Casting unit, apparatus for manufacturing film, and method for manufacturing film

Abstract

To provide a casting unit, apparatus, and method for manufacturing a film that reduces air trapping between the plastic molten material and the chill roll in a simple manner. [Solution] A casting unit (14) for a device for manufacturing a film comprises a slot die (26), a chill roll (28), and an air nozzle device (32). The chill roll (28) has at least a circumferential surface (36), the slot die (26) is configured to produce a molten material (38), and the air nozzle device (32) is connected to the slot die (26) such that the circumferential surface (36) of the chill roll (28), the molten material (38), the slot die (26), and the air nozzle device (32) are defined by an intermediate space, and is designed to generate an airflow (46) that generates negative pressure in the intermediate space.

Description

Technical Field

[0001] The present invention relates to a casting unit, an apparatus for producing a film, and a method for producing a film.

[0002] In the production of thin plastic films, a film of plastic melt is first applied onto a chill roll, where it is cooled and solidified. In this case, air bubbles may be trapped between the plastic melt and the chill roll, and the air bubbles become part of the film, thereby impairing the quality of the film.

[0003] To avoid such air entrapment between the plastic melt and the chill roll, it is known to arrange a hood extending below the slot die in a direction opposite to the rotation direction before the melt is applied. Thereafter, air is evacuated from this hood to generate a negative pressure, which as a result reduces air entrapment. For example, U.S. Pat. No. 5,618,568 describes such a solution.

[0004] The problem with this solution is that the hood needs to be placed in very close proximity to the chill roll so that a sufficiently large vacuum can be generated to achieve a noticeable effect. This makes the setup of the apparatus difficult and time-consuming, which in turn reduces economic benefits.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the object of the present invention is to provide a casting unit, apparatus, and method for manufacturing a film that reduces air trapping between the plastic molten material and the chill roll in a simple manner. [Means for solving the problem]

[0007] This problem is solved by a casting unit for a film manufacturing apparatus, comprising a slot die, a chill roll, and an air nozzle device. The chill roll has a circumferential surface and is designed to rotate around an axis so that the circumferential surface moves in the rotational direction. The slot die is designed to produce a molten material that contacts the circumferential surface in the coating line. The air nozzle device is connected to the slot die such that an intermediate space is defined by the circumferential surface of the chill roll, the molten material, the slot die, and the air nozzle device, and the air nozzle device is designed to produce an airflow that strikes the circumferential surface along the line of action in the opposite direction to the rotation, generating negative pressure in the intermediate space.

[0008] The negative pressure generated by the airflow contacting the circumferential surface of the chill roll is created by the airflow itself, so the intermediate space is sealed along its width, thereby easily generating negative pressure. In addition, precise positioning of larger components such as hoods is not required.

[0009] In particular, negative pressure exists in the region below the molten material and / or in the intermediate space section in the direction of rotation from the zero line.

[0010] Furthermore, the airflow in contact with the circumferential surface separates the boundary layer of air moving with the circumferential surface from the surface. In this way, air trapping in the molten material can be further reduced.

[0011] Within the scope of this disclosure, the rotational direction corresponds to the direction in the circumferential direction defined by the circumferential direction of the chill roll. Similarly, the axial direction may be defined by the axial direction of the chill roll.

[0012] In particular, the coating lines and action lines extend in the axial direction.

[0013] Airflow can also constitute the boundary of an intermediate space. In particular, airflow can expel air from an intermediate space.

[0014] The casting unit may include a coating device designed to apply the molten material onto the chill roll particularly uniformly and reliably. The coating device may be a so-called “pinning device,” such as an electrostatic coating device (“e-pinning device”). Such coating devices are known, for example, from German Patent Application Publication No. 102022118971. Other pinning devices may also be used.

[0015] In one embodiment, the slot die includes an outlet opening that opens circumferentially in the rotational and / or radial directions, thereby enabling the molten material to be applied to the chill roll in a particularly controlled manner.

[0016] The direction of the opening, i.e., the normal direction of the opening, has, for example, a component in the rotational direction and a component in the radial direction toward the circumferential surface.

[0017] The exit opening can be offset in the rotational direction relative to the zero line.

[0018] In one embodiment, the outlet opening and / or molten material has width in the axial direction, and the axial width of the intermediate space, airflow and / or air nozzle device is smaller than the width of the outlet opening and / or molten material, equal to the width of the outlet opening and / or molten material, and larger than the width of the outlet opening and / or molten material. In this way, it is ensured that air is not trapped across the entire width of the molten material.

[0019] The width of the chill roll is equal to or greater than the width of the air nozzle device, airflow, and / or molten material.

[0020] To avoid film irregularities, the exit opening, melt, intermediate space and / or airflow are continuous in the axial direction.

