A cast unit, a unit for producing a film, and a method for producing a film

Abstract

A casting unit (14) of a unit (10) for producing a film (F) comprises a slit die (26), a cooling roller (28) and an air nozzle device (32). The cooling roller (28) comprises at least one circumferential surface (36) and is designed to rotate about an axis such that the circumferential surface (36) moves in a rotational direction (R), wherein the slit die (26) is configured to generate a melt (38). The air nozzle device (32) is connected to the slit die (26) such that the circumferential surface (36) of the cooling roller (28), the melt (38), the slit die (26) and the air nozzle device (32) are delimited by an intermediate space (48), wherein the air nozzle device (32) is designed to generate an air flow (46) which impinges on the circumferential surface (36) against the rotational direction (R) along a line of action (W) and generates a negative pressure in the intermediate space (48). Furthermore, a unit (10) for producing a film (F) as well as a method are provided.

Description

Technical Field

[0001] This invention relates to a casting unit, a unit for producing films, and a method for producing films. Background Technology

[0002] In the production of thin plastic films, the molten plastic film is initially applied to a cooling roller, where it is cooled and hardened. Here, air bubbles may become trapped between the molten plastic and the cooling roller, becoming part of the film and thus impairing its quality.

[0003] To avoid air trapped between the molten plastic and the cooling rollers, it is known to arrange a shroud before the molten plastic is applied, extending counter-rotatingly below the slit mold. Air is then extracted from this shroud to create a vacuum, thereby reducing trapped air. For example, US 5,618,568 A illustrates such a solution.

[0004] The problem with this solution is that, to achieve a noticeable effect, the shroud needs to be positioned very close to the cooling rollers in order to generate a sufficiently large vacuum. This makes the unit setup difficult and time-consuming, thus reducing its economic efficiency. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a casting unit, a unit for producing films, and a method thereof, wherein the air trapped between the plastic melt and the cooling roller is reduced in a simple manner.

[0006] This objective is achieved by means of a casting unit for producing a film, the casting unit comprising a slit die, a cooling roller, and an air nozzle assembly. The cooling roller has a circumferential surface and is designed to rotate about an axis, such that the circumferential surface moves in the direction of rotation. The slit die is designed to generate a melt that contacts the circumferential surface at the application line. The air nozzle assembly is connected to the slit die such that an intermediate space is defined by the circumferential surface of the cooling roller, the melt, the slit die, and the air nozzle assembly, wherein the air nozzle assembly is designed to generate an airflow that impacts the circumferential surface along the line of action against the direction of rotation, and generates a negative pressure in the intermediate space.

[0007] Since the negative pressure is generated by the airflow on the circumferential surface of the contact cooling rollers, the intermediate space is tightly sealed along its width, making it easy to generate negative pressure. Furthermore, there is no need to precisely position larger components, such as shrouds.

[0008] Specifically, negative pressure exists in the region below the melt and / or in the section of the intermediate space starting from the zero line in the direction of rotation.

[0009] Furthermore, the airflow in contact with the circumferential surface causes the boundary layer of the air moving with the circumferential surface to detach from it. In this way, the amount of air trapped in the melt can be further reduced.

[0010] Within the scope of this disclosure, the direction of rotation corresponds to the direction in the circumferential direction defined by the circumferential direction of the cooling roller. Similarly, the axial direction may be defined by the axial direction of the cooling roller.

[0011] In particular, the application line and the line of action extend in the axial direction.

[0012] Airflow can also define intermediate spaces. Specifically, airflow transports air out of intermediate spaces.

[0013] The casting unit may include an application device designed to apply the melt particularly uniformly and reliably onto the cooling rollers. The application device may be a so-called "pinning device," such as an electrostatic application device ("e-pinning device"). Such an application device is known, for example, from DE 10 2022 118 971 A1. Other pinning devices may also be used.

[0014] In one embodiment, the slit mold includes an outlet opening that opens toward a circumferential surface in the rotational and / or radial direction, thereby allowing the melt to be applied to the cooling roller in a particularly controlled manner.

[0015] The direction of the opening, that is, the direction perpendicular to the opening, for example, has a component in the rotational direction and a component in the radial direction toward the circumferential surface.

[0016] The outlet opening can be offset relative to the zero line in the direction of rotation.

[0017] In one embodiment, the outlet opening and / or the melt has a width in the axial direction, and the width of the intermediate space, airflow, and / or air nozzle assembly in the axial direction is less than, equal to, or greater than the width of the outlet opening and / or the melt. In this way, it is ensured that air trapped across the entire width of the melt is avoided.

[0018] The width of the cooling roller is equal to or greater than the width of the air nozzle device, the airflow and / or the melt.

