A cast film production vacuum extraction structure

Abstract

This utility model discloses a vacuum structure for cast film production, relating to the field of cast film production technology. It solves the technical problem that during high-temperature extrusion of plastic melt, small amounts of low-molecular-weight substances and volatile components such as moisture evaporaters are released, and that moisture in the air forms water droplets upon contact with the cooling roller surface, affecting the quality of the cast film. This utility model includes an extruder with an extrusion lip at its lower end. A cooling roller is fitted below the extrusion lip, and a sealing assembly is also provided at the lower part of the extruder. The width of the sealing assembly matches the width of the cooling roller. The sealing assembly, together with the cooling roller and the extruded melt curtain from the extrusion lip, forms a sealed space. An internal pipe of the sealing assembly is connected to a vacuum pump. The purpose is to actively extract air through the vacuum pump, preventing air from being trapped between the melt and the cooling roller surface. Furthermore, the insulating effect of air eliminates moisture, low-molecular-weight substances, and moisture evaporaters, thereby improving the production efficiency of the cast film.

Description

Technical Field

[0001] This utility model belongs to the field of cast film production technology, specifically relating to a vacuum structure for cast film production. Background Technology

[0002] Cast film is a process for producing plastic film by casting and rapid cooling of melt. Its basic principle is to melt and plasticize thermoplastic granules in an extruder, and then extrude them into a sheet-like melt curtain through the extrusion lip. Subsequently, it is rapidly cooled and solidified while closely adhering to the surface of the cooling roller. Finally, it is drawn and wound to obtain the finished film. The performance of cast film depends to a large extent on the initial cooling effect of the melt on the cooling roller.

[0003] In the traditional cast film production process, ensuring a completely tight adhesion between the melt curtain and the surface of the high-gloss cooling roller is a key technical challenge. If the adhesion is not tight, air gaps will exist between the two, which will seriously degrade the film quality. During the high-temperature extrusion process, the plastic melt will release a small amount of low-molecular-weight substances, water vapor, and other volatile components, which will condense and adhere to the roller surface, forming tiny precipitates. When the temperature of the cooling roller surface is lower than the dew point temperature of the ambient air, water vapor in the air will condense into tiny water droplets on its surface, affecting the production quality of the cast film. Utility Model Content

[0004] To address the aforementioned technical problems, this utility model provides a vacuum structure for casting film production. By actively evacuating air using a vacuum pump, it prevents air from being trapped between the melt and the cooling roller. Furthermore, air has an insulating effect; eliminating air allows the melt's heat to be directly and unimpededly transferred to the cooling roller, achieving rapid and uniform cooling. This reduces the film's crystallinity, increases its transparency, and enhances its gloss. The negative pressure environment created by the sealing component effectively removes low-molecular-weight substances and volatiles such as moisture released from the heated plastic melt, preventing them from condensing on the cooling roller surface and being transferred onto the casting film, thus avoiding surface defects. Because the sealing component is in a vacuum state, moisture condensation is prevented at the contact points between the melt curtain and the cooling roller, facilitating further temperature adjustment and reduction on the cooling roller surface. This allows for uniform and rapid cooling of the melt curtain, improving the film's dimensional stability and mechanical property consistency.

[0005] The technical solution adopted in this utility model is as follows:

[0006] A vacuum structure for casting film production includes an extruder, an extrusion lip at the lower end of the extruder, a cooling roller below the extrusion lip, a sealing assembly at the lower part of the extruder, the width of the sealing assembly matching the width of the cooling roller, the sealing assembly cooperating with the cooling roller and the melt curtain extruded from the extrusion lip to form a sealed space, and an internal pipe of the sealing assembly connected to a vacuum pump.

[0007] By employing the above technical solution, active air extraction via a vacuum pump prevents air from being trapped between the melt and the cooling roller surface. Furthermore, air has an insulating effect; eliminating air allows the melt's heat to be directly and unimpededly transferred to the cooling roller, achieving rapid and uniform cooling. This reduces film crystallinity, increases transparency, and enhances gloss. The negative pressure environment created by the sealing component effectively removes low-molecular-weight substances and volatiles such as moisture released from the heated plastic melt, preventing them from condensing on the cooling roller surface and being transferred to the cast film, thus avoiding surface defects. Because the sealing component is in a vacuum state, moisture condensation is prevented at the contact points between the melt curtain and the cooling roller, facilitating further temperature adjustment and reduction on the cooling roller surface. This allows for uniform and rapid cooling of the melt curtain, improving the film's dimensional stability and mechanical property consistency.