[0021] In one embodiment, the air nozzle device comprises a flow guide section that defines a gap between the chill roll and the air nozzle device, the airflow flows through the gap, in particular, the gap is 0 mm to 6 mm, particularly 1.5 mm to 3.5 mm. The negative pressure in the intermediate space can be adjusted by the size of the gap.

[0022] The negative pressure in the intermediate space can be adjusted by the level of the positive pressure provided by the compressed air source.

[0023] For example, the flow guide section is wedge-shaped, rounded and / or convex with a tip directed towards the chill roll. The flow guide section may be made of polyether ether ketone (PEEK).

[0024] The action line is, in particular, located within the gap, ahead of the gap with respect to the rotation direction, or behind the gap with respect to the rotation direction.

[0025] In one embodiment, the airflow at the action line and / or in the gap has a velocity of 50 m / s to 250 m / s, particularly 50 m / s to 200 m / s, and / or the negative pressure in the intermediate space is 500 Pa to 25,000 Pa, particularly 5 Pa to 25,000 Pa, for example 5 Pa to 600 Pa, particularly 30 Pa to 150 Pa, or 500 Pa to 20,000 Pa, which makes it possible to further reduce air entrapment.

[0026] The pressure data of the negative pressure should be understood as a pressure difference relative to the ambient pressure.

[0027] In order to produce films of particularly high quality, the application line can be offset in the rotational direction, and / or the working line can be offset relative to the zero line in the direction opposite to the rotational direction, in particular the zero line corresponds to a radially extending straight line passing through the apex of the chill roll in a properly assembled position.

[0028] The apex is also referred to as the 12 o'clock position.

[0029] The distance from the zero line to the melt and / or application line may be 30 mm to 100 mm, and the distance between the zero line and the airflow and / or working line may be 30 mm to 145 mm, each measured along the tangent at the zero line.

[0030] In order to effectively remove the boundary layer, in particular from the chill roll, the airflow can contact the peripheral surface at an incident angle of 0° to 80°, in particular 5° to 40°.

[0031] Within the scope of the present disclosure, the incident angle is understood to mean the angle between the airflow and the tangent at the working line.

[0032] The incident angle is, in particular, constant along the width of the airflow.

[0033] For space-saving integration, the air nozzle device can be mounted on the slot die, in particular on the side of the slot die facing the chill roll.

[0034] The air nozzle device can be designed to be movable relative to the slot die, so that the position of the airflow and / or the gap can be adjusted to suit circumstances such as the material of the film to be produced.

[0035] In one embodiment, the air nozzle device has a nozzle section including a nozzle opening that opens toward a line of action, a gap, and / or a flow guide section, and in particular, the air nozzle device includes at least one compressed air source designed to deliver air to the nozzle opening to generate airflow. Thus, the airflow exiting the nozzle opening can be generated in a controlled manner.

[0036] The compressed air source can be positioned on the end face of the air nozzle device. For example, it is conceivable to have two compressed air sources positioned on two opposite end faces of the air nozzle device.

[0037] The compressed air source is, for example, at least a pipe and / or hose, such as a pipe and / or hose system. For example, the compressed air source may be supplied with compressed air by a compressor, which is part of the compressed air source. The compressor may be located in a space away from the apparatus.

[0038] In one embodiment, the air nozzle device includes a reservoir from which the nozzle opening extends. Uniform axial pressure, and therefore homogeneous airflow, is generated by the reservoir.

[0039] In particular, the nozzle opening and / or reservoir is the same width as the molten material, or wider than the molten material. The nozzle opening and / or reservoir is, for example, continuous along its entire length.

[0040] An air nozzle device, particularly a nozzle section, may comprise an inlet chamber and several ducts to maintain a constant axial pressure within a reservoir, the ducts fluidly connecting the inlet chamber to the reservoir, and in particular, at least one compressed air source is located at the end face of the inlet chamber.

[0041] In particular, the inlet chamber is continuous along its width. The width of the inlet chamber can correspond to the width of the reservoir.

[0042] In one embodiment, the casting unit has a control device, and the air nozzle device has at least one compressed air source equipped with a pressure regulating valve. The control device is connected to the pressure regulating valve and configured to control the pressure regulating valve. In this way, a negative pressure in the intermediate space can be automatically and precisely set, in particular to prevent the molten material from fluttering before contacting the chill roll.

[0043] For example, the control device is configured to receive the chill roll speed as an input and output a control signal to the pressure regulating valve based at least on the chill roll speed.

[0044] In particular, the pressure regulating valve affects the level of negative pressure in the inlet chamber, and therefore the airflow pressure and the negative pressure in the intermediate space.

[0045] The levels of negative pressure and / or input pressure within the inlet chamber may also be set manually. For example, a pressure regulating valve is a manually operated valve.

