Film production line for producing a film web, air extraction device for a film production line for producing a film web, and method for producing a film web

Abstract

The invention relates to a film production line for producing a film web, in particular a cast film line or calender line, comprising: an extruder for producing a continuous melt flow consisting of a thermoplastic material; an extrusion die having an outlet opening, in particular a flat die having an outlet opening in the form of a wide slot, which is designed to extrude the melt flow in the form of a flat molten web; and a film-producing roller (or cooling roller) having a lateral surface and a film-forming zone on the lateral surface, in which zone the molten web can be placed at a placement position, and can then be cooled form a film web; and comprising an air extraction device with an extraction opening, which is designed to extract air from the lateral surface of the film-producing roller by means of a negative pressure, wherein the extraction opening is located upstream of the placement position of the film-producing roller in the direction of rotation. It is proposed that the air extraction device has at least two lateral air chambers, preferably the air extraction device has at least one further central air chamber, wherein the respective air chambers are separated from one another, wherein the air chambers are arranged substantially along the longitudinal axis of the film-producing roller, wherein the lateral air chambers are each designed to extract air in an extraction portion of the lateral surface that corresponds to an edge portion of the film web.

Description

[0001] Film system for producing a film web, air extraction device for a film system for producing a film web and method for producing a film web

[0002] FIELD OF APPLICATION AND STATE OF THE ART

[0003] The present patent application relates to a film plant for producing a film web, in particular cast film or calender plants, an air extraction device and a method for operating a film plant with an air extraction device.

[0004] A film line is a specialized production system for the manufacture of thin film webs made of thermoplastic material. This article primarily describes so-called cast film lines. Such a line typically consists of an extruder, which melts thermoplastic material, normally in the form of granules or pellets, and converts it into a viscous melt. Once the material has melted, it is typically passed through an extrusion die with a wide outlet opening. This die is shaped to extrude the melt stream in the form of a flat melt web. This flat melt stream forms the basis for subsequent film production. One of the key components in such a film line is the film production roll. This roll, which is usually large, usually has a smooth, cylindrical surface onto which the flat melt web is applied.The film forming roller rotates at what is known as "film speed," meaning its rotation speed essentially corresponds to the desired speed of the film web to be produced. Immediately after the flat melt web has been applied to the film forming roller, it is cooled and converted into a relatively solid state. This is usually done by chill rollers in contact with cooling liquids, but the cooling process can also occur passively. Typically, a take-off unit then pulls the solidified film web from the roller, and the film web is transported further through the film line. Depending on requirements, slitters can be used to cut the film web to the desired width. The film web is then typically wound up on a rewind station to produce film rolls that can be reused or sold.The choice of film production roller is crucial as it significantly influences film production in terms of speed and quality.

[0005] The film speed, i.e. the rotation speed of the film forming roller, varies depending on the application requirements. Typically, film lines can achieve a wide range of speeds, from a few meters per minute to several hundred meters per minute. However, in such lines, the air rotating with the film forming roller, also known as drag air, is a significant limiting factor. Drag air is a general phenomenon in which an air stream forms around rotating rollers that rotates with the roller. This effect can limit the production speed of the film line, especially at high speeds. The drag air can lead to the melt web not being evenly applied to the outer surface of the film forming roller, which impairs product quality.Therefore, the uniform application of the melt path is a crucial aspect in order to achieve the maximum speed and efficiency of such a film line.

[0006] To ensure that the melt web or the resulting film web adheres firmly to the film production roller, air blowing devices are known in the art. These devices have blowing openings that serve to blow air onto the outer surface of the film production roller using positive pressure, thus pressing the film web against the roller. The blowing openings are positioned in the direction of rotation according to the contact position of the film production roller.

[0007] However, it has been shown that at increased line speeds, the phenomenon of drag air, which rotates synchronously with the roller, occurs. Especially at high line speeds, this drag air effect can lead to the melt web not being positioned flush with the outer surface of the film production roller. This proves to be particularly disadvantageous in the edge area of ​​the film web. The extruded film web is usually thicker in the edge area, so reduced heat transfer due to poor adhesion caused by the drag air can exacerbate the effect.

[0008] TASK AND SOLUTION

[0009] The main objective of the present invention is to minimize the effect of entraining air and thus enable improved adhesion of the melt web or film web to the film production roll.

