outer edge of the inner circular part.

[0008] In step S2, the rotary traction device arranged at the top pulls the tubular film bubble upward at a preset traction speed, and at the same time, the rotary traction device rotates 360° around its own axis at a preset rotation speed and drives the tubular film bubble to rotate, so that the inner convex strips on the inner wall of the tubular film bubble have a spiral upward trend.

[0009] In step S3, the composite winding device arranged at the top folds or presses the single-layer tubular film bubble. First, it is hot-pressed through the heating roller area, and then cooled and shaped through the cold water roller area to form a double-layer flat film. The inner convex strips cross and overlap to form an in-film network; the composite winding device rotates 360° around its own axis at the same rotational speed as the rotary traction device;

[0010] In step S4, the composite winding device directly winds the double-layer flat film at the top.

[0011] Preferably, in step S1, the sawteeth are square, the width of the sawteeth is greater than or equal to 1 mm and less than or equal to 300 mm, the length of the sawteeth is greater than or equal to 0.1 mm and less than or equal to 100 mm, and the gap between the sawteeth is greater than or equal to 0.5 mm and less than or equal to 300 mm.

[0012] Preferably, in step S3, the pressing pressure of the heating rollers in the heating roller area is adjustable, and the temperature and pressure of the heating rollers are controlled in stages according to the material characteristics; the cold water roller area consists of several cold water rollers with low-temperature liquid inside; the temperature and pressure of the heating rollers and cold water rollers can be uniformly controlled by the roller control device.

[0013] Preferably, in step S1, multiple independent extruders can be set to respectively convey raw materials of different functional layers for multi-layer co-extrusion.

[0014] Preferably, in step S2, the tubular film bubble is limited by arranging a limiting device outside the tubular film bubble, and an air-cooling device is arranged outside the tubular film bubble 2 for pre-cooling.

[0015] Preferably, according to the longitudinal and transverse strength requirements of the film, the values of the preset traction speed and the preset rotational speed are calculated and set, and the cross angle of each inner convex strip in the in-film network is adjusted by controlling the rising speed and the rotational speed of the tubular film bubble.

[0016] Preferably, in step S4, the tension of the double-layer flat film is controlled by a tension control device.

[0017] According to the second aspect of the present invention, there is provided a system for preparing a film with an in-film network, including: a serrated die head, a rotary traction device, and a composite winding device;

[0018] The serrated die head is used to extrude a tubular film bubble with inner convex strips on the inner wall. The serrated die head includes an inner circular part and an outer ring part, which are concentrically arranged. An annular gap is formed between the inner circular part and the outer ring part for extruding raw materials; an air hole is also arranged in the inner circular part for blowing air upward to form a tubular film bubble; a plurality of sawteeth are arranged on the outer edge of the inner circular part;

[0019] A rotary traction device is used to traction a tubular film bubble to rotate and rise at the top. The rotary traction device tractions the tubular film bubble to move upward according to a preset traction speed, and at the same time rotates 360° according to a preset rotation speed and drives the tubular film bubble to rotate, so that the inner convex strips on the inner wall of the tubular film bubble have a spiral upward trend.

[0020] A composite winding device is used to fold or press a single-layer tubular film bubble to form a double-layer flat film, and the inner convex strips are cross-overlapped to form an in-film network, and the double-layer flat film is directly wound at the top. The composite winding device includes a heating press roller area and a cold water press roller area. The heating press roller area is composed of several heating press rollers, and the temperature and pressing pressure of the heating press rollers are adjustable. The cold water press roller area is composed of several cold water press rollers with low-temperature liquid inside. The composite winding device rotates 360° at the same rotation speed as the rotary traction device.

[0021] Preferably, it further includes:

[0022] A press roller control device is used to uniformly control the temperature and pressure of the heating press rollers and cold water press rollers.

[0023] A tension control device is used to control the tension of the double-layer flat film during the winding process of the double-layer flat film.

[0024] A limiting device is arranged outside the tubular film bubble to limit the tubular film bubble.

[0025] An air cooling device is used to pre-cool the tubular film bubble and cool it by air cooling before the tubular film bubble enters the composite winding device.