[0046] To increase the negative pressure in the intermediate space, the air nozzle device may include two end face covers, each positioned on one of the end faces of the intermediate space to axially close the intermediate space, in particular, at least one of the covers having a pressure sensor and / or a measuring opening fluidly connected to the pressure sensor.

[0047] The cover is movable in the circumferential and radial directions, independently of, for example, the nozzle section of an air nozzle device.

[0048] Furthermore, the problem is solved by a unit for manufacturing film that includes the aforementioned casting unit and stretching units, particularly a transverse direction orienter, a machine direction orienter, and / or a simultaneous stretching device.

[0049] The features and advantages described for the casting unit also apply to the apparatus, and vice versa.

[0050] This problem is also solved by a method for manufacturing a film using the aforementioned unit, wherein the molten material is generated by a slot die, applied to a chill roll, and simultaneously a negative pressure is generated in the intermediate space.

[0051] The features and advantages described for the casting unit and / or apparatus also apply to the method, and vice versa.

[0052] For example, the level of negative pressure in the intermediate space is controlled by the casting unit's control device, particularly based on the speed of the chill roll.

[0053] Further features and advantages of the present invention are described below and referenced in the accompanying drawings. The drawings are as follows: [Brief explanation of the drawing]

[0054] [Figure 1] A schematic diagram of an apparatus according to one embodiment of the present invention, which includes a casting unit according to one embodiment of the present invention, is shown. [Figure 2] A schematic perspective view of the casting unit shown in Figure 1 is provided. [Figure 3] Figure 2 shows a cross-sectional schematic diagram illustrating the principle of the casting unit. [Figure 4] A flowchart of one embodiment of the method according to the present invention is shown. [Figure 5] A detailed side view of the casting unit of one embodiment of the present invention is shown. [Figure 6] Figure 5 shows a cross-sectional view of the air nozzle device of the coating device. [Figure 7] Figure 5 shows a bottom view of a portion of the coating device. [Figure 8] Figure 5 shows an enlarged cross-sectional view of the air nozzle device of the coating device in the airflow region. [Figure 9] This shows how to represent air pressure in an intermediate space. [Figure 10] The graph shows two exemplary curves illustrating the dependency of the input pressure on the chill roll velocity. [Modes for carrying out the invention]

[0055] Figure 1 shows a very schematic representation of the apparatus 10 for manufacturing film F, which comprises several different units and devices.

[0056] For example, apparatus 10 is a sequential film manufacturing unit, which exemplifies the present invention without limiting the scope of protection.

[0057] In the illustrated example, the apparatus 10 comprises an extrusion device 12, a casting unit 14, at least a machine direction orienter 16 (MDO), a transverse direction orienter 18 (TDO), a processing device 20, and a winding device 24.

[0058] The extruder 12 includes an extruder and is configured to produce a molten material from at least one starting product. The molten material is a plastic molten material.

[0059] For example, extruders include single-screw extruders, cascade extruders, and / or twin-screw extruders.

[0060] Other mixing and processing equipment, such as a buskneter or planetary roller extruder, may also be used.

[0061] Similarly, it is also possible to produce a molten material by polymerization. For this purpose, monomers (and optionally additives such as catalysts) are mixed and polymerized in the reactor and / or extruder of the extruder 12.

[0062] The molten material can be directly applied onto the chill roll 28 of the casting unit 14 via the slot die 26 of the casting unit 14, thereby generating a film F.

[0063] Chill Roll 28 has a diameter of, for example, 50 cm to 4 m.

[0064] The resulting film F may have one or more layers. In the case of a multilayer film, the extruder may produce some or all of the layers, or an extruder may be provided for each layer.

[0065] The film F is then sent to the longitudinal stretcher 16, where it is stretched in the longitudinal direction.

[0066] The transverse stretcher 18 has an oven 30 having different zones for temperature control of the film along the normal running direction and the stretching direction, as described, for example, in German Patent Application Publication No. 102021128332.

[0067] Inside the oven 30, the film F is heated in a known manner and stretched laterally by the transverse stretcher 18, thereby producing a uniaxially oriented film or, as in this embodiment, a biaxially oriented film.

[0068] An optional processing apparatus 20 is, for example, an apparatus for activating the surface of the film F by corona treatment in order to achieve better metallic bonding. Corona treatment can be performed on one side or both sides.

[0069] The winding device 24 is used to wind the manufactured film F and is the last device in the stretching direction. The winding device 24 includes a winding core around which the film F is wound.

[0070] Figure 2 shows a magnified schematic of the casting unit 14 (also called the chill roll unit).

[0071] The casting unit 14 shown herein comprises a slot die 26, a chill roll 28, and an air nozzle device 32 and an optional coating device 34.