[0008] Furthermore, a filter is installed between the sealing assembly and the pipe connecting the vacuum pump to facilitate the removal of volatile substances from the gas by the vacuum pump, preventing these volatile substances from condensing in the pipe or vacuum pump and causing blockage or damage.

[0009] Preferably, the sealing assembly includes a first sealing plate, a second sealing plate, and two third sealing plates. The upper ends of the first sealing plate and the second sealing plate are respectively connected to the lower part of the extruder. The two third sealing plates are respectively disposed on both sides of the first sealing plate and the second sealing plate to form a box. One of the third sealing plates is provided with an interface, which is connected to the vacuum pump through a pipe.

[0010] Using the above technical solution, the first sealing plate and the second sealing plate form a seal in the width direction of the cooling roller, and the two third sealing plates form a seal in the direction perpendicular to the first sealing plate, thereby forming a box structure together with the surface of the cooling roller to form a complete, sealed chamber surrounding the attachment point. The interface is set on the third sealing plate, providing a reasonable and convenient position for the connection of the vacuum pipeline, avoiding pipeline interference with the melt curtain or other components.

[0011] Preferably, the first sealing plate is located in the outflow direction of the melt curtain, and the distance between the lower end of the first sealing plate and the cast film formed on the cooling roller by the melt curtain is between 0 and 50 μm, that is, the distance between the lower end of the first sealing plate and the cooling roller is equal to the thickness of the cast film.

[0012] By adopting the above technical solution, the distance between the lower end of the first sealing plate and the cast film is between 0 and 50 μm. The extremely small gap ensures that the formed film can be continuously and stably removed from the vacuum chamber without being scratched or blocked. The tiny gap greatly limits the flow rate of external air back into the vacuum chamber from the position of the first sealing plate. Combined with the pumping speed of the vacuum pump, the negative pressure in the chamber can be easily maintained, achieving effective sealing under dynamic conditions. At the same time, it avoids direct friction and wear between the first sealing plate and the high-precision cooling roller surface.

[0013] Preferably, the second sealing plate is located on the side of the melt curtain away from the first sealing plate, and the lower end of the second sealing plate is in close contact with the cooling roller.

[0014] By adopting the above technical solution, the second sealing plate is closely attached to the cooling roller, which isolates external air from being brought into the vacuum chamber from the second sealing plate to the greatest extent.

[0015] Preferably, the third sealing plates on both sides are in sealing contact with the side edges of the cooling rollers on the corresponding sides.

[0016] By adopting the above technical solution, the two sides of the vacuum chamber are sealed, preventing air from being drawn in from both sides of the cooling roller, and ensuring a uniform negative pressure environment across the entire width of the cooling roller surface.

[0017] Preferably, each of the third sealing plates has a T-shaped slider at the lower end near the cooling roller, and T-shaped grooves are respectively provided at the two side edges of the cooling roller. The T-shaped grooves are annular and coaxial with the cooling roller.

[0018] Using the above technical solution, the slider and the groove cooperate to form a labyrinth seal, which effectively blocks the airflow. The T-shaped groove design allows the third sealing plate to have a small amount of floating space in the radial direction, avoiding jamming or wear, while also facilitating the installation and positioning of the first and second sealing plates.

[0019] Preferably, the lower part of the first sealing plate and the second sealing plate is configured as a curved surface that cooperates with the cooling roller.

[0020] By adopting the above technical solution, the lower part of the sealing plate is set as a curved surface that cooperates with the cooling roller, which can increase the fit between the sealing plate and the cooling roller surface, and facilitate the smooth flow of the melt curtain from the box of the sealing assembly.

[0021] Preferably, the lower part of the first sealing plate and the second sealing plate is provided with a contact portion, and the contact portion is made of high-performance engineering plastic material.