[0026] Preferably, the saw teeth are square, the width of the saw teeth is greater than or equal to 1 mm and less than or equal to 300 mm, the length of the saw teeth is greater than or equal to 0.1 mm and less than or equal to 100 mm, and the gap between the saw teeth is greater than or equal to 0.5 mm and less than or equal to 300 mm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] By extruding a tubular film bubble with inner convex strips on the inner wall, and traction it to rotate and rise at the top and then composite it into a flat double-layer film, the inner convex strips are cross-overlapped to form an in-film network, reducing the film thickness on the premise of ensuring the physical properties of the finished film, and greatly saving the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects and advantages of the present invention will become more obvious:

[0030] Figure 1 It is a schematic structural diagram of the sawtooth die head described in Embodiment 1;

[0031] Figure 2 It is a schematic diagram of the principle of the method in Example 1;

[0032] Figure 3 It is a schematic flow diagram of the method described in Example 1.

[0033] As shown in the figure:

[0034] 1 - Serrated die head; 11 - Inner circular part; 12 - Outer ring part; 13 - Air duct; 14 - Annular gap; 15 - Saw teeth;

[0035] 2 - Tubular film bubble; 21 - Inner convex strip;

[0036] 3 - Rotary traction device;

[0037] 4 - Limiting device;

[0038] 5 - Air cooling device;

[0039] 6 - Composite winding device; 61 - Heating pressure roller; 62 - Cold water pressure roller; 63 - Winding guide roller. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0042] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, all directional indications (such as up, down, left, right, front, back, bottom, top...) in the present application are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0043] Example 1

[0044] This embodiment provides a method for preparing a thin film with an in-membrane network, as Figure 3 shown, which includes the following steps:

[0045] In step S1, the raw material is extruded through a serrated die head 1 to form a tubular film bubble 2. After the raw material is melted and plasticized, it is extruded through the serrated die head 1 arranged at the lower part and extends to form a tubular film bubble 2 with inner convex strips 21 on the inner wall.

[0046] Specifically, as Figure 1 shown, the serrated die head 1 includes an inner circular part 11 and an outer ring part 12. The inner circular part 11 and the outer ring part 12 are concentrically arranged, and an annular gap 14 is formed therebetween for extruding the raw material. The inner circular part 11 is also provided with a wind tunnel 13 for blowing air upward to form a tubular film bubble 2. A plurality of saw teeth 15 are arranged on the outer edge of the inner circular part 11, so that when the raw material is extruded from the annular gap 14, concave and convex lines are formed on the inner circle, so that the inner wall of the tubular film bubble 2 bulges inward to form inner convex strips 21.

[0047] Furthermore, the size of the saw teeth 15 will affect the shape, size and density of the inner convex strips 21, thereby affecting the longitudinal and transverse tensile strength of the in-membrane network. To improve the strength of the finished thin film, the saw teeth 15 are preferably square, and the size is: the width of the saw teeth is greater than or equal to 1 mm and less than or equal to 300 mm, the length of the saw teeth is greater than or equal to 0.1 mm and less than or equal to 100 mm, and the gap between the saw teeth is greater than or equal to 0.5 mm and less than or equal to 300 mm.

[0048] Furthermore, multiple independent extruders can be set to separately convey raw materials of different functional layers, so as to achieve multi-layer co-extrusion including an inner layer, a middle layer, an outer layer and an additional layer, meeting the use requirements of the thin film.

[0049] In step S2, the tubular film bubble 2 is rotated and pulled upward at the top. As Figure 2 shown, after the tubular film bubble 2 is extruded from the serrated die head 1 arranged at the lower part, it is rotated and stretched by a rotary traction device 3 and moves upward in a rotating manner, so as to change the orientation of the inner convex strips 21 on the inner wall of the tubular film bubble 2. Specifically, when the tubular film bubble 2 is extruded from the lower serrated die head 1, the inner wall is provided with parallel inner convex strips 21; the rotary traction device 3 arranged at the top pulls the tubular film bubble 2 upward at a preset traction speed; at the same time, the rotary traction device 3 rotates 360° at a preset rotation speed. The rotary traction device 3 clamps the upper part of the tubular film bubble 2, so that the tubular film bubble 2 rotates, and further makes the orientation of the inner convex strips 21 on the inner wall of the tubular film bubble 2 spiral upward.

[0050] Furthermore, a limiting device 4 can be arranged outside the tubular film bubble 2 to limit the tubular film bubble 2 and prevent it from being skewed and damaged during the rotation and upward movement.

[0051] In step S3, the single-layer tubular film vesicles 2 are subjected to double-layer film lamination and hot-pressed into shape. The tubular film vesicles 2 are drawn by the rotary traction device 3 to reach the composite winding device 6 arranged at the top. The single-layer tubular film vesicles 2 are folded or pressed against each other to form a double-layer flat film, and the inner convex strips 21 cross and overlap to form an internal film network. The composite winding device 6 rotates 360° around its own axis at the same rotational speed as the rotary traction device 3 to prevent the single-layer tubular film vesicles 2 from being torn or wrinkled during the double-layer film lamination process.