[0072] The coating device 34 may be a so-called pinning device, such as an electrostatic coating device ("e-pinning device"). Such coating devices are known, for example, from German Patent Application Publication No. 102022118971. Other coating devices 34 may also be used. For clarity, coating devices 34 are not shown in the remaining figures.

[0073] The chill roll 28 is cooled and is therefore called a "chill roll". The chill roll 28 has an axis that extends in the plane of the drawing and defines the axial direction, an outer circumference that defines the circumferential direction, and a radius that defines the radial direction.

[0074] The chill roll 28 has a circumferential surface 36 around its circumference and is designed to rotate around an axis, thereby moving the circumferential surface 36 in the circumferential direction and the rotational direction R.

[0075] For this purpose, a motor may be provided.

[0076] The slot die 26 is positioned above the chill roll 28 and is designed to continuously apply the molten material 38, which forms the film F, to the chill roll 28. The plastic of the molten material 38 is, in particular, polyethylene terephthalate (PET). The use of other plastics is also possible.

[0077] In the axial direction, the chill roll 28 has a width greater than the width of the molten material 38.

[0078] The slot die 26 and the air nozzle device 32 are also smaller than the molten material 38, the same as the molten material 38, or larger than the molten material 38 but smaller than or equal to the width of the chill roll 28.

[0079] In particular, the molten material 38 is continuous in the axial direction, that is, along its width, and as a result, a continuous film F is produced.

[0080] Figure 3 shows a cross-sectional view passing through Figure 2, which is significantly simplified, similar to Figure 2, in order to explain the principle.

[0081] The slot die 26 is positioned above the chill roll 28, for example, above the top vertex of the chill roll 28. The zero line N of the chill roll 28, i.e., a straight line extending radially through the top vertex of the chill roll 28, therefore intersects the slot die 26.

[0082] The slot die 26 is positioned radially away from the circumferential surface 36 of the chill roll 28 and has an outlet opening 40 through which the molten material 38 is extruded during operation.

[0083] The outlet opening 40 is positioned offset from the zero line N in the rotational direction R, and opens in the rotational direction R and radially toward the circumferential surface 36, as shown in the embodiment, for example.

[0084] The direction of the exit opening 40 corresponds here to the normal direction of the opening. As can be seen in Figure 3, this normal has a component in the rotational direction R and a radial component toward the circumferential surface 36.

[0085] It is also conceivable that the outlet opening 40 opens only toward the circumferential surface 36.

[0086] In the axial direction, the outlet opening 40 is continuous, and its width corresponds to the width of the molten material 38.

[0087] During operation, as shown in Figure 3, the molten material 38 exits through the outlet opening 40 and is deposited on the chill roll 28.

[0088] The axial line in which the molten material 38 contacts the chill roll 28 is called the coating line A. The coating line A is offset in the rotational direction R from the outlet opening 40, and the offset increases as the rotational speed v of the chill roll 28 increases.

[0089] The coating line A and the molten material 38 have a spacing a1 with respect to the zero line N. This can be 30 mm to 100 mm. For example, this spacing a1 is determined along the tangent of the circumferential surface 36 at the intersection with the zero line N. Therefore, the coating line A is not exactly on this tangent, but is slightly offset from the tangent because the diameter of the chill roll 28 is very large compared to the spacing a1.

[0090] The air nozzle device 32 is connected to the slot die 26. For example, as shown in the illustrated embodiment, the air nozzle device 32 is attached to the slot die 26 on the side facing the chill roll 28.

[0091] The entire air nozzle device 32 or the nozzle section 42 may be designed to be movable relative to the slot die 26, particularly in the radial and rotational directions R.

[0092] The air nozzle device 32 has a nozzle section 42 having a nozzle opening 44, as shown in Figure 3.

[0093] The nozzle opening 44 is used to generate airflow 46, as will be described in detail later.

[0094] The nozzle opening 44 and the airflow 46 are designed to be continuous in the axial direction, i.e., along the width. In addition, the width of the airflow 46 and / or the nozzle opening 44 can be narrower than the molten material 38, equal to the molten material 38, or wider than the molten material 38.

[0095] The nozzle opening 44 opens in the opposite direction to the rotational direction R and also has a radially inward component toward the circumferential surface 36. The generated airflow 46 flows toward the circumferential surface 36 in the opposite direction to the rotational direction R and collides with the circumferential surface 36 along the line of action W. The line of action W therefore extends in the axial direction.

[0096] Starting from the zero line N, the action line W and the airflow 46 are offset by a distance a2 in the opposite direction to the rotational direction R. The distance a2 is, for example, 30mm to 145mm. In this case as well, the action line is not exactly tangential.