[0019] To avoid irregularities in the membrane, the outlet opening, melt, intermediate space and / or airflow can be continuous in the axial direction.

[0020] In one embodiment, the air nozzle device includes a flow guide section defining a gap between the cooling roller and the air nozzle device, through which airflow flows, particularly where the gap is between 0 mm and 6 mm, and more particularly between 1.5 mm and 3.5 mm. The negative pressure in the intermediate space can be adjusted by means of the size of the gap.

[0021] The negative pressure in the intermediate space can be adjusted by the positive pressure level provided by a compressed air source.

[0022] For example, the flow guide section is wedge-shaped, rounded, and / or convex, with its tip pointing towards the cooling roller. The flow guide section can be made of polyetheretherketone (PEEK).

[0023] The line of action, especially in the gap, is either in front of the gap or behind the gap relative to the direction of rotation.

[0024] In one embodiment, the airflow at the line of action and / or in the gap has a velocity between 50 m / s and 250 m / s, particularly between 50 m / s and 200 m / s, and / or the negative pressure in the intermediate space is between 500 Pa and 25,000 Pa, particularly between 5 Pa and 25,000 Pa, for example between 5 Pa and 600 Pa, particularly between 30 Pa and 150 Pa, or between 500 Pa and 20,000 Pa, thereby making it possible to further reduce the trapped air.

[0025] Negative pressure data should be understood as the pressure difference relative to ambient pressure.

[0026] To produce particularly high-quality films, the application line may be offset in the direction of rotation and / or the action line may be offset relative to the zero line in the opposite direction of rotation, in particular where the zero line corresponds to a radially extending straight line passing through the apex of the cooling roller in the correct assembly position.

[0027] The vertex is also called the 12 o'clock position.

[0028] The distance between the zero line and the melt and / or the applied line can be between 30 mm and 100 mm, and the distance between the zero line and the air flow and / or the applied line can be between 30 mm and 145 mm, each measured along the tangent at the zero line.

[0029] In order to effectively remove the boundary layer, in particular from the cooling rollers, the airflow can contact the circumferential surface at an incident angle between 0° and 80°, and especially between 5° and 40°.

[0030] Within the scope of this disclosure, the angle of incidence is understood to mean the angle between the airflow and the tangent at the line of action.

[0031] The angle of incidence is particularly constant along the width of the airflow.

[0032] For space-saving integration, the air nozzle device can be attached to the slit mold, particularly to the side of the slit mold facing the cooling roller.

[0033] The air nozzle device can be designed to be movable relative to the slit mold so that the position of the airflow and / or gap can be adjusted according to the environment (e.g., the material of the film to be produced).

[0034] 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. Specifically, the air nozzle device includes at least one compressed air source designed to deliver air to the nozzle opening to generate an airflow. In this way, an airflow exiting the nozzle opening can be generated in a controlled manner.

[0035] The compressed air source can be arranged on the end face of the air nozzle device. It is conceivable to provide two included air sources, for example, arranged on two opposite end faces of the air nozzle device.

[0036] The compressed air source is, for example, at least a pipe and / or hose, such as a pipe and / or hose system. This can be achieved, for example, by means of a compressor that is part of the compressed air source. The compressor may be located in a separate space from the unit.

[0037] In one aspect, the air nozzle device includes a reservoir from which a nozzle opening extends. The reservoir generates a uniform pressure in the axial direction, thereby producing a uniform airflow.

[0038] Specifically, the width of the nozzle opening and / or reservoir is equal to or greater than the width of the melt. The nozzle opening and / or reservoir are continuous, for example, along the entire length.

[0039] An air nozzle device, particularly a nozzle section, may include an inlet chamber and several conduits to maintain a constant pressure in a reservoir in the axial direction, wherein the conduits fluidly connect the inlet chamber to the reservoir, and wherein the at least one compressed air source is arranged on the end face of the inlet chamber.

[0040] Specifically, the inlet chamber is continuous along its width. The width of the inlet chamber can correspond to the width of the reservoir.

[0041] In one embodiment, the casting unit has a control device, and the air nozzle assembly has at least one compressed air source including a pressure regulating valve. The control device is connected to the pressure regulating valve and is configured to control the pressure regulating valve. In this way, the negative pressure in the intermediate space can be precisely and automatically set, particularly to prevent the melt from wobbling before contacting the cooling rollers.

[0042] For example, the control device is configured to receive the speed of the cooling roller as an input quantity, and output a control signal for the pressure regulating valve based at least on the speed of the cooling roller.

[0043] In particular, the pressure regulating valve affects the negative pressure level in the inlet chamber, thereby affecting the airflow pressure and the negative pressure in the intermediate space.