[0022] By adopting the above technical solution, high-performance engineering plastics have low coefficient of friction, high wear resistance and self-lubricating properties, which can minimize wear and scratches on the high-gloss cooling roller surface, resist chemical corrosion of plastic volatiles, and avoid sealing failure due to material deterioration.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are:

[0024] By actively evacuating air using a vacuum pump, air is prevented from being trapped between the melt and the cooling roller. Furthermore, air has an insulating effect; eliminating air allows the melt's heat to be directly and unimpededly transferred to the cooling roller, achieving rapid and uniform cooling. This reduces film crystallinity, increases transparency, and enhances gloss. The negative pressure environment created by the sealing assembly effectively removes low-molecular-weight substances and volatiles such as moisture released from the heated plastic melt, preventing them from condensing on the cooling roller surface and being transferred to the cast film, thus avoiding surface defects. Because the sealing assembly is in a vacuum state, moisture condensation is prevented at the contact points between the melt curtain and the cooling roller, facilitating further temperature adjustment and reduction on the cooling roller surface. This allows for uniform and rapid cooling of the melt curtain, improving the film's dimensional stability and mechanical property consistency. Attached Figure Description

[0025] This utility model will be described by way of example and with reference to the accompanying drawings, wherein:

[0026] Figure 1 This is a schematic diagram of a vacuum extraction structure for casting film production according to this utility model;

[0027] Figure 2 This is a utility model Figure 1 Enlarged structural diagram of part A in the middle;

[0028] Figure 3 This is a schematic diagram of the structure of the first sealing plate in this utility model.

[0029] Figure Labels

[0030] 1-Extruder, 2-Cooling roller, 3-Cast film, 4-First sealing plate, 5-Second sealing plate, 6-Third sealing plate, 7-Extrusion lip, 8-Contact part. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The following is combined with Figures 1-3 This utility model will be described in detail.

[0033] Example 1

[0034] A vacuum structure for casting film production, see attached. Figures 1-2 The extruder includes an extruder 1, with an extrusion lip 7 at its lower end. A cooling roller 2 is fitted below the extrusion lip 7. A sealing assembly is also provided at the lower part of the extruder 1, the width of which matches the width of the cooling roller 2. The sealing assembly, together with the cooling roller 2 and the melt curtain extruded from the extrusion lip 7, forms a sealed space. The internal pipe of the sealing assembly is connected to a vacuum pump. The vacuum pump actively evacuates air, preventing air from being trapped between the melt and the surface of the cooling roller 2. Furthermore, air has an insulating effect; eliminating air allows the heat of the melt to be directly transferred to the cooling roller 2 without obstruction. Roller 2 achieves rapid and uniform cooling, reducing film crystallinity, increasing transparency, and enhancing gloss. The negative pressure environment created by the sealing assembly effectively removes low-molecular-weight substances and volatiles such as moisture released from the heated plastic melt, preventing them from condensing on the surface of cooling roller 2 and being transferred onto the cast film 3, thus avoiding surface defects. Because the sealing assembly is in a vacuum state, moisture condensation is prevented at the corresponding parts where the melt curtain contacts the cooling roller 2, which facilitates further adjustment and reduction of the surface temperature of cooling roller 2. This allows the melt curtain to cool rapidly and uniformly, improving the dimensional stability and mechanical property consistency of the film.

[0035] In this embodiment, a filter is provided between the sealing component and the pipe connecting the vacuum pump to facilitate the removal of volatile substances from the gas by the vacuum pump, thereby preventing these volatile substances from condensing in the pipe or vacuum pump and causing blockage or damage.

[0036] Example 2

[0037] In this embodiment, the sealing assembly includes a first sealing plate 4, a second sealing plate 5, and two third sealing plates 6. The upper ends of the first sealing plate 4 and the second sealing plate 5 are respectively connected to the lower part of the extruder 1. The two third sealing plates 6 are respectively disposed on both sides of the first sealing plate 4 and the second sealing plate 5 to form a box. One side of the third sealing plate 6 is provided with an interface, which is connected to the vacuum pump through a pipe. The first sealing plate 4 and the second sealing plate 5 form a seal in the width direction of the cooling roller 2, and the two third sealing plates 6 form a seal in the direction perpendicular to the first sealing plate 4, thereby forming a box structure that together with the surface of the cooling roller 2 forms a complete, sealed chamber surrounding the attachment point. The interface is located on the third sealing plate 6, providing a reasonable and convenient position for connecting the vacuum pipe and avoiding interference of the pipe with the melt curtain or other components.