[0097] The air nozzle device 32 is also spaced radially from the circumferential surface 36.

[0098] As shown in Figure 3, an intermediate space 48 is formed during operation. The intermediate space 48 is defined downward, i.e., radially inward, by the circumferential surface 36 of the chill roll 28; in the rotational direction R, by the molten material 38; upward, by the slot die 26 and partially by the air nozzle device 32; and in the direction opposite to the rotational direction R, by the air nozzle device 32.

[0099] Therefore, the intermediate space 48 is largely isolated from the environment, and as a result, a different air pressure ratio from the environment can be formed within the intermediate space.

[0100] The intermediate space 48 also extends axially and is continuous in the axial direction. The intermediate space 48 can be closed at its axial end face by the cover 50 (Figure 5) of the air nozzle device 32.

[0101] Therefore, the width of the intermediate space 48 is equal to the width of the molten material 38 and / or the outlet opening 40, or greater than the width of the molten material 38 and / or the outlet opening 40.

[0102] It is also possible that the width of the intermediate space 48 is smaller than the width of the molten material 38 and / or the outlet opening 40. In this way, the necessary negative pressure can be generated even when the mass flow rate of the air nozzle device 32 is increased.

[0103] During operation, an airflow 46 is generated. The airflow 46 is directed in the opposite direction to the rotational direction R, that is, outward from the intermediate space 48, and therefore draws air out of the intermediate space 48. Consequently, a negative pressure is generated in the intermediate space 48 due to the Bernoulli effect.

[0104] The airflow 46 can be considered a further boundary of the intermediate space 48.

[0105] For example, negative pressure, i.e., the pressure difference relative to the ambient pressure, can be between 500 Pa and 25,000 Pa, and especially between 500 Pa and 20,000 Pa.

[0106] This negative pressure occurs, for example, at this level, particularly in the region below the molten material 38, i.e., between the molten material 38 and the circumferential surface 36, and / or in the intermediate space 48, in the region from the zero line N toward the molten material 38 in the rotational direction R. For example, the negative pressure occurs from the molten material 38 toward the gap 74.

[0107] As a result of this negative pressure below the molten material 38, the trapping of air between the molten material 38 and the chill roll 28 is significantly reduced.

[0108] In addition, the airflow 46 also reduces potential air trapping in another way. During the operation of the device 10, the chill roll 28 rotates, thereby drawing in air from the environment along the circumferential surface 36. Thus, an air boundary layer is formed along the circumferential surface 36, and this boundary layer moves in the rotational direction R.

[0109] The airflow 46 contacts the circumferential surface 36 in the opposite direction to the rotational direction R, and as a result, the boundary layer is peeled away from the circumferential surface 36 and therefore cannot enter the intermediate space 48 and cannot enter between the molten material 38 and the circumferential surface 36. As a method for manufacturing the film F, during the operation of the apparatus 10, as simplified in Figure 4, the molten material 38 is generated by the slot die 26 (S1) and applied to the chill roll 28 (S2). At the same time, negative pressure is generated in the intermediate space (S3). The film F applied to the chill roll 28 is then finished directly, for example, in a longitudinal stretcher 16 and then in a transverse stretcher 18 (S4).

[0110] Figures 5 to 8 show one embodiment of the casting unit 14 at a more detailed level. However, the additional features and advantages of the casting unit 14 described in relation to these figures are not limited to this embodiment and can generally be easily adapted to other casting units 14 as described above with respect to the figures.

[0111] Figure 5 shows a side view of the casting unit 14 in the region of the apex of the chill roll 28.

[0112] In addition to the nozzle section 42, the air nozzle device 32 also includes a cover 50 that defines an intermediate space 48 on its end face and therefore obstructs the view to the intermediate space 48 in the representation of Figure 5.

[0113] In addition to the cover 50, the air nozzle device 32 includes a control device 51 provided spatially separated from the slot die 26, for example, as shown in the illustrated embodiment.

[0114] The intermediate space 48 is also closed off by another of these covers 50 on the end face opposite the axial direction.

[0115] The cover 50 is movable circumferentially and radially independently of the nozzle section 42, as indicated by the arrows on the cover 50 in Figure 5.

[0116] The position of the cover 50 is selected here so that it is positioned as close as possible to the circumferential surface 36. It is also possible that the cover 50 may be in contact with the circumferential surface 36.

[0117] The cover 50 is positioned axially outside the area where the molten material 38 is applied to the chill roll 28, for example.

[0118] The cover 50 has a contour that corresponds to the contour of the intermediate space 48, or a contour that is larger than this maximum contour, especially at the maximum rotational speed v of the chill roll 28.