[0044] It is also conceivable to manually set the negative pressure level and / or input pressure in the oral cavity. For example, a pressure regulating valve is a manually actuable valve.

[0045] To increase the negative pressure in the intermediate space, the air nozzle device may include two end face covers, which are respectively arranged on one of the end faces of the intermediate space and close the intermediate space in the axial direction. In particular, at least one of the covers includes a pressure sensor and / or a measuring opening for fluid connection to the pressure sensor.

[0046] For example, the cover can move independently of the nozzle section of the air nozzle device in the circumferential and radial directions.

[0047] Furthermore, this objective is achieved by means of a unit for producing a film, which includes a casting unit and a stretching unit as previously described, particularly a transverse orientation oriented device, a machine orientation oriented device and / or a simultaneous stretching unit.

[0048] The features and advantages described for the casting element also apply to this element, and vice versa.

[0049] This objective is also achieved by means of a method for producing membranes using a unit as previously described, wherein a melt is generated by means of a slit mold and applied to a cooling roller, wherein a negative pressure is simultaneously generated in the intermediate space.

[0050] The features and advantages of the cast elements and / or element descriptions also apply to this method, and vice versa.

[0051] For example, the negative pressure level in the intermediate space is controlled by the control equipment of the casting unit, particularly based on at least the speed of the cooling roller. Attached Figure Description

[0052] Additional features and advantages of the invention can be found in the following description and the accompanying drawings. In the drawings:

[0053] Figure 1 A schematic diagram of a unit according to an embodiment of the present invention is shown, the unit including a casting unit according to an embodiment of the present invention.

[0054] Figure 2 A schematic perspective view shows the situation based on... Figure 1 The casting unit,

[0055] Figure 3 The cross-section shows the results according to Figure 2 A schematic diagram of the principle of the casting unit.

[0056] Figure 4 A flowchart illustrating an embodiment of the method according to the present invention is shown.

[0057] Figure 5 A detailed side view of the casting unit according to an embodiment of the present invention is shown.

[0058] Figure 6 It shows according to Figure 5 A cross-sectional view of the air nozzle device of the application equipment.

[0059] Figure 7 It shows according to Figure 5 A lower view of a portion of the applying device.

[0060] Figure 8 It shows according to Figure 5 An enlarged cross-sectional view of the air nozzle device of the application equipment in the area of ​​airflow.

[0061] Figure 9 The air pressure in the intermediate space is shown, and

[0062] Figure 10 A graph with two exemplary curves is shown, which illustrate the dependence of the desired inlet pressure on the cooling roller speed. Detailed Implementation

[0063] exist Figure 1 The diagram illustrates, in a highly schematic manner, a unit 10 for producing membrane F, which comprises several different units and devices.

[0064] For example, unit 10 is a sequential membrane production unit, by means of which there are no limitations on the scope of protection, and the present invention is explained by way of example.

[0065] In the example shown, unit 10 includes extrusion unit 12, casting unit 14, at least one machine orientation orienter 16 (MDO), transverse orientation orienter 19 (TDO), processing device 20, and winding device 24.

[0066] The extrusion unit 12 includes an extruder and is configured to generate a melt from at least one starting product. The melt is a plastic melt.

[0067] For example, one or more extruders are single-screw extruders, cascade extruders, and / or twin-screw extruders.

[0068] It is also conceivable to use other mixing and processing units, such as a Buss kneader or a planetary roll extruder.

[0069] Similarly, a melt can be generated by polymerization. For this purpose, monomers (and optional additives, such as catalysts) are mixed and polymerized in the reactor and / or extruder of extrusion unit 12.

[0070] The melt can be applied directly to the cooling roller 28 of the casting unit 14 via the slit mold 26 of the casting unit 14, thereby generating film F.

[0071] The cooling roller 28 has a diameter, for example, between 50 cm and 4 m.

[0072] The resulting film F may comprise one or more layers. In the case of a multilayer film, it is conceivable that an extruder can generate several or all of the layers, or that an extruder can be provided for each layer.

[0073] Subsequently, the membrane F is fed to the machine orientation orienter 16, where it is stretched in the machine direction.

[0074] For example, the transverse orienter 18 described in DE 10 2021 128 332 A1 has an oven 30 with different zones for controlling the temperature of the membrane along the usual direction of travel and the direction of tension.

[0075] In oven 30, the membrane F is heated in a known manner and stretched in the lateral direction by lateral orientation 18 to produce a uniaxially oriented membrane, or, as in this embodiment, a biaxially oriented membrane.

[0076] Optional processing device 20 is, for example, a device for activating the surface of the film F by means of corona treatment, in order to achieve, for example, better metal bonding. Corona treatment can be performed on one side or both sides.