[0010] The object is achieved by the subject matter of the independent claims. In particular, a film system for producing a film web, in particular a cast film or calender system, is proposed. This film system has an extruder that serves to generate a continuous melt stream from a thermoplastic material. The film system also has an extrusion nozzle with an outlet opening for extruding the melt stream in the form of a flat melt web. The extrusion nozzle can be designed as a flat die with a wide-slot outlet opening. This system also includes a film production roller that has a circumferential surface and a film formation zone on the circumferential surface. The melt web can be applied in this zone and subsequently cooled as a film web. An air extraction device is provided to ensure the adhesion of the melt web to the film production roller.This air extraction device has a suction opening that uses negative pressure to extract air from the outer surface of the film production roller. The suction opening is positioned in front of the film production roller's contact position in the direction of rotation.

[0011] In the present invention, the extracted air is at least partially the entrainment air described in the prior art, which forms when rollers rotate. This entrainment air can have a negative effect, especially in the edge areas of the film web.

[0012] When producing film webs, it is usually crucial that the edge regions of the film lie tightly and evenly on the film forming roller. This is critical for several reasons. A uniform fit of the edge regions can prevent unwanted pulling of the film towards the center of the film forming roller. If the edge regions do not fit tightly enough, the film can tend to pull towards the center of the film forming roller, which can lead to uneven thicknesses and possibly unwanted deformations. Furthermore, a uniform fit of the edge regions helps to minimize the occurrence of wrinkles or other irregularities. While the edge regions are often trimmed later to obtain a smooth edge, it is nevertheless preferable that the surface of the film web is as uniform as possible in this area too to ensure a high-quality end product.Proper adhesion of the edge areas of the film web to the film production roller is therefore crucial to producing a high-quality film web.

[0013] The outer surface of the film-forming roll is the outer surface of the cylindrical roll. This surface extends along the entire length of the roll and forms the outer shell, or in other words, the outer circumference of the cylinder. The outer surface of the film-forming roll can be smooth or have special features, such as grooves or groove patterns, depending on the intended properties of the film web to be produced.

[0014] The position of the film forming roller where the melt web first encounters the rotating film forming roller is also referred to as the contact position. This is where the still-liquid melt web makes contact with the film forming roller. The air extraction device is positioned to control the air extraction process precisely before this contact position, thus ensuring optimal adhesion of the melt web.

[0015] The film forming roll can be equipped with a cooling device to ensure that it is maintained at a defined temperature during the production process. This cooling can ensure that the melt web cools efficiently and transitions to a desired solid state. Cooling the film forming roll can be achieved in several ways. One common method is to circulate cooling fluids, such as water or special coolants, through the film forming roll. These fluids remove heat from the film forming roll and help to quickly cool the melt web. A cooled film forming roll can easily ensure that film production takes place within a controlled temperature range, which can ensure the quality and consistency of the produced film web.This is particularly advantageous when the film web is required to have specific desired mechanical and / or optical properties and to meet the requirements of a specific end application.

[0016] The invention is particularly characterized by the air extraction device, which has at least two separate, i.e., distinct, lateral air chambers. The air chambers are arranged along the longitudinal axis of the film-producing roller and are each designed to extract air in a extraction section of the circumferential surface, which corresponds to an edge section of the film web. In the film system according to the invention, lateral air chambers are therefore provided at least in the edge regions of the film-producing roller. One or more additional central air chambers can be provided between these lateral air chambers. This arrangement enables targeted control of the air extraction along the circumferential surface of the film-producing roller and is advantageous for minimizing entrainment air.

[0017] The air chambers are preferably separated from each other by partition walls. Through a targeted arrangement of air chambers and partition walls, the entrained air is preferably completely eliminated before it can impair the melt web. This contributes significantly to improving the quality and efficiency of the film production process, especially in the critical edge areas of the film web.

[0018] A typical film line, also known as a cast film line, is a machine for producing film webs from thermoplastic material. These lines can include several key components. Some of these components are described below:

[0019] Such a film line may have an extruder that melts the thermoplastic material, which is usually in the form of granules or pellets. The extruder includes a screw that mixes and heats the material, converting it into a liquid melt. Such a film line can also employ multiple extruders, each capable of melting different materials. This configuration enables, for example, the production of multilayer film webs in which different materials are applied in layers. This is particularly useful for producing films with special properties or functions that must be made from different materials, as is common for many packaging materials, for example.

[0020] The molten mass, the melt stream, is passed through an extrusion nozzle, usually with a thin and wide outlet opening. This nozzle is particularly suitable for extruding the melt stream in the form of a flat melt sheet. In many cases, this is a flat nozzle with a wide slot opening.