[0119] For example, at least one of the covers 50 has a measuring opening 52 extending through the cover 50. On the outside, a tube 54 is provided on the cover that closes the measuring opening 52. The other end of the tube 54 is connected to a pressure sensor 56 of a control device 51.

[0120] Pipe 54 is only partially shown in the diagram.

[0121] In this way, the pressure in the intermediate space 48 can be determined by the control device 51.

[0122] Instead of pipe 54, it is also possible to use a hose or a combination of pipe 54 and a hose.

[0123] The pressure sensor 56 may also be provided directly within the measurement opening 52, or on the cover 50 within the intermediate space 48.

[0124] Figure 6 shows the air nozzle device 32, more specifically the nozzle section 42 and the back of the cover 50. The nozzle section 42 is shown in cross-section. Figure 7 shows the air nozzle device 32, in particular the nozzle section 42, in a bottom view.

[0125] In addition to the nozzle opening 44, the nozzle section 42 includes a reservoir 58, several ducts 60, an inlet chamber 62, and a compressed air source 64. The inlet chamber 62 is an axially extending cavity, and is particularly continuous in the axial direction.

[0126] One or two compressed air sources 64 are positioned on one or both end faces of the inlet chamber 62, and the compressed air sources 64 transport air from the environment into the inlet chamber 62, thus generating positive pressure within the inlet chamber 62. The compressed air sources may be controlled, for example, by a control device 51.

[0127] The compressed air source 64 is, for example, a pipe and / or hose supplied with compressed air from a compressor. The pipe and / or hose may be part of a pipe system and / or hose system. The compressor may be located in one of the spaces separated from the unit and may be controlled by a control device 51.

[0128] For example, the compressed air source 64 includes a pressure regulating valve 65 that controls the input pressure p, i.e., the pressure of the air supplied to the inlet chamber 62.

[0129] The pressure regulating valve 65 is connected to and controlled by the control device 51.

[0130] In addition, to prevent solids that could impair the quality of the film from entering the intermediate space 48, an air filter may be provided on the end face of the inlet chamber 62, or the compressed air source 64 may be equipped with an air filter.

[0131] Starting from the inlet chamber 62, the duct 60 extends, for example, in the form of a pipe or hose, to the reservoir 58.

[0132] The ducts 60 are spaced apart in the axial direction and arranged along the entire width of the inlet chamber 62. The spacing is mostly regular.

[0133] For example, the air nozzle device 32 is equipped with 15 to 25 ducts 60.

[0134] All of the ducts 60 open into reservoir 58.

[0135] Reservoir 58 is a cavity that extends axially and can be continuous in the axial direction.

[0136] The reservoir 58 is closed at the end face.

[0137] The nozzle opening 44 opens outward from the reservoir 58. The reservoir 58 extends across the entire width of the nozzle opening 44, and as a result, the reservoir 58 has a width wider than the airflow 46 and therefore the molten material 38, or the same width as the airflow 46 and therefore the molten material 38.

[0138] The duct 60 opens into the reservoir 58 at regular intervals in the axial direction in order to make the pressure distribution within the reservoir 58 as homogeneous as possible.

[0139] The nozzle opening 44 is designed as a slot, which is the only opening in the reservoir 58 other than the duct 60, as shown in Figure 8, for example.

[0140] For example, as shown in the illustrated embodiment, the nozzle opening 44 is designed as a slot between the first component 68 and the second component 70 of the nozzle section 42, and the reservoir 58 is designed within at least one, in particular both, components 68 and 70.

[0141] Therefore, the nozzle opening 44 is aligned with the surface of the first component 68.

[0142] The flow guide section 66 is designed on the surface of the first component 68.

[0143] For example, the flow guide section 66 is a separate component from the first component 68, and is attached to the first component 68. The flow guide section 66 may be made of PEEK.

[0144] For example, the flow guide section 66 is a component with a wedge-shaped cross-section, with a tip that faces the chill roll 28.

[0145] The flow guide section 66 may also have a rounded shape and / or a convex shape.

[0146] It is also conceivable that the flow guide section 66, together with the first component 68, be designed as a single part.

[0147] The flow guide section 66 has an axial edge 72 formed by its tip. The edge 72 is spaced apart from the circumferential surface 36 and constitutes the point of the nozzle section 42 closest to the circumferential surface 36 of the chill roll 28.

[0148] Therefore, the gap between the edge 72 and the circumferential surface 36 constitutes a gap 74 between the chill roll 28 and the air nozzle device 32, and this gap 74 forms an opening for an intermediate space 48 to the environment.

[0149] The gap 74 is, for example, 0mm to 6mm in the radial direction, and especially 1.5mm to 3.5mm in size.

[0150] The flow guide section 66, and therefore the gap 74, also has at least an axial width corresponding to the width of the nozzle opening 44.