[0077] The winding device 24 is used to wind the produced film F and is the last device in the stretching direction. It includes a winding core on which the film F is wound.

[0078] exist Figure 2 The enlarged schematic diagram shows the casting unit 14 (also known as the cooling roller unit).

[0079] The casting unit 12 shown here includes a slit mold 26, a cooling roller 28, an air nozzle device 32, and an optional application device 34.

[0080] The application device 34 can be a so-called pinning device, such as an electrostatic application device (“e-pinning device”). Such an application device is known, for example, from DE 10 2022 118 971 A1. Other application devices 34 may also be used. For clarity, the application device 34 is not shown in the remaining figures.

[0081] The cooling roller 28 is cooled and is therefore referred to as a "cooling roller". It has an axis extending into the drawing plane and defining the axial direction, an outer circumference defining the circumferential direction, and a radius defining the radial direction.

[0082] The cooling roller 28 has a circumferential surface 36 on its circumference and is designed to rotate about an axis, so that the circumferential surface 36 moves in the circumferential direction in the rotation direction R.

[0083] For this purpose, a motor can be provided.

[0084] A slit mold 26 is positioned above a cooling roller 28 and is designed to continuously apply the melt 38 forming the film F to the cooling roller 28. The plastic of the melt 38 is, in particular, polyethylene terephthalate (PET). Other plastics are conceivable.

[0085] In the axial direction, the width of the cooling roller 28 is greater than the width of the melt 38.

[0086] The width of the slit mold 26 and the air nozzle device 32 is also less than, equal to or greater than the width of the melt 38, but less than or equal to the width of the cooling roller 28.

[0087] In particular, the melt 38 is continuous in the axial direction, that is, along its width, thereby generating a continuous film F.

[0088] exist Figure 3 In the middle, it is shown that passing through Figure 2 The sectional view, it is also like Figure 2 It has also been greatly simplified in order to explain the principle.

[0089] The slit mold 26 is arranged above the cooling roller 28, for example, above the upper vertex of the cooling roller 28. The zero line N of the cooling roller 28, that is, the straight line extending radially through the upper vertex of the cooling roller 28, intersects with the slit mold 26.

[0090] The slit die 26 is arranged radially spaced from the circumferential surface 36 of the cooling roller 28 and has an outlet opening 40 from which the melt 38 is extruded during operation.

[0091] The outlet opening 40 is arranged in the rotation direction R to be offset relative to the zero line N, and, for example, as shown in the embodiment, the outlet opening 40 is open in the rotation direction R and in the radial direction toward the circumferential surface 36.

[0092] The direction of the outlet opening 40 corresponds here to the direction normal to the opening. For example, in Figure 3 As can be seen, the normal has a component in the rotation direction R and a component in the radial direction toward the circumferential surface 36.

[0093] It can also be envisioned that the outlet opening 40 is open only toward the circumferential surface 36.

[0094] In the axial direction, the outlet opening 40 is continuous and its width corresponds to the width of the melt 38.

[0095] During operation, such as in Figure 3 As shown, melt 38 exits the outlet opening 40 and deposits on the cooling roller 28.

[0096] The line in which the melt 38 contacts the cooling roller 28 in the axial direction is called the application line A. The application line A is offset from the outlet opening 40 in the rotational direction R, and this offset increases with the increase of the rotational speed v of the cooling roller 28.

[0097] The application line A and the melt 38 have a distance a1 from the zero line N. This can be between 30 mm and 100 mm. For example, this distance a1 is determined along the tangent at the intersection of the circumferential surface 36 and the zero line N. Therefore, the application line A is not exactly on this tangent, but only slightly offset relative to the tangent, because the diameter of the cooling roller 28 is very large compared to the distance a1.

[0098] An air nozzle device 32 is connected to a slit mold 26. For example, as in the illustrated embodiment, the air nozzle device 32 is attached to the slit mold 26 on the side of the slit mold 26 facing the cooling roller 28.

[0099] The entire air nozzle assembly 32 or nozzle section 42 can be designed to be movable relative to the slit mold 26, particularly in the radial and rotational directions R.

[0100] The air nozzle device 32 has a nozzle section 42, such as Figure 3 As shown, the nozzle section 42 has a nozzle opening 44.

[0101] Nozzle opening 44 is used to generate airflow 46, as will be described in detail.

[0102] 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 may be less than, equal to or greater than the melt 38.

[0103] The nozzle opening 44 opens against the direction of rotation R and also has a component that extends radially inward toward the circumferential surface 36. The generated airflow 46 flows against the direction of rotation R and toward the circumferential surface 36, and impacts the circumferential surface 36 along the line of action W. The line of action W extends accordingly in the axial direction.