[0021] After the melt sheet passes through the extrusion die, it is directed onto the surface of a rotating film-forming roll. This film-forming roll typically has a cooled interior to cool the melt sheet and convert it into a solid state.

[0022] Other components of such a film line typically include a take-off unit, which pulls the solidified film web from the chill roll and transports it further through the line. The speed of the take-off can be used to control the desired thickness of the film web.

[0023] Film lines typically have a cross cutter that cuts the film web to the desired width. This allows, for example, the production of film rolls of different sizes. Such cross cutters are also used to remove edges of the film web, which are often discarded as waste during production.

[0024] After cutting, or as needed, the film web is typically wound onto a rewind station to create film rolls ready for shipping or further processing, for example. Such systems are typically monitored and controlled by a control system that can regulate process parameters such as temperature, speed, and / or pressure to ensure the quality of film production.

[0025] It's important to note that the actual configuration of a film line can vary depending on the specific requirements and desired end product variants. Some lines may feature additional features such as embossing or coating units to create special surface effects or functionalities. Overall, the film line enables the production of thin film webs that can be used in a wide variety of applications, from packaging materials to technical applications.

[0026] The air extraction device according to the present invention aims to specifically and effectively eliminate the described entrained air, at least in the edge regions of the film web, by extracting air from the area along the outer surface of the film production roller. This not only improves the adhesion of the melt web to the roller, but also minimizes the disruptive effect of the entrained air.

[0027] In the present invention, the entraining air is actively extracted from the outer surface of the film-forming roll before the melt web reaches this area and is applied to the roll surface of the film-forming roll. This process is crucial for optimizing the film production process and minimizing the adverse effects of entraining air.

[0028] This proactive extraction of the entraining air ensures that the melt web can be applied evenly and flush across the entire surface of the film production roller. This contributes significantly to improving product quality and increasing the efficiency of the manufacturing process. This design enables much higher line speeds, allowing the film web to be produced at up to 400 meters per minute.

[0029] Air extraction can be achieved in a variety of ways. The primary goal is to effectively remove, at least to a large extent, the entrained air from the surface of the film production roll in order to improve the quality of film production. Some of the common methods and means by which air extraction can be achieved in such a system are described below.

[0030] A vacuum device is a commonly used method for air extraction. It uses a pump to create a negative pressure that sucks air away from the surface of the film-forming roller. This method allows for precise control of the extraction process and is generally efficient. Methods and means for air extraction also include fans and / or blowers. Fans and / or blowers create an airflow that can be directed through exhaust ducts or channels. This method is widely used, and the respective air extraction is also suitable for extracting entrained air. An air extraction system can also be designed with a centrifugal separator, for example. These devices use centrifugal force to separate air from particles. Adsorbents such as activated carbon can also be used to remove gases or vapors from the air during extraction.

[0031] Throttle valves are an example of a means of controlling and regulating negative pressure. Throttle valves, which can be placed in the exhaust ducts of an air extraction device, enable the control of air flow and thus the prevailing negative pressure. They can be controlled manually or automatically. Pressure control valves or regulators can monitor and control the negative pressure. They ensure a constant suction power and can work in combination with sensors. Differential pressure sensors can be used to measure the pressure difference between the extracted area and, for example, the ambient air or another air chamber. They are particularly advantageous for maintaining the desired negative pressure or a predetermined pressure gradient. Frequency converters can be used in fans and blowers, which allow the negative pressure to be adjusted through variable speed controls.

[0032] The air extraction device implemented according to this invention has at least one suction opening positioned in the direction of rotation upstream of the application position of the film-forming roller. In other words, this is an opening in the air chambers. This means that the extraction begins actively even before the melt web reaches the relevant sections of the lateral surface. In this way, the entraining air is preferably completely eliminated before it can impair the adhesion of the melt web.

[0033] The lateral air chambers are designed such that they each cover an area along the longitudinal axis of the film-producing roller, which extends to the suction section of the lateral surface corresponding to an edge section of the film web. This area preferably extends by plus / minus 25 centimeters along the longitudinal axis of the film-producing roller; more preferably, the area extends by plus / minus 15 centimeters along the longitudinal axis of the film-producing roller. This means that the suction opening extends in an area to the right and left of the film area along the longitudinal axis of the film-producing roller.