[0038] Example 3

[0039] In this embodiment, the first sealing plate 4 is located in the outflow direction of the melt curtain. The distance between the lower end of the first sealing plate 4 and the cast film 3 formed on the cooling roller 2 by the melt curtain is between 0 and 50 μm, that is, the distance between the lower end of the first sealing plate 4 and the cooling roller 2 is equal to the thickness of the cast film 3. The distance between the lower end of the first sealing plate 4 and the cast film 3 is between 0 and 50 μm. The extremely small gap ensures that the formed film can be continuously and stably removed from the vacuum chamber without being scratched or blocked. The tiny gap greatly limits the flow rate of external air backflowing into the vacuum chamber from the position of the first sealing plate 4. With the pumping speed of the vacuum pump, the negative pressure in the chamber can be easily maintained, achieving effective sealing under dynamic conditions. At the same time, it avoids direct friction and wear between the first sealing plate 4 and the surface of the high-precision cooling roller 2.

[0040] Example 4

[0041] In this embodiment, the second sealing plate 5 is located on the side of the melt curtain away from the first sealing plate 4, and the lower end of the second sealing plate 5 is closely attached to the cooling roller 2; the close attachment of the second sealing plate 5 to the cooling roller 2 maximizes the isolation of external air from being brought into the vacuum chamber from the second sealing plate 5.

[0042] Example 5

[0043] In this embodiment, the third sealing plates 6 on both sides are in sealing contact with the side edges of the cooling roller 2 on the corresponding sides; this achieves the sealing of both sides of the vacuum chamber, preventing air from being drawn in from both sides of the cooling roller 2, and ensuring that the negative pressure environment is uniform and consistent across the entire width of the cooling roller 2.

[0044] Example 6

[0045] In this embodiment, a T-shaped slider is provided at the lower end of each third sealing plate 6 near the cooling roller 2, and T-shaped grooves are provided at both sides of the cooling roller 2. The T-shaped grooves are annular and coaxial with the cooling roller 2. The slider and the groove cooperate to form a labyrinth seal, which effectively blocks the airflow. The T-shaped groove design allows the third sealing plate 6 to have a small amount of floating space in the radial direction, avoiding jamming or wear, and also facilitates the installation and positioning of the first sealing plate 4 and the second sealing plate 5.

[0046] Example 7

[0047] In this embodiment, the lower part of the first sealing plate 4 and the second sealing plate 5 is configured as a curved surface that cooperates with the cooling roller 2; the lower part of the sealing plate being configured as a curved surface that cooperates with the cooling roller 2 can increase the fit between the sealing plate and the roller surface of the cooling roller 2, making it easier for the melt curtain to flow smoothly out of the box of the sealing assembly.

[0048] Example 8

[0049] In this embodiment, refer to the appendix. Figure 3 The lower part of the first sealing plate 4 and the second sealing plate 5 is provided with a contact part 8, which is made of high-performance engineering plastic. High-performance engineering plastic has a low coefficient of friction, high wear resistance and self-lubricating properties, which can minimize the wear and scratches on the surface of the high-gloss cooling roller 2, resist the chemical corrosion of plastic volatiles, and avoid sealing failure due to material deterioration.

[0050] Among them, high-performance engineering plastics use polytetrafluoroethylene.

[0051] The use of a vacuum structure in the production of cast film 3 involves the following steps:

[0052] Step 1: Check that the first sealing plate 4, the second sealing plate 5 and the third sealing plates 6 on both sides have been assembled into a complete box structure and are firmly fixed to the lower part of the extruder 1. Check that the T-shaped slider at the lower end of the third sealing plate 6 has been embedded in the T-shaped grooves on both sides of the cooling roller 2. Confirm that the vacuum pipe has been connected to the interface on the third sealing plate 6 and finally connected to the vacuum pump. Check the airtightness of the pipe connection.