[0052] Furthermore, the composite winding device 6 includes a heating press roller area and a cold water press roller area. The heating press roller area is used for hot melt bonding of interfaces and consists of several heating press rollers 61 with adjustable temperatures. The pressing pressure between the heating press rollers is adjustable, and the temperature and pressure of the heating press rollers are controlled in stages according to the material properties. The cold water press roller area consists of several cold water press rollers 62 filled with low-temperature liquid, which is used for rapid cooling and shaping of the double-layer flat film to ensure the interlayer bonding strength and dimensional stability. The single-layer tubular film vesicles 2 are folded or pressed against each other, first hot-pressed through the heating press roller area, and then cooled and shaped through the cold water press roller area to form a double-layer flat film. The temperatures and pressures of the heating press rollers 61 and the cold water press rollers 62 can be uniformly controlled by a press roller control device (not shown in the figure) to enhance the efficiency of film lamination and the quality of the finished product.

[0053] Furthermore, before the tubular film vesicles 2 enter the composite winding device, they are pre-cooled. For example, an air-cooling device 5 can be arranged outside the tubular film vesicles 2 to cool them by air.

[0054] Furthermore, according to the longitudinal and transverse strength requirements of the film, the values of the corresponding preset traction speed and preset rotational speed can be calculated and set. By controlling the rising speed and rotational speed of the tubular film vesicles 2, the crossing angle of each inner convex strip 21 in the internal film network is adjusted, so as to form the grid shape of the internal film network that best meets the film usage requirements and satisfy the film strength requirements.

[0055] In step S4, the double-layer flat film is wound at the top. The double-layer flat film produced in step 3 is directly wound at the top under traction, rather than being drawn to the lower part for winding. This can save redundant moving distances, reduce the risk of film breakage caused by sudden changes in film tension, and also reduce the floor area and energy consumption of the equipment, making the production line layout more compact. Specifically, as Figure 2 shown, step 4 is directly completed by the composite winding device 6: the single-layer tubular film vesicles 2 are first hot-pressed through the heating press roller area and then cooled and shaped through the cold water press roller area to form a double-layer flat film, and continue to be directly wound at the top under the rotation of the winding guide roller 63.

[0056] Further, during the winding process, the tension of the double-layer flat film can be controlled by a tension control device (not shown in the figure) to avoid wrinkles or stretching deformation during the winding process.

[0057] Optionally, the double-layer flat film can be post-processed according to actual needs, such as corona treatment, coating treatment, etc. on the film surface, so as to improve printing or composite performance and meet the diverse film usage requirements.

[0058] To verify the physical properties of the film prepared by the method of this embodiment, a test sample A was made using the method described in this embodiment for testing. The raw material formula used to prepare test sample A is: 60% low-density polyethylene (LDEP) of model 2426H, 38% linear low-density polyethylene (LLDPE) of model 7042, 1% anti-aging agent, and 1% antiblocking agent.

[0059] The mass per unit area of test sample A was measured. According to the test method of ISO9864:2005, in a laboratory environment with a temperature of 23(±2)°C and a humidity of 50(±5)%RH, the mass per unit area result of the test sample A was measured to be 32 g / m² using an XP204 type electronic balance.

[0060] The thickness of test sample A was measured. According to the test method of ISO4593:1993, in a laboratory environment with a temperature of 23(±2)°C and a humidity of 50(±5)%RH, under a load of 0.8 N, using a TG-3130-A3 digital desktop thickness gauge, the thickness of the non-film built-in mesh area (plain surface) of the test sample A was measured to be 0.024 mm, and the thickness of the film built-in mesh area (ribbed surface) was measured to be 0.094 mm.

[0061] The tensile test was carried out on the test sample A. The test method was ISO527-3:2018, the laboratory environment temperature was 23(±2)°C, the humidity was 50(±5)%RH, the specimen type was type 2, the specimen width was 15 mm, the specimen thickness (transverse) was 0.061 mm, the specimen thickness (longitudinal) was 0.065 mm, the test speed was 500 mm / min, the gauge length was 50 mm, the initial clamp spacing was 100 mm, and the test equipment was a single-arm tensile machine (model BT2-FZ2.5TH.D16.001). Finally, the tensile strength (transverse) of test sample A was measured to be 13.3 MPa, the tensile strength (longitudinal) was 27.5 MPa, the elongation at break (transverse) was 652%, and the elongation at break (longitudinal) was 191%.