[0034] With respect to the outer surface of the film-producing roller, the suction opening preferably extends over a range of 2 to 100 degrees of the roller surface; more preferably, the suction opening extends over a range of 15 to 90 degrees of the roller surface. This allows the entraining air to be effectively suctioned off, and it can be ensured in a particularly simple manner that the melt web lies evenly and flush against the roller surface, particularly in the edge regions of the produced film web. The distance of the suction opening is preferably positioned less than 10 degrees in the direction of rotation in front of the application position of the film-producing roller; more preferably, the distance of the suction opening is positioned less than 2 degrees in the direction of rotation in front of the application position of the film-producing roller.

[0035] In one embodiment, the film system has a controller for controlling the negative pressure in the various air chambers. The controller is preferably designed to generate and / or manage differences in the negative pressure between the air chambers. The task of the controller is to precisely and specifically control the negative pressure in the air chambers in order to optimize the removal of entraining air and the adhesion of the melt web to the film production roller. By being able to generate and manage differences in the negative pressure between the air chambers, the controller can adapt the extraction process to different requirements and conditions. This enables flexible and customized control of the air extraction along the film production roller to ensure optimal film production.

[0036] The specific design of the air extraction device aims to effectively remove the entraining air from at least the critical edge areas of the film web once the melt web has been placed on the film production roller. By creating an increased negative pressure in these lateral air chambers, it is ensured that the melt web is pressed tightly against the roller surface, thus ensuring optimal adhesion.

[0037] In one embodiment, the air extraction device has two lateral air chambers, each corresponding to the area of ​​the lateral surface of the film production roller against which the edge region of the film web rests after the melt web has been applied. In addition, a further central air chamber is arranged precisely between these two edge air chambers on the longitudinal axis of the film production roller. This arrangement of the air chambers enables targeted control and optimization of the extraction process. The two lateral air chambers are designed to effectively remove the entraining air from the edge regions of the film web in order to ensure uniform adhesion and cooling of the melt web. The additional central air chamber in between serves to uniformly regulate the negative pressure in the central region of the film web and to control the removal of the entraining air in this region.

[0038] In one embodiment, the air extraction device is designed such that it generates an increased negative pressure in the lateral air chambers compared to possible additional central air chambers within the air extraction device.

[0039] In one embodiment, the air extraction device for controlling the negative pressure is designed such that it regulates the negative pressure depending on at least one parameter of the film line. These parameters include, for example, the speed of the film production roller and / or the type of thermoplastic material being processed. This means that the control system is preferably able to dynamically adjust the negative pressure in order to meet specific requirements of the current production process. If, for example, the speed of the film production roller needs to be increased, the air extraction device can adjust the negative pressure accordingly to ensure that the entraining air removal and the adhesion of the melt web remain optimal. Likewise, the control system can adjust the negative pressure when processing different thermoplastic materials in order to ensure the best conditions for each material type.

[0040] In one embodiment, the air extraction device is equipped with sealing elements designed to seal the area between the film-forming roller and the surrounding environment of the respective air chambers. This preferably serves to specifically control and / or minimize air flow in the area between a respective air chamber and the surrounding environment of the respective air chamber. These sealing elements can, for example, be flexible sealing elements that are in close or quasi-contact with the surface of the film-forming roller. They can be designed as a modular construction, meaning they can be adapted to different roller diameters or configurations. These sealing elements preferably fulfill several important functions:

[0041] 1. Air flow contra Ile: The sealing elements can be designed so that the air flow in the area between the film production roller and the environment can be precisely controlled.

[0042] 2. Prevention of ingress: The sealing elements can be used to reduce or prevent the ingress of unwanted air or contaminants into the film web manufacturing process.

[0043] 3. Adaptability: Thanks to a modular design, the sealing elements can be adapted to different roll diameters or configurations. This enables flexible use of the air extraction device in various production environments.

[0044] In one embodiment, the width and / or position of the air chambers is adjustable along the longitudinal axis of the roller. Preferably, the width and / or position of the lateral air chambers is adjustable along the longitudinal axis of the roller. Depending on the configuration, the width and / or position of the central air chamber(s) correlates with the adjustment of the lateral air chambers. This allows adaptation to different production conditions, especially when the width of the film produced can be varied.

[0045] In one embodiment, the air extraction device is equipped with a displacement device that allows the width and / or position of the air chambers to be adjusted along the longitudinal axis of the roller. This displacement device preferably offers various adjustment options. This embodiment offers flexibility to adapt the air chambers depending on the specific requirements of the manufacturing process, be it due to changes in product width or other operating conditions. The adjustable width and positioning of the air chambers allows the air extraction device to be tailored to the respective production process. On the one hand, the adjustment can be manual. In this case, the width of the air chambers can be adjusted manually by an operator. This is usually done by moving or adjusting the corresponding components of the air extraction device.Alternatively, it can also be mechanical. The width of the air chambers can be adjusted using mechanisms such as threaded or lever mechanisms, which allow for precise adjustment of the air chambers. Preferably, it is automatic. The width of the air chambers can be adjusted automatically. This can be achieved by integrating a motorized or electronic control system that adjusts the position of the air chambers based on current production requirements.