[0104] Starting from the zero line N, the line of action W and the airflow 46 are offset by a distance a2 against the direction of rotation R. The distance a2 is, for example, between 30 mm and 145 mm. Again, here, the line of action is not exactly tangential.

[0105] The air nozzle device 32 is also radially spaced from the circumferential surface 36.

[0106] As in Figure 3 As can be seen, an intermediate space 48 is formed during operation. This intermediate space 48 is downward and thus radially inward defined by the circumferential surface 36 of the cooling roller 28, defined in the rotational direction R by the melt 38, and upward defined by the slit mold 26 and partly by the air nozzle device 32, as well as in the opposite direction of rotation R by the air nozzle device 32.

[0107] Therefore, the intermediate space 48 is largely separated from the environment, which allows for the formation of different pressure ratios in the intermediate space compared to the environment.

[0108] The intermediate space 48 also extends in the axial direction and is continuous in the axial direction. The intermediate space 48 can be covered by the cover 50 of the air nozzle device 32. Figure 5 It is closed on the end face in the axial direction.

[0109] Therefore, the width of the intermediate space 48 is equal to or greater than the width of the melt 38 and / or the outlet opening 40.

[0110] It is also conceivable that the width of the intermediate space 48 is smaller than the width of the melt 38 and / or the outlet opening 40. In this way, the required negative pressure can also be generated if the mass flow rate of the air nozzle device 32 increases.

[0111] During operation, an airflow 46 is generated. This airflow 46 is directed against the direction of rotation R, i.e., exiting from the intermediate space 48, and thus carrying air out of the intermediate space 48. Due to the Bernoulli effect, a negative pressure is thus created in the intermediate space 48.

[0112] Airflow 46 can be considered a further definition of intermediate space 48.

[0113] For example, negative pressure, which is the pressure difference relative to ambient pressure, can be between 500 Pa and 25,000 Pa, especially between 500 Pa and 20,000 Pa.

[0114] This negative pressure, for example at this level, specifically occurs in the region below the melt 38, i.e., between the melt 38 and the circumferential surface 36, and / or in the region of the intermediate space 48 from the zero line N toward the melt 38 in the rotational direction R. For example, a negative pressure is generated from the melt 38 to the gap 74.

[0115] Due to the negative pressure below the melt 38, the air trapped between the melt 38 and the cooling roller 28 is significantly reduced.

[0116] Furthermore, the airflow 46 reduces potential air trapping in another way. During operation of unit 10, the cooling roller 28 rotates, thereby drawing air from the environment along the circumferential surface 36. Thus, an air boundary layer is formed along the circumferential surface 36, which moves in the rotational direction R.

[0117] Airflow 46 contacts circumferential surface 36 against the direction of rotation R, resulting in the boundary layer detaching from circumferential surface 36 and thus preventing it from entering the intermediate space 48 and reaching between melt 38 and circumferential surface 36. During operation of unit 10, as a method for producing film F, such as... Figure 4 As simplified in the diagram, melt 38 is generated by means of slit mold 26 (S1) and applied to cooling roller 28 (S2). Simultaneously, a negative pressure is generated in the intermediate space (S3). The film F applied to cooling roller 28 is then directly finished (S4), for example in machine orientation orienter 16, and then in transverse orientation orienter 18.

[0118] exist Figures 5 to 8 The accompanying drawings illustrate an embodiment of the casting unit 14 in more detail. However, the additional features and advantages of the casting unit 14 described in conjunction with these drawings are not limited to this embodiment, but can also be readily transferred individually to other casting units 14, as described above with reference to the accompanying drawings. Figure 1 Generally described.

[0119] Figure 5 A side view of the casting unit 14 in the apex region of the cooling roller 28 is shown.

[0120] In addition to the nozzle section 42, the air nozzle assembly 32 also includes a cover 50, which defines an intermediate space 48 on the end face, and thus... Figure 5 The view in the intermediate space 48 is obscured in the representation.

[0121] In addition to the cover 50, the air nozzle device 32 also includes a control device 51, which is configured to be spatially separate from the slit mold 26, for example, as in the illustrated embodiment.

[0122] The intermediate space 48 is also closed by another of these coverings 50 on the axially opposite end faces.

[0123] like Figure 5 As shown by the arrow on the cover 50, the cover 50 can move independently of the nozzle section 42 in the circumferential and radial directions.

[0124] The positions of the coverings 50 are chosen such that they are positioned at the smallest possible distance from the circumferential surface 36. It is also conceivable that the outlet opening 50 contacts the circumferential surface 36.

[0125] The cover 50 is located, for example, outside the area in the axial direction where the melt 38 is applied to the cooling roller 28.