[0062] The dart impact strength test was carried out on the test sample A. The test method was ISO7765-1:1988 (Method A). The laboratory environmental temperature was 23(±2)°C, the humidity was 50(±5)%RH, the thickness of the test specimen was 0.075 mm, the test equipment was a dart impact tester (model FDI-01), and finally the impact breakage mass was measured to be less than 35 g.

[0063] According to the foregoing test results, it can be known that the film with an internal network prepared by the method provided in this embodiment can still ensure good physical properties while reducing the film thickness, greatly saving the preparation cost.

[0064] Example 2

[0065] This embodiment provides a film preparation system with an internal network. Through the mutual cooperation of the various components of the system, it can realize the film preparation method with an internal network described in Example 1. The system provided in this embodiment includes: a serrated die head, a rotary traction device, and a composite winding device. Among them:

[0066] The serrated die head is used to extrude a tubular film bubble with internal convex strips on the inner wall. The serrated die head includes an inner circular part and an outer ring part. The inner circular part and the outer ring part are concentrically arranged. An annular gap is formed between the inner circular part and the outer ring part for extruding the raw material. The inner circular part is also provided with a wind hole for blowing air upward to form a tubular film bubble. A number of serrations are provided on the outer edge of the inner circular part. Further, the serrations are preferably square, and the dimensions are: the serration width is greater than or equal to 1 mm and less than or equal to 300 mm, the serration length is greater than or equal to 0.1 mm and less than or equal to 100 mm, and the serration gap is greater than or equal to 0.5 mm and less than or equal to 300 mm.

[0067] The rotary traction device is used to traction the tubular film bubble to rotate and rise at the top. When the tubular film bubble is extruded from the lower serrated die head, the inner wall has parallel internal convex strips. The rotary traction device arranged at the top traction the tubular film bubble to move upward at a preset traction speed; at the same time, the rotary traction device rotates 360° around its own axis at a preset rotation speed, so that the tubular film bubble rotates, and then the direction of the internal convex strips 21 on the inner wall of the tubular film bubble is helically rising.

[0068] The composite winding device is used to fold or press a single-layer tubular film bubble to form a double-layer flat film, the inner convex strips are cross-overlapped to form a network inside the film, and the double-layer flat film is directly wound at the top. The composite winding device includes a heating press roller area, a cold water press roller area, and a winding guide roller. After the tubular film bubble enters the composite winding device, it will pass through the heating press roller area and the cold water press roller area in sequence, and is directly wound at the top under the rotation of the winding guide roller. The heating press roller area is composed of several heating press rollers with adjustable temperatures, and the temperature and pressing pressure of the heating press rollers are adjustable; the cold water press roller area is composed of several cold water press rollers with low-temperature liquid inside. The composite winding device rotates 360° self-rotation at the same rotation speed as the rotary traction device to prevent the single-layer tubular film bubble from being torn or wrinkled during the double-layer film composite.

[0069] The system provided in this embodiment further includes a press roller control device for uniformly regulating the temperature and pressure of the heating press rollers and the cold water press rollers to enhance the efficiency of film composite and the quality of finished products.

[0070] The system provided in this embodiment further includes a tension control device for controlling the tension of the double-layer flat film during the winding process of the double-layer flat film to prevent wrinkles or stretching deformation during the winding process.

[0071] The system provided in this embodiment further includes a limiting device arranged outside the tubular film bubble to limit the tubular film bubble to prevent it from being skewed and damaged during the rotating upward process.

[0072] The system provided in this embodiment further includes an air-cooling device for pre-cooling the tubular film bubble and cooling it by air cooling before the tubular film bubble enters the composite winding device.

[0073] It should be noted that the explanations of the various implementation manners and beneficial effects described in the above-mentioned Embodiment 1 also apply to this embodiment. To avoid redundancy, no detailed elaboration will be made here.

[0074] The specific embodiments of the present invention have been described above. Through the above description, relevant staff can make various changes and modifications completely within the scope not deviating from the technical idea of this invention.

Claims

1. A method for preparing an in-film mesh film, characterized in that: The steps include: In step S1, the molten plasticized raw material is extruded through a sawtooth die head to form a tubular film bubble having an inner wall with inner convex strips; the sawtooth die head comprises an inner circular part and an outer ring part arranged concentrically, and an annular gap is formed between the inner circular part and the outer ring part; the inner circular part is also provided with a wind tunnel, and the wind tunnel blows air upward to form a tubular film bubble; the outer edge of the inner circular part is provided with a plurality of saw teeth; In step S2, the rotating traction device arranged at the top pulls the tubular film bubble upward at a preset traction speed, and at the same time, the rotating traction device rotates 360 degrees at a preset rotation speed and drives the tubular film bubble to rotate, so that the inner convex strips on the inner wall of the tubular film bubble are spirally ascending; In step S3, the composite winding device arranged at the top folds or presses the single-layer tubular film bubble, first passes through the heated pressing roller area for heat pressing, and then passes through the cold water pressing roller area for cooling and shaping, to form a double-layer flat film, and the inner convex strips are cross-overlaid to form a film-embedded net; the composite winding device and the rotating traction device maintain the same rotation speed and rotate 360 ​​degrees; In step S4, the composite winding device directly winds up the double-layer flat film at the top.