[0046] In one embodiment, in addition to or alternatively to moving the partition walls of the air chambers, the outer walls of the lateral air chambers can also be moved using the displacement device. This allows for adjustment of the width and / or position of the lateral air chambers along the longitudinal axis of the film-forming roller in the outer region. The versatility of these adjustment options allows the air extraction device to be efficiently adapted to different production conditions and the desired configuration of the air chambers to be selected depending on the requirements of the manufacturing process.

[0047] In one embodiment, the air extraction device is designed to operate the lateral air chambers at a negative pressure typically in the range of -0.5 bar to -5 bar. Preferably, the air extraction device is operable in the range of -1 bar to -4 bar, with a particularly preferred operating range being between -2 bar and -3 bar. The ability to precisely adjust the negative pressure within this range allows the air extraction device to be adapted to the specific requirements of the manufacturing process and to ensure the desired conditions for producing high-quality film webs.

[0048] In one embodiment, the air extraction device is designed to operate the central air chambers at a negative pressure typically in the range of -0.01 bar to -2 bar. Preferably, the air extraction device is operable in the range of -0.8 bar to -1 bar, with a particularly preferred operating range being between -0.3 bar and -0.5 bar.

[0049] It has been found that a specific operation of the air extraction device is particularly advantageous in order to achieve a uniform surface of the film web produced, in which a lower negative pressure is applied in the central regions of any air chambers present and a higher negative pressure is applied in the lateral air chambers in the edge regions.

[0050] Through this targeted adjustment of the vacuum, it was determined that the film web exhibits a particularly uniform surface. This effect results from the targeted control of the airflow along the film production roller. The lower suction in the central areas enables a smoother and more uniform surface, while the increased suction in the edge areas helps press the melt web tightly against the roller surface and minimize entrainment air.

[0051] In one embodiment, the film system has an air blowing device with a blowing opening. This blowing opening is designed to blow air onto the outer surface of the film production roller using positive pressure in order to press the film web against the film production roller.

[0052] It is preferred that the blow opening be positioned downstream of the film forming roller's application position in the rotational direction. This means that the blow opening is oriented to direct the air flow toward the moving film forming roller. This arrangement can help ensure that the melt web is properly and evenly applied to the roller surface, ensuring optimal adhesion.

[0053] In a second aspect, the invention relates to an air extraction device for a film system, in particular for a cast film or calender system, for producing a film web. This air extraction device is designed such that air can be extracted from the outer surface of a film production roller of the film system by means of a negative pressure. The film production roller serves in a corresponding film system for applying a continuous melt stream of a thermoplastic material, which can be applied by an extruder via an extrusion nozzle with an outlet opening in the form of a flat melt web. The suction opening is designed such that it can be positioned in front of the application position of the melt web on the film production roller in the direction of rotation. The air extraction device has at least two lateral air chambers; preferably, the air extraction device has at least three separate air chambers.These air chambers are designed such that they can be arranged along a longitudinal axis of the film-producing roller. The two lateral air chambers are each designed to extract air from a suction section of the outer surface corresponding to an edge section of the film web. The film system is preferably a film system of the type described.

[0054] In one embodiment, the air extraction device is characterized in that it is assigned a controller for controlling the negative pressure in the various air chambers. This controller is designed to specifically generate and / or manage differences in the negative pressure between the air chambers. The controller is designed to enable differentiated adjustment of the negative pressure in the individual air chambers. This means that the negative pressure strength in the air chambers can be individually adjusted and controlled. This ability to fine-tune the negative pressure in the various areas of the air extraction device preferably contributes to optimizing the removal of entraining air and ensuring the production of high-quality film webs in the film line.

[0055] The air extraction device preferably has the features already described above, as shown in relation to the air extraction device of the film system.

[0056] In a third aspect, the invention relates to a method for producing a film web.