[0053] Step 2: Adjust the lower end of the second sealing plate 5 to be in close contact with the surface of the cooling roller 2 to ensure the sealing of the melt curtain inlet side and prevent a large amount of air from entering from here. Adjust the first sealing plate 4 so that the gap between its lower end and the surface of the cooling roller 2 is precisely adjusted to be equal to the thickness of the target cast film 3.

[0054] Step 3: Start the extruder 1 and feeding system according to the standard operating procedures to begin plasticizing the material. Start the circulating cooling system of the cooling roller 2 and set the roller surface temperature to the low temperature required by the process. The cooling roller 2 starts to rotate. The melt curtain passes under the first sealing plate 4 and is finally introduced into the subsequent traction and winding device. When the melt curtain is stably attached to the cooling roller 2 and is running normally, start the vacuum pump and observe the vacuum gauge set on the vacuum pump. By adjusting the valves on the vacuum pipeline, gradually adjust the vacuum degree in the sealing assembly to the optimal value required by the process.

[0055] Step 4: The system enters a stable production state. After the melt curtain is extruded from the die, the air and volatiles between the melt curtain and the cooling roller 2 are quickly extracted. After being filtered through the interface and pipeline, it is discharged by the vacuum pump. The melt is rapidly cooled and shaped in an absolutely bonded state to form a high-quality film. It is then smoothly led out from the micro gap at the lower end of the first sealing plate 4. The machine is stopped regularly to check or replace the filter element in the filter to prevent the vacuum degree from being affected by the condensation and blockage of volatiles.

[0056] It should be noted that:

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vacuum structure for casting film production, comprising an extruder (1), wherein an extrusion lip (7) is provided at the lower end of the extruder (1), and a cooling roller (2) is provided below the extrusion lip (7), characterized in that, The lower part of the extruder (1) is also provided with a sealing component. The width of the sealing component matches the width of the cooling roller (2). The sealing component can cooperate with the cooling roller (2) and the melt curtain extruded by the extrusion lip (7) to form a sealed space. The internal pipe of the sealing component is connected to a vacuum pump.

2. The vacuum structure for casting film production according to claim 1, characterized in that, The sealing assembly includes a first sealing plate (4), a second sealing plate (5), and two third sealing plates (6). The upper ends of the first sealing plate (4) and the second sealing plate (5) are respectively connected to the lower part of the extruder (1). The two third sealing plates (6) are respectively disposed on both sides of the first sealing plate (4) and the second sealing plate (5) to form a box. One side of the third sealing plate (6) is provided with an interface, which is connected to the vacuum pump through a pipe.

3. A vacuum extraction structure for the production of a cast film according to claim 2, characterized in that The first sealing plate (4) is located in the outflow direction of the melt curtain. The distance between the lower end of the first sealing plate (4) and the cast film (3) formed on the cooling roller (2) by the melt curtain is between 0 and 50 μm. That is, the distance between the lower end of the first sealing plate (4) and the cooling roller (2) is equal to the thickness of the cast film (3).

4. A vacuum extraction structure for the production of a cast film according to claim 3, characterized in that The second sealing plate (5) is located on the side of the melt curtain away from the first sealing plate (4), and the lower end of the second sealing plate (5) is in close contact with the cooling roller (2).

5. A vacuum extraction structure for the production of a cast film according to claim 3, characterized in that The third sealing plates (6) on both sides are in sealing contact with the side edges of the cooling rollers (2) on the corresponding sides.

6. A vacuum extraction structure for the production of a cast film according to claim 5, characterized in that Each of the third sealing plates (6) has a T-shaped slider at the lower end near the cooling roller (2), and T-shaped grooves are provided at the two sides of the cooling roller (2). The T-shaped grooves are annular and are coaxial with the cooling roller (2).

7. A vacuum structure for casting film production according to any one of claims 2 to 6, characterized in that, The lower part of the first sealing plate (4) and the second sealing plate (5) is configured as a curved surface that cooperates with the cooling roller (2).

8. A vacuum structure for casting film production according to any one of claims 2 to 6, characterized in that, The lower part of the first sealing plate (4) and the second sealing plate (5) is provided with a contact part (8), and the contact part (8) is made of high-performance engineering plastic material.

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