2. The method for preparing an in-film mesh film according to claim 1, characterized in that: In step S1, the saw teeth are square, the saw tooth width is greater than or equal to 1 mm and less than or equal to 300 mm, the saw tooth length is greater than or equal to 0.1 mm and less than or equal to 100 mm, and the saw tooth gap is greater than or equal to 0.5 mm and less than or equal to 300 mm.

3. The method for preparing an in-film mesh film according to claim 1, characterized in that: In step S3, the pressing pressure of the heating roller in the heating roller zone is adjustable, and the temperature and pressure of the heating roller are controlled in stages according to the material properties; the cold water roller zone is composed of a number of cold water rollers with built-in low-temperature liquid; the temperature and pressure of the heating roller and the cold water roller can be uniformly controlled by a roller control device.

4. The method for preparing an in-film mesh film according to claim 1, characterized in that: In step S1, multiple independent extruders can be set up to respectively deliver raw materials of different functional layers to perform multi-layer co-extrusion.

5. The method for preparing an in-film mesh film according to claim 1, characterized in that: In step S2, the tubular film bubble is limited by providing a limiting device outside the tubular film bubble, and an air cooling device is provided outside the tubular film bubble to pre-cool it.

6. The method for preparing an in-film mesh film according to claim 1, characterized in that: According to the longitudinal and transverse strength requirements of the film, the corresponding preset traction speed and preset rotation speed are calculated and set, and the crossing angle of each inner convex strip in the membrane built-in net is adjusted by controlling the rising speed and rotation speed of the tubular membrane bubble.

7. The method for preparing an in-film mesh film according to claim 1, characterized in that: In step S4, the tension of the double-layer flat film is controlled by a tension control device.

8. An in-film mesh film preparation system, characterized in that: include: Sawtooth die head, rotary traction device, composite winding device; The sawtooth die head is used to extrude a tubular film bubble with inner convex strips on the inner wall. The sawtooth die head includes an inner circular part and an outer ring part. The inner circular part and the outer ring part are arranged concentrically. An annular gap is formed between the inner circular part and the outer ring part for extruding the raw material. The inner circular part is also provided with a wind tunnel for blowing air upward to form a tubular film bubble. The outer edge of the inner circular part is provided with a plurality of saw teeth. A rotating traction device is used to pull the tubular film bubble at the top to rotate and rise; the rotating traction device pulls the tubular film bubble upward according to a preset traction speed, and at the same time rotates 360 degrees at a preset rotation speed and drives the tubular film bubble to rotate, so that the inner convex strips on the inner wall of the tubular film bubble are in a spiral upward direction; The composite winding device is used to fold or press a single-layer tubular film bubble to form a double-layer flat film, the inner convex strips are cross-overlapped to form a film-built-in net, and the double-layer flat film is directly wound up on the top; the composite winding device includes a heating roller area and a cold water roller area; the heating roller area is composed of a plurality of heating rollers, and the temperature and pressing pressure of the heating rollers are adjustable; the cold water roller area is composed of a plurality of cold water rollers with built-in low-temperature liquid; the composite winding device and the rotating traction device maintain the same rotation speed and rotate 360°.

9. The in-film web-making film preparation system according to claim 8, characterized in that: Also includes: A pressure roller control device, used for uniformly controlling the temperature and pressure of the heating pressure roller and the cold water pressure roller; A tension control device, used for controlling the tension of the double-layer flat film during the winding process of the double-layer flat film; A limiting device is arranged outside the tubular film bubble to limit the position of the tubular film bubble; The air cooling device is used to pre-cool the tubular film bubble before it enters the composite winding device and cool it by air.

10. The in-film web-making film preparation system according to claim 8, characterized in that: The saw teeth are square, with a saw tooth width greater than or equal to 1 mm and less than or equal to 300 mm, a saw tooth length greater than or equal to 0.1 mm and less than or equal to 100 mm, and a saw tooth gap greater than or equal to 0.5 mm and less than or equal to 300 mm.

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