[0057] In the process, a thermoplastic material is first processed into a continuous melt stream using an extruder. This melt stream is then extruded from an extrusion die, in particular a flat die, through an outlet opening in the form of a flat melt web. The melt web is applied to a circumferential surface at a contact position of a cooled film-forming roller rotating in a direction of rotation about an axis. During operation, the film-forming roller rotates in a direction of rotation about an axis. Preferably, the film-forming axis is cooled. The melt web is cooled as a film web, i.e., the melt web solidifies, whereby it is referred to as a film web. An air extraction device with a suction opening extracts air from the circumferential surface of the film-forming roller using negative pressure, wherein the suction opening is positioned in front of the contact position of the film-forming roller in the direction of rotation.The air extraction device has at least two lateral air chambers; preferably, the air extraction device has at least one additional central air chamber, wherein the air chambers are arranged substantially along the longitudinal axis of the film-forming roller. Preferably, the air extraction device has a system for controlling the negative pressure in the various air chambers. This method enables the efficient production of high-quality film webs in cast film or polishing systems, with the removal of entraining air being precisely controlled to ensure consistent film quality.

[0058] In this process, a film line of the type described above is preferably used. This film line is designed to produce film webs by extruding the melt stream of a thermoplastic material, applying it to a cooled film-forming roll, and removing entraining air using an efficient air extraction system. Precise control of the negative pressure in the various air chambers of the air extraction system contributes to ensuring a uniform surface and high quality of the produced film web. This system design enables effective and reliable production of film webs, especially in cast film or calender systems.

[0059] Further advantages and aspects of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the schematic figures.

[0060] Fig. 1 shows an embodiment of a film system according to the invention

[0061] Fig. 2 shows the embodiment of Fig. 1 in a side view

[0062] Fig. 3 shows the embodiment of Figs. 1 and 2 in a further side view.

[0063] Fig. 4 shows an embodiment of an inventive

[0064] Air extraction device in a view from below

[0065] Fig. 5 shows an embodiment of an inventive

[0066] Air extraction device with air chambers adjustable in width.

[0067] Fig. 6 shows the embodiment of Fig. 5 in another possible configuration. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] Figure 1 shows a side view of the film-producing roller 40 in cross-section. An extrusion nozzle 30 is arranged above the film-producing roller 40. The extrusion nozzle is designed as a flat nozzle with an outlet opening 32 in the form of a slot die and extends along the longitudinal axis 4 above the film-producing roller 40. A thermoplastic material 20 is conveyed in the nozzle 30 and is guided by an extruder (not shown) as a continuous melt stream 22 to the outlet opening 32. From the outlet opening 32, the thermoplastic material 20 is extruded in the form of a flat melt web 24 onto the outer surface 42 of the film-producing roller 40. The melt web 24 is placed at a contact position 44 on the outer surface of the roller 40. The film production roller 40 rotates about its longitudinal axis 4 in the direction of rotation 2 and cools the melt web 24, whereby it solidifies as a film web 26.In front of the application position 44 is an air extraction device 50 with a suction opening 52, which serves to extract air from the outer surface 42 of the film-producing roller 40 using a negative pressure. The suction opening 52 is positioned in front of the application position 44 of the film-producing roller 40 in the direction of rotation 2. According to the invention, the air extraction device 50 in this exemplary embodiment has three mutually separated air chambers 54, 56, 58, which are arranged along the longitudinal axis 4 of the film-producing roller 40. Two of these air chambers, the lateral air chambers 54, 58, are each designed to extract air in a suction section 46 of the outer surface 42 corresponding to an edge section 28 of the film web 24.

[0069] Figure 2 shows the embodiment from Figure 1 in a side view, in which the film production roller 40 is shown from the front in the direction of rotation 2. Here, it is clearly visible where the suction section 46 of the outer surface 42, corresponding to an edge section 28 of the film web 24, is located. From this view, the extrusion nozzle 30 almost completely conceals the air suction device 50. To the side of the air suction device 50 is the displacement device 70 present in this embodiment, which makes it possible to adjust the width and / or position of the air chambers along the longitudinal axis of the roller. Also indicated are the three air chambers 54, 56, 58, which in this example are separated from one another by partition walls. Figure 3 provides a rear view of the embodiment shown in Figure 2. In this view, the vacuum connections 60, 62 and 64 of the side and middle air chambers 54, 56 and 58 can be seen.These connections are positioned above the respective air chambers 54, 56, and 58 and serve to direct the required negative pressure into the respective air chambers 54, 56, and 58. The side air chambers 54, 58 and the central air chamber 56 are separated from each other by partition walls to enable precise control of the negative pressure in these areas. The negative pressure control system, identified by the reference numeral 66, is also indicated and plays a central role in setting and managing the negative pressure in the various air chambers 54, 56, and 58. This negative pressure control system 66 enables flexible adaptation to the specific requirements of the film production process and contributes to improving the quality and uniformity of the produced film web.