[0126] The cover 50 has a profile corresponding to the profile of the intermediate space 48, particularly the profile of the intermediate space 48 at the maximum rotational speed v of the cooling roller 28, or a profile greater than that maximum profile.

[0127] 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 to close the measuring opening 52. The other end of the tube 54 is connected to a pressure sensor 56 of the control device 51.

[0128] Only part of tube 54 is shown in the figure.

[0129] In this way, the pressure in the intermediate space 48 can be determined by the control device 51.

[0130] It is also conceivable to use a flexible tube or a combination of tube 54 and flexible tube to replace tube 54.

[0131] It is also conceivable that the pressure sensor 56 is directly disposed in the measuring opening 52 within the intermediate space 48 or on the covering 50.

[0132] exist Figure 6 The image shows an air nozzle assembly 32, and more specifically, the back of the nozzle section 42 and the cover 50. The nozzle section 42 is shown in cross-section. Figure 7 The following side view shows the air nozzle assembly 32, and in particular the nozzle section 42.

[0133] In addition to the nozzle opening 44, the nozzle section 42 also includes a reservoir 58, several pipes 60, an inlet chamber 62, and a compressed air source 64. The inlet chamber 62 is a cavity extending in the axial direction, particularly a cavity that is continuous in the axial direction.

[0134] One or two compressed air sources 64 are arranged on one or both end faces of the inlet oral cavity 62, which supply air from the environment into the inlet oral cavity 62 and thus generate positive pressure in the inlet oral cavity 62. The compressed air sources (one or more) may be controlled, for example, by a control device 51.

[0135] Compressed air source 64 is, for example, a pipe and / or hose that supplies compressed air from the 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 separate from the unit and may be controlled by control device 51.

[0136] For example, compressed air source 64 includes pressure regulating valve 65, which controls input pressure p, i.e., the pressure of the air supplied to inlet chamber 62.

[0137] The pressure regulating valve 65 is connected to and controlled by the control device 51.

[0138] In addition, an air filter may be provided on the end face of the inlet chamber 62, or the compressed air source 64 may include an air filter to prevent solids from entering the intermediate space 48, which could damage the quality of the membrane.

[0139] Starting from the oral cavity 62, the conduit 60 extends, for example, in the form of a tube or hose, to the reservoir 58.

[0140] The conduits 60 are arranged axially and spaced apart along the entire width of the inlet chamber 62. The spacing is mostly regular.

[0141] For example, the air nozzle device 32 includes 15 to 25 pipes 60.

[0142] All pipes 60 lead to storage device 58.

[0143] The storage device 58 is a cavity that extends in the axial direction and can be continuous in the axial direction.

[0144] The storage device 58 is closed on the end face.

[0145] The nozzle opening 44 leads out of the reservoir 58. The reservoir 58 extends over the entire width of the nozzle opening 44 such that the width of the reservoir 58 is greater than or equal to the width of the airflow 46, and therefore greater than or equal to the width of the melt 38.

[0146] Pipe 60 extends into reservoir 58 at regular intervals in the axial direction in order to achieve the most uniform pressure distribution possible within reservoir 58.

[0147] For example, such as Figure 8In this design, the nozzle opening 44 is designed as a slot, which is the only opening of the reservoir 58 other than the pipe 60.

[0148] For example, as in the illustrated embodiment, the nozzle opening 44 is designed as a slot between the first part 68 and the second part 70 of the nozzle section 42, wherein the reservoir 58 is designed in at least one, particularly both parts 68, 70.

[0149] Therefore, the nozzle opening 44 is aligned with the surface of the first component 68.

[0150] The flow guide section 66 is designed in the surface of the first component 68.

[0151] For example, the flow guide section 66 is a component separate from and attached to the first component 68. The flow guide section 66 may be made of PEEK.

[0152] For example, the flow guide section 66 is a wedge-shaped component in cross-section, which includes a tip facing the cooling roller 28.

[0153] The flow guide section 66 can also be rounded and / or convex.

[0154] It is also conceivable that the flow guide section 66, together with the first component 68, is designed as a single piece.

[0155] The flow guide section 66 has an edge 72 formed by a tip in the axial direction. The edge 72 is arranged to be spaced apart from the circumferential surface 36, wherein the edge 72 constitutes the point of the nozzle section 42 closest to the circumferential surface 36 of the cooling roller 28.

[0156] Therefore, the gap between the edge 72 and the circumferential surface 36 forms the gap 74 between the cooling roller 28 and the air nozzle device 32, which forms an opening of the intermediate space 48 toward the environment.

[0157] The size of the gap 74 is, for example, between 0 mm and 6 mm in the radial direction, and particularly between 1.5 mm and 3.5 mm.