[0151] During the operation of the air nozzle device 32, a positive pressure is generated in the inlet chamber 62 by the compressed air source 64. Consequently, a positive pressure also accumulates in the reservoir 58 through the fluid connection via the duct 60, thereby generating the airflow 46 that exits from the nozzle opening 44.

[0152] The pressure of the airflow 46 can be set by the level of positive pressure in the inlet chamber 62.

[0153] As is clearly visible in Figure 8, the airflow 46 flows in the opposite direction to the rotational direction R along the first component 68 and the flow guide section 66. The airflow 46 then flows through the gap 74 and subsequently contacts the circumferential surface 36 of the chill roll 28 at the line of action W.

[0154] Therefore, the line of action W is located in front of the gap 74 with respect to the rotational direction R. It is also possible that the line of action W is located behind or inside the gap 74.

[0155] The airflow 46 may have a velocity of 50 m / s to 250 m / s, particularly 50 m / s to 200 m / s, in the line of action W and / or gap 74. As a result, as already described, a negative pressure of 5 Pa to 25,000 Pa, for example 500 Pa to 25,000 Pa, particularly 500 Pa to 20,000 Pa, can be achieved in the intermediate space 48. For example, a negative pressure of 5 Pa to 600 Pa, particularly 30 Pa to 150 Pa, can be generated.

[0156] The airflow 46 contacts the circumferential surface 36 at an incidence angle α of 0° to 80°, particularly between 5° and 40°, along the line of action W.

[0157] The angle of incidence α is understood here to mean, for example, the angle between the airflow 46 and the tangent (shown by the dashed line) to the circumferential surface 36 in the line of action W.

[0158] The angle of incidence α is, for example, constant along the axial direction.

[0159] Figure 9 shows a cross-sectional representation of the air pressure levels within the intermediate space 48, within a portion of the reservoir 58, and in front of the gap 74 during the operation of the apparatus 10. The components of the casting unit 14, as well as the apparatus 10 and the molten material 38, are not shown. However, their locations are identified by corresponding reference numerals for ease of reference.

[0160] It is clear that the air pressure in the intermediate space 48 is considerably lower than that in front of the gap 74, and therefore a negative pressure is formed within the intermediate space 48. In addition, the negative pressure within the intermediate space 48 is almost homogeneous.

[0161] The control device 51 may be used to automatically control the casting unit 14.

[0162] The control device 51 controls the pressure regulating valve 65, thereby setting the level of positive pressure in the inlet chamber 62, and therefore the pressure of the airflow 46, which then affects the level of negative pressure in the intermediate space 48.

[0163] For example, the control device 51 receives the speed v of the chill roll 28 as the sole input quantity or as one of the input quantities. This may be the desired speed and / or the actual speed of the chill roll 28.

[0164] The control device 51 uses the speed v of the chill roll 28 to establish a control signal for the pressure regulating valve 65 that indicates, for example, a desired value of the input pressure p and / or negative pressure in the intermediate space 48. The control signal may also indicate a desired opening width of the pressure regulating valve 65.

[0165] The control device 51 outputs a control signal to the pressure regulating valve 65, which receives the control signal and adjusts its opening width according to the control signal.

[0166] The actual value of the input pressure p can be determined, for example, by a pressure sensor 56, and can also be used as the input quantity for the control device 51.

[0167] For example, the dependency of a desired input pressure p on the speed v of the chill roll 28 is stored in the control device 51. This dependency can occur as a lookup table and / or function.

[0168] An example of such a lookup table is reproduced below.

[0169] [Table 1]

[0170] Figure 10 shows a graph containing two exemplary curves illustrating the dependency of the input pressure p on the velocity v of the chill roll 28. The dashed line shows a linear dependency, and the dotted line shows a nonlinear dependency, in the form of an S-curve.

[0171] It is also conceivable that the desired value of the input pressure p depends on more than one input quantity. Possible input quantities, individually or in combination, are as follows: namely, the speed v of the chill roll 28, the film production speed of the casting unit 14 and / or the device 10 for producing the film F, the thickness of the film F, the material of the film F, and / or the temperature of the film F.

[0172] The pressure regulating valve 65 may be a manual valve and / or manually operable. The input pressure, which affects the level of negative pressure in the intermediate space 48, the level of positive pressure in the inlet chamber 62, and therefore the pressure of the airflow 46, can also be adjusted manually. By manually adjusting the input pressure, it is also possible to omit the control device.