[0070] Figure 4 shows an air extraction device 50 for a film system 10 for producing a film web 26, in particular a film system for cast film or calender systems. In this illustrated embodiment, the air extraction device 50 is designed according to the air extraction device 50 of the film system 10 from Figs. 1 to 3. Fig. 4 shows a view from below, i.e., seen from the film production roller 40. The air extraction device 50 has a suction opening 52, which serves to extract air from the outer surface 42 of the film production roller 40 by means of a negative pressure. On this roller 42, a continuous melt stream 22 of a thermoplastic material 20 is extruded from an extrusion nozzle 30 with an outlet opening 32 in the form of a flat melt web 24. The suction opening 52 is designed such that it can be positioned in the direction of rotation in front of the application position 44 of the melt web 24 on the film production roller 40.This enables efficient removal of air along the application position 44, thereby improving film production. The air extraction device 50 is characterized by its three separate air chambers, shown in this exemplary embodiment as lateral air chambers 54, 58 and central air chamber 56. These air chambers 54, 56, and 58 are arranged along the longitudinal axis 4 of the film production roller 40 to ensure uniform extraction of air along the entire circumferential surface 42. In particular, the two lateral air chambers 54, 58 are designed such that they each extract air from a suction section 46 of the circumferential surface 42 corresponding to an edge section 28 of the film web 24.In this view, sealing elements 68 are shown which are designed to seal the area between the film-forming roller 40 and the surrounding environment of the respective air chambers 54, 56 and 58 in order to control and / or minimize air flow in the area between the film-forming roller 40 and the environment.

[0071] Figure 5 shows the same air extraction device 50 as in Figure 4, but in this illustration, the width and / or position of the air chambers 54, 56, and 58 along the longitudinal axis 4 of the film-producing roller 40 has been adjusted. This was achieved using the displacement device 70 present in this exemplary embodiment. The displacement device 70 displaced the partition walls 55, 59 between the air chambers 54, 56, and 58 such that the lateral air chambers 54, 58 cover a larger area of ​​the lateral surface 42. This increased the extraction area of ​​the lateral air chambers 54, 58. The air chamber width and position can be adjusted depending on the conditions of the manufacturing process to ensure optimal performance of the air extraction device.

[0072] In Fig. 6, in addition to the displacement of the partition walls 55, 59, as shown in Fig. 5, the outer walls 53, 57 of the lateral air chambers 54, 58 have also been displaced by means of the displacement device 70. This means an adjustment of the width and / or position of the air chambers 54, 56 along the longitudinal axis 4 of the film-forming roller 40 in the outer region.

[0073] List of reference symbols

[0074] 2 Rotation direction

[0075] 4 Longitudinal axis

[0076] 10 film system 20 thermoplastic material

[0077] 22 Melt stream

[0078] 24 melt track

[0079] 26 film strips

[0080] 28 Film edge 30 Extrusion nozzle

[0081] 32 Exit opening

[0082] 40 film production roller

[0083] 42 lateral surface

[0084] 44 Position 46 Suction section

[0085] 50 Air extraction device

[0086] 52 Suction opening

[0087] 54 side air chamber 56 middle air chamber

[0088] 58 side air chamber

[0089] 60 Vacuum connection of the side air chamber

[0090] 62 Vacuum connection of the middle air chamber 64 Vacuum connection of the side air chamber

[0091] 66 Negative pressure control system

[0092] 68 sealing elements

[0093] 70 Shifting device

Claims

Claims 1. A film system for producing a film web, in particular a cast film or calender system, comprising: a. an extruder for producing a continuous melt stream from a thermoplastic material; b. an extrusion nozzle having an outlet opening, in particular a flat nozzle, designed to extrude the melt stream in the form of a flat melt web; c. a film production roller having a peripheral surface and a film formation zone on the peripheral surface, in which the melt web can be applied and subsequently cooled as a film web; and d. an air extraction device having a suction opening designed to extract air from the peripheral surface of the film production roller by means of a vacuum; e. the suction opening is positioned in the direction of rotation upstream of the application position of the film production roller;the air extraction device has at least two lateral air chambers, preferably the air extraction device has at least one further central air chamber, wherein the respective air chambers are separated from one another, wherein the air chambers are arranged substantially along the longitudinal axis of the film production roller, wherein the lateral air chambers are each designed to extract air in a suction section of the lateral surface corresponding to an edge section of the film web.