[0158] The flow guide section 66 and therefore the gap 74 have a width in the axial direction that corresponds at least to the width of the nozzle opening 44.

[0159] During operation of the air nozzle device 32, the compressed air source 64 generates positive pressure in the inlet chamber 62. Therefore, due to the fluid connection via the pipe 60, positive pressure also accumulates in the reservoir 58, thereby generating an airflow 46 that flows out from the nozzle opening 44.

[0160] The pressure of the airflow 46 can be set by the positive pressure level in the inlet chamber 62.

[0161] As in Figure 8 As can be clearly seen, the airflow 46 flows against the direction of rotation 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 cooling roller 28 at the line of action W.

[0162] Therefore, relative to the direction of rotation R, the line of action W is located before the gap 74. It is also conceivable that the line of action W is located behind or within the gap 74.

[0163] The airflow 46 can have a velocity between 50 m / s and 250 m / s, particularly between 50 m / s and 200 m / s, at the line of action W and / or in the gap 74. As a result, as already described, a negative pressure between 5 Pa and 25,000 Pa, for example between 500 Pa and 25,000 Pa, particularly between 500 Pa and 20,000 Pa, can be achieved in the intermediate space 48. For example, a negative pressure between 5 Pa and 600 Pa, particularly between 30 Pa and 150 Pa, can be generated.

[0164] At the line of action W, the airflow 46 contacts the circumferential surface 36 at an incident angle α between 0° and 80°, particularly between 5° and 40°.

[0165] The angle of incidence α is understood here, for example, as the angle between the airflow 46 and the tangent (shown as a dashed line) at the line of action W of the circumferential surface 36.

[0166] The incident angle α is constant, for example, along the axial direction.

[0167] Figure 9 A cross-sectional view showing the air pressure levels in the intermediate space 48, in the portion of the reservoir 58, and in front of the gap 74 during operation of unit 10 is shown. Components of casting unit 14, as well as unit 10 and melt 38, are not shown. However, for ease of reference, their locations are indicated by corresponding reference numerals.

[0168] It can be clearly seen that the air pressure in the intermediate space 48 is much lower than that before the gap 74, thus creating a negative pressure in the intermediate space 48. Furthermore, the negative pressure in the intermediate space 48 is mostly uniform.

[0169] The control device 51 can be used to automatically control the casting unit 14.

[0170] Control device 51 controls pressure regulating valve 65, thereby setting the positive pressure level in inlet chamber 62 and thus setting the pressure of airflow 46, which in turn affects the negative pressure level in intermediate space 48.

[0171] For example, control device 51 receives the speed v of cooling roller 28 as a single input or as one of the inputs. This can be the desired speed and / or the actual speed of cooling roller 28.

[0172] Using the speed v of the cooling roller 28, the control device 51 establishes a control signal for the pressure regulating valve 65, which, for example, indicates the desired value of the input pressure p and / or the negative pressure in the intermediate space 48. It is also conceivable that the control signal indicates the desired opening width of the pressure regulating valve 65.

[0173] 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.

[0174] The actual value of the input pressure p can be determined, for example, by means of the pressure sensor 56, and can also be used as an input to the control device 51.

[0175] For example, the dependence of the desired value of the input pressure p on the speed v of the cooling roller 28 is stored in the control device 51. This dependence can appear as a lookup table and / or function.

[0176] An example of this lookup table is shown below:

[0177] Figure 10 A graph including two exemplary curves is shown, illustrating the dependence of the desired value of the input pressure p on the speed v of the cooling roller 28. The discontinuous line indicates a linear dependence, while the dotted line represents a non-linear dependence, here in the form of an S-curve.

[0178] It is also conceivable that the desired value of the input pressure p depends on more than one input quantity. The individual or combined input quantities that can be conceivable are as follows: the speed v of the cooling roller 28, the production rate of the film F of the casting unit 14 and / or the unit 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.

[0179] It is conceivable that the pressure regulating valve 65 is a manual valve and / or manually actuated. Therefore, the input pressure, the positive pressure level in the inlet chamber 62, and the pressure of the airflow 46 can also be manually adjusted, with the pressure of the airflow 46 in turn affecting the negative pressure level in the intermediate space 48. By manually adjusting the input pressure, control equipment can also be eliminated.