Claims

1. A casting unit for a device (10) for manufacturing a film (F), comprising a slot die (26), a chill roll (28), and an air nozzle device (32), The chill roll (28) is provided with a circumferential surface (36) and is designed to rotate around an axis such that the circumferential surface (36) moves in the rotational direction (R). The slot die (26) is designed to generate a molten material (38) that comes into contact with the circumferential surface (36) in the coating line (A). The air nozzle device (32) is connected to the slot die (26) such that an intermediate space (48) is defined by the circumferential surface (36) of the chill roll (28), the molten material (38), the slot die (26), and the air nozzle device (32). The air nozzle device (32) is designed to generate an airflow (46) that collides with the circumferential surface (36) along the line of action (W) in the opposite direction to the rotational direction (R), generating a negative pressure in the intermediate space (48). Casting unit.

2. The casting unit according to claim 1, wherein the slot die (26) includes an outlet opening (40) that opens in the rotational direction (R) and / or radially toward the circumferential surface (36).

3. The casting unit according to claim 1 or 2, wherein the outlet opening (40) and / or the molten material (38) has a width in the axial direction, and the width in the axial direction of the intermediate space (48), the airflow (46) and / or the air nozzle device (32) is less than the width of the outlet opening (40) and / or the molten material (38), equal to the width of the outlet opening (40) and / or the molten material (38), or greater than the width of the outlet opening (40) and / or the molten material (38).

4. The casting unit according to claim 1, wherein the outlet opening (40), the molten material (38), the intermediate space (48), and / or the airflow (46) are continuous in the axial direction.

5. The casting unit according to claim 1, wherein the air nozzle device (32) comprises a flow guide section (66) that defines a gap (74) between the chill roll (28) and the air nozzle device (32), and the airflow (46) flows through the gap (74).

6. The casting unit according to claim 5, wherein the gap (74) is 0 mm to 6 mm or 1.5 mm to 3.5 mm.

7. The casting unit according to claim 1, wherein the airflow (46) in the working line (W) and / or the gap (74) has a velocity of 50 m / s to 250 m / s or 50 m / s to 200 m / s.

8. The casting unit according to claim 1, wherein the negative pressure in the intermediate space (48) is 5 Pa to 25,000 Pa.

9. The casting unit according to claim 1, wherein the coating line (A) is offset in the rotational direction (R), and / or the action line (W) is offset from the zero line (N) in the opposite direction to the rotational direction (R).

10. The casting unit according to claim 1, wherein the airflow (46) contacts the circumferential surface (36) at an incident angle (α), and the incident angle (α) is 0° to 80° or 5° to 40°.

11. The casting unit according to claim 1, wherein the air nozzle device (32) is attached to the slot die (26), and / or the air nozzle device (32) is designed to be movable relative to the slot die (26).

12. The air nozzle device (32) is The nozzle opening (44) opening toward the line of action (W), the gap (74) and / or the flow guide section (66), The casting unit according to claim 1, having a nozzle section (42) equipped with

13. The casting unit according to claim 12, wherein the air nozzle device (32) comprises at least one compressed air source (64) designed to deliver air to the nozzle opening (44) to generate the airflow (46).

14. The casting unit according to claim 12, wherein the air nozzle device (32) comprises a reservoir (58), and the nozzle opening (44) extends from the reservoir (58).

15. The casting unit according to claim 14, wherein the air nozzle device (32) or the nozzle section (42) comprises an inlet chamber (62) and several ducts (60), the ducts (60) fluidly connecting the inlet chamber (62) to the reservoir (58).

16. The casting unit (14) is equipped with a control device (51), and the air nozzle device (32) is equipped with at least one compressed air source (64) which includes a pressure regulating valve (65). The control device (51) is connected to the pressure regulating valve (65) and is configured to control the pressure regulating valve (65). The casting unit according to claim 1.

17. The casting unit according to claim 16, wherein the control device (51) is configured to receive the speed (v) of the chill roll (28) as an input quantity and to output a control signal for the pressure regulating valve (65) to the pressure regulating valve (65) based on at least the speed (v) of the chill roll (28).

18. The casting unit according to claim 1, wherein the air nozzle device (32) comprises two end face covers (50) which are each positioned on one of the end faces of the intermediate space (48) and which close the intermediate space (48) in the axial direction, and at least one of the covers (50) comprises a measuring opening (52) which is fluidly connected to a pressure sensor (56) and / or a pressure sensor (56).

19. An apparatus for manufacturing a film (F), comprising a casting unit (14) and stretchers (16, 18) as described in claim 1.

20. A method for producing a film (F) using the apparatus (10) described in claim 19, A method comprising: a molten material (38) being generated by a slot die (26) and applied to the chill roll (28), while simultaneously generating negative pressure in the intermediate space (48).

21. The method according to claim 20, wherein the level of negative pressure in the intermediate space (48) is controlled by a control device (51) of the casting unit (14), or the level of negative pressure in the intermediate space (48) is controlled by a control device (51) of the casting unit (14) based at least on the speed (v) of the chill roll (28).

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