2. Film system according to claim 1, characterized in that a. the film system has a control system for controlling the negative pressure in the various air chambers, and that b. the control system is designed to generate and / or manage differences in the negative pressure between the air chambers.

3. Film system according to one of claims 1 and 2, characterized in that the air extraction device is designed in such a way as to build up a higher negative pressure in the lateral air chambers in comparison to other air chambers of the air extraction device.

4. Film system according to one of claims 1 to 3, characterized in that a. the lateral air chambers each correspond to the area of the outer surface of the film production roller against which the edge area of the film web rests after the application of the melt web, and that b. a further central air chamber is arranged between the lateral air chambers in the edge area on the longitudinal axis of the film production roller.

5. Film system according to one of claims 1 to 4, characterized in that the air extraction device for controlling the negative pressure is designed to regulate the negative pressure depending on at least one parameter of the film system, such as the speed of the film production roller and / or the type of thermoplastic material being processed.

6. Film system according to one of claims 1 to 5, characterized in that the air extraction device has sealing elements which are designed to seal the area between the film production roller and the surrounding environment of the respective air chambers in order to control and / or minimize an air flow in the area between a respective air chamber and an environment of the respective air chamber.

7. Film system according to one of claims 1 to 6, characterized in that the width and / or position of the air chambers along the longitudinal axis of the roller is adjustable.

8. Film system according to claim 7, characterized in that the air extraction device for adjusting the width and / or position of the air chambers has a displacement device which makes it possible to adjust the width and / or position of the air chambers along the longitudinal axis of the roller.

9. Film system according to one of claims 1 to 8, characterized in that the air extraction device is designed to operate the lateral air chambers with a negative pressure in the range of -0.5 bar to -5 bar, preferably in the range of -1 bar to -4 bar, particularly preferably between -2 bar to -3 bar.

10. Film system according to one of claims 1 to 9, characterized in that the air extraction device is designed to operate the at least one central air chamber with a negative pressure in the range of -0.01 bar to -2 bar, preferably in the range of -0.8 bar to -1 bar, particularly preferably between -0.3 bar to -0.5 bar.

11. Film system according to one of claims 1 to 10, characterized in that a. the film system has an air blowing device with a blowing opening which is designed to blow air by means of an overpressure onto the outer surface of the film production roller in order to press the film web against the film production roller, wherein b. the blowing opening is positioned in the direction of rotation after the application position of the film production roller.

12. Air extraction device for a film system for producing a film web, in particular a film system for cast film or calender systems, wherein a. the air extraction device has a suction opening which is designed to extract air by means of a negative pressure from a jacket surface of a film production roller of the film system, onto which a continuous melt stream made of a thermoplastic material, produced by an extruder, can be applied from an extrusion nozzle with an outlet opening in the form of a flat melt web, and wherein b. the suction opening is designed to be positioned in the direction of rotation in front of a contact position of the melt web on the film production roller, characterized in that c.the air extraction device has two lateral air chambers, preferably the air extraction device has at least one further central air chamber, wherein the air chambers are separated from one another, wherein the air chambers are designed to be arranged substantially along a longitudinal axis of the film production roller, and d. that the lateral air chambers are designed to each extract air in a suction section of the lateral surface corresponding to an edge section of the film web.

13. Air extraction device according to claim 12, characterized in that a. the air extraction device is assigned a controller for controlling the negative pressure in the various air chambers, and that b. the controller is designed to generate and / or manage differences in the negative pressure between the air chambers.

14. A process for producing a film web comprising the following steps: a. a thermoplastic material is processed into a continuous melt stream by means of an extruder, and b. the melt stream is extruded from an extrusion nozzle, in particular a flat nozzle, through an outlet opening in the form of a flat melt web, and c. the melt web is applied to a jacket surface at a contact position of a film production roller, and d. the melt web is cooled as a film web, and e. an air extraction device with a suction opening extracts air from the jacket surface of the film production roller by means of a negative pressure, wherein i. the suction opening is positioned in front of the contact position of the film production roller in the direction of rotation, and ii. the air extraction device has at least two lateral air chambers, preferably the air extraction device has at least one further central air chamber, wherein the air chambers are arranged substantially along the longitudinal axis of the film production roller, and that iii.the lateral air chambers are each designed to suck air into a suction section of the lateral surface corresponding to an edge section of the film web.

15. Method according to claim 14, characterized in that the film web is produced by means of a film system according to one of claims 1 to 11.

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