Claims

1. A casting unit (10) for producing a film (F), comprising a slit die (26), a cooling roller (28), and an air nozzle device (32). in, The cooling roller (28) includes a circumferential surface (36) and is designed to rotate about an axis, such that the circumferential surface (36) moves in the direction of rotation (R). The slit mold (26) is designed to generate a melt (38) that contacts the circumferential surface (36) at the application line (A). The air nozzle device (32) is connected to the slit mold (26) such that the intermediate space (48) is defined by the circumferential surface (36) of the cooling roller (28), the melt (38), the slit mold (26) and the air nozzle device (32), wherein the air nozzle device (32) is designed to generate an airflow (46) that impacts the circumferential surface (36) along the line of action (W) against the direction of rotation (R) and generates a negative pressure in the intermediate space (48).

2. The casting unit according to claim 1, characterized in that, The slit mold (26) includes an outlet opening (40) that opens toward the circumferential surface (36) in the direction of rotation (R) and / or in the radial direction.

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

4. The casting unit according to any one of the preceding claims, characterized in that, The outlet opening (40), the melt (38), the intermediate space (48) and / or the airflow (46) are continuous in the axial direction.

5. The casting unit according to any one of the preceding claims, characterized in that, The air nozzle device (32) includes a flow guide section (66) that defines a gap (74) between the cooling roller (28) and the air nozzle device (32), through which an airflow (46) flows, particularly where the gap (74) is between 0 mm and 6 mm, particularly between 1.5 mm and 3.5 mm.

6. The casting unit according to any one of the preceding claims, characterized in that, The airflow (46) at the line of action (W) and / or in the gap (74) has a velocity between 50 m / s and 250 m / s, particularly between 50 m / s and 200 m / s, and / or the negative pressure in the intermediate space (48) is between 5 Pa and 25,000 Pa, for example between 5 Pa and 600 Pa, particularly between 30 Pa and 150 Pa, or between 500 Pa and 25,000 Pa, particularly between 500 Pa and 20,000 Pa.

7. The casting unit according to any one of the preceding claims, characterized in that, The application line (A) is offset in the rotation direction (R), and / or the action line (W) is offset from the zero line (N) in the opposite direction of the rotation direction (R), wherein the zero line (N) corresponds to a straight line extending radially through the apex of the cooling roller (28) in the correct assembly position.

8. The casting unit according to any one of the preceding claims, characterized in that, The airflow (46) contacts the circumferential surface (36) at an incident angle (α), wherein the incident angle (α) is between 0° and 80°, particularly between 5° and 40°.

9. The casting unit according to any one of the preceding claims, characterized in that, The air nozzle device (32) is attached to the slit mold (26), particularly on the side of the slit mold (26) facing the cooling roller (28), and / or the air nozzle device (32) is designed to be movable relative to the slit mold (26).

10. The casting unit according to any one of the preceding claims, characterized in that, The air nozzle device (32) has a nozzle section (42) including a nozzle opening (44) that opens toward the line of action (W), the gap (74) and / or the flow guide portion (66). In particular, the air nozzle device (32) includes at least one compressed air source (64) that is designed to deliver air to the nozzle opening (44) to generate the airflow (46).

11. The casting unit according to claim 10, characterized in that, The air nozzle device (32) includes a reservoir (58) from which the nozzle opening (44) extends.

12. The casting unit according to claim 11, characterized in that, The air nozzle device (32), particularly the nozzle section (42), includes an inlet chamber (62) and a plurality of pipes (60), wherein the pipes (60) fluidly connect the inlet chamber (62) to the reservoir (58), and wherein at least one compressed air source (64) is disposed on the end face of the inlet chamber (62).

13. The casting unit according to any one of the preceding claims, characterized in that, The casting unit (14) includes a control device (51), and the air nozzle device (32) includes 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 configured to control the pressure regulating valve (65). In particular, the control device (51) is configured to receive the speed (v) of the cooling roller (28) as an input and output a control signal for the pressure regulating valve (65) based at least on the speed (v) of the cooling roller (28).

14. The casting unit according to any one of the preceding claims, characterized in that, The air nozzle device (32) includes two end face covers (50), each of which is disposed on one of the end faces of the intermediate space (48) and closes the intermediate space (48) in the axial direction. In particular, at least one of the covers (50) includes a pressure sensor (56) and / or a measuring opening (52) which is fluidly connected to the pressure sensor (56).

15. A unit for producing a film (F) comprising a casting unit (14) and a stretching unit (16, 18) according to any one of the preceding claims, particularly a transverse orientation oriented device, a machine orientation oriented device and / or a simultaneous stretching unit.

16. A method for producing a film (F) by means of a unit (10) according to claim 15, wherein a melt (38) is generated by means of a slit mold (26) and applied to a cooling roller (28), wherein a negative pressure is simultaneously generated in the intermediate space (48), particularly wherein, The negative pressure level in the intermediate space (48) is controlled by the control device (51) of the casting unit (14), and more particularly based on the speed (v) of the cooling roller (